High-voltage direct-hanging type network-constructing type energy storage grid-connected control method and system

Abstract

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

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage direct-mounted energy storage, and in particular to a high-voltage direct-mounted grid-connected energy storage grid-connected control method and system. Background Art

[0002] As the proportion of renewable energy generation in the power system gradually increases, large-capacity energy storage systems are widely used to solve the volatility and intermittency problems of renewable energy generation. In order to improve the single-machine capacity and voltage level of the energy storage system, researchers have proposed a high-voltage direct-mounted converter based on the 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 operates the converter as a voltage source, enabling it to have the ability to actively support the grid frequency and voltage similar to a synchronous generator, becoming a key technology for solving the stability problem of the power system.

[0003] The existing grid-type control scheme of high-voltage direct-mounted converters has some shortcomings, which are mainly reflected in the following aspects:

[0004] 1. Uncontrollable DC voltage: Although the grid-based control technology with the virtual synchronous generator (VSG) control strategy as the main architecture can enhance system stability, one of its disadvantages is that the DC voltage is uncontrollable, which may lead to large voltage fluctuations on the DC side under certain circumstances, affecting the overall stability of the system;

[0005] 2. Dynamic response speed: The existing grid-based control methods may not have a fast enough dynamic response speed in some cases. Especially when dealing with grid failures or load mutations, the output power and voltage may not be adjusted in time, thus affecting the stability of the system.

[0006] 3. Control complexity: Network control technology involves multiple control links and parameter adjustments, which makes its control algorithm more complex and difficult to implement. At the same time, complex control logic also increases the maintenance and debugging costs of the system;

[0007] 4. Limited applicable scenarios: Although the grid-building control technology has a wide range of applicable scenarios, not all application scenarios can fully exert its advantages. For example, under some specific power grid structures and operating conditions, the grid-building control technology may not achieve the expected results.

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

[0009] Therefore, there is an urgent need for a high-voltage direct-mounted grid-connected energy storage control method and system to solve the above problems. Summary of the invention

[0010] The purpose of the present invention is to provide a high-voltage direct-mounted grid-connected energy storage grid-connected control method and system, which realizes the improvement of the stability of renewable energy power generation and the regulation capacity of the power grid through a grid-connected control strategy.

[0011] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0012] On the one hand, a high-voltage direct-mounted grid-connected energy storage 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-mounted energy storage system; obtaining the internal voltage phase reference value and the internal voltage amplitude reference value respectively through calculation of the active power control law and the reactive power control law;

[0014] S2: Calculate the equivalent internal voltage according to 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 ​​of the internal voltage d-axis and q-axis 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;

[0015] S3: Calculate the second reference value of the current of the d-axis and the q-axis according to the first reference value of the current and the current limit value as the current given value; use the output current as the current feedback, adjust the output current through the proportional integral controller, and 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-mounted energy storage system 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-mounted energy storage system are sampled and calculated, specifically:

[0017] Collect the three-phase voltage and three-phase output current of the high-voltage direct-mounted energy storage system grid connection point, and the three-phase voltage is recorded as U a , U b , U c , the three-phase output current is recorded 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-mounted energy storage system are calculated respectively;

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

[0020] P=U d I d +U q I q

[0021] Q=U d I d -U q I q

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

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

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

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

[0026] Among them, Δθ is the change of the internal voltage phase reference value, K p and K i are proportional and integral control coefficients, P ref is the active power reference value of the high-voltage direct-mounted energy storage system, and P is the active power actually output by the high-voltage direct-mounted energy storage system;

[0027] Given the reactive power reference value of the high-voltage direct-mounted energy storage system, combined with the output reactive power of the high-voltage direct-mounted energy storage system, the reactive power reference value and the rated output voltage amplitude, the internal voltage amplitude reference value is calculated through the reactive power control law. The calculation formula is as follows:

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

[0029] Among them, ΔU is the change of the internal voltage amplitude reference value, K q and Ki are the proportional and integral control coefficients, Q ref is the reactive power reference value of the high-voltage direct-mounted energy storage system, and Q is the reactive power actually output by the high-voltage direct-mounted energy storage system.

[0030] Preferably, in step S2, the equivalent internal voltage is calculated as follows:

[0031] The modulation voltage reference values ​​of the d-axis and q-axis of the previous control cycle are extracted from the high-voltage direct-mounted energy storage system controller module and recorded as The equivalent internal voltages of the d-axis and q-axis are calculated based on the extracted modulation voltage reference values, which are denoted as e 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 changes according to the characteristics of the high-voltage direct-mounted energy storage system.

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

[0035] Setting the virtual resistance and virtual inductance of the high-voltage direct-mounted energy storage system, and calculating the virtual impedance voltages of the d-axis and the q-axis according to the set virtual resistance and virtual inductance and the output current;

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

[0037] Based on the adjusted equivalent internal voltage, a first reference value of the current is calculated.

[0038] Preferably, in step S3, the second reference values ​​of the currents of the d-axis and the q-axis are calculated, specifically:

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

[0040] The current limit value of the high-voltage direct-mounted energy storage system is set, and the second reference value of the current of the d-axis and the q-axis is calculated according to the first reference value of the current 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 )×sign(i q，ref1 )

[0043] Among them, i d，ref2 and i q，ref2 Represent the second reference value of the current of the d-axis and q-axis, I lim Indicates the current limit value, the min() function is used to take a smaller value, and the sign() function is used to retain the sign of the current.

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

[0045] According to the Park inverse transform, U α , U β Determine the sector where the reference voltage is located;

[0046] Selecting a boundary vector of a synthetic reference voltage according to the sector;

[0047] Calculate the time when two boundary vectors act respectively according to the amplitude of the reference voltage;

[0048] Conduct overmodulation judgment and processing on the action time of two boundary vectors;

[0049] Calculate and allocate the time for seven-segment vector synthesis;

[0050] Convert the voltage reference values ​​on the d-axis and q-axis to the three-phase abc-axis.

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

[0052] On the other hand, a high-voltage direct-mounted grid-connected energy storage grid-connected control system is provided, which is used to implement any of the above-mentioned high-voltage direct-mounted grid-connected energy storage grid-connected control methods.

[0053] Compared with the prior art, the beneficial effects of the present invention are:

[0054] 1. The grid-type energy storage system uses specific control technology to enable the converter to have voltage source external characteristics, which can actively support the grid frequency and voltage, thereby effectively coping with the volatility and intermittency of renewable energy power generation and improving the stability of the grid;

[0055] 2. The high-voltage direct-mounted grid-connected energy storage system can quickly output active / reactive power, realize flexible adjustment of grid frequency and voltage, and meet the grid's regulation needs under different working conditions;

[0056] 3. Compared with traditional low-voltage boost technology, the high-voltage direct-mounted energy storage system does not need to go through the transformer link and is directly connected to the power grid, which reduces the loss in the energy conversion process and improves the overall efficiency of the system;

[0057] 4. Improve battery life: The high-voltage direct-mounted energy storage system reduces the parallel operation of battery clusters through a cascade structure, avoiding the circulation phenomenon between battery cells and battery clusters, thereby weakening the problems caused by battery consistency in the energy storage system and improving the cycle life of the battery system;

[0058] 5. The control of high-voltage direct-mounted energy storage system is relatively simple. Each three phases is a group of control units. It does not need to coordinate according to the performance differences of parallel energy storage units before responding to instructions, which shortens the response time of the energy storage system.

[0059] 6. High-voltage direct-mounted grid-type energy storage system is suitable for occasions with high requirements on energy storage control performance such as inertia support, stable control, rapid frequency and voltage regulation, such as new energy power station energy storage, independent energy storage, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a flow chart of the overall method of the present invention;

[0061] Figure 2 It is a flow chart of a method for calculating output active power and reactive power of a high-voltage direct-mounted energy storage system of the present invention;

[0062] Figure 3 is a flow chart of a method for calculating an internal voltage phase reference value and an internal voltage amplitude reference value of the present invention;

[0063] Figure 4 is a flow chart of a method for calculating a first reference value of current according to the present invention;

[0064] Figure 5 It is a flow chart of the method for calculating the three-phase modulation voltage reference value of the present invention. DETAILED DESCRIPTION

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

[0066] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0067] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0068] Example:

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

[0070] S1: sampling and calculating the output active power and reactive power of the high-voltage direct-mounted energy storage system; obtaining the internal voltage phase reference value and the internal voltage amplitude reference value respectively through calculation of the active power control law and the reactive power control law;

[0071] S2: Calculate the equivalent internal voltage according to 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 ​​of the internal voltage d-axis and q-axis 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 value of the current of the d-axis and the q-axis according to the first reference value of the current and the current limit value as the current given value; use the output current as the current feedback, adjust the output current through the proportional integral controller, and 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-mounted energy storage system to generate voltage based on the reference value.

[0073] Wherein, in step S1, Figure 2 As shown, the output active power and reactive power of the high-voltage direct-mounted energy storage system are sampled and calculated, specifically:

[0074] Collect the three-phase voltage and three-phase output current of the high-voltage direct-mounted energy storage system grid connection point, and the three-phase voltage is recorded as U a , U b , U c , the three-phase output current is recorded as Ia ,I b ,I c ;

[0075] 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-mounted energy storage system are calculated respectively;

[0076] In the dq rotating coordinate system, the active power and 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] Among them, 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 respectively;

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

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

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

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

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

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

[0086] Among them, ΔU is the change of the internal voltage amplitude reference value, K q and K i are the proportional and integral control coefficients, Q ref is the reactive power reference value of the high-voltage direct-mounted energy storage system, and Q is the reactive power actually output by the high-voltage direct-mounted energy storage system.

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

[0088] The modulation voltage reference values ​​of the d-axis and q-axis of the previous control cycle are extracted from the high-voltage direct-mounted energy storage system controller module and recorded as The equivalent internal voltages of the d-axis and q-axis are calculated based on the extracted modulation voltage reference values, which are denoted as e d 、e q , the calculation formula is as follows:

[0089]

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

[0091] In step S2, calculating the virtual impedance voltage includes:

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

[0093] Collect the current output current i from the high-voltage direct-mounted energy storage system abc , the output current i abc is the three-phase output current;

[0094] The three-phase current i abc Use Park transformation to transform from the abc coordinate system to the dq rotation coordinate system to obtain i dq ;

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

[0096]

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

[0098] For the q-axis, the virtual impedance voltage u vq The calculation formula is:

[0099]

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

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

[0102] When the internal voltage amplitude reference value is set to the given value of the d-axis, the high-voltage direct-mounted energy storage system will try to control the actual d-axis voltage to be close to this reference value; setting the given value of the q-axis to 0 means that the high-voltage direct-mounted energy storage system hopes that the q-axis voltage will be kept at 0 or close to 0, which is usually related to the control of reactive power. In order to achieve specific control goals, the voltages of the d-axis and q-axis need to be controlled differently;

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

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

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

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

[0107] In step S3, the second reference values ​​of the currents of the d-axis and the q-axis are calculated, specifically:

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

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

[0110] i d，ref2 =min(|i d，ref1 |,I lim )×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 Represent the second reference value of the current of the d-axis and q-axis, I lim Indicates the current limit value, the min() function is used to take a 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 a 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 through sensors actual ;

[0115] Compare the actual current with the set reference current and calculate the current error e(t):

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

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

[0118]

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

[0120] The current error e(t) is input to the PI controller and the output u(t) of the PI controller is calculated. For discrete-time systems, the output of the PI controller can be calculated by 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 three-phase modulation voltage reference value is obtained, specifically:

[0124] According to the Park inverse transform, U α , U βDetermine the sector where the reference voltage is located. In the SVPWM (space vector pulse width modulation) algorithm, it is usually based on U α , U β The value of is used to determine in which sector the reference voltage vector is located;

[0125] Selecting boundary vectors of the synthetic reference voltage according to the sectors, the boundary vectors being two non-zero vectors and one zero vector adjacent to the reference voltage vector;

[0126] The action time of the two boundary vectors is calculated according to the amplitude of the reference voltage. In one carrier cycle, the product of the reference voltage vector and the action time of each boundary vector is equal to the product of the carrier cycle and the reference voltage vector.

[0127] The over-modulation judgment and processing of the action time of the two boundary vectors are performed. If the calculated action time exceeds the allowable range, corresponding adjustments need to be made to avoid over-modulation;

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

[0129] The voltage reference values ​​on the d-axis and q-axis are converted to the three-phase abc axis, and the voltage components on the dq-axis are converted back to the voltage components in the abc three-phase coordinate system using Park inverse transformation;

[0130] The H-bridge of each module in the high-voltage direct-mounted cascade energy storage system is driven to generate voltage. Specifically, based on the generated three-phase modulation voltage reference value, the H-bridge of each module in the high-voltage direct-mounted cascade energy storage system is driven to generate corresponding voltage through the SPWM modulation strategy.

[0131] In addition, this embodiment also provides a high-voltage direct-mounted grid-connected energy storage grid-connected control system, which is used to implement any of the above-mentioned high-voltage direct-mounted grid-connected energy storage grid-connected control methods.

[0132] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A high-voltage direct-hanging grid-connected energy storage control method, characterized in that: The steps include: S1: sampling and calculating the output active power and reactive power of the high-voltage direct-mounted energy storage system; obtaining the internal voltage phase reference value and the internal voltage amplitude reference value respectively through calculation of the active power control law and the reactive power control law; S2: Calculate the equivalent internal voltage according to 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 ​​of the internal voltage d-axis and q-axis 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; S3: Calculate the second reference value of the current of the d-axis and the q-axis according to the first reference value of the current and the current limit value as the current given value; use the output current as the current feedback, adjust the output current through the proportional integral controller, and obtain the modulation voltage reference value; The internal voltage phase reference value is used for coordinate transformation to obtain a three-phase modulation voltage reference value, and the H-bridge of each module in the high-voltage direct-mounted energy storage system is driven to generate voltage based on the reference value.

2. A high-voltage direct-mounted grid-connected energy storage control method according to claim 1, characterized in that: In step S1, sampling and calculating the output active power and reactive power of the high-voltage direct-mounted energy storage system includes: Collect the three-phase voltage and three-phase output current of the high-voltage direct-mounted energy storage system grid connection point, and the three-phase voltage is recorded as U a , U b , U c , the three-phase output current is recorded as I a ,I b ,I c ; 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-mounted energy storage system are calculated respectively; In the dq rotating coordinate system, the active power and reactive power can be calculated by the following formula: P=U d ·AND d +U q ·AND q Q=U d ·I d -U q ·I q Among them, U d and U q are the d-axis and q-axis components of the grid-connected point voltage, I d and I q They are the d-axis and q-axis components of the output current respectively.

3. A high-voltage direct-mounted grid-connected energy storage control method according to claim 2, characterized in that: In the step S1, the internal voltage phase reference value and the internal voltage amplitude reference value are obtained respectively, including: Given the active power reference value of the high-voltage direct-mounted energy storage system, combined with the output active power of the high-voltage direct-mounted energy storage system and the rated angular frequency of the power grid, the internal voltage phase reference value is calculated through the active power control law. The calculation formula is as follows: Δθ=K p (P ref -P)+K i ∫(P ref -P)dt Among them, Δθ is the change of the internal voltage phase reference value, K p and K i are proportional and integral control coefficients, P ref is the active power reference value of the high-voltage direct-mounted energy storage system, and P is the active power actually output by the high-voltage direct-mounted energy storage system; Given the reactive power reference value of the high-voltage direct-mounted energy storage system, combined with the output reactive power of the high-voltage direct-mounted energy storage system, the reactive power reference value and the rated output voltage amplitude, the internal voltage amplitude reference value is calculated through the reactive power control law. The calculation formula is as follows: ΔU=K q (Q ref -Q)+K i ∫(Q ref -Q)dt Among them, ΔU is the change of the internal voltage amplitude reference value, K q and K i are the proportional and integral control coefficients, Q ref is the reactive power reference value of the high-voltage direct-mounted energy storage system, and Q is the reactive power actually output by the high-voltage direct-mounted energy storage system.

4. A high-voltage direct-mounted grid-connected energy storage control method according to claim 3, characterized in that: In the step S2, calculating the equivalent internal voltage includes: The modulation voltage reference values ​​of the d-axis and q-axis of the previous control cycle are extracted from the high-voltage direct-mounted energy storage system controller module and recorded as The equivalent internal voltages of the d-axis and q-axis are calculated based on the extracted modulation voltage reference values, which are denoted as e d 、e q , the calculation formula is as follows: Among them, K mod It represents the modulation equivalent gain, which is a constant or a coefficient that changes according to the characteristics of the high-voltage direct-mounted energy storage system.

5. A high-voltage direct-mounted grid-connected energy storage control method according to claim 4, characterized in that: In the step S2, obtaining the first reference value of the current includes: Setting the virtual resistance and virtual inductance of the high-voltage direct-mounted energy storage system, and calculating the virtual impedance voltages of the d-axis and the q-axis according to the set virtual resistance and virtual inductance and the output current; The equivalent internal voltage is regulated in a closed loop through a proportional-integral controller; Based on the adjusted equivalent internal voltage, a first reference value of the current is calculated.

6. A high-voltage direct-mounted grid-connected energy storage control method according to claim 5, characterized in that: In step S3, calculating the second reference values ​​of the currents of the d-axis and the q-axis includes: The first reference values ​​of the current on the d-axis and q-axis obtained in step S2 are respectively denoted as i d，ref1 、i q，ref1 ; The current limit value of the high-voltage direct-mounted energy storage system is set, and the second reference value of the current of the d-axis and the q-axis is calculated according to the first reference value of the current and the current limit value. The calculation formula is: in d，ref2 =min(|i d，ref1 |,I lim )×sign(i d，ref1 ) in q，ref2 =min(|i q，ref1 |,I lim )×sign(i q，ref1 ) Among them, i d，ref2 and i q，ref2 Represent the second reference value of the current of the d-axis and q-axis, I lim Indicates the current limit value, the min() function is used to take a smaller value, and the sign() function is used to retain the sign of the current.

7. A high-voltage direct-mounted grid-connected energy storage control method according to claim 6, characterized in that: In step S3, obtaining a three-phase modulation voltage reference value includes: According to the Park inverse transform, U α , U β Determine the sector where the reference voltage is located; Selecting a boundary vector of a synthetic reference voltage according to the sector; Calculate the time when two boundary vectors act respectively according to the amplitude of the reference voltage; Conduct overmodulation judgment and processing on the action time of two boundary vectors; Calculate and allocate the time for seven-segment vector synthesis; Convert the voltage reference values ​​on the d-axis and q-axis to the three-phase abc-axis.

8. A high-voltage direct-mounted grid-connected energy storage control method according to claim 7, characterized in that: In the step S3, driving the H-bridge of each module in the high-voltage direct-mounted cascade energy storage system to generate voltage includes: based on the generated three-phase modulation voltage reference value, driving the H-bridge of each module in the high-voltage direct-mounted cascade energy storage system to generate corresponding voltage through the SPWM modulation strategy.

9. A high-voltage direct-mounted grid-connected energy storage control system, characterized in that: Used to implement a high-voltage direct-mounted grid-connected energy storage control method as described in claims 1-8 above.

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