Hot-plug mode control method for emergency power supply in substation under multi-vehicle and multi-pile network control

Abstract

The present invention relates to the technical field of electric vehicle charging piles, and in particular to a hot-plug mode control method for emergency power supply in a substation under the control of a multi-vehicle multi-pile network, the method comprising the following steps: constructing a topology and control architecture for reusing a bidirectional charging pile as an emergency power supply for a substation; when a new electric vehicle needs to be connected when the network is completed, inserting a charging gun and connecting a main relay; the hot-plugged vehicle pile unit obtains the frequency and phase information under the current network through a phase-locked loop, and then starts the voltage output of the vehicle pile unit to synchronize with the voltage frequency and phase of the current network, closes the AC network side relay of the vehicle pile unit to achieve seamless hot plugging, and uses a high-pass frequency compensation control strategy to suppress transient oscillations under hot plugging in a multi-vehicle multi-pile network. The present invention can realize seamless hot plugging of vehicle pile units into a multi-vehicle multi-pile network, and can suppress power oscillations and frequency oscillations caused by dynamic redistribution of emergency power supply load power in existing vehicle pile units during seamless hot plugging.

Description

Technical Field

[0001] The invention relates to the technical field of electric vehicle charging piles, and in particular to a hot-plug mode control method for emergency power supply to a platform under a multi-vehicle and multi-pile network control. 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 mains in the distribution cabinet, and then starts the diesel generator or notifies the mobile power emergency vehicle to continue to supply power to the load of the power supply substation as a backup power supply. The time required for diesel generators or mobile power emergency vehicles to restore power is generally relatively long, and the area occupied by diesel generators 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.

[0005] However, on the basis of reusing the bidirectional charging pile as an emergency power source, on the one hand, the newly arrived electric vehicle needs to be connected to the bidirectional charging pile and participate in the networking, that is, the seamless "hot plug" of the car-pile unit. On the other hand, under the condition of a multi-machine network corresponding to multiple piles and multiple machines, in order to realize the seamless entry of the car-pile unit into the current multi-car multi-pile networking system, and to enter the network with the emergency power supply load, it is necessary to consider the dynamic redistribution of the emergency power supply load power in the existing multi-car-pile unit networking system, and the violent power and frequency oscillations in this transient process, and the mechanism of this oscillation is completely different from the oscillation mechanism caused when the car-pile unit exits the networking. Therefore, a new control method for the "hot plug" process is needed. Summary of the invention

[0006] In view of the defects in the prior art, the present invention provides a hot-plug mode control method for emergency power supply to a substation under multi-vehicle and multi-pile network control.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a hot-plug mode control method for emergency power supply in the substation under the control of multi-vehicle multi-pile network construction, the method comprising the following steps: constructing a topology and control architecture for reusing the bidirectional charging pile car pile unit as the substation emergency power supply; when the electric vehicle is connected in the case of a power outage in the power grid and the bidirectional charging pile car pile unit has completed the network construction, the charging gun is inserted into the electric vehicle and the main relay between the bidirectional charging pile and the electric vehicle is connected, thereby forming a hot-plug car pile unit; the hot-plug car pile unit obtains the frequency information and phase information under the current network construction through a phase-locked loop, and then starts the voltage output of the hot-plug car pile unit to synchronize with the voltage frequency and phase of the current network construction, and closes the AC network side relay of the hot-plug car pile unit to achieve seamless hot plug; while realizing the seamless hot plug, a high-pass frequency compensation control strategy is used to suppress the transient oscillation of the topology and control architecture under hot plug conditions. The present invention can realize the seamless hot plug of the car pile unit into the multi-vehicle multi-pile network construction, and can suppress the power oscillation and frequency oscillation caused by the dynamic redistribution of the emergency power supply load power in the existing car pile unit during seamless hot plug.

[0008] 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:

[0009] Construct a cascade power conversion system for bidirectional charging piles;

[0010] Constructing a power supply circuit for connecting the cascade power conversion system, the power grid and the load in the substation area;

[0011] 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.

[0012] Optionally, the cascade power conversion system includes a grid-side inverter, a pile-side converter and the bidirectional charging pile vehicle-pile unit.

[0013] 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.

[0014] Optionally, the grid-side inverter and the pile-side converter are cascaded via a common DC bus;

[0015] 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;

[0016] 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;

[0017] 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.

[0018] Optionally, when the power grid is out of power, based on the topology and control architecture, the bidirectional charging pile vehicle-pile unit adopts a multi-vehicle multi-pile networking control strategy to complete networking.

[0019] Optionally, when the power grid is out of power, based on the topology and control architecture, the bidirectional charging pile vehicle pile unit adopts a multi-vehicle multi-pile network construction control strategy to complete the network construction, including the following steps:

[0020] 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;

[0021] Based on the sampling results, the instantaneous active power and instantaneous reactive power are calculated using the instantaneous power calculation module;

[0022] 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;

[0023] 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;

[0024] 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;

[0025] The output voltage instruction is input into a PWM modulation module to generate a high-frequency switching signal for the grid-side inverter.

[0026] Optionally, the high-pass frequency compensation control strategy is to add high-pass frequency compensation to the multi-vehicle multi-pile network control strategy.

[0027] Optionally, after the high-pass frequency compensation is added to the multi-vehicle multi-pile networking control strategy, the angle signal output by the networking control module and the instantaneous active power satisfy the following relationship:

[0028]

[0029] Among them, θ i is the phase angle of the voltage vector of the i-th bidirectional charging pile, s is the Laplace operator, P outi is the instantaneous active power corresponding to the i-th bidirectional charging pile vehicle pile unit, J 0i is the frequency time constant of the i-th bidirectional charging pile vehicle pile unit, ω0 is the rated angular frequency, D i is the damping coefficient of the i-th bidirectional charging pile vehicle pile unit, G ci is the high-pass frequency compensation corresponding to the i-th bidirectional charging pile vehicle pile unit, i=1, 2, 3, ..., N, and N is the total number of bidirectional charging pile vehicle pile units.

[0030] Optionally, the high-pass frequency compensation satisfies the following relationship:

[0031]

[0032] Among them, G c For the high-pass frequency compensation, is the small signal variation of the AC bus frequency, s is the Laplace operator, ω s is the integral feed-forward coefficient of the AC bus frequency.

[0033] 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 proposed topology and control architecture, the present invention proposes a hot-plug method for adding bidirectional charging pile vehicle pile units to the networking system during actual operation, and further proposes a method for suppressing the violent power and frequency oscillations caused by the dynamic redistribution of emergency power supply load power in a multi-machine system when bidirectional charging pile vehicle pile units are added to 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

[0034] 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.

[0035] Figure 1 It is a flow chart of a hot-plug mode control method for emergency power supply to a substation under a multi-vehicle multi-pile network control according to an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of the topology and control architecture of an embodiment of the present invention;

[0037] 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;

[0038] Figure 4 It is a hot-plugging process analysis model of the multi-vehicle multi-pile network control strategy of the embodiment of the present invention;

[0039] Figure 5 Schematic diagram of the zero-pole changes of the output power expression of the hot-plug charging pile unit according to an embodiment of the present invention.

[0040] 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 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-the first bidirectional charging pile vehicle-pile unit, 202-the second bidirectional charging pile vehicle-pile unit, 203-the 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-plug mode control method for emergency power supply in a substation under multi-vehicle multi-pile network control, 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 that provides emergency power supply, breaking the application bottleneck of bidirectional charging pile vehicle-grid interaction V2G limited to shifting peaks and filling valleys.

[0054] S2. When an electric vehicle is connected when the power grid is out and the bidirectional charging pile vehicle-pile unit has completed networking, a charging gun is inserted into the electric vehicle and a main relay is connected between the bidirectional charging pile and the electric vehicle, thereby forming a hot-plug vehicle-pile unit.

[0055] Specifically, in this embodiment, after the power grid 1 is out of power and multiple bidirectional charging pile vehicle pile units 2 have been networked, multiple bidirectional charging pile vehicle pile units 2 are already providing stable emergency power supply for the load branch of the substation area. In order to increase the reliability and duration of emergency power supply, the existing bidirectional charging piles can be used to connect more electric vehicles. First, the operator inserts the charging gun into the electric vehicle, and then operates on the user interface of the bidirectional charging pile to connect the main relay between the bidirectional charging pile and the electric vehicle to form a hot-plug vehicle pile unit. At this time, the main control system in the charging station will receive real-time information about the battery pack of the electric vehicle in the hot-plug vehicle pile unit.

[0056] For more details, see Figure 2 and Figure 3 When the power grid 1 is out of power, based on the topology and control architecture, multiple bidirectional charging pile vehicle pile units 2 adopt a multi-vehicle multi-pile network construction control strategy to complete the network construction, which specifically includes the following steps:

[0057] T1. When the power grid is out of power, sampling is performed on the current input to the isolation transformer and the output filter capacitor voltage of the grid-side inverter.

[0058] 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. At this time, in the multi-vehicle multi-pile structure 13, the current i2 of the input isolation transformer 6 and the output filter capacitor voltage u of the grid-side inverter 4 are c Sampling is performed and the sampling results are input into the multi-mechanism network control structure 14.

[0059] T2. Based on the sampling results, the instantaneous active power and instantaneous reactive power are calculated using the instantaneous power calculation module.

[0060] Specifically, in this embodiment, the sampling result of step T1 is transformed by abc / dq to obtain the d-axis component i of i2 in the dq coordinate system. 2d and the q-axis component i 2q and u c In the dq coordinate system, the d-axis component u c_d and the q-axis component u c_q , then i 2d 、i 2q 、u c_d and u c_q The input instantaneous power calculation module performs instantaneous power calculation to obtain instantaneous active power P and instantaneous reactive power Q.

[0061] Furthermore, the instantaneous power calculation module for calculating the instantaneous power is a prior art and will not be described in detail here.

[0062] T3. Input 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.

[0063] Specifically, in this embodiment, the angle signal θ output by the network control module and the instantaneous active power P satisfy the following relationship:

[0064]

[0065] Among them, θ i is the phase angle of the voltage vector of the i-th bidirectional charging pile vehicle pile unit 2, s is the Laplace operator, P outi is the instantaneous active power corresponding to the i-th bidirectional charging pile vehicle pile unit 2, J 0i is the frequency time constant of the i-th bidirectional charging pile vehicle pile unit 2, ω0 is the rated angular frequency of the bidirectional charging pile vehicle pile unit 2, D iis the damping coefficient of the i-th bidirectional charging pile vehicle pile unit 2, i=1,2,3,...,N, and N is the total number of 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.

[0066] The voltage amplitude U output by the network control module and the instantaneous reactive power Q satisfy the following relationship:

[0067]

[0068] Among them, U i is the voltage amplitude output by the network control module corresponding to the i-th bidirectional charging pile vehicle pile unit 2, K i is the voltage regulation coefficient of the i-th bidirectional charging pile vehicle pile unit 2, D qi is the reactive power regulation coefficient of the i-th bidirectional charging pile vehicle pile unit 2, Q outi is the instantaneous reactive power corresponding to the i-th bidirectional charging pile vehicle pile unit 2.

[0069] 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:

[0070]

[0071] Among them, ΔP outi is the output active power change of the i-th bidirectional charging pile vehicle pile unit 2, ΔP seti is the rated active power change of the i-th bidirectional charging pile vehicle pile unit 2, ΔP load is the load power variation in the entire multi-vehicle multi-pile structure 13, G iP and G iω They represent the active power command P of the i-th bidirectional charging pile vehicle pile unit 2 respectively. ref The transfer function of the frequency disturbance to its output power is expressed as follows:

[0072]

[0073] Among them, U0 is the output phase voltage of the multi-vehicle multi-pile structure 13, U g is the voltage amplitude at the PCC in the multi-vehicle multi-pile structure 13, X gi is the grid-side equivalent impedance of the i-th bidirectional charging pile vehicle pile unit 2.

[0074] T4. 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.

[0075] Specifically, in this embodiment, the dq axis voltage control instructions generated by the voltage generation module include the d axis voltage control instruction u c_dref and q-axis voltage control command u c_qref The dq coordinate system transformation result of the output filter capacitor voltage includes u c_d and u c_q .

[0076] Furthermore, c_dref and u c_d Do poorly, u c_qref and u c_q Make a difference and input the result into the voltage and current inner loop.

[0077] T5. 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 In, L f and C f are the filter inductance and filter capacitance of the output filter of the grid-side inverter 4, u c That is C f Voltage across L g and R g are line inductance and resistance respectively, i1 represents the output current of the grid-side converter 4, Q ref is the reactive power command, C dc It is the DC capacitor between the two-stage cascade of the grid-side inverter 4 and the pile-side converter 3.

[0080] T6. Input 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 instruction obtained in T5 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, the hot-swap vehicle pile unit obtains the frequency information and phase information of the current network through a phase-locked loop, then starts the voltage output of the hot-swap vehicle pile unit to synchronize with the voltage frequency and phase of the current network, and closes the AC network side relay of the hot-swap vehicle pile unit to achieve seamless hot plugging.

[0085] Specifically, in this embodiment, after the hot-plug car pile unit is added to the current network through seamless hot plugging, a new networking system will be formed. In the seamless hot plugging method given by S2 and S3, the power of the substation load 10 will be dynamically redistributed between the hot-plug car pile unit and the original multiple bidirectional charging pile car pile units 2. The new networking system will reach a new balance of power and frequency after the transient state.

[0086] S4. While achieving the seamless hot plug, a high-pass frequency compensation control strategy is used to suppress transient oscillations of the topology and control architecture under hot plug 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 u c 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 is suddenly connected, that is, the third bidirectional charging pile vehicle pile unit 203 is a hot plug vehicle pile unit, the expression for analyzing the output power P3 of the third bidirectional charging pile vehicle pile unit 203 is as follows:

[0088]

[0089] Among them, α1, β1, γ1 and σ1 are 4 different reference symbols, which are used to simplify the expression of the output power of the third bidirectional charging pile vehicle pile unit 203. α1, β1, γ1 and δ1 satisfy the following relationship in sequence:

[0090]

[0091] δ1=D1+D2+D3

[0092] Among them, K pi is the synchronous power coefficient of the i-th bidirectional charging pile vehicle pile unit 2 and K pi =3E i E0i / [X gi +ω0(L fi +L gi )]; E i is the output voltage amplitude of the i-th bidirectional charging pile vehicle pile unit 2; E 0i is the rated voltage amplitude of the i-th bidirectional charging pile vehicle pile unit 2; L fi is the filter inductance of the LCL filter corresponding to the i-th bidirectional charging pile vehicle pile unit 2; L gi is the filter capacitor of the LCL filter corresponding to the i-th bidirectional charging pile vehicle pile unit 2. Figure 4 There are three bidirectional charging pile units 2, so i=1,2,3 at this time.

[0093] According to the final value theorem, the steady-state value of the output power of the third bidirectional charging pile vehicle pile unit 203 is As shown below:

[0094]

[0095] The steady-state value Extracted from the output power expression, the expression of the output power of the third bidirectional charging pile vehicle pile unit 203 is rewritten as:

[0096]

[0097] From the rewritten expression, we can see that the power oscillation during the hot plug process comes from the inherent oscillation term 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 L f1 、Filter capacitor C f1 and line inductance L g1 The LCL filter corresponding to the second bidirectional charging pile vehicle pile unit 202 includes a filter inductor L f2 、Filter capacitor C f2 and line inductance L g2 The LCL filter corresponding to the third bidirectional charging pile vehicle pile unit 203 includes a filter inductor L f3 、Filter capacitor C f3 and line inductance L g3 .

[0098] Furthermore, this embodiment uses a high-pass frequency compensation control strategy to suppress transient oscillations of the topology and control architecture under hot plugging conditions. The high-pass frequency compensation control strategy specifically adds high-pass frequency compensation to the multi-vehicle multi-pile network control strategy. After adding high-pass frequency compensation to 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:

[0099]

[0100] Among them, G ci is the high-pass frequency compensation corresponding to the i-th bidirectional charging pile vehicle pile unit. The high-pass frequency compensation satisfies the following relationship:

[0101]

[0102] Among them, G c For high-pass frequency compensation, is the small signal change of the AC bus frequency, ω s is the integral feed-forward coefficient of the AC bus frequency.

[0103] After adding high-pass frequency compensation to the multi-vehicle multi-pile network control strategy, the output power of the third bidirectional charging pile vehicle pile unit 203 is expressed as:

[0104]

[0105] Furthermore, after adding high-pass frequency compensation to the multi-vehicle multi-pile network control strategy, the zero-pole changes of the expression of the output power of the third bidirectional charging pile vehicle pile unit 203 are as follows: Figure 5 As shown, with ω s As increases, the isolated pole introduced by the high-pass frequency compensation gradually moves away from the imaginary axis, and the damping effect on the hot plug process decreases, thereby suppressing the violent power and frequency oscillations caused by the dynamic redistribution of the emergency power supply load power in the multi-machine system during the hot plug process.

[0106] 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.

[0107] 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 proposed topology and control architecture, the present invention proposes a hot-plug method for adding bidirectional charging pile vehicle pile units to the networking system during actual operation, and further proposes a method for suppressing the violent power and frequency oscillations caused by the dynamic redistribution of emergency power supply load power in a multi-machine system when bidirectional charging pile vehicle pile units are added to the networking system, thereby laying the foundation for the implementation of a new scenario engineering for emergency power supply for bidirectional charging piles.

[0108] 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-plug mode control method for emergency power supply in a substation under multi-vehicle and multi-pile network control, 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 electric vehicle is connected when the power grid is out and the bidirectional charging pile vehicle-pile unit has completed the network construction, the charging gun is inserted into the electric vehicle and the main relay between the bidirectional charging pile and the electric vehicle is connected, thereby forming a hot-plug vehicle-pile unit; The hot-plug car pile unit obtains the frequency information and phase information of the current network through a phase-locked loop, then starts the voltage output of the hot-plug car pile unit to synchronize with the voltage frequency and phase of the current network, and closes the AC network side relay of the hot-plug car pile unit to achieve seamless hot plugging; While achieving the seamless hot plug, a high-pass frequency compensation control strategy is used to suppress transient oscillations of the topology and control architecture under hot plug 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, a pile-side converter and the bidirectional charging pile vehicle pile unit; 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, the bidirectional charging pile vehicle-pile unit adopts a multi-vehicle multi-pile network construction control strategy to complete the network construction; When the power grid is out of power, based on the topology and control architecture, the bidirectional charging pile vehicle pile unit adopts 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 high-pass frequency compensation control strategy is to add high-pass frequency compensation to the multi-vehicle multi-pile network control strategy; After the high-pass frequency compensation is added to the multi-vehicle multi-pile networking control strategy, the angle signal output by the networking 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 high-pass frequency compensation corresponding to the i-th bidirectional charging pile vehicle pile unit, , N is the total number of bidirectional charging pile vehicle pile units.

2. The hot-plug mode control method for emergency power supply in the platform area under the multi-vehicle multi-pile network control according to claim 1 is characterized in that: The high-pass frequency compensation satisfies the following relationship: in, For the high-pass frequency compensation, is the small signal variation of the AC bus frequency, s is the Laplace operator, is the integral feed-forward coefficient of the AC bus frequency.

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