CN111137163B - Electric vehicle quick charging control method and system based on virtual synchronous motor - Google Patents

Electric vehicle quick charging control method and system based on virtual synchronous motor Download PDF

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CN111137163B
CN111137163B CN201811299371.9A CN201811299371A CN111137163B CN 111137163 B CN111137163 B CN 111137163B CN 201811299371 A CN201811299371 A CN 201811299371A CN 111137163 B CN111137163 B CN 111137163B
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voltage
power
current
charging
rectifier
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CN111137163A (en
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吴鸣
吕志鹏
孙丽敬
宋振浩
赵婷
周珊
刘国宇
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Taizhou Power Supply Co of State Grid Jiangsu Electric Power Co Ltd
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State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
Taizhou Power Supply Co of State Grid Jiangsu Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/10—Technologies relating to charging of electric vehicles
    • Y02T90/16—Information or communication technologies improving the operation of electric vehicles

Abstract

The invention relates to a virtual synchronous motor-based electric automobile quick charging control method and system, which are characterized in that the reactive power, the voltage amplitude and the angular frequency of a rectifier are calculated based on the voltage/current output by a synchronous power grid; determining the actual charging power of the power battery based on the droop relation of the charging mode; formulating a three-phase current reference instruction according to the obtained parameters so as to control the voltage of the direct current bus; and controlling the electric automobile to perform quick charging based on a pulse signal generated by the DC bus voltage and the resonant current of the full-bridge resonant LLC converter. The scheme realizes virtual synchronous motor control and constant-current quick charge control through the rectifier and has better coordination. The control targets of the front and rear two stages of circuits of the related system are different, and the division of labor is clear; the requirement for stabilizing the voltage of the direct-current bus is met, and the constant-current quick charging of the electric automobile is realized; the electric vehicle non-vehicle-mounted charger system comprises an acquisition module, a determination module, a preceding stage control module and a subsequent stage control module which are connected with the electric vehicle non-vehicle-mounted charger system.

Description

Electric vehicle quick charging control method and system based on virtual synchronous motor
Technical Field
The invention belongs to the technical field of power electronic application, and particularly relates to a virtual synchronous motor-based electric vehicle quick-charging control method and system.
Background
The traditional fuel oil automobile is increased in geometric progression, so that the global energy crisis and the environmental pollution are increasingly serious, and the vigorous development of the electric automobile becomes an important measure for coping with climate change and promoting energy conservation and emission reduction. The number of the electric automobiles is rapidly increased, so that the proportion of the novel electric active load in a power distribution network is increased day by day, and a charging system of the electric automobile is taken as one of important components of the electric automobile, and has great significance for meeting user requirements and safe and stable operation of a power grid by reasonably controlling the electric automobile.
The charging mode of the electric automobile is divided into slow charging and fast charging according to the magnitude of charging power. The slow charging current is small, the charging time is generally more than 6 hours, and the method is suitable for low-power charging occasions. The quick charging current is large, the charging time is generally less than 1 hour, and the quick charging method is generally suitable for a high-power off-board charger. The fast charging mode of the electric automobile is widely concerned by virtue of the advantages of high charging speed, time saving, easier satisfaction of user requirements and the like.
However, the electric vehicle belongs to a nonlinear load for a power system, and frequent switching of such a high-power charging load affects the power quality of a power grid. In order to improve the stability of the voltage and the frequency of a power grid, a student proposes that a Virtual Synchronous Motor (VSM) technology is applied to a charger of an electric vehicle, on one hand, in the transient process, inertia and damping are provided to inhibit the rapid change of the voltage and the frequency of the power grid, and support is provided for the recovery of a system; on the other hand, under the steady state condition, the system automatically participates in the voltage regulation and frequency modulation of the power grid according to the supply and demand requirements, realizes friendly interaction with the power grid, and improves the survival capability of the system.
The VSM technology can flexibly solve the access problem of the electric automobile, so that the VSM technology is deeply researched. Suul J A and other scholars study VSM control methods suitable for low-power single-phase chargers, but cannot be directly applied to three-phase chargers. Liu Ching professor proposed a VSM method suitable for a three-phase charger, but the method only verified the inertia, damping and one-time regulation characteristics of the virtual synchronous machine, and the charging mode of the electric automobile is not yet involved. Based on the scheme, the university such as Lushipeng proposes a quick-charging control scheme of the electric vehicle applying the virtual synchronous motor technology, the VSM function and the direct-current bus voltage are stabilized at the front stage, and the constant-voltage charging is realized at the rear stage. However, the scheme adopts a resistor to simulate a rechargeable battery of the electric automobile, constant-voltage charging is realized through double closed-loop control, the charging mode is unclear, and constant-current or constant-power charging is usually adopted for quick charging; secondly, because of the adoption of an ideal power grid, the simulation result cannot prove the primary frequency modulation characteristic of the VSM.
Disclosure of Invention
In order to make up for the defects, the invention provides a virtual synchronous motor-based electric vehicle fast charging control method and system, provides technical support for the novel VSM control field applicable to electric vehicle fast charging, has great research value and significance, and solves the problems of power grid frequency and voltage quality caused by frequent switching of high-power charging loads.
The invention is realized by adopting the following technical scheme:
a virtual synchronous motor-based electric vehicle fast charging control method comprises the following steps:
calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
determining the actual charging power of the power battery based on the droop relation of the charging mode;
according to the rectifier reactive power, the voltage amplitude and the angular frequency and the actual charging power of the power battery, a three-phase current reference instruction is formulated to control the direct-current bus voltage;
and controlling the electric automobile to perform quick charging based on the pulse signal generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter.
Preferably, the formulating a three-phase current reference command according to the rectifier reactive power, the voltage amplitude and the angular frequency and the actual charging power of the power battery to control the dc bus voltage includes:
inputting the rectifier reactive power and reactive power reference values and the rectifier voltage amplitude and voltage amplitude reference values into a pre-established excitation control model, and outputting an excitation electromotive potential instruction;
inputting the rectifier angular frequency, the angular frequency reference value, the power battery charging power and the charging power set value into a rotor motion equation, and outputting an angle instruction;
superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
and controlling the voltage of the direct current bus according to the pulse signal generated by the three-phase current reference instruction.
Further, the controlling the voltage of the direct current bus according to the pulse signal generated by the three-phase current reference command comprises:
and 6 paths of pulse signals generated according to the three-phase current reference instruction are used for conducting a switching tube of the three-phase voltage type PWM rectifier, so that the voltage of the direct-current bus stably runs.
Preferably, the controlling the electric vehicle to perform fast charging based on a pulse signal generated by the dc bus voltage and the resonant current of the full-bridge resonant LLC converter includes:
acquiring direct-current bus voltage of voltage-stabilizing operation and resonant current of a full-bridge resonant LLC converter;
and 4 paths of pulses generated according to the voltage of the direct current bus running in the voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter conduct a switching tube of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
Preferably, the droop relationship of the charge mode is determined by the following equation:
Figure GDA0001992289660000031
in the formula, P bat For the actual charging power of the power battery, Q is the actual input reactive power of the rectifier, omega g For the actual angular frequency, Q, of the rectifier set 、ω n 、U n Respectively setting the reactive power of the rectifier, the rated angular frequency and the rated voltage; d p And D q Respectively representing the droop coefficients, U, of active frequency and reactive voltage bat Actual charging voltage for power battery, I bat-set Is the charging current set point.
Further, the charging current setting value is determined by:
I bat-set > | Capacity (Ah) | (2)
Further, when the actual charging current is less than the charging current set value, the actual charging power of the power battery is calculated by the following formula:
Figure GDA0001992289660000032
when the actual charging current is equal to the charging current set value, calculating the actual charging power of the power battery by the following formula:
Figure GDA0001992289660000033
where eta is the efficiency coefficient eta varying with power bat P, P being the reactive power of the rectifier, P bat For the actual charging power, P, of the power cell e And P m Virtual electromagnetic power and mechanical power, respectively.
A virtual synchronous motor-based electric vehicle quick charging control system comprises an acquisition module, a determination module, a preceding stage control module and a subsequent stage control module, wherein the acquisition module, the determination module, the preceding stage control module and the subsequent stage control module are connected with an electric vehicle off-board charger system; wherein the content of the first and second substances,
the acquisition module is used for calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
the determining module is used for determining the actual charging power of the power battery based on the droop relation of the charging mode;
the preceding stage control module is used for making a three-phase current reference instruction according to the reactive power, the voltage amplitude and the angular frequency of the rectifier and the actual charging power of the power battery so as to control the voltage of a direct-current bus; and the rear-stage control module is used for controlling the electric automobile to carry out quick charging based on the pulse signals generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter.
Preferably, the electric vehicle off-board charger system includes: a synchronous power grid formed by synchronous generators with primary voltage regulation and frequency modulation functions; the synchronous power grid is connected with the power battery through the LC filter circuit, the three-phase voltage type PWM rectifier and the full-bridge resonant LLC converter; and the output end of the synchronous power grid is connected with the acquisition module.
Preferably, the obtaining module includes:
the acquisition unit is used for acquiring voltage and current output by the synchronous power grid;
the measurement calculation unit (1) is used for calculating the rectifier reactive power and the voltage amplitude of the excitation control unit (2) and the angular frequency of the droop control unit (3);
the determining module comprises: the droop control unit (3) is used for defining the droop relation of the power battery in the charging mode;
the preceding stage control module includes:
the command formulation submodule is used for formulating a three-phase current reference command;
the preceding stage control submodule is used for controlling the voltage of the direct current bus according to a pulse signal generated by the three-phase current reference instruction; wherein the content of the first and second substances,
the instruction making submodule includes:
the excitation control unit (2) is used for inputting the rectifier reactive power and reactive power reference values, and the rectifier voltage amplitude and voltage amplitude reference values into a pre-established excitation control model and outputting an excitation electromotive potential instruction;
the rotor motion equation unit (4) is used for inputting the rectifier angular frequency and angular frequency reference value, and the power battery charging power and charging power set value into a rotor motion equation and outputting an angle command;
the voltage synthesis unit (5) is used for superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
the stator voltage equation unit (6) is used for inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
the preceding stage control submodule includes:
the current control unit (7) is used for generating 6 paths of pulse signals through a three-phase current reference instruction;
the SVPWM unit (8) is used for conducting a switching tube of the three-phase voltage type PWM rectifier according to 6 paths of pulse signals generated by the three-phase current reference instruction so as to enable the voltage of a direct-current bus to stably operate;
the back-stage control module comprises:
the effective value measuring unit (9) is used for measuring the resonance current of the full-bridge resonance LLC conversion circuit;
the double closed loop control unit (10) is used for generating 4 paths of pulse signals according to the direct current bus voltage in voltage stabilization operation and the resonance current of the full-bridge resonance LLC conversion circuit;
and the PWM unit (11) is used for conducting a switching tube of the full-bridge resonant LLC converter according to 4 paths of pulses generated by the voltage of the direct-current bus running in a voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
Further, the measurement calculation unit (1) is respectively connected with the excitation control unit (2) and the droop control unit (3);
the droop control unit (3) is connected with the rotor motion equation unit (4), and the excitation control unit (2) and the rotor motion equation unit (4) are respectively connected with the voltage synthesis unit (5);
the voltage synthesis unit (5) is respectively connected with the stator voltage equation unit (6), the current control unit (7) and the SVPWM unit (8);
and the effective value measuring unit (9) is respectively connected with the double closed-loop control unit (10) and the PWM unit (11).
Further, the SVPWM unit (8) is connected in series with a control signal input terminal of the three-phase voltage source PWM rectifier;
and the PWM unit (11) is connected with the control signal input end of the full-bridge resonant LLC converter in series.
Compared with the closest prior art, the invention has the following beneficial effects:
the invention discloses a virtual synchronous motor-based electric vehicle quick charging control method and system, which are characterized in that the reactive power, the voltage amplitude and the angular frequency of a rectifier are calculated based on the voltage/current output by a synchronous power grid; determining the actual charging power of the power battery based on the droop relation of the charging mode; according to the reactive power, the voltage amplitude and the angular frequency of the rectifier and the actual charging power of the power battery, a three-phase current reference instruction is formulated to control the voltage of a direct current bus; the correction of the circuit factor is realized, and the direct current bus voltage is stabilized.
Controlling the electric automobile to perform quick charging based on a pulse signal generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter; the virtual synchronous motor is guaranteed to have the same inertia and damping characteristics as the traditional synchronous motor and the primary frequency modulation and voltage regulation capabilities, and the constant-current quick-charging function of the power battery is realized. The scheme realizes virtual synchronous motor control and constant-current quick charge control through the rectifier and has better coordination.
The control targets of the front and rear two stages of circuits of the related system are different, and the division of labor is clear; the system mainly comprises an acquisition module, a determination module, a preceding stage control module and a subsequent stage control module which are connected with an off-board charger system of the electric automobile.
The acquisition module is used for calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid; the determining module is used for determining the actual charging power of the power battery based on the droop relation of the charging mode; the preceding stage control module is used for making a three-phase current reference instruction according to the reactive power, the voltage amplitude and the angular frequency of the rectifier and the actual charging power of the power battery so as to control the voltage of a direct-current bus; the rear-stage control module is used for controlling the electric automobile to carry out quick charging on the basis of pulse signals generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter; the requirement of stabilizing the voltage of the direct-current bus is met, and meanwhile, the constant-current quick charging of the electric automobile is realized.
Drawings
FIG. 1 is a flow chart of a control method provided in an embodiment of the present invention;
FIG. 2 is a topological structure diagram of an off-board charger of an electric vehicle according to an embodiment of the present invention;
fig. 3 is a control block diagram of a virtual synchronous motor suitable for fast charging of an electric vehicle according to an embodiment of the present invention;
FIG. 4 is a diagram of an electric vehicle simulation system provided in an embodiment of the present invention;
fig. 5 is a waveform diagram of active power of a rectifier according to variations of inertia J and damping D, where (a) is an active power waveform diagram when J varies, and (b) is an active power waveform diagram when D varies;
fig. 6 is a primary regulation characteristic diagram of the VSM provided in the embodiment of the present invention, in which (a) is an active power variation diagram, (b) is a frequency variation diagram, (c) is a reactive power variation diagram, and (d) is a voltage amplitude variation diagram;
FIG. 7 is a waveform diagram of a dynamic response of an off-board charger I provided in an embodiment of the present invention, where (a) 1 ) For the active power of the rectifier under conventional control, (a) 2 ) For the active power of the rectifier under the control mentioned, (b) 1 ) Is the reactive power of the rectifier under the traditional control, (b) 2 ) For the reactive power of the rectifier under the control mentioned, (c) 1 ) Is the active power of the power grid under the traditional control, (c) 2 ) For the active power of the grid under the control mentioned, (d) 1 ) Is the reactive power of the power grid under the traditional control, (d) 2 ) For the reactive power of the grid under the proposed control,(e 1 ) For the grid frequency under the conventional control, (e) 2 ) For the grid frequency under the control mentioned, (f) 1 ) For the grid voltage amplitude under the traditional control, (f) 2 ) For the grid voltage amplitude under the control mentioned, (g) 1 ) For the charging current of the power battery under the traditional control, (g) 2 ) For the charging current of the power battery under the control, (h) 1 ) Is the direct current bus voltage under the traditional control, (h) 2 ) The DC bus voltage under the control is provided.
Detailed Description
Embodiments of the process of the present invention are described in detail below with reference to the accompanying drawings.
The invention provides a virtual synchronous motor-based electric vehicle quick charging control system, which comprises an acquisition module, a determination module, a preceding stage control module and a subsequent stage control module, wherein the acquisition module, the determination module, the preceding stage control module and the subsequent stage control module are connected with an off-board charger system of an electric vehicle; wherein the content of the first and second substances,
the acquisition module is used for calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
the determining module is used for determining the actual charging power of the power battery based on the droop relation of the charging mode;
the preceding stage control module is used for making a three-phase current reference instruction according to the reactive power, the voltage amplitude and the angular frequency of the rectifier and the actual charging power of the power battery so as to control the voltage of a direct-current bus; and the rear-stage control module is used for controlling the electric automobile to carry out quick charging based on the pulse signals generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter.
Wherein, the acquisition module includes:
the acquisition unit is used for acquiring voltage and current output by the synchronous power grid;
the measurement calculation unit (1) is used for calculating the rectifier reactive power and the voltage amplitude of the excitation control unit (2) and the angular frequency of the droop control unit (3);
the determining module comprises: the droop control unit (3) is used for defining the droop relation of the power battery in the charging mode;
the preceding stage control module includes:
the command formulation submodule is used for formulating a three-phase current reference command;
the preceding stage control submodule is used for controlling the voltage of the direct current bus according to a pulse signal generated by the three-phase current reference instruction; wherein the content of the first and second substances,
the instruction making submodule comprises:
the excitation control unit (2) is used for inputting the rectifier reactive power and reactive power reference values, and the rectifier voltage amplitude and voltage amplitude reference values into a pre-established excitation control model and outputting an excitation electromotive potential instruction;
the rotor motion equation unit (4) is used for inputting the rectifier angular frequency and angular frequency reference value, and the power battery charging power and charging power set value into a rotor motion equation and outputting an angle command;
the voltage synthesis unit (5) is used for superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
the stator voltage equation unit (6) is used for inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
the preceding stage control submodule includes:
the current control unit (7) is used for generating 6 paths of pulse signals through a three-phase current reference instruction;
the SVPWM unit (8) is used for conducting a switching tube of the three-phase voltage type PWM rectifier according to 6 paths of pulse signals generated by the three-phase current reference instruction so as to enable the voltage of a direct-current bus to stably operate;
the back-stage control module comprises:
the effective value measuring unit (9) is used for measuring the resonance current of the full-bridge resonance LLC conversion circuit;
the double closed loop control unit (10) is used for generating 4 paths of pulse signals according to the direct current bus voltage in voltage stabilization operation and the resonance current of the full-bridge resonance LLC conversion circuit;
and the PWM unit (11) is used for conducting a switching tube of the full-bridge resonant LLC converter according to 4 paths of pulses generated by the voltage of the direct-current bus running in a voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
As shown in fig. 3, the measurement calculation unit (1) is respectively connected with the excitation control unit (2) and the droop control unit (3);
the droop control unit (3) is connected with the rotor motion equation unit (4), and the excitation control unit (2) and the rotor motion equation unit (4) are respectively connected with the voltage synthesis unit (5);
the voltage synthesis unit (5) is respectively connected with the stator voltage equation unit (6), the current control unit (7) and the SVPWM unit (8);
the effective value measuring unit (9) is respectively connected with the double closed-loop control unit (10) and the PWM unit (11).
The SVPWM unit (8) is connected with a control signal input end of the three-phase voltage source PWM rectifier in series;
the PWM unit (11) is connected with the input end of a control signal of the full-bridge resonant LLC converter in series.
As shown in fig. 2, the electric vehicle off-board charger system integrally includes a synchronous grid formed by synchronous generators with primary voltage and frequency regulation functions; the synchronous power grid is connected with the power battery through the LC filter circuit, the three-phase voltage type PWM rectifier and the full-bridge resonant LLC converter; the synchronous power grid charges the power battery through an LC filter circuit, a three-phase voltage type PWM rectifier and a full-bridge resonance LLC conversion circuit; the synchronous power grid is formed by a synchronous generator with primary voltage regulation and frequency modulation characteristics, is an equivalent model of all power supplies in the actual power grid, and the capacity of the synchronous power grid is the sum of the capacities of all the power supplies. In fig. 3, the output of the synchronization grid is connected to a measurement and calculation unit (1) comprised by the acquisition module.
The invention provides a virtual synchronous motor-based electric vehicle quick-charging control method, which comprises the following steps of: output voltage u of preceding stage circuit through sampling synchronous power grid abc And an output current i abc The measurement and calculation unit 1 generates the rectifier reactive power Q and the voltage amplitude U of the excitation control unit 2 m And P based on charging mode bat -omega droop control unit 3Angular frequency of (omega) g The reactive power Q of the rectifier and the reference value Q of the reactive power n Voltage amplitude U m And a voltage amplitude reference value U n After the excitation electromotive force is sent to an excitation control unit 2, an excitation electromotive force instruction is output, and the power battery charging power P is obtained bat Charging power set value P bat Set, angular frequency ω g And angular frequency reference value omega n Sending P based on charging mode bat The-omega droop control unit 3 enters a rotor motion equation unit 4, outputs an angle theta instruction, and sends an excitation electromotive force amplitude instruction E and the angle instruction theta into a three-phase excitation electromotive force E obtained by a voltage synthesis unit 5 abc The three-phase current reference instruction i is obtained after the instruction passes through a stator voltage equation unit 6 f , abc 6 paths of pulse signals are generated after passing through the current control unit 7 and the SVPWM unit 8 to conduct a switching tube of the three-phase voltage type PWM rectifier; resonant current i of rear-stage full-bridge resonant LLC (logical link control) conversion circuit r Via the effective value measuring unit 9, I is obtained r And the DC bus voltage U dc The signals are sent to a double closed-loop control unit 10 and a PWM unit 11 to generate 4 paths of pulses to conduct a switching tube of the full-bridge resonant LLC converter.
The control method shown in fig. 1 specifically includes the following steps:
s1, calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
s2, determining the actual charging power of the power battery based on the droop relation of the charging mode;
s3, according to the rectifier reactive power, the voltage amplitude and the angular frequency and the actual charging power of the power battery, a three-phase current reference instruction is formulated to control the direct-current bus voltage;
and S4, controlling the electric vehicle to perform quick charging based on the direct-current bus voltage and a pulse signal generated by the resonance current of the full-bridge resonance LLC converter.
In step S2, the drooping relationship of the charging mode is determined by the following equation:
Figure GDA0001992289660000091
in the formula, P bat For the actual charging power of the power battery, Q is the actual input reactive power of the rectifier, omega g For the actual angular frequency, Q, of the rectifier set 、ω n 、U n Respectively setting the reactive power of the rectifier, the rated angular frequency and the rated voltage; d p And D q Respectively representing the droop coefficients, U, of active frequency and reactive voltage bat Actual charging voltage for power battery, I bat-set Is the charging current set point.
Determining the charging current set point by:
I bat-set > | Capacity (Ah) | (2)
When the actual charging current is smaller than the set charging current value, calculating the actual charging power of the power battery by the following formula:
Figure GDA0001992289660000092
when the actual charging current is equal to the charging current set value, calculating the actual charging power of the power battery by the following formula:
Figure GDA0001992289660000101
where eta is the efficiency coefficient eta varying with power bat P, P being the reactive power of the rectifier, P bat For the actual charging power, P, of the power cell e And P m Virtual electromagnetic power and mechanical power, respectively.
Step S3 is to formulate a three-phase current reference command according to the rectifier reactive power, the voltage amplitude and the angular frequency and the actual charging power of the power battery, so as to control the dc bus voltage, including:
inputting the rectifier reactive power and reactive power reference value, and the rectifier voltage amplitude and voltage amplitude reference value into a pre-established excitation control model, and outputting an excitation electromotive potential instruction;
inputting the angular frequency of the rectifier, the angular frequency reference value, the charging power of the power battery and the charging power set value into a rotor motion equation, and outputting an angle instruction;
superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
and controlling the voltage of the direct current bus according to the pulse signal generated by the three-phase current reference instruction.
Step S4, based on the pulse signal generated by the dc bus voltage and the resonant current of the full-bridge resonant LLC converter, controlling the electric vehicle to perform fast charging includes:
acquiring direct-current bus voltage of voltage-stabilizing operation and resonant current of a full-bridge resonant LLC converter;
and 4 paths of pulses generated according to the voltage of the direct current bus running in the voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter conduct a switching tube of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
In summary, the technical solution has technical and methodological innovations including:
(1) the control targets of the front and rear two-stage circuits are different, and the division of labor is clear. The novel VSM control of the preceding stage can realize the constant-current quick-charging function of the electric automobile while reflecting the inertia, damping and one-time regulation characteristics which are the same as those of the synchronous motor; the rear-stage double closed-loop control is mainly responsible for stabilizing the voltage of the direct-current bus.
(2) Droop control based on a charging mode in novel VSM control can enable an off-board charger to charge a power battery in a constant-current quick-charging mode by setting a charging current set value.
Example (b):
FIG. 2 is a topological structure diagram of a non-vehicular charger for an electric vehicle, which integrally comprises a synchronous power grid, and a power battery is charged by an LC filter circuit, a three-phase voltage type PWM rectifier and a full-bridge resonant LLC conversion circuit; the synchronous power grid is formed by a synchronous generator with primary voltage regulation and frequency modulation characteristics, is an equivalent model of all power supplies in the actual power grid, and the capacity of the synchronous power grid is the sum of the capacities of all the power supplies.
Fig. 3 shows a control block diagram of a virtual synchronous motor suitable for fast charging of an electric vehicle. The output end of the preceding stage synchronous power grid is connected with a measurement and calculation unit 1, and the measurement and calculation module 1 is respectively connected with an excitation control unit 2 and a charging mode-based P bat - ω droop control unit 3 connected, based on P of the charging mode bat The-omega droop control unit 3 is connected with the rotor motion equation unit 4, the excitation control unit 2 and the rotor motion equation unit 4 are connected with the voltage synthesis module 5 together, the voltage synthesis unit 5 is connected with the stator voltage equation unit 6, the current control unit 7 and the SVPWM unit 8 respectively, and the control signal input ends of the three-phase voltage source PWM rectifier of the SVPWM unit 8 are connected in series; the resonant current of the rear-stage full-bridge resonant LLC converter is respectively connected with the effective value measuring unit 9, the double closed-loop control unit 10 and the PWM unit 11, and the PWM unit 11 is connected with the control signal input end of the full-bridge resonant LLC converter in series.
The P based on the charging mode bat The-omega droop control unit 3 can realize that the off-board charger charges the power battery in a constant-current quick-charging mode by taking the charging mode of the electric automobile into consideration on the basis of the traditional droop control method, and a droop relational expression based on the charging mode is
Figure GDA0001992289660000111
Wherein, U bat Is the actual charging voltage of the power battery, I bat-set Is the charging current set point.
Since the capacity of the power battery is represented by Ah, the capacity is equal to the product of the charging current (a) and the charging time (h), i.e., the capacity (Ah) is the charging current (a) × time (h). When the electric automobile adopts the quick charging mode, the charging time is usually less than 1h, namely the time (h) <1 h. The constant current quick charging function is realized, and the device is required to be arranged
I bat-set > | Capacity (Ah) | (2)
Said for realizing charging modeP bat The connection of the- ω droop control unit 3 and the rotor equation of motion unit 4 has two configurations depending on whether losses are considered or not. If the efficiency of the conversion circuit is very high, the losses can be neglected, and the following relation can be derived:
Figure GDA0001992289660000112
if the efficiency is not neglected, let us assume that we continue to use equation (3), which will cause the actual charging current to be slightly less than the set value, i.e., I bat <I bat-ref . Therefore, in order to strictly let I bat ＝I bat-ref Equation (3) is modified as follows:
Figure GDA0001992289660000121
in the formula (4), η is an efficiency coefficient varying with power, and its expression is that η ═ P bat and/P. P is not only the rectifier power, but also the input power of the off-board charger. P bat Representing the charging power of the power battery and the output power of the off-board charger.
The specific control process is as follows:
output voltage u of preceding stage circuit through sampling synchronous power grid abc And an output current i abc The measurement and calculation module 1 is used for generating the rectifier reactive power Q and the voltage amplitude U of the excitation control unit 2 m And P based on charging mode bat -angular frequency ω of ω droop control unit 3 g The reactive power Q of the rectifier and the reference value Q of the reactive power n Voltage amplitude U m And a voltage amplitude reference value U n After the excitation electromotive force is sent to an excitation control unit 2, an excitation electromotive force E instruction is output, and the power battery charging power P is obtained bat Charging power set value P bat-set Angular frequency omega g And angular frequency reference value omega n Sending P based on charging mode bat The-omega droop control unit 3 enters a rotor motion equation unit 4 and outputs an angle theta command, and the exciting electromotive force is excitedThe amplitude instruction E and the angle instruction theta are sent to the three-phase excitation electromotive force E obtained by the voltage synthesis unit 5 abc The three-phase current reference instruction i is obtained after the instruction passes through a stator voltage equation unit 6 f,abc * 6 paths of pulse signals are generated after passing through the current control unit 7 and the SVPWM unit 8 to conduct a switching tube of the three-phase voltage type PWM rectifier; resonant current i of rear-stage full-bridge resonant LLC (logical link control) conversion circuit r Via the effective value measuring unit 9, I is obtained r And the DC bus voltage U dc The signals are sent to a double closed-loop control unit 10 and a PWM unit 11 to generate 4 paths of pulses to conduct a switching tube of the full-bridge resonant LLC converter.
And (3) constructing an electric vehicle simulation system diagram shown in FIG. 4 in MATLAB/Simulink, and verifying the effectiveness of the provided control strategy.
Verification of inertia and damping characteristics
Taking the off-board charger I in fig. 4 as an example, three typical values of inertia and damping are selected to observe the effect of different inertia and damping on the rectifier active power, i.e., J0.05, 1,1.5 and D12, 20, 30. In the initial state, the power grid supplies power to the power battery I and the power battery II. And the power battery II is out of operation at 1 second. Fig. 5 shows the active power waveform of the rectifier with the inertia J and the damping D, wherein (a) is the active power waveform when J changes, and (b) is the active power waveform when D changes.
As can be seen from fig. 5, the proposed VSM strategy introduces the inertia and damping characteristics of the synchronous motor into the control of the off-board charger. As can be seen from fig. 5(a), the moment of inertia J can suppress abrupt power changes, but as J increases, the dynamic response of the system becomes slow, and the active power starts to oscillate; in fig. 5(b), as the damping D increases, the oscillation of the system is suppressed, but too much damping lengthens the time taken for the system to reach a steady state. Therefore, the inertia and the damping effect described above are consistent with the dynamic characteristics of the synchronous motor.
Verification of primary regulation characteristic
The off-board charger I in fig. 4 was taken as a research point to verify the primary regulation characteristic of the VSM. Simulation working conditions are as follows: firstly, before 1.5 seconds, the power grid supplies power to a 1kVar reactive load, a power battery I and a power battery II. And secondly, stopping the off-board charger II after 1.5 seconds, and connecting the off-board charger II to the power grid again after 2.5 seconds. And running of the 1kVar reactive load of the AC interface is quitted at 3.5 s. It is worth noting that when the active and reactive power fluctuates, the regulation ratio of the grid and the off-board charger I is set to 1: 1. In addition, the active power of the off-board charger II is set to 30 kW. Fig. 6 shows the primary regulation characteristic of the VSM, in which (a) is an active power variation diagram, (b) is a frequency variation diagram, (c) is a reactive power variation diagram, and (d) is a voltage amplitude variation diagram.
As can be seen from fig. 6(a), (c), according to the 1:1 regulation ratio, the rectifier increases the absorption of 15kW of active power between 1.5s and 2.5s in addition to the power taken up by the grid, the reactive power exiting the rectifier due to the reactive load changes from-500 Var to 0 Var. Meanwhile, as can be seen from fig. 6(b) and (d), the frequency and voltage of the VSM are adjusted according to their droop characteristics. Thus, in steady state, the proposed VSM participates in the frequency and voltage regulation when the charging load is frequently switched back on and off.
(III) control scheme comparison verification
With fig. 4 as a simulation system, the proposed control method and the conventional control are applied to the off-board charger I, respectively. The traditional control means that the off-board charger does not have the power regulation characteristic of a synchronous motor and only realizes the charging function. When the power battery II is started or stopped through the off-board charger II and the reactive power of the alternating current interface fluctuates, the two control methods compare the influences of the frequency and the voltage of the power grid. Explained further, for the VSM-controlled non-vehicle charger I, the rated capacity of the power battery I is 100Ah, and in order to enable the power battery I to work in the constant-current quick-charging mode, the charging current reference value is set to be 1.5 times of the rated capacity, namely I bat-ref 1.5| Capacity | 150A, so P bat-ref ＝I bat-ref ×U bat ＝150U bat 。
Based on the above working conditions and parameter settings, three simulation situations are set: the simulation time was 4.5 seconds. Before 1.5 seconds, the power battery I is rapidly charged by the power grid through the off-board charger I at a charging current of 150A. ② at 1.5s, the power battery II passes throughAnd the off-board charger II is connected to the power grid and quits the operation within 2.5 seconds. In this time range, the active power consumed by the offboard charger II was 60 kW. And thirdly, the 2kVar reactive load at the AC interface is connected into the power grid in 3.5 s. FIG. 6 shows the dynamic response waveform of the off-board charger I, with the red line representing the conventional control (denoted by x) 1 Denotes, x ═ a, b, c.., h), and the blue line denotes the proposed control (denoted by x ═ a, b, c.., h) 2 Denotes, x ═ a, b, c.., h), where (a) is 1 ) For the active power of the rectifier under conventional control, (a) 2 ) For the active power of the rectifier under the control mentioned, (b) 1 ) Is the reactive power of the rectifier under the traditional control, (b) 2 ) For the reactive power of the rectifier under the control mentioned, (c) 1 ) Is the active power of the power grid under the traditional control, (c) 2 ) For the active power of the grid under the control mentioned, (d) 1 ) Is the reactive power of the power grid under the traditional control, (d) 2 ) For the reactive power of the grid under the control mentioned, (e) 1 ) For the grid frequency under the conventional control, (e) 2 ) For the grid frequency under the control mentioned, (f) 1 ) For the grid voltage amplitude under the traditional control, (f) 2 ) For the grid voltage amplitude under the control mentioned, (g) 1 ) For the charging current of the power battery under the traditional control, (g) 2 ) For the charging current of the power battery under the control, (h) 1 ) Is the direct current bus voltage under the traditional control, (h) 2 ) The DC bus voltage under the control is provided.
As shown in fig. 7, in the initial state, the power grid charges the power battery I at a charging current of 150A through the off-board charger I. When the power battery II is connected to the grid at 1.5s and the reactive load is connected to the ac interface at 3.5s, for conventional control, from fig. 7 (a) 1 )、(b 1 ) It can be seen that no matter how the load changes, the off-board charger I system does not participate in active and reactive power regulation. In this case, the power change is fully assumed by the grid. The active power sent by the power grid is increased from 115kW to 175kW (as shown in FIG. 7 (c) 1 ) Shown), which results in a reduction of the grid frequency by 0.32Hz (as shown in fig. 7 (e) 1 ) Shown). Further, from FIG. 7 (d) 1 )、(f 1 ) It can be seen that at 3.5 seconds, the reactive power generated by the grid increases from 0Var to 20 Var00Var, which results in a voltage amplitude drop from 311.159V to 306V.
In contrast, for the proposed control method, the off-board charger I and the grid share the active and reactive power in a 1:1 ratio. Between 1.5s and 2.5s from FIG. 7 (a) 2 ) And (c) 2 ) It can be observed that the active power of the rectifier is reduced from 100kW to 75kW and the power transmitted by the grid is increased from 115kW to 145 kW. The adjustment sum of the two is equal to 60kW of active power consumed by the off-board charger II. FIG. 7 (e) is compared with the conventional control 2 ) The grid frequency in (1) drops by only 0.17 Hz. FIG. 7 (b) shows the connection of a 2kVar reactive load at 3.5s 2 ) And (d) 2 ) The rectifier is shown to reduce the reactive absorption of 1kVar and the grid generates 1kVar of reactive power. FIG. 7 (f) according to the reactive droop coefficient 2 ) The voltage amplitude of the medium power grid is reduced by 3.15V, and the reduction degree of the voltage amplitude is smaller than that of the traditional control. Since the VSM-controlled off-board charger I takes part in the frequency and voltage regulation, FIG. 7 (g) shows the power battery II during the connection thereof 2 ) The charging current of the medium power battery I is reduced. However, in FIG. 7 (g) 1 ) In the conventional control of (2), the charging current is kept constant at 150A. In addition, in FIG. 7 (h) 2 ) In this way, the post-stage double closed-loop control can stabilize the dc bus voltage at the reference value of 800V.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application and not for limiting the protection scope thereof, and although the present application is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: numerous variations, modifications, and equivalents will occur to those skilled in the art upon reading the present application and are within the scope of the claims appended hereto.

Claims (10)

1. A virtual synchronous motor-based electric vehicle fast charging control method is characterized by comprising the following steps:
calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
determining the actual charging power of the power battery based on the droop relation of the charging mode;
according to the rectifier reactive power, the voltage amplitude and the angular frequency and the actual charging power of the power battery, a three-phase current reference instruction is formulated to control the direct-current bus voltage;
controlling the electric automobile to perform quick charging based on the direct-current bus voltage and a pulse signal generated by the resonance current of the full-bridge resonance LLC converter;
according to rectifier reactive power, voltage amplitude and angular frequency and power battery's actual charging power, formulate three-phase current reference instruction to control direct current busbar voltage includes:
inputting the rectifier reactive power and reactive power reference values and the rectifier voltage amplitude and voltage amplitude reference values into a pre-established excitation control model, and outputting an excitation electromotive potential instruction;
inputting the rectifier angular frequency, the angular frequency reference value, the power battery charging power and the charging power set value into a rotor motion equation, and outputting an angle instruction;
superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
and controlling the voltage of the direct current bus according to the pulse signal generated by the three-phase current reference instruction.
2. The method of claim 1, wherein controlling the dc bus voltage according to the pulsed signals generated by the three-phase current reference commands comprises:
and 6 paths of pulse signals generated according to the three-phase current reference instruction are used for conducting a switching tube of the three-phase voltage type PWM rectifier, so that the voltage of the direct-current bus stably runs.
3. The method of claim 1, wherein the controlling the electric vehicle to perform fast charging based on the pulse signal generated by the DC bus voltage and the resonant current of the full-bridge resonant LLC converter comprises:
acquiring direct-current bus voltage of voltage-stabilizing operation and resonant current of a full-bridge resonant LLC converter;
and 4 paths of pulses generated according to the voltage of the direct current bus running in the voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter conduct a switching tube of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
4. The method of claim 1, wherein the droop relationship for the charging mode is determined by:
Figure FDA0003579604680000021
in the formula, P bat For the actual charging power of the power battery, Q is the actual input reactive power of the rectifier, omega g For the actual angular frequency, Q, of the rectifier set 、ω n 、U n Respectively setting the reactive power of the rectifier, the rated angular frequency and the rated voltage; d p And D q Respectively representing the droop coefficients, U, of active frequency and reactive voltage bat Actual charging voltage for power battery, I bat-set Is the charging current set point.
5. The method of claim 4, wherein the charging current set point is determined by:
I bat-set > | Capacity (Ah) | (2).
6. The method of claim 5, wherein when the actual charging current is less than the charging current set point, the actual charging power of the power battery is calculated by:
Figure FDA0003579604680000022
when the actual charging current is equal to the charging current set value, calculating the actual charging power of the power battery by the following formula:
Figure FDA0003579604680000023
where eta is the efficiency coefficient eta varying with power bat P, P being the reactive power of the rectifier, P bat For the actual charging power, P, of the power cell e And P m Virtual electromagnetic power and mechanical power, respectively.
7. A virtual synchronous motor-based electric vehicle quick charging control system is characterized by comprising an acquisition module, a determination module, a preceding stage control module and a subsequent stage control module, wherein the acquisition module, the determination module, the preceding stage control module and the subsequent stage control module are connected with an off-board charger system of an electric vehicle; wherein the content of the first and second substances,
the acquisition module is used for calculating the reactive power, the voltage amplitude and the angular frequency of the rectifier based on the voltage and the current output by the synchronous power grid;
the determining module is used for determining the actual charging power of the power battery based on the droop relation of the charging mode;
the preceding stage control module is used for making a three-phase current reference instruction according to the reactive power, the voltage amplitude and the angular frequency of the rectifier and the actual charging power of the power battery so as to control the voltage of a direct-current bus; the rear-stage control module is used for controlling the electric automobile to carry out quick charging on the basis of pulse signals generated by the direct-current bus voltage and the resonance current of the full-bridge resonance LLC converter;
the acquisition module includes:
the acquisition unit is used for acquiring voltage and current output by the synchronous power grid;
the measurement calculation unit (1) is used for calculating the rectifier reactive power and the voltage amplitude of the excitation control unit (2) and the angular frequency of the droop control unit (3);
the determining module comprises: the droop control unit (3) is used for defining the droop relation of the power battery in the charging mode;
the preceding stage control module includes:
the command formulation submodule is used for formulating a three-phase current reference command;
the preceding stage control submodule is used for controlling the voltage of the direct current bus according to a pulse signal generated by the three-phase current reference instruction; wherein the content of the first and second substances,
the instruction making submodule includes:
the excitation control unit (2) is used for inputting the rectifier reactive power and reactive power reference values, and the rectifier voltage amplitude and voltage amplitude reference values into a pre-established excitation control model and outputting an excitation electromotive potential instruction;
the rotor motion equation unit (4) is used for inputting the rectifier angular frequency and angular frequency reference value, and the power battery charging power and charging power set value into a rotor motion equation and outputting an angle command;
the voltage synthesis unit (5) is used for superposing the excitation electromotive force amplitude instruction and the angle instruction to generate a three-phase excitation electromotive force instruction;
the stator voltage equation unit (6) is used for inputting the three-phase excitation electromotive force instruction into a stator voltage equation to obtain a three-phase current reference instruction;
the preceding stage control submodule includes:
the current control unit (7) is used for generating 6 paths of pulse signals through a three-phase current reference instruction;
the SVPWM unit (8) is used for conducting a switching tube of the three-phase voltage type PWM rectifier according to 6 paths of pulse signals generated by the three-phase current reference instruction so as to enable the voltage of a direct-current bus to stably operate;
the back-stage control module comprises:
the effective value measuring unit (9) is used for measuring the resonance current of the full-bridge resonance LLC conversion circuit;
the double closed loop control unit (10) is used for generating 4 paths of pulse signals according to the direct current bus voltage in voltage stabilization operation and the resonance current of the full-bridge resonance LLC conversion circuit;
and the PWM unit (11) is used for conducting a switching tube of the full-bridge resonant LLC converter according to 4 paths of pulses generated by the voltage of the direct-current bus running in a voltage stabilizing mode and the resonant current of the full-bridge resonant LLC converter, so that the virtual synchronous motor charges the power battery in a constant-current quick-charging mode.
8. The system of claim 7, wherein the electric vehicle off-board charger system comprises: a synchronous power grid formed by synchronous generators with primary voltage regulation and frequency modulation functions; the synchronous power grid is connected with the power battery through the LC filter circuit, the three-phase voltage type PWM rectifier and the full-bridge resonant LLC converter; and the output end of the synchronous power grid is connected with the acquisition module.
9. The system according to claim 7, characterized in that the measurement calculation unit (1) is connected with an excitation control unit (2) and a droop control unit (3), respectively;
the droop control unit (3) is connected with the rotor motion equation unit (4), and the excitation control unit (2) and the rotor motion equation unit (4) are respectively connected with the voltage synthesis unit (5);
the voltage synthesis unit (5) is respectively connected with the stator voltage equation unit (6), the current control unit (7) and the SVPWM unit (8);
and the effective value measuring unit (9) is respectively connected with the double closed-loop control unit (10) and the PWM unit (11).
10. The system according to claim 8 or 7, characterized in that the SVPWM unit (8) is connected in series with a control signal input of the three-phase voltage source PWM rectifier;
and the PWM unit (11) is connected with the control signal input end of the full-bridge resonant LLC converter in series.
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