Fault ride-through control method, device and equipment of electric vehicle charging station considering reactive power support and charging power

Abstract

The application relates to the field of power system fault ride-through, and particularly discloses a fault ride-through control method, device and equipment of an electric vehicle charging station which takes into account reactive power support and charging power. The method comprises the following steps: when detecting that the AC bus voltage of the charging station falls below a preset voltage, the system compares the voltage threshold value, calculates the fault removal time, compares the fault removal time with the main protection action time, dynamically adjusts the control strategy of the double active bridge converter and the voltage source converter of the charging station, prevents the DC voltage from exceeding the limit and protects the battery charging safety, and finally ensures that the charging station stably operates and smoothly recovers during the fault, and completes the fault ride-through process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system fault ride-through, in particular to a kind of electric vehicle charging station fault ride-through control method, device and equipment considering reactive power support and charging power. BACKGROUND

[0002] With the continuous growth of the number of electric vehicles, using power battery as controllable load or mobile energy storage to provide support for power grid is attracting much attention. Electric vehicle charging station generally charges battery through two-stage grid-connected structure of voltage source converter and dual active bridge converter. Under the short-circuit fault of power grid, through the flexible control of voltage source converter (VSC), the charging station can output reactive power to support the voltage of power grid. However, after the fault of power grid, the input power of charging station decreases due to voltage drop, and unbalanced power is generated on the direct current side of charging station, resulting in the decrease of direct current voltage. When the direct current voltage decreases to the limit value, the dual active bridge converter (DAB) is repeatedly unlocked and locked in a short time, and the direct current capacitor is repeatedly charged and discharged, which not only causes impact on the charging system, but also may cause safety problems such as overcharging, overtemperature and explosion of battery due to the frequent and large changes of charging power.

[0003] At present, electric vehicle charging station generally directly disconnects from the grid by triggering low voltage protection under the fault of power grid, and then reconnects to the grid after the voltage recovers. However, direct disconnection not only makes the charging station unable to provide support for the power grid, but also causes the sudden decrease and increase of electric vehicle charging power in a short time due to the short duration of power grid fault, which affects the service life and safety of power battery. At present, there is no related technology of charging station fault ride-through. There has been some research on the use of electric vehicles to provide reactive power for power grid. Researchers have demonstrated the feasibility of electric vehicles providing reactive power support for power grid from the aspects of hardware and control; researchers have analyzed the reactive power compensation capacity of electric vehicles in charging mode through prototype test; researchers have proposed an electric vehicle reactive power optimization method considering the interests of power grid side and user side by establishing a reactive power optimization model. However, the existing researches are all from the perspective of power grid or user operation benefit, and use voltage deviation, network loss and other targets for optimization solution, with control response being minute or hour level, without considering the problem of reactive power support and direct current voltage over-limit of charging station under the fault of power grid.

[0004] The structure of the electric vehicle charging station is similar to the new energy of the inverter interface. The new energy fault ride-through of the inverter interface mainly avoids the over-limit of the DC voltage under the condition of avoiding the over-limit of the DC voltage by means of additional energy storage device, super capacitor, unloading, adjusting the DC side power to realize power rebalancing, and supporting the power grid by the grid-connected converter control output reactive power. The construction cost and operation and maintenance cost of the additional energy storage and super capacitor are high, and they are not suitable for large-scale promotion in the charging station. The active power of the charging station and the active power of the new energy flow in the opposite direction, so that the DC voltage changes in different directions under the power grid fault, and the unloading is useless to prevent the DC voltage of the charging station from falling below the lower limit. Adjusting the charging power of the charging station can inhibit the reduction of the DC voltage, but the change of the charging power may threaten the safety of the electric vehicle. Especially due to the constraint of the AC current limiting, the output reactive power of the voltage source converter often reduces the active power at the cost, which may cause the charging power to change greatly. The fault ride-through of the charging station needs to consider the reduction of the DC voltage, the change of the charging power and the reactive power support, and the existing fault ride-through technology of the new energy cannot be directly applied to the charging station.

[0005] Therefore, how to realize the fault ride-through of the electric vehicle charging station while considering the reactive power support and the charging power has become a problem that those skilled in the art urgently need to solve. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a kind of electric vehicle charging station fault ride-through control method, device and equipment considering reactive power support and charging power, effectively solve the current problem of charging station safety ride-through under fault, provide reference for the fault ride-through of charging station under a large number of electric vehicles.

[0007] In the first aspect of the present application, the present application adopts the following technical solution, a kind of electric vehicle charging station fault ride-through control method considering reactive power support and charging power, applied to electric vehicle charging station, dual active bridge converter and voltage source converter are used in the electric vehicle charging station to realize AC-DC conversion and charging control, the method comprises the following steps:

[0008] S101: real-time acquisition of the AC bus voltage, active and reactive power of the electric vehicle charging station before and after the power grid fault, real-time detection whether the AC bus voltage of the charging station drops to below the preset voltage, if yes, implement S102;

[0009] S102: compare whether the amplitude of the AC bus voltage of the charging station is greater than the voltage threshold value that makes the charging station AC current limiting, if yes, implement S103;If not, implement S104;

[0010] S103: the control of the dual active bridge converter remains unchanged, the voltage source converter adopts DC voltage and reactive power control, the reactive power control reference value is set to Q1, until the AC bus voltage of the charging station is greater than the preset voltage, S109 is implemented;

[0011] S104: according to the AC bus voltage of the charging station, the fault limit trip time for avoiding the over-limit of the DC voltage of the charging station is calculated;

[0012] S105: the fault limit trip time is compared with the main protection action time of the power distribution network, if the fault limit trip time is less than the main protection action time, S106 is implemented; otherwise, S107 is implemented;

[0013] S106: the voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, and the phase shift ratio reference value of the dual active bridge converter is set to D f * until the AC bus voltage of the charging station is greater than the preset voltage, S109 is implemented;

[0014] S107: the voltage source converter adopts active power and reactive power control, the active power and reactive power reference values are set to P2 and Q2, the control of the dual active bridge converter remains unchanged, until the main protection action time, whether the AC bus voltage is greater than the preset voltage is detected, if yes, S109 is implemented; if no, it indicates that the main protection refuses to act, S108 is implemented;

[0015] S108: at the main protection action time, the voltage source converter is switched to DC voltage and reactive power control, the reactive power reference value is set to 0, and the phase shift ratio of the dual active bridge converter is set to D f *;

[0016] S109: the voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, and the phase shift ratio of the dual active bridge converter is set to the reference value before the fault, the charging station fault ride-through is ended;

[0017] Wherein, Q1 is the reactive power under the maximum allowed AC current constraint of the voltage source converter corresponding to the active power of the charging station before the fault, D f * is the phase shift ratio of the dual active bridge converter to make the transmission power just reach the maximum active power of the voltage source converter under the fault, P2 and Q2 are the active power and reactive power at the intersection of the maximum allowed AC current constraint power boundary of the charging station and the DC voltage constraint power boundary of the charging station.

[0018] In the second aspect of the present application, the present application adopts the following technical scheme, a charging station fault ride-through control device for electric vehicles considering reactive power support and charging power, comprising:

[0019] The acquisition module is configured to collect AC bus voltage, active power and reactive power of the electric vehicle charging station before and after the power grid fault;

[0020] The first comparison module is configured to compare the AC bus voltage, and if the AC bus voltage drops below a preset voltage, the second comparison module is invoked. The second comparison module is configured to compare the AC bus voltage amplitude of the charging station with a voltage threshold value for limiting the amplitude of the AC current of the charging station, and if the AC bus voltage amplitude of the charging station is greater than the voltage threshold value for limiting the amplitude of the AC current of the charging station, the first control module is invoked, otherwise the first calculation module is invoked.

[0021] The first control module is configured to keep the control of the dual-active-bridge converter unchanged, and the voltage source converter is controlled by DC voltage and reactive power, the reactive power control reference value is set as Q1, and the first comparison module is invoked to further invoke the fourth control module.

[0022] The first calculation module is configured to calculate a fault limit trip time for avoiding over-limit of the DC voltage of the charging station, and after the calculation is completed, the third comparison module is invoked.

[0023] The third comparison module is configured to compare the fault limit trip time with the main protection action time of the distribution network, and if the fault limit trip time is less than the main protection action time, the second control module is invoked, otherwise the third control module is invoked.

[0024] The second control module is configured to control the voltage source converter by DC voltage and reactive power, the reactive power reference value is set as 0, and the phase-shifted ratio reference value of the dual-active-bridge converter is set as D f , and the first comparison module is invoked to further invoke the fourth control module.

[0025] The third control module is configured to control the voltage source converter by active power and reactive power, the active power and reactive power reference values are set as P2 and Q2, the control of the dual-active-bridge converter is kept unchanged, and the fourth comparison module is invoked.

[0026] The fourth comparison module is configured to compare whether the AC bus voltage at the main protection action time is less than a preset voltage, and if the AC bus voltage is less than the preset voltage, the second control module is invoked, otherwise the fourth control module is invoked.

[0027] The fourth control module is configured to control the voltage source converter by DC voltage and reactive power, the reactive reference value is set as 0, and the phase-shifted ratio of the dual-active-bridge converter is set as the reference value before the fault.

[0028] Q1 is the reactive power of the voltage source converter under the maximum allowed AC current constraint corresponding to the active power of the charging station before the fault, D fP2 and Q2 are active power and reactive power of the intersection of the maximum allowed AC current constraint and the DC voltage constraint of the charging station power boundary for the phase-shifted comparison of the dual active bridge converter transmitting power just reaching the maximum active power of the fault voltage source converter.

[0029] In a third aspect of the present application, the present application adopts the technical solution as follows: an electric vehicle fault ride-through control device considering reactive power support and charging power, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the electric vehicle charging station fault ride-through control method considering reactive power support and charging power according to the first aspect of the present application when executing the computer program.

[0030] In view of the fact that the existing charging station cannot avoid the impact of the fault on the power electronic devices and the battery charging safety while maintaining continuous grid connection during the fault, and provide reactive power support for the power grid, the present application discloses an electric vehicle charging station fault ride-through control method, device and equipment considering reactive power support and charging power, and considering the influence of charging power and DC voltage lower limit on the charging station fault ride-through. Compared with the prior art, the present application has the following advantages:

[0031] 1. The existing technology can use electric vehicles to provide reactive power support for the power grid during normal operation, but mainly focuses on the operation benefits of the power grid or users, and the target and control response time scale is not suitable for the rapid response demand under power grid fault. There is no related technology for the fault ride-through of the charging station under the power grid fault at present, and it is impossible to provide reactive power support as much as possible while ensuring the safety of the charging station DC voltage and charging safety.

[0032] 2. The existing fault ride-through technologies for inverter interface new energy sources such as using additional energy storage, super capacitor or unloading have problems such as high cost, complex operation and maintenance or unsuitable principle, and cannot be applied to charging stations.

[0033] 3. The existing fault ride-through technologies of power electronic equipment do not consider the balance between DC voltage reduction, charging power variation and reactive power support, and cannot be directly applied to charging stations, and cannot provide maximum reactive support while ensuring the safety of electric vehicle charging. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The flow chart of the electric vehicle charging station fault ride-through control method considering reactive power support and charging power of the embodiment of the present application;

[0035] Figure 2 The structure schematic diagram of the electric vehicle charging station fault ride-through control device considering reactive power support and charging power of the embodiment of the present application;

[0036] Figure 3 This is a diagram of the main circuit topology of an electric vehicle charging station used in an embodiment of the present invention.

[0037] Figure 4 This is a schematic diagram of electrical quantities for embodiment 1 of the present invention;

[0038] Figure 5 This is a schematic diagram of electrical quantities for embodiment 2 of the present invention;

[0039] Figure 6 This is a schematic diagram of electrical quantities for embodiment 3 of the present invention;

[0040] Figure 7 This is a schematic diagram of electrical quantities for embodiment 4 of the present invention. Detailed Implementation

[0041] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] The present invention will now be described in further detail with reference to the accompanying drawings.

[0043] Please see Figure 1 ,like Figure 1 The flowchart shown illustrates a fault ride-through control method for electric vehicle charging stations that balances reactive power support and charging power, provided by an embodiment of the present invention. This method is applied to electric vehicle charging stations, which include at least dual active bridge converters and voltage source converters. The method comprises the following steps:

[0044] S101: Real-time acquisition of AC bus voltage, active power and reactive power of charging station, real-time detection of whether AC bus voltage of charging station drops below preset voltage, if so, implement S102;

[0045] S102: Compare whether the amplitude of the AC bus voltage of the charging station is greater than the voltage threshold value that limits the AC current of the charging station. If yes, then proceed to S103; otherwise, proceed to S104.

[0046] S103: The control of the dual active bridge converter of the charging station remains unchanged. The voltage source converter adopts DC voltage and reactive power control. The reactive power control reference value is set to Q1 until the AC bus voltage of the charging station is greater than the preset voltage, then execute S109.

[0047] S104: According to the charging station AC bus voltage, the fault limit trip time for avoiding the over-limit of the charging station DC voltage is calculated;

[0048] S105: The fault limit trip time is compared with the main protection action time of the power distribution network. If the fault limit trip time is less than the main protection action time, S106 is implemented; otherwise, S107 is implemented.

[0049] S106: The voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, and the phase shift ratio reference value of the dual active bridge converter is set to D f * until the charging station AC bus voltage is greater than the preset voltage, and S109 is implemented.

[0050] S107: The voltage source converter adopts active power and reactive power control, the active power and reactive power reference values are set to P2 and Q2, and the dual active bridge converter control remains unchanged until the main protection action time. It is detected whether the AC bus voltage is greater than the preset voltage. If yes, S109 is implemented; if no, it indicates that the main protection refuses to act, and S108 is implemented.

[0051] S108: At the main protection action time, the charging station voltage source converter is switched to DC voltage and reactive power control, the reactive power reference value is set to 0, and the phase shift ratio of the dual active bridge converter is set to D f *;

[0052] The main protection action time refers to the time point or time range of the entire process from the occurrence of a fault in a power device (such as a charging station voltage source converter, a dual active bridge converter, etc.) to the completion of fault removal (such as tripping) by the main protection device configured.

[0053] S109: The charging station voltage source converter adopts DC voltage and reactive power control, the reactive reference value is set to 0, and the phase shift ratio of the dual active bridge converter is set to the reference value before the fault, and the charging station fault ride-through is ended.

[0054] In specific implementation, in step S101, some electrical parameter measuring instruments such as power analyzers and power quality analyzers can be used to measure the voltage, current, active power, and reactive power of the charging station AC bus in real time. For example, a resistance voltage divider or an isolated voltage sensor is used to collect the DC bus voltage of the DAB, which is not limited in the art.

[0055] In the embodiment of the present application, in step S101, the preset voltage can be 0.95p.u times rated voltage, which can intuitively reflect the voltage deviation, for example, if the rated voltage of the bus of a certain charging station is 110kV, 0.95p.u times rated voltage is 110*0.95=104.5kV. If the actual bus voltage is close to this value, it means that the AC bus voltage of the charging station has been reduced to a certain extent, but it is still within the acceptable range; if it deviates greatly, step S102 needs to be implemented to ensure the normal operation of the equipment.

[0056] In specific implementation, in step S102, the voltage threshold value for limiting the AC current of the charging station is the minimum AC bus voltage that can make the active power of the charging station after the fault return to the value before the fault, which is determined by the active power of the charging station before the fault and the maximum allowable AC current of the voltage source converter, and the calculation method includes:

[0057] According to the product of the maximum allowable AC current coefficient of the voltage source converter and the rated AC current of the voltage source converter, the maximum AC current value that can be borne by the voltage source converter is calculated,

[0058] According to the ratio of the active power of the charging station before the fault to the maximum AC current value that can be borne by the voltage source converter, the voltage threshold value for limiting the AC current of the charging station is calculated.

[0059] In some embodiments, the voltage threshold value for limiting the AC current of the charging station is calculated by the following formula:

[0060]

[0061] Wherein, P0 is the active power of the charging station before the fault; K I is the maximum allowable AC current coefficient of the voltage source converter; I N is the rated AC current of the voltage source converter.

[0062] The embodiment of the present application considers the maximum allowable AC current limitation, prevents the AC current of the charging station from exceeding the bearing capacity of the converter in the fault condition, prolongs the service life of the power electronic equipment, and reduces the maintenance cost. Through the ratio of the active power of the charging station before the fault to the maximum AC current value that can be borne by the voltage source converter, the voltage threshold value can be reasonably set to ensure that the charging station can return to the active power level before the fault after the fault.

[0063] In specific implementation, in step S103, the reactive power reference value Q1 of the voltage source converter is the reactive power under the maximum allowable AC current constraint of the voltage source converter corresponding to the active power of the charging station before the fault, and the calculation method includes:

[0064] The maximum instantaneous apparent power of the voltage source converter allowed to output at the fault moment is calculated according to the product of the amplitude of the AC bus voltage at the fault moment, the maximum allowed AC current coefficient of the voltage source converter and the rated AC current of the voltage source converter;

[0065] The reactive power of the charging station before the fault corresponding to the maximum allowed AC current constraint of the voltage source converter is calculated according to the square root of the difference between the square of the maximum instantaneous apparent power of the voltage source converter allowed to output at the fault moment and the square of the active power of the charging station before the fault.

[0066] In some embodiments, the reactive power of the charging station before the fault corresponding to the maximum allowed AC current constraint of the voltage source converter is calculated by the following formula:

[0067]

[0068] In the formula, (U f K I I N ) is used to represent the maximum instantaneous apparent power of the voltage source converter allowed to output at the fault moment, U f is the amplitude of the AC bus voltage at the fault moment.

[0069] In the embodiments of the present application, the maximum allowed AC current limit is considered to prevent the AC current of the charging station from exceeding the bearing capacity of the converter in the fault condition, and by reasonably setting the reactive power reference value, it is ensured that the charging station can recover to the active power level before the fault after the fault.

[0070] In specific implementation, in step S104, the fault limit removal time for avoiding the over-limit of the DC voltage of the charging station is the fault duration time when the power boundary of the charging station with the maximum allowed AC current constraint is tangent to the power boundary of the charging station with the DC voltage constraint, and is determined by the DC voltage reference value, the critical value of the DC voltage, the DC capacitor, the amplitude of the AC bus voltage at the fault moment, the transmission power of the dual active bridge converter under the fault, the maximum allowed AC current of the voltage source converter, and the calculation method includes:

[0071] According to the DC voltage reference value, the critical voltage of the dual active bridge converter lockout and the bus capacitor of the charging station, the energy difference released when the bus capacitor of the charging station discharges from the DC voltage reference value to the critical voltage of the dual active bridge converter lockout is calculated;

[0072] According to the amplitude of the AC bus voltage at the fault moment, the maximum allowed AC current coefficient of the voltage source converter, the square of the rated AC current of the voltage source converter and the total transmission power of the dual active bridge converter in the charging station under the fault, the power of the charging station with the maximum current output is calculated.

[0073] The fault limit trip time for avoiding overvoltage of the charging station is calculated according to a ratio of an energy difference released by discharging of the DC voltage reference value of the charging station bus capacitor to a critical voltage of the dual active bridge converter being blocked to a power output by the charging station at a maximum current.

[0074] In some embodiments, the fault limit trip time for avoiding overvoltage of the charging station is calculated by the following formula:

[0075]

[0076] In the formula, C is the charging station bus capacitor; is the DC voltage reference value; U dc,th is the critical voltage of the dual active bridge converter being blocked, generally 0.5 p.u. rated voltage; P s,f is the total transmission power of the dual active bridge converter in the charging station under fault, which represents the battery charging power in the charging station.

[0077] In specific implementation, in step S106, the phase shift ratio reference value D f of the dual active bridge converter is the phase shift ratio that makes the transmission power of the dual active bridge converter just reach the maximum active power of the voltage source converter under fault. The calculation method includes:

[0078] The transmission power of the dual active bridge converter is calculated according to the energy storage inductance of the dual active bridge converter, the switching frequency of the dual active bridge converter, and the turns ratio of the high-voltage side and the low-voltage side of the dual active bridge converter.

[0079] The maximum active power of the voltage source converter is calculated according to the ohmic internal resistance of the electric vehicle battery, the constant voltage of the battery, the polarization voltage constant of the battery, the capacity of the battery, the amplitude and time constant inverse of the voltage drop in the exponential region of the typical discharge curve of the battery, the state of charge of the battery, and the number of electric vehicles in the charging station at the time of fault.

[0080] The phase shift ratio that makes the transmission power of the dual active bridge converter just reach the maximum active power of the voltage source converter under fault is solved by simultaneously solving the transmission power of the dual active bridge converter and the maximum active power of the voltage source converter.

[0081] In some embodiments, the phase shift ratio that makes the transmission power of the dual active bridge converter just reach the maximum active power of the voltage source converter under fault is calculated by the following formula:

[0082]

[0083] In the formula, a1 is a first parameter, a2 is a second parameter, and a3 is a third parameter. is a DC voltage reference value.

[0084] In implementation, the first, second and third parameters are calculated by the charging station parameters:

[0085]

[0086] wherein, L r is an energy storage inductor of the dual active bridge converter; f s is a switching frequency of the dual active bridge converter; n is a turns ratio of a high-voltage side coil to a low-voltage side coil of the dual active bridge converter; R ba is an ohmic internal resistance of the electric vehicle battery; E0 is a constant voltage of the battery; K is a polarization voltage constant of the battery; Q c is a capacity of the battery; A ba , B ba are respectively an amplitude and an inverse time constant of a voltage drop in an exponential region of a typical discharge curve of the battery; soc is a state of charge of the battery; and N is a number of electric vehicles in the charging station at the time of the fault.

[0087] In implementation, in step S107, the active power and reactive power reference values P2 and Q2 of the voltage source converter are active power and reactive power at an intersection of a maximum allowed AC current constrained charging station power boundary and a DC voltage constrained charging station power boundary, and the calculation method comprises:

[0088] According to the active power of the charging station before the fault, the DC voltage reference value, the critical voltage of the blocking of the dual active bridge converter, the bus capacitance of the charging station and the main protection action time, the active power at the intersection of the maximum allowed AC current constrained charging station power boundary and the DC voltage constrained charging station power boundary is calculated.

[0089] According to the amplitude of the AC bus voltage at the moment of the fault, the maximum allowed AC current coefficient of the voltage source converter, the square of the rated AC current of the voltage source converter and the square root of the square of the active power at the intersection of the maximum allowed AC current constrained charging station power boundary and the DC voltage constrained charging station power boundary, the reactive power at the intersection of the maximum allowed AC current constrained charging station power boundary and the DC voltage constrained charging station power boundary is calculated.

[0090] In some embodiments, the calculation formulas of the active power and reactive power reference values P2 and Q2 of the voltage source converter, which are the active power and reactive power at the intersection of the maximum allowed AC current constrained charging station power boundary and the DC voltage constrained charging station power boundary, are as follows:

[0091]

[0092] Wherein, P2 is the active power of the charging station power boundary intersection point of the maximum allowed alternating current constraint and the direct current voltage constraint, Q2 is the reactive power of the charging station power boundary intersection point of the maximum allowed alternating current constraint and the direct current voltage constraint; P0 is the active power of the charging station before the fault; C is the charging station bus capacitance; U is the direct current voltage reference value; U dc,th is the critical voltage of the double active bridge converter lockout; t1 is the main protection action time; U f is the alternating current bus voltage amplitude at the fault moment; K I is the maximum allowed alternating current coefficient of the voltage source converter; I N is the rated alternating current of the voltage source converter.

[0093] The embodiment of the application considers the maximum allowed alternating current and the direct current voltage constraint when determining P2 and Q2, so that the equipment can be prevented from being damaged due to overcurrent or overvoltage, the service life of the equipment is prolonged, and the maintenance cost is reduced; by reasonably determining the P2 and Q2 reference values, it is ensured that the charging station can meet the alternating current and direct current voltage constraints in the running process and stably output the required active and reactive power, and maintain its normal charging service function.

[0094] Please refer to Figure 2 , Figure 2 It is a kind of electric vehicle charging station fault ride-through control device structure schematic diagram that considers reactive support and charging power, comprising:

[0095] The acquisition module is used to collect the alternating current bus voltage, active and reactive power of the electric vehicle charging station before and after the power grid fault;

[0096] The first comparison module is used to compare the alternating current bus voltage, and if the alternating current bus voltage drops below the preset voltage, the second comparison module is called; the second comparison module is used to compare the alternating current bus voltage amplitude of the charging station with the voltage threshold value that makes the alternating current of the charging station current limiting, and if the alternating current bus voltage amplitude of the charging station is greater than the voltage threshold value that makes the alternating current of the charging station current limiting, the first control module is called, otherwise the first calculation module is called;

[0097] The first control module is used to keep the control of the double active bridge converter unchanged, and the voltage source converter adopts direct current voltage and reactive power control, the reactive power control reference value is set to Q1, and the first comparison module is called to call the fourth control module;

[0098] The first calculation module is used to calculate the fault limit trip time for avoiding the over-limit of the direct current voltage of the charging station, and after the calculation is completed, the third comparison module is called;

[0099] The third comparison module is used to compare the fault clearance time with the main protection action time of the distribution network. If the fault clearance time is less than the main protection action time, the second control module is called; otherwise, the third control module is called.

[0100] The second control module uses DC voltage and reactive power control for the voltage source converter, with the reactive power reference value set to 0. The shift ratio reference value for the dual active bridge converter is set to D. f * and then call the first comparison module and then the fourth control module;

[0101] The third control module uses active and reactive power control for the voltage source converter. The active and reactive power reference values ​​are set to P2 and Q2, respectively. The control of the dual active bridge converter remains unchanged, and the fourth comparison module is called.

[0102] The fourth comparison module is used to compare whether the AC bus voltage is less than the preset voltage at the time of the main protection action. If it is less than the preset voltage, the second control module is called; otherwise, the fourth control module is called.

[0103] The fourth control module, the voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, and the shift ratio of the dual active bridge converter is set to the reference value before the fault.

[0104] Where Q1 is the reactive power of the voltage source converter under the maximum allowable AC current constraint corresponding to the active power of the charging station before the fault, and D f *To ensure that the power transmitted by the dual active bridge converter just reaches the shift ratio of the maximum active power of the voltage source converter under fault conditions, P2 and Q2 are the active power and reactive power at the intersection of the charging station power boundary constrained by the maximum allowable AC current and the charging station power boundary constrained by the DC voltage.

[0105] The embodiments of the present invention, through the combination of an acquisition module, multiple comparison modules, and multiple control modules, fully consider the balance between DC voltage reduction, charging power variation, and reactive power support, and can be directly applied to electric vehicle charging stations, providing maximum reactive power support while ensuring the safety of electric vehicle charging.

[0106] In an embodiment of the present invention, the electric vehicle fault ride control device that balances reactive power support and charging power includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the electric vehicle charging station fault ride control method that balances reactive power support and charging power as described in the present invention.

[0107] In some embodiments, the memory may include non-persistent memory in a computer-readable medium, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0108] In this embodiment of the invention, the system is built in MATLAB / Simulink. Figure 3 The simulation model shown verifies the correctness and effectiveness of the theoretical analysis and the proposed solution. There are four electric vehicles in the charging station. The charging station is connected to the power distribution network via a 0.380 / 10kV transformer. The rated DC voltage is 800V, and the outer loop control parameter k of the voltage source converter is... p =1, k i =50. The parameters of the dual active bridge converter are k vp =0.0005, k vi =20, L r It is 20e-6H, f s =10000Hz, n=800 / 420. The reference voltage for each electric vehicle battery pack under constant voltage charging is 415V, and under constant current charging it is 380A. The maximum allowable AC current factor of the voltage source converter is 1.2, and the rated current is 1440A. The blocking voltage of the dual active bridge converter is 0.55pu. The main protection action time of the distribution network is 0.4s, and the backup protection action time is 1s. Under normal operation, two electric vehicles are charged at constant current, and two electric vehicles are charged at constant voltage. The transmission power of the dual active bridge converter is 1.0pu, and the reactive power of the voltage source converter is 0p.u. The control method proposed in this paper is verified by setting up three comparison groups: Method 1 adopts DC voltage control and constant reactive power control for the voltage source converter, and the dual active bridge converter maintains the constant current / constant voltage control before the fault; Method 2 refers to the fault ride-through requirements of new energy, and controls the reactive power of the voltage source converter according to the voltage drop degree. The reactive power reference value is 1.5(0.9-U). f )I N The active power reference value is the smaller of the maximum instantaneous apparent power that the voltage source converter can output at the moment of the fault and the active power before the fault; Method 3 is the method of the present invention.

[0109] Embodiment 1 of the present invention: When the voltage source converter current is not limited

[0110] Assume a three-phase short-circuit fault occurs in the distribution network at 0.3 seconds. After the fault, the AC bus voltage is as follows: Figure 4As shown in (a), the AC bus voltage of the charging station drops to 0.85 pu. According to the calculation method of the voltage threshold value for AC current limiting of the charging station, the AC bus voltage threshold value at which the voltage source converter can restore the active power before the fault is 0.83 pu. After the fault, the AC bus voltage of the charging station is greater than the threshold voltage, and the current of the voltage source converter is not limited. The active and reactive power reference values ​​for method 2 are 1.01 pu and 0.064 pu, respectively; the reactive power reference value for method 3 is 0.65 pu. Simulation results show the AC bus voltage, DC voltage, active and reactive power of the voltage source converter, and transmission power of the dual active bridge converter under the three methods as follows: Figure 4 As shown in the image.

[0111] like Figure 4 (b) and Figure 4 As shown in (c), since the AC current is not limited, the active power of the voltage source converter can be restored to the pre-fault power in all three methods. Therefore, the DC voltage fluctuation is small and does not exceed the limit. However, the reactive power provided by the charging station differs significantly among the three methods. Figure 4 As shown in (d), Method 1 maintains normal operation with the charging station not generating reactive power. In Method 2, due to the shallow AC bus voltage drop, the charging station only generates 0.064 pu of reactive power, failing to fully utilize its reactive capacity. In Method 3, the charging station generates a maximum of 0.65 pu of reactive power. Method 3 accurately characterizes the feasible power domain of the charging station, thus fully utilizing its reactive capacity. Figure 4 As shown in (a), the AC bus voltage during the fault period in Method 3 rises from 0.85 pu to 0.875 pu, while the AC bus voltage in Methods 1 and 2 remains around 0.85 pu. Figure 4 As shown in (e), the transmission power of the dual active bridge converter is basically the same under the three methods. The improvement of voltage source converter control in method 3 does not affect the charging of electric vehicles during faults. When the voltage drop is small, the present invention can better support the AC bus voltage while avoiding DC voltage over-limit and charging power changes.

[0112] Scheme 2 of this invention: The fault limit clearing time is greater than the main protection action time and the main protection operates correctly.

[0113] After the fault, the AC bus voltage of the charging station dropped to 0.7 pu. Figure 5As shown in (a), the AC bus voltage is less than the threshold voltage, and the voltage source converter current is limited. The reference values ​​for active and reactive power of the voltage source converter in Method 2 are 0.81 pu and 0.21 pu, respectively. Based on the fault limit clearing time calculation method, the fault calculation time is 132 ms, which is greater than the main protection action time. According to P2 and Q2, the reference values ​​for active and reactive power of the voltage source converter in Method 3 are 0.72 pu and 0.43 pu, respectively. The AC bus voltage, DC voltage, active and reactive power of the voltage source converter, and transmission power of the dual active bridge converter are shown in the figures for the three methods. Figure 5 As shown.

[0114] like Figure 5 As shown in (b), the DC voltage did not exceed the limit under all three methods. In method 3, the DC voltage dropped to 0.55 pu, which just reached the latch-up value of the dual active bridge converter, thus verifying the correctness of the charging station's power feasible region. Figure 5 As shown in (c) and 5(d), under Method 1, the active power during the fault period is 0.84 pu. To restore active power, the d-axis current of Method 1 is the voltage source converter limiting current, therefore the output reactive power is 0. Method 2 prioritizes reactive power control and outputs 0.21 pu of reactive power based on the AC bus voltage drop, thus the active power of the voltage source converter is reduced compared to Method 1. Method 3 outputs 0.43 pu of reactive power, a significant increase compared to Methods 1 and 2. Although Method 3 has the lowest active power of the voltage source converter, as... Figure 5 (b) and Figure 5 As shown in (d), because the safety margin of the charging station's DC voltage during the main protection's operating time was accurately characterized, the DC voltage did not exceed the limit and provided greater reactive power. Figure 5 As shown in (a), under method 3, the AC bus voltage increases from 0.7 pu to 0.74 pu during the fault, while the AC bus voltages under methods 2 and 1 remain at 0.71 pu and 0.70 pu, respectively. Figure 5 As shown in (e), the DC voltage drop has minimal impact on the transmission power of the dual active bridge converter under all three methods, essentially maintaining the transmission power at the pre-fault level. The improvement in voltage source converter control in Method 3 does not affect the charging of electric vehicles during the fault. The proposed method can better support the AC bus voltage while avoiding DC voltage overshoot and charging power variations.

[0115] Scheme 3 of this invention: The fault clearance time is greater than the main protection operation and the main protection fails to operate.

[0116] The fault conditions remain unchanged, such as Figure 4As shown in (a), after the fault, the AC bus voltage of the charging station dropped to 0.7 pu. However, the main protection failed to operate, and the fault was cleared by the backup protection. The control reference values ​​for Method 1 and Method 2 are the same as those for Case 2, and the control reference value for Method 3 before the main protection operation time is also the same as that for Case 2. Method 3 detects that the fault has not been cleared at 0.4s and then restores the DC voltage control of the voltage source converter, while adjusting the shift ratio of the dual active bridge converter to 0.0669. The DC voltage of the charging station, the AC bus voltage, the active and reactive power of the voltage source converter, and the transmission power of the dual active bridge converter are as follows: Figure 6 As shown.

[0117] like Figure 6 As shown in (b), the DC voltage in Method 1 and Method 2 drops to the blocking value of the dual active bridge converter at 0.43s and 0.41s, respectively, and then the capacitor repeatedly charges and discharges, causing the DC voltage to oscillate continuously. In Method 3, the active power of the voltage source converter and the transmission power of the dual active bridge converter are balanced again at 0.4s, and the DC voltage just reaches the blocking value of the dual active bridge converter. Subsequently, the DC voltage in Method 3 gradually recovers to the reference value, avoiding the blocking of the dual active bridge converter, as shown in the figure. Figure 6 As shown in (b). Figure 6 (c) and Figure 6 In (d), since the d-axis current is the limiting current of the voltage source converter, the active power of the voltage source converter in Method 1 is the highest during the fault, reaching 0.84 pu, but the output reactive power is 0. The active power of the voltage source converter in Method 2 is 0.81 pu, lower than Method 1, and the output reactive power is 0.21 pu. Before the main protection fails to operate, Method 3 provides more reactive power than Method 1 and Method 2, with an output reactive power of 0.43 pu; the active power of Method 3 is 0.72 pu, slightly less than Method 1 and Method 2, but at this time the transmission power of the dual active bridge converter is close to that of Method 1 and Method 2, both maintaining the power level before the fault. Figure 6 As shown in (e), after the main protection fails to operate, the transmission power of the dual active bridge converter in method 3 decreases to approximately 0.84 pu. However, in methods 1 and 2, due to the repeated unlocking and de-locking of the dual active bridge converter, the transmission power decreases sharply and oscillates continuously near 0, seriously threatening the safety of electric vehicles. This invention can better support the AC bus voltage while avoiding DC voltage over-limits and charging power changes before the main protection fails to operate, and even if the main protection fails to operate, it can still avoid DC voltage over-limits and large changes in charging power.

[0118] Scheme 4 of this invention: The fault clearance time is less than the main protection action time.

[0119] After a power distribution network fault, the AC bus voltage at the charging station dropped to 0.65 pu. Figure 7 As shown in (b). The active and reactive power reference values ​​for the voltage source converter in Method 2 are 0.74 pu and 0.24 pu, respectively. After the fault, the AC bus voltage of the charging station is less than the threshold voltage. Based on the fault limit clearing time calculation method, the fault limit clearing time is 73 ms, which is less than the main protection action time. Based on the shift ratio reference value calculation method, the shift ratio reference value for the dual active bridge converter in Method 3 is 0.0669, and the reactive power reference value for the voltage source converter is 0. The electrical quantities of the charging station are as follows: Figure 7 As shown.

[0120] Because the AC bus voltage of the charging station drops significantly, such as Figure 7 As shown in (a), the constant voltage control of Method 1 cannot restore the active power of the voltage source converter. At 0.37s, the DC voltage drops to the latch-up value of the dual active bridge converter, as... Figure 7 As shown in (b) and 7(c). The output reactive power under Method 2 is 0.24 pu, as... Figure 7 As shown in (d). To provide more reactive power, Method 2 results in a lower active power of the voltage source converter during the fault, reaching 0.74 pu. Therefore, the DC voltage of Method 2 drops to the blocking value of the dual active bridge converter at 0.35s, which is faster than Method 1. In Method 3, the DC voltage drops due to the reduced output power of the voltage source converter at the moment of the fault. As the transmission power of the dual active bridge converter decreases, the DC voltage recovers quickly, without exceeding the limit and with a relatively small change. Figure 7 As shown in (c), the active power of the voltage source converters of the three methods is similar. However, as Figure 7 As shown in (e), due to DC voltage blocking, the transmission power of the dual active bridge converters in methods 1 and 2 drops sharply to near zero and oscillates continuously, severely affecting the safety of the electric vehicle charging circuit and battery pack. Method 3 reduces the transmission power of the dual active bridge converter, but the maximum change is only 0.22 pu. This invention minimizes the variation in charging power while avoiding DC voltage exceeding limits.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described with reference to preferred embodiments, those skilled in the art should understand that various changes in form and detail can be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A fault ride-through control method for electric vehicle charging stations that balances reactive power support and charging power, characterized in that, This method is applied to electric vehicle charging stations, where dual active bridge converters and voltage source converters are used to achieve AC / DC conversion and charging control. The method includes the following steps: S101: Real-time acquisition of AC bus voltage, active and reactive power of electric vehicle charging stations before and after power grid faults; real-time detection of whether AC bus voltage of charging stations drops below the preset voltage; if so, implement S102. S102: Compare whether the amplitude of the AC bus voltage of the charging station is greater than the voltage threshold value that limits the AC current of the charging station. If yes, then proceed to S103; otherwise, proceed to S104. S103: The control of the dual active bridge converter remains unchanged. The voltage source converter adopts DC voltage and reactive power control. The reactive power control reference value is set to Q1 until the AC bus voltage of the charging station is greater than the preset voltage, and then S109 is implemented. S104: Calculate the fault clearance time to avoid DC voltage exceeding the limit of the charging station based on the AC bus voltage of the charging station. S105: Compare the fault clearance time with the main protection operation time of the distribution network. If the fault clearance time is less than the main protection operation time, then implement S106; otherwise, implement S107. S106: The voltage source converter uses DC voltage and reactive power control, with the reactive power reference value set to 0. The shift ratio reference value of the dual active bridge converter is set to... Until the AC bus voltage of the charging station is greater than the preset voltage, S109 is implemented. S107: The voltage source converter adopts active power and reactive power control. The active power and reactive power reference values ​​are set to P2 and Q2. The dual active bridge converter control remains unchanged until the main protection operates. It checks whether the AC bus voltage is greater than the preset voltage. If yes, S109 is implemented; if no, it indicates that the main protection fails to operate and S108 is implemented. S108: When the main protection operates, the voltage source converter switches to DC voltage and reactive power control, the reactive power reference value is set to 0, and the shift ratio of the dual active bridge converter is set to... ; S109: The voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, the shift ratio of the dual active bridge converter is set to the reference value before the fault, and the charging station fault ride-through ends. Where Q1 represents the reactive power of the voltage source converter under the maximum allowable AC current constraint corresponding to the active power of the charging station before the fault. To ensure that the power transmitted by the dual active bridge converter just reaches the shift ratio of the maximum active power of the voltage source converter under fault conditions, P2 and Q2 are the active power and reactive power at the intersection of the charging station power boundary constrained by the maximum allowable AC current and the charging station power boundary constrained by the DC voltage.

2. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 1, characterized in that, In S102, the calculation method for the voltage threshold value of the AC bus that limits the AC current of the charging station includes: The maximum AC current that the voltage source converter can withstand is calculated by multiplying the maximum permissible AC current coefficient of the voltage source converter by the rated AC current of the voltage source converter. Based on the ratio of the active power of the charging station before the fault to the maximum AC current that the voltage source converter can withstand, the voltage threshold value that limits the AC current of the charging station is calculated.

3. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 1, characterized in that, In S103, the calculation method for the reactive power under the maximum allowable AC current constraint of the voltage source converter corresponding to the active power of the charging station before the fault includes: The maximum instantaneous apparent power that the voltage source converter can output at the moment of the fault is calculated by multiplying the AC bus voltage amplitude at the instant of the fault, the maximum allowable AC current coefficient of the voltage source converter, and the rated AC current of the voltage source converter. The reactive power of the voltage source converter under the maximum allowable AC current constraint corresponding to the active power of the charging station before the fault is calculated by taking the square root of the difference between the square of the maximum instantaneous apparent power allowed to be output by the voltage source converter at the moment of the fault and the square of the active power of the charging station before the fault.

4. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 1, characterized in that, In S104, the calculation method for the fault clearance limit to avoid DC voltage exceeding the charging station limit includes: Based on the DC voltage reference value, the critical voltage of the dual active bridge converter lockout, and the charging station bus capacitor, the energy difference released by the charging station bus capacitor from the DC voltage reference value to the critical voltage of the dual active bridge converter lockout is calculated. Based on the AC bus voltage amplitude at the moment of the fault, the maximum allowable AC current coefficient of the voltage source converter, the square of the rated AC current of the voltage source converter, and the total transmission power of the dual active bridge converters in the charging station under the fault, the power output of the charging station at the maximum current is calculated. The fault clearance time to avoid DC voltage exceeding the limit of the charging station is calculated based on the ratio of the energy difference released by the charging station bus capacitor from the DC voltage reference value to the critical voltage of the dual active bridge converter lockout to the power output of the charging station at maximum current.

5. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 1, characterized in that, In S106, the calculation method for the shift ratio that makes the transmission power of the dual active bridge converter just reach the maximum active power of the voltage source converter under fault conditions includes: The transmission power of the dual active bridge converter is calculated based on the energy storage inductance, switching frequency, and turns ratio of the high-voltage and low-voltage coils of the dual active bridge converter. The maximum active power of the voltage source converter is calculated based on the ohmic internal resistance of the electric vehicle battery, the constant voltage of the battery, the polarization voltage constant of the battery, the battery capacity, the magnitude of the voltage drop in the exponential region of the typical discharge curve of the battery and the reciprocal of the time constant, the state of charge of the battery, and the number of electric vehicles in the charging station when the fault occurs. Based on the transmission power of the dual active bridge converter and the maximum active power of the voltage source converter, a shift ratio is obtained by simultaneously solving the equations to ensure that the transmission power of the dual active bridge converter just reaches the maximum active power of the voltage source converter under fault conditions.

6. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 5, characterized in that, In S106, the calculation formula for the shift ratio that makes the transmission power of the dual active bridge converter just reach the maximum active power of the voltage source converter under fault conditions is expressed as follows: In the formula, To ensure that the power transmitted by the dual active bridge converter just reaches the shift ratio of the maximum active power of the voltage source converter under fault conditions, As the first parameter, For the second parameter, It is the third parameter; This is a reference value for DC voltage. The energy storage inductor is for a dual active bridge converter; The switching frequency of the dual active bridge converter; The turns ratio of the high-voltage side to the low-voltage side coils in a dual active bridge converter; The internal resistance of an electric vehicle battery is ohmic. K is the constant voltage of the battery; K is the battery polarization voltage constant. Battery capacity; , These are the magnitude of the voltage drop in the exponential region of a typical battery discharge curve and the reciprocal of the time constant, respectively. Let N be the state of charge of the battery of the i-th electric vehicle; N is the number of electric vehicles in the charging station when the fault occurs. K represents the amplitude of the AC bus voltage at the moment of the fault. I This is the maximum permissible AC current coefficient for the voltage source converter; This is the rated AC current of the voltage source converter.

7. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 1, characterized in that, In S107, the calculation methods for the active and reactive power at the intersection of the charging station power boundary with the maximum allowable AC current constraint and the charging station power boundary with the DC voltage constraint include: Based on the active power of the charging station before the fault, the reference value of DC voltage, the critical voltage of the dual active bridge converter blocking, the bus capacitance of the charging station, and the action time of the main protection, the active power at the intersection of the charging station power boundary constrained by the maximum allowable AC current and the charging station power boundary constrained by the DC voltage is calculated. The reactive power at the intersection of the AC bus voltage amplitude at the moment of fault, the maximum allowable AC current coefficient of the voltage source converter, the square of the rated AC current of the voltage source converter, and the arithmetic root of the square of the active power at the intersection of the charging station power boundary constrained by the maximum allowable AC current and the charging station power boundary constrained by the DC voltage are calculated.

8. The electric vehicle charging station fault ride-through control method that takes into account both reactive power support and charging power according to claim 7, characterized in that, In S107, the formulas for calculating the active and reactive power at the intersection of the charging station power boundary with the maximum allowable AC current constraint and the charging station power boundary with the DC voltage constraint are as follows: Where P2 is the active power at the intersection of the charging station power boundary with maximum allowable AC current constraint and the charging station power boundary with DC voltage constraint; Q2 is the reactive power at the intersection of the charging station power boundary with maximum allowable AC current constraint and the charging station power boundary with DC voltage constraint; P0 is the active power of the charging station before the fault; and C is the charging station bus capacitance. This is a reference value for DC voltage. This is the critical voltage for the dual active bridge converter to be locked out. This refers to the timing of the primary protection action; K represents the amplitude of the AC bus voltage at the moment of the fault. I This is the maximum permissible AC current coefficient for the voltage source converter; This is the rated AC current of the voltage source converter.

9. A fault ride-through control device for electric vehicle charging stations that combines reactive power support and charging power, characterized in that, include: The acquisition module is used to collect AC bus voltage, active power and reactive power of electric vehicle charging stations before and after power grid faults. The first comparison module is used to compare the AC bus voltage. If the AC bus voltage drops below the preset voltage, the second comparison module is called. The second comparison module is used to compare the amplitude of the AC bus voltage of the charging station with the voltage threshold value that limits the AC current of the charging station. If the amplitude of the AC bus voltage of the charging station is greater than the voltage threshold value that limits the AC current of the charging station, the first control module is called; otherwise, the first calculation module is called. The first control module maintains the same control for the dual active bridge converters. The voltage source converter uses DC voltage and reactive power control, with the reactive power control reference value set to Q1. The first comparison module is then called, followed by the fourth control module. The first calculation module is used to calculate the fault clearance time to avoid DC voltage exceeding the limit of the charging station. After the calculation is completed, the third comparison module is called. The third comparison module is used to compare the fault clearance time with the main protection action time of the distribution network. If the fault clearance time is less than the main protection action time, the second control module is called. Otherwise, invoke the third control module; The second control module uses DC voltage and reactive power control for the voltage source converter, with the reactive power reference value set to 0. The shift ratio reference value for the dual active bridge converter is set to... And then call the first comparison module and then the fourth control module; The third control module uses active and reactive power control for the voltage source converter. The active and reactive power reference values ​​are set to P2 and Q2, respectively. The control of the dual active bridge converter remains unchanged, and the fourth comparison module is called. The fourth comparison module is used to compare whether the AC bus voltage is less than the preset voltage at the time of the main protection action. If it is less than the preset voltage, the second control module is called; otherwise, the fourth control module is called. The fourth control module, the voltage source converter adopts DC voltage and reactive power control, the reactive power reference value is set to 0, and the shift ratio of the dual active bridge converter is set to the reference value before the fault. Where Q1 represents the reactive power of the voltage source converter under the maximum allowable AC current constraint corresponding to the active power of the charging station before the fault. To ensure that the power transmitted by the dual active bridge converter just reaches the shift ratio of the maximum active power of the voltage source converter under fault conditions, P2 and Q2 are the active power and reactive power at the intersection of the charging station power boundary constrained by the maximum allowable AC current and the charging station power boundary constrained by the DC voltage.

10. A fault-through control device for electric vehicles that combines reactive power support and charging power, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the electric vehicle charging station fault ride-through control method as described in any one of claims 1 to 8.

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