CN115313500B - Control method of four-quadrant power unit - Google Patents
Control method of four-quadrant power unit Download PDFInfo
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- CN115313500B CN115313500B CN202211243618.1A CN202211243618A CN115313500B CN 115313500 B CN115313500 B CN 115313500B CN 202211243618 A CN202211243618 A CN 202211243618A CN 115313500 B CN115313500 B CN 115313500B
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- 230000002441 reversible effect Effects 0.000 claims abstract description 4
- 230000001360 synchronised effect Effects 0.000 claims description 32
- 238000005070 sampling Methods 0.000 claims description 22
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- 230000003068 static effect Effects 0.000 claims description 8
- 238000004891 communication Methods 0.000 claims description 3
- 230000004907 flux Effects 0.000 claims description 3
- 238000010248 power generation Methods 0.000 claims description 3
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- 238000010586 diagram Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 3
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/22—Current control, e.g. using a current control loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
The invention discloses a control method of a four-quadrant power unit, wherein in an electric state, a PWM rectifying module carries out PWM modulation on three-phase voltage of a power grid, an SVPWM vector angle of the PWM rectifying module is dynamically lagged behind the vector angle of the power grid, the input power factor of the power grid is close to 1, the voltage of a direct-current bus is in a voltage stabilizing state, active power factor compensation is completed, and forward flow of energy from the power grid to a motor is realized; in the feeding state, when the inversion module and the motor operate in a braking state and the voltage of the direct current bus is increased, the SVPWM vector angle of the PWM rectification module is adjusted to lead the SVPWM vector angle to the power grid vector angle dynamically, and the motor operates in a feedback state, so that the bus direct current is modulated into three-phase alternating current and is combined with the power grid, the bus voltage is stabilized, and the reverse flow of energy from the motor to the power grid is realized. The invention can ensure that the bus voltage is stabilized in a safe interval when the power unit works, and keep the four-quadrant power unit stable in operation.
Description
Technical Field
The invention relates to a high-voltage frequency converter, in particular to a control method of a four-quadrant power unit.
Background
The cascade four-quadrant high-voltage frequency converter is key equipment of a high-voltage motor frequency conversion driving system, and is widely applied to energy-saving operation control and process speed regulation control of 10kV and 6kV high-voltage high-power motors. The cascade high-voltage frequency converter is mainly composed of a phase-shifting transformer and 3N power units, wherein every N power units are connected in series to form a phase-shifting frequency-changing voltage-changing power supply, 3N power units can form three single-phase frequency-changing voltage-changing power supplies, the three single-phase frequency-changing voltage-changing power supplies are connected into a star shape, the three-phase output frequency-changing voltage-changing power supplies are formed, and the high-voltage output capacity is formed due to the cascade of the units and can be used for controlling the operation of a high-voltage motor.
In the motor power generation state, the four-quadrant power unit carries out PWM rectification on the voltage with the over-high unit bus, and the voltage is fed back to the power grid through the phase-shifting transformer, so that the four-quadrant frequency converter is kept stable in operation.
When the four-quadrant power unit PWM rectifying module works in an electric state, active power factor adjustment is carried out on unit alternating current input, so that the alternating current input power factor is close to 1.
Three-phase output of the high-voltage frequency converter, each phase is connected in series by a plurality of four-quadrant power units, three-phase unbalance can occur as long as the load is carried, at the moment, the bus voltage of the three-phase units can be inconsistent, the input of the four-quadrant power units comes from a phase-shifting transformer with multiple output windings, the multiple output windings share one iron core, and the phenomenon of instability of mutual interference can also occur; the bus voltage stability is an important guarantee for ensuring stable operation and operation safety, the output power of the bus voltage is too low and does not reach the standard, the bus voltage is too high to generate the risk of explosion, and the bus voltage severely fluctuates to cause the unstable operation of the four-quadrant power unit.
Disclosure of Invention
The invention aims to provide a control method of a four-quadrant power unit, which can stabilize the bus voltage of the power unit in a safety interval.
In order to solve the technical problems, the invention adopts the technical scheme that the four-quadrant power unit comprises a PWM rectifying module, an inversion module and a control circuit, wherein the PWM rectifying module is provided with a three-phase alternating current input end and is connected with a three-phase alternating current power supply of a power grid to convert received alternating current into direct current; the inversion module is provided with an alternating current output end, is connected with the PWM rectification module through a direct current bus and is used for converting direct current into alternating current with adjustable frequency and driving a motor connected with the alternating current output end; the control circuit is respectively connected with the PWM rectifying module and the inversion module and is used for controlling the PWM rectifying module and the inversion module, and the control method comprises the following control steps:
101 Electric state): the PWM rectifying module carries out PWM modulation on three-phase voltage of the power grid, the SVPWM vector angle of the PWM rectifying module is dynamically lagged behind the power grid vector angle, the input power factor of the power grid is close to 1, the direct current bus voltage is in a voltage stabilizing state, active power factor compensation is completed, and forward flow of energy from the power grid to the motor is realized;
102 Feeding state): when the inversion module and the motor operate in a braking state and the voltage of a direct current bus is increased, the SVPWM vector angle of the PWM rectification module is adjusted to lead the SVPWM vector angle of the motor to be the power grid vector angle dynamically, and the motor operates in a feedback state, so that the bus direct current is modulated into three-phase alternating current and is combined with the power grid, the bus voltage is stabilized, and the reverse flow of energy from the motor to the power grid is realized.
The control method of the four-quadrant power unit comprises the following control steps:
201 Three-phase alternating voltage of the power grid is collected in real time, and a vector angle of the power grid is obtained through virtual flux linkage estimation;
202 The three-phase alternating current input into the PWM rectifying module is collected in real time, a controllable vector is obtained through alpha beta/dq conversion, and the voltage of a direct current bus tends to be stable through a PI regulator;
203 Detecting the voltage of the direct current bus in real time, and comparing the sampling value of the voltage of the direct current bus with the set value of the direct current bus;
204 When the voltage of the direct current bus drops to the set lower limit value, the vector angle of the PWM rectifying module is dynamically delayed from the vector angle of the power grid through space vector conversion, so that the voltage of the direct current bus tends to be stabilized at the set lower limit value;
205 When the DC bus voltage rises to the set upper limit value, the vector angle of the PWM rectifying module is dynamically advanced to the vector angle of the power grid through space vector conversion, so that the DC bus voltage tends to be stabilized at the set upper limit value.
The control method of the four-quadrant power unit comprises the following control steps:
the control circuit comprises a controller, a three-phase alternating current voltage sampling circuit, a three-phase alternating current sampling circuit and a direct current bus voltage sampling circuit, and comprises the following control steps:
301 The three-phase alternating voltage sampling signals are processed and decomposed into a grid voltage vector angle, a direct-axis voltage component of a d q synchronous rotation coordinate system and a quadrature-axis voltage component of a d q synchronous rotation coordinate system through a first signal processing unit;
302 The three-phase alternating current sampling signal is processed and decomposed into a direct-axis current component of a d q synchronous rotation coordinate system and a quadrature-axis current component of a d q synchronous rotation coordinate system by a second signal processing unit;
303 The phase-locked loop module outputs the phase-locked grid voltage vector angle;
304 Performing difference operation and PI operation on the DC bus voltage sampling value and the DC bus voltage setting value to obtain a direct-axis current reference and a quadrature-axis current reference of the d q synchronous rotation coordinate system;
305 A direct-axis current component id and a direct-axis current reference are subjected to difference operation and PI operation to obtain a direct-axis voltage compensation value, and a quadrature-axis current component iq and a quadrature-axis current reference are subjected to difference operation and PI operation to obtain a quadrature-axis voltage compensation value;
306 The direct-axis voltage component ud and the direct-axis voltage compensation value are summed to obtain a direct-axis voltage correction value, and the quadrature-axis voltage component uq and the quadrature-axis voltage compensation value are summed to obtain a quadrature-axis voltage correction value;
307 The phase-locked grid voltage vector angle theta o, the direct axis voltage correction value and the quadrature axis voltage correction value are respectively input into an inverse transformation module of the synchronous rotation coordinate system, and the direct axis voltage correction value and the quadrature axis voltage correction value are transformed into alpha beta static coordinate system data by the data of the dq synchronous rotation coordinate system; outputting an alpha-axis voltage component and a beta-axis voltage component of an alpha-beta static coordinate system;
308 An alpha-axis voltage component and a beta-axis voltage component of the alpha-beta static coordinate system are input into a PWM data generation module to generate PWM driving signals for controlling the PWM rectification module.
In the control method of the four-quadrant power unit, the controller is formed by combining the DSP, the MCu and the CPLD, wherein the DSP is used as a main control and is responsible for important data operation; MCu is responsible for data acquisition and communication; CPLD is responsible for PWM operation line on-off, fault protection quick linkage, switch logic processing and IO port expansion.
The invention can ensure that the bus voltage is stabilized in a safe interval when the power unit works, and keep the four-quadrant power unit stable in operation.
Drawings
The invention will be described in further detail with reference to the drawings and the detailed description.
Fig. 1 is a schematic block diagram of a four-quadrant power cell main circuit according to an embodiment of the present invention.
Fig. 2 is a control schematic diagram of a four-quadrant power cell according to an embodiment of the invention.
Fig. 3 is a flowchart of a control method of a four-quadrant power unit according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of a synchronous rotating coordinate system according to an embodiment of the present invention.
Fig. 5 is a diagram of the operational effect of the biquad generalized integral PI phase-locked loop of an embodiment of the present invention.
Detailed Description
The principle of the four-quadrant power unit control method of the embodiment of the invention is shown in fig. 1 to 5, and the four-quadrant power unit comprises a PWM rectifying module (PWM three-phase IGBT rectifying bridge) 116, an inverter module 119 and a control circuit, wherein the PWM rectifying module has a three-phase ac input end, and is connected with a three-phase ac power supply of a power grid 110 and an output end of a phase-shifting transformer through a reactor 117 to convert received ac power into dc power; the inversion module is provided with an alternating current output end, is connected with the PWM rectification module through a direct current bus and is used for converting direct current into alternating current with adjustable frequency and driving a motor connected with the alternating current output end; the DC bus is connected with a bus capacitor 118; the control circuit is respectively connected with the PWM rectifying module and the inversion module and is used for controlling the PWM rectifying module and the inversion module. The general serial port between the PWM rectifying module and the inversion module is communicated in the unit, 20mS is carried out once, and the inversion module refreshes the data of the PWM rectifying module at a high speed according to a frame period of 30 microseconds after receiving the data, and uploads the data to the control circuit.
The control method mainly comprises the following control steps:
1) Electric state: the PWM rectifying module carries out PWM modulation on three-phase voltage of the power grid, the SVPWM vector angle of the PWM rectifying module is dynamically lagged behind the power grid vector angle, the input power factor of the power grid is close to 1, the direct current bus voltage is in a voltage stabilizing state, active power factor compensation is completed, and forward flow of energy from the power grid to the motor is realized;
2) Feed state: when the inversion module and the motor operate in a braking state and the voltage of a direct current bus is increased, the SVPWM vector angle of the PWM rectification module is adjusted to lead the SVPWM vector angle of the motor to be the power grid vector angle dynamically, and the motor operates in a feedback state, so that the bus direct current is modulated into three-phase alternating current and is combined with the power grid, the bus voltage is stabilized, and the reverse flow of energy from the motor to the power grid is realized.
The flow of the four-quadrant power unit control method in the embodiment of the invention is shown in fig. 3, and the method comprises the following control steps:
1) Step 316 and 317 are performed to collect three-phase ac voltage of the power grid in real time, and obtain a vector angle of the power grid through virtual flux linkage estimation; the operation process comprises a power grid phase-locked loop, a stable power grid phase is provided, and the phase-locked loop can be kept stable even if the power grid voltage has severe fluctuation;
2) Step 318, 319 and 320, collecting three-phase alternating current input into the PWM rectification module in real time from between the reactor and the PWM rectification module, obtaining a controllable vector through alpha beta/dq conversion, and stabilizing the voltage of the direct current bus through the PI regulator;
3) Step 307, step 304, step 305, step 309 and step 310 are performed to detect the dc bus voltage in real time, and comparing the sampled value of the dc bus voltage with the set value of the dc bus;
4) In the electric state of the motor, the bus voltage is reduced less when the motor is lightly loaded, and the DC bus voltage is reduced to a 6 pulse wave rectifying base line when the motor is heavily loaded; when the dc bus voltage drops to the set lower limit value 970V, steps 306 and 312 enable the vector angle of the PWM rectifying module to dynamically lag the vector angle of the power grid through space vector conversion and PI regulator, so that the dc bus voltage tends to be stabilized at the set lower limit value 970V and the current of the power grid tends to be stabilized;
5) In the power generation state of the motor, the motor is in the running states of speed reduction, galloping or restarting and the like, the energy of the motor can flow reversely, and the generated electric energy charges a bus capacitor through an inversion module; as shown in steps 311 and 312, when the dc bus voltage rises to the set upper limit 1150V, the vector angle of the PWM rectifying module is dynamically advanced to the grid vector angle by the space vector conversion and PI regulator, so that the dc bus voltage tends to be stabilized at the set upper limit 1150V, and the current of the grid tends to be stabilized.
The control principle of the four-quadrant power unit in the embodiment of the invention is shown in fig. 2:
the control circuit comprises a controller, a three-phase alternating current voltage sampling circuit, a three-phase alternating current sampling circuit and a direct current bus voltage sampling circuit, and comprises the following control steps:
1) Sampling signals of three-phase alternating voltages ua, ub and uc output by the phase-shifting transformer and obtained by a three-phase alternating voltage sampling circuit are calculated by a first signal processing unit 111, and a direct-axis voltage component ud of a grid voltage vector angle theta and d q synchronous rotation coordinate system and an intersecting-axis voltage component uq of a d q synchronous rotation coordinate system are decomposed;
2) The three-phase alternating current sampling circuit samples currents ia, ib and ic between the reactor 117 and the PWM rectification module 116, and the three-phase alternating current sampling signal is processed and decomposed into a direct-axis current component id of a d q synchronous rotation coordinate system and an quadrature-axis current component iq of the d q synchronous rotation coordinate system by the second signal processing unit 112; the direct-axis voltage component ud, the quadrature-axis voltage component uq, the direct-axis current component id and the quadrature-axis current component iq are controllable vectors, so that the next operation is facilitated;
3) The power grid voltage vector angle theta is input into a phase-locked loop module, and the phase-locked loop module outputs the phase-locked power grid voltage vector angle theta;
4) Performing difference operation and PI operation on the DC bus voltage sampling value Vdc and the DC bus voltage setting value Vdc to obtain a direct-axis current reference (id_reference) and a quadrature-axis current reference (iq_reference) of a d q synchronous rotation coordinate system;
5) Performing difference operation and PI operation on the direct-axis current component id and the direct-axis current reference (id_reference) to obtain a direct-axis voltage compensation value, and performing difference operation and PI operation on the quadrature-axis current component iq and the quadrature-axis current reference (iq_reference) to obtain a quadrature-axis voltage compensation value;
6) The direct-axis voltage component ud and the direct-axis voltage compensation value are summed to obtain a direct-axis voltage correction value, and the quadrature-axis voltage component uq and the quadrature-axis voltage compensation value are summed to obtain a quadrature-axis voltage correction value;
7) The phase-locked grid voltage vector angle theta o, the direct axis voltage correction value and the quadrature axis voltage correction value are respectively input into an inverse transformation module 114 of the synchronous rotation coordinate system, and the direct axis voltage correction value and the quadrature axis voltage correction value are transformed into alpha beta static coordinate system data by the data of the dq synchronous rotation coordinate system; outputting an alpha-axis voltage component and a beta-axis voltage component of an alpha-beta static coordinate system;
8) The α -axis voltage component and the β -axis voltage component of the αβ stationary coordinate system are input to the PWM data generation module 115, which generates PWM drive signals that control the PWM rectification module 116.
According to the control method provided by the embodiment of the invention, the bus voltage and the power grid current tend to be stable through PI regulation; the PI regulator dynamically advances or retards the PWM rectified vector angle to the grid vector angle such that the bus voltage stabilizes around the target voltage value and the grid operating current tends to stabilize in either the motoring or generating state.
The controller is formed by combining a DSP (digital signal processor), an MCu (micro controller unit) and a CPLD (complex programmable logic device), wherein the DSP is used as a main control and is responsible for important data operation; MCu is responsible for data acquisition and communication; CPLD is responsible for PWM operation line on-off, fault protection quick linkage, switch logic processing and IO port expansion.
The phase-locked loop module is a biquad generalized integral PI phase-locked loop based on combination of software and hardware, namely, based on a synchronous rotation coordinate system and a second-quad generalized integral PI phase-locked loop, and can accurately acquire frequency and phase information of positive sequence components of the power grid voltage under the conditions of unbalanced power grid voltage, voltage sag, frequency mutation or multiple harmonics.
The above phase locked loop satisfies the following formula condition:
when the angle θ=θ2=θo, the angular frequency ω1=ω2, the phase difference Φerr=0, the rotation coordinate direct axis ud=u, and the rotation coordinate quadrature axis uq=0, the phase lock is successful.
Wherein,,
uα is the α -axis voltage component of the αβ stationary coordinate system;
uβ is the β -axis voltage component of the αβ stationary coordinate system; ud is the direct axis voltage component of the d q synchronous rotating coordinate system;
uq is the quadrature voltage component of the d q synchronous rotation coordinate system;
θ is the input grid voltage vector angle θ;
θ2 is the vector angle of the software synchronous rotation coordinate system, namely the initial angle of the d q synchronous rotation coordinate system; θo is the grid voltage vector angle of the phase lock;
ω1 is the grid angular frequency;
ω2 is the software synchronous rotation coordinate system angular frequency; ω2 is the angular frequency obtained by calculating the angle theta 2 of the alpha beta software synchronous rotation coordinate system by the DSP arctangent related software module and the angle walked in unit time. ω2 is made close to or equal to ω1 by adjusting Φerr.
Φerr is the angular error of the input grid voltage vector angle θ and the synchronous rotation coordinate system vector angle input grid voltage vector angle θ2;
u is the phase voltage of the power grid, and is converted into ua, ub and uc in the operation process, then converted into uα and uβ, and then converted into ud and uq; i.e. the three variables of the three-phase voltage are finally converted into two variables which are easy to operate.
As shown in fig. 4, in the synchronous rotation coordinate system of the phase-locked loop d q, the vector included angle between the direct axis component and the quadrature axis component is θo, which is the vector included angle outputted after the phase locking of the three-phase alternating current; the d-axis component and the q-axis component can be converted into a formula so as to facilitate calculation and processing;
d expresses the voltage, and the larger d represents the larger back electromotive force, so that the output device and the target equipment reach energy balance, and the output force is counteracted; otherwise, deviating from the equilibrium state; the magnitude of q-expression output is generally expressed as uq/iq; the q value is positive rotation force, and the q value is negative rotation force; the larger the q value is, the smaller the d value is, and the acceleration or deceleration state is entered, otherwise, the equilibrium state is entered.
As shown in fig. 5, the power grid voltage is switched from the stable working condition to the severe working condition, the phase-locked energy loop is kept stable, the waveform of the output PWM rectified voltage is kept stable, and the three-phase PWM rectified current is balanced and stable. In the view of figure 5 of the drawings,
201:INTPuT ubc is the input grid voltage waveform;
202: ud and uq are the sizes of the synchronous rotation coordinate system ud, uq on the time axis;
203: outputting a monitored vector angle theta o time axis;
204: Φerr is the phase-locked error timeline;
205: the ontrut ubc is the voltage waveform output to the grid.
According to the control method of the four-quadrant power unit, the balance is achieved in dynamic conversion of stability and transient response through the software-hardware combined biquad generalized integral PI phase-locked loop, so that bus voltage is stable between the upper limit and the lower limit, and the control method can quickly respond to keep safe operation of the four-quadrant power unit.
Claims (2)
1. The control method of the four-quadrant power unit comprises a PWM rectifying module, an inversion module and a control circuit, wherein the PWM rectifying module is provided with a three-phase alternating current input end and is connected with a three-phase alternating current power supply of a power grid to convert received alternating current into direct current; the inversion module is provided with an alternating current output end, is connected with the PWM rectification module through a direct current bus and is used for converting direct current into alternating current with adjustable frequency and driving a motor connected with the alternating current output end; the control circuit is respectively connected with the PWM rectifying module and the inversion module and is used for controlling the PWM rectifying module and the inversion module, and is characterized by comprising the following control steps:
101 Electric state): the PWM rectifying module carries out PWM modulation on three-phase voltage of the power grid, the SVPWM vector angle of the PWM rectifying module is dynamically lagged behind the power grid vector angle, the input power factor of the power grid is close to 1, the direct current bus voltage is in a voltage stabilizing state, active power factor compensation is completed, and forward flow of energy from the power grid to the motor is realized;
102 Feeding state): when the inversion module and the motor operate in a braking state and the voltage of a direct current bus is increased, the SVPWM vector angle of the PWM rectification module is adjusted to lead the SVPWM vector angle to the power grid vector angle dynamically, and the motor operates in a feedback state, so that the bus direct current is modulated into three-phase alternating current and is combined with the power grid, the bus voltage is stabilized, and the reverse flow of energy from the motor to the power grid is realized;
meanwhile, the method also comprises the following control steps:
103 Three-phase alternating voltage of the power grid is collected in real time, and a vector angle of the power grid is obtained through virtual flux linkage estimation;
104 The three-phase alternating current input into the PWM rectifying module is collected in real time, a controllable vector is obtained through alpha beta/dq conversion, and the voltage of a direct current bus tends to be stable through a PI regulator;
105 Detecting the voltage of the direct current bus in real time, and comparing the sampling value of the voltage of the direct current bus with the set value of the direct current bus;
106 Under the electric state of the motor, when the voltage of the direct current bus drops to the set lower limit value 970V, the vector angle of the PWM rectifying module is dynamically delayed from the vector angle of the power grid through space vector conversion and a PI regulator, so that the voltage of the direct current bus tends to be stabilized at the set lower limit value 970V;
107 Under the power generation state of the motor, when the voltage of the direct current bus rises to the set upper limit value 1150V, the vector angle of the PWM rectifying module is dynamically advanced to the vector angle of the power grid through space vector conversion and a PI regulator, so that the voltage of the direct current bus tends to be stabilized at the set upper limit value 1150V;
the control circuit also comprises a controller, a three-phase alternating current voltage sampling circuit, a three-phase alternating current sampling circuit and a direct current bus voltage sampling circuit, and comprises the following control steps:
201 The three-phase alternating voltage sampling signals are processed and decomposed into a grid voltage vector angle, a direct-axis voltage component of a d q synchronous rotation coordinate system and a quadrature-axis voltage component of a d q synchronous rotation coordinate system through a first signal processing unit;
202 The three-phase alternating current sampling signal is processed and decomposed into a direct-axis current component of a d q synchronous rotation coordinate system and a quadrature-axis current component of a d q synchronous rotation coordinate system by a second signal processing unit;
203 The phase-locked loop module outputs the phase-locked grid voltage vector angle;
204 Performing difference operation and PI operation on the DC bus voltage sampling value and the DC bus voltage setting value to obtain a direct-axis current reference and a quadrature-axis current reference of the d q synchronous rotation coordinate system;
205 A direct-axis current component id and a direct-axis current reference are subjected to difference operation and PI operation to obtain a direct-axis voltage compensation value, and a quadrature-axis current component iq and a quadrature-axis current reference are subjected to difference operation and PI operation to obtain a quadrature-axis voltage compensation value;
206 A direct axis voltage component ud and a direct axis voltage compensation value to obtain a direct axis voltage correction value, a quadrature axis voltage component uq and a quadrature axis voltage compensation value to obtain a quadrature axis voltage correction value,
207 The phase-locked grid voltage vector angle theta o, the direct axis voltage correction value and the quadrature axis voltage correction value are respectively input into an inverse transformation module of the synchronous rotation coordinate system, and the direct axis voltage correction value and the quadrature axis voltage correction value are transformed into alpha beta static coordinate system data by the data of the dq synchronous rotation coordinate system; outputting an alpha-axis voltage component and a beta-axis voltage component of an alpha-beta static coordinate system;
208 An alpha-axis voltage component and a beta-axis voltage component of the alpha-beta static coordinate system are input into a PWM data generation module to generate PWM driving signals for controlling the PWM rectification module.
2. The control method of the four-quadrant power unit according to claim 1, wherein the controller is composed of a DSP, an MCu and a CPLD, and the DSP is used as a master control and is responsible for important data operation;
MCu is responsible for data acquisition and communication; CPLD is responsible for PWM operation line on-off, fault protection quick linkage, switch logic processing and IO port expansion.
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