A high-voltage direct-hanging type network-forming energy storage grid-connected control method and system

Abstract

The application discloses a high-voltage direct-hanging type network-constructed energy storage grid-connected control method and system, and mainly relates to the technical field of high-voltage direct-hanging type energy storage. The method comprises the following steps: sampling and calculating the output active power and reactive power of a high-voltage direct-hanging type energy storage system, and obtaining an internal voltage phase reference value and an internal voltage amplitude reference value; calculating an equivalent internal voltage and a virtual impedance voltage, and obtaining a current first reference value; obtaining a current given value according to the current first reference value and a current amplitude limiting value, obtaining a modulation voltage reference value, and driving an H-bridge in each module of the high-voltage direct-hanging type energy storage system to generate a voltage based on the reference value. The application has the beneficial effect that the stability of new energy power generation and the regulation capacity of the power grid are improved through the network-constructed control strategy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-voltage direct-hanging energy storage, in particular to a high-voltage direct-hanging grid-forming energy storage grid-connected control method and system. BACKGROUND

[0002] With the increasing proportion of new energy power generation in the power system, large-capacity energy storage systems are widely used to solve the volatility and intermittency of new energy power generation. In order to improve the single-machine capacity and voltage level of the energy storage system, researchers have proposed a high-voltage direct-hanging converter based on cascaded H-bridge topology. Due to its advantages such as large capacity, high efficiency, redundancy and scalability, it has become the preferred solution for large-capacity energy storage systems. Grid-forming control runs the converter as a voltage source, enabling it to actively support the grid frequency and voltage like a synchronous generator, and has become a key technology to solve the stability problem of the power system.

[0003] The grid-forming control scheme of the high-voltage direct-hanging converter in the prior art has some deficiencies, mainly in the following aspects:

[0004] 1. Uncontrollable DC voltage: Although the grid-forming control technology based on the virtual synchronous generator (VSG) control strategy can enhance system stability, one of its shortcomings is that the DC voltage is uncontrollable, which may cause large voltage fluctuations on the DC side under certain conditions, affecting the overall stability of the system.

[0005] 2. Dynamic response speed: The existing grid-forming control method may not be fast enough in some cases, especially when dealing with grid faults or load surges, it may not be able to adjust the output power and voltage in time, affecting the stability of the system.

[0006] 3. Control complexity: Grid-forming control technology involves multiple control loops and parameter adjustments, making its control algorithm complex and difficult to implement. At the same time, the complex control logic also increases the maintenance and debugging cost of the system.

[0007] 4. Limited application scenarios: Although grid-forming control technology has a wide range of applications, it may not be able to fully utilize its advantages in all application scenarios. For example, under certain specific grid structures and operating conditions, grid-forming control technology may not achieve the desired results.

[0008] 5. Hardware dependency: The implementation of grid-forming control technology often relies on high-performance hardware devices such as high-speed processors and high-precision sensors, which increases the cost and complexity of the system and also puts higher requirements on the reliability of the hardware.

[0009] Therefore, a high-voltage direct-hanging network-type energy storage grid-connected control method and system are urgently needed to solve the above problems. SUMMARY

[0010] The application aims to provide a high-voltage direct-hanging network-type energy storage grid-connected control method and system, which realizes the stability of new energy power generation and the regulation ability of the power grid through the network-type control strategy.

[0011] To achieve the above-mentioned purpose, the application realizes the following technical solutions:

[0012] On the one hand, a high-voltage direct-hanging network-type energy storage grid-connected control method is provided, comprising the following steps:

[0013] S1: Sampling and calculating the output active power and reactive power of the high-voltage direct-hanging energy storage system; through the calculation of the active power control law and the reactive power control law, the inner voltage phase reference value and the inner voltage amplitude reference value are obtained respectively;

[0014] S2: According to the modulation voltage reference value of the last control cycle, the equivalent inner voltage is calculated; the virtual impedance voltage is calculated; the inner voltage amplitude reference value and 0 are taken as the given values of the inner voltage d-axis and q-axis respectively; the equivalent inner voltage is taken as the voltage feedback, and the equivalent inner voltage is adjusted through the proportional integral controller to obtain the first current reference value;

[0015] S3: According to the first current reference value and the current amplitude limit value, the second current reference value of the d-axis and q-axis is calculated as the current given value; the output current is taken as the current feedback, and the output current is adjusted through the proportional integral controller to obtain the modulation voltage reference value; the three-phase modulation voltage reference value is obtained through coordinate transformation using the inner voltage phase reference value, and the H-bridge in each module of the high-voltage direct-hanging energy storage system is driven to generate voltage based on the reference value.

[0016] Preferably, in step S1, the output active power and reactive power of the high-voltage direct-hanging energy storage system are sampled and calculated, specifically:

[0017] The three-phase voltage and three-phase output current of the high-voltage direct-hanging energy storage system are collected, the three-phase voltage is denoted as U a , U b , U c , and the three-phase output current is denoted as I a , I b , I c ;

[0018] According to the collected three-phase voltage and three-phase output current, the active power P and reactive power Q output by the high-voltage direct-hanging energy storage system are calculated respectively;

[0019] In the dq rotating coordinate system, the active power and the reactive power can be calculated by the following formulas:

[0020] P = U d · I d + U q · I q

[0021] Q = U d · I d - U q · I q

[0022] Wherein, U d and U q are the d-axis and q-axis components of the grid-connected point voltage, I d and I q are the d-axis and q-axis components of the output current.

[0023] Preferably, in the step S1, the inner voltage phase reference value and the inner voltage amplitude reference value are obtained respectively, specifically as follows:

[0024] Given the active power reference value of the high-voltage direct-hanging type energy storage system, combined with the output active power of the high-voltage direct-hanging type energy storage system and the rated angular frequency of the power grid, the inner voltage phase reference value is calculated by the active power control law, and the calculation formula is as follows:

[0025] Δθ = K p (P ref - P) + K i ∫(P ref - P)dt

[0026] Wherein, Δθ is the change amount of the inner voltage phase reference value, K p and K i are the proportional and integral control coefficients, P ref is the active power reference value of the high-voltage direct-hanging type energy storage system, and P is the actual output active power of the high-voltage direct-hanging type energy storage system.

[0027] Given the reactive power reference value of the high-voltage direct-hanging type energy storage system, combined with the output reactive power of the high-voltage direct-hanging type energy storage system, the reactive power reference value and the rated output voltage amplitude, the inner voltage amplitude reference value is calculated by the reactive power control law, and the calculation formula is as follows:

[0028] ΔU = K q (Q ref - Q) + K i ∫(Q ref - Q)dt

[0029] Wherein, ΔU is the change amount of the inner voltage amplitude reference value, K q and Ki These are the proportional and integral control coefficients, Q. ref Q is the reference value for reactive power of the high-voltage direct-connected combined energy storage system, and Q is the actual reactive power output of the high-voltage direct-connected combined energy storage system.

[0030] Preferably, in step S2, calculating the equivalent internal voltage specifically involves:

[0031] The modulation voltage reference values ​​of the d-axis and q-axis from the previous control cycle are extracted from the controller module of the high-voltage direct-connected energy storage system, and are denoted as follows: The equivalent internal voltages of the d-axis and q-axis are calculated based on the extracted modulation voltage reference value, and are denoted as e, respectively. d e q The calculation formula is as follows:

[0032]

[0033] Among them, K mod It represents the modulation equivalent gain, which is a constant or a coefficient that varies according to the characteristics of the high-voltage direct-connected energy storage system.

[0034] Preferably, in step S2, obtaining the first reference value of the current specifically involves:

[0035] Set the virtual resistance and virtual inductance of the high-voltage direct-connected energy storage system, and calculate the virtual impedance voltage on the d-axis and q-axis based on the set virtual resistance and virtual inductance and the output current;

[0036] The equivalent internal voltage is regulated in a closed loop using a proportional-integral controller.

[0037] The first reference value of the current is calculated based on the adjusted equivalent internal voltage.

[0038] Preferably, in step S3, calculating the second reference values ​​of the current along the d-axis and q-axis specifically involves:

[0039] The first reference values ​​of the current on the d-axis and q-axis obtained in step S2 are denoted as i, respectively. d，ref1 i q，ref1 ;

[0040] Set the current limit value for the high-voltage direct-connected combined energy storage system. Calculate the second reference values ​​for the current on the d-axis and q-axis based on the first current reference value and the current limit value. The calculation formula is as follows:

[0041] i d，ref2 =min(|i d，ref1 |,I lim )×sign(i d，ref1 )

[0042] i q，ref2= min (|i q，ref1 |, I lim ) x sign(i q，ref1 )

[0043] wherein i d，ref2 and i q，ref2 represent the second reference value of the current on the d-axis and q-axis respectively, I lim represents the current limiting value, the min() function is used to take the smaller value, and the sign() function is used to retain the sign of the current.

[0044] Preferably, in the step S3, the three-phase modulation voltage reference value is obtained, specifically:

[0045] The sector in which the reference voltage is located is determined according to the U α and U β obtained by the Park inverse transformation;

[0046] The boundary vectors of the synthesized reference voltage are selected according to the sector;

[0047] The time during which the two boundary vectors act, respectively, is calculated according to the amplitude of the reference voltage;

[0048] The action time of the two boundary vectors is judged and processed by modulation;

[0049] The time for seven-segment vector synthesis is calculated and distributed;

[0050] The voltage reference values on the d-axis and q-axis are converted to the three-phase abc-axis.

[0051] Preferably, in the step S3, the H-bridge of each module in the high-voltage direct-hanging cascaded energy storage system generates voltage, specifically: based on the generated three-phase modulation voltage reference value, the H-bridge of each module in the high-voltage direct-hanging cascaded energy storage system is driven to generate corresponding voltage through the SPWM modulation strategy.

[0052] On the other hand, a high-voltage direct-hanging network-type energy storage grid-connected control system is provided for implementing any of the above-mentioned high-voltage direct-hanging network-type energy storage grid-connected control methods.

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] 1. The network-type energy storage system has a voltage source external characteristic through specific control technology, can actively support the grid frequency and voltage, and thus effectively deals with the volatility and intermittency of new energy generation and improves the stability of the grid;

[0055] 2. The high-voltage direct-hanging network-type energy storage system can quickly output active / reactive power, realize flexible adjustment of the grid frequency and voltage, and meet the adjustment requirements of the grid under different operating conditions;

[0056] 3. Compared with the traditional low-voltage boosting technology, the high-voltage direct hanging type energy storage system does not need to pass through the transformer link and is directly connected to the power grid, thereby reducing the loss in the energy conversion process and improving the overall efficiency of the system;

[0057] 4. Improving the battery life: the high-voltage direct hanging type energy storage system reduces the parallel operation of the battery cluster through the cascade structure, avoids the circulating current phenomenon between the battery monomers and the battery cluster, thereby weakening the problems caused by the consistency of the battery in the energy storage system, and improving the cycle life of the battery system;

[0058] 5. The control of the high-voltage direct hanging type energy storage system is relatively simple, and each three-phase is a group of control units, which does not need to coordinate and respond to the instruction according to the performance difference of the parallel energy storage units, thereby shortening the response time of the energy storage system;

[0059] 6. The high-voltage direct hanging type network construction energy storage system is suitable for occasions with high requirements for energy storage control performance, such as inertia support, stability control, fast frequency and voltage regulation, etc., such as new energy power station energy storage, independent energy storage, etc. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is the overall method flowchart of the present application;

[0061] Figure 2 is the method flowchart for calculating the output active power and reactive power of the high-voltage direct hanging type energy storage system of the present application;

[0062] Figure 3 is the method flowchart for calculating the internal voltage phase reference value and the internal voltage amplitude reference value of the present application;

[0063] Figure 4 is the method flowchart for calculating the current first reference value of the present application;

[0064] Figure 5 is the method flowchart for calculating the three-phase modulation voltage reference value of the present application. DETAILED DESCRIPTION

[0065] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the present application.

[0066] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0067] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0068] Example:

[0069] like Figure 1 As shown, this embodiment provides a high-voltage direct-connection grid-connected energy storage grid-connected control method, including the following steps;

[0070] S1: Sample and calculate the output active and reactive power of the high-voltage direct-connected energy storage system; obtain the internal voltage phase reference value and internal voltage amplitude reference value through the calculation of the active power control law and the reactive power control law, respectively.

[0071] S2: Calculate the equivalent internal voltage based on the modulation voltage reference value of the previous control cycle; calculate the virtual impedance voltage; use the internal voltage amplitude reference value and 0 as the given values ​​for the d-axis and q-axis of the internal voltage, respectively; use the equivalent internal voltage as voltage feedback, adjust the equivalent internal voltage through the proportional-integral controller, and obtain the first reference value of the current.

[0072] S3: Calculate the second reference values ​​of the current on the d-axis and q-axis based on the first reference value of the current and the current limit value, and use them as the current setpoint; use the output current as current feedback, adjust the output current through the proportional-integral controller to obtain the modulation voltage reference value; use the internal voltage phase reference value to perform coordinate transformation to obtain the three-phase modulation voltage reference value, and drive the H-bridge of each module in the high-voltage direct-connected energy storage system to generate voltage based on the reference value.

[0073] In step S1, as follows Figure 2 As shown, the output active and reactive power of the high-voltage direct-connected combined energy storage system are sampled and calculated, specifically as follows:

[0074] The three-phase voltage and three-phase output current at the grid connection point of the high-voltage direct-connected energy storage system are collected. The three-phase voltage is denoted as U. a U b U c The three-phase output current is denoted as I.a 、I b 、I c ;

[0075] According to the collected three-phase voltage and three-phase output current, the active power P and the reactive power Q output by the high-voltage direct-hanging energy storage system are calculated respectively;

[0076] In the dq rotating coordinate system, the active power and the reactive power can be calculated by the following formula:

[0077] P=U d ·I d +U q ·I q

[0078] Q=U d ·I d -U q ·I q

[0079] Wherein, U d and U q are the d-axis and q-axis components of the grid-connected point voltage, I d and I q are the d-axis and q-axis components of the output current;

[0080] As Figure 3 shown, the inner voltage phase reference value and the inner voltage amplitude reference value are obtained respectively, specifically:

[0081] Given the active power reference value of the high-voltage direct-hanging energy storage system, combined with the active power output by the high-voltage direct-hanging energy storage system and the rated angular frequency of the power grid, the inner voltage phase reference value is calculated by the active power control law, and the calculation formula is as follows:

[0082] Δθ=K p (P ref -P)+K i ∫(P ref -P)dt

[0083] Wherein, Δθ is the change amount of the inner voltage phase reference value, K p and K i are the proportional and integral control coefficients, P ref is the active power reference value of the high-voltage direct-hanging energy storage system, and P is the active power actually output by the high-voltage direct-hanging energy storage system;

[0084] Given the reactive power reference value of the high-voltage direct-hanging energy storage system, combined with the reactive power output by the high-voltage direct-hanging energy storage system, the reactive power reference value and the rated output voltage amplitude, the inner voltage amplitude reference value is calculated by the reactive power control law, and the calculation formula is as follows:

[0085] ΔU = K q (Q ref -Q) + K i ∫(Q ref -Q)dt

[0086] wherein, ΔU is the change of the amplitude reference value of internal voltage, K q and K i are the proportional and integral control coefficients respectively, Q ref is the reactive power reference value of the high-voltage direct-coupled energy storage system, and Q is the actual output reactive power of the high-voltage direct-coupled energy storage system.

[0087] In the step S2, the equivalent internal voltage is calculated, specifically:

[0088] The modulation voltage reference value of the d-axis and the q-axis in the last control period is extracted from the high-voltage direct-coupled energy storage system controller module, and is denoted as The equivalent internal voltage of the d-axis and the q-axis is calculated according to the extracted modulation voltage reference value, and is denoted as e d , e q , and the calculation formula is as follows:

[0089]

[0090] wherein, K mod represents the modulation equivalent gain, which is a constant or a coefficient that changes according to the characteristics of the high-voltage direct-coupled energy storage system;

[0091] In the step S2, the virtual impedance voltage is calculated, including:

[0092] The virtual resistance and the virtual inductance are pre-set according to the characteristics and control requirements of the high-voltage direct-coupled energy storage system, and are denoted as R v , L v ;

[0093] The current output i abc of the high-voltage direct-coupled energy storage system is collected, and the output current i abc is a three-phase output current;

[0094] The three-phase current i abc is converted from the abc coordinate system to the dq rotating coordinate system using Park transformation, and i dq is obtained;

[0095] In the dq coordinate system, the virtual impedance voltage of the d-axis and the q-axis can be calculated according to the definition of the virtual impedance. For the d-axis, the calculation formula of the virtual impedance voltage u vd is as follows:

[0096]

[0097] wherein, is the rate of change of the d-axis current;

[0098] For the q-axis, the virtual impedance voltage u vq is calculated as:

[0099]

[0100] wherein, is the rate of change of the q-axis current;

[0101] In step S2, the inner voltage amplitude reference value and 0 are taken as the given values of the inner voltage d-axis and q-axis respectively, specifically:

[0102] When the inner voltage amplitude reference value is set as the given value of the d-axis, the high-voltage direct-hanging energy storage system will try to control the actual d-axis voltage to approach this reference value; the given value of the q-axis is set to 0, which means that the high-voltage direct-hanging energy storage system hopes that the q-axis voltage remains at 0 or close to 0, which is usually related to the control of reactive power. In order to achieve a specific control goal, different controls are needed for the d-axis and q-axis voltages;

[0103] As shown in Figure 4 , in the step S2, the current first reference value is obtained, specifically:

[0104] The virtual resistance and virtual inductance of the high-voltage direct-hanging energy storage system are set, and the virtual impedance voltages of the d-axis and q-axis are calculated according to the set virtual resistance and virtual inductance and the output current;

[0105] Through the proportional-integral controller, the equivalent inner voltage is closed-loop adjusted to obtain a more stable and accurate control effect;

[0106] Based on the adjusted equivalent inner voltage, the first reference value of the current is calculated.

[0107] In the step S3, the second reference value of the current on the d-axis and q-axis is calculated, specifically:

[0108] The current first reference values on the d-axis and q-axis obtained in step S2 are denoted as i d，ref1 and i q，ref1 respectively;

[0109] The current limit value of the high-voltage direct-hanging energy storage system is set, and the second reference value of the current on the d-axis and q-axis is calculated according to the current first reference value and the current limit value, and the calculation formula is as follows:

[0110] i d，ref2 = min(|i d，ref1 |, I lim ) x sign(i d，ref1 )

[0111] i q，ref2 =min(|i q，ref1 |,I lim )×sign(i q，ref1 )

[0112] Among them, i d，ref2 and i q，ref2 I represents the second reference value of the current along the d-axis and q-axis, respectively. lim This represents the current limit value. The min() function is used to take the smaller value, and the sign() function is used to retain the sign of the current.

[0113] In step S3, the output current is used as current feedback, and the output current is adjusted by a proportional-integral controller to obtain the modulation voltage reference value. The specific implementation process is as follows:

[0114] The actual output current i of the inverter is monitored and collected in real time by sensors. actual ;

[0115] The actual current is compared with the set reference current, and the current error e(t) is calculated:

[0116] e(t) = i ref -i actual

[0117] The transfer function of a PI controller can be expressed as:

[0118]

[0119] Among them, K p It is the proportional gain, K i It is the integral gain, and s is the complex frequency domain variable;

[0120] Input the current error e(t) into the PI controller and calculate the PI controller output u(t). For a discrete-time system, the PI controller output can be calculated using the following recursive formula:

[0121] u(t) = K p ·e(t)+K i ·∫e(t)dt

[0122] The output u(t) of the PI controller is used as the reference value of the modulation voltage.

[0123] like Figure 5 As shown, the reference values ​​for the three-phase modulation voltage are obtained, specifically:

[0124] U obtained from the inverse Park transform α U βDetermine the sector where the reference voltage is located, in the SVPWM (Space Vector Pulse Width Modulation) algorithm, usually according to the value of U α , U β to determine which sector the reference voltage vector is located in;

[0125] According to the sector, select the boundary vectors of the synthesized reference voltage, which are two non-zero vectors and one zero vector adjacent to the reference voltage vector;

[0126] According to the amplitude of the reference voltage, calculate the time of action of the two boundary vectors, and in a carrier cycle, the product of the action time of the reference voltage vector and each boundary vector is equal to the product of the carrier cycle and the reference voltage vector;

[0127] The action time of the two boundary vectors is modulated and processed, and if the calculated action time exceeds the allowed range, corresponding adjustment is needed to avoid overmodulation phenomenon;

[0128] Calculate and distribute the time of seven-segment vector synthesis, which includes determining the specific action time of each vector (including zero vector and non-zero vector) in a carrier cycle;

[0129] Convert the voltage reference values on the d-axis and q-axis to the three-phase abc-axis, and use Park inverse transformation to convert the voltage components on the dq-axis back to the voltage components in the abc three-phase coordinate system;

[0130] Drive the H-bridge of each module in the high-voltage direct-hanging type cascaded energy storage system to generate voltage, specifically: based on the generated three-phase modulation voltage reference value, drive the H-bridge of each module in the high-voltage direct-hanging type cascaded energy storage system to generate corresponding voltage through SPWM modulation strategy.

[0131] In addition, the embodiment also provides a high-voltage direct-hanging type network construction energy storage grid-connected control system for realizing any one of the high-voltage direct-hanging type network construction energy storage grid-connected control methods.

[0132] The above is a specific description of the preferred embodiment of the present application, but the present application is not limited to the described embodiments, and those skilled in the art can make various equivalent modifications or replacements without deviating from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A grid-connected control method for a high-voltage direct-coupled grid-forming energy storage, characterized in that, The method comprises the following steps: S1: sampling and calculating the output active power and reactive power of the high-voltage direct-cascaded energy storage system; through the calculation of the active power control law and the reactive power control law, the inner voltage phase reference value and the inner voltage amplitude reference value are obtained respectively; S2: calculating the equivalent inner voltage according to the modulation voltage reference value of the last control period; calculating the virtual impedance voltage; taking the inner voltage amplitude reference value and 0 as the given values of the inner voltage d-axis and q-axis respectively; taking the equivalent inner voltage as the voltage feedback, adjusting the equivalent inner voltage through the proportional integral controller to obtain the current first reference value; S3: calculating the current second reference value of the d-axis and q-axis according to the current first reference value and the current amplitude limit value, as the current given value; taking the output current as the current feedback, adjusting the output current through the proportional integral controller to obtain the modulation voltage reference value; The three-phase modulation voltage reference value is obtained through coordinate transformation by using the inner voltage phase reference value, and the H-bridge of each module in the high-voltage direct-cascaded energy storage system is driven to generate voltage based on the three-phase modulation voltage reference value; In the step S3, the current second reference value of the d-axis and q-axis is calculated, comprising: The first reference values of the currents on the d-axis and q-axis obtained in step S2 are respectively denoted as ; The current amplitude limit value of the high-voltage direct-cascaded energy storage system is set, and the current second reference value of the d-axis and q-axis is calculated according to the current first reference value and the current amplitude limit value, and the calculation formula is: wherein, and respectively denote a second reference value of the current on the d-axis and on the q-axis, denotes a current clipping value, the function min is used to take the smaller value, the function sign is used to preserve the sign of the current; In the step S3, the three-phase modulation voltage reference value is obtained, comprising: According to the Park inverse transform, we get determining the sector in which the reference voltage lies; According to the sector, the boundary vectors of the synthesized reference voltage are selected; According to the amplitude of the reference voltage, the time of the action of the two boundary vectors is calculated; The action time of the two boundary vectors is judged and processed; The time of the seven-segment vector synthesis is calculated and distributed; The voltage reference value on the d-axis and q-axis is converted to the three-phase abc-axis; In the step S3, the H-bridge of each module in the high-voltage direct-cascaded energy storage system is driven to generate voltage, comprising: based on the generated three-phase modulation voltage reference value, the H-bridge of each module in the high-voltage direct-cascaded energy storage system is driven to generate corresponding voltage through the SPWM modulation strategy.

2. The high-voltage direct-hanging network-type energy storage grid-connected control method according to claim 1, characterized in that, In the step S1, the output active power and reactive power of the high-voltage direct-cascaded energy storage system are sampled and calculated, comprising: Three-phase voltage and three-phase output current of a high-voltage direct-connection energy storage system grid-connected point are collected, the three-phase voltage is denoted as , and the three-phase output current is denoted as ; According to the collected three-phase voltage and three-phase output current, active power and reactive power output by the high-voltage direct-hanging energy storage system are calculated respectively and ​ In the dq rotating coordinate system, the active power and the reactive power can be calculated through the following formula: wherein, and are the d-axis and q-axis components of the grid-connected point voltage, respectively, and are the d-axis and q-axis components of the output current, respectively.

3. The high-voltage direct-hanging network-type energy storage grid-connected control method according to claim 2, characterized in that, In the step S1, the inner voltage phase reference value and the inner voltage amplitude reference value are obtained respectively, comprising: The active power reference value of the high-voltage direct-cascaded energy storage system is given, and the inner voltage phase reference value is calculated through the active power control law combined with the output active power of the high-voltage direct-cascaded energy storage system and the rated angular frequency of the power grid, and the calculation formula is as follows: wherein, is a variation of the inner voltage phase reference value, and are proportional and integral control coefficients, respectively, is an active power reference value of the high-voltage direct-coupled energy storage system, is an active power actually output by the high-voltage direct-coupled energy storage system; The reactive power reference value of the high-voltage direct-cascaded energy storage system is given, and the inner voltage amplitude reference value is calculated through the reactive power control law combined with the output reactive power of the high-voltage direct-cascaded energy storage system, the reactive power reference value and the rated output voltage amplitude, and the calculation formula is as follows: wherein, is a variation of the inner voltage amplitude reference value, and are proportional and integral control coefficients, respectively, is a reactive power reference value of the high-voltage direct-coupled energy storage system, is the actual output reactive power of the high-voltage direct-coupled energy storage system.

4. The high-voltage direct-hanging network-type energy storage grid-connected control method according to claim 3, characterized in that, In the step S2, the equivalent inner voltage is calculated, comprising: Extract the modulation voltage reference value of d-axis and q-axis of the last control period from the high-voltage direct-coupled energy storage system controller module, respectively denoted as According to the extracted modulation voltage reference value, the equivalent internal voltage of d-axis and q-axis is calculated, respectively denoted as The calculation formula is as follows: wherein, Gmrepresents the modulation equivalent gain, which is a constant or a coefficient that varies according to the characteristics of the high-voltage direct-connection storage energy system.

5. The high-voltage direct-hanging network-type energy storage grid-connected control method according to claim 4, characterized in that, In the step S2, the current first reference value is obtained, comprising: The virtual resistance and the virtual inductance of the high-voltage direct-cascaded energy storage system are set, and the virtual impedance voltage of the d-axis and q-axis is calculated according to the set virtual resistance and virtual inductance and the output current; The equivalent internal voltage is closed-loop regulated by a proportional-integral controller; A first reference value of the current is calculated based on the adjusted equivalent internal voltage.

6. A high-voltage direct-coupled grid-forming energy storage grid- connected control system, characterized in that, The application discloses a high-voltage direct-hanging network type energy storage grid-connected control method.

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