Black start transient fault ride-through method and system based on bridge arm energy storage type network configuration SVG

Abstract

The application discloses a black-start transient fault ride-through method and system based on a bridge arm energy storage type network configuration SVG, relates to the technical field of black-start control of power grids, and comprises the following steps: a new energy station black-start system is built, the black-start system comprises an energy storage power station and a bridge arm energy storage type network configuration SVG, and the energy storage power station serves as a main black-start power supply; the bridge arm energy storage type network configuration SVG detects the frequency of the black-start system at any time; when it is detected that the frequency of the black-start system is lower than a preset action threshold value, the energy storage power station has a transient fault; the bridge arm energy storage type network configuration SVG is put into an energy storage unit, the control mode is switched from reactive power priority to active power priority, the active current amplitude limiting value and the reactive current amplitude limiting value are dynamically adjusted according to the frequency of the black-start system, and active power is preferentially output; and when the frequency of the black-start system returns to a normal range, the bridge arm energy storage type network configuration SVG returns to the reactive power priority mode and exits the active power support state. The method can improve the stability and anti-interference capability of the black-start process.

Description

Technical Field

[0001] This invention relates to the field of power grid black start control technology, specifically to a black start instantaneous fault ride-through method and system based on bridge arm energy storage type grid SVG. Background Technology

[0002] As power systems continue to expand, their structures and operating modes become increasingly complex and variable. Against this backdrop, system stability issues are becoming increasingly prominent. High-risk disasters and human error can lead to frequent large-scale power outages, significantly impacting the socio-economic landscape and people's daily lives. Therefore, researching black-start technology and developing rapid system recovery plans is crucial. Black-start refers to the process of gradually restoring the power grid to operation without external power support after a complete power outage. The most basic and critical condition for this process is the availability of a reliable black-start power source. Traditionally, hydropower stations, pumped-storage power stations, and gas turbines have been selected as black-start power sources. However, with the increasing proportion of new energy sources such as photovoltaic and wind power in the power grid, traditional black-start control strategies are insufficient to meet the flexibility and stability requirements of modern power grids. Therefore, utilizing new energy sources to replace traditional hydropower and gas turbine units as black-start power sources has garnered widespread attention and research. Photovoltaic and wind turbine output is limited by the external environment, exhibiting significant randomness and volatility, and cannot independently serve as the main control power source for black-start operations. Therefore, the industry generally adopts a "new energy + energy storage" joint model to participate in grid black start: the energy storage system acts as the main control power source, using grid-based V / f control to establish islanded voltage and frequency; photovoltaic and wind power act as auxiliary power sources, using grid-following constant power control to achieve maximum power output. However, the energy storage system is vulnerable and under great control pressure in the early stages of black start, and is prone to grid disconnection or shutdown due to control anomalies, communication failures, or momentary short circuits. Once the energy storage fails, the system will lose its only voltage / frequency support, leading to black start failure or even the expansion of the accident.

[0003] To enhance voltage and frequency support capabilities in weak grid and islanded scenarios, modular multilevel (MMC) grid-type static var generators (SVGs) are widely used. These grid-type SVGs simulate the inertia and damping characteristics of a synchronous machine by controlling the virtual synchronous generator (VSG). They can autonomously build voltage, regulate frequency, and provide inertia support without relying on a phase-locked loop (PLL), effectively suppressing voltage fluctuations and enhancing system transient stability. Furthermore, integrating energy storage units into the SVG arms forms arm-type grid-type SVGs with energy storage capabilities. This allows them to provide reactive power support while also possessing short-term active power throughput capabilities, enabling rapid output of active power during faults to compensate for system power deficits.

[0004] Existing technologies include solutions for black start and multi-machine coordinated control of photovoltaic power plant grids, and some literature proposes topology and control frameworks for energy storage-based grid-connected SVG (Static Var Generator) systems for voltage support in weak grids / islanded environments. However, existing technologies still have significant shortcomings: First, most solutions focus on the black start process under normal operating conditions, without proposing effective countermeasures for the critical risk scenario of instantaneous failure of the main energy storage power source during black start; second, existing research on energy storage-based grid-connected SVG systems mainly focuses on steady-state or transient voltage support, without designing complete input, switching, and de-input control logic for the black start sequence of new energy power plants, resulting in insufficient engineering practicality.

[0005] In summary, under the background of high proportion of new energy grid connection, how to achieve rapid replacement of instantaneous failure of energy storage power supply, maintain system voltage and frequency stability, and ensure continuous and reliable black start process are the key technical problems that urgently need to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a black-start instantaneous fault ride-through method and system based on bridge-arm energy storage type SVG. During the black-start process of a new energy power station, when a control fault occurs in the energy storage power station, the bridge-arm energy storage type SVG is used to temporarily replace the energy storage power station, establish and maintain the system voltage and frequency, and improve the stability and anti-interference capability of the black-start process.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the first embodiment of the present invention provides a black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG, comprising:

[0009] A black start system for new energy power plants is constructed. The black start system includes a thermal power plant, a photovoltaic power plant, a wind farm, an energy storage power station, and a bridge arm energy storage grid SVG. The energy storage power station serves as the main black start power source, and the voltage and frequency of the black start system are established using V / f control.

[0010] The SVG of the bridge arm energy storage grid constantly monitors the frequency of the black start system.

[0011] When the black start system frequency is detected to be lower than the preset action threshold, the energy storage power station experiences a momentary fault.

[0012] When the SVG of the bridge arm energy storage network is put into the energy storage unit, the control mode is switched from reactive priority to active priority. The active current limit and reactive current limit are dynamically adjusted according to the black start system frequency, and the active power is output first to support the black start system frequency.

[0013] Once the black-start system frequency returns to the normal range, the bridge arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

[0014] Furthermore, it also includes: detecting the state of charge of the energy storage units of the bridge arm energy storage network SVG to maintain the state of charge within a preset safe range.

[0015] Furthermore, the dynamic adjustment of the active current limit and reactive current limit based on the black-start system frequency specifically includes:

[0016] Set three times the rated current of the converter under normal operating conditions as the total output current limit. Total output current limit and active current limit With reactive current limiting value The relationship between them is:

[0017] ;

[0018] When the system frequency decreases, the active current limit increases and the reactive current limit decreases. The dynamic adjustment satisfies the following formula:

[0019] ;

[0020] ;

[0021] in, Minimum reactive current limiting is used to ensure necessary reactive power transmission and support system voltage. It is the active power limit amplitude under normal operating conditions. I N The rated current of the converter under normal operating conditions is given by f, where f is the per-unit value of the black-start system frequency. Active current, This is reactive current.

[0022] Furthermore, the bridge arm energy storage network SVG adopts a modular multilevel converter topology, with several energy storage units connected in series in each bridge arm. The energy storage unit is composed of a half-bridge submodule and a DC / DC converter.

[0023] Furthermore, the startup sequence of the black-start system is as follows: first, start the energy storage power station to establish voltage and frequency, then put the bridge arm energy storage grid SVG into operation, then connect the photovoltaic power station to the grid, then connect the thermal power plant to the grid, and finally connect the wind farm to the grid.

[0024] Secondly, another embodiment of the present invention provides a black-start instantaneous fault ride-through system based on bridge arm energy storage grid SVG, comprising:

[0025] The system setup module is used to build black start systems for thermal power plants, photovoltaic power plants, wind farms, energy storage power plants, and bridge arm energy storage grid SVG.

[0026] The bridge-arm energy storage network SVG constantly monitors the black-start system frequency. When the black-start system frequency is detected to be lower than the preset action threshold, a momentary fault occurs in the energy storage power station. The bridge-arm energy storage network SVG then activates the energy storage unit and switches the control mode from reactive power priority to active power priority. It dynamically adjusts the active current limit and reactive current limit according to the black-start system frequency, prioritizing the output of active power to support the black-start system frequency. When the black-start system frequency returns to the normal range, the bridge-arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

[0027] Furthermore, it also includes a state of charge detection module, which is used to detect the state of charge of the energy storage units of the bridge arm energy storage network SVG, so that the state of charge is maintained within a preset safe range.

[0028] Furthermore, the bridge arm energy storage network SVG includes a dynamic adjustment module, which is used to dynamically adjust the active current limit value and the reactive current limit value according to the black start system frequency, specifically including:

[0029] Set three times the rated current of the converter under normal operating conditions as the total output current limit. Total output current limit and active current limit With reactive current limiting value The relationship between them is:

[0030] ;

[0031] When the system frequency decreases, the active current limit increases and the reactive current limit decreases. The dynamic adjustment satisfies the following formula:

[0032] ;

[0033] ;

[0034] in, Minimum reactive current limiting is used to ensure necessary reactive power transmission and support system voltage. It is the active power limit amplitude under normal operating conditions. I N The rated current of the converter under normal operating conditions is given by f, where f is the per-unit value of the black-start system frequency. For active current, This is reactive current.

[0035] Furthermore, the bridge arm energy storage network SVG adopts a modular multilevel converter topology, with several energy storage units connected in series in each bridge arm. The energy storage unit is composed of a half-bridge submodule and a DC / DC converter.

[0036] Furthermore, the startup sequence of the black-start system is as follows: first, start the energy storage power station to establish voltage and frequency, then put the bridge arm energy storage grid SVG into operation, then connect the photovoltaic power station to the grid, then connect the thermal power plant to the grid, and finally connect the wind farm to the grid.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] This invention provides a black-start instantaneous fault ride-through method and system based on bridge-arm energy storage type grid SVG. By utilizing the grid-building voltage establishment, short-term energy storage support and virtual synchronous machine inertial characteristics of bridge-arm energy storage type grid SVG, the control mode can be quickly switched at the moment of energy storage power station failure. It can replace the energy storage power station to establish and maintain system voltage and frequency, effectively avoid interruption during black start, and greatly improve the black start success rate and reliability of new energy power stations. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0040] Figure 1 This is a schematic diagram of the grid connection control method for an energy storage system.

[0041] Figure 2 This is a schematic diagram of the grid-connected control method for a photovoltaic system.

[0042] Figure 3 This is a diagram of the SVG topology for a bridge arm energy storage network.

[0043] Figure 4 Diagram of the overall control framework of the bridge arm energy storage network SVG;

[0044] Figure 5 A flowchart of a black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG provided in an embodiment of the present invention;

[0045] Figure 6 The waveform of the bus voltage when a single-phase short-circuit fault occurs in the energy storage power station during black start-up;

[0046] Figure 7 The waveform of the bus voltage when a two-phase short-circuit fault occurs in the energy storage power station during black start-up;

[0047] Figure 8 The bus voltage waveform diagram is shown when a three-phase short-circuit fault occurs in the energy storage power station during black start-up.

[0048] Figure 9 The diagram shows the system frequency waveform when a single-phase short-circuit fault occurs in the energy storage power station during black start-up.

[0049] Figure 10 The diagram shows the system frequency waveform when a two-phase short-circuit fault occurs in the energy storage power station during black start-up.

[0050] Figure 11 This is a waveform diagram of the system frequency when a three-phase short-circuit fault occurs in the energy storage power station during black start-up. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0052] Structure and common controls of photovoltaic-storage integrated systems:

[0053] For power grids with a high proportion of photovoltaic (PV) power generation, configuring energy storage to form a combined PV-storage power generation system for black start is highly feasible. The combined PV-storage system consists of two parts: an energy storage system and a PV power generation system. The energy storage system serves as the black start power source, employing a grid-connected VSG control strategy to ensure its voltage and frequency support capabilities and deployment capability. The PV units serve as the non-black start power source, using grid-connected constant power control to guarantee maximum power generation and the highest possible energy conversion efficiency.

[0054] Energy storage system structure and typical control methods:

[0055] Energy storage system grid connection structure and control methods, such as Figure 1 As shown, the photovoltaic system is connected to the DC bus via a bidirectional DC / DC converter and then fed into the grid through a PCS. During the grid black start process, the output of the photovoltaic system fluctuates due to the intermittent and fluctuating nature of solar energy. To ensure a stable power supply, an energy storage system assists the photovoltaic system in taking over as the main control power source for black start. By storing and releasing energy, the photovoltaic output is smoothed, ensuring that the system continuously and stably supplies power to the load.

[0056] Figure 1 middle, The DC current output by the energy storage system; The DC voltage output by the DC / DC converter; The phase angle is obtained through a phase-locked loop at the system reference frequency. ; This is the measured value of the grid-side voltage; This is the filter inductor current; Given an outer loop voltage reference signal; The inner loop current reference signal generated for the outer loop control; , These represent the voltage and current along the dq axis after coordinate transformation.

[0057] In a typical control structure of an energy storage system, a bidirectional DC / DC converter controls the DC current output by the energy storage battery to maintain a constant DC voltage and achieve bidirectional energy transfer between the energy storage system and the grid. The energy storage system's PCS uses V / f control to provide stable voltage and frequency support for grid recovery. Simultaneously, the energy storage system balances issues such as the mismatch between photovoltaic system output and load power, providing stable and reliable power support to the grid.

[0058] Photovoltaic system structure and typical control methods:

[0059] A two-stage photovoltaic grid-connected system is selected, and its system structure and control method are as follows: Figure 2 As shown in the diagram, the unidirectional DC / DC converter in this system implements MPPT control and boost functions, while the DC / AC converter is responsible for converting DC power into AC power to meet the power supply needs of AC loads or the power grid. This design simplifies the control structure and improves the overall performance of the system.

[0060] Figure 2 middle, This refers to the DC voltage output by the photovoltaic array. This refers to the direct current output by the photovoltaic array. The DC voltage output by the DC / DC converter; The voltage reference value obtained from MPPT control is used as the outer loop reference signal for the DC / DC converter voltage. This refers to the grid connection current. The input voltage is used to obtain the phase angle through a phase-locked loop. and frequency ; This refers to the reactive power on the grid side. , These are the voltage and reactive power reference signals for the PCS outer loop control, respectively. , The voltage and current along the dq axis after coordinate transformation. This is the reference signal for the inner loop current.

[0061] In a typical photovoltaic (PV) system control structure, a unidirectional DC / DC circuit is primarily used to implement MPPT (Multi-Level Photovoltaic Power) control, ensuring the PV array always operates in optimal condition, thus providing a stable and reliable power output for system recovery. The DC / AC converter employs constant DC voltage / constant reactive power control. This maintains a constant DC bus voltage and ensures that the PV system outputs only active power during black start, operating at unity power factor, maximizing energy conversion efficiency, reducing reactive power loss, and preventing grid connection interference with system recovery.

[0062] Bridge arm energy storage grid SVG:

[0063] Renewable energy power plants are subject to significant power output fluctuations due to natural conditions, which severely impacts the quality of grid voltage. Grid-type static var generators (SVG), by simulating the operating characteristics of synchronous machines, can assist the system in establishing voltage and frequency, and actively provide inertia or reactive power support during transients. Applied to photovoltaic / wind power grid connection points, they can significantly improve the operational stability of renewable energy power plants that converge at the grid end via long-distance transmission lines.

[0064] Using a Modular Multilevel Converter (MMC) as the main topology, by adding ESM energy storage units to the bridge arms, a result can be obtained as follows: Figure 3 The diagram shows a bridge arm energy storage type grid SVG topology. The DC side of this topology consists of several sub-modules, the number of which can be freely configured according to the voltage level. Each bridge arm is connected in series with an ESM energy storage unit formed by a half-bridge sub-module combined with a DC / DC converter. The number of energy storage units can be configured as needed. Furthermore, the modular multi-level topology allows operation under grid asymmetry conditions with low output voltage harmonic content and low filtering requirements.

[0065] Figure 3 middle, For the DC side voltage of the grid-type SVG, This is a regular submodule. As an energy storage unit, for Three-phase upper bridge arm voltage for Three-phase lower bridge arm voltage; for Three-phase upper bridge arm current, for Three-phase lower bridge arm current; Output voltage for the submodule. This refers to the capacitor voltage of the submodule. This represents the current flowing through the submodule; , These are the bridge arm resistors and bridge arm inductors, respectively. For switching devices IGBT, It is an anti-parallel diode.

[0066] The overall control framework of the bridge arm energy storage grid SVG is as follows: Figure 4 As shown, the main control loops include VSG control and voltage-current dual closed-loop control. The basic idea of ​​VSG control is to simulate the speed governor and excitation regulator of a synchronous generator based on the flexible and controllable characteristics of power electronic devices. Damping coefficients and inertia constants are introduced into the inverter control, giving the distributed generation unit the characteristics of a synchronous generator. In VSG control, the active power-frequency regulator includes the rotor motion equation and prime mover regulation equation of the synchronous generator. The rotor motion equation is shown below, reflecting the inertia and damping characteristics of the generator rotor:

[0067] (1)

[0068] In equation (1), J is the moment of inertia; and These are the rated angular frequency and the actual angular frequency, respectively; T m T represents mechanical torque; e Represents electromagnetic torque; D is the damping coefficient; P m P represents mechanical power; e Indicates electromagnetic power; For the angle of attack.

[0069] The speed regulation formula for the prime mover is:

[0070] (2)

[0071] In equation (2), P ref The active power command is given by P, and the droop parameter is given by K. The regulator detects the frequency deviation and obtains the power deviation through the active power droop, thereby changing P. m Thus controlling P e This allows for adjustment of the output frequency.

[0072] Figure 4 middle, and These are the three-phase voltage and three-phase current at the grid connection point, respectively. , and These are respectively smoothing reactance, filter capacitor, and line reactance; , These are the calculated active power input value and reactive power input value, respectively. , , and These are the reference values ​​for angular frequency, effective voltage, active power, and reactive power, respectively. and These are the calculated phase angle and voltage, respectively; and These represent the voltage and current in the dq axis coordinate system, respectively. and These are the reference voltage values ​​for the d-axis and q-axis, respectively; This is the three-phase modulated voltage signal after Parker transformation; This refers to the DC-side voltage of the SVG (Static Var Generator) in the bridge arm energy storage network. The SVG in the bridge arm energy storage network can synchronize with the grid without the need for a PLL (Programmable Logic Controller) in its overall control system.

[0073] like Figure 5 As shown, the first embodiment of the present invention provides a black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG, comprising:

[0074] A black start system for new energy power plants is constructed. The black start system includes a thermal power plant, a photovoltaic power plant, a wind farm, an energy storage power station, and a bridge arm energy storage grid (SVG). The energy storage power station serves as the main black start power source, and V / f control is used to establish the voltage and frequency of the black start system.

[0075] The bridge arm energy storage grid SVG constantly monitors the black start system frequency.

[0076] When the black start system frequency is detected to be lower than the preset action threshold, the energy storage power station experiences a momentary fault.

[0077] When the SVG of the bridge arm energy storage network is put into the energy storage unit, the control mode is switched from reactive priority to active priority. The active current limit and reactive current limit are dynamically adjusted according to the black start system frequency, and the active power is output first to support the black start system frequency.

[0078] Once the black-start system frequency returns to the normal range, the bridge arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

[0079] Based on the PSCAD / EMTDC simulation platform, a black-start system simulation model was built. The black-start system consists of a thermal power plant, a photovoltaic power station, a wind farm, an energy storage power station, and a bridge-arm energy storage grid SVG, possessing multiple regulation resources. The thermal power plant adopts a synchronous generator model with excitation and speed control systems, and the prime mover is a steam turbine to more accurately represent the transient characteristics of the thermal power plant, reflecting its ability to support and regulate grid voltage and frequency during black-start. The photovoltaic power station uses photovoltaic arrays, enabling variable parameter control such as temperature and light intensity, thus achieving flexible power control. The wind farm adopts a wind power generation system model based on a doubly-fed induction generator, with a frequency response module added to its generator-side converter power control loop. The energy storage power station is equivalent to a battery module, and the bridge-arm energy storage grid SVG adopts a modular multi-level structure and uses grid-type control to assist in establishing the grid system frequency and voltage.

[0080] The core of black start is to utilize a power source with black start capability to drive a power source without non-black start capability, continuously expanding the system's power generation, gradually connecting the load, and ultimately restoring the entire system. Therefore, the selection and activation of the black start power source plays a decisive role in system power restoration. A black start power source needs to possess characteristics such as the ability to establish and maintain the voltage and frequency of a single sub-section of the microgrid, the ability to stably provide power output, and good dynamic performance.

[0081] In this black-start system, the randomness and volatility of power output from photovoltaic (PV) systems and wind farms can easily cause frequency fluctuations in the power grid, making them incapable of independent startup. Therefore, the energy storage power station needs to employ V / f control to establish the grid-connected bus voltage and frequency in islanded mode, ensuring a safe and reliable startup of the power grid. Once the grid-connected bus voltage established by the energy storage power station stabilizes, the PV system obtains the corresponding voltage and phase angle signals through a phase-locked loop (PLL) and uses constant power control for grid connection. The main objective is to maintain the stability of the DC-side voltage and the balance of reactive power in the PV system, while simultaneously achieving MPPT (maximum power point tracking) control. Simultaneously, the thermal power plant is connected to the grid through a PLL using constant power control to provide stable power output, further stabilizing the system frequency and voltage. Finally, the wind farm is connected to the grid, achieving a complete black start.

[0082] In the aforementioned black start process, the bridge-arm energy storage grid-connected SVG possesses a certain energy reserve and can simulate the speed governor and excitation system of a synchronous generator. It can participate in black start as an auxiliary power source when the energy storage power station serves as the primary power source. Specifically, this can be divided into the following two scenarios:

[0083] (1) Normal self-start of energy storage power station: The energy storage system adopts V / f control. First, it is necessary to establish the voltage and frequency of the grid-connected bus to provide conditions for the safe and reliable start-up of the power grid. Since the bridge arm energy storage type grid SVG also has the ability to build the system frequency and voltage, putting it into the system as early as possible can improve the overall stability of the power grid system in the early stage of black start. Therefore, when the energy storage power station is in normal self-start, after it has established the system voltage and frequency, and before the photovoltaic power generation is connected to the grid, the bridge arm energy storage type grid SVG can be put into operation to provide reactive power to the system, further stabilize the system voltage, and provide inertia through VSG control.

[0084] (2) Self-starting failure of energy storage power station: If the energy storage power station fails during black start, it will be difficult to establish a stable system frequency and voltage, affecting the black start process. At this time, the energy storage power station can be temporarily shut down and the bridge arm energy storage grid SVG can be used as an emergency power source to support the system frequency and voltage for a short time. After the energy storage power station fault is cleared, the energy storage power station can be put back into operation to establish the system frequency and voltage.

[0085] This method clarifies the input, operation, and exit strategies of SVG at different stages of black start, and is highly matched with the start-up sequence of energy storage, photovoltaic, wind power, and conventional power sources. The control logic is clear and easy to implement in engineering, and can provide practical and feasible technical support for grid restoration in scenarios with a high proportion of new energy grid connection.

[0086] The SVG (Static Var Generator) in the bridge arm energy storage network constantly monitors the system frequency. When a fault occurs in the energy storage station and the active power output decreases, the system frequency also decreases. When the system frequency drops below the activation threshold, the energy storage unit is activated, and the control mode of the SVG in the bridge arm energy storage network is changed from reactive power control to active power control, providing active power support to the system and stabilizing the system frequency. When activating the energy storage unit, dynamic priority control can be used to increase the active current amplitude and decrease the reactive current amplitude, thereby allowing more active power to be output to the system through the SVG in the bridge arm energy storage network. Under normal circumstances, the active current limit and reactive current limit of the SVG in the bridge arm energy storage network are fixed values ​​and satisfy the following formula:

[0087] (3)

[0088] in, The total amplitude of the output current limit can generally be set to 3 times the rated current. and These are the active current limit and the reactive current limit, respectively.

[0089] By differentiating between active and reactive current limits, the power priority of the SVG (Static Var Generator) in the bridge arm energy storage network can be differentiated. When the limits for active and reactive currents are equal, the power priorities are equal, with no order of precedence. When the active current limit is greater than the reactive current limit, the SVG prioritizes active power transmission; when the active current limit is less than the reactive current limit, the SVG prioritizes reactive power transmission. Typically, the SVG in the bridge arm energy storage network is mainly used to ensure the stability of the bus voltage, employing a reactive power priority mode. Through a dynamic adjustment mechanism for active / reactive current limits, the SVG operates in reactive power priority mode under normal operating conditions, providing stable reactive power support and suppressing voltage fluctuations for the renewable energy power station. When a fault in the energy storage power station is detected causing a drop in the black-start system frequency, it automatically switches to active power priority mode, briefly outputting active power to support the system frequency. After the fault is recovered, it automatically returns to reactive power support mode. This control logic balances steady-state operation requirements with fault ride-through capability, offering flexible and highly adaptable control.

[0090] During a power storage station failure, in order to activate the energy storage units and output active power into the system, the following dynamic priority adjustment mechanism can be introduced:

[0091] (4)

[0092] (5)

[0093] in, Minimum reactive current limiting ensures necessary reactive power transmission and supports system voltage. It is the active power limit amplitude under normal operating conditions. I N The rated current of the converter under normal operating conditions is given by f, where f is the per-unit value of the system frequency. For active current, This is reactive current.

[0094] The main functions of the above-mentioned links are as follows: When the system is running in normal steady state, the reactive current limit of the bridge arm energy storage network SVG is relatively large, and it is mainly used as a reactive power support device; when the energy storage power supply fails instantaneously during black start, the system temporarily loses the active power supply and needs to output active power to the system. The limiting link detects the decrease in system frequency and gradually increases the active current limit according to equation (4). As the current increases, the reactive current limit of the SVG in the bridge arm energy storage network gradually decreases, changing from reactive priority mode to active priority mode, and using 3 times the rated current as the final limit. After the fault ends, the system frequency recovers, and according to equations (4) and (5), the active current limit decreases and returns to the normal value, the reactive current limit increases and returns to the normal value, and the SVG is used as a reactive current support device again.

[0095] In addition, to avoid overcharging or over-discharging of the energy storage unit and extend its lifespan, the following SOC (State of Charge) detection and protection control is set up to keep the state of charge of the energy storage unit within a suitable range.

[0096] (6)

[0097] This method monitors and limits the depth of charge and discharge of energy storage units in real time by detecting and protecting the state of charge (SOC) of the energy storage units. This avoids damage to the energy storage devices caused by overcharging and over-discharging, ensures the long-term safe and stable operation of SVG energy storage units, reduces equipment maintenance costs, and improves the overall economic efficiency of the system.

[0098] Simulation verification is carried out using a system with SVG (Static Var Generated Imager) containing bridge arm energy storage, photovoltaic / wind power plants, energy storage power stations, and thermal power plants as examples.

[0099] exist Simulation results are provided for a short-circuit fault at the outlet of the energy storage power station. The simulation results for the SVG (Static Var Generator) configuration with and without the bridge arm energy storage network in operation during the fault are as follows: Figures 6-11 As shown, where Figures 6-8 This is the per-unit waveform of the bus voltage. Figures 9-11 The waveform represents the system frequency. Simulations show that during the initial black start phase, the system is vulnerable, and if a fault occurs at the outlet of the energy storage power station, the system voltage and frequency will oscillate.

[0100] At this point, if the bridge-arm energy storage grid SVG is put into operation according to a predetermined plan based on the voltage and frequency provided by the energy storage power station, it can temporarily support the system frequency and voltage, thereby enhancing system stability. Figures 6-8 As shown, when an energy storage power station encounters short-circuit faults of varying degrees, deploying the bridge arm energy storage-type grid SVG can reduce the degree of system voltage drop; by Figures 9-11 As shown, when an energy storage power station encounters short-circuit faults of varying degrees, the deployment of the bridge-arm energy storage network SVG reduces the degree of system frequency drop and improves the recovery speed. Simulation results indicate that the deployment of the bridge-arm energy storage network SVG is beneficial to system frequency and voltage stability, further enhancing the system's anti-interference capability.

[0101] This invention provides a black-start instantaneous fault ride-through method based on bridge-arm energy storage type grid SVG. By utilizing the grid-building voltage establishment, short-term energy storage support, and virtual synchronous machine inertial characteristics of the bridge-arm energy storage type grid SVG, the control mode can be quickly switched at the moment of energy storage power station failure. This method can replace the energy storage power station to establish and maintain system voltage and frequency, effectively avoid interruption during black start, and significantly improve the success rate and reliability of black start of new energy power stations.

[0102] Another embodiment of the present invention provides a black-start instantaneous fault ride-through simulation system based on bridge arm energy storage grid SVG, comprising:

[0103] The system setup module is used to build black start systems for thermal power plants, photovoltaic power plants, wind farms, energy storage power plants, and bridge arm energy storage grid SVG.

[0104] The bridge-arm energy storage network SVG constantly monitors the black-start system frequency. When the black-start system frequency is detected to be lower than the preset action threshold, a momentary fault occurs in the energy storage power station. The bridge-arm energy storage network SVG then activates the energy storage unit and switches the control mode from reactive power priority to active power priority. It dynamically adjusts the active current limit and reactive current limit according to the black-start system frequency, prioritizing the output of active power to support the black-start system frequency. When the black-start system frequency returns to the normal range, the bridge-arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

[0105] The system also includes a state of charge detection module, which is used to detect the state of charge of the energy storage units of the bridge arm energy storage network SVG and keep the state of charge within a preset safe range.

[0106] The bridge arm energy storage network SVG includes a dynamic adjustment module, which is used to dynamically adjust the active current limit and reactive current limit based on the black start system frequency. Specifically, it includes:

[0107] Set three times the rated current of the converter under normal operating conditions as the total output current limit. Total output current limit and active current limit With reactive current limiting value The relationship between them is:

[0108] ;

[0109] When the system frequency decreases, the active current limit increases and the reactive current limit decreases. The dynamic adjustment satisfies the following formula:

[0110] ;

[0111] ;

[0112] in, Minimum reactive current limiting is used to ensure necessary reactive power transmission and support system voltage. It is the active power limit amplitude under normal operating conditions. I N The rated current of the converter under normal operating conditions is given by f, where f is the per-unit value of the black-start system frequency. Active current, This is reactive current.

[0113] In this embodiment, the bridge arm energy storage network SVG adopts a modular multilevel converter topology, with several energy storage units connected in series in each bridge arm. The energy storage unit is composed of a half-bridge submodule and a DC / DC converter.

[0114] In this embodiment, the startup sequence of the black-start system is as follows: first, start the energy storage power station to establish voltage and frequency, then put the bridge arm energy storage grid SVG into operation, then connect the photovoltaic power station to the grid, then connect the thermal power plant to the grid, and finally connect the wind farm to the grid.

[0115] The black-start instantaneous fault ride-through system based on bridge arm energy storage type grid SVG provided in this embodiment of the invention and the black-start instantaneous fault ride-through method based on bridge arm energy storage type grid SVG are based on the same inventive concept and have the same beneficial effects, and will not be described again here.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG, characterized in that, include: A black start system for new energy power plants is constructed. The black start system includes a thermal power plant, a photovoltaic power plant, a wind farm, an energy storage power station, and a bridge arm energy storage grid SVG. The energy storage power station serves as the main black start power source, and the voltage and frequency of the black start system are established using V / f control. The SVG of the bridge arm energy storage grid constantly monitors the frequency of the black start system. When the black start system frequency is detected to be lower than the preset action threshold, the energy storage power station experiences a momentary fault. When the SVG of the bridge arm energy storage network is put into the energy storage unit, the control mode is switched from reactive priority to active priority. The active current limit and reactive current limit are dynamically adjusted according to the black start system frequency, and the active power is output first to support the black start system frequency. Once the black-start system frequency returns to the normal range, the bridge arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

2. The black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG according to claim 1, characterized in that, Also includes: The state of charge (SOC) of the energy storage units in the bridge arm energy storage network SVG is monitored to maintain the SOC within a preset safe range.

3. The black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG according to claim 1, characterized in that, The bridge arm energy storage network SVG adopts a modular multilevel converter topology, with several energy storage units connected in series in each bridge arm. The energy storage unit consists of a half-bridge submodule and a DC / DC converter.

4. The black-start instantaneous fault ride-through method based on bridge arm energy storage grid SVG according to claim 1, characterized in that, The startup sequence of the black start system is as follows: first, start the energy storage power station to establish voltage and frequency, then put the bridge arm energy storage grid SVG into operation, then connect the photovoltaic power station to the grid, then connect the thermal power plant to the grid, and finally connect the wind farm to the grid.

5. A black-start instantaneous fault ride-through system based on bridge arm energy storage grid SVG, characterized in that, include: The system setup module is used to build black start systems for thermal power plants, photovoltaic power plants, wind farms, energy storage power plants, and bridge arm energy storage grid SVG. The bridge-arm energy storage network SVG constantly monitors the black-start system frequency. When the black-start system frequency is detected to be lower than the preset action threshold, a momentary fault occurs in the energy storage power station. The bridge-arm energy storage network SVG then activates the energy storage unit and switches the control mode from reactive power priority to active power priority. It dynamically adjusts the active current limit and reactive current limit according to the black-start system frequency, prioritizing the output of active power to support the black-start system frequency. When the black-start system frequency returns to the normal range, the bridge-arm energy storage network SVG reverts to reactive power priority mode and exits the active power support state.

6. The black-start instantaneous fault ride-through system based on bridge arm energy storage grid SVG according to claim 5, characterized in that, It also includes a state of charge detection module, which is used to detect the state of charge of the energy storage units of the bridge arm energy storage network SVG, so that the state of charge is maintained within a preset safe range.

7. The black-start instantaneous fault ride-through system based on bridge arm energy storage grid SVG according to claim 5, characterized in that, The bridge arm energy storage network SVG adopts a modular multilevel converter topology, with several energy storage units connected in series in each bridge arm. The energy storage unit consists of a half-bridge submodule and a DC / DC converter.

8. The black-start instantaneous fault ride-through system based on bridge arm energy storage grid SVG according to claim 5, characterized in that, The startup sequence of the black start system is as follows: first, start the energy storage power station to establish voltage and frequency, then put the bridge arm energy storage grid SVG into operation, then connect the photovoltaic power station to the grid, then connect the thermal power plant to the grid, and finally connect the wind farm to the grid.

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