JPH11299290A - Ac motor drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a very reliable system, which prevents the deterioration of a smoothing capacitor, a PWM inverter, and an AC motor, which are key components of the converter/inverter system and can expand the life of a drive system, such as an elevator which has a long service life and increase the reliability and which can efficiently process regenerative energy, even in the case when a power supply has a troubles or a converter goes out of order. SOLUTION: A converter/inverter control system is added with a converter/ inverter manipulated variable storing means 30 for storing manipulated variables for controlling a converter, a PWM inverter, and a motor, a DC voltage command calculating means 40 for generating a DC voltage command, based on the manipulated variables stored in the storing means 30, a power supply trouble deciding means 60, a converter input power minimum value deciding means for deciding the minimum value of the converter input power, and an energy accumulating means 7 connected in parallel with a smoothing capacitor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a converter / PW
The present invention relates to a system for driving an AC motor at a variable speed by an M inverter, and particularly to a variable speed drive for an elevator, an electric railway, and general industrial fields in which the AC motor is repeatedly accelerated and decelerated using an AC power supply, that is, a commercial power supply as a power source. The present invention relates to a converter / PWM inverter system suitable for a system.

[0002]

2. Description of the Related Art In a conventional converter control, as disclosed in Japanese Patent Application Laid-Open No. 4-285472, a DC voltage of a capacitor for smoothing an output voltage of a converter (hereinafter referred to as a smoothing capacitor) is controlled to a predetermined value. And a voltage control system that matches the DC voltage of the smoothing capacitor to the DC voltage command is added to control the power factor 1 so that the phase of the power supply current on the input side matches the phase of the power supply voltage. I was The DC voltage command was kept constant regardless of the state of the inverter.

As a method of controlling the converter based on the information on the inverter side, as disclosed in Japanese Patent Application Laid-Open No. 1-136568, the inverter input current is detected and the power supply current is controlled without directly controlling the DC voltage command. There is also a method of compensating for. Further, in Japanese Patent Application Laid-Open No. 3-1288691, the instantaneous electric power on the inverter side is calculated and fed back to the current control system on the converter side, so that the voltage of the smoothing capacitor is transiently kept constant.

[0004]

In the conventional converter control, the DC voltage of the smoothing capacitor is constantly and constantly fixed. When performing converter control, the DC voltage command of the smoothing capacitor is larger than the average voltage of the full-wave rectifier by the diode, and is limited by the withstand voltage of the used smoothing capacitor and the withstand voltage of the power element used for the inverter. For example, in the case of a 200 V three-phase power supply, the DC voltage command for converter control is 2
The voltage is set as high as possible between 80V and 400V. This is to increase the control range in which regeneration is possible. Therefore, in the conventional converter control, since the above high DC voltage is always applied to the smoothing capacitor, the life of the capacitor and the power element of the inverter is accelerated as the applied voltage is higher, the deterioration is accelerated and the life is increased. Be shorter. For this reason, there is a problem that the number of times of maintenance, inspection and replacement is increased in an elevator or an AC overhead line electric railway having a long product life of 15 to 20 years in order to ensure reliability.

[0005] Regardless of the speed of the motor, a PWM pulse having a voltage value corresponding to the DC voltage command is output from the PWM inverter. This PWM pulse voltage is not only large in magnitude but also a PWM pulse with a sharp rise and fall, so that a surge voltage with a very short wave front length is generated. When this surge voltage is applied to the motor via the wiring cable, an overvoltage exceeding the output voltage of the PWM inverter occurs at the motor terminal due to a reflection phenomenon at the motor terminal, which causes insulation breakdown of the winding of the motor. . In the conventional converter control, as described above, if the DC voltage command is maintained at a high value, the influence of the surge voltage becomes excessively large, and the insulation deterioration of the motor is accelerated.

Further, when an AC motor is driven at a variable speed,
Since the effective voltage value applied to the motor is small in the low-speed range, the pulse width of the PWM signal applied to the gate of the power element is narrow. Since the power element used in the inverter has a switching delay, it is necessary to apply a dead time to the gate of the power element with a dead time to prevent a short circuit between the upper and lower arms of the inverter. The driving performance of the electric motor deteriorates. The influence of this dead time is that the DC voltage command is set higher than usual, so that the pulse width of the PWM signal further decreases, but the dead time does not change, so the dead time with respect to the period of the PWM signal is reduced. And the current flowing through the motor becomes more and more distorted.

Further, since the peak value of the voltage applied to each arm of the PWM inverter increases, the switching loss of the inverter also increases. Further, in a light load state in a low speed range, the exciting current increases, and the power factor of the motor decreases, so that high-efficiency driving cannot be performed.

In the conventional converter control described above, the life of the power element in the smoothing capacitor and the inverter, the deterioration of the insulation of the motor and the overall efficiency characteristics including the converter / inverter are improved, and the driving performance in the low-speed region is improved. The power factor control is not considered, and an object of the present invention is to provide an AC motor drive system by converter control that can solve such a problem.

[0009]

SUMMARY OF THE INVENTION The above-mentioned problem is caused by the fact that the DC voltage (voltage of the smoothing capacitor) applied to the inverter is:
This is achieved by optimizing according to the operation state of the inverter. For this purpose, the following control means is added so that the control information of the inverter is also taken in and the DC voltage applied to the inverter can be controlled in accordance with the state on the load side.

First, a converter / inverter operation amount storage means is provided, and the state quantity of the PWM inverter includes a speed command of an AC motor, a speed deviation of a speed control system (a deviation between the speed command and the speed of the motor), a torque command. , Deviation of torque control system (deviation between torque command and generated torque), manipulated variable of torque command, torque current command, modulation degree of modulation wave of PWM control system, voltage command for forming modulation wave, voltage command The internal q-axis voltage component and the like are stored. The DC voltage command is corrected based on these state quantities. A DC voltage corresponding to the DC voltage command is directly applied to the smoothing capacitor to perform power factor control for converter control.

In order to realize such control, DC voltage command calculation means for calculating a DC command of the converter based on the information of the converter / inverter operation amount storage means, torque command or torque determination means, PWM control By adding the system saturation determining means and the converter input power minimum value determining means to the converter / inverter control system, the following operation can be attained and the above problem can be solved.

In general, constant-speed control is performed in variable-speed driving of an AC motor. In this control, the voltage and frequency applied to the motor are controlled by a PWM inverter so that the ratio between the rated voltage and the rated frequency of the motor is constant in order to eliminate magnetic saturation inside the motor. On the other hand, the maximum output voltage of the PWM inverter is determined by the magnitude of the DC voltage. Therefore, in a region where the speed of the motor is low, the voltage applied to the motor may be small. This means that the DC voltage command may be obtained in correspondence with the motor speed command, which is one of the information stored in the converter / inverter operation amount storage means. However, this is not enough. This is because the state of the load applied to the motor is not taken into account in this calculation process. A large load may be applied even in a low speed range. In such a case, it is necessary to apply a voltage to the AC motor to generate a sufficient load torque and a torque required for acceleration. Generally, the load torque applied to the electric motor is added or fluctuated regardless of the speed of the electric motor. In order to cope with this, the DC voltage command is further determined in consideration of the state of each control system in which fluctuations such as load torque and acceleration torque of the speed control system, torque control system, PWM control system, etc. actually appear. What should I do?

Therefore, in the present invention, the DC voltage command is basically linked with the speed command, but the linking operation is performed while taking into account at least one information among the state quantities of the respective control systems. It is calculated by the DC voltage command calculation means so that a torque corresponding to the state can always be generated.

This is carried out in parallel with the addition of "a normal operation for increasing / decreasing the DC voltage command in response to the speed command" and a "correction process other than the normal operation".
For example, the former “normal processing” includes a method of executing “correction processing for increasing or decreasing the DC voltage command while monitoring the magnitude of the speed deviation signal of the speed control system (or saturation of the speed control system)”. If the speed deviation is excessive in the DC voltage command obtained in the “normal processing” in which the DC voltage command is increased or decreased according to the speed command, the latter “correction processing” operates. In this “correction process”, the DC voltage command is increased or decreased until an excessive speed deviation (or saturation of the speed control system) is avoided. And if saturation of the speed control system is avoided,
The correction of the DC voltage command obtained in the “correction processing” at that time is maintained, and thereafter, only the “normal processing” is executed. The DC voltage command in this case is a value obtained by superimposing the correction amount obtained in the “correction process” on the “normal process” of the DC voltage command corresponding to the speed command, and is determined by the inverter input voltage corresponding to the DC voltage command. The PWM inverter generates an AC voltage, and the motor is driven by this voltage.

By performing such a "correction process", the AC motor is driven without saturating the control system, so that the DC voltage applied to the inverter has a minimum value, and the above-mentioned problem is achieved. You.

In the above description, attention has been paid to the saturation of the speed control system as the "correction process". However, the torque command and the torque deviation (the torque command and the torque deviation) are set so that the control systems such as the torque control system and the PWM control system are not saturated. "Correction processing" while determining the saturation of the control system from state quantities such as a deviation from the generated torque), a PWM inverter voltage command (modulated wave), and a q-axis voltage component.
The above-mentioned problem can be similarly achieved by executing the above.

In addition, the same effect can be obtained by correcting the DC current command so as to minimize the input power of the converter as the "correction process". That is, the DC voltage command that minimizes the input power is equivalent to the fact that the control system of the inverter operates without being saturated.
If saturation occurs in the control system, proper voltage and current cannot flow to the motor.

[0018]

FIG. 1 shows an embodiment in which the present invention is applied to a variable speed drive system of an elevator. First, the power / mechanical system of the drive system will be described. The three-phase commercial power supply 1
Via a current sensor 2 for detecting a power supply current and an AC reactor 3, a converter (forward converter) 4 for converting an AC voltage into a DC voltage is connected. Converter 4 is a rectifier that can vary the output voltage that can be controlled to a value equal to or greater than the value of the DC voltage obtained by full-wave rectification by a diode. The DC voltage obtained from converter 4 is smoothed by smoothing capacitor 5. Therefore, in the converter method, a voltage higher than the voltage obtained by full-wave rectification by the diode is always applied to the smoothing capacitor.

On the other hand, the deterioration characteristic of an electrolytic capacitor generally used as a smoothing capacitor is a function of the square of the applied voltage. For this reason, when the converter method is adopted, the smoothing capacitor is more deteriorated than the full-wave rectification method using the diode. A method of avoiding this is a DC voltage command process described later.

In parallel with the smoothing capacitor 5, a power storage means in which a power switching element 6 and a large-capacity power capacitor 7 are connected in series is connected. The large-capacity power capacitor 7 cannot be stored by the smoothing capacitor 5 alone,
It serves to accumulate regenerative energy generated by the motor when decelerating an elevator, which will be described later. In addition, a large-capacity capacitor capable of storing energy is used when the converter 4 is out of order or when the commercial power supply 1 fails to recover excess regenerative energy due to a power outage, and has a capacity of, for example, several tens of F. , An electric double layer capacitor is used.

[0021] PW via the above-mentioned emergency power storage means
M inverter 8 is connected. The emergency power storage means is connected to an auxiliary power supply 130 such as a controller or a display, and surplus energy that cannot be regenerated to the power stored in the large-capacity power capacitor 7 is used for the auxiliary power supply. Here, the case where the power supply is used as an auxiliary power supply has been described, but the power supply can be used as a power supply for various uses used in a drive system such as a drive power supply for a fan used for cooling a converter, an inverter, and the like.

The PWM inverter 8 is connected to an AC motor 10 via a current sensor 9, and the current sensor 9 detects a current flowing in a primary winding of the AC motor 10. A rotary encoder 11 is provided at one end of the rotating shaft of the AC motor 10.
A is attached, and the rotation speed of the AC motor 10 is detected. Further, a driving force transmission mechanism (not shown) such as a gear is connected to the other end of the rotating shaft of the AC motor 10, and is connected by a rope via a mesh wheel 11 driven by the driving force transmission mechanism.
A counterweight 12 and a car 13 are suspended, and the rotational force (torque) of the electric motor is converted into a vertical motion, and the car 13
Move up and down.

Hereinafter, the configuration and operation of the control system of the above-described elevator drive system will be described.

The control system of the elevator drive system includes a voltage sensor 20 for measuring the voltage of the current guided from the commercial power supply 1 to the converter 4, a power supply abnormality determining means 60 to which the output of the voltage sensor 20 is input, and a power supply phase detecting means 70. A DC voltage command calculating means 40 connected to the output side of the power supply abnormality determining means 60, a voltage sensor 5A for detecting a terminal voltage of the smoothing capacitor 5, and a regenerative energy processing control start determination to which an output Ed of the voltage sensor 5A is input. Means 110, converter / inverter operation amount storage means 30, voltage sensor 5
A voltage control means 50 having the output Ed of A and the output Ed * of the DC voltage command calculation means 40 as inputs, a power supply current command generation means 80 having as inputs the output of the voltage control means 50 and the output of the power supply phase detection means 70, A current control unit 90 that receives the output of the current command generation unit 80 and the output of the current sensor 2 as inputs,
PWM signal generating means 100 which receives the output of the current control means 90 and the output of the power supply abnormality judging means 60 and outputs a PWM signal to the converter 4, the output ΔEd of the voltage control means 50 and the regenerative energy processing control start judging means 110
Chopper duty ratio calculating means 120 and acceleration command calculating means 1 for inputting the output of the above and the terminal voltage of the large capacity power capacitor 7 and inputting the output to the power switching element 6
40, a speed command calculating means 150 to which the output α * of the acceleration command calculating means 140 is inputted, and an output ω * of the speed command calculating means 150 and the rotational angular velocity ωm calculated based on the output of the rotary encoder 11A. The adder / subtractor 170, the speed control means 160 to which the output Δω of the adder / subtractor 170 is input, the torque / excitation current detection means 180 to which the output of the current sensor 9 is input, and the output Im of the torque / excitation current detection means 180 to input. Secondary magnetic flux calculating means 1
90, an output Φ ₂ of the secondary magnetic flux calculating means 190 and an output It of the torque / exciting current detecting means 180 are input. The torque calculating means 200 receives the output τ of the torque calculating means 200 and the output τR of the speed control means 160. Adder / subtractor 17
1, a torque control means 210 which receives an output of the adder / subtractor 171 as an input, a vector control means 220 which receives an output τ * of the torque control means 210, an output Φ ₂ of the secondary magnetic flux calculating means 190, and the rotational angular velocity ωm, Vector control means 22
The adder / subtractor 172 which receives the output Im * of 0 and the output Im of the torque / excitation current detection means 180 as inputs, the output It * of the vector control means 220 and the torque / excitation current detection means 180
Adder / subtractor 173 and adder / subtractor 17 that receive the output It
The current control means 23 which receives the output ΔIt of the second control signal, the output ΔIm of the adder / subtractor 173 and the output ω of the vector control means 220 as inputs.
0, a PWM signal generating means 240 which receives the outputs Vt *, Vm * of the current control means 230 and inputs the output to the PWM inverter 8.

The output α of the acceleration command calculating means 140 is stored in the converter / inverter operation amount storing means 30.
*, Output ω * of speed command calculation means 150, adder / subtractor 17
The output Δω of 0 and the output of the power supply abnormality determination means 60 (power supply abnormality detection signal) are input, and the output side of the converter / inverter operation amount storage means 30 is connected to the DC voltage command calculation means 4.
Connected to 0. The primary angular frequency ω output from the vector control means 220 is input to the input side of the torque / excitation current detection means 180, and the instantaneous phase θ output by the torque / excitation current detection means 180 is a PWM signal generation means. 240 is input. The output (power failure detection signal) of the power failure determination means 60 is also input to the regenerative energy processing control activation determination means 110.

First, the configuration and operation principle of the control system of the converter will be described. The control system (converter control means) of the converter includes the voltage sensor 5A, the DC voltage command calculation means 40, the voltage control means 50, the power supply abnormality determination means 60, the power supply phase detection means 70, the power supply current command generation means 80 , Current control means (input current control means) 90, and P
It is composed of WM signal generating means 100.

The output voltage of converter 4 is controlled based on DC voltage command Ed * generated by DC voltage command calculation means 40. The DC voltage command Ed * and the terminal voltage Ed of the smoothing capacitor 5 detected by the voltage sensor 5A are input to the voltage control means 50, and the voltage control means 5
0 operates so that the detected terminal voltage Ed of the smoothing capacitor 5 matches the DC voltage command Ed *, and determines and outputs the value of the amplitude Is * of the power supply current. The phase of the power supply current command is obtained by detecting the commercial power supply voltage by the voltage sensor 20 and based on this detection signal, the voltage phase θs of the commercial power supply 1 is obtained by the power supply phase detecting means 70. Power supply phase detecting means 7
0, U-phase, V-phase, W-phase
The zero phase of the three-phase power supply voltage of each phase is obtained, and the counter is operated based on the zero phase to generate a phase of 360 ° (for one cycle).

The amplitude Is * of the power supply current and the voltage phase θs of the commercial power supply 1 are input to the power supply current command generation means 80, and the power supply current command generation means 80 generates the power supply current command is * (AC amount) for three phases. I do. Power supply current command for three phases is *
Is input to the current control means 90 and the current control means 90
Takes a deviation from the three-phase power supply current detected by the current sensor 2, and the current control means 90 operates so that the deviation becomes zero, thereby generating an AC voltage command Es *. The AC voltage command Es * (for three phases, only one phase is shown in the figure)
Is input to the PWM signal generating means 100 as a modulated wave for PWM control. The modulated wave (for three phases) is PW
Compared with the carrier (triangular wave) of the M signal generating means 100,
A PWM signal is generated and applied to the gate of the power switching element constituting the converter 4.

Therefore, converter 4 outputs a DC voltage corresponding to the DC voltage command while making the power supply current coincide with the phase of the power supply voltage. The PWM inverter 8 generates a variable-voltage / variable-frequency AC power supply based on the DC voltage by the control described below, and drives the AC motor 10.

The PWM inverter control system (PWM inverter control means) includes a rotary encoder (speed detection means) 11A, acceleration command calculation means 140, speed command calculation means 150, adder / subtractor 170, speed control means 160, torque / excitation current detection. Means 180, secondary magnetic flux calculating means 19
0, torque calculating means 200, adder / subtractor 171, torque control means 210, vector control means 220, adder / subtractor 17
2, adder / subtractor 173, current control means 230, and PWM
It is configured to include the signal generation means 240. The PWM inverter control system operates as follows.

The acceleration command calculating means 140 generates an acceleration signal α * in consideration of the riding comfort of the person in the car 13 and inputs the acceleration signal α * to the speed command calculating means 150. The speed command calculating means 150 integrates the input acceleration signal α * to obtain a speed command ω *, which acts as a command signal for a speed control system. The speed command ω * is connected to the plus terminal of the adder / subtractor 170, the rotational angular speed ωm (speed calculator is omitted) obtained by calculating based on the signal obtained from the rotary encoder (speed sensor) 11A to the minus terminal, Each of them is input, and the adder / subtractor 170 generates a speed deviation Δω. The speed deviation Δω is determined by the speed control means 160
And the speed control means 160 generates a torque command τR such that the speed deviation Δω becomes zero. The torque command τR is input to the plus terminal of the adder / subtractor 171, and the instantaneous torque τ obtained from the torque calculator 200 is input to the minus terminal. Instantaneous torque τ (= k ・ It ・
φ ₂ ) is the torque current It, 2 obtained by the torque / excitation current detecting means 180 and the secondary magnetic flux calculating means 190.
The next magnetic flux φ ₂ is input and output from the torque calculating means 200.

Here, torque / excitation current detecting means 180
Converts the three-phase primary current (current flowing through the primary winding of the AC motor 10) detected by the current sensor 9 into a primary angular frequency ω obtained from a vector control unit 220 described later.
Using the instantaneous phase θ (= 角 ωdt) obtained by integrating (= ωm + ωs: slip angular frequency), a three-phase AC current is converted into a two-phase DC current to obtain a torque current It and an excitation current Im. . The secondary magnetic flux φ ₂ depends on the exciting current Im and the AC motor 10
Magnetic flux calculating means 190 using the secondary time constant T _{2 of}
In the above, the calculation is performed by executing an operation: M · Im / (1 + T ₂ · s, s: Laplace operator, M: excitation inductance).

An adder / subtracter 171 calculates a deviation Δτ (= τR−τ) between the torque command τR and the instantaneous torque τ generated from the AC motor 10, and the torque control means 210
Is input to The torque control means 210 generates a torque command operation amount τ * such that the torque deviation Δτ is eliminated. The manipulated variable τ * of the torque command is input to the vector control means 220, and the vector control means 220 determines the torque current command It * and the excitation current command Im * as follows. The torque current command It * is obtained by executing a calculation: kt · τ * / φ ₂ (kt: a constant related to the motor) based on the secondary magnetic flux φ ₂ currently generated in the electric motor.

On the other hand, the excitation current command Im * is set to a control amount α, for example, a control amount obtained by using the method disclosed in Japanese Patent Application No. 8-40916 so that the operation efficiency of the drive system is maximized. α is the torque current command I obtained by the above calculation.
Multiply by t *.

The excitation current command Im * and the torque current command It * thus obtained are respectively added to the adder / subtracter 172, 1
The excitation current Im and the torque current It that are input to the plus terminal 73 and detected by the torque / excitation current detection means 180 are input to the minus terminal. Adder / subtractor 172, 1
73 outputs a torque current deviation ΔIt and an excitation current deviation ΔIm, respectively, and the torque current deviation ΔIt and the excitation current deviation ΔIm are input to the current control means 230. The current control unit 230 generates voltage commands Vt * and Vm * based on the torque current deviation ΔIt, the excitation current deviation ΔIm, and the primary angular frequency ω input from the vector control unit 220, and outputs the PWM signal generation unit 240 Output to

The voltage commands Vt * and Vm * are converted by the PWM signal generating means 240 into the magnitude of the primary voltage command V1 * ｛=
((Vt *) ² + (Vm *) ² ) １ ／, the primary AC voltage command (for three phases) vu, vv, from the instantaneous phase θ output from the torque / excitation current detecting means 180 vw is generated and compared with a triangular wave (carrier) to generate a PWM signal, which is applied to the gate of the power switching element of the PWM inverter 8.

The converter / inverter operation amount storage means 30 stores the state quantities of the converter control system and the PWM inverter control system described above. The converter / inverter operation amount storage means 30 stores an acceleration command, a speed command, a speed deviation,
Torque command τR, torque deviation Δτ, manipulated variable τ * of torque command, torque current command It *, deviation ΔIt of torque current, voltage command Vt * contributing to torque, magnitude V1 * of primary voltage command, modulation degree (= The magnitude of the primary voltage command and the peak value of the carrier wave) are stored (in FIG. 1, some connection lines are omitted in order to avoid complication of the drawing).

On the other hand, from the converter control system, an abnormal signal (power abnormality detection signal) on the power supply side, for example, a signal for detecting a power failure, an instantaneous power failure, or an open phase, or an AC voltage command (not shown in FIG. 1). , The degree of modulation, the magnitude of the voltage component that affects the magnitude of the input voltage of the converter, the input deviation of the voltage control means, the amplitude of the power supply current output from the voltage control means 50, and the amplitude of the PWM signal generation means 100. The time or the like of the minimum pulse width of the PWM signal is also a state quantity to be stored in the converter / inverter manipulated variable storage means 30.

The temperatures of the power converters of the converter and the inverter and the temperatures of the individual power switching elements constituting the power converters are also the state variables stored in the converter / inverter operation amount storage means 30. The DC voltage command for the converter is determined based on these state quantities.

FIG. 1 shows an example in which the DC voltage command Ed * is determined based on the speed command ω * and the speed deviation Δω. The feature of this configuration is that the capacity of the smoothing capacitor 5 is several thousand μ.
In contrast to F, a capacitor of several F to several tens F or more is provided as the capacity of the large-capacity capacitor 7.
Therefore, since the surplus energy during regeneration can be completely stored in the large-capacity capacitor 7 by the following means, the smoothing capacitor voltage can be kept within a predetermined range regardless of the operation state of the drive system. The stored energy can also be used as an auxiliary power source for a control power source or the like, or as an emergency power source at the time of power failure.

The above control is started by the regenerative energy processing control start judging means 110 when the smoothing capacitor 5 reaches a predetermined voltage. The regenerative energy processing control start determination means 110 generates a start signal when the smoothing capacitor 5 reaches a predetermined voltage, and inputs the start signal to the chopper conduction ratio calculation means 120. This chopper conduction ratio calculating means 12
To 0, the start signal, the deviation ΔEd between the DC voltage command Ed * and the DC voltage Ed of the smoothing capacitor, and the terminal voltage of the large-capacity capacitor 7 are input, and according to the magnitude of the deviation ΔEd (the sign is minus). The operation is performed until the voltage of the smoothing capacitor 5 falls within a specified voltage range (within the range specified by the DC voltage command Ed *).

FIG. 2 shows the speed command and the DC voltage command corresponding thereto. The speed command has been described by taking an elevator as an example. However, in the case of acceleration / deceleration driving, similar speed commands are given, so that generality is maintained. When a start command is given to the elevator, A
The acceleration command α * that can maintain a comfortable ride comfort is given, and the elevator accelerates. In this region, the motor must generate the total torque of the acceleration torque and the load torque (the driving force required to transport the load having the difference between the counterweight and the load of the car (including the running resistance)). In order to generate such a torque, the ratio between the inverter output voltage and the frequency may be controlled to be constant.

Accordingly, since the speed command changes in accordance with the inverter frequency, in a region where the speed command is small,
The voltage output from the inverter (the inverter voltage required for driving the motor) may be small. On the other hand, the output voltage of the inverter is proportional to the inverter input voltage (DC voltage). Therefore, when the speed command is small, the inverter input voltage may be basically small. Therefore, basically, the DC voltage command of the converter control system is changed in accordance with the increase / decrease of the speed command of the inverter control system. Here, ΔEd is the amount to be corrected, and Ed0 * is the output voltage (average voltage) of the full-wave rectifier of the diode, which is a fixed component.

Ed * = Ed0 * + ΔEd (1) ΔEd = k · ω * (K: constant) (2) However, among the above torques, the load torque varies depending on the number of occupants. There is no causal relationship.
There are two ways to deal with this. One of them is
In order that the converter can generate the input voltage of the inverter by ΔEdmax so that the inverter can generate a voltage sufficient to generate the required maximum torque at each speed of the motor,
This is a method in which the bias ΔEdmax is set in advance as shown in FIG.

ΔEd * = k · ω * + ΔEdmax (3) In this method, the inverter input voltage is high in a light load region. For this reason, the second method is to make it possible to further optimize the correction according to the load state. The amount of this correction is the speed deviation Δω of the speed control system, the torque command τR, the torque deviation Δτ of the torque control system, and the operation amount τ of the torque command.
*, Torque current command It *, manipulated variable V of torque current control system
The amount of correction is determined based on the amount of information fluctuating according to the state of the load at t * and the magnitude V1 * of the modulated wave (primary voltage command) of the PWM control system.

As shown in FIG. 2 (b), the DC current command uses the smoothing capacitor voltage obtained when the converter section is a rectifier composed of a diode as a lower limit value, The smaller of the allowable values of the input DC voltage of the PWM inverter is set as the upper limit value, and the change is determined so as to be the same as the change of the speed command within this range. The maximum value of the DC voltage shown in FIG. 2B is the smaller of the allowable voltage of the smoothing capacitor and the allowable value of the input DC voltage of the PWM inverter.

FIG. 3 shows a DC current command process for varying the correction ΔEdmax based on the speed deviation Δω of the speed control system. The power supply abnormality determination means 60 detects the three-phase voltage, determines whether or not there is an abnormality based on the magnitude of the detection signal, and generates a power supply abnormality detection signal when the magnitude decreases below a predetermined value. In this case, since the energy of the electric motor cannot be regenerated on the power supply side, the converter operation is stopped and the following power supply abnormality processing 600 is executed. That is, the DC voltage command is reduced in response to the speed command, and a deceleration process for stopping the elevator at the nearest floor is executed.
When the converter operation is stopped, the terminal voltage of the smoothing capacitor 5 is reduced to a predetermined value. When the terminal voltage of the smoothing capacitor 5 reaches a predetermined value, a DC current is supplied to the AC motor through the PWM inverter to supply AC power. The speed of the motor is reduced to a predetermined speed.

In this case, regenerative energy is generated by the deceleration, and the energy is accumulated in the smoothing capacitor 5. Therefore, a determination process 60C for determining whether or not the voltage of the smoothing capacitor 5 has reached a predetermined value or more is executed.
If this value is equal to or less than the specified value, regenerative energy is accumulated in the smoothing capacitor while decelerating the elevator. When the voltage of the smoothing capacitor 5 reaches a specified value or more, the regenerative energy is accumulated in the large-capacity capacitor 7 until the chopper element (power switching element) 6 is operated and the elevator stops. Here, when the regenerative energy is accumulated in the large-capacity capacitor 7 and reaches a voltage equal to or higher than a predetermined voltage, for example, 5 V or more, it is supplied as a power supply for a control circuit. This energy may be used as an emergency power supply for other devices, such as a cooling fan drive power supply for the converter / inverter.

If no power failure signal is generated in step 60, first, in step 10A, the controllable correction of the DC voltage command is changed in accordance with equation (2) in accordance with the speed command.

Next, when the speed deviation Δω of the speed control system is accelerating (α * ≧ 0), it exceeds the maximum value Δωmax, or when decelerating (α * ≦ 0), the minimum value is obtained. -Δωm
Check if it is not less than ax. If none of the above applies, the speed control system is operating normally without saturation. In this case, it is determined that the inverter input voltage for generating the torque is appropriately given, and the processing 100C for setting the correction ΔAdmax corresponding to the load torque to the current value is executed.

If the speed deviation Δω exceeds Δωmax, it is determined that the torque to be generated by the motor is insufficient, and a process 100B for increasing the correction ΔEdmax by a predetermined time constant is executed. When this operation is repeated, the input voltage finally becomes a proper one, and the process 100C
Will be executed. The speed deviation Δω is -Δωmax
In the following cases, the control system is saturated due to overspeed, and the input voltage decreases from the current value.
Execute D. When this operation is repeated, the input voltage finally becomes the same, and the process 100C is executed. By such an operation, even if the load changes due to a change in the number of occupants or the like, the saturation of the speed control system is suppressed, so that the electric motor can generate a torque that achieves a desired speed.

In addition, since the DC voltage command is reduced by the process 100D, the rotational energy of the motor is regenerated.
The voltage of the smoothing capacitor may increase. Therefore, first, it is determined whether or not the voltage of the smoothing capacitor 5 is within a specified range. If the voltage is within the specified range, the compensation for the load torque is directly performed. However, processing 100E
Then, when the voltage of the smoothing capacitor 5 has reached the specified level or more, the power switching element 6 is operated to execute a process 100F for storing regenerative energy in the large-capacity capacitor 7. The stored power is used as drive power for other devices such as a control power supply.

As described above, the DC voltage command is controlled so that the speed control system is not saturated, and the voltage applied to the smoothing capacitor 5 is optimized.

FIGS. 4 and 5 show an input voltage minimum value judging means 30A for judging the differential sign of the converter input and a torque command or torque judging means 30B added to the configuration shown in FIG. 9 shows another method of optimization. The other configuration is the same as the configuration shown in FIG. 1, so that illustration and description are omitted. As shown in FIG. 5, the presence / absence of a power supply abnormality detection signal obtained from the power supply abnormality determination means 60 is confirmed, and if yes, the power supply abnormality processing 60 shown in FIG.
Execute 0. If the power failure detection signal has not been generated, the above-described process 10A is executed.

Then, the following correction processing of the DC voltage command is executed so that the torque control system is not saturated. Here, in the process 200A, it is determined whether the torque command or the torque exceeds a specified value by the torque command or the torque determination means 3.
It is determined by 0B. As a result, when these values exceed the specified values, it is determined that the value of the DC voltage is an inappropriate value, and the following process 200B is executed. If the polarity of the torque command is positive, it means that the torque is insufficient, so the DC voltage command is increased. When the polarity of the torque command is negative, the brake torque is excessive, and there is a possibility that the regenerative energy increases and the smoothing capacitor voltage becomes excessive. Therefore, the DC voltage command is lowered to make it easier to regenerate surplus energy. By this processing, when the DC voltage command reaches the maximum value, it is determined that the regenerative processing cannot be performed in time, and the overvoltage processing 700 shown in FIG. 3 is executed.

If the torque command or the torque is within the specified range, the input voltage P
Processing 20 for searching for a DC current command that minimizes in
Execute 0D and 200E. In this process, the DC power command is increased / decreased within a specified range, and the input power input to the converter 4 is sequentially calculated from the input voltage and input current detected corresponding to each increase / decrease operation. It outputs a smaller DC voltage command value of the input power as a true DC voltage command.

By the above processing, an optimum DC voltage command can be obtained while minimizing the input power. As a result, the minimum voltage for improving the efficiency is applied, and the deterioration of the smoothing capacitor 5 is suppressed.

Next, another embodiment is shown in FIGS. The embodiment shown in FIG.
The difference from the configuration shown in FIG. 4 is that a PWM control system saturation determination means 30C is added in place of B, and other configurations are the same as those shown in FIG. . The PWM control system saturation determination means 30C
Output of M signal generating means 240 (torque voltage command Vt
*, The magnitude of the primary voltage command V1 *), and determines whether or not they exceed a specified maximum value, and outputs the determination result to the converter / inverter operation amount storage means 30.

In this embodiment, as shown in FIG. 7, after the processes 60A and 10A shown in FIG. 3 are executed, the torque control voltage command Vt * or 1
It is determined whether or not the next voltage command V1 * exceeds a specified maximum value, and it is checked whether the PWM control system is saturated. If the value exceeds the maximum value, the DC voltage command is increased or decreased with a predetermined time constant. That is, when the torque component voltage command exceeds the maximum value, the DC voltage is insufficient, and the DC voltage command is increased with a predetermined time constant. Conversely, if the torque component voltage command is equal to or less than the minimum value, the DC voltage of the smoothing capacitor is overvoltage due to the regenerated energy, so the DC voltage command is lowered to facilitate regeneration.

If the DC voltage command reaches the specified maximum value by this processing, the overvoltage processing shown in FIG.
00 is executed.

In the process 300A, when the torque component voltage command is within the maximum value and the minimum value, a process 300D for determining the DC voltage command so that the converter input power becomes the minimum value is executed. By this processing, the voltage of the smoothing capacitor can be efficiently and optimally controlled without saturation of the PWM control system, and deterioration of the capacitor can be suppressed.

In the embodiment shown in FIG. 1, the method of processing regenerative energy by a chopper circuit using a large-capacity capacitor in the case of converter control as a method of overvoltage processing can be applied to a full-wave rectifier using a diode.

As described above, according to the present invention, the deterioration of the smoothing capacitor can be suppressed efficiently.

[0064]

According to the present invention, even when the converter is controlled, the time during which a high voltage is applied to the smoothing capacitor is shorter than in the prior art, the deterioration of the smoothing capacitor can be suppressed, and the life can be extended. . Further, since the peak value of the voltage applied to the inverter can be suppressed to a low value, switching loss can be reduced, and at the same time, the voltage applied to the power switching element used in the inverter can be suppressed, so that deterioration of the power switching element can be suppressed. .

The peak value of the voltage waveform output from the PWM inverter is determined by the DC voltage of the smoothing capacitor. According to the present invention, since the value of the DC voltage can be suppressed low, the output voltage of the PWM inverter applied between the windings of the electric motor is also reduced, and the surge voltage due to the reflection phenomenon generated by the steep PWM waveform is also smaller than before. Therefore, the deterioration of the insulation of the motor can be suppressed.

As described above, the deterioration of the smoothing capacitor, the power switching element of the inverter, and the motor, which are key components of the drive system, can be suppressed, the service life of the drive system can be increased, and the reliability of the system can be improved.

Furthermore, since the DC voltage of the smoothing capacitor is determined so that the input power of the converter is minimized, the operation efficiency of the converter / inverter can be improved.

Further, by providing a large-capacity energy storage means in parallel with the smoothing capacitor, even if a situation occurs in which regenerative energy cannot be regenerated due to a power failure such as a power failure or a converter failure, the voltage of the smoothing capacitor can be reduced. Can not be abnormally high. Further, by providing this energy storage means, there is another effect that the energy obtained by storage can be used for an emergency power supply such as a controller or a display.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing a main configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a comparison between a DC voltage command according to the embodiment of the present invention and a DC voltage according to the related art.

FIG. 3 is a flowchart illustrating an example of a method of varying a DC voltage command according to the present invention.

FIG. 4 is a control block diagram showing an example in which a part of the embodiment shown in FIG. 1 is modified.

FIG. 5 is a procedure diagram showing an example of changing a DC voltage command according to the embodiment shown in FIG. 4;

FIG. 6 is a control block diagram showing another example in which a part of the embodiment shown in FIG. 1 is changed.

FIG. 7 is a procedure diagram showing an example of changing a DC voltage command according to the embodiment shown in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial power supply 2, 9 Current sensor 3 AC reactor 4 Converter 5 Smoothing capacitor 6 Power switching element 7 Large-capacity capacitor 8 PWM inverter 10 AC motor 11 Net wheel 11A Speed sensor (rotary encoder) 12 Counter weight 13 Riding car 20 Power supply voltage sensor Reference Signs List 30 converter / inverter operation amount storage means 30A converter input power minimum value determination means 30B torque command or torque determination means 30C PWM control system saturation determination means 40 DC voltage command calculation means 50 voltage control means 60 power supply abnormality determination means 70 power supply phase detection means Reference Signs List 80 power supply current command generation means 90 current control means 100 PWM signal generation means 110 regenerative energy processing control start determination means 120 chopper conduction rate calculation means 130 auxiliary for controller / display Power supply 140 Acceleration command calculation means 150 Speed command calculation means 160 Speed control means 170, 171, 172, 173 Adder / subtractor 180 Torque / excitation current detection means 190 Secondary magnetic flux calculation means 200 Torque calculation means 210 Torque control means 220 Vector control means 230 Current control means 240 PWM signal generation means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Komatsu 1070 Ma, Hitachinaka-shi, Ibaraki Pref. Hitachi, Ltd. Mito Plant

Claims (11)

[Claims] 1. A converter for converting a commercial power supply to a DC voltage, a capacitor for smoothing the output voltage of the converter, a PWM inverter for converting the DC voltage of the smoothing capacitor to an AC voltage having a variable voltage and a variable frequency, and a PWM inverter. In an AC motor drive system including an AC motor driven by variable speed driving, the control means for the converter, the PWM inverter control means for controlling the AC motor, and an operation amount and a state amount generated in a process of controlling both are stored. An AC motor drive system comprising a converter / inverter operation amount storage means, wherein the converter is controlled by an operation amount of the PWM inverter control means stored in the converter / inverter operation amount storage means. 2. The converter control means according to claim 1, wherein the DC voltage command calculating means for generating a DC voltage command for the smoothing capacitor, the DC voltage detecting means for detecting the voltage of the smoothing capacitor, and the DC voltage command calculating means. The input DC voltage command includes input current control means for controlling the input current of the converter so that the DC voltage detected by the DC voltage detection means is matched with the DC voltage command. Is a speed command calculating means for generating a speed command for the AC motor, a speed detecting means for detecting the speed of the AC motor, and generating a torque command for the AC motor so as to match the detected speed with the speed command. The control system of the converter / PWM inverter is configured to include the speed control means, and the DC voltage command calculation means of the converter control means is 2. The AC motor drive system according to claim 1, wherein the DC voltage command is determined in association with the speed command obtained from the speed command means of the PWM inverter control means. 3. The converter control means according to claim 1, wherein the DC voltage command calculation means generates a DC voltage command for the smoothing capacitor, the DC voltage detection means detects the voltage of the smoothing capacitor, and the DC voltage command calculation means issues the DC voltage command calculation means. 2. The PWM inverter control unit according to claim 1, further comprising an input current control unit that controls an input current of the converter so that the DC voltage command matches a DC voltage detected by the DC voltage detection unit. Acceleration command calculation means for generating an acceleration command of the above, speed command calculation means for forming a speed command of the AC motor from the acceleration generated from the acceleration command calculation means, speed detection means for detecting the speed of the AC motor, the speed Speed control means for generating a torque command for the AC motor so as to match the speed detected with the command. A DC voltage command calculation means of the converter control means determines a DC voltage command corresponding to an acceleration command generated from the acceleration command calculation means of the PWM inverter control means. The AC motor drive system according to claim 1, wherein: 4. The converter control means according to claim 1, wherein the DC voltage command calculation means generates a DC voltage command for the smoothing capacitor, the DC voltage detection means detects a voltage of the smoothing capacitor, and is issued from the DC voltage command calculation means. 2. The PWM inverter control means according to claim 1, further comprising an input current control means for controlling an input current of said converter so that the DC voltage command is made to match a DC voltage detected by said DC voltage detection means. Speed command calculating means for generating a speed command; speed detecting means for detecting the speed of the AC motor; and speed control means for generating a torque command for the AC motor so as to match the speed detected with the speed command. And a converter / PWM inverter control system, wherein the DC voltage command calculation means of the converter control means includes a DC voltage command Is determined on the basis of a torque command obtained from the speed control means. 5. A DC voltage command calculation means for generating a DC voltage command for a smoothing capacitor, a DC voltage detection means for detecting a voltage of the smoothing capacitor, and a DC voltage command calculation as part of the converter control means according to claim 1. 2. The PWM inverter control means according to claim 1, further comprising an input current control means for controlling an input current of said converter so that a DC voltage command issued by said means matches a DC voltage detected by said DC voltage detection means. In part, a speed command calculating means for generating a speed command for the AC motor, a speed detecting means for detecting the speed of the AC motor, a torque command for the AC motor so that the detected speed matches the detected speed. Speed control means for controlling the torque current and the excitation current flowing through the AC motor so that a torque corresponding to the torque command is generated. A converter / PWM inverter control system is configured so as to include a current control means for controlling the smoothing capacitor so that the voltage command of the PWM inverter obtained from the current control means does not exceed a predetermined value. The AC motor drive system according to claim 1, wherein the AC motor drive system is determined. 6. The DC voltage command calculating means according to claim 2, wherein the lower limit value is a smoothing capacitor voltage obtained when the converter section is a rectifier formed of a diode, and is used for an allowable voltage of the smoothing capacitor and a PWM inverter. 3. The method according to claim 2, wherein a smaller one of the allowable values is set as an upper limit value, and the DC voltage command is varied within this range so as to be the same as a change in the speed command of the AC motor. AC motor drive system. 7. The DC voltage command calculation means increases or decreases the DC voltage command so that a speed deviation of a speed control system of the AC motor or a torque command which is an output signal of the speed control system falls within a prescribed value. The AC motor drive system according to claim 2. 8. A converter for converting a commercial power supply into a DC voltage, a capacitor for smoothing the output voltage of the converter, a PWM inverter for converting the DC voltage of the smoothing capacitor into an AC voltage having a variable voltage and a variable frequency, and a PWM inverter. An AC motor drive system including an AC motor driven at a variable speed, comprising a power supply voltage detecting means for detecting a voltage of the commercial power supply, wherein the voltage detected by the power supply voltage detecting means falls below a predetermined value. If a power failure is determined, the operation of the converter is stopped, the voltage of the smoothing capacitor is reduced to a predetermined value, and when the voltage of the smoothing capacitor reaches a predetermined value, a DC current is supplied to the AC motor via the PWM inverter. Flow to reduce the speed of the AC motor to a predetermined speed. AC motor drive system. 9. A converter for converting a commercial power supply into a DC voltage, a capacitor for smoothing the output voltage of the converter, a PWM inverter for converting the DC voltage of the smoothing capacitor into an AC voltage having a variable voltage and a variable frequency, and a PWM inverter. An AC motor driving system including an AC motor driven by variable speed driving, comprising: a power supply voltage detecting means for detecting a voltage of the commercial power supply; and a large-capacity power capacitor connected in parallel with the smoothing capacitor. If a power failure is detected, the speed of the motor is reduced, and the regenerative energy at the time of deceleration is once collected in the smoothing capacitor, and when the terminal voltage of the smoothing capacitor exceeds a specified value, the voltage is increased. An AC motor drive system characterized by regenerating to a capacitor. 10. The AC motor driving system according to claim 9, further comprising a large capacitor voltage detecting means for detecting a voltage of the large capacitor, wherein the voltage detected by the large capacitor voltage detecting means is a predetermined voltage. Is supplied as control power for the converter / PWM inverter or power for driving peripheral devices of the motor drive system when the value of the motor drive system is exceeded. 11. A converter control device comprising: a converter voltage detector for detecting an input voltage of a converter; a converter input current detector; a DC voltage detector for detecting a voltage of a smoothing capacitor; DC voltage command calculation means for generating a command, and an input current for controlling an input current of the converter so that a DC voltage detected by the DC voltage detection means matches a DC voltage command issued from the DC voltage command calculation means. A control means for increasing / decreasing a DC voltage command within a specified range, and sequentially calculating input power input to the converter from the detected input voltage and input current in response to each of the increase / decrease operations. ,
2. The AC motor drive system according to claim 1, wherein a value of the smaller DC voltage command of the obtained input power is used as a true DC voltage command to control the input current of the converter. .