Energy storage substation integrated control structure and flexible control method thereof

Abstract

The invention discloses an energy storage substation integrated control structure and a flexible control method thereof, and the control structure comprises an energy storage substation, and a droop control loop, a converter outer loop, a constant power loop and a converter inner loop which are used for integrated control. According to the control structure, indirect influence of the energy storage system on output of the energy storage transformer substation is considered, the overall output current of the energy storage transformer substation is fed forward, the energy storage system and the energy storage transformer substation are researched as an integrated system, and an integrated control scheme of the energy storage transformer substation configured with the energy storage system is provided. And a crucial energy-saving effect is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage substations, and in particular to an integrated control structure of an energy storage substation and a flexible control method thereof. Background Art

[0002] By the end of 2023, the total operating mileage of urban rail transit in my country has reached 11,232 kilometers. In 2023, the total power consumption of urban rail transit is about 24.97 billion kWh, of which traction energy consumption accounts for about 50% of the total energy consumption. With the widespread application of regenerative braking technology in urban rail transit trains, how to make full use of train regenerative braking energy is one of the key issues in the field of energy conservation in urban rail transit. According to statistics, regenerative braking energy can account for up to 20%-40% of traction energy consumption.

[0003] With the continuous development of energy storage technology, the regenerative braking energy recovery scheme based on energy storage system has received more and more attention. The ground-based energy storage system (wayside energy storage system) is generally composed of energy storage components (supercapacitors, flywheels, batteries, etc.) and energy storage converters. Since the energy storage system has available capacity limitations and the power that can be provided by energy storage components such as supercapacitors and flywheels is affected by the real-time capacity (or speed), the working conditions of the energy storage system will also affect the working conditions of the energy storage substation. Therefore, for the traction power supply system equipped with an energy storage system, its output characteristics are difficult to determine, which is fundamentally different from the reversible energy storage substation. The advantage of the latter is that the output characteristics are determined, and the optimal energy interaction within the TPSS can be achieved based on the optimal power flow method under the condition of known train conditions. Adequate feedback is achieved on the basis of reducing the generation of residual regenerative braking energy. At present, the energy management and control methods for urban rail transit energy storage systems are to simply treat it as a controlled energy storage device. The core control goal is to absorb the remaining regenerative braking energy in the TPSS and release it when there is a traction demand. Essentially, it is about how to improve the utilization of the remaining regenerative braking energy, without considering the active regulation of the system power. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides an integrated control structure of an energy storage substation and a flexible control method thereof, which solves the problem that the existing energy storage substation control structure does not consider the active regulation of the system flow.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: to provide an integrated control structure of an energy storage substation, including: an energy storage substation and a droop control loop for integrated control, a converter outer loop, a constant power loop and a converter inner loop;

[0006] The energy storage substation includes a loop-connected energy storage system, a bidirectional DCDC converter and a rectifier;

[0007] The droop control loop is used to output the energy storage substation voltage command value according to the virtual voltage source, the virtual resistance and the energy storage substation current;

[0008] The converter outer loop is used to output the current instruction of the energy storage system according to the voltage instruction value of the energy storage substation, the rectifier current and the voltage of the energy storage substation;

[0009] The constant power loop is used to output the current command value of the energy storage system on the energy storage side according to the current command of the energy storage system, the voltage of the energy storage substation and the voltage of the energy storage system on the energy storage side;

[0010] The inner loop of the converter is used to output the integrated control command of the energy storage substation according to the current command value of the energy storage system on the energy storage side and the current of the energy storage system on the energy storage side.

[0011] Further: the current instruction i of the energy storage system output by the converter outer loop wess The expression is:

[0012]

[0013] Among them, i sub is the rectifier current, is the current command value of the energy storage substation, PI(.) represents proportional-integral control, is the voltage command value of the energy storage substation, u esub is the voltage of the energy storage substation.

[0014] Furthermore: the constant power loop includes a power threshold that is dynamically adjusted according to the real-time capacity state SOC of the energy storage system , whose expression is:

[0015]

[0016] Among them, P es,max is the maximum design power of the energy storage system, u es is the voltage on the energy storage side of the energy storage system, u sc,max is the maximum voltage at the energy storage side.

[0017] Furthermore: The output of the energy storage substation includes 5 working modes, namely:

[0018] Exit working mode, the triggering conditions are: when the SOC reaches the upper or lower limit, and when the traction network voltage is higher than the no-load voltage of the energy storage substation itself;

[0019] The substation independent working mode is triggered when the SOC reaches the upper or lower limit, and the traction grid voltage is lower than the no-load voltage of the energy storage substation itself;

[0020] Voltage regulation mode, triggered by: when the energy storage system has available capacity and does not reach the power threshold hour;

[0021] Non-voltage regulation joint working mode, the triggering condition is: when the energy storage system reaches the power threshold , and the traction grid voltage is lower than the no-load voltage of the energy storage substation itself;

[0022] The non-voltage-regulated energy storage system operates independently. The triggering condition is: when the energy storage system reaches the power threshold , and the traction network voltage is higher than the no-load voltage of the energy storage substation itself.

[0023] Further: The output expression of exiting the working mode is: i esub =0i esub =0;

[0024] The output expression of the substation independent working mode is:

[0025] The output expression of the voltage regulation mode is:

[0026] The output expression of the non-voltage-regulated common working mode is:

[0027] The output expression of the independent working mode of the non-voltage-regulated energy storage system is:

[0028] Among them, i esub is the output of the energy storage substation, is a virtual voltage source, is the virtual resistance, u s0 is the no-load voltage, r s0 is the equivalent internal resistance of the substation.

[0029] The present application also provides a flexible control method for an integrated control structure of an energy storage substation, which is applied to a multi-station and multi-train urban rail DC traction power supply system, including:

[0030] S1. Perform a global search on the urban rail DC traction power supply system through a genetic algorithm to determine the optimization parameters;

[0031] S2. Perform local optimization based on the optimization parameters to obtain the target result;

[0032] S3. Use the target results to optimize the urban rail DC traction power supply system.

[0033] Further: S1 includes:

[0034] S11, performing a global search on the urban rail DC traction power supply system by using a genetic algorithm to obtain dynamic parameters;

[0035] S12, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system;

[0036] S13. Determine whether the iteration goal has been achieved:

[0037] If so, the result of the power flow calculation is used as the optimization parameter;

[0038] If not, the dynamic parameters are updated according to the result of the power flow calculation, and the process returns to S12.

[0039] Further: S2 includes:

[0040] S21, performing local optimization on the optimization parameters by using a nonlinear precise optimization algorithm;

[0041] S22, updating dynamic parameters according to the result of local optimization;

[0042] S23, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system;

[0043] S24. Determine whether the iteration goal has been achieved:

[0044] If yes, the result after power flow calculation is taken as the target result;

[0045] If not, the optimization parameters are updated according to the results of the power flow calculation, and the process returns to S21.

[0046] Further: In S2, the target result satisfies:

[0047]

[0048] Among them, Min means minimization, E sys represents the total energy consumption of the traction power supply system, M is the number of stations, N is the number of trains; T is the operation cycle, P sub,m is the power of energy storage substation, P br,loss,n is the train braking resistor power, P l,loss is the line resistance power.

[0049] Further: In S12 and S23, the constraints of the rail DC traction power supply system are:

[0050]

[0051] SOC min ≤SOC≤SOC max

[0052] U dc,min ≤U t ≤U br,lim

[0053] Among them, P esub,i represents the total power of the energy storage substation at the traction grid node i, P t,i represents the train power at traction network node i, G dcij represents the admittance between nodes i and j in the traction network, U dc,i and U dc,j They represent the voltage at node i and node j of the traction network, respectively, and U t Indicates the voltage at the pantograph of the train, SOC min and SOC max Represent the minimum and maximum values ​​of SOC, U dc,min Indicates the minimum voltage under normal train operation conditions, U br,lim Indicates the upper limit of the braking resistor's operating voltage.

[0054] The beneficial effects of the present invention are:

[0055] 1. An integrated control structure of energy storage substation is proposed, which takes into account the indirect impact of the energy storage system on the working characteristics of the energy storage substation, samples the feedback quantity of the energy storage substation as a whole, and then realizes the overall control of the energy storage substation through integrated control instructions;

[0056] 2. A flexible control method for energy storage substation is proposed. Different from the reversible energy storage substation in the general flexible traction power supply system, the energy storage devices such as supercapacitors and flywheels commonly used in urban rail transit can provide power coupled with real-time capacity, and when the energy storage system has no available capacity, the energy storage substation will switch the working mode. The proposed method realizes a unified description of the output characteristics of the energy storage substation;

[0057] 3. An optimal power flow algorithm based on integrated flexible control of energy storage substation is proposed. The energy saving of urban rail traction power supply system is taken as the first priority goal, and the control parameters of the energy storage substation are optimized, which greatly improves the energy efficiency performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is the integrated control structure diagram of the energy storage substation.

[0059] Figure 2 This is a diagram of the optimal power flow algorithm framework method.

[0060] Figure 3 This is the flow optimization effect diagram of the DC traction power supply system.

[0061] Figure 4 This is the voltage waveform of the traction network. DETAILED DESCRIPTION

[0062] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0063] Traditional ground-based energy storage systems are used to connect energy storage elements to the DC traction grid through energy storage inverters. Taking common supercapacitor or battery energy storage as an example, they are connected to the grid through a bidirectional DCDC converter. Energy storage inverters currently widely use a traditional dual-loop control structure based on a voltage outer loop and a current inner loop (or variants such as a power loop).

[0064] Therefore, the analysis of the output external characteristics of the energy storage system on the traction grid side is always coupled with the energy storage side, and does not consider the output characteristics of the entire traction substation. Therefore, it is not clear what the actual output characteristics of the energy storage system and the substation are, and what the output characteristics of the entire traction power supply system are at this time.

[0065] In order to solve the above problems, Figure 1 As shown, in one embodiment of the present invention, an integrated control structure of an energy storage substation is provided, comprising: an energy storage substation and a droop control loop, a converter outer loop, a constant power loop and a converter inner loop for integrated control;

[0066] The energy storage substation includes a loop-connected energy storage system, a bidirectional DCDC converter and a rectifier;

[0067] The droop control loop (DroopControlLoop) is used to output the voltage command value of the energy storage substation according to the virtual voltage source, the virtual resistance and the energy storage substation current;

[0068] The converter outer loop (ConverterOuterLoop) is used to output the current instruction of the energy storage system according to the voltage instruction value of the energy storage substation, the rectifier current and the energy storage substation voltage;

[0069] The constant power loop (ConstantPowerLoop) is used to output the current command value of the energy storage system on the energy storage side according to the current command of the energy storage system, the voltage of the energy storage substation and the voltage of the energy storage system on the energy storage side;

[0070] The converter inner loop (ConverterInnerLoop) is used to output the integrated control command of the energy storage substation according to the current command value of the energy storage system on the energy storage side and the current of the energy storage system on the energy storage side.

[0071] The object of the integrated control structure of the energy storage substation provided by the present invention is the energy storage system, taking into account the indirect impact of the energy storage system on the substation output, and feeding forward the overall output current of the energy storage substation.

[0072] Specifically, the current command i of the energy storage system output by the converter outer loop is wess The expression is:

[0073]

[0074] Among them, i sub is the rectifier current, is the current command value of the energy storage substation, PI(.) represents proportional-integral control, is the voltage command value of the energy storage substation, u esub is the voltage of the energy storage substation.

[0075] At the same time, the constant power loop includes a power threshold that is dynamically adjusted according to the real-time capacity state SOC of the energy storage system. , which is used to decouple the coupling relationship between the external characteristics of the energy storage substation output and the energy storage side, and its expression is:

[0076]

[0077] Among them, P es,max is the maximum design power of the energy storage system, determined during the design phase, u es is the voltage on the energy storage side of the energy storage system, u sc,max is the maximum voltage at the energy storage side.

[0078] The output of the energy storage substation includes 5 working modes:

[0079] Exit working mode, the triggering conditions are: when the SOC reaches the upper or lower limit, and when the traction network voltage is higher than the no-load voltage of the energy storage substation itself;

[0080] The substation works independently, and the triggering conditions are: when the SOC reaches the upper or lower limit, and the traction grid voltage is lower than the no-load voltage of the energy storage substation itself, the substation works independently, and the energy storage system does not participate in the work;

[0081] Voltage regulation mode, triggered by: when the energy storage system has available capacity and does not reach the power threshold

[0082] hour;

[0083] Non-voltage regulation joint working mode, the triggering condition is: when the energy storage system reaches the power threshold , and the traction grid voltage is lower than the no-load voltage of the energy storage substation itself;

[0084] The non-voltage-regulated energy storage system operates independently. The triggering condition is: when the energy storage system reaches the power threshold

[0085] , and the traction network voltage is higher than the no-load voltage of the energy storage substation itself.

[0086] Based on the above analysis, the output expression of exiting the working mode is: esub =0i esub =0;

[0087] The output expression of the substation independent working mode is:

[0088] The output expression of the voltage regulation mode is:

[0089] The output expression of the non-voltage-regulated common working mode is:

[0090] The output expression of the independent working mode of the non-voltage-regulated energy storage system is:

[0091] Among them, i esub is the output of the energy storage substation, is a virtual voltage source, is the virtual resistance, u s0 is the no-load voltage, r s0 is the equivalent internal resistance of the substation.

[0092] In the voltage regulation mode of energy storage substation, by controlling the parameters and It can adjust the output voltage reference value and slope of the energy storage substation. In the non-voltage regulation common working mode or independent working mode, the dynamic adjustment The overall control of the external characteristics of the energy storage substation output can also be achieved. That is to say, based on the proposed integrated control structure and control method of the energy storage substation, as long as the energy storage system still has residual capacity before it is completely out of operation, the integrated control of the output characteristics of the energy storage substation can be achieved.

[0093] Therefore, the method proposed in this patent completes the unified establishment of the energy storage substation control model, and decouples the traction grid side from the energy storage side, which can achieve flexible adjustment of the output external characteristics of the energy storage substation to a certain extent.

[0094] like Figure 2As shown, based on the established steady-state equivalent model of energy storage substation and the optimal power flow algorithm (OPF), flexible control is performed, and a flexible control method for the integrated control structure of energy storage substation is provided, which is applied to the urban rail DC traction power supply system with multiple stations and multiple trains, including:

[0095] S1. Perform a global search on the urban rail DC traction power supply system through a genetic algorithm to determine the optimization parameters;

[0096] S2. Perform local optimization based on the optimization parameters to obtain the target result;

[0097] S3. Use the target results to optimize the urban rail DC traction power supply system.

[0098] That is, step S1 is used as the outer layer OPF, and step S2 is used as the inner layer OPF.

[0099] Specifically, S1 includes:

[0100] S11, performing a global search on the urban rail DC traction power supply system by using a genetic algorithm to obtain dynamic parameters;

[0101] S12, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system;

[0102] S13. Determine whether the iteration goal has been achieved:

[0103] If so, the result of the power flow calculation is used as the optimization parameter;

[0104] If not, the dynamic parameters are updated according to the results of the power flow calculation, and the process returns to S12;

[0105] Specifically, the iteration target in S13 is the total energy consumption E of the traction power supply system sys No longer falling.

[0106] S2 includes:

[0107] S21, performing local optimization on the optimization parameters by using a nonlinear precise optimization algorithm;

[0108] S22, updating dynamic parameters according to the result of local optimization;

[0109] S23, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system;

[0110] S24. Determine whether the iteration goal has been achieved:

[0111] If yes, the result after power flow calculation is taken as the target result;

[0112] If not, the optimization parameters are updated according to the results of the power flow calculation, and the process returns to S21.

[0113] Specifically, the iteration target in S24 is the same as that in S13, which is the total energy consumption of the traction power supply system E sys The difference is that the outer iterative optimization (S1) is to search for the initial value in a large range, while the inner iterative optimization (S2) is to search for the precise optimization in a small range based on the initial value.

[0114] The dynamic parameters that need to be optimized in OPF are:

[0115] in, and They are the reference voltage and equivalent internal resistance in the integrated control link of the energy storage substation at the Mth station;

[0116] The optimization objectives of the DC traction power supply system OPF equipped with energy storage substation are:

[0117]

[0118] Among them, Min means minimization, M is the number of stations, N is the number of trains; T is the operation cycle, P sub,m is the power of energy storage substation, P br,loss,n is the train braking resistor power, P l,loss is the line resistance power;

[0119] Since the flexible control method of the integrated control structure of the energy storage substation is based on a double-layer OPF structure, the target result obtained in S2 also satisfies the above formula.

[0120] Specifically, in S12 and S23, the constraints of the rail DC traction power supply system are:

[0121]

[0122] SOC min ≤SOC≤SOC max

[0123] U dc,min ≤U t ≤U br,lim

[0124] Among them, P esub,i represents the total power of the energy storage substation at the traction grid node i, P t,i represents the train power at traction network node i, G dcij represents the admittance between nodes i and j in the traction network, U dc,i and U dc,j They represent the voltage at node i and node j of the traction network, respectively, and U t Indicates the voltage at the pantograph of the train, SOCmin and SOC max Represent the minimum and maximum values ​​of SOC, U dc,min Indicates the minimum voltage under normal train operation conditions, U br,lim Indicates the upper limit of the braking resistor's operating voltage.

[0125] In one embodiment of the present invention, taking a subway line in Beijing as an example, a simulation model of the traction power supply system under multi-vehicle operation conditions is constructed based on actual line conditions. A ground-based supercapacitor energy storage system is configured at each station along the entire line, thus constituting a total of 5 energy storage substations. The differences in no-load voltages of each substation are taken into account, and the traction power supply system and train parameters are obtained based on actual measurements. The line and train parameter configurations are shown in Tables 1 and 2 below.

[0126] Table 1 Line parameters

[0127]

[0128] Table 2 Vehicle parameters

[0129]

[0130] The energy storage system parameter configuration is shown in Table 3 below. In order to simplify the operation process, the power threshold that the energy storage system can provide is the minimum value within the normal working range, that is, the power threshold is a fixed value. In this way, even if real-time sampling and tracking of SOC is not performed, the decoupling of the traction grid side and the energy storage side can still be achieved. Power threshold in case analysis It can be calculated based on the following formula.

[0131] Table 3. Energy storage parameters

[0132]

[0133] The proposed integrated flexible control method for energy storage substations is adopted. In order to reduce the scale of parameter optimization, the control variables of the five energy storage substations on the entire line are kept consistent and optimized uniformly.

[0134] In order to intuitively demonstrate the effect of power flow optimization, the train power in the entire power supply section at any time is summed up to simplify it as the remaining traction and braking power demand after the train power interaction. The power demand in TPSS is compared with the sum of the powers of the energy storage substations on the entire line. It can be seen from the figure below that based on the proposed method, the TPSS power flow can fully adapt to the load demand in the system. When there is still residual regenerative braking energy in the system after train interaction (P<0), the energy storage substation fully recovers it; when there is residual traction energy demand (P>0), the energy storage substation outputs energy to supplement it. The power flow optimization effect of the DC traction power supply system is as follows. Figure 3 shown.

[0135] like Figure 4 The following table shows the traction network voltage measured at each station. It can be seen that the traction network voltage is maintained at a low level overall, and only rarely reaches the braking resistor starting voltage. This is also consistent with the results in the above table, and almost no energy is lost in the braking resistor. At the same time, the traction network voltage shows good voltage stabilization characteristics for most of the time, and the minimum traction network voltage is 797V.

[0136] Table 4 shows the energy-saving performance of the traction power supply system equipped with an energy storage system when controlled based on different strategies. The following three methods are compared:

[0137] Strategy 1: The EMS sets the charging and discharging thresholds of the energy storage system based on the substation no-load voltage. This is also the most widely used strategy in practice.

[0138] Strategy 2: Optimize the charging and discharging thresholds of the energy storage system based on the heuristic optimization algorithm, and independently optimize the thresholds of the energy storage system configured at each station using a distributed optimization method.

[0139] Strategy 3: Based on the method proposed in this patent.

[0140] Table 4 Optimization results of energy consumption of traction power supply system

[0141]

[0142] The results show that compared with the case where no energy storage system is configured, the method proposed in this patent shows the highest energy saving performance, with an energy saving rate of up to 30%. Compared with the energy management strategy based on no-load voltage and heuristic optimization algorithm optimization under isolated control schemes in the past, the proposed method has improved the energy saving rate by 9% and 3%, respectively. After adopting the proposed method, the energy consumption of the traction substation was reduced by 10% and 4%, respectively. In addition, from the perspective of braking resistor energy consumption, the energy consumption was reduced by 89% and 53%, respectively, after adopting the proposed method. The above results show that the integrated flexible control method of the energy storage substation proposed in this patent and its double-layer OPF strategy can not only reduce the output energy of the traction substation, but also greatly reduce the energy loss on the braking resistor, thereby reducing the waste of regenerative braking energy.

[0143] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application 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 of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An integrated control structure of an energy storage substation, characterized in that: include: Energy storage substation and a droop control loop, a converter outer loop, a constant power loop and a converter inner loop for integrated control; The energy storage substation includes a loop-connected energy storage system, a bidirectional DCDC converter and a rectifier; The droop control loop is used to output the energy storage substation voltage command value according to the virtual voltage source, the virtual resistance and the energy storage substation current; The converter outer loop is used to output the current instruction of the energy storage system according to the voltage instruction value of the energy storage substation, the rectifier current and the voltage of the energy storage substation; The constant power loop is used to output the current command value of the energy storage system on the energy storage side according to the current command of the energy storage system, the voltage of the energy storage substation and the voltage of the energy storage system on the energy storage side; The inner loop of the converter is used to output the integrated control command of the energy storage substation according to the current command value of the energy storage system on the energy storage side and the current of the energy storage system on the energy storage side.

2. The integrated control structure of energy storage substation according to claim 1 is characterized in that: The current command i of the energy storage system output by the converter outer loop wess The expression is: Among them, i sub is the rectifier current, is the current command value of the energy storage substation, PI(.) represents proportional-integral control, is the voltage command value of the energy storage substation, u esub is the voltage of the energy storage substation.

3. The integrated control structure of energy storage substation according to claim 2 is characterized in that: The constant power loop includes a power threshold that is dynamically adjusted according to the real-time capacity state SOC of the energy storage system. Its expression is: Among them, P es,max is the maximum design power of the energy storage system, u es is the voltage on the energy storage side of the energy storage system, u sc,max is the maximum voltage at the energy storage side.

4. The integrated control structure of energy storage substation according to claim 3 is characterized in that: The output of the energy storage substation includes 5 working modes: Exit working mode, the triggering conditions are: when the SOC reaches the upper or lower limit, and when the traction network voltage is higher than the no-load voltage of the energy storage substation itself; The substation independent working mode is triggered when the SOC reaches the upper or lower limit, and the traction grid voltage is lower than the no-load voltage of the energy storage substation itself; Voltage regulation mode, triggered by: when the energy storage system has available capacity and does not reach the power threshold hour; Non-voltage regulation joint working mode, the triggering condition is: when the energy storage system reaches the power threshold And the traction grid voltage is lower than the no-load voltage of the energy storage substation itself; The non-voltage-regulated energy storage system operates independently. The triggering condition is: when the energy storage system reaches the power threshold And the traction network voltage is higher than the no-load voltage of the energy storage substation itself.

5. The integrated control structure of energy storage substation according to claim 4 is characterized in that: The output expression of exiting working mode is: esub =0i esub =0; The output expression of the substation independent working mode is: The output expression of the voltage regulation mode is: The output expression of the non-voltage-regulated common working mode is: The output expression of the independent working mode of the non-voltage-regulated energy storage system is: Among them, i esub is the output of the energy storage substation, is a virtual voltage source, is the virtual resistance, u s0 is the no-load voltage, r s0 is the equivalent internal resistance of the substation.

6. A flexible control method for an integrated control structure of an energy storage substation, based on the integrated control structure of an energy storage substation according to any one of claims 1 to 5, characterized in that: The urban rail DC traction power supply system used for multiple stations and multiple trains includes: S1. Perform a global search on the urban rail DC traction power supply system through a genetic algorithm to determine the optimization parameters; S2. Perform local optimization based on the optimization parameters to obtain the target result; S3. Use the target results to optimize the urban rail DC traction power supply system.

7. The flexible control method of the integrated control structure of the energy storage substation according to claim 6 is characterized in that: S1 includes: S11, performing a global search on the urban rail DC traction power supply system by using a genetic algorithm to obtain dynamic parameters; S12, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system; S13. Determine whether the iteration goal has been achieved: If so, the result of the power flow calculation is used as the optimization parameter; If not, the dynamic parameters are updated according to the result of the power flow calculation, and the process returns to S12.

8. The flexible control method of the integrated control structure of the energy storage substation according to claim 6 is characterized in that S2 include: S21, performing local optimization on the optimization parameters by using a nonlinear precise optimization algorithm; S22, updating dynamic parameters according to the result of local optimization; S23, performing power flow calculation according to dynamic parameters and constraints of the rail DC traction power supply system; S24. Determine whether the iteration goal has been achieved: If yes, the result after power flow calculation is taken as the target result; If not, the optimization parameters are updated according to the results of the power flow calculation, and the process returns to S21.

9. The flexible control method of the integrated control structure of the energy storage substation according to claim 6 is characterized in that: In S2, the target result satisfies: Among them, Min means minimization, E sys represents the total energy consumption of the traction power supply system, M is the number of stations, N is the number of trains; T is the operation cycle, P sub,m is the power of energy storage substation, P br,loss,n is the train braking resistor power, P l,loss is the line resistance power.

10. The flexible control method of the integrated control structure of the energy storage substation according to any one of claims 7 or 8, characterized in that: In S12 and S23, the constraints of the rail DC traction power supply system are: SOC min ≤SOC≤SOC max IN dc,min ≤U t ≤U br,lim Among them, P esub,i represents the total power of the energy storage substation at the traction grid node i, P t,i represents the train power at traction network node i, G dcij represents the admittance between nodes i and j in the traction network, U dc,i and U dc,j They represent the voltage at node i and node j of the traction network, respectively, and U t Indicates the voltage at the pantograph of the train, SOC min and SOC max Represent the minimum and maximum values ​​of SOC, U dc,min Indicates the minimum voltage under normal train operation conditions, U br,lim Indicates the upper limit of the braking resistor's operating voltage.

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