Control system, method and energy storage system for an energy storage system

Abstract

The embodiment of the application provides a kind of energy storage system control system, method and energy storage system, the system includes: mode selection module, voltage closed loop control module, dynamic limit power control module, current closed loop control module and PWM modulation module;Mode selection module is used to determine the working mode of energy storage capacitor and voltage given value;Voltage closed loop control module is used to calculate voltage deviation value, and current control value is determined according to voltage deviation value;Dynamic limit power control module is used to determine current given value according to current limit value or current control value, and current limit value is the ratio of preset charge-discharge power of energy storage capacitor and terminal voltage of energy storage capacitor, and preset charge-discharge power is determined by charge-discharge power function;Current closed loop control module is used to calculate current deviation value, and modulation wave is obtained according to current deviation value;PWM modulation module is used to determine converter control pulse according to modulation wave, to control energy storage capacitor, improve the energy-saving effect and voltage stabilizing effect of energy storage system.

Description

Technical Field

[0001] This application relates to the field of capacitor energy storage control technology, and in particular to a control system, method and energy storage system for an energy storage system. Background Technology

[0002] Introducing supercapacitor energy storage systems into urban rail transit power supply systems to store train braking energy for use during train traction not only saves energy but also helps maintain grid voltage stability, and has broad application potential in the urban rail transit field.

[0003] Most existing supercapacitor energy storage systems employ current-limiting control strategies. During train traction, as speed increases, the required traction power also gradually increases. However, under current-limiting control, the power released by the supercapacitor gradually decreases as the capacitor voltage decreases, resulting in insufficient traction force for the train. During train braking, as train speed gradually decreases, the braking power also gradually decreases. However, under current-limiting control, the power absorbed by the supercapacitor gradually increases as the capacitor voltage rises, which is inconsistent with the train's operating characteristics and fails to achieve the ideal voltage stabilization and energy-saving effects. Summary of the Invention

[0004] This application provides a control system, method, and energy storage system for an energy storage system, and provides a dynamic power control strategy that improves the voltage regulation effect of the energy storage capacitor and the energy utilization rate of the energy storage system.

[0005] In a first aspect, embodiments of this application provide a control system for an energy storage system, the control system comprising: a mode selection module, a voltage closed-loop control module, a dynamic power limiting control module, a current closed-loop control module, and a PWM modulation module;

[0006] The mode selection module is used to determine the operating mode and voltage setpoint of the energy storage capacitor of the energy storage system based on the grid voltage of the traction power supply network.

[0007] The voltage closed-loop control module is used to calculate the voltage deviation between the voltage setpoint and the grid voltage, and to determine the current control value based on the voltage deviation.

[0008] The dynamic power limiting control module is used to determine the current setpoint based on the current limit value or the current control value, wherein the current limit value is the ratio of the preset charging and discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor, and the preset charging and discharging power is determined by the charging and discharging power function, which is used to describe the correspondence between the preset charging and discharging power and time.

[0009] The current closed-loop control module is used to determine the current deviation value based on the current setpoint and the current value of the energy storage capacitor, and to obtain the modulation wave based on the current deviation value.

[0010] The PWM modulation module is used to determine the converter control pulse based on the modulation wave, so as to control the charging and discharging current of the energy storage capacitor in the operating mode according to the control pulse.

[0011] Optionally, the dynamic power limiting control module is specifically used for:

[0012] When the current control value is less than the current limit value, the current control value is determined to be the current setpoint value;

[0013] When the current control value is greater than or equal to the current limit value, the current limit value is determined to be the current setpoint value;

[0014] The expression for the current limiting value is: I SC_lim (t)=P SC_lim (t) / U SC (t), P SC_lim (t) represents the preset charging / discharging power at time t, U SC (t) represents the terminal voltage of the energy storage capacitor at time t.

[0015] Optionally, the control system further includes;

[0016] The state of charge limiting module is used to set the current setpoint to 0 when the remaining charge of the energy storage capacitor is higher than a first charge threshold or lower than a second charge threshold.

[0017] Optionally, the control system further includes:

[0018] The current setpoint adjustment module is used to adjust the current setpoint based on the remaining charge of the energy storage capacitor according to a preset setpoint adjustment formula after determining the current setpoint according to the current limit value or the current control value, so as to obtain the adjusted current setpoint.

[0019] Accordingly, the current closed-loop control module is specifically used for:

[0020] The current deviation value is determined based on the adjusted current setpoint and the current value of the energy storage capacitor, and the modulation wave is obtained based on the current deviation value.

[0021] Optionally, the preset given value adjustment formula is:

[0022] I ref ** (t)=I ref *(t)×K SOC

[0023] Among them, I ref * (t) is the current given value at time t; I ref ** (t) is the adjusted current setpoint; when the operating mode is charging mode, K SOC The expression is: When the operating mode is discharge mode, K SOC The expression is: Wherein, SOC is the square of the ratio of the terminal voltage of the energy storage capacitor to the maximum allowable terminal voltage.

[0024] Optionally, the mode selection module is specifically used for:

[0025] When the grid voltage is greater than the charging voltage threshold of the energy storage capacitor but less than the maximum allowable grid voltage, the operating mode of the energy storage capacitor is determined to be the charging mode, and the voltage setpoint is the charging setpoint.

[0026] When the grid voltage is greater than the minimum allowable grid voltage and less than the discharge voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined to be the discharge mode, and the voltage setpoint is the discharge setpoint.

[0027] Optionally, the voltage closed-loop control module includes a voltage deviation calculation module and a voltage PI adjustment module;

[0028] The voltage deviation calculation module is used to calculate the voltage deviation between the voltage setpoint and the grid voltage.

[0029] The voltage PI regulation module is used to determine the current control value based on the voltage deviation value, so as to realize closed-loop control of the grid voltage.

[0030] Optionally, the charge / discharge power function is determined by the following expression:

[0031]

[0032]

[0033]

[0034] T0+ΔT≤T max

[0035] Where t0 is the control cycle of the energy storage capacitor; Δt is the operating cycle of the energy storage capacitor, wherein both the charging and discharging cycles are 0.5Δt; C is the capacitance value of the energy storage capacitor; 0 is the initial time, t∈(0, 0.5Δt); U SC (t) represents the terminal voltage of the energy storage capacitor at time t, and the initial voltage U... SC The value of (t) is U SC0 ;P SC_lim (t) represents the preset charging and discharging power of the energy storage capacitor at time t; R es R is the internal resistance of the energy storage capacitor; ca The typical thermal resistance of the energy storage capacitor is ΔT; ΔT is the temperature rise of the energy storage capacitor within one control cycle t0; T0 is the initial temperature of the energy storage capacitor; T max I represents the highest operating temperature of the energy storage capacitor. RMS The effective value of the current of the stored energy is given.

[0036] Secondly, this application also provides a control method for an energy storage system, the control method comprising:

[0037] The operating mode and voltage setpoint of the energy storage capacitor of the energy storage system are determined by the mode selection module based on the grid voltage of the traction power supply network.

[0038] The voltage deviation between the voltage setpoint and the grid voltage is calculated via the voltage closed-loop control module, and the current control value is determined based on the voltage deviation.

[0039] The current setpoint is determined by the dynamic power limiting control module based on the current limit value or the current control value. The current limit value is the ratio of the preset charging and discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor. The preset charging and discharging power is determined by the charging and discharging power function, which describes the correspondence between the preset charging and discharging power and time.

[0040] The current deviation value is determined based on the current setpoint and the current value of the energy storage capacitor via the current closed-loop control module, and the modulation wave is obtained based on the current deviation value.

[0041] The converter control pulse is determined based on the modulation wave via the PWM modulation module, so as to control the charging and discharging current of the energy storage capacitor in the operating mode according to the control pulse.

[0042] Optionally, determining the operating mode and voltage setpoint of the energy storage capacitor of the energy storage system based on the grid voltage of the traction power supply network includes:

[0043] When the grid voltage is greater than the charging voltage threshold of the energy storage capacitor but less than the maximum allowable grid voltage, the operating mode of the energy storage capacitor is determined to be the charging mode, and the voltage setpoint is the charging setpoint.

[0044] When the grid voltage is greater than the minimum allowable grid voltage and less than the discharge voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined to be the discharge mode, and the voltage setpoint is the discharge setpoint.

[0045] Optionally, the voltage closed-loop control module includes a voltage deviation calculation module and a voltage PI regulation module. The calculation of the voltage deviation between the voltage setpoint and the grid voltage includes:

[0046] The voltage deviation calculation module calculates the voltage deviation between the voltage setpoint and the grid voltage.

[0047] Determining the current control value based on the voltage deviation value includes:

[0048] The voltage PI regulation module determines the current control value based on the voltage deviation value to achieve closed-loop control of the grid voltage.

[0049] Optionally, determining the current setpoint based on the current limit value or the current control value includes:

[0050] When the current control value is less than the current limit value, the current control value is determined to be the current setpoint value;

[0051] When the current control value is greater than or equal to the current limit value, the current limit value is determined to be the current setpoint value;

[0052] The expression for the current limiting value is: I SC_lim (t)=P SC_lim (t) / U SC (t), P SC_lim (t) represents the preset charging / discharging power at time t, U SC (t) represents the terminal voltage of the energy storage capacitor at time t.

[0053] Optionally, the dynamic power limiting control module further includes a state of charge limiting module, and the control method further includes:

[0054] The current setpoint is set to 0 when the remaining charge of the energy storage capacitor is higher than a first charge threshold or lower than a second charge threshold, via the state of charge limiting module.

[0055] Optionally, after determining the current setpoint based on the current limit value or the current control value, the method further includes:

[0056] Based on the preset given value adjustment formula, the current given value is adjusted according to the remaining charge of the energy storage capacitor to obtain the adjusted current given value;

[0057] Accordingly, determining the current deviation value based on the given current value and the current value of the energy storage capacitor includes:

[0058] The current deviation value is determined based on the adjusted current setpoint and the current value of the energy storage capacitor.

[0059] Optionally, the preset given value adjustment formula is:

[0060] I ref ** (t)=I ref * (t)×K SOC

[0061] Among them, I ref * (t) is the current given value at time t; I ref ** (t) is the adjusted current setpoint; when the operating mode is charging mode, K SOC The expression is: When the operating mode is discharge mode, K SOC The expression is: Wherein, SOC is the square of the ratio of the terminal voltage of the energy storage capacitor to the maximum allowable terminal voltage.

[0062] Optionally, the charge / discharge power function is determined by the following expression:

[0063]

[0064]

[0065]

[0066] T0+ΔT≤T max

[0067] Where t0 is the control cycle of the energy storage capacitor; Δt is the operating cycle of the energy storage capacitor, wherein both the charging and discharging cycles are 0.5Δt; C is the capacitance value of the energy storage capacitor; 0 is the initial time, t∈(0, 0.5Δt); U SC (t) represents the terminal voltage of the energy storage capacitor at time t, and the initial voltage U... SC The value of (t) is U SC0 ;P SC_lim(t) represents the preset charging and discharging power of the energy storage capacitor at time t; R es R is the internal resistance of the energy storage capacitor; ca The typical thermal resistance of the energy storage capacitor is ΔT; ΔT is the temperature rise of the energy storage capacitor within one control cycle t0; T0 is the initial temperature of the energy storage capacitor; T max I represents the highest operating temperature of the energy storage capacitor. RMS This is the effective value of the current in the energy storage capacitor.

[0068] Thirdly, this application provides an energy storage system, including: an energy storage capacitor and a control system for the energy storage system provided in any embodiment of this application.

[0069] Fourthly, this application provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the control method of the energy storage system provided in any embodiment of this application.

[0070] The control system, method, and energy storage system provided in this application embodiment offer a power control strategy for energy storage systems based on energy storage capacitors. A mode selection module determines the operating mode and given voltage value of the energy storage capacitor. A voltage closed-loop control module implements closed-loop control of the traction network voltage to achieve the desired given voltage value. Simultaneously, the voltage closed-loop control module outputs a current control value. A dynamic power limiting control module obtains the current limit value of the energy storage capacitor based on the ratio of a preset time-varying charging / discharging power to the terminal voltage across the energy storage capacitor. Based on this current limit value and the current control value, a current setpoint is determined. A current closed-loop control module then implements closed-loop control of the energy storage capacitor's current to achieve the desired current setpoint. A modulation wave is obtained based on the current deviation value. A PWM modulation module determines the control pulse for the energy storage capacitor's converter based on the modulation wave output by the current closed-loop control module, thereby controlling the charging and discharging of the energy storage capacitor. The technical solution of this application embodiment realizes dynamic control of the power of the energy storage capacitor, so that the energy storage capacitor can be charged and discharged at appropriate power during the train starting and braking stages, making the power curve of the energy storage capacitor more in line with the electric braking characteristics of the train, and improving the voltage stabilization performance and energy saving effect of the energy storage capacitor. Attached Figure Description

[0071] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0072] Figure 1 An application scenario diagram provided for an embodiment of this application;

[0073] Figure 2 This is a schematic diagram of the control system of an energy storage system provided in one embodiment of the present application;

[0074] Figure 3 A schematic diagram of the control system of an energy storage system provided in another embodiment of this application;

[0075] Figure 4 This application Figure 3 The illustrated embodiment provides a structural schematic diagram of a supercapacitor energy storage system and its control system.

[0076] Figure 5 A flowchart illustrating a control method for an energy storage system provided in one embodiment of this application;

[0077] Figure 6 This is a schematic diagram of the structure of an energy storage system provided in one embodiment of this application;

[0078] Figure 7 This is a schematic diagram of the structure of an electronic device provided in one embodiment of this application.

[0079] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0080] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0081] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0082] The application scenarios of the embodiments of this application are explained below:

[0083] Figure 1 An application scenario diagram provided for an embodiment of this application, such as Figure 1As shown, the energy storage system provided in this application embodiment is an energy storage system including an energy storage capacitor, such as a supercapacitor, specifically a supercapacitor energy storage system for rail transit. Train 110 operates on a designated track 130 according to a preset mode under the control of the traction power supply network 120. The operation of train 110 mainly includes three stages: the starting stage, the constant speed driving stage, and the braking stage. In the starting stage, the typical characteristics of train 110 operation are: initially, the traction power is relatively small, and as the speed of train 110 increases, the traction power gradually increases; in the braking stage, the typical characteristics of train 110 operation are: initially, the braking power is very large, and as the train speed decreases, the braking power gradually decreases. To improve energy recovery efficiency and ensure voltage stability during train operation at each stage, an energy storage system 140 needs to be designed to recover braking energy during train braking, improve energy utilization, and provide reliable traction force for the train during startup to ensure smooth train startup. In order to improve the performance of the energy storage system 140, a corresponding control system 150 needs to be designed for it, so as to control the charging and discharging processes of the energy storage system 140, realize the recovery of braking energy and provide reliable traction for the train.

[0084] However, existing energy storage systems employ current-limiting control. During train traction, the supercapacitor provides traction energy to the train at a constant current; during braking, it absorbs braking energy at a constant current. Under this current-limiting control strategy, the power characteristics of the energy storage capacitor change in the opposite direction to the train's power characteristics, failing to achieve effective voltage stabilization and energy saving.

[0085] The main concept of the control system for the energy storage system provided in this application is: based on a power-limited control method, a dynamic power control strategy is provided for the energy storage system, so that the energy storage capacitor can maintain a large charging and discharging power as much as possible under its allowable conditions, thereby improving energy utilization while effectively stabilizing the grid voltage.

[0086] Figure 2 This is a schematic diagram of the control system of an energy storage system provided in one embodiment of this application, as shown below. Figure 2 As shown, the control system of the energy storage system provided in this embodiment includes: a mode selection module 210, a voltage closed-loop control module 220, a dynamic power limiting control module 230, a current closed-loop control module 240, and a PWM modulation module 250.

[0087] The system comprises the following modules: a mode selection module 210 determines the operating mode and voltage setpoint of the energy storage capacitor based on the grid voltage of the traction power supply network; a voltage closed-loop control module 220 calculates the voltage deviation between the voltage setpoint and the grid voltage, and determines the current control value based on the voltage deviation; a dynamic power limiting control module 230 determines the current setpoint based on a current limit value or the current control value, wherein the current limit value is the ratio of the preset charging / discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor, and the preset charging / discharging power is determined by a charging / discharging power function, which describes the correspondence between the preset charging / discharging power and time; a current closed-loop control module 240 determines the current deviation based on the current setpoint and the current value of the energy storage capacitor, and obtains a modulation wave based on the current deviation; and a PWM modulation module 250 determines a converter control pulse based on the modulation wave, and controls the charging / discharging current of the energy storage capacitor in the operating mode according to the control pulse. The energy storage capacitor in this system can be a supercapacitor. Supercapacitors, also known as electrochemical capacitors, are power sources with unique properties that fall between traditional capacitors and batteries. They primarily store electrical energy through the electric double layer and redox capacitance. No chemical reaction occurs during the energy storage process, and the process is reversible, allowing for hundreds of thousands of charge-discharge cycles. The energy storage capacitor can be composed of m×n supercapacitor modules, where m and n represent the number of series and parallel connections, respectively. Each supercapacitor module has the same power output. This energy storage system can be used in rail transit, such as the energy storage system of subway trains. The grid voltage of the traction power supply network can be 1500V or other voltage values, determined by the specific circumstances. The voltage setpoint can be pre-stored in the mode selection module.

[0088] Specifically, the various modules of this control system can be integrated into a single chip or a single integrated circuit. The mode selection module can be a mode selection circuit composed of comparators; the voltage closed-loop control module can be a voltage closed-loop control circuit composed of a voltage deviation calculation circuit and a first PI controller; the power control module can be a power control circuit; and the current closed-loop control module can be a current closed-loop control circuit composed of a current deviation calculation circuit and a second PI controller.

[0089] Specifically, the mode selection module 210 can be composed of comparators to compare the collected grid voltage of the traction power supply network with preset voltage thresholds, thereby determining the working mode of the energy storage capacitor and the voltage setpoint of the voltage closed-loop control module 220 based on the comparison results.

[0090] Optionally, the mode selection module 210 is specifically used for:

[0091] When the grid voltage is greater than the charging voltage threshold of the energy storage capacitor and less than the maximum allowable grid voltage, the operating mode of the energy storage capacitor is determined to be the charging mode, and the voltage setpoint is the charging setpoint; when the grid voltage is greater than the minimum allowable grid voltage and less than the discharging voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined to be the discharging mode, and the voltage setpoint is the discharging setpoint.

[0092] Among these, the maximum permissible grid voltage refers to the maximum grid voltage allowed by the traction power supply network, while the minimum permissible grid voltage is the minimum grid voltage. The charging voltage threshold is the minimum voltage value of the energy storage capacitor in charging mode. The discharging voltage threshold is the maximum voltage value of the energy storage capacitor in discharging mode.

[0093] Specifically, when the train is braking, the mode selection module 210 outputs the charging mode; when the train is traction or starting, the mode selection module 210 outputs the discharging mode; and when the train is traveling at a constant speed, the mode selection module 210 outputs the standby mode, in which the energy storage capacitor neither discharges nor charges.

[0094] Specifically, the mode selection module 210 monitors the grid voltage of the traction power supply network in real time and determines the corresponding operating mode and voltage setpoint based on the range of the currently collected grid voltage. If the grid voltage U dc Located in [U char U max If the range is specified, the operating mode is determined to be charging mode, and the voltage setpoint is U. char_ref If the grid voltage U dc In (U) dis U char If the grid voltage U is within a certain range, the operating mode is determined to be standby mode, in which case the energy storage capacitor neither charges nor discharges; if the grid voltage U dc Located in [U min U dis If the range is specified, the operating mode is determined to be discharge mode, and the voltage setpoint is U. dis_ref , among which, U max To maximize the allowable network voltage, U char U is the charging voltage threshold. dis U is the discharge voltage threshold. min This is the minimum permissible voltage.

[0095] For example, the energy storage system could be a 1MW supercapacitor-based energy storage system operating at 1500V grid voltage, with a maximum permissible grid voltage U. max It can be 1900V, charging voltage threshold U char It can be 1700V, discharge voltage threshold Udis It can be 1600V, and the minimum allowable mains voltage can be 1000V.

[0096] Specifically, the voltage closed-loop control module 220 can be a closed-loop control module based on the PID control algorithm.

[0097] Specifically, the voltage closed-loop control module 220 can be a closed-loop control circuit that receives the voltage setpoint from the mode selection module 210 and, based on the difference between the voltage setpoint and the grid voltage, implements closed-loop control of the grid voltage to ensure that the grid voltage tracks the voltage setpoint and stabilizes the grid voltage. The voltage closed-loop control module 220 can consist of a differential circuit and a controller. The differential circuit calculates the difference between the grid voltage and the voltage setpoint. The controller can be a PI controller, PID controller, or other controller to determine the corresponding control quantity based on the difference between the grid voltage and the voltage setpoint, i.e., the current control value I of the subsequent dynamic power limiting control module 230. ref This is to control the grid voltage to remain near the given voltage value and achieve a stable state.

[0098] Specifically, the dynamic power limiting control module 230 is used to receive the current control value I from the voltage closed-loop control module 220. ref And determine the current limit value I for the current control cycle or the current moment. SC_lim According to the current control value I ref and current limit value I SC_lim Determine the current setpoint I of the current closed-loop control module 240 ref * Among them, the current limit value I SC_lim The expression is: I SC_lim (t)=P SC_lim (t) / U SC (t), where U SC (t) represents the terminal voltage across the energy storage capacitor at time t, P SC_lim (t) represents the preset charging and discharging power of the energy storage capacitor at time t. The function P... SC_lim (t) is the preset charging and discharging power function. It can be seen that the preset charging and discharging power may be different at different times. That is, the preset charging and discharging power is a changing power or dynamic power, rather than a fixed power value.

[0099] Furthermore, the charge / discharge power function P SC_lim (t) can be determined based on the temperature, terminal voltage, and charging / discharging current of the energy storage capacitor at time t.

[0100] Optionally, the dynamic power limiting control module 230 is specifically used for:

[0101] When the current control value is less than the current limit value, the current control value is determined to be the current setpoint; when the current control value is greater than or equal to the current limit value, the current limit value is determined to be the current setpoint; wherein, the expression for the current limit value is: I SC_lim (t)=P SC_lim (t) / U SC (t), P SC_lim (t) represents the preset charging / discharging power at time t, U SC (t) represents the terminal voltage of the energy storage capacitor at time t.

[0102] Specifically, the current setpoint I ref * The expression is:

[0103]

[0104] Wherein, the current setpoint I ref * (t) can omit the time variable t and be abbreviated as I. ref * .

[0105] Specifically, when the voltage closed-loop control module 220 outputs the current control value I... ref Less than the current limit value I SC_lim When the voltage deviation is small, it indicates that the current grid voltage is close to the voltage setpoint, and power limiting control is not required. Conventional closed-loop control can achieve voltage stabilization. However, when the current control value I... ref Greater than or equal to the current limit value I SC_lim When the voltage deviation is too large, it indicates that power control is needed by setting the charging and discharging power to quickly stabilize the grid voltage to the given voltage value and improve the voltage regulation performance of the energy storage capacitor.

[0106] Specifically, the current closed-loop control module 240 receives the current setpoint I from the dynamic power limiting control module 230. ref * Simultaneously, the charging and discharging current I of the energy storage capacitor is monitored in real time. SCThe difference between the two values ​​is calculated, which can be implemented using a differential circuit to obtain the current deviation value. Based on a current controller, such as a PI controller, PID controller, or other types of controller, the modulation wave of the PWM modulation module is determined according to this current deviation value to achieve closed-loop control of the charging and discharging current of the energy storage capacitor. This ensures that the current tracks the given current value and remains stable. The modulation wave of the PWM modulation module 250 is determined based on the current deviation value. Then, the control pulse of the switching transistor is obtained by comparing the modulation wave output by the PWM modulation module 250 with the carrier triangular wave. Specifically, the control pulse is high when the modulation wave amplitude is greater than the triangular wave, and low when the modulation wave amplitude is less than the triangular wave. This control pulse is the control pulse of the converter for the energy storage capacitor. Based on this control pulse, the converter controls the energy storage capacitor to release electrical energy to the traction power grid at the desired power, thereby achieving voltage regulation.

[0107] The control system of the energy storage system provided in this application provides a power control strategy for an energy storage system based on an energy storage capacitor. A mode selection module determines the operating mode and given voltage value of the energy storage capacitor. A voltage closed-loop control module implements closed-loop control of the traction network voltage to achieve the desired given voltage value. Simultaneously, a current control value is output via the voltage closed-loop control module. A dynamic power limiting control module obtains the current limit value of the energy storage capacitor based on the ratio of a preset time-varying charging / discharging power to the terminal voltage across the energy storage capacitor. Based on this current limit value and the current control value, a current setpoint is determined, and a current closed-loop control module implements closed-loop control of the energy storage capacitor's current to achieve the desired current setpoint. A modulation wave is obtained based on the current deviation value. A PWM modulation module determines the control pulse for the energy storage capacitor's converter based on the modulation wave output by the current closed-loop control module, thereby controlling the charging and discharging of the energy storage capacitor according to this control pulse. The technical solution of this application embodiment realizes dynamic control of the power of the energy storage capacitor, so that the energy storage capacitor can be charged and discharged at appropriate power during the train starting and braking stages, making the power curve of the energy storage capacitor more in line with the electric braking characteristics of the train, and improving the voltage stabilization performance and energy saving effect of the energy storage capacitor.

[0108] Figure 3 A schematic diagram of the control system of an energy storage system provided in another embodiment of this application is shown below. Figure 3 As shown, this embodiment is... Figure 2Based on the embodiment shown, the voltage closed-loop control module 220 is further refined, and a state of charge limiting module and a current setpoint adjustment module are added. The control system of the energy storage system provided in this embodiment includes: a mode selection module 310, a voltage deviation calculation module 321, a voltage PI adjustment module 322, a dynamic power limiting control module 330, a state of charge limiting module 340, a current setpoint adjustment module 350, a current closed-loop control module 360, and a PWM modulation module 370.

[0109] The mode selection module 310 is used to determine the operating mode of the energy storage capacitor as charging mode when the grid voltage is greater than the charging voltage threshold of the energy storage capacitor and less than the maximum allowable grid voltage, and the voltage setpoint is the charging setpoint value; when the grid voltage is greater than the minimum allowable grid voltage and less than the discharging voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined as discharging mode, and the voltage setpoint is the discharging setpoint value. The voltage deviation calculation module 321 is used to calculate the voltage deviation between the voltage setpoint value and the grid voltage. The voltage PI adjustment module 322 is used to determine the current control value based on the voltage deviation value to achieve closed-loop control of the grid voltage. The dynamic power limiting control module 330 is used to determine the current setpoint value based on the current limit value and the current control value, wherein the current limit value is the ratio of the preset charging / discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor, and the preset charging / discharging power is the ratio of the preset charging / discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor. The power is determined by a charge / discharge power function, which describes the correspondence between the preset charge / discharge power and time. A state-of-charge (SOC) limiting module 340 sets the current setpoint to 0 when the remaining charge of the energy storage capacitor is higher than a first charge threshold or lower than a second charge threshold. A current setpoint adjustment module 350, after determining the current setpoint based on the current limit value or the current control value, adjusts the current setpoint according to the remaining charge of the energy storage capacitor based on a preset setpoint adjustment formula to obtain the adjusted current setpoint. A current closed-loop control module 360 ​​determines the current deviation value based on the adjusted current setpoint and the current value of the energy storage capacitor, and obtains a modulation wave based on the current deviation value. A PWM modulation module 370 determines the converter control pulse based on the modulation wave, and controls the charge / discharge current of the energy storage capacitor in the operating mode according to the control pulse.

[0110] Specifically, the state of charge (SOC) limiting module 340 can be integrated into the dynamic power limiting control module 330. It is mainly used to flexibly disconnect the energy storage capacitor when its remaining charge or SOC is too high or too low, preventing overcharging or over-discharging and protecting the energy storage capacitor. This flexible disconnection avoids impact when the energy storage system exits the traction power grid.

[0111] Specifically, the current setpoint adjustment module 350 receives the remaining charge SOC output by the state of charge limiting module 340, and adjusts the current setpoint based on the preset setpoint adjustment formula and SOC.

[0112] Optionally, the preset given value adjustment formula is:

[0113] I ref ** (t)=I ref * (t)×K SOC

[0114] Among them, I ref * (t) is the current given value at time t; I ref ** (t) is the adjusted current setpoint; when the operating mode is charging mode, K SOC The expression is: When the operating mode is discharge mode, K SOC The expression is: Wherein, SOC is the square of the ratio of the terminal voltage of the energy storage capacitor to the maximum allowable terminal voltage.

[0115] The expression for SOC is:

[0116]

[0117] Through parameter K SOC For the current given value I ref * (t) is adjusted so that when the SOC of the energy storage capacitor is too low (less than 0.25) or too high (1), the given current value is set to 0, thereby disconnecting the energy storage capacitor from the train's traction power supply network and thus avoiding overcharging or over-discharging of the energy storage capacitor.

[0118] Of course, the above SOC thresholds are just examples. The specific values ​​can be determined based on the performance of the energy storage capacitor itself. For example, 0.25 can be replaced with 0.2, 0.15 or other values, 0.3 can be replaced with 0.4, 0.35 or other values, 0.95 can be replaced with 0.9, 0.85 or other values, and 1 can be replaced with 0.99, 0.98 or other values, etc.

[0119] Specifically, due to the internal resistance of the energy storage capacitor, a temperature rise occurs during its charging and discharging process, thus limiting the operating current. To balance the operating efficiency of the energy storage capacitor with preventing damage from excessive temperature, it needs to operate intermittently. This ensures that the capacitor can meet the high charging and discharging power requirements while maintaining the effective value of the charging and discharging current within the temperature rise limit. Each operating cycle requires determining the corresponding charging and discharging power function P based on the capacitor's own state, such as temperature, charging and discharging current, and terminal voltage. SC_lim (t).

[0120] Optionally, the charge / discharge power function is determined by the following expression:

[0121]

[0122]

[0123]

[0124] T0+ΔT≤T max

[0125] Where t0 is the control cycle of the energy storage capacitor; Δt is the operating cycle of the energy storage capacitor, wherein both the charging and discharging cycles are 0.5Δt; C is the capacitance value of the energy storage capacitor; 0 is the initial time, t∈(0, 0.5Δt); U SC (t) represents the terminal voltage of the energy storage capacitor at time t, and the initial voltage U... SC The value of (t) is U SC0 ;P SC_lim (t) represents the preset charging and discharging power of the energy storage capacitor at time t; R es R is the internal resistance of the energy storage capacitor; ca The typical thermal resistance of the energy storage capacitor is ΔT; ΔT is the temperature rise of the energy storage capacitor within one control cycle t0; T0 is the initial temperature of the energy storage capacitor; T max I represents the highest operating temperature of the energy storage capacitor. RMS This is the effective value of the current in the energy storage capacitor.

[0126] It's important to understand that the initial time can be other than 0, such as t1.

[0127] Furthermore, within the same control period t0, P SC_lim The value of (t) remains unchanged.

[0128] Furthermore, combining the above expressions, we can obtain the charge / discharge power function P. SC_lim (t) should satisfy the following inequality:

[0129]

[0130] Specifically, the preset charging and discharging power of the energy storage capacitor can be the minimum value that satisfies the above inequality, or other suitable values, which can be determined based on the actual situation.

[0131] Specifically, the operating cycle Δt of the energy storage capacitor is the same in both charging and discharging modes. The control cycle t0 should be determined based on the actual circuit conditions.

[0132] For example, taking the train braking state as an example, the energy storage capacitor is operating in charging mode. The energy storage system adopts an intermittent working system, working for 30 seconds (2Δt) every 120 seconds (t0), with each charging and discharging time being 15 seconds (Δt). Therefore, the period t0 of the dynamic power limiting control is set to 120 seconds, that is, the power limit value P of the energy storage system for charging and discharging is updated every 120 seconds. SC_lim At the start of each working cycle, the terminal voltage U of the supercapacitor bank is read. SC0 Given the ambient temperature T0, the limit value P of the charging and discharging power corresponding to this control cycle is then solved using the above formula. SC_lim Finally, the real-time monitored terminal voltage U of the supercapacitor bank is used. SC (t) can be used to calculate the limit value I of the charging and discharging current of the energy storage system at each moment within the control cycle. SC_lim (t), thus achieving dynamic power limiting control. When the ambient temperature is measured to be 20℃, P is calculated. SC_lim The value is 0.56MW, indicating that the supercapacitor is in good condition and can operate at a relatively high power. When the supercapacitor operates frequently for a period of time and the temperature rises to 30℃, P... SC_lim At a power consumption of 0.47MW, when the supercapacitor temperature is high, the power should be appropriately limited to avoid temperature rise issues. Through dynamic power limiting control, the state of the traction power grid and the supercapacitor itself are comprehensively considered during train operation, enabling the supercapacitor energy storage system to maintain a relatively large charging and discharging power under its permissible conditions, ensuring the normal operation of the supercapacitor while maximizing its utilization.

[0133] For example, Figure 4 This application Figure 3 The illustrated embodiment provides a structural schematic diagram of a supercapacitor energy storage system and its control system, as shown below. Figure 4 As shown, the supercapacitor energy storage system 400 includes a traction power supply network 410, a converter 420, and a supercapacitor bank 430. The grid voltage level of the traction power supply network 410 is 1500V. The supercapacitor bank 430 is composed of 48V supercapacitor modules arranged in a 20-series-3-parallel configuration. The typical thermal resistance R of the supercapacitor module is... ca The internal resistance R of the supercapacitor module is 0.4℃ / W.es The supercapacitor has a capacitance of 6mΩ, a capacitance C of 25F, an operating voltage range of 450V~900V (SOC: 0.25~1), an allowable operating temperature of -40℃~65℃, and a rated operating current of 760A. The control system 500 corresponding to this supercapacitor energy storage system mainly consists of three parts: a mode selection section 510, a dual closed-loop control section 520, and a PWM modulation section 530. The mode selection section 510, composed of the aforementioned mode selection module 310, is used to determine the operating mode of the supercapacitor 430 and the given voltage value of the dual closed-loop control section 520 based on the real-time detected grid voltage. The dual closed-loop control section 520 includes a voltage outer loop section 521, a dynamic power limiting control section 522, and a current inner loop section 523. It is used to control the modulation wave of the PWM modulation section 530 based on dynamic power limiting control, thereby controlling the supercapacitor 430 to charge or discharge in the determined operating mode to stabilize the grid voltage. The voltage outer loop section 521, composed of the aforementioned voltage deviation calculation module 321 and voltage PI adjustment module 322, implements closed-loop control of the grid voltage based on the difference between the grid voltage feedback value (grid voltage) and the given voltage value to stabilize the grid voltage. The dynamic power limiting control section... 522 consists of the aforementioned dynamic power limiting control module 330, state-of-charge limiting module 340, and current setpoint adjustment module 350, to achieve power control of the energy storage capacitor based on a preset dynamic power setting, and to obtain the current setpoint of the inner current loop 523. The inner current loop 523 consists of the current closed-loop control module 360, which realizes closed-loop control of the current based on the difference between the current feedback value (charging and discharging current of the supercapacitor 430) and the current setpoint, so as to control the modulation wave of the PWM modulation section 530 (composed of PWM modulation module 370), thereby controlling the control pulse of the converter 420 of the supercapacitor 430, realizing power control of the supercapacitor 430, thereby improving the charging and discharging power of the supercapacitor 430 to meet the operating characteristics of the train, and at the same time improving the voltage regulation performance of the supercapacitor 430.

[0134] In this embodiment, a power control-based system is provided for the energy storage system based on the energy storage capacitor. This system enables dynamic power control of the energy storage capacitor, ensuring that its power characteristics match the power characteristics of the train operation, thereby improving the voltage regulation performance and energy utilization rate of the energy storage system. The dual closed-loop voltage and current control improves control stability and accuracy. By using the energy storage capacitor's own parameters, such as internal resistance, operating temperature, voltage, and current, the preset charging and discharging power of the energy storage capacitor is determined. This ensures the normal operation of the energy storage capacitor while maximizing its utilization, improving its efficiency and safety. Furthermore, the state-of-charge (SOC) limiting module and current setpoint adjustment module flexibly disconnect the energy storage capacitor from the traction power supply network when its charge level is too high or too low, effectively preventing overcharging or over-discharging and extending the capacitor's lifespan.

[0135] Figure 5 This is a flowchart illustrating a control method for an energy storage system according to an embodiment of this application. This control method can be executed by the energy storage system's control system or by a processor. Figure 5 As shown, the control method for the energy storage system provided in this embodiment includes the following steps:

[0136] Step S501: The operating mode and voltage setpoint of the energy storage capacitor of the energy storage system are determined by the mode selection module based on the grid voltage of the traction power supply network.

[0137] Step S502: The voltage deviation between the voltage setpoint and the grid voltage is calculated via the voltage closed-loop control module, and the current control value is determined based on the voltage deviation value.

[0138] Step S503: The current setpoint is determined by the dynamic power limiting control module based on the current limit value or the current control value.

[0139] Wherein, the current limit value is the ratio of the preset charge / discharge power of the energy storage capacitor to the terminal voltage of the energy storage capacitor, the preset charge / discharge power is determined by the charge / discharge power function, and the charge / discharge power function is used to describe the correspondence between the preset charge / discharge power and time.

[0140] Step S504: The current deviation value is determined by the current closed-loop control module based on the current setpoint and the current value of the energy storage capacitor, and the modulation wave is obtained based on the current deviation value.

[0141] Step S505: The converter control pulse is determined by the PWM modulation module based on the modulation wave, so as to control the charging and discharging current of the energy storage capacitor in the operating mode according to the control pulse.

[0142] Optionally, determining the operating mode and voltage setpoint of the energy storage capacitor of the energy storage system based on the grid voltage of the traction power supply network includes:

[0143] When the grid voltage is greater than the charging voltage threshold of the energy storage capacitor but less than the maximum allowable grid voltage, the operating mode of the energy storage capacitor is determined to be the charging mode, and the voltage setpoint is the charging setpoint.

[0144] When the grid voltage is greater than the minimum allowable grid voltage and less than the discharge voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined to be the discharge mode, and the voltage setpoint is the discharge setpoint.

[0145] Optionally, the voltage closed-loop control module includes a voltage deviation calculation module and a voltage PI regulation module. The calculation of the voltage deviation between the voltage setpoint and the grid voltage includes:

[0146] The voltage deviation calculation module calculates the voltage deviation between the voltage setpoint and the grid voltage.

[0147] Determining the current control value based on the voltage deviation value includes:

[0148] The voltage PI regulation module determines the current control value based on the voltage deviation value to achieve closed-loop control of the grid voltage.

[0149] Optionally, determining the current setpoint based on the current limit value or the current control value includes:

[0150] When the current control value is less than the current limit value, the current control value is determined to be the current setpoint value;

[0151] When the current control value is greater than or equal to the current limit value, the current limit value is determined to be the current setpoint value;

[0152] The expression for the current limiting value is: I SC_lim (t)=P SC_lim (t) / U SC (t), P SC_lim (t) represents the preset charging / discharging power at time t, U SC (t) represents the terminal voltage of the energy storage capacitor at time t.

[0153] Optionally, the dynamic power limiting control module further includes a state of charge limiting module, and the control method further includes:

[0154] The current setpoint is set to 0 when the remaining charge of the energy storage capacitor is higher than a first charge threshold or lower than a second charge threshold, via the state of charge limiting module.

[0155] Optionally, after determining the current setpoint based on the current limit value or the current control value, the method further includes:

[0156] Based on the preset given value adjustment formula, the current given value is adjusted according to the remaining charge of the energy storage capacitor to obtain the adjusted current given value;

[0157] Accordingly, determining the current deviation value based on the given current value and the current value of the energy storage capacitor includes:

[0158] The current deviation value is determined based on the adjusted current setpoint and the current value of the energy storage capacitor.

[0159] Optionally, the preset given value adjustment formula is:

[0160] I ref ** (t)=I ref * (t)×K SOC

[0161] Among them, I ref * (t) is the current given value at time t; I ref ** (t) is the adjusted current setpoint; when the operating mode is charging mode, K SOC The expression is: When the operating mode is discharge mode, K SOC The expression is: Wherein, SOC is the square of the ratio of the terminal voltage of the energy storage capacitor to the maximum allowable terminal voltage.

[0162] Optionally, the charge / discharge power function is determined by the following expression:

[0163]

[0164]

[0165]

[0166] T0+ΔT≤T max

[0167] Where t0 is the control cycle of the energy storage capacitor; Δt is the operating cycle of the energy storage capacitor, wherein both the charging and discharging cycles are 0.5Δt; C is the capacitance value of the energy storage capacitor; 0 is the initial time, t∈(0, 0.5Δt); U SC(t) represents the terminal voltage of the energy storage capacitor at time t, and the initial voltage U... SC The value of (t) is U SC0 ;P SC_lim (t) represents the preset charging and discharging power of the energy storage capacitor at time t; R es R is the internal resistance of the energy storage capacitor; ca The typical thermal resistance of the energy storage capacitor is ΔT; ΔT is the temperature rise of the energy storage capacitor within one control cycle t0; T0 is the initial temperature of the energy storage capacitor; T max This is the highest operating temperature of the energy storage capacitor.

[0168] The control method for an energy storage system provided in this application provides a power control strategy for an energy storage system based on an energy storage capacitor. A mode selection module determines the operating mode and given voltage value of the energy storage capacitor. A voltage closed-loop control module implements closed-loop control of the traction network voltage to achieve the desired given voltage value. Simultaneously, the voltage closed-loop control module outputs a current control value. A dynamic power limiting control module obtains the current limit value of the energy storage capacitor based on the ratio of a preset time-varying charging / discharging power to the terminal voltage across the energy storage capacitor. Based on this current limit value and the current control value, a current setpoint is determined. A current closed-loop control is then implemented to achieve closed-loop control of the energy storage capacitor's current, ensuring the current reaches the desired current setpoint. Simultaneously, the control signal output from the current closed-loop control is used to control the rectifier of the energy storage capacitor, thereby controlling the charging and discharging of the energy storage capacitor. The technical solution of this application embodiment realizes dynamic control of the power of the energy storage capacitor, so that the energy storage capacitor can be charged and discharged at appropriate power during the train starting and braking stages, making the power curve of the energy storage capacitor more in line with the electric braking characteristics of the train, and improving the voltage stabilization performance and energy saving effect of the energy storage capacitor.

[0169] Figure 6 This is a schematic diagram of the structure of an energy storage system provided in one embodiment of this application, as shown below. Figure 6 As shown, the energy storage system provided in this embodiment includes: an energy storage capacitor 610 and a control system 620.

[0170] The energy storage capacitor 610 and the control system 620 are electrically connected. The energy storage capacitor 610 may be one or more supercapacitors. The control system 620 is the control system of the energy storage system provided in any embodiment of this application, used to control the charging and discharging power of the energy storage capacitor 610.

[0171] Figure 7 This is a schematic diagram of the structure of an electronic device provided in one embodiment of this application, as shown below. Figure 7 As shown, the electronic device provided in this embodiment includes: a memory 710, a processor 720, and a computer program.

[0172] The computer program is stored in memory 710 and configured to be executed by processor 720 to implement this application. Figure 5 The corresponding embodiment provides a control method for the energy storage system.

[0173] The memory 710 and the processor 720 are connected via a bus 730.

[0174] For relevant instructions, please refer to the corresponding text. Figure 5 The relevant descriptions and effects corresponding to the steps will be understood, and will not be elaborated on here.

[0175] One embodiment of this application provides a computer-readable storage medium having a computer program stored thereon, the computer program being executed by a processor to implement this application. Figure 5 The corresponding embodiment provides a control method for the energy storage system.

[0176] The computer-readable storage medium can be ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0177] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0178] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application filed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not claimed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0179] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A control system for an energy storage system, characterized in that, The energy storage system includes an energy storage capacitor, and the control system includes: a mode selection module, a voltage closed-loop control module, a dynamic power limiting control module, a current closed-loop control module, and a PWM modulation module. The mode selection module is used to determine the operating mode and voltage setpoint of the energy storage capacitor of the energy storage system based on the grid voltage of the traction power supply network. The voltage closed-loop control module is used to calculate the voltage deviation between the voltage setpoint and the grid voltage, and to determine the current control value based on the voltage deviation. The dynamic power limiting control module is used to determine the current setpoint based on the current limit value and the current control value. The current limit value is the ratio of the preset charging / discharging power of the energy storage capacitor to the terminal voltage of the energy storage capacitor. The preset charging / discharging power is determined by a charging / discharging power function, which describes the relationship between the preset charging / discharging power and time. The charging / discharging power function is determined by the following expression: in, The control cycle of the energy storage capacitor; The operating cycle of the energy storage capacitor is defined as follows, wherein both the charging cycle and the discharging cycle are... ; The capacitance value of the energy storage capacitor; At the initial moment, ; for The terminal voltage of the energy storage capacitor at time 1, initially at time 2. The value is ; for The preset charging and discharging power of the energy storage capacitor at any given time; The internal resistance of the energy storage capacitor is denoted as . The typical thermal resistance of the energy storage capacitor is given. For the energy storage capacitor in one control cycle The temperature rise inside; The initial temperature of the energy storage capacitor; This is the highest operating temperature of the energy storage capacitor; This is the effective value of the current in the energy storage capacitor; The current closed-loop control module is used to determine the current deviation value based on the current setpoint and the current value of the energy storage capacitor, and to obtain the modulation wave based on the current deviation value. The PWM modulation module is used to determine the converter control pulse based on the modulation wave, so as to control the charging and discharging current of the energy storage capacitor in the operating mode according to the control pulse.

2. The control system according to claim 1, characterized in that, The dynamic power limiting control module is specifically used for: When the current control value is less than the current limit value, the current control value is determined to be the current setpoint value; When the current control value is greater than or equal to the current limit value, the current limit value is determined to be the current setpoint value; The expression for the current limit value is as follows: , for The preset charge / discharge power at the specified time, for The terminal voltage of the energy storage capacitor at that time.

3. The control system according to claim 2, characterized in that, The control system further includes: The state of charge limiting module is used to set the current setpoint to 0 when the remaining charge of the energy storage capacitor is higher than a first charge threshold or lower than a second charge threshold.

4. The control system according to claim 3, characterized in that, The control system further includes: The current setpoint adjustment module is used to adjust the current setpoint based on the remaining charge of the energy storage capacitor according to a preset setpoint adjustment formula after determining the current setpoint according to the current limit value or the current control value, so as to obtain the adjusted current setpoint. Accordingly, the current closed-loop control module is specifically used for: The current deviation value is determined based on the adjusted current setpoint and the current value of the energy storage capacitor, and the modulation wave is obtained based on the current deviation value.

5. The control system according to claim 4, characterized in that, The preset given value adjustment formula is as follows: in, for The given current value at time; The adjusted current setpoint; when the operating mode is charging mode, The expression is: 1; When the operating mode is discharge mode, The expression is: 0.3, where SOC is the square of the ratio of the terminal voltage of the energy storage capacitor to the maximum allowable terminal voltage.

6. The control system according to claim 1, characterized in that, The mode selection module is specifically used for: When the grid voltage is greater than the charging voltage threshold of the energy storage capacitor but less than the maximum allowable grid voltage, the operating mode of the energy storage capacitor is determined to be the charging mode, and the voltage setpoint is the charging setpoint. When the grid voltage is greater than the minimum allowable grid voltage and less than the discharge voltage threshold of the energy storage capacitor, the operating mode of the energy storage capacitor is determined to be the discharge mode, and the voltage setpoint is the discharge setpoint.

7. The control system according to claim 1, characterized in that, The voltage closed-loop control module includes a voltage deviation calculation module and a voltage PI adjustment module; The voltage deviation calculation module is used to calculate the voltage deviation between the voltage setpoint and the grid voltage. The voltage PI regulation module is used to determine the current control value based on the voltage deviation value, so as to realize closed-loop control of the grid voltage.

8. A control method for an energy storage system, characterized in that, The energy storage system includes an energy storage capacitor, and the method includes: The operating mode and voltage setpoint of the energy storage capacitor of the energy storage system are determined by the mode selection module based on the grid voltage of the traction power supply network. The voltage deviation between the voltage setpoint and the grid voltage is calculated via the voltage closed-loop control module, and the current control value is determined based on the voltage deviation. The dynamic power limiting control module determines the current setpoint based on the current limit value or the current control value. The current limit value is the ratio of the preset charge / discharge power of the energy storage capacitor to the terminal voltage of the energy storage capacitor. The preset charge / discharge power is determined by a charge / discharge power function, which describes the relationship between the preset charge / discharge power and time. The charge / discharge power function is determined by the following expression: in, The control cycle of the energy storage capacitor; The operating cycle of the energy storage capacitor is defined as follows, wherein both the charging cycle and the discharging cycle are... ; The capacitance value of the energy storage capacitor; At the initial moment, ; for The terminal voltage of the energy storage capacitor at time 1, initially at time 2. The value is ; for The preset charging and discharging power of the energy storage capacitor at any given time; The internal resistance of the energy storage capacitor is denoted as . The typical thermal resistance of the energy storage capacitor is given. For the energy storage capacitor in one control cycle The temperature rise inside; The initial temperature of the energy storage capacitor; This is the highest operating temperature of the energy storage capacitor; This is the effective value of the current in the energy storage capacitor; The current deviation value is determined based on the current setpoint and the current value of the energy storage capacitor via the current closed-loop control module, and the modulation wave is obtained based on the current deviation value. The converter control pulse is determined based on the modulation wave via the PWM modulation module, so as to control the charging and discharging current of the energy storage capacitor in the operating mode according to the control pulse.

9. An energy storage system, characterized in that, It includes an energy storage capacitor and a control system as described in any one of claims 1-7.

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