JP4931105B2 - Electric vehicle power converter - Google Patents

Description

  The present invention relates to an improved power converter for an electric vehicle (hereinafter referred to as EV).

  Conventional EV power converters are usually configured to drive a induction motor or a synchronous motor by converting a direct current power source such as a battery and the direct current from the direct current power source into an alternating current by an inverter.

  For the control of the inverter, so-called vector control is used. That is, the torque current command iq * and the excitation current command id * orthogonal to the torque current command iq * and the feedback-calculated torque current iq and excitation current id are respectively compared and calculated by an amplifier, and the respective outputs are output to the torque voltage command vq * and the excitation current. The voltage command is vd *. The torque voltage command vq * and the excitation voltage command vd * are converted into a three-phase voltage reference V * by a coordinate converter, which is converted into a pulse by a PWM controller to obtain an inverter gate signal.

  Here, the torque current command iq * is limited by a torque current command limit determined by the rotational speed n detected by the speed detector. The torque current command limit is set to a torque current command maximum value for each rotation speed. Although there is a case where the torque command is limited instead of the torque current command, the operation is the same.

  On the other hand, the torque current iq and the excitation current id described above detect an arbitrary two-phase output current of the inverter, for example, a U-phase current iu and a W-phase current iw, and this is converted from three phases to two phases by a coordinate converter. Convert to find. Here, the reference phase of the coordinate converter is the slip frequency fs obtained by calculation from the phase angle θr obtained by integrating the rotational speed n of the induction motor detected by the speed detector, the torque current command iq *, and the excitation current command id *. The phase angle θ obtained by adding the phase angle θs obtained by integrating is used. The phase angle θ is similarly used for the reference phase of the coordinate converter described above. This phase angle θ corresponds to the electrical angle formed by the output phase of the inverter and the rotating magnetic field of the induction motor. The motor rotation speed n can also be obtained by calculation without using a speed detector. This is so-called sensorless vector control.

  In general, in the EV, the direct current power source is a battery, and in this case, the voltage varies greatly depending on the state of charging and discharging and the load condition. Even if the same current flows, the voltage varies depending on the state of charge of the battery.

  In EV, the vehicle is started and accelerated by the discharge energy from the battery, and the kinetic energy of the vehicle is regenerated to the battery at the time of deceleration. Therefore, a large amount of energy is required, and the current for discharging and charging also increases. However, since the battery is mounted on the vehicle, the capacity is relatively small due to restrictions such as size and weight. For this reason, when a large current flows, the direct current (battery) voltage decreases during discharging, and the direct current (battery) voltage increases during charging. This voltage fluctuation may exceed ± 20%, and the voltage fluctuation becomes much larger than that of a general DC power source using a commercial power source.

  As the torque output of the electric motor increases, the electric current of the electric motor increases and the required voltage supplied to the electric motor increases. However, the upper limit of the voltage supplied from the inverter to the electric motor is determined by the direct current (battery) voltage. When the torque current command mitt is set in a state where the direct current (battery) voltage is low, the torque current command mitt becomes small and the battery capacity cannot be effectively utilized when the battery voltage is high. Conversely, if the torque current command mitt is set while the direct current (battery) voltage is high, the inverter output voltage is saturated when the battery voltage is low, making it difficult to control the motor current, and in some cases an overcurrent may occur. is there.

As a countermeasure against the above problem, a proposal has been made to reduce the torque command value when the voltage command of the inverter exceeds a predetermined voltage limit value determined by the battery voltage (see, for example, Patent Document 1).
JP 2003-128398 A (page 3-4, FIG. 2)

  According to the technique disclosed in Patent Document 1, when the output voltage command of the inverter exceeds a predetermined value, the torque command is reduced, so that the torque can be adjusted according to the voltage of the battery. However, since the procedure for converting the battery voltage to the inverter output voltage is required, the circuit is complicated and the operation state of the motor is not taken into consideration, so the motor determines the predetermined value in the power running state. When the electric motor is regeneratively operated, the torque is limited more than necessary, resulting in a decrease in operating efficiency.

  The present invention has been made in view of the above problems, and effectively uses battery capacity by performing control according to a direct current (battery) voltage and an operating state of an electric motor with a relatively simple circuit configuration. It aims at providing the power converter device for EV.

In order to achieve the above object, a power converter for an electric vehicle according to a first aspect of the present invention includes an inverter circuit that converts DC power from a DC power source into AC to drive an AC motor, and the inverter circuit. Control means for controlling, rotation speed detection means for directly or indirectly detecting the rotation speed of the AC motor, and voltage detection means for detecting a DC voltage of the inverter circuit, wherein the control means comprises the AC Vector control means for separating the current of the motor into an excitation current and a torque current orthogonal thereto, and adjusting the voltage command of the inverter circuit according to a deviation from each command value, and whether the AC motor is in a power running state A power running / regeneration determining means for determining whether the engine is in a regenerative operation state, and when the rotational speed by the rotational speed detecting means is less than or equal to a predetermined value, the torque current limit is When the output of the raw judgment means is a power running, it becomes a positive constant value, and when it is regenerative, it becomes a negative constant value, and when the rotational speed exceeds the predetermined value, the torque current limit is set to the rotational speed. When the output of the power running / regeneration determining means is power running and the rotational speed exceeds the predetermined value, the torque current limit is set substantially proportional to the voltage by the voltage detecting means. It is characterized by being reduced .

The electric vehicle power converter according to the second aspect of the present invention includes an inverter circuit that converts direct current power from a direct current power source into alternating current to drive an alternating current motor, and control means that controls the inverter circuit; A rotation speed detecting means for directly or indirectly detecting the rotation speed of the AC motor, and the control means separates the current of the AC motor into an excitation current and a torque current orthogonal thereto, and A vector control means for adjusting a voltage command of the inverter circuit according to a deviation from the value; and a power running / regeneration judgment means for judging whether the AC motor is in a power running operation state or a regenerative operation state, and the rotational speed When the number of revolutions by the detection means is less than or equal to a predetermined value, the torque current limit is a positive constant value when the output of the power running / regeneration determination means is power running, and a negative constant value when the output is regenerative. And when the rotational speed exceeds the predetermined value, the torque current limit is reduced substantially inversely proportional to the rotational speed, the output of the power running / regeneration determining means is power running, and the voltage command is predetermined. When the value is equal to or greater than the value, the torque current limit is linearly reduced toward 0 with respect to the increase in the voltage command.

  According to the present invention, it is possible to provide an EV power conversion device that effectively uses battery capacity by performing control according to a direct current (battery) voltage and an operating state of an electric motor with a relatively simple circuit configuration. It becomes possible.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, an EV power converter according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block configuration diagram of an EV power converter according to Embodiment 1 of the present invention.

  The DC power source 1 supplies DC power to the inverter 3 via the switch 2, and the inverter 3 converts this DC power into AC and drives the AC motor 4.

  The inside of the inverter 3 includes a capacitor 32 for smoothing a DC voltage and an inverter circuit 33 in which main circuit elements 33u, 33v, 33w, 33x, 33y, and 33z are bridge-connected. The inverter circuit 33 is controlled by the control circuit 34.

The AC motor 4 is provided with a speed detector 5 and supplies a rotation speed signal to the control circuit 34. The configuration of the control circuit 34 is as follows. The given torque current (q-axis current) command iq * is compared with the torque current (q-axis current) iq feedback-calculated via the limit circuit 341, and this deviation is adjusted by the amplifier 342 to obtain the q-axis voltage command. Outputs vq *. Similarly, the excitation current (d-axis current) command id * is compared with the feedback-calculated excitation current (d-axis current) id, and the deviation is adjusted by the amplifier 343 to output the d-axis voltage command vd *. The q-axis voltage command vq * and the d-axis voltage command vd * obtained here are converted into a three-phase voltage reference V * by the coordinate converter 344, and converted into a pulse by the PWM controller 345 for the inverter circuit 33. Getting the gate signal.

  On the other hand, the q-axis current iq and the d-axis current id described above detect an arbitrary two-phase output current of the inverter 3, for example, a U-phase current iu and a W-phase current iw, and this is converted into a three-phase by a coordinate converter 346. It is obtained by converting from 2 to 2 phase. Here, the reference phase of the coordinate converter 346 is obtained by integrating the phase angle θr obtained by integrating the rotational speed n of the AC motor 4 and the slip frequency fs obtained by calculation from the torque current command iq * and the excitation current command id *. A phase angle θ obtained by adding the obtained phase angle θs is used. The phase angle θ is similarly used for the reference phase of the coordinate converter 344 described above. As described above, the method of separating the current of the AC motor 4 into the torque current and the excitation current and independently controlling them is well known as so-called vector control.

  The DC voltage of the inverter 3 is detected by the voltage detector 347 and applied to the torque current limit circuit 348. The torque current limit circuit 348 is supplied with the rotation speed signal that is the output of the speed detector 5 and the output of the power running / regeneration determination circuit 349 obtained from the torque current command iq *, and the limit circuit 341 is controlled by this output. In FIG. 1, the voltage detector 347 is provided inside the control circuit 34, but this may be provided outside the control circuit 34.

  FIG. 2 is an operation explanatory diagram of the torque current limit circuit 348.

  As shown in FIG. 2, the torque current command limit circuit 348 receives the rotation speed n and outputs a torque current command limit. When the regenerative operation is determined by the power running / regeneration determination circuit 349, the torque current command limit is set to the maximum value iq_max_n * during regeneration regardless of the value of the DC voltage Vdc. This iq_max_n * is normally a constant value up to the base speed n0, but when the speed exceeds n0 and becomes a field weakening region, it decreases in inverse proportion to the speed.

  Similarly, when the power running / regeneration determination circuit 349 determines that the power running operation is performed, the torque current command limit is set to the maximum value iq_max_n * during regeneration at the base speed n0 or less, but when the base speed n0 is exceeded. The value is changed according to the DC voltage Vdc. Assuming that the maximum value of the DC voltage is Vdc3, the lower voltage value is Vdc2, and the lower voltage value is Vdc1, the torque current command limit is reduced as the DC voltage decreases from Vdc3 to Vdc1, as shown.

  Thus, by changing the torque current command limit according to the direct current (battery) voltage, the inverter output voltage can be prevented from being saturated even if the direct current (battery) voltage fluctuates during power running. Further, when the battery voltage is reduced during regeneration, the regenerative torque is maximized even if the output voltage of the inverter is somewhat saturated, and the battery voltage is recovered by ensuring the battery charge amount.

  It is obvious that the same effect can be obtained by applying a limit to the torque command instead of applying a limit to the torque current command. Further, although the power running / regeneration determination is performed based on the torque current command iq *, the power running / regeneration determination may be performed based on the DC current idc or the like.

  FIG. 3 is a block diagram of the EV power converter according to the second embodiment of the present invention. In each part of the second embodiment, the same parts as those in the block configuration diagram of the EV power converter according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The second embodiment is different from the first embodiment in that a voltage command calculation circuit 350 that calculates a voltage command Vdq * from a q-axis voltage command vq * and a d-axis voltage command vd *, and the voltage command Vdq * and power running / regeneration determination. A modulation rate limit circuit 351 that calculates a voltage reduction rate during powering from the output of the circuit 349 is provided, and the output of the modulation rate limit circuit 351 is multiplied by the output of the torque current command limit circuit 351A to operate the limit circuit 341. This is the point.

  Here, the calculation formula in the voltage command calculator is as follows.

Vdq * = {(vd *) ² + (vq *) ² } ^1/2
Hereinafter, the operation of the modulation rate limit circuit 351 will be described with reference to FIG.

  When the power running / regeneration determination circuit 349 determines that the power running operation is performed, the output of the modulation rate limit circuit is reduced from 1 to zero when the output of the voltage command computing unit 350 exceeds a predetermined value as shown in the figure. Like that. If this output is multiplied by the output of the torque current command limit circuit 348A and the limiter 341 is operated, the torque current command iq * is reduced when the voltage command Vdq * exceeds the reference value, so that the DC voltage Vdc fluctuates. Inverter output voltage will not be saturated. The output of the torque current command limit circuit 348A is set as a limit value at the maximum value of the DC voltage Vdc.

  When the power running / regeneration determination circuit 349 determines that the regenerative operation is performed, the modulation rate limit circuit 351 always outputs 1.

  In the field-weakening region, an increase in the rotational speed n corresponds to an increase in the voltage command Vdq *. Therefore, according to the second embodiment, the inverter output voltage does not saturate even when the direct current (battery) voltage fluctuates during powering. Can be. Further, when the battery voltage is reduced during regeneration, it is possible to maximize the regenerative torque and further secure the battery charge even if the output voltage of the inverter is somewhat saturated.

  Note that the same effect can be obtained by multiplying the output of the change rate limit circuit 351 by the output of the limit circuit 341 instead of the output of the torque current command limit circuit 348 to limit the torque current command iq *.

  FIG. 5 is a block diagram of an EV power converter according to Embodiment 3 of the present invention. About each part of this Example 3, the same part as each part of the block block diagram of the power converter device for EVs which concerns on Example 1 of FIG. 1 is shown with the same code | symbol, and the description is abbreviate | omitted. The third embodiment differs from the first embodiment in that a rate processing circuit 352 is provided, and a direct current (battery) voltage Vdc detected by the voltage detector 346 is applied to the torque current command limit circuit 348 via the rate processing circuit 352. This is the point that was configured.

Rate processing circuit 352, when direct current (battery) voltage is lowered without rate, the DC voltage is input to the torque current command limit the voltage detection value with a rate be elevated.

  FIG. 6 is an explanatory diagram of the operation of the rate processing circuit 352. FIG. 6A shows an operation example when the rate processing circuit 352 has no rate when the voltage drops and no rate when the voltage rises. When the torque command greatly increases stepwise at time t = t0, the direct current (battery) voltage decreases and the torque current command limit is narrowed. At time t = t1, since the torque current command limit is reduced, the direct current (battery) voltage rises and the torque current command limit rises again. Further, at time t = t2, the torque current command limit is increased, so that the voltage decreases again, and the state is the same as at time t = t0. This vibration phenomenon is repeated at times t = t3, t4, t5, and t6. .

  Next, FIG. 6B shows an operation example when the rate processing circuit 352 has no rate when the voltage drops and has a rate when the voltage rises. When the torque command greatly increases stepwise at time t = t0, the direct current (battery) voltage decreases and the torque current command limit is narrowed. As the torque current command limit is reduced, the direct current (battery) voltage rises and the torque current command limit tries to rise again, but the detected value of the direct current (battery) voltage is rate-processed. The command limit increases slowly. As a result, the vibration phenomenon shown in FIG. 6A can be suppressed, and stable operation can be performed even when a large torque command is input.

  In FIG. 5, the rate processing circuit 352 performs rate processing on the output of the voltage detector 346. This rate processing is provided at the output of the torque current command limit circuit 348, and the time change rate of the torque current command limit is set. May be configured to directly limit

  FIG. 7 is a block diagram of an EV power converter according to Embodiment 4 of the present invention. In the fourth embodiment, the same parts as those in the block configuration diagram of the EV power converter according to the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The fourth embodiment is different from the first embodiment in that the AC motor 4 is a synchronous motor, the slip frequency is not calculated, and the angle obtained by integrating the rotational speed n detected from the speed detector 5 remains as it is. This is the point where the phase θ is adopted.

  In the case of a synchronous motor, since the rotation speed n is proportional to the output frequency of the inverter 3, the speed detector 5 can be omitted.

  Also in the case of the first to third embodiments, the speed detector 5 can be omitted by using so-called sensorless vector control.

  Further, it is apparent that the first to fourth embodiments described above can be applied not only to EV but also to a hybrid EV power conversion device.

1 is a block configuration diagram of an EV power converter according to Embodiment 1 of the present invention. FIG. Operation explanatory diagram of torque current command limit circuit The block block diagram of the power converter device for EV which concerns on Example 2 of this invention. Operation explanatory diagram of modulation rate limit circuit The block block diagram of the power converter device for EV which concerns on Example 3 of this invention. Operation explanation diagram of rate processing circuit The block block diagram of the power converter device for EVs which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Switch 3 Inverter 4 AC motor 5 Speed detector 32 DC capacitor 33 Inverter circuit 34 Control circuit 341 Limit circuit 342 Amplifier 343 Amplifier 344 Coordinate converter 345 PWM circuit 346 Coordinate converter 347 Voltage detection circuit 348, 348A Torque Current command limit circuit 349 Power running / regeneration determination circuit 350 Voltage command calculation circuit 351 Modulation rate limit circuit 352 Rate processing circuit

Claims (4)

An inverter circuit for driving an AC motor by converting DC power from a DC power source into AC, and a control means for controlling the inverter circuit;
A rotational speed detection means for directly or indirectly detecting the rotational speed of the AC motor;
Voltage detecting means for detecting a DC voltage of the inverter circuit,
The control means includes
Vector control means for separating the current of the AC motor into an excitation current and a torque current orthogonal thereto, and adjusting a voltage command of the inverter circuit according to a deviation from each command value;
Power running / regeneration determination means for determining whether the AC motor is in a power running operation state or a regenerative operation state;
When the rotational speed by the rotational speed detection means is less than or equal to a predetermined value, the torque current limit becomes a positive constant value when the output of the power running / regeneration determination means is power running, and a negative constant value when regenerative. When the rotational speed exceeds the predetermined value, the limit of the torque current is reduced approximately in inverse proportion to the rotational speed, and the output of the power running / regeneration determination means is power running and the rotational speed is When the predetermined value is exceeded, the torque current limit is reduced approximately in proportion to the voltage by the voltage detection means. An inverter circuit for driving an AC motor by converting DC power from a DC power source into AC, and a control means for controlling the inverter circuit;
A rotation speed detecting means for directly or indirectly detecting the rotation speed of the AC motor;
The control means includes
Vector control means for separating the current of the AC motor into an excitation current and a torque current orthogonal thereto, and adjusting a voltage command of the inverter circuit according to a deviation from each command value;
Power running / regeneration determination means for determining whether the AC motor is in a power running operation state or a regenerative operation state;
When the rotational speed by the rotational speed detection means is less than or equal to a predetermined value, the torque current limit becomes a positive constant value when the output of the power running / regeneration determination means is power running, and a negative constant value when regenerative. When the rotational speed exceeds the predetermined value, the limit of the torque current is reduced approximately in inverse proportion to the rotational speed,
When the output of the power running / regeneration determination means is power running and the voltage command is greater than or equal to a predetermined value, the torque current limit is linearly reduced toward 0 with respect to the increase of the voltage command. A power converter for an electric vehicle.   2. The electric power converter for an electric vehicle according to claim 1, wherein rate setting means is provided such that a time change rate of the voltage by the voltage detection means is not more than a predetermined limit value. The rate setting means includes:
The limit value of the time change rate when the voltage rises,
The electric power converter for an electric vehicle according to claim 3, wherein the electric power converter is set to be larger than a limit value of the time change rate when the voltage drops.

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