CN112737070B - Integrated drive charging circuit and control system based on clamping type three-level converter - Google Patents

Integrated drive charging circuit and control system based on clamping type three-level converter Download PDF

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CN112737070B
CN112737070B CN202110080486.4A CN202110080486A CN112737070B CN 112737070 B CN112737070 B CN 112737070B CN 202110080486 A CN202110080486 A CN 202110080486A CN 112737070 B CN112737070 B CN 112737070B
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current
phase
grid
motor
interface
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CN112737070A (en
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蒋栋
高加楼
李柏杨
周敏
孙伟
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
    • H02J7/04—Regulation of charging current or voltage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
    • B60L53/20—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by converters located in the vehicle
    • 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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
    • Y02T10/92—Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Ac Motors In General (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses an integrated drive charging circuit and a control system based on a clamping type three-level converter, and belongs to the field of electric automobiles. The invention provides a method for selecting a motor phase winding to be connected into a power grid by adopting a three-level converter and changing a switching mode of a neutral point bridge arm of the three-level converter, wherein the phase connected into the power grid can be flexibly selected and changed through the neutral point bridge arm in the converter, and the current control strategy is combined to ensure that an integrated charger cannot generate motor torque and has the lowest loss when being connected into the power grid, and the realization of zero torque is independent of a rotor position angle and has the lowest loss. The auxiliary bridge arm is modulated, so that the current on the auxiliary inductor is controlled to reversely compensate the current flowing into the neutral point of the capacitor by the three-level converter under the motor driving condition, and the purpose of stabilizing the potential of the neutral point is finally achieved. According to the invention, an additional bridge arm and an additional inductor are added, and the additional elements can be connected into a power grid when being connected to the power grid, so that the system has a full-bridge property, and the power quality of the grid connection can be improved.

Description

Integrated drive charging circuit and control system based on clamping type three-level converter
Technical Field
The invention belongs to the field of electric automobiles, and particularly relates to an integrated driving charging circuit and a control system based on a clamping type three-level converter.
Background
The pure electric vehicle and the plug-in hybrid electric vehicle can effectively reduce carbon emission and increase energy utilization efficiency, and will replace an internal combustion engine vehicle in the future. However, the current electric vehicles face the problems of limited battery capacity and inconvenient energy supply, and only by effectively solving the two problems, the electric vehicles can be really accepted by the public. For the problem of inconvenient energy supply of batteries, the existing solutions include battery replacement and expansion of charging piles, but both methods require expensive construction cost. There is also a way to use an on-board charger, but this device is limited by space and cost in the vehicle, generally the power level is not high, and therefore the charging rate is limited.
The vehicle-mounted charging function is realized by utilizing the existing power electronic device in the electric automobile, the characteristics of large charging power and convenience can be considered, and the vehicle-mounted charging device has higher practical value. However, the integrated charging system proposed in the related document has a problem that the charging process generates motor torque and noise. For example, patent CN109167551A proposes an H-bridge automobile motor controller with integrated charging function, when a three-phase power grid is used to charge a battery, a three-phase symmetrical alternating current flows through the motor windings, and the current will generate an alternating torque to cause a motor squeal.
Disclosure of Invention
Aiming at the problem that the motor can generate torque when a motor controller is reused as a vehicle-mounted charger in the prior art, and the realization of zero torque is required to be independent of the position angle of a motor rotor; the invention provides an integrated driving charging circuit and a control system based on a clamping type three-level converter, aiming at realizing zero-torque grid connection to manage charging and discharging of a battery while ensuring the driving performance of a motor. Compared with the existing scheme, the invention has no problems of motor torque and noise in the charging process, and has the characteristics of high integration level and low cost, and the motor driving performance is better than that of a common driving motor conversion system.
To achieve the above object, according to a first aspect of the present invention, there is provided a single-motor-driven single-phase grid-connected integrated driving charging circuit based on a clamped three-level converter, the integrated driving charging circuit comprising: the device comprises a clamping type three-level converter, two direct current filter capacitors, an auxiliary inductor, an auxiliary two-level bridge arm, a working mode switching module, a direct current power supply side electric interface, a motor system alternating current side electric interface and a single-phase power grid interface;
the clamped three-level converter is composed of m clamped three-level bridge arms, and anodes Px of the clamped three-level bridge arms are in short circuit to form an anode P of an electric interface at the DC power supply side; the negative electrodes Nx of the three-level bridge arms are in short circuit together to form a negative electrode N of the electric interface at the DC power supply side; the AC interface ACx of the three-level bridge arm is independently connected out to form an AC side electrical interface of the motor system together, and the AC side electrical interface is connected with the m-phase AC motor; neutral points Ox of the three-level bridge arms are connected together to form a neutral point O of the clamping type three-level converter, wherein x is 1,2,3, m and m represent the phase number of the alternating current motor;
the two direct current filter capacitors are connected in series, and a positive electrode interface CP, a negative electrode interface CN and a neutral point interface CO are led out; the positive electrode interface CP is connected to the positive electrode P of the electric interface on the DC power supply side; the negative electrode interface CN is connected to the negative electrode N of the electric interface at the DC power supply side;
the working mode switching module is provided with three interfaces, namely an auxiliary inductor interface LP, a direct-current capacitor neutral point interface COP and a clamping type three-level converter neutral point interface IOP; the auxiliary inductor interface LP is connected with one end of an auxiliary inductor; the direct-current capacitor neutral point interface COP is connected with the neutral point interface CO; the neutral point interface IOP of the clamping type three-level converter is connected with a neutral point O;
the auxiliary inductor is provided with two ports, one end of the auxiliary inductor is connected to an auxiliary inductor interface LP of the working mode switching module, and the other end of the auxiliary inductor is connected with an alternating current side interface ACa of the two-level bridge arm unit;
the auxiliary two-level bridge arm is provided with a positive electrode Pa, a negative electrode Na and an alternating current side interface ACa, and the positive electrode Pa is connected to a positive electrode P of an electric interface on the direct current power supply side; the negative electrode Na is connected to the negative electrode N of the electrical interface at the DC power supply side; the alternating current side interface ACa is connected with one end of the auxiliary inductance unit;
the neutral point interface IOP and the auxiliary inductor interface LP of the clamping type three-level converter jointly form a single-phase power grid interface, and a power grid voltage sensor is arranged in the single-phase power grid interface and used for detecting the voltage of a power grid.
Has the advantages that: according to the invention, by adopting the clamping type three-level converter, the auxiliary inductor and the bridge arm, the neutral point current compensation function of the auxiliary inductor and the bridge arm and the three-level converter phase bridge arm can work in a zero-level switching mode, so that the balance of neutral point potential in the driving working condition and the random selection of motor phase windings accessed to a power grid under the grid-connected working condition are respectively realized, and the zero-torque grid-connected operation of any motor rotor d-axis position is realized.
Preferably, the working mode switching module comprises M power diode bridge arms and one power transistor bridge arm;
the number of the power diode bridge arms is the sum of the number of the auxiliary inductor interfaces LP and the number of the neutral point interfaces IOP of the clamping type three-level converter, and the neutral point of each power diode bridge arm is connected with the auxiliary inductor interfaces LP or the neutral point interfaces IOP of the clamping type three-level converter;
the neutral point of the power transistor bridge arm is connected with the DC capacitor neutral point interface COP;
the cathode of the power diode bridge arm is in short circuit with the positive end of the power transistor bridge arm, and the anode of the power diode bridge arm is in short circuit with the negative end of the power transistor bridge arm.
Has the advantages that: in a general method, switching is realized through a mechanical switch, which may increase stray inductance of a power loop of the system, thereby deteriorating electromagnetic compatibility of the system. By adopting the diode bridge arm and the power transistor bridge arm, the invention realizes the flexible switching of the working mode and the reduction of the electromagnetic interference of the circuit due to the unidirectional conductivity of the diode, the switching action of the power transistor and the high circuit integration of the diode and the power transistor, and the electromagnetic compatibility of the system can be optimized while the switching function is ensured due to the small stray inductance.
In order to achieve the above object, according to a second aspect of the present invention, there is provided a control system of a single-motor-driven single-phase grid-connected integrated drive charging circuit based on a clamped three-level converter as described in the first aspect, the system includes a controller, configured to send a command for operating in a motor-driven operating condition or a command for operating in a grid-connected power conversion operating condition to an operating mode switching module in the integrated drive charging circuit;
the working mode switching module is used for receiving a mode switching instruction from the controller and changing the internal switch state according to the instruction:
when an instruction of operating in a motor driving working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP, the direct-current capacitor neutral point interface COP and the neutral point interface IOP of the clamping type three-level converter are in short circuit;
when an instruction of operating in a grid-connected power conversion working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP is disconnected with the DC capacitor neutral point interface COP, the neutral point interface IOP of the clamp type three-level converter is disconnected with the DC capacitor neutral point interface COP, and at the moment, the auxiliary inductor interface LP is connected to one end of the single-phase power grid, and the neutral point interface IOP of the clamp type three-level converter is connected to the other end of the single-phase power grid.
Has the advantages that: the invention realizes the setting of the system working mode by the effective on-off control of the controller on the switch in the working mode switching module, thereby enabling hardware to effectively work in two different working conditions.
Preferably, the controller comprises a first control module corresponding to the working condition of the driving motor, and the first control module comprises an m-phase alternating current motor control unit, a clamping type three-level converter modulation unit, a neutral point current average value calculation unit of a clamping type three-level converter, a direct current filter capacitor neutral point voltage control loop and an auxiliary inductor current control loop;
the m-phase alternating current motor control unit is used for receiving a current detection signal of the alternating current motor and a rotating speed signal of the alternating current motor, adjusting the rotating speed and the current of the motor to enable the rotating speed and the torque of the motor to meet control requirements, outputting a control voltage command to the clamping type three-level converter, and outputting the control voltage command and a current detection value of the alternating current motor to a neutral point current average value calculation unit of the clamping type three-level converter;
the clamping type three-level converter modulation unit is used for receiving a control voltage command from the m-phase alternating current motor control unit, carrying out carrier modulation, outputting a driving signal of a power switch in the clamping type three-level converter and outputting the driving signal to a clamping type three-level bridge arm;
a neutral point current average value calculating unit of the clamping type three-level converter for receiving a k th beat control voltage command value v from the m-phase alternating current motor control unit*[k]And the current detection value i [ k ] of the K-th beat AC motor]Calculating to obtain kT through a voltage-current equation of the alternating current motor and a carrier modulation modesTo (k +1) TsNeutral point current average value i of three-level converter of clamp typenpAnd output to a neutral point voltage control loop of the DC filter capacitor, TsIs a switching cycle;
a DC filter capacitor neutral point voltage control loop for calculating the difference between two DC filter capacitor voltages, inputting the difference into the voltage regulator VR, and calculating to obtain a compensation current instruction i* compThe instruction and inpAdding to obtain an auxiliary inductor current instruction i* LAnd output to the auxiliary inductance current control loop;
auxiliary inductor current control loop for calculating i* LThe difference value with the actual inductive current is input into a current regulator CR, and an inductive voltage control signal U is obtained through calculationLTo U, to ULAnd comparing the processed signals with a triangular carrier after per unit processing to obtain driving signals of the two-level bridge arm unit, and outputting the driving signals to the auxiliary two-level bridge arm.
Has the advantages that: the invention calculates the average value of the midpoint current of the clamping type three-level converter, takes the average value as the sum of the feedforward quantity and the compensation current instruction output by the neutral point voltage control loop as the auxiliary inductive current instruction, and realizes the balance of the midpoint potential of the clamping type three-level converter under the motor driving working condition because the auxiliary inductive current control loop can have no static tracking instruction.
Preferably, the controller comprises a second control module corresponding to a grid-connected power conversion working condition, and the second control module comprises an alternating current motor rotor d-axis position angle judgment unit, an alternating current motor winding access power grid mode determination unit, a power grid voltage phase-locked loop unit, a grid-connected current control unit and a bridge arm modulation unit;
the device comprises an alternating current motor rotor d-axis position angle judging unit, a grid connection current control unit and a grid connection current control unit, wherein the alternating current motor rotor d-axis position angle judging unit is used for judging the alternating current motor rotor d-axis position angle and outputting the position angle to the alternating current motor winding access power grid mode determining unit and the grid connection current control unit;
the system comprises an alternating current motor winding access power grid mode determining unit, a grid-connected current control unit and a clamping type three-level converter, wherein the alternating current motor winding access power grid mode determining unit is used for selecting a switch corresponding to the midpoint of a certain phase bridge arm in the clamping type three-level converter to be conducted according to a d-axis position angle of a motor, so that the motor winding of the corresponding phase is connected with a single-phase power grid, meanwhile, the clamping type three-level bridge arms of other phases work in a two-level mode, and phase numbers of the alternating current motor winding access power grid are output to the grid-connected current control unit;
the grid voltage phase-locked loop unit is used for receiving a voltage detection signal from a grid voltage sensor, calculating to obtain an instantaneous phase and an amplitude of grid voltage and outputting the instantaneous phase and the amplitude to the grid-connected current control unit;
the grid-connected current control unit includes: the system comprises a grid-connected current instruction generation module, a d-axis current instruction generation module, a dq shafting lower current negative feedback calculation module, a proportion-multi-resonance current regulator, a power grid voltage feedforward calculation module and a coordinate inverse transformation module;
the grid-connected current instruction generating module is used for receiving grid voltage instantaneous phase and amplitude signals of the grid voltage phase-locked loop unit, receiving a grid-connected power instruction signal, obtaining a grid-connected current instruction according to the relation between power and voltage current, and outputting the grid-connected current instruction to the d-axis current instruction generating module;
the d-axis current instruction generation module is used for receiving a grid-connected current instruction, a motor position angle and a winding access phase number, calculating the d-axis current instruction according to the vector relation between the grid current and the d-axis current, and outputting the d-axis current instruction to the dq shafting lower current negative feedback calculation module;
the dq shafting lower current negative feedback calculation module is used for receiving a d-axis current instruction and a motor phase current detection value, setting the q-axis current instruction to be zero, firstly performing coordinate transformation on motor phase current to obtain d-axis current and q-axis current, subtracting the d-axis current and the q-axis current instruction to obtain an error term, and outputting the error term to the proportional-multi-resonant current regulator;
the proportion-multi-resonance current regulator is used for receiving the error terms, respectively executing the operation of the proportion regulator and the multi-resonance regulator, adding the error terms to obtain a feedback control output quantity, and outputting the feedback control output quantity to the power grid voltage feedforward calculation module;
the power grid voltage feedforward calculation module is used for receiving voltage detection signals of a power grid voltage sensor, motor position angles and winding access modes, calculating components of the power grid voltage on d and q axes from the voltage detection signals, respectively adding the components to feedback control output quantities of corresponding axes to obtain final voltage control output quantities, and outputting the final voltage control output quantities to the coordinate inverse transformation module;
the coordinate inverse transformation module is used for receiving the voltage control output quantity and the motor position angle, calculating to obtain a voltage output quantity under an m-phase coordinate system, and outputting the voltage output quantity to the bridge arm modulation unit;
the bridge arm modulation unit is used for receiving a winding access mode and voltage output quantity under an m-phase coordinate system, and firstly blocking an upper switch and a lower switch of a three-level bridge arm of the phase accessed to a power grid according to the winding access mode; then, the component of the phase which is connected into the power grid in the voltage output quantity is subjected to per-unit treatment, and then is compared with a triangular carrier to obtain a driving signal of the auxiliary two-level bridge arm, and the driving signal is output to the auxiliary two-level bridge arm; and after the components of other phases in the voltage output quantity are unified, the components are compared with the triangular carrier wave to obtain driving signals of upper and lower switches of a bridge arm of the corresponding phase in the three-level converter, and the driving signals are output to the clamping type three-level bridge arm.
Has the beneficial effects that: according to the invention, a proper motor phase winding is selected to be connected into a single-phase power grid and a circuit for controlling the motor phase winding according to the position of the d axis of the motor, and the motor torque is zero while high electric energy quality grid connection is realized due to the effective current regulation capacity of the proportion-multi-resonance regulator.
In order to achieve the above object, according to a third aspect of the present invention, there is provided a multi-motor driving three-phase grid-connected integrated driving charging circuit based on a clamped three-level converter, including X clamped three-level converters, two dc filter capacitors, Y auxiliary inductors, Y auxiliary two-level bridge arms, a working mode switching module, a dc power supply side electrical interface, a motor system ac side electrical interface, and a three-phase power grid interface;
each clamped three-level converter is composed of m clamped three-level bridge arms, and anodes Px of the clamped three-level bridge arms are in short circuit to form an anode P of the direct current power supply side electric interface; the negative electrodes Nx of the three-level bridge arms are in short circuit together to form a negative electrode N of the electric interface at the DC power supply side; the AC interface ACx of the three-level bridge arm is independently connected out to form an AC side electrical interface of the motor system together, and the AC side electrical interface is connected with the m-phase AC motor; neutral points Ox of the three-level bridge arms are connected together to form a neutral point O of the converter, wherein x is 1,2,3, m and m represent the number of phases of the alternating current motor;
the two direct current filter capacitors are connected in series, and a positive electrode interface CP, a negative electrode interface CN and a neutral point interface CO are led out; the positive electrode interface CP is connected to the positive electrode P of the electric interface on the DC power supply side; the negative electrode interface CN is connected to the negative electrode N of the electric interface at the DC power supply side;
the working mode switching module is provided with three interfaces, namely an auxiliary inductor interface LP, a direct-current capacitor neutral point interface COP and a clamping type three-level converter neutral point interface IOP; the auxiliary inductor interfaces LP are connected with one end of an auxiliary inductor, and the number of the LPs is Y; the direct-current capacitor neutral point interface COP is connected with the neutral point interface CO, and the number of COPs is 1; neutral point interfaces IOP of the clamping type three-level converter are connected with neutral points O, and the number of the IOP is X;
each auxiliary inductor is provided with two ports, one end of each auxiliary inductor is connected to a corresponding auxiliary inductor interface LP in the working mode switching module, and the other end of each auxiliary inductor is connected with an alternating current side interface ACa of a corresponding two-level bridge arm unit;
each auxiliary two-level bridge arm is provided with a positive electrode Pa, a negative electrode Na and an alternating current side interface ACa, and the positive electrode Pa is connected to a positive electrode P of the direct current power supply side electrical interface; the negative electrode Na is connected to the negative electrode N of the electrical interface at the DC power supply side; the alternating current side interface ACa is connected with one end of the corresponding auxiliary inductance unit;
under the three-phase grid-connected working condition, the electric wiring mode between the integrated drive charging circuit and the three-phase power grid is determined according to X, and the following two possibilities exist:
when X is more than or equal to 3, three phases of a three-phase power grid are respectively connected to neutral points of three clamping type three-level converters;
and when X is 2, two phases of the three-phase power grid are respectively connected to neutral points of the two clamping type three-level converters, and the other phase is connected to one end of one auxiliary inductor.
Has the advantages that: according to the invention, the plurality of clamping type three-level converters are adopted to connect the power grid and the plurality of motors, and due to the action of the switches corresponding to the zero levels of the clamping type three-level bridge arms, the connection of any phase winding of the motor with the power grid is realized, so that the zero torque of the motor during three-phase grid-connected charging is realized.
Preferably, the working mode switching module comprises a plurality of power diode bridge arms and a power transistor bridge arm;
the number of the power diode bridge arms is the sum of the number of the auxiliary inductor interfaces LP and the number of the neutral point interfaces IOP of the clamping type three-level converter, and the neutral point of each power diode bridge arm is connected with the auxiliary inductor interfaces LP or the neutral point interfaces IOP of the clamping type three-level converter;
the neutral point of the power transistor bridge arm is connected with the DC capacitor neutral point interface COP;
the cathode of the power diode bridge arm is in short circuit with the positive end of the power transistor bridge arm, and the anode of the power diode bridge arm is in short circuit with the negative end of the power transistor bridge arm.
Has the advantages that: by adopting the diode bridge arm and the power transistor bridge arm, the invention realizes the flexible switching of the working modes and the reduction of the electromagnetic interference of the circuit due to the unidirectional conductivity of the diode, the switching action of the power transistor and the high circuit integration of the diode and the power transistor.
In order to achieve the above object, according to a fourth aspect of the present invention, there is provided a control system of a clamped three-level converter-based multi-motor-driven three-phase grid-connected integrated drive charging circuit according to the third aspect, the system includes a controller, configured to send a command for operating in a motor-driven operating condition or a command for operating in a grid-connected power conversion operating condition to an operating mode switching module of the integrated drive charging circuit;
the working mode switching module is used for receiving a mode switching instruction from the controller and changing the internal switch state according to the instruction:
when an instruction of operating in a motor driving working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP, the direct-current capacitor neutral point interface COP and the neutral point interface IOP of the clamping type three-level converter are in short circuit;
when an instruction of operating in a grid-connected power conversion working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP is disconnected with the DC capacitor neutral point interface COP, the neutral point interface IOP of the clamp type three-level converter is disconnected with the DC capacitor neutral point interface COP, and at the moment, the three-phase power grid is connected with Y auxiliary inductors and X clamp type three-level converter neutral points according to the electric wiring mode between the integrated drive charging circuit and the three-phase power grid.
Has the advantages that: the invention realizes the setting of the system working mode by the effective on-off control of the controller on the switch in the working mode switching module, thereby enabling hardware to effectively work in two different working conditions.
Preferably, the controller comprises a third control module corresponding to the working condition of the driving motor, and the third control module comprises X m-phase alternating current motor control units, X clamping type three-level converter modulation units, X neutral point current average value calculation units of clamping type three-level converters, a direct current filter capacitor neutral point voltage control loop and Y auxiliary inductor current control loops;
each m-phase alternating current motor control unit is used for receiving a current detection signal of a corresponding alternating current motor and a rotating speed signal of the alternating current motor, completing the regulation of the rotating speed and the current of the corresponding motor, enabling the rotating speed and the torque of the motor to meet control requirements, outputting a control voltage command to a corresponding clamping type three-level converter, and outputting the control voltage command and a current detection value of the alternating current motor to a neutral point current average value calculation unit of the corresponding clamping type three-level converter;
each clamping type three-level converter modulation unit is used for receiving a control voltage command from the corresponding m-phase alternating current motor control unit, carrying out carrier modulation, outputting a driving signal of a power switch in the corresponding clamping type three-level converter and outputting the driving signal to a clamping type three-level bridge arm;
a neutral point current average value calculating unit of each clamping type three-level converter for receiving the kth beat control voltage command value v from the corresponding m-phase alternating current motor control unit*[k]And the current detection value i [ k ] of the K-th AC motor]Calculating to obtain kT through a voltage-current equation of the alternating current motor and a carrier modulation modesTo (k +1) TsNeutral point current average value i of corresponding clamp type three-level converternp，TsThe switching period is the switching period, and the switching period is output to a neutral point voltage control loop of the direct current filter capacitor;
a neutral point voltage control loop of the DC filter capacitor for calculating the difference between the voltages of the two DC filter capacitors, inputting the difference into the voltage regulator VR, and calculating to obtain a compensation current command i* compThe instruction and X inpAdding to obtain an auxiliary inductor current instruction i* L，i* LDividing the current by Y and then respectively outputting the current to Y auxiliary inductance current control loops;
each auxiliary inductor current control loop for calculating i* LThe difference between the/Y and the actual inductor current is input to a current regulator CR, and an inductor voltage control signal U is calculatedLTo U, to ULAnd comparing the processed signals with a triangular carrier after per unit processing to obtain driving signals of the corresponding two-level bridge arm unit, and outputting the driving signals to the corresponding auxiliary two-level bridge arm.
Has the advantages that: according to the invention, the average value of the midpoint current of the clamping type three-level converter is calculated, the average value is used as the sum of the feedforward quantity and the compensation current instruction output by the neutral point voltage control loop and is used as the auxiliary inductive current instruction, and the auxiliary inductive current control loop can track the instruction without static error, so that the balance of the midpoint potential of the clamping type three-level converter under the motor driving working condition is realized.
Preferably, the controller includes a fourth control module corresponding to an operating condition of the drive motor, the fourth control module including: the system comprises X alternating current motor rotor d-axis position angle judgment units, X alternating current motor winding access power grid mode determination units, a three-phase power grid voltage phase-locked loop unit, a grid-connected current control unit and X bridge arm modulation units;
each alternating current motor rotor d axis position angle judging unit is used for judging a corresponding alternating current motor rotor d axis position angle and outputting the position angle to a corresponding alternating current motor winding access power grid mode determining unit and a grid-connected current control unit;
each alternating current motor winding is connected to a power grid mode determining unit and used for selecting a switch corresponding to a neutral point of a certain phase bridge arm in a corresponding clamping type three-level converter according to a d-axis position angle of a corresponding alternating current motor to be conducted, so that the motor winding of the corresponding phase is connected with one phase in a three-phase power grid, meanwhile, the clamping type three-level bridge arms of other phases work in a two-level mode, and the motor phase number of the corresponding alternating current motor winding connected to the three-phase power grid is output to a grid-connected current control unit;
the grid voltage phase-locked loop unit is used for receiving a voltage detection signal from the three-phase grid voltage sensor, calculating to obtain an instantaneous phase and an amplitude of the three-phase grid voltage, and outputting the instantaneous phase and the amplitude to the grid-connected current control unit;
the grid-connected current control unit includes: the system comprises Z grid-connected current instruction generation modules, Z d-axis current instruction generation modules, Z dq-axis lower current negative feedback calculation modules, Z proportion-multi-resonance current regulators, 3-Z auxiliary inductance current control modules, 3 grid voltage feedforward calculation modules, Z coordinate inverse transformation modules and 3 bridge arm modulation units, wherein Z is 2 or 3;
each grid-connected current instruction generation module is used for receiving the grid voltage instantaneous phase and amplitude signals of the three-phase grid voltage phase-locked loop unit, receiving the grid-connected power instruction signals, obtaining a grid-connected current instruction according to the relation between power and voltage current, and outputting the grid-connected current instruction to the corresponding d-axis current instruction generation module;
each d-axis current instruction generation module is used for receiving a corresponding grid-connected current instruction, a motor position angle and a winding access phase number, calculating the d-axis current instruction according to the vector relation between the grid current of the corresponding phase and the corresponding d-axis current to obtain the d-axis current instruction, and outputting the d-axis current instruction to the corresponding dq-axis lower current negative feedback calculation module;
each dq shafting lower current negative feedback calculation module is used for receiving a corresponding d-axis current instruction and a corresponding motor phase current detection value, setting the q-axis current instruction to be zero, firstly performing coordinate transformation on motor phase current to obtain d-axis current and q-axis current, subtracting the d-axis current and the q-axis current instruction to obtain an error term, and outputting the error term to a corresponding proportional-multi-resonant current regulator;
each proportion-multi-resonance current regulator is used for receiving the corresponding error term, respectively executing the operation of the proportion regulator and the multi-resonance regulator, adding the operation results to obtain feedback control output quantity, and outputting the feedback control output quantity to the corresponding power grid voltage feedforward calculation module;
each auxiliary inductance current control module is used for receiving a grid-connected power instruction signal and a detected value of auxiliary inductance current, calculating an instruction value of the auxiliary inductance current according to the phase number of the auxiliary inductance connected to a three-phase power grid, subtracting the detected value of the auxiliary inductance current from the instruction value of the auxiliary inductance current to obtain an error term, performing proportional-multi-resonance adjustment calculation on the error term to obtain an auxiliary inductance current control quantity, and outputting the control quantity to a power grid voltage feedforward calculation module;
the 3 power grid voltage feedforward calculation modules are divided into Z dq-axis voltage feedforward calculation units and (3-Z) voltage feedforward calculation units of auxiliary inductors; each dq-axis voltage feedforward calculation module is used for receiving voltage detection signals of the corresponding power grid voltage sensor, corresponding motor position angles and winding access modes, calculating components of the power grid voltage in d and q axes according to the voltage detection signals, adding the components to feedback control output quantities of the corresponding axes respectively to obtain final dq-axis voltage control output quantities, and outputting the final dq-axis voltage control output quantities to the corresponding coordinate inverse transformation modules;
the voltage feedforward calculation unit of each auxiliary inductor is used for receiving a voltage detection signal of a corresponding phase power grid voltage sensor, adding the signal to a corresponding auxiliary inductor current control quantity to obtain a final auxiliary inductor control output quantity, and outputting the final auxiliary inductor control output quantity to the bridge arm modulation unit; each coordinate inverse transformation module is used for receiving the corresponding dq axis voltage control output quantity and the motor position angle, calculating to obtain a voltage output quantity under an m-phase coordinate system, and outputting the voltage output quantity to the corresponding Z bridge arm modulation units;
the Z bridge arm modulation units are connected with the coordinate inverse transformation module and used for receiving a mode corresponding to the access of the alternating current motor winding and the voltage output quantity under an m-phase coordinate system, and the upper and lower switches of the three-level bridge arm of the phase accessed to the power grid are blocked according to the mode of the access of the winding; after the components of other motor phases which are not connected with a three-phase power grid in the voltage output quantity are unified, the components are compared with a triangular carrier to obtain driving signals of upper and lower switches of a bridge arm of a corresponding phase in the three-level converter, and the driving signals are output to a clamping type three-level bridge arm;
and the rest (3-Z) bridge arm modulation units are used for receiving the corresponding auxiliary inductance control output quantity, comparing the auxiliary inductance control output quantity with the triangular carrier to obtain a driving signal of the corresponding auxiliary two-level bridge arm, and outputting the driving signal to the auxiliary two-level bridge arm.
Has the advantages that: according to the invention, a proper motor phase winding is selected to be connected into a single-phase power grid and a circuit for controlling the motor phase winding according to the position of the d axis of the motor, and the motor torque is zero while high electric energy quality grid connection is realized due to the effective current regulation capacity of the proportion-multi-resonance regulator; on the other hand, the invention adopts a plurality of clamping type three-level converters to connect the three-phase power grid, the motor and the battery, thereby realizing the quick charging of the battery.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) in order to solve the problems that when an existing multiplexing motor controller is used as a vehicle-mounted charger, a motor can generate torque, and zero torque is required to be realized independent of a position angle of a rotor of the motor, the invention provides a method for selecting a mode of connecting a phase winding of the motor to a power grid by adopting a three-level converter and changing a switching mode of a neutral point bridge arm of the three-level converter, wherein the phase connected to the power grid can be flexibly selected and changed through the neutral point bridge arm in the converter, a current control strategy is combined to ensure that the integrated charger can not generate the motor torque and the loss is lowest when the integrated charger is connected to the power grid, and the zero torque is realized independent of the position angle of the rotor and the loss is lowest.
(2) In order to solve the problem of how to balance the neutral point potential of the three-level converter and the problem of independence of a modulation mode, a modulation coefficient, a load power factor and the like, the current flowing into a neutral point of a capacitor of the three-level converter is reversely compensated by controlling the current on an auxiliary inductor through modulating an auxiliary bridge arm, and finally the purpose of stabilizing the neutral point potential is achieved. Under the motor driving condition, neutral point potential balance of the three-level converter is generally realized by optimizing a modulation mode, but the mode is related to load power factor and modulation factor. The effect of neutral point potential balance is general because the modulation factor and power factor of the inverter vary over a wide range during motor control. According to the invention, an additional bridge arm and an additional inductor are added, on one hand, the additional elements can be connected into a power grid during grid connection, so that the system has a full-bridge property, the quality of grid-connected electric energy can be improved, on the other hand, under the working condition of motor driving, the auxiliary inductor can provide current to reversely compensate the current flowing into a neutral point of a capacitor of the three-level converter, and finally the purpose of stabilizing the potential of the neutral point is achieved.
Drawings
Fig. 1 is a hardware system block diagram of a single-motor-driven single-phase grid-connected integrated drive charging circuit based on a clamping type three-level converter according to the present invention;
FIG. 2 is a main circuit topology based on a T-type three-level converter provided by the invention;
FIG. 3 is a main circuit topology based on a neutral point clamped three-level converter provided by the present invention;
FIG. 4 is a block diagram of a motor drive control algorithm provided by the present invention;
FIG. 5 is a block diagram of a midpoint voltage fluctuation compensation control algorithm provided by the present invention;
FIG. 6 is a block diagram of a grid-connected control algorithm provided by the present invention;
FIG. 7 is a block diagram of a multi-module extended application hardware system provided by the present invention;
FIG. 8 is a block diagram of a control system for a multi-module extended application system provided by the present invention;
fig. 9 is a circuit diagram of an operation mode switching switch based on a power semiconductor device according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the respective embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, the present invention provides a single-motor driven single-phase grid-connected integrated driving charging circuit based on a clamped three-level converter, which includes: the device comprises a plurality of clamping type three-level bridge arms, two direct current filter capacitors, an auxiliary two-level bridge arm, an auxiliary inductor, a working mode selector switch, a direct current side electric interface, an alternating current side electric interface and a single-phase power grid interface.
The clamping type three-level bridge arm can be other types of three-level bridge arms except flying capacitor three-level bridge arms and comprises an upper bridge arm switch, a lower bridge arm switch and a midpoint switch, wherein the upper bridge arm switch is connected to the positive end of a direct-current bus, the lower bridge arm switch is connected to the negative end of the direct-current bus, and the midpoint switches of the bridge arms are connected together to form a midpoint of the three-level converter. The number of the three-level bridge arm units is determined according to the phase number m of the motor.
The direct current filter capacitor can be an electrolytic capacitor or a common membrane capacitor in an electric automobile and comprises an upper sub capacitor and a lower sub capacitor, a neutral point of each sub capacitor is connected out to serve as a neutral point interface, and the direct current support capacitor is used for stabilizing direct current side voltage and absorbing load pulse current.
The auxiliary two-level bridge arm is a common voltage type two-level bridge arm, an upper bridge arm switch is connected to a direct current positive pole end, and a lower bridge arm switch is connected to a direct current negative pole end; the size of the auxiliary inductor is matched with the motor inductor and is used for providing a midpoint compensation current and serving as a part of a grid-connected filter inductor.
The working mode change-over switch is internally composed of an electronic switch or a mechanical switch and is provided with three ports, one port is connected to a neutral point of the direct current supporting capacitor, the other port is connected to the auxiliary inductor, and the third port is connected to the midpoint of the three-level converter; the working mode selector switch changes the connection relation of the internal switch according to the working mode instruction; when the motor works under the motor driving working condition, the auxiliary inductor is connected to the neutral point of the direct current support capacitor, and the middle point of the three-level converter is also connected to the neutral point of the direct current support capacitor; when the three-level converter works under a grid-connected working condition, the auxiliary inductor is connected to one end of a power grid, the middle point of the three-level converter is connected to the other end of the power grid, and the neutral point of the direct-current support capacitor is disconnected with the port.
The single-phase power grid interface consists of a power grid charging interface and a power grid voltage sensor, and the power grid charging interface is used for accessing a single-phase power grid under the grid-connected working condition; the grid voltage sensor is used for converting the high-voltage grid voltage into a low-voltage detection signal and transmitting the low-voltage detection signal to the controller.
The three-phase alternating current motor is an electric automobile driving motor, such as a permanent magnet synchronous motor and an asynchronous motor.
The controller receives a motor position signal, a motor stator winding current signal, an auxiliary inductance current signal and a power grid voltage sensor signal, then executes a motor driving algorithm or a grid-connected control algorithm, and finally outputs a driving signal of a three-level converter power switch and a driving signal of an auxiliary bridge arm switch; and meanwhile, the controller sends out a switch signal according to the working mode to control the on-off state of a switch in the working mode switching switch device.
To further illustrate the hardware structure of the present invention, embodiments of the present invention provide a motor driving-grid-connected power conversion integration technology based on a T-type three-level converter and a midpoint clamping three-level converter, as shown in fig. 2 and fig. 3, respectively.
In fig. 2, the midpoint switch of the three-level bridge arm is composed of two bidirectional voltage switches connected in reverse series, while in fig. 3, the midpoint switch is composed of two switches in the middle and two clamping diodes; in fig. 3, the top switch is the upper switch of the bridge arm and is connected with the positive direct current pole, and the bottom switch is the lower switch of the bridge arm and is connected with the negative direct current pole; the ac side of the three-level inverter in fig. 2 and 3 is connected to a three-phase ac motor.
The circuits shown in fig. 2 and 3 each include an auxiliary two-level bridge arm and an auxiliary inductor for balancing the midpoint voltage; also included is an operating mode switch having three ports: the ports (P1, P2) connected with the auxiliary inductor and the midpoint of the three-level converter are led out from the midpoint after the two diodes are connected in series, and the port (P3) connected with the neutral point of the direct current support capacitor is led out from the midpoint after the two transistors are connected in series; the grid voltage interface is connected to P1, P2, and includes grid voltage sensor and voltage interface.
When the circuit works in a motor driving mode, two power transistors of the working mode selector switch are switched on, and when the circuit works in a grid-connected mode, the two power transistors are switched off; in a motor driving mode, the three-level converter works in a conventional three-level modulation mode, namely all switching tubes in the converter work in a high-frequency switching state; in a grid-connected mode, firstly, the midpoint switch of the bridge arm of the phase is determined to be always on and the midpoint switches of the bridge arms of the other two phases are always off according to the position of the motor, specifically:
C1. when the position of the d axis of the motor is positioned at (-30) - (-150) - (-210) - (-150) - (-210) -)), the midpoint switch of the A-phase bridge arm is always on, and the midpoint switch of the B-phase bridge arm and the C-phase bridge arm are always off;
C2. when the position of the d axis of the motor is positioned between 90 degrees, 150 degrees or-90 degrees and-30 degrees, the midpoint switch of the B phase bridge arm is always on, and the midpoint switch of the A phase bridge arm and the C phase bridge arm are always off;
C3. when the d-axis position of the motor is located at other positions, the midpoint switch of the C-phase bridge arm is always on, and the midpoint switches of the A-phase bridge arm and the B-phase bridge arm are always off.
Further, other switches of the bridge arm connected to the power grid are always turned off; the other switch working modes of the other two-phase bridge arm which is not connected into the power grid are as follows: in fig. 2, the upper and lower power switching tubes of the bridge arm work in a complementary manner; in fig. 3, the upper two switches and the lower two switches of the bridge arm are synchronous switches, and they are complementary and need to add a certain dead time.
The control strategy of the system is introduced next, which comprises a control algorithm under the motor driving working condition and a control algorithm under the grid-connected working condition, when the system works actually, the control algorithm writes codes into the controller, and the controller timely selects the algorithm to execute and complete the control task.
FIG. 4 shows a block diagram of a control algorithm under a motor driving condition, which includes receiving an upper layer torque and rotation speed instruction, a motor torque and rotation speed control algorithm, a three-level converter modulation strategy, midpoint current prediction, a midpoint voltage control loop, an auxiliary inductor current control loop, and auxiliary bridge arm modulation; the motor torque and rotating speed control algorithm is a vector control algorithm of a conventional permanent magnet motor or an asynchronous motor, and the modulation strategy of the three-level converter is also conventional three-level space vector modulation or carrier wave laminated modulation.
FIG. 5 is a block diagram of a midpoint current prediction, a midpoint voltage control loop, and an auxiliary inductor current control loop; the midpoint current prediction link is used for predicting the current (taking the midpoint flowing into the three-level converter as positive) of the midpoint of the three-level converter, and the input of the midpoint current prediction link is the actually measured three-phase current of the motor stator winding and the middle vector action time T obtained by the modulation module of the three-level converterMSum small vector action time TSThe output is the low frequency component of the midpoint current, and one example of the calculation is:
Figure BDA0002909072070000171
wherein D isposIs the small vector with positive midpoint current in the selected small vectors acts on the time TSZhong ZhiThe ratio of the component (A) to the component (B).
The midpoint voltage control loop collects the difference delta u between the lower capacitor voltage and the upper capacitor voltagec＝uc2-uc1Then AND instruction
Figure BDA0002909072070000172
And comparing to obtain an error quantity, inputting the error quantity into a voltage regulator AUR to calculate to obtain a midpoint voltage compensation current, wherein the AUR is a proportional-multiresonant regulator and has the following transfer function:
Figure BDA0002909072070000173
wherein k ispAnd kriThe setting method adopts an engineering PID parameter adjusting method for the proportion and the resonance coefficient of the AUR regulator; omegagIs the angular frequency of the grid voltage.
AUR calculates to obtain the sum of midpoint voltage compensation current and midpoint current low-frequency component to obtain auxiliary inductor current instruction
Figure BDA0002909072070000181
Instruction and actual inductor current instruction iLMaking a difference to obtain an inductive current error quantity, inputting the inductive current error quantity into a current regulator ACR to calculate to obtain an auxiliary bridge arm modulation voltage, wherein the ACR is a proportional-multi-resonant regulator, and the transfer function of the proportional-multi-resonant regulator is the same as that of AUR, but the proportion and the resonance coefficient are different; and the modulation wave is compared with the high-frequency triangular carrier wave to obtain a driving signal of the auxiliary bridge arm.
Fig. 6 shows a block diagram of a control system under a grid-connected condition, which includes a grid voltage phase-locked loop, d-axis position acquisition and winding access mode determination logic, dq-axis current instruction generation logic, a dq-axis current controller, and bridge arm drive signal generation logic.
The grid voltage phase-locked loop is a conventional single-phase voltage phase-locked loop based on a generalized second-order integrator, and the input of the grid voltage phase-locked loop is an instantaneous detection signal of the grid voltage and the output of the grid voltage phase-locked loop is an instantaneous phase of the grid voltage.
The d-axis position acquisition can be obtained by identifying the d-axis position of the motor by adopting a high-frequency signal injection method, and can also be obtained by an absolute type coding device.
The logic for judging the winding access mode is as follows: when the d-axis position of the motor is between-30 degrees, 30 degrees or 150 degrees, 210 degrees, the A-phase winding is connected to the power grid; when the d-axis position of the motor is between [90 degrees, 150 degrees ] or [ -90 degrees, -30 degrees ], the B-phase winding is connected to the power grid; otherwise, the C-phase winding is connected to the power grid.
The d-axis current instruction generation logic is that the grid-connected current instruction is received and the motor position theta obtained by the motor position judgment unitrAnd the mode of winding access is instructed by the grid current according to the vector relation between the grid current and the d-axis current
Figure BDA0002909072070000182
D-axis current instruction is obtained through calculation
Figure BDA0002909072070000183
The calculation is as follows:
when the phase A is connected to the power grid:
Figure BDA0002909072070000184
when the B phase is connected to the power grid:
Figure BDA0002909072070000185
when the C phase is connected to the power grid:
Figure BDA0002909072070000186
the d-axis current command and the q-axis current command (equal to 0) are input to the dq-axis current controller. The dq-axis current controller receives a motor phase current detection value, firstly, coordinate transformation is carried out on motor phase current to obtain d-axis current and q-axis current, and the d-axis current and the q-axis current are subtracted from d-axis current and q-axis current instructions to obtain an error item; the proportional-multivibrator of the dq-axis current controller receives the error term and executesCalculating proportion and multiple resonance regulators to obtain feedback control output, wherein the multiple resonance regulators are composed of 5 quasi-resonance regulators connected in parallel, and the resonance frequency is fg,2fg,3fg,5fg,7fg(fgGrid frequency, 50 Hz); the dq-axis current controller also comprises a power grid voltage feedforward calculation module, a feedback control output value calculation module and a feedback control output value calculation module, wherein the power grid voltage feedforward calculation module is used for receiving an instantaneous detection value of the power grid voltage, a motor position and a winding access mode, calculating the action quantities of the power grid voltage on d and q axes according to the instantaneous detection value, and then adding the action quantities to the feedback control output quantities of the corresponding axes respectively to obtain a final voltage control output quantity; the inverse coordinate transformation receives the voltage control output quantity and the motor position, and the voltage output quantity u under the phase coordinate system is obtained through calculationabc。
Finally, according to uabcAnd determining a driving signal of a bridge arm by a winding access mode: firstly, blocking an upper switch and a lower switch of a three-level bridge arm of the phase accessed to a power grid according to a mode of winding access; then, the component of the phase connected to the power grid in the voltage output quantity is unified, and then the component is compared with a triangular carrier wave to obtain a driving signal for assisting a two-level bridge arm; and after the components of other phases in the voltage output quantity are unified per unit, the components are compared with the triangular carrier wave to obtain driving signals of upper and lower switches of a bridge arm of the corresponding phase in the three-level converter.
Further, according to a final aspect of the present invention, the embodiment provides an example of an extended application of a multi-module system, wherein the multi-module system comprises a plurality of driving motors and controls based on three-level converters, and the multi-module system can be connected to a three-phase power grid to complete quick charging of a battery.
Fig. 7 is a block diagram of a hardware system for multi-module extended application according to an embodiment of the present invention, which includes an electric drive system formed by multiple sets of circuit structures and multiple ac motors, and an electrical connection mode between the electric drive system and a three-phase power grid.
The multi-set circuit structure comprises x sets of three-phase clamping type three-level converters and interfaces thereof (x is more than or equal to 2), and y auxiliary two-level bridge arms and auxiliary inductors (y is more than or equal to 1); correspondingly, the number of equivalent switches in the working mode change-over switch is x + y; the circuit structures share a direct current capacitor; the middle points of the x three-phase clamping type three-level converter are connected with corresponding points in the working mode selector switch, and the middle points are in short circuit through switches instead of direct connection; one end of each of the y auxiliary inductors is connected with a corresponding point in the working mode selector switch, and the ports are in short circuit through the switch instead of being directly connected; the other end of each y auxiliary inductor is connected with the corresponding auxiliary two-level bridge arm.
The electric drive system is composed of a plurality of sets of circuit structures and x three-phase alternating current motors, and alternating current interfaces of three-level converters in the circuit structures are connected to corresponding alternating current motor windings to drive the motors.
Under the three-phase operating mode that is incorporated into the power networks, the electric wiring mode between electric drive system and three-phase electric network is decided according to x and y quantity, has following two kinds of probably:
when x is larger than or equal to 3, three phases of a three-phase power grid are respectively connected to the middle points of the three clamping type three-level converters;
and when x is 2, two phases of the three-phase power grid are respectively connected to the middle points of the two sets of clamping type three-level converters, and the other phase is connected to one end of one auxiliary inductor.
On the other hand, aiming at multi-module extended application, the embodiment of the invention also provides a control strategy of an electric drive system and a control strategy of the system under a grid-connected working condition, which specifically comprises the following steps:
under the working condition of driving the motor, on one hand, a motor control algorithm and a modulation algorithm of the clamping type three-level converter are executed to control the rotating speed and the torque of the motor; on the other hand, the midpoint current low-frequency components of each set of three-phase clamping type three-level converter are predicted and integrated to obtain the total midpoint current low-frequency component; on the last hand, the low-frequency component of the total midpoint current is evenly distributed into current commands of y auxiliary inductors, so that the current stress and the loss on each auxiliary inductor are ensured to be balanced while the midpoint current is compensated;
under the grid-connected working condition, the corresponding bridge arm is controlled according to the electric connection mode between the electric drive system and the three-phase power grid, a control system block diagram is given in fig. 8, and the specific steps are as follows:
s1, obtaining a real-time position of a d shaft of a motor by adopting high-frequency signal injection or according to an absolute position signal of a permanent magnet motor, and selecting a winding access power grid mode according to the real-time position of the d shaft of the motor;
s2, blocking upper and lower switch tubes of a three-level bridge arm corresponding to a phase winding accessed to a power grid;
s3, determining current instructions of windings or inductors connected with other bridge arms: for the motor winding, calculating a phase winding current instruction according to the grid current, the d-axis current of the motor and the vector relation among the axes of the phase windings to obtain the phase winding current instruction; for the auxiliary inductor, an inductor current instruction is a corresponding power grid phase current instruction;
s4, calculating the error between the current instruction of the motor winding or the inductor and the actual current, inputting the error into the proportional-multiresonant regulator, and calculating to obtain the output voltage of the bridge arm; the multi-resonance regulator is composed of 5 resonance regulators with resonance frequency of fg,2fg,3fg,5fg,7fg(fgGrid frequency, 50 Hz);
s5, obtaining the voltages of all the action bridge arms, solving the maximum value and the minimum value, adding the maximum value and the minimum value, multiplying the sum by-0.5 to obtain a zero sequence voltage, and adding the zero sequence voltage to the voltages of all the action bridge arms to obtain bridge arm modulation voltages;
and S6, dividing the modulation voltage of all the action bridge arms by half of the direct-current bus voltage to obtain bridge arm modulation waves, and finally comparing the modulation waves with high-frequency triangular carriers to obtain driving signals of the upper and lower tubes of the corresponding bridge arms.
In a multi-module expansion application, the operation mode switch may also adopt a circuit structure based on power electronic devices, and fig. 9 shows an embodiment including a plurality of power diodes and two power transistors, and their electrical connection relationships.
The number of power diodes is twice the number of external access points, i.e. each access point will correspond to two power diodes; the power transistor may be a power BJT, a power MOSFET, an IGBT, or a SiC power device.
The electrical connection relationship of the power diode and the power transistor is as follows: two diodes corresponding to each access point are connected in series, namely the cathode of one diode is connected to the anode of the other diode, the connection point is led out to form an external access point, and the rest cathode and anode are connected with the cathode and anode of the corresponding unit of the other access point; the two power transistors are connected in series to form a structure similar to a two-level bridge arm, the middle point of the two power transistors is connected with the neutral point of the bus capacitor, the positive end of the bridge arm is connected with the cathode of the diode unit, and the negative end of the bridge arm is connected with the anode of the diode unit.
The work mode switch based on the power semiconductor device can reduce the cost and the volume of the system, and simultaneously can reduce the power loop area of the system so as to reduce EMI.
It will be understood by those skilled in the art that the foregoing is only an exemplary embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, since various modifications, substitutions and improvements within the spirit and scope of the invention are possible and within the scope of the appended claims.

Claims (6)

1. A control system of a single-motor-driven single-phase grid-connected integrated drive charging circuit based on a clamping type three-level converter is characterized by comprising a controller, wherein the controller is used for sending an instruction of operating in a motor driving working condition or an instruction of operating in a grid-connected power conversion working condition to a working mode switching module in the integrated drive charging circuit;
the working mode switching module is used for receiving a mode switching instruction from the controller and changing the internal switch state according to the instruction:
when an instruction of operating in a motor driving working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP, the direct-current capacitor neutral point interface COP and the neutral point interface IOP of the clamping type three-level converter are in short circuit;
when an instruction of operating in a grid-connected power conversion working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP is disconnected with the DC capacitor neutral point interface COP, the neutral point interface IOP of the clamp type three-level converter is disconnected with the DC capacitor neutral point interface COP, and at the moment, the auxiliary inductor interface LP is connected to one end of a single-phase power grid, and the neutral point interface IOP of the clamp type three-level converter is connected to the other end of the single-phase power grid;
the controller comprises a first control module corresponding to the working condition of the driving motor, wherein the first control module comprises an m-phase alternating current motor control unit, a clamping type three-level converter modulation unit, a neutral point current average value calculation unit of a clamping type three-level converter, a direct current filter capacitor neutral point voltage control loop and an auxiliary inductance current control loop;
the m-phase alternating current motor control unit is used for receiving a current detection signal of the alternating current motor and a rotating speed signal of the alternating current motor, adjusting the rotating speed and the current of the motor to enable the rotating speed and the torque of the motor to meet control requirements, outputting a control voltage command to the clamping type three-level converter, and outputting the control voltage command and a current detection value of the alternating current motor to a neutral point current average value calculation unit of the clamping type three-level converter;
the clamping type three-level converter modulation unit is used for receiving a control voltage command from the m-phase alternating current motor control unit, carrying out carrier modulation, outputting a driving signal of a power switch in the clamping type three-level converter and outputting the driving signal to a clamping type three-level bridge arm;
a neutral point current average value calculating unit of the clamping type three-level converter for receiving a k th beat control voltage command value v from the m-phase alternating current motor control unit*[k]And the current detection value i [ k ] of the K-th beat AC motor]Calculating to obtain kT through a voltage-current equation of the alternating current motor and a carrier modulation modesTo (k +1) TsNeutral point current average value i of clamp type three-level converter in betweennpAnd output to a neutral point voltage control loop, T, of the DC filter capacitorsIs a switching cycle;
a DC filter capacitor neutral point voltage control loop for calculating the difference between the voltages of the two DC filter capacitors,inputting the difference value into a voltage regulator VR, and calculating to obtain a compensation current instruction i* compThe instruction and inpAdding to obtain an auxiliary inductor current instruction i* LAnd output to the auxiliary inductance current control loop;
auxiliary inductor current control loop for calculating i* LThe difference value with the actual inductive current is input into a current regulator CR, and an inductive voltage control signal U is obtained through calculationLTo U, to ULPerforming per unit processing, comparing the per unit processing with a triangular carrier to obtain a driving signal of the two-level bridge arm unit, and outputting the driving signal to the auxiliary two-level bridge arm;
the single-motor-driven single-phase grid-connected integrated drive charging circuit based on the clamping type three-level converter comprises: the device comprises a clamping type three-level converter, two direct current filter capacitors, an auxiliary inductor, an auxiliary two-level bridge arm, a working mode switching module, a direct current power supply side electric interface, a motor system alternating current side electric interface and a single-phase power grid interface;
the clamped three-level converter is composed of m clamped three-level bridge arms, and anodes Px of the clamped three-level bridge arms are in short circuit to form an anode P of an electric interface at the DC power supply side; the negative electrodes Nx of the three-level bridge arms are in short circuit together to form a negative electrode N of the electric interface at the direct current power supply side; the AC interface ACx of the three-level bridge arm is independently connected out to form an AC side electrical interface of the motor system together, and the AC side electrical interface is connected with the m-phase AC motor; neutral points Ox of the three-level bridge arms are connected together to form a neutral point O of the clamped three-level converter, x is 1,2,3 …, and m represents the phase number of the alternating current motor;
the two direct current filter capacitors are connected in series, and a positive electrode interface CP, a negative electrode interface CN and a neutral point interface CO are led out; the positive electrode interface CP is connected to the positive electrode P of the electric interface on the direct current power supply side; the negative electrode interface CN is connected to the negative electrode N of the electric interface at the DC power supply side;
the working mode switching module is provided with three interfaces, namely an auxiliary inductor interface LP, a direct current capacitor neutral point interface COP and a clamping type three-level converter neutral point interface IOP; the auxiliary inductor interface LP is connected with one end of an auxiliary inductor; the direct-current capacitor neutral point interface COP is connected with the neutral point interface CO; the neutral point interface IOP of the clamping type three-level converter is connected with a neutral point O;
the auxiliary inductor is provided with two ports, one end of the auxiliary inductor is connected to an auxiliary inductor interface LP of the working mode switching module, and the other end of the auxiliary inductor is connected with an alternating current side interface ACa of the two-level bridge arm unit;
the auxiliary two-level bridge arm is provided with a positive electrode Pa, a negative electrode Na and an alternating current side interface ACa, and the positive electrode Pa is connected to a positive electrode P of an electric interface on the direct current power supply side; the negative electrode Na is connected to the negative electrode N of the electrical interface at the DC power supply side; the alternating current side interface ACa is connected with one end of the auxiliary inductance unit;
the neutral point interface IOP and the auxiliary inductor interface LP of the clamping type three-level converter jointly form a single-phase power grid interface, and a power grid voltage sensor is arranged in the single-phase power grid interface and used for detecting the voltage of a power grid.
2. The control system of claim 1, wherein the controller comprises a second control module corresponding to a grid-connected power conversion working condition, and the second control module comprises an alternating current motor rotor d-axis position angle judging unit, an alternating current motor winding grid-connected mode determining unit, a grid voltage phase-locked loop unit, a grid-connected current control unit and a bridge arm modulation unit;
the device comprises an alternating current motor rotor d-axis position angle judging unit, a grid connection current control unit and a grid connection current control unit, wherein the alternating current motor rotor d-axis position angle judging unit is used for judging the alternating current motor rotor d-axis position angle and outputting the position angle to the alternating current motor winding access power grid mode determining unit and the grid connection current control unit;
the system comprises an alternating current motor winding access power grid mode determining unit, a grid-connected current control unit and a clamping type three-level converter, wherein the alternating current motor winding access power grid mode determining unit is used for selecting a switch corresponding to the midpoint of a certain phase bridge arm in the clamping type three-level converter to be conducted according to a d-axis position angle of a motor, so that the motor winding of the corresponding phase is connected with a single-phase power grid, meanwhile, the clamping type three-level bridge arms of other phases work in a two-level mode, and phase numbers of the alternating current motor winding access power grid are output to the grid-connected current control unit;
the grid voltage phase-locked loop unit is used for receiving a voltage detection signal from a grid voltage sensor, calculating to obtain an instantaneous phase and an amplitude of grid voltage and outputting the instantaneous phase and the amplitude to the grid-connected current control unit;
the grid-connected current control unit includes: the system comprises a grid-connected current instruction generation module, a d-axis current instruction generation module, a dq shafting lower current negative feedback calculation module, a proportion-multi-resonance current regulator, a power grid voltage feedforward calculation module and a coordinate inverse transformation module;
the grid-connected current instruction generating module is used for receiving grid voltage instantaneous phase and amplitude signals of the grid voltage phase-locked loop unit, receiving a grid-connected power instruction signal, obtaining a grid-connected current instruction according to the relation between power and voltage current, and outputting the grid-connected current instruction to the d-axis current instruction generating module;
the d-axis current instruction generating module is used for receiving a grid-connected current instruction, a motor position angle and a winding access phase number, calculating the d-axis current instruction according to the vector relation between the grid current and the d-axis current, and outputting the d-axis current instruction to the dq shafting lower current negative feedback calculating module;
the dq shafting lower current negative feedback calculation module is used for receiving a d-axis current instruction and a motor phase current detection value, setting the q-axis current instruction to be zero, firstly performing coordinate transformation on motor phase current to obtain d-axis current and q-axis current, subtracting the d-axis current and the q-axis current instruction to obtain an error term, and outputting the error term to the proportional-multi-resonant current regulator;
the proportion-multi-resonance current regulator is used for receiving the error terms, respectively executing the operation of the proportion regulator and the multi-resonance regulator, adding the error terms to obtain a feedback control output quantity, and outputting the feedback control output quantity to the power grid voltage feedforward calculation module;
the power grid voltage feedforward calculation module is used for receiving voltage detection signals of a power grid voltage sensor, motor position angles and winding access modes, calculating components of the power grid voltage on d and q axes from the voltage detection signals, respectively adding the components to feedback control output quantities of corresponding axes to obtain final voltage control output quantities, and outputting the final voltage control output quantities to the coordinate inverse transformation module;
the coordinate inverse transformation module is used for receiving the voltage control output quantity and the motor position angle, calculating to obtain a voltage output quantity under an m-phase coordinate system, and outputting the voltage output quantity to the bridge arm modulation unit;
the bridge arm modulation unit is used for receiving a winding access mode and voltage output quantity under an m-phase coordinate system, and firstly blocking an upper switch and a lower switch of a three-level bridge arm of the phase accessed to a power grid according to the winding access mode; then, the component of the phase which is connected into the power grid in the voltage output quantity is subjected to per-unit treatment, and then is compared with a triangular carrier to obtain a driving signal of the auxiliary two-level bridge arm, and the driving signal is output to the auxiliary two-level bridge arm; and after the components of other phases in the voltage output quantity are unified per unit, the components are compared with the triangular carrier to obtain driving signals of upper and lower switches of the bridge arm of the corresponding phase in the three-level converter, and the driving signals are output to the clamping type three-level bridge arm.
3. The control system of claim 1, wherein the operating mode switching module comprises M power diode legs and one power transistor leg;
the number of the power diode bridge arms is the sum of the number of the auxiliary inductor interfaces LP and the number of the neutral point interfaces IOP of the clamping type three-level converter, and the neutral point of each power diode bridge arm is connected with the auxiliary inductor interfaces LP or the neutral point interfaces IOP of the clamping type three-level converter;
the neutral point of the power transistor bridge arm is connected with the DC capacitor neutral point interface COP;
the cathode of the power diode bridge arm is in short circuit with the positive end of the power transistor bridge arm, and the anode of the power diode bridge arm is in short circuit with the negative end of the power transistor bridge arm.
4. A control system of a multi-motor drive three-phase grid-connected integrated drive charging circuit based on a clamping type three-level converter is characterized by comprising a controller, wherein the controller is used for sending an instruction of operating in a motor drive working condition or an instruction of operating in a grid-connected power conversion working condition to a working mode switching module of the integrated drive charging circuit;
the working mode switching module is used for receiving a mode switching instruction from the controller and changing the internal switch state according to the instruction:
when an instruction of operating in a motor driving working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP, the direct-current capacitor neutral point interface COP and the neutral point interface IOP of the clamping type three-level converter are in short circuit;
when an instruction of operating in a grid-connected power conversion working condition is received, the working mode switching module changes the internal switching state, so that the auxiliary inductor interface LP is disconnected with the DC capacitor neutral point interface COP, the neutral point interface IOP of the clamp type three-level converter is disconnected with the DC capacitor neutral point interface COP, and at the moment, the three-phase power grid is connected with Y auxiliary inductors and X clamp type three-level converter neutral points according to the electric wiring mode between the integrated drive charging circuit and the three-phase power grid;
the controller comprises a third control module corresponding to the working condition of the driving motor, and the third control module comprises X m-phase alternating current motor control units, X clamping type three-level converter modulation units, neutral point current average value calculation units of X clamping type three-level converters, a direct current filter capacitor neutral point voltage control loop and Y auxiliary inductor current control loops;
each m-phase alternating current motor control unit is used for receiving a current detection signal of a corresponding alternating current motor and a rotating speed signal of the alternating current motor, completing the regulation of the rotating speed and the current of the corresponding motor, enabling the rotating speed and the torque of the motor to meet control requirements, outputting a control voltage command to a corresponding clamping type three-level converter, and outputting the control voltage command and a current detection value of the alternating current motor to a neutral point current average value calculation unit of the corresponding clamping type three-level converter;
each clamping type three-level converter modulation unit is used for receiving a control voltage command from the corresponding m-phase alternating current motor control unit, carrying out carrier modulation, outputting a driving signal of a power switch in the corresponding clamping type three-level converter and outputting the driving signal to a clamping type three-level bridge arm;
a neutral point current average value calculating unit of each clamping type three-level converter for receiving the kth beat control voltage command value v from the corresponding m-phase alternating current motor control unit*[k]And current detection of the k-th beat AC motorMeasured value i [ k ]]Calculating to obtain kT through a voltage-current equation of the alternating current motor and a carrier modulation modesTo (k +1) TsNeutral point current average value i of corresponding clamp type three-level converternp，TsThe switching period is the switching period, and the switching period is output to a neutral point voltage control loop of the direct current filter capacitor;
a neutral point voltage control loop of the DC filter capacitor for calculating the difference between the voltages of the two DC filter capacitors, inputting the difference into the voltage regulator VR, and calculating to obtain a compensation current command i* compThe instruction and X inpAdding to obtain an auxiliary inductor current instruction i* L，i* LDividing the current by Y and then respectively outputting the current to Y auxiliary inductance current control loops;
each auxiliary inductor current control loop for calculating i* LThe difference between the/Y and the actual inductor current is input to a current regulator CR, and an inductor voltage control signal U is calculatedLTo U, to ULComparing the processed signals with a triangular carrier after per unit processing to obtain driving signals of corresponding two-level bridge arm units, and outputting the driving signals to corresponding auxiliary two-level bridge arms;
the multi-motor drive three-phase grid-connected integrated drive charging circuit based on the clamping type three-level converter comprises: the system comprises X clamping type three-level converters, two direct current filter capacitors, Y auxiliary inductors, Y auxiliary two-level bridge arms, a working mode switching module, a direct current power supply side electric interface, a motor system alternating current side electric interface and a three-phase power grid interface;
each clamping type three-level converter is composed of m clamping type three-level bridge arms, and anodes Px of the clamping type three-level bridge arms are in short circuit connection to form an anode P of an electric interface at the direct current power supply side; the negative electrodes Nx of the three-level bridge arms are in short circuit together to form a negative electrode N of the electric interface at the DC power supply side; the AC interface ACx of the three-level bridge arm is independently connected out to form an AC side electrical interface of the motor system together, and the AC side electrical interface is connected with the m-phase AC motor; neutral points Ox of the three-level bridge arms are connected together to form a neutral point O of the converter, wherein x is 1,2,3 …, and m represents the number of phases of the alternating current motor;
the two direct current filter capacitors are connected in series, and a positive electrode interface CP, a negative electrode interface CN and a neutral point interface CO are led out; the positive electrode interface CP is connected to the positive electrode P of the electric interface on the DC power supply side; the negative electrode interface CN is connected to the negative electrode N of the electric interface at the DC power supply side;
the working mode switching module is provided with three interfaces, namely an auxiliary inductor interface LP, a direct-current capacitor neutral point interface COP and a clamping type three-level converter neutral point interface IOP; the auxiliary inductor interfaces LP are connected with one end of an auxiliary inductor, and the number of the LPs is Y; the direct-current capacitor neutral point interface COP is connected with the neutral point interface CO, and the number of COPs is 1; neutral point interfaces IOP of the clamping type three-level converter are connected with neutral points O, and the number of the IOP is X;
each auxiliary inductor is provided with two ports, one end of each auxiliary inductor is connected to a corresponding auxiliary inductor interface LP in the working mode switching module, and the other end of each auxiliary inductor is connected with an alternating current side interface ACa of a corresponding two-level bridge arm unit;
each auxiliary two-level bridge arm is provided with a positive electrode Pa, a negative electrode Na and an alternating current side interface ACa, and the positive electrode Pa is connected to a positive electrode P of the direct current power supply side electrical interface; the negative electrode Na is connected to the negative electrode N of the electric interface on the direct current power supply side; the alternating current side interface ACa is connected with one end of the corresponding auxiliary inductance unit;
under the three-phase grid-connected working condition, the electric wiring mode between the integrated drive charging circuit and the three-phase power grid is determined according to X, and the following two possibilities exist:
when X is more than or equal to 3, three phases of a three-phase power grid are respectively connected to neutral points of three clamping type three-level converters;
and when X is 2, two phases of the three-phase power grid are respectively connected to neutral points of the two clamping type three-level converters, and the other phase is connected to one end of one auxiliary inductor.
5. The control system of claim 4, wherein the controller includes a fourth control module corresponding to an operating condition of the drive motor, the fourth control module comprising: the device comprises X alternating current motor rotor d-axis position angle judgment units, X alternating current motor winding access power grid mode determination units, a three-phase power grid voltage phase-locked loop unit and a grid-connected current control unit;
each alternating current motor rotor d axis position angle judging unit is used for judging a corresponding alternating current motor rotor d axis position angle and outputting the position angle to a corresponding alternating current motor winding access power grid mode determining unit and a grid-connected current control unit;
each alternating current motor winding is connected to a power grid mode determining unit and used for selecting a switch corresponding to a neutral point of a certain phase bridge arm in a corresponding clamping type three-level converter according to a d-axis position angle of a corresponding alternating current motor to be conducted, so that the motor winding of the corresponding phase is connected with one phase in a three-phase power grid, meanwhile, the clamping type three-level bridge arms of other phases work in a two-level mode, and the motor phase number of the corresponding alternating current motor winding connected to the three-phase power grid is output to a grid-connected current control unit;
the grid voltage phase-locked loop unit is used for receiving a voltage detection signal from the three-phase grid voltage sensor, calculating to obtain an instantaneous phase and an amplitude of the three-phase grid voltage, and outputting the instantaneous phase and the amplitude to the grid-connected current control unit;
the grid-connected current control unit includes: the system comprises Z grid-connected current instruction generating modules, Z d-axis current instruction generating modules, Z dq-axis lower current negative feedback computing modules, Z proportional-multi-resonance current regulators, (3-Z) auxiliary inductor current control modules, 3 grid voltage feed-forward computing modules, Z coordinate inverse transformation modules and 3 bridge arm modulation units, wherein Z is 2 or 3;
each grid-connected current instruction generating module is used for receiving the instantaneous phase and amplitude signals of the grid voltage of the three-phase grid voltage phase-locked loop unit, receiving a grid-connected power instruction signal, obtaining a grid-connected current instruction according to the relation between power and voltage current, and outputting the grid-connected current instruction to the corresponding d-axis current instruction generating module;
each d-axis current instruction generation module is used for receiving a corresponding grid-connected current instruction, a motor position angle and a winding access phase number, calculating the d-axis current instruction according to the vector relation between the grid current of the corresponding phase and the corresponding d-axis current to obtain the d-axis current instruction, and outputting the d-axis current instruction to the corresponding dq-axis lower current negative feedback calculation module;
each dq shafting lower current negative feedback calculation module is used for receiving a corresponding d-axis current instruction and a corresponding motor phase current detection value, setting the q-axis current instruction to be zero, firstly performing coordinate transformation on motor phase current to obtain d-axis current and q-axis current, subtracting the d-axis current and the q-axis current instruction to obtain an error term, and outputting the error term to a corresponding proportional-multi-resonant current regulator;
each proportion-multi-resonance current regulator is used for receiving the corresponding error term, respectively executing the operation of the proportion regulator and the multi-resonance regulator, adding the operation results to obtain feedback control output quantity, and outputting the feedback control output quantity to the corresponding power grid voltage feedforward calculation module;
each auxiliary inductance current control module is used for receiving a grid-connected power instruction signal and a detected value of auxiliary inductance current, calculating an instruction value of the auxiliary inductance current according to a phase number of an auxiliary inductor accessed into a three-phase power grid, subtracting the detected value of the auxiliary inductance current from the instruction value of the auxiliary inductance current to obtain an error term, performing proportional-multiresonance adjustment calculation on the error term to obtain auxiliary inductance current control quantity, and outputting the control quantity to the power grid voltage feedforward calculation module;
the 3 power grid voltage feedforward calculation modules are divided into Z dq-axis voltage feedforward calculation units and (3-Z) voltage feedforward calculation units of auxiliary inductors; each dq-axis voltage feedforward calculation module is used for receiving voltage detection signals of the corresponding power grid voltage sensor, corresponding motor position angles and winding access modes, calculating components of the power grid voltage in d and q axes according to the voltage detection signals, adding the components to feedback control output quantities of the corresponding axes respectively to obtain final dq-axis voltage control output quantities, and outputting the final dq-axis voltage control output quantities to the corresponding coordinate inverse transformation modules;
the voltage feedforward calculation unit of each auxiliary inductor is used for receiving a voltage detection signal of a corresponding phase power grid voltage sensor, adding the signal to a corresponding auxiliary inductor current control quantity to obtain a final auxiliary inductor control output quantity, and outputting the final auxiliary inductor control output quantity to the bridge arm modulation unit;
each coordinate inverse transformation module is used for receiving the corresponding dq axis voltage control output quantity and the motor position angle, calculating to obtain a voltage output quantity under an m-phase coordinate system, and outputting the voltage output quantity to the corresponding Z bridge arm modulation units;
the Z bridge arm modulation units are connected with the coordinate inverse transformation module and used for receiving a mode corresponding to the access of the alternating current motor winding and the voltage output quantity under an m-phase coordinate system, and the upper and lower switches of the three-level bridge arm of the phase accessed to the power grid are blocked according to the mode of the access of the winding; after the components of other motor phases which are not connected with the three-phase power grid in the voltage output quantity are subjected to per unit, the components are compared with a triangular carrier to obtain driving signals of upper and lower switches of a bridge arm of a corresponding phase in the three-level converter, and the driving signals are output to a clamping type three-level bridge arm;
and the rest (3-Z) bridge arm modulation units are used for receiving the corresponding auxiliary inductance control output quantity, comparing the auxiliary inductance control output quantity with the triangular carrier to obtain a driving signal of the corresponding auxiliary two-level bridge arm, and outputting the driving signal to the auxiliary two-level bridge arm.
6. The control system of claim 5, wherein the operating mode switching module comprises a plurality of power diode legs and a power transistor leg;
the number of the power diode bridge arms is the sum of the number of the auxiliary inductor interfaces LP and the number of the neutral point interfaces IOP of the clamping type three-level converter, and the neutral point of each power diode bridge arm is connected with the auxiliary inductor interfaces LP or the neutral point interfaces IOP of the clamping type three-level converter;
the neutral point of the power transistor bridge arm is connected with the DC capacitor neutral point interface COP;
the cathode of the power diode bridge arm is in short circuit with the positive end of the power transistor bridge arm, and the anode of the power diode bridge arm is in short circuit with the negative end of the power transistor bridge arm.
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