Hot-pull control method for emergency power supply in the substation area of ​​multi-vehicle pile unit network

Abstract

The present invention relates to the technical field of electric vehicle charging and discharging system, and in particular to a hot-plug control method for emergency power supply of a substation under a multi-vehicle pile unit network. The method comprises the following steps: constructing a topology and control architecture for reusing a bidirectional charging pile as an emergency power supply for a substation; when the power grid is out of power, the vehicle pile unit adopts a multi-vehicle multi-pile network control strategy to complete the network; in a steady state of emergency power supply for substation loads, when the vehicle pile unit is about to run out of power, control its grid-side and pile-side power converters to shut down, then disconnect the main relay between the bidirectional charging pile and the vehicle, and finally pull out the charging gun, while using a frequency feedforward damping control strategy to suppress transient oscillations under hot-plugging of a multi-vehicle multi-pile network. The present invention can realize seamless hot-plugging of a vehicle pile unit from a multi-vehicle multi-pile network, and can suppress power and frequency oscillations caused by the redistribution of emergency power supply loads in the remaining vehicle pile units during seamless hot-plugging, laying a foundation for the implementation of a new scenario engineering for emergency power supply of a substation for bidirectional charging piles.

Description

Technical Field

[0001] The invention relates to the technical field of electric vehicle charging and discharging systems, and in particular to a hot-plug control method for emergency power supply to a lower platform area of ​​a multi-vehicle pile unit network. Background Art

[0002] With the popularity of electric vehicles, the technical concept of vehicle-to-grid bidirectional power interaction (V2G) has emerged. Its core content is to use the battery units of new energy electric vehicles as large-scale distributed energy storage units of the power grid, and participate in the operation of the power system to achieve bidirectional interaction of energy between the power grid and the vehicle, with the aim of improving the power load curve of the power system and reducing the actual operating pressure of the power grid. Specifically, V2G can balance the load of the power system, charge electric vehicles during the valley power period at night based on time-of-use electricity prices, and feed back energy to the power grid according to demand during the peak power period during the day, thus achieving peak shifting and valley filling.

[0003] On the one hand, although the V2G bidirectional charging and discharging between electric vehicles and the power grid has completed successful demonstration operation in a series of national projects, it has encountered serious economic bottlenecks in its promotion and application. Specifically, it is intolerable for users of high-power fast charging piles to hang the car on the charging pile for a long time to charge and discharge during peak-filling periods. They all need to have a charging waiting time close to the experience of fast refueling of traditional cars. Moreover, compared with the expensive battery cost, the depreciation cost of the battery's charge and discharge cycle life caused by V2G cannot be recovered through the peak-valley price difference. These two major economic bottlenecks have severely restricted the real promotion of V2G. Therefore, vehicle-grid interaction requires other practical forms and corresponding technologies besides V2G.

[0004] On the other hand, in the existing emergency power supply scheme for urban substations, diesel generators or mobile power emergency vehicles are most commonly used. After a power outage occurs, the corresponding power staff usually disconnects the connection switch between the power supply substation and the city power in the distribution cabinet, and then starts the diesel generator or notifies the mobile power emergency vehicle as a backup power supply to continue to supply power to the load of the power supply substation. The time required for diesel generators or mobile power emergency vehicles to restore power is generally relatively long, and the area occupied by the diesel generator is relatively large. In addition to the generator set, it is also necessary to consider the control, power distribution, fuel tank and other auxiliary equipment rooms, which have high requirements for plane and space. In addition, the oil storage room itself is a fire hazard, so it also needs to be fireproofed. Therefore, compared with V2G, reusing bidirectional charging piles as emergency power supplies to replace diesel generators has greater development prospects. However, on the basis of reusing bidirectional charging piles as emergency power supplies, on the one hand, in order to ensure the continuous and uninterrupted emergency power supply of the substation for a long time, it is necessary to dispatch electric vehicles with sufficient power to replace electric vehicles that are about to run out of power, that is, to achieve seamless "hot pull" of electric vehicles and their connected bidirectional charging piles from the network system. On the other hand, under the condition of a multi-machine network with multiple piles and multiple machines, to realize the withdrawal of the bidirectional charging pile vehicle pile unit from the network system, it is necessary to consider the dynamic redistribution of the emergency power supply load power in the remaining multi-vehicle multi-pile network system and the violent power and frequency oscillations in this transient process. Therefore, a new control method for the "hot pull" process is needed. Summary of the invention

[0005] In view of the defects in the prior art, the present invention provides a hot pull control method for emergency power supply in the lower area of ​​a multi-vehicle pile unit network.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a hot-plug control method for emergency power supply of a substation under a multi-vehicle-pile unit network, the method comprising the following steps: constructing a topology and control architecture for reusing the bidirectional charging pile vehicle-pile unit as an emergency power supply for the substation; when the power grid is out of power, based on the topology and control architecture, multiple bidirectional charging pile vehicle-pile units adopt a multi-vehicle and multi-pile networking control strategy to complete the networking; under steady-state conditions where emergency power supply has been provided for the substation load, when the power of the bidirectional charging pile vehicle-pile unit is about to be exhausted, the power converters on the grid side and the pile side of the bidirectional charging pile vehicle-pile unit are controlled to shut down, and then the main relay between the bidirectional charging pile and the electric vehicle is disconnected, and finally the charging gun is pulled out to achieve seamless hot-plugging of the bidirectional charging pile vehicle-pile unit from the topology and control architecture; while achieving the seamless hot-plugging, a frequency feedforward damping control strategy is used to suppress transient oscillations of the topology and control architecture under hot-plug conditions. The present invention can realize seamless hot removal of vehicle-pile units from a multi-vehicle and multi-pile network, and can suppress power and frequency oscillations caused by the redistribution of emergency power supply loads among the remaining vehicle-pile units during seamless hot removal, laying the foundation for the implementation of a new scenario of emergency power supply for bidirectional charging piles.

[0007] Optionally, the construction of a topology and control architecture for reusing the bidirectional charging pile vehicle pile unit as an emergency power supply for the station area includes the following steps:

[0008] Construct a cascade power conversion system for bidirectional charging piles;

[0009] Constructing a power supply circuit for connecting the cascade power conversion system, the power grid and the load in the substation area;

[0010] The power supply circuit is used to interconnect the cascade power conversion system, the power grid and the substation load to form the topology and control architecture.

[0011] Optionally, the cascade power conversion system includes a grid-side inverter and a pile-side converter of each of the bidirectional charging pile vehicle-pile units.

[0012] Optionally, the power supply circuit includes a three-wire AC bus, an isolation transformer, a load switch, a transfer switch, a four-wire AC bus, a grid-side switch and a load bus.

[0013] Optionally, the grid-side inverter and the pile-side converter are cascaded via a common DC bus;

[0014] The three-phase AC sides of the plurality of grid-side inverters are connected in parallel and connected to one side of the triangle of the isolation transformer;

[0015] The grid-side switch and the load switch are both three-phase four-wire, the two ends of the grid-side switch are respectively connected to the grid and the load bus, and the two ends of the load switch are respectively connected to the load bus and the three-phase four-wire of the star side of the isolation transformer;

[0016] The switching switch is a three-phase three-wire switch, and two ends of the switching switch are respectively connected to one side of the triangle of the isolation transformer and the load bus.

[0017] Optionally, when the power grid is out of power, based on the topology and control architecture, multiple bidirectional charging pile vehicle-pile units adopt a multi-vehicle multi-pile networking control strategy to complete networking, including the following steps:

[0018] When the power grid is out of power, sampling the current input to the isolation transformer and the output filter capacitor voltage of the grid-side inverter;

[0019] Based on the sampling results, the instantaneous active power and instantaneous reactive power are calculated using the instantaneous power calculation module;

[0020] The instantaneous active power and the instantaneous reactive power are input into a network control module, and the network control module outputs a voltage amplitude and an angle signal to a voltage generation module;

[0021] Use the voltage generation module to generate a dq axis voltage control instruction, and input the difference between the dq axis voltage control instruction and the dq coordinate system transformation result of the output filter capacitor voltage into the voltage and current inner loop;

[0022] The voltage and current inner loop generates an output voltage dq coordinate axis instruction of the grid-side inverter, and then converts it into an output voltage instruction of a three-phase coordinate system through coordinate system transformation;

[0023] The output voltage instruction is input into a PWM modulation module to generate a high-frequency switching signal for the grid-side inverter.

[0024] Optionally, the frequency feedforward damping control strategy is to introduce frequency feedforward damping into the multi-vehicle multi-pile network control strategy.

[0025] Optionally, after the frequency feedforward damping is introduced into the multi-vehicle multi-pile network construction control strategy, the angle signal output by the network construction control module and the instantaneous active power satisfy the following relationship:

[0026]

[0027] in, is the phase angle of the voltage vector of the i-th bidirectional charging pile, s is the Laplace operator, is the instantaneous active power corresponding to the i-th bidirectional charging pile vehicle pile unit, is the frequency time constant of the i-th bidirectional charging pile vehicle pile unit, is the rated angular frequency, is the damping coefficient of the i-th bidirectional charging pile vehicle pile unit, is the frequency feedforward damping corresponding to the i-th bidirectional charging pile vehicle pile unit, , N is the total number of bidirectional charging pile vehicle pile units.

[0028] Optionally, the frequency feedforward damping satisfies the following relationship:

[0029]

[0030] in, is the frequency feedforward damping, s is the Laplace operator, is the proportional feedforward coefficient, is the integral feed-forward coefficient.

[0031] Optionally, after the frequency feedforward damping is introduced, the open-loop transfer function of the multi-vehicle multi-pile network control strategy satisfies the following relationship:

[0032]

[0033] in, represents the open-loop transfer function of the multi-vehicle multi-pile network control strategy after the frequency feedforward damping is introduced, s is the Laplace operator, is the frequency feedforward damping, is the feedforward coefficient for the example, is the synchronous power factor, is the frequency time constant of the bidirectional charging pile vehicle pile unit, is the rated angular frequency, and D is the damping coefficient of the bidirectional charging pile unit.

[0034] In summary, the present invention constructs a topology and control architecture that reuses bidirectional charging piles as emergency power supplies for substations, transforms bidirectional charging piles into multifunctional multiplexing equipment that provides emergency power supply, and mobilizes electric vehicles to connect to bidirectional charging piles for emergency power supply in substations when power outages occur in substations, thereby improving the disaster prevention and supply guarantee capabilities of urban power supply substations. At the same time, based on the topology and control architecture proposed in the present invention, a hot-plug method for the bidirectional charging pile vehicle unit to exit the networking system during actual operation is proposed, and further a method for suppressing the violent power and frequency oscillations caused by the dynamic redistribution of the emergency power supply load power in the remaining multi-machine system when the bidirectional charging pile vehicle unit exits the networking system, thereby laying the foundation for the implementation of a new scenario engineering for emergency power supply for bidirectional charging piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a flow chart of a hot-pull control method for emergency power supply to a lower area of ​​a multi-vehicle pile unit network according to an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of the topology and control architecture of an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of a control strategy for constructing a network using multiple vehicles and multiple piles according to an embodiment of the present invention;

[0039] Figure 4 It is a hot-pulling process analysis model of the multi-vehicle multi-pile network construction control strategy of an embodiment of the present invention;

[0040] Figure 5 The open-loop transfer function phase margin diagram of the multi-vehicle multi-pile network control strategy of the embodiment of the present invention is shown in FIG1. ​​Among them: 1-power grid, 2-bidirectional charging pile vehicle pile unit, 3-pile side converter, 4-grid side inverter, 5-three-wire AC bus, 6-isolation transformer, 7-load switch, 8-load bus, 9-switching switch, 10-station area load, 11-four-wire AC bus, 12-grid side switch, 13-multi-vehicle multi-pile structure, 14-multi-mechanism network control structure, 15-AC bus, 201-first bidirectional charging pile vehicle pile unit, 202-second bidirectional charging pile vehicle pile unit, 203-third bidirectional charging pile vehicle pile unit. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0042] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0043] It should be noted in advance that, in an optional embodiment, except for independent explanations, the same symbols or letters appearing in all formulas have the same meanings and values.

[0044] In an alternative embodiment, see Figure 1 The present invention provides a hot pull control method for emergency power supply in the lower area of ​​a multi-vehicle pile unit network, the method comprising the following steps:

[0045] S1. Construct a topology and control architecture that reuses the bidirectional charging pile vehicle-pile unit as an emergency power supply for the station area.

[0046] Among them, S1 specifically includes the following steps:

[0047] S11, constructing a cascade power conversion system for a bidirectional charging pile, and at the same time constructing a power supply circuit for connecting the cascade power conversion system, the power grid and the load in the substation.

[0048] Specifically, in this embodiment, see Figure 2 The bidirectional charging pile vehicle pile unit 2 includes a grid-side inverter 4 and a pile-side converter 3. The cascade power conversion system includes multiple bidirectional charging pile vehicle pile units 2, and the three-phase AC sides of multiple grid-side inverters 4 are connected in parallel. The power supply circuit includes a three-wire AC bus 5, an isolation transformer 6, a load switch 7, the switching switch 9, a four-wire AC bus 11, a grid-side switch 12 and a load bus 8.

[0049] Furthermore, the pile-side converter 3 is a DC / DC converter, and the grid-side inverter 4 is an AC / DC converter, both of which are components of the bidirectional charging pile. The cascade power conversion system of this embodiment is a prior art and will not be described in detail here.

[0050] In other optional embodiments, the bidirectional charging pile vehicle pile unit 2 may also include an electric car connected to the bidirectional charging pile.

[0051] S12. Use the power supply circuit to interconnect the cascade power conversion system, the power grid and the substation load to form the topology and control architecture.

[0052] Specifically, in this embodiment, see Figure 2 , the grid-side inverter 4 and the pile-side converter 3 are cascaded through a common DC bus, the pile-side converter 3 is connected to the bidirectional charging pile vehicle pile unit 2 by a cable, and the three-phase AC sides of multiple grid-side inverters 4 are connected in parallel and connected to the delta side of the isolation transformer 6. The grid-side switch 12 and the load switch 7 are both three-phase four-wire, and the two ends of the grid-side switch 12 are respectively connected to the power grid 1 and the load bus 8, and the two ends of the load switch 7 are respectively connected to the load bus 8 and the three-phase four-wire on the star side of the isolation transformer 6. The switching switch 9 is three-phase three-wire, and the two ends of the switching switch 9 are respectively connected to the delta side of the isolation transformer 6 and the load bus 8. Multiple load feeders are used to connect the load bus 8 and the substation load 10.

[0053] The topology and control architecture of reusing bidirectional charging piles as emergency power supply for substations can also be called the substation emergency power supply system of bidirectional charging piles. By constructing the topology and control architecture of reusing bidirectional charging piles as emergency power supply for substations, the bidirectional charging piles are transformed into multifunctional multiplexing equipment for providing emergency power supply, breaking the application bottleneck of bidirectional charging pile vehicle-grid interaction V2G limited to shifting peaks and filling valleys, and can mobilize any electric vehicle and bidirectional charging pile to connect for substation emergency power supply when the power grid 1 is out of power, so that the emergency diesel generator set does not need to be installed to greatly improve the disaster prevention capacity of the urban power supply substation, and at the same time, it can also relieve the pressure of emergency power supply vehicles.

[0054] S2. When the power grid is out of power, based on the topology and control architecture, multiple of the bidirectional charging pile vehicle-pile units adopt a multi-vehicle multi-pile networking control strategy to complete networking.

[0055] Among them, see Figure 2 and Figure 3 , step S2 specifically includes the following steps:

[0056] S21. When the power grid is out of power, sampling the current input to the isolation transformer and the output filter capacitor voltage of the grid-side inverter.

[0057] More specifically, when the power grid 1 is out of power, the emergency power supply mode is switched to close the load switch 7, disconnect the grid-side switch 12 and the switching switch 9, and then the electric vehicle battery pack is used to provide off-grid emergency power supply to the load in the substation. and the output filter capacitor voltage of the grid-side inverter 4 Sampling is performed and the sampling results are input into the multi-mechanism network control structure 14.

[0058] S22. Based on the sampling result, the instantaneous active power and the instantaneous reactive power are calculated using the instantaneous power calculation module.

[0059] Specifically, in this embodiment, the sampling result of step S21 is converted into The d-axis component in the dq coordinate system and the q-axis component as well as The d-axis component in the dq coordinate system and the q-axis component , then , , and The input instantaneous power calculation module performs instantaneous power calculation to obtain instantaneous active power P and instantaneous reactive power Q.

[0060] Furthermore, the instantaneous power calculation module for calculating the instantaneous power is a prior art and will not be described in detail here.

[0061] S23, inputting the instantaneous active power and the instantaneous reactive power into a network control module, and the network control module outputs voltage amplitude and angle signals to a voltage generation module.

[0062] Specifically, in this embodiment, the angle signal output by the network control module is The relationship between the instantaneous active power P is as follows:

[0063]

[0064] in, is the phase angle of the voltage vector of the i-th bidirectional charging pile vehicle pile unit 2, s is the Laplace operator, is the instantaneous active power corresponding to the i-th bidirectional charging pile vehicle pile unit 2, is the frequency time constant of the i-th bidirectional charging pile vehicle pile unit 2, is the rated angular frequency of the bidirectional charging pile vehicle pile unit 2, is the damping coefficient of the i-th bidirectional charging pile vehicle pile unit 2, , N is the total number of the bidirectional charging pile vehicle pile units 2. A bidirectional charging pile vehicle pile unit 2 includes a bidirectional charging pile and an electric vehicle connected to the bidirectional charging pile.

[0065] The voltage amplitude U output by the network control module and the instantaneous reactive power Q satisfy the following relationship:

[0066]

[0067] in, is the voltage amplitude output by the network control module corresponding to the i-th bidirectional charging pile vehicle pile unit 2, is the voltage regulation coefficient of the i-th bidirectional charging pile vehicle pile unit 2, is the reactive power adjustment coefficient of the i-th bidirectional charging pile vehicle pile unit 2, is the instantaneous reactive power corresponding to the i-th bidirectional charging pile vehicle pile unit 2.

[0068] At this time, the output active power change of the bidirectional charging pile vehicle pile unit 2 and the rated active power change should satisfy the following relationship:

[0069]

[0070] in, is the output active power change of the i-th bidirectional charging pile vehicle pile unit 2, is the change in rated active power of the i-th bidirectional charging pile vehicle pile unit 2, is the load power variation in the entire multi-vehicle multi-pile structure 13, and Respectively represent the active power command of the i-th bidirectional charging pile vehicle pile unit 2 The transfer function of the frequency disturbance to its output power is expressed as follows:

[0071]

[0072]

[0073] in, is the output phase voltage of the multi-vehicle multi-pile structure 13, is the voltage amplitude at the PCC in the multi-vehicle multi-pile structure 13, is the grid-side equivalent impedance of the i-th bidirectional charging pile vehicle pile unit 2.

[0074] S24, using the voltage generation module to generate a dq axis voltage control instruction, and subtracting the dq axis voltage control instruction from the dq coordinate system transformation result of the output filter capacitor voltage and inputting the result into the voltage and current inner loop.

[0075] Specifically, in this embodiment, the dq axis voltage control instructions generated by the voltage generation module include the d axis voltage control instructions and q-axis voltage control command The dq coordinate system transformation results of the output filter capacitor voltage include and .

[0076] Further, and Do badly, and Make a difference and input the result into the voltage and current inner loop.

[0077] S25, the voltage-current inner loop generates an output voltage dq coordinate axis instruction of the grid-side inverter, and then converts it into an output voltage instruction of a three-phase coordinate system through coordinate system transformation.

[0078] Specifically, in this embodiment, the output voltage dq coordinate axis instruction generated by the voltage and current inner loop is converted into an output voltage instruction of a three-phase coordinate system after dq / abc transformation.

[0079] Further, in Figure 3 middle, and are the filter inductor and filter capacitor of the output filter of the grid-side inverter 4, That is The voltage across the terminals, and are line inductance and resistance respectively, represents the output current of the grid-side converter 4, is the reactive power command, It is the DC capacitor between the two-stage cascade of the grid-side inverter 4 and the pile-side converter 3.

[0080] S26, inputting the output voltage instruction into a PWM modulation module to generate a high-frequency switching signal for the grid-side inverter.

[0081] Specifically, in this embodiment, the output voltage command obtained in S25 is input into the PWM modulation module to generate a high-frequency switching signal of the grid-side inverter 4 .

[0082] Furthermore, when the power grid 1 is out of power, the bidirectional charging pile vehicle-pile unit 2 adopts a multi-vehicle and multi-pile network control strategy to build a microgrid and mobilize any electric vehicles to connect to the bidirectional charging piles for emergency power supply to the substation, thereby eliminating the need to install emergency diesel generator sets to greatly improve the disaster prevention capabilities of the urban power supply substation, while also alleviating the pressure on emergency power supply vehicles.

[0083] In other optional embodiments, when the power grid 1 operates normally, see Figure 2 , the load switch 7 is opened, the grid-side switch 12 and the switching switch 9 are closed, the three-phase AC side of the grid-side inverter 4 is directly connected to the three-phase line of the load bus 8, and the power grid 1 directly supplies power to the substation load 10.

[0084] S3. Under the steady-state condition that emergency power supply has been provided for the substation load, when the power of the bidirectional charging pile vehicle pile unit is about to be exhausted, the power converters on the grid side and the pile side of the bidirectional charging pile vehicle pile unit are controlled to shut down, and then the main relay between the bidirectional charging pile and the electric vehicle is disconnected, and finally the charging gun is pulled out to realize seamless hot pull of the bidirectional charging pile vehicle pile unit from the topology and control architecture.

[0085] Specifically, in this embodiment, under the steady-state condition that the power grid 1 is out of power and the bidirectional charging pile vehicle pile unit 2 has provided emergency power supply for the substation load 10, when the power of the electric vehicle connected to a bidirectional charging pile is about to run out, the operator or the main control system controls the power converters on the grid side and the pile side of the bidirectional charging pile vehicle pile unit 2 to shut down, and then disconnects the main relay between the bidirectional charging pile and the electric vehicle, and finally manually pulls out the charging gun. In this hot pull mode, the bidirectional charging pile and the electric vehicle connected to it are both instantly out of the network, and the substation load power will be dynamically redistributed among the remaining bidirectional charging pile vehicle pile units 2, and the entire network system will reach a new power balance and frequency balance after the transient state.

[0086] S4. While achieving the seamless hot pull, a frequency feedforward damping control strategy is used to suppress transient oscillations of the topology and control architecture under hot pull conditions.

[0087] Specifically, in this embodiment, see Figure 4 The first bidirectional charging pile vehicle pile unit 201, the second bidirectional charging pile vehicle pile unit 202 and the third bidirectional charging pile vehicle pile unit 203 output the filter capacitor voltage To control the target, they are connected to the AC bus 15 through their respective LCL filters, and then transmit power to the load through the isolation transformer 6 and the load switch 7. Under off-grid load conditions, if the third bidirectional charging pile vehicle pile unit 203 suddenly exits, the expression for analyzing the output power of the second bidirectional charging pile vehicle pile unit 202 is as follows:

[0088]

[0089] in, is the synchronous power coefficient of the i-th bidirectional charging pile vehicle pile unit 2 and ; is the output voltage amplitude of the i-th bidirectional charging pile vehicle pile unit 2; is the rated voltage amplitude of the i-th bidirectional charging pile vehicle pile unit 2; is the filter inductance of the LCL filter corresponding to the i-th bidirectional charging pile vehicle pile unit 2; is the filter capacitor of the LCL filter corresponding to the i-th bidirectional charging pile vehicle pile unit 2; is the output power of the second bidirectional charging pile vehicle pile unit 202; , , and are 4 different reference symbols, which are used to simplify the expression of the output power of the second bidirectional charging pile vehicle pile unit 202. Figure 4 There are three bidirectional charging pile units in the CPC, so at this time . , , and The following relations are satisfied in sequence:

[0090]

[0091]

[0092]

[0093]

[0094] According to the final value theorem, the steady-state value of the output power of the second bidirectional charging pile vehicle pile unit 202 is As shown below:

[0095]

[0096] The steady-state value Extracted from the output power expression, the expression of the output power of the second bidirectional charging pile vehicle pile unit 202 is rewritten as:

[0097]

[0098] From the rewritten expression, we can see that the power oscillation of the hot pull process comes from the third-order oscillation term inherent in the expression. In addition, Figure 4 In the embodiment, the LCL filter corresponding to the first bidirectional charging pile vehicle pile unit 201 includes a filter inductor 、Filter capacitor and line inductance The LCL filter corresponding to the second bidirectional charging pile vehicle pile unit 202 includes a filter inductor 、Filter capacitor and line inductance The LCL filter corresponding to the third bidirectional charging pile vehicle pile unit 203 includes a filter inductor 、Filter capacitor and line inductance .

[0099] Furthermore, this embodiment uses a frequency feedforward damping control strategy to suppress power oscillation and frequency oscillation during the hot pull process. The frequency feedforward damping control strategy specifically introduces frequency feedforward damping into the multi-vehicle multi-pile network control strategy. After the frequency feedforward damping is introduced into the multi-vehicle multi-pile network control strategy, the angle signal output by the network control module and the instantaneous active power satisfy the following relationship:

[0100]

[0101] in, is the frequency feedforward damping corresponding to the i-th bidirectional charging pile vehicle pile unit. The frequency feedforward damping satisfies the following relationship:

[0102]

[0103] in, is the frequency feedforward damping, is the proportional feedforward coefficient, is the integral feed-forward coefficient.

[0104] After introducing frequency feedforward damping, the open-loop transfer function of the multi-vehicle multi-pile network control strategy satisfies the following relationship:

[0105]

[0106] in, represents the open-loop transfer function of the multi-vehicle multi-pile network control strategy after introducing frequency feedforward damping, is the synchronous power coefficient of the bidirectional charging pile vehicle pile unit 2, is the frequency time constant of the bidirectional charging pile vehicle pile unit 2, and D is the damping coefficient of the bidirectional charging pile vehicle pile unit 2.

[0107] Furthermore, the open-loop bode diagram of the multi-vehicle multi-pile network control strategy before and after adding frequency feedforward damping is shown in Figure 5 As shown in the figure. Before adding frequency feedforward damping, the phase margin of network control is only 12.7°, while after introducing frequency feedforward damping, the phase margin of network control increases to 49.6°. This shows that the frequency feedforward damping control strategy improves the phase margin of network control and can significantly improve the power stability and frequency stability in hot-plug scenarios.

[0108] It should be noted that, in some cases, the actions described in the specification can be performed in a different order and still achieve the desired results. In this embodiment, the order of steps given is only to make the embodiment appear clearer and easier to explain, rather than to limit it.

[0109] In summary, the present invention constructs a topology and control architecture that reuses bidirectional charging piles as emergency power supplies for substations, transforms bidirectional charging piles into multifunctional multiplexing equipment that provides emergency power supply, and mobilizes electric vehicles to connect to bidirectional charging piles for emergency power supply in substations when power outages occur in substations, thereby improving the disaster prevention and supply guarantee capabilities of urban power supply substations. At the same time, based on the topology and control architecture proposed in the present invention, a hot-plug method for the bidirectional charging pile vehicle unit to exit the networking system during actual operation is proposed, and further a method for suppressing the violent power and frequency oscillations caused by the dynamic redistribution of the emergency power supply load power in the remaining multi-machine system when the bidirectional charging pile vehicle unit exits the networking system, thereby laying the foundation for the implementation of a new scenario engineering for emergency power supply for bidirectional charging piles.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A hot pull control method for emergency power supply in the lower area of ​​a multi-vehicle pile unit network, characterized in that: The steps include: Construct a topology and control architecture that reuses the bidirectional charging pile vehicle pile unit as an emergency power supply for the station area; When the power grid is out of power, based on the topology and control architecture, multiple bidirectional charging pile vehicle pile units adopt a multi-vehicle multi-pile network construction control strategy to complete the network construction; Under the steady-state condition that emergency power supply has been provided for the load in the substation, when the power of the bidirectional charging pile vehicle pile unit is about to be exhausted, the power converters on the grid side and the pile side of the bidirectional charging pile vehicle pile unit are controlled to shut down, and then the main relay between the bidirectional charging pile and the electric vehicle is disconnected, and finally the charging gun is pulled out to realize seamless hot pull of the bidirectional charging pile vehicle pile unit from the topology and control architecture; While achieving the seamless hot pull, a frequency feedforward damping control strategy is used to suppress transient oscillations of the topology and control architecture under hot pull conditions; The topology and control architecture for reusing the bidirectional charging pile vehicle pile unit as an emergency power supply for the station area includes the following steps: Construct a cascade power conversion system for bidirectional charging piles; Constructing a power supply circuit for connecting the cascade power conversion system, the power grid and the load in the substation area; Using the power supply circuit to interconnect the cascade power conversion system, the power grid and the load in the substation area to form the topology and control architecture; The cascade power conversion system includes a grid-side inverter and a pile-side converter of each of the bidirectional charging pile vehicle pile units; The power supply circuit includes a three-wire AC bus, an isolation transformer, a load switch, a transfer switch, a four-wire AC bus, a grid-side switch and a load bus; The grid-side inverter and the pile-side converter are cascaded via a common DC bus; The three-phase AC sides of the plurality of grid-side inverters are connected in parallel and connected to one side of the triangle of the isolation transformer; The grid-side switch and the load switch are both three-phase four-wire, the two ends of the grid-side switch are respectively connected to the grid and the load bus, and the two ends of the load switch are respectively connected to the load bus and the three-phase four-wire of the star side of the isolation transformer; The switching switch is a three-phase three-wire switch, and the two ends of the switching switch are respectively connected to one side of the triangle of the isolation transformer and the load bus; When the power grid is out of power, based on the topology and control architecture, multiple bidirectional charging pile vehicle pile units adopt a multi-vehicle multi-pile network construction control strategy to complete the network construction, including the following steps: When the power grid is out of power, sampling the current input to the isolation transformer and the output filter capacitor voltage of the grid-side inverter; Based on the sampling results, the instantaneous active power and instantaneous reactive power are calculated using the instantaneous power calculation module; The instantaneous active power and the instantaneous reactive power are input into a network control module, and the network control module outputs a voltage amplitude and an angle signal to a voltage generation module; Use the voltage generation module to generate a dq axis voltage control instruction, and input the difference between the dq axis voltage control instruction and the dq coordinate system transformation result of the output filter capacitor voltage into the voltage and current inner loop; The voltage and current inner loop generates an output voltage dq coordinate axis instruction of the grid-side inverter, and then converts it into an output voltage instruction of a three-phase coordinate system through coordinate system transformation; Inputting the output voltage command into a PWM modulation module to generate a high-frequency switching signal for the grid-side inverter; The frequency feedforward damping control strategy is to introduce frequency feedforward damping into the multi-vehicle multi-pile network control strategy; After the frequency feedforward damping is introduced into the multi-vehicle multi-pile network control strategy, the angle signal output by the network control module and the instantaneous active power satisfy the following relationship: in, is the phase angle of the voltage vector of the i-th bidirectional charging pile, s is the Laplace operator, is the instantaneous active power corresponding to the i-th bidirectional charging pile vehicle pile unit, is the frequency time constant of the i-th bidirectional charging pile vehicle pile unit, is the rated angular frequency, is the damping coefficient of the i-th bidirectional charging pile vehicle pile unit, is the frequency feedforward damping corresponding to the i-th bidirectional charging pile vehicle pile unit, , N is the total number of bidirectional charging pile vehicle pile units; The frequency feedforward damping satisfies the following relationship: in, is the frequency feedforward damping, s is the Laplace operator, is the proportional feedforward coefficient, is the integral feedforward coefficient; After the frequency feedforward damping is introduced, the open-loop transfer function of the multi-vehicle multi-pile network control strategy satisfies the following relationship: in, represents the open-loop transfer function of the multi-vehicle multi-pile network control strategy after the frequency feedforward damping is introduced, s is the Laplace operator, is the proportional feedforward coefficient, is the integral feed-forward coefficient, is the synchronous power factor, is the frequency time constant of the bidirectional charging pile vehicle pile unit, is the rated angular frequency, and D is the damping coefficient of the bidirectional charging pile unit.

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