Net construction type energy storage system configuration method and system for suppressing broadband oscillation

Abstract

The invention discloses a configuration method and system for a network-constructing type energy storage system for suppressing broadband oscillation, and relates to the technical field of new energy power generation grid connection and power system stability control. The invention aims to solve the problems that broadband oscillation is easily caused when a new energy field station is connected into a weak power grid, an existing suppression method affects equipment characteristics or needs additional investment, and netting type energy storage locating and sizing lacks scientific guidance. The method comprises the following steps: firstly, simplifying a system comprising a new energy station, a constructed network type energy storage system and a power grid, then carrying out impedance modeling on the two systems (reserving complete impedance characteristics of energy storage), and judging the stability through an impedance analysis method; and the optimal capacity is determined at a single position, and then the global optimal capacity and the corresponding position are determined by traversing the positions, so that low-cost broadband oscillation suppression is realized.

Description

Technical Field

[0001] This application belongs to the technical field of energy storage and grid-connected control, and relates to a configuration method and system for a grid-forming energy storage system that suppresses broadband oscillations. Background Art

[0002] With the continuous expansion of the power generation proportion and installed capacity of new energy represented by photovoltaic and wind power, the power system gradually shows the "double high" characteristics of a high proportion of renewable energy and a high proportion of power electronic devices. Renewable energy has problems such as volatility and poor peak regulation and frequency modulation capabilities, and their large-scale access poses huge challenges to the real-time power balance and frequency stability of the power system. The energy storage system has the functions of suppressing power fluctuations, maintaining system voltage and frequency stability. Therefore, energy storage systems are often required to be built in supporting for new energy power generation grid connection. The grid-connected converter is a key device connecting new energy power generation equipment and energy storage systems to the power system, and its various characteristics are significantly affected by its own control strategy. The control strategy of the grid-connected converter can be divided into grid-following control and grid-forming control.

[0003] Grid-following control realizes synchronization with the power grid through a phase-locked loop, and its external characteristics are manifested as a current source. New energy is affected by changes in weather conditions, and its power generation power is intermittent and volatile. The current source characteristics of grid-following control enable it to better track the changing power. Therefore, grid-following control is mostly used in new energy power generation equipment such as photovoltaic and wind power. However, grid-following control has disadvantages such as being unable to operate in island mode and being difficult to provide frequency and voltage support to the power grid. Grid-forming control uses power synchronization, and its external characteristics are manifested as a voltage source. It has the advantages of being able to provide support for the frequency and voltage of the power grid, being able to operate in island mode, and having good stability under weak grids. The voltage source characteristics of grid-forming control make its output power determined by the load in the system, and it is more used to balance the power fluctuations in the system, which is consistent with the role of energy storage. Therefore, grid-forming energy storage is gradually becoming a hot spot and is increasingly used in new energy supporting energy storage systems.

[0004] The large-scale access of new energy power generation equipment using grid-following control with current source characteristics has significantly changed the impedance characteristics of the system, and it is easy to interact with weak grids and cause broadband oscillation accidents. The frequent occurrence of broadband oscillation accidents will not only lead to serious deterioration of power quality, but also affect the stable operation of the power system, and even cause large-scale power outages, posing huge challenges to power system maintenance. Controlling broadband oscillations has become a key issue in the current power system.

[0005] At present, the commonly used broadband oscillation suppression methods can be divided into the source side and the grid side from the control object: 1. Starting from the source side, the negative damping characteristics can be improved by changing control parameters or control structure. For example, optimizing the phase-locked loop parameters or voltage loop parameters under subsynchronous / supersynchronous oscillation can improve the negative damping characteristics of the grid converter in this frequency band, thereby achieving the effect of suppressing wideband oscillation. However, this method significantly affects its own dynamic characteristics.

[0006] 2. From the grid side, by configuring additional flexible AC transmission devices such as static var generators with additional damping control to improve the negative damping of oscillating equipment, the oscillation suppression effect can also be achieved, but additional investment is required.

[0007] Grid connection of renewable energy power generation often requires the use of energy storage systems. In addition to their active support capabilities and peak-shaving and frequency regulation capabilities, grid-connected energy storage systems can also suppress broadband oscillations through proper location and capacity configuration. Compared to the methods mentioned above, suppressing broadband oscillations at renewable energy power plants through grid-connected energy storage systems is based on their own impedance characteristics and does not alter the dynamic characteristics of the renewable energy grid-connected converter equipment itself. Furthermore, since renewable energy grid connection itself requires the construction of energy storage systems, achieving broadband oscillation suppression using grid-connected energy storage systems does not require additional investment.

[0008] However, this method also has certain problems at this stage of research: 1. In the process of site selection and capacity determination of grid-type energy storage systems, they are often equivalent to an ideal voltage source or equivalent to a voltage source and scalar reactance, ignoring their own complete impedance characteristics, which can easily lead to deviations in stability judgment.

[0009] 2. In discussions on the impact of grid-type energy storage systems on overall system stability, most studies only consider one type of grid-type control. When using other types of grid-type control, the entire system needs to be remodeled, which lacks versatility.

[0010] There is still a lack of scientific guidance on issues such as how to accurately analyze the impact of grid-type energy storage systems on the stability of grid-type converters for new energy sources, how to determine the optimal capacity of grid-type energy storage systems to suppress broadband oscillations, and the optimal location for configuration. Summary of the Invention

[0011] This application provides a configuration method and system for a grid-type energy storage system to suppress broadband oscillations. It aims to solve the technical problems that broadband oscillations are easily caused when new energy power plants (with grid-type control) are connected to weak power grids. Existing suppression methods either affect the dynamic characteristics of the equipment or require additional investment. Furthermore, grid-type energy storage systems ignore complete impedance characteristics during site selection and capacity determination, have poor versatility, lack scientific guidance, and result in capacity redundancy, ineffective suppression, and excessively high costs.

[0012] To achieve the above objectives, this application employs the following technical means: In a first aspect, this application provides a method for configuring a grid-type energy storage system to suppress broadband oscillations, including: S1 simplifies and equivalences the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids; S2, impedance modeling is performed on the simplified equivalent new energy power station and grid-type energy storage system respectively to construct the system equivalent circuit; impedance analysis method is used to determine the system stability of the equivalent circuit; S3, determine the optimal capacity of the grid-type energy storage system at a fixed configuration location; S4. Change the configuration location of the grid-type energy storage system to determine the global optimal capacity and the corresponding optimal configuration location.

[0013] As a further improvement to this application, the simplification and equivalence of the actual system including grid-connected control renewable energy power stations, grid-connected energy storage systems, and AC power grids includes: The multiple grid-connected converters in the new energy power station are aggregated and equivalent to a single grid-connected converter model, and the multiple grid-connected converters in the grid-connected energy storage system are aggregated and equivalent to a single grid-connected converter model, thus simplifying and equipping the AC power grid.

[0014] As a further improvement of this application, the impedance modeling method is the dq impedance modeling method or the sequence impedance modeling method. When using sequence impedance modeling, the frequency coupling effect is considered and the equivalent positive and negative sequence impedances are obtained by reducing the order.

[0015] As a further improvement to this application, the impedance modeling of the simplified equivalent new energy power station and the grid-type energy storage system, and the construction of the system equivalent circuit, includes: When performing impedance modeling for new energy power plants and grid-type energy storage systems, dq impedance modeling or sequence impedance modeling methods are adopted to preserve the complete impedance characteristics of the grid-type energy storage system. After establishing the impedance models of new energy power plants and grid-type energy storage systems and their equivalents with the power grid, the new energy power plant is equivalent to a current source connected in parallel with its own impedance, the grid-type energy storage system is equivalent to a voltage source connected in series with its own impedance, and the power grid is equivalent to a voltage source connected in series with the grid impedance.

[0016] As a further improvement to this application, the method of using impedance analysis to determine the system stability of the equivalent circuit includes: Before configuring grid-type energy storage, the stability is determined by the ratio of the impedance of the power grid and the new energy power station through stability criteria based on impedance analysis. After configuring the grid-connected energy storage system, the system becomes a hybrid grid-connected / grid-connected system, integrating the first part... The second part is included in the impedance calculation of the new energy power station. As a new grid impedance, the grid-connected energy storage system is then connected in parallel with the grid as an equivalent grid; then impedance analysis is used to determine the stability of the grid-connected system.

[0017] As a further improvement to this application, the determination of the optimal capacity of the grid-type energy storage at a certain configuration location of the fixed grid-type energy storage includes: At a certain configuration location, the grid-type energy storage capacity is changed, and impedance modeling and stability analysis are performed on the hybrid grid-connected system under each capacity. When the grid-type energy storage capacity is insufficient, the new energy power station is still unstable. When the grid-type energy storage capacity is excessive, the new energy power station is stable but it will cause waste. The algorithm is used to solve the critical grid-type energy storage capacity that makes the new energy power station change from unstable to stable, that is, the minimum capacity required to suppress oscillation, as the optimal capacity to save converter costs.

[0018] As a further improvement to this application, the step of changing the configuration location and determining the globally optimal capacity and the corresponding optimal configuration location includes: By changing the configuration location of the grid-type energy storage system, S3 is repeated for the equivalent circuit model under different configuration locations to obtain the corresponding optimal capacity under that configuration location. Using the optimal capacity of grid-type energy storage at different locations as the optimization objective and the configuration location as the decision variable, the optimization algorithm is executed to obtain the global optimal capacity and the corresponding optimal configuration location of the grid-type energy storage system.

[0019] As a further improvement to this application, the specific method for determining stability using impedance analysis is as follows: the stability of the system is determined based on the Nyquist criterion.

[0020] As a further improvement of this application, the control method of the grid-type energy storage system includes any one of droop control, virtual synchronous machine control, matching control or virtual oscillator control. When different control methods are adopted, only the impedance model of the grid-type energy storage system needs to be reconstructed separately.

[0021] Secondly, this application provides a grid-type energy storage system configuration system for suppressing broadband oscillations, characterized in that the system comprises: A simplified equivalent module is used to simplify and equate the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids. The modeling and analysis module is used to perform impedance modeling on the simplified equivalent new energy power stations and grid-type energy storage systems respectively, and construct the equivalent circuit of the system; the impedance analysis method is used to determine the system stability of the equivalent circuit; The optimization configuration module is used to fix a certain configuration location of the grid-type energy storage system and determine the optimal capacity of the grid-type energy storage system at that configuration location; and to change the configuration location of the grid-type energy storage system and determine the global optimal capacity and the corresponding optimal configuration location.

[0022] Compared with the prior art, the present application has the following advantages: The present application models by retaining the complete impedance characteristics of the network-forming energy storage system, avoiding the deviation of stability judgment caused by the equivalent simplification of the prior art, providing an accurate basis for site selection and capacity determination, and ensuring the effect of broadband oscillation suppression. Relying on the network-forming energy storage system supporting the new energy power station to achieve oscillation suppression, there is no need to additionally configure equipment such as flexible AC transmission devices, nor to change the control parameters or structure of the grid-following converter, which neither affects the dynamic characteristics and performance of the original equipment nor saves additional investment costs. Through the optimization of both capacity and location dimensions, the global optimal capacity and configuration location are accurately determined, minimizing the capacity redundancy of the energy storage system to the greatest extent, significantly reducing the equipment procurement, construction and operation and maintenance costs, and greatly saving the capacity investment compared with the worst configuration plan. It is applicable to various network-forming control methods, and only needs to separately reconstruct the impedance model of the energy storage system to adapt, without reconstructing the overall system, with strong versatility and can meet the application requirements of different new energy power stations. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of a new energy power generation grid-connected system; Figure 2 It is an equivalent circuit of a new energy power generation grid-connected system; Figure 3 It is an equivalent circuit of the power grid and the network-forming energy storage system; Figure 4 It is a specific process flow chart; Figure 5 It is a schematic diagram of a simplified equivalent structure of a research case; Figure 6 It is the control structure of a new energy grid-connected converter; Figure 7 It is the control structure of a network-forming converter with virtual synchronous machine control; Figure 8 It is the electromechanical transient control structure of a virtual synchronous machine; Figure 9 It is the electromagnetic transient control structure of a virtual synchronous machine; Figure 10 It is the impedance modeling and frequency sweep results of a new energy power station; Figure 11 It is the impedance modeling and frequency sweep results of the network-forming energy storage system; Figure 12 It is the impedance ratio Nyquist diagram at different network-forming energy storage system capacities under the initial configuration location; (a) The impedance ratio Nyquist diagram when the capacity is 7.50% of the new energy power station; (b) The impedance ratio Nyquist diagram when the capacity is 8.25% of the new energy power station; Figure 13The output current and Fourier analysis results of new energy power stations with different grid-type energy storage system capacities at the initial configuration location are shown; where (a) capacity is 7.5% of the new energy power station capacity; and (b) capacity is 8.3% of the new energy power station capacity. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0025] This application employs a grid-based energy storage system to suppress broadband oscillations in renewable energy power plants, and proposes a method for configuring the capacity and location of this grid-based energy storage system. This method optimizes the configuration capacity and location of the grid-based energy storage system by performing impedance modeling on both the renewable energy power plant and the grid-based energy storage system, while ensuring effective oscillation suppression. This achieves the goal of suppressing broadband oscillations in renewable energy power plants with a minimum capacity grid-based energy storage system, thereby reducing the equipment cost required to configure the grid-based energy storage system.

[0026] This application utilizes a grid-based energy storage system to suppress broadband oscillations in renewable energy power plants. The choice of configuration capacity and location significantly impacts the cost. Insufficient capacity may fail to completely suppress broadband oscillations, while excessive capacity leads to redundancy and increased investment costs. Furthermore, a certain electrical distance often exists between the renewable energy power plant and the energy storage system; therefore, the effectiveness of the grid-based energy storage system in suppressing broadband oscillations varies depending on its location. Inappropriate location increases the required capacity, indirectly raising costs.

[0027] Therefore, this application proposes a configuration method for grid-type energy storage systems to suppress broadband oscillations. While ensuring the suppression of broadband oscillations, it avoids the waste caused by excessively large capacity design or improper configuration of the grid-type energy storage system, thus saving investment costs. The method includes the following steps: S1 simplifies and equivalences the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids; S2, impedance modeling is performed on the simplified equivalent new energy power station and grid-type energy storage system respectively to construct the system equivalent circuit; impedance analysis method is used to determine the system stability of the equivalent circuit; S3, determine the optimal capacity of the grid-type energy storage system at a fixed configuration location; S4. Change the configuration location of the grid-type energy storage to determine the global optimal capacity and the corresponding optimal configuration location.

[0028] The principle of this application is as follows: First, the complex system under actual research needs to be simplified and equivalent. Then, impedance modeling is performed on both the new energy power station and the grid-type energy storage system, and stability analysis is conducted on the system based on the corresponding stability criteria. Based on the modeling and stability analysis results, the capacity of the grid-type energy storage system at a certain configuration location is optimized to obtain the optimal capacity at that configuration location. Then, capacity optimization is performed at different configuration locations to obtain the globally optimal capacity and the corresponding optimal configuration location.

[0029] This application comprises four steps: the first step is to simplify and equivalence the actual system; the second step is to perform modeling and stability analysis; and the third and fourth steps are to optimize the location and capacity of the energy storage system.

[0030] Step 1: Simplify and make equivalent representations of the actual system being studied.

[0031] Actual research on new energy power generation grid-connected systems, such as Figure 1 As shown, the power generation equipment in the new energy power station adopts grid-connected control, while its supporting energy storage system adopts grid-connected control; both are connected to the AC power grid. It should be noted that the grid-connected energy storage system referred to in this application can refer to a single grid-connected energy storage converter or a grid-connected energy storage power station composed of multiple converters.

[0032] Real-world systems are often too complex to be analyzed directly, requiring simplification and equivalence of their components. For renewable energy power plants and energy storage systems consisting of multiple converters, they can be aggregated and equivalently represented as a single converter model. Complex AC power grids are difficult to analyze directly in terms of stability; however, simplification and equivalence can be achieved through methods such as the center of inertia method and the center of gravity method. This application does not impose specific limitations.

[0033] Optionally, the method for simplifying and equipping the AC power grid in step 1 is the center of inertia method or the center of gravity method.

[0034] Step 2: Perform impedance modeling and stability analysis on new energy power plants and grid-type energy storage systems.

[0035] When performing impedance modeling for new energy power plants and their supporting energy storage systems, impedance modeling methods such as dq impedance modeling and sequence impedance modeling can be used. After establishing the impedance models of the new energy power plants and grid-connected energy storage systems and their equivalent grid values, the system can be equivalent to... Figure 2 The circuit shown, Figure 2 This is the equivalent circuit for a new energy power generation grid-connected system; where the new energy power station is equivalent to a current source connected in parallel with its own impedance, the grid-type energy storage system can be equivalent to a voltage source connected in series with its own impedance, and the power grid is equivalent to a voltage source and an impedance connected in series.

[0036] After establishing the impedance model and equivalent circuit, stability analysis can be performed. Before configuring grid-connected energy storage, the system only consists of two parts: the renewable energy power station and the power grid. According to impedance analysis, the ratio of their impedances can be analyzed using stability criteria. After configuring the grid-connected energy storage system, the system becomes a hybrid grid-connected system, making direct impedance analysis inconvenient. Therefore, the first part... The second part is included in the impedance calculation of the new energy power station. As a new grid impedance, the grid-connected energy storage system is then connected in parallel with the grid to form an equivalent grid, such as... Figure 3 As shown. Then, the stability of the hybrid system of root and network can be determined by using the same impedance analysis method.

[0037] Optionally, the impedance modeling method in step 2 can be either dq impedance modeling or sequence impedance modeling. When using sequence impedance modeling, frequency coupling effects are considered and the equivalent positive and negative sequence impedances are obtained by reducing the order.

[0038] The specific method for determining stability using impedance analysis in step 2 is as follows: based on the Nyquist criterion, the system stability is determined by judging whether the impedance ratio curve encircles the point (-1, j0).

[0039] Step 3: Determine the optimal capacity of the grid-type energy storage system at a given configuration location.

[0040] The optimization process for capacity and location can be viewed as a nested loop process, as follows: Figure 4 As shown. Under a certain configuration location, by changing the grid-type energy storage capacity, impedance modeling and stability analysis of the hybrid grid-connected system under each capacity are performed for S2. When the grid-type energy storage capacity is insufficient, the new energy power station is still unstable. When the grid-type energy storage capacity is excessive, the new energy power station is stable but it will cause waste. An algorithm is used to solve for the critical grid-type energy storage capacity that makes the new energy power station change from unstable to stable as the optimal capacity to save converter costs.

[0041] Optionally, the solution algorithm described in step 3 can be a traversal method, a binary search method, or other search algorithms.

[0042] Step 4: Determine the optimal location for the grid-type energy storage system.

[0043] By changing the configuration location of the grid-type energy storage system, step S3 is repeated for the equivalent circuit model at different configuration locations to obtain the corresponding optimal capacity. Using the optimal capacity at different locations as the optimization objective and the configuration location as the decision variable, an optimization algorithm is executed to obtain the global optimal capacity and the corresponding optimal configuration location of the grid-type energy storage system.

[0044] Optionally, the optimization algorithm described in step 4 is a heuristic algorithm such as traversal method, genetic algorithm, or particle swarm optimization.

[0045] In step 4, the different configuration positions are characterized by the division ratio of the total impedance of the power grid, and the configuration positions are traversed by the division ratio in a step size of 0.05~0.1.

[0046] The control methods of the grid-type energy storage system include any one of droop control, virtual synchronous machine control, matching control, or virtual oscillator control. When different control methods are used, only the impedance model of the grid-type energy storage system needs to be reconstructed separately.

[0047] The broadband oscillation includes subsynchronous oscillation or supersynchronous oscillation, and the new energy power station is a photovoltaic power station or a wind power station.

[0048] Below are specific implementation examples of the strategy proposed in this application: This application is applicable to broadband oscillation problems in new energy power plants such as photovoltaic and wind power. Taking photovoltaic power generation as an example, after configuring grid-type energy storage, the simplified equivalent system structure is as follows: Figure 5 As shown, Figure 5 A simplified equivalent structure diagram is provided for this case study. The photovoltaic grid-connected converter employs grid-following control on the grid side, while the energy storage converter uses grid-connected control; both utilize LCL-type filters. Due to the electrical distance between the AC grid and the renewable energy plant, a certain grid impedance exists between the renewable energy source and the equivalent grid. The grid-connected energy storage system is positioned somewhere between the renewable energy plant and the grid. This application is applicable to various types of broadband oscillations in renewable energy grid-following converters. This case study investigates one typical broadband oscillation: subsynchronous / supersynchronous oscillations caused by the interaction between the weakening grid impedance due to changes in grid impedance and the negative damping generated by the grid-following converter control structure.

[0049] 1. Control strategy for grid-connected converters for new energy sources, as detailed below: The control of grid-connected converters in renewable energy power plants includes generator-side control and grid-side control. Generator-side control is generally used to track the maximum power output of the renewable energy source, while grid-side control adopts grid-following control to maintain DC-side power balance and grid connection. Because the DC bus capacitor is generally large and voltage fluctuations are small, under fixed operating conditions, their generator-side control and the upstream converter can be considered equivalent to a single current source. Their grid-side control uses grid-following control, such as... Figure 6 As shown, it includes DC voltage outer loop control, current inner loop control and phase-locked loop. First, by sampling the capacitor voltage and transforming it into coordinates, the phase angle can be obtained by inputting it into the phase-locked loop to achieve synchronization with the power grid. Then, the DC voltage loop controls the DC bus voltage and power balance.

[0050] Figure 6 This is the control structure for a grid-connected converter for new energy sources. (See diagram.) This represents the DC bus capacitor voltage; The magnitude of the equivalent DC current source of the preceding converter; , and These are the filter inductor and filter capacitor of an LCL filter, respectively. For grid impedance; The capacitor voltage is given in a three-phase stationary coordinate system. The capacitor voltage in a synchronously rotating coordinate system; The grid voltage is in a three-phase stationary coordinate system. Filter inductor in a three-phase stationary coordinate system Current on; For the filter inductor in the synchronous rotating coordinate system Current on; This serves as the d-axis current reference. The grid-connected converter is synchronized with the power grid via a phase-locked loop (PLL). This case uses the most common three-phase synchronous PLL. and It outputs the phase angle and angular frequency.

[0051] 2. The energy storage system control strategy is as follows: The energy storage system employs grid-based control, and there are currently many types of grid-based control methods, including droop control, virtual synchronous machine control, and matched control. This case study utilizes virtual synchronous machine control, a widely used method in academia. It simulates the electromechanical transient characteristics of a synchronous generator to provide frequency and inertia support for the system, and simulates the electromagnetic transient characteristics of a synchronous generator to provide voltage support. Its control structure is as follows: Figure 7 As shown. However, it should be noted that this application is not limited to virtual synchronous machine control, but is also applicable to various network-based control methods. It is only necessary to establish their respective impedance models and then perform system stability analysis.

[0052] Figure 7 The diagram shows the control structure of a virtual synchronous machine-controlled grid-type converter: The capacitor voltage is given in a three-phase stationary coordinate system. The grid-side filter inductor in a three-phase stationary coordinate system Current on; Filter inductor in a three-phase stationary coordinate system The current on the grid is calculated. First, the virtual synchronous machine acquires the output capacitor voltage and grid-side current signal, and obtains the real-time output power of the system through the power calculation module. Second, the virtual angular frequency and phase angle can be obtained by simulating the governor equation and rotor oscillation equation of the synchronous generator through electromechanical transient simulation. Finally, the electromotive force is obtained by simulating the electromagnetic transient of the synchronous machine, and the reference voltage of the inverter modulation wave is further obtained.

[0053] Among them, the electromechanical transient control section, such as Figure 8The diagram shows the electromechanical transient control structure of a virtual synchronous machine. For the damping element in the virtual synchronous machine control, a state feedback-based damping design method is adopted. This not only improves the system's damping ratio but also offers advantages over previous methods, such as better dynamic characteristics and stronger harmonic suppression.

[0054] The electromagnetic transient control structure adopts the voltage and current dual closed-loop control, which is widely used in academia. Its control structure is as follows: Figure 9 As shown, the electromotive force reference value is first obtained through the reactive voltage droop relationship, and then the coordinate transformation is performed by combining the virtual phase angle obtained by electromechanical transient control. The inverter modulation wave reference voltage is generated through the voltage and current controller and the virtual impedance link.

[0055] Specific implementation process one: Simplifying and equipping the actual system In practical systems, multiple converters in new energy power plants and grid-based energy storage systems are simplified and aggregated into an equivalent single converter. For complex AC power grids, the center of inertia method and Thevenin circuit simplification are employed.

[0056] Specific implementation process two: Establish impedance models for new energy power plants and grid-type energy storage systems and conduct stability analysis. First, impedance modeling was performed on both new energy power plants and grid-connected energy storage systems, and verified through frequency sweep. This application is applicable to different impedance modeling methods. In this case, the sequence impedance modeling method is used, which avoids the synchronization problem of different coordinate systems in the dq impedance analysis method. Furthermore, its applicability to black-box models makes it a more engineering-significant method. During sequence impedance modeling, the impact of frequency coupling effects must be considered, which is more pronounced under weak grid conditions. After considering the frequency coupling effect, equivalent positive and negative sequence impedances can be obtained by order reduction to reduce computational load. Then, the Nyquist criterion can be used to determine system stability.

[0057] Specific implementation process three: Determining the optimal capacity of the grid-type energy storage system required to suppress oscillations. To determine the optimal capacity of a grid-connected energy storage system required to suppress oscillations, this application is applicable to various solution algorithms. In this case, an ergonomic method is used, which is simple in principle and easy to implement. First, the capacity of the grid-connected energy storage system is initialized to zero. Then, at the initial configuration location, the capacity of the grid-connected energy storage system is gradually increased in steps of 0.25% of the site capacity. This process is repeated to model the system and obtain the sequence impedance model of the grid-connected energy storage system under the new capacity. Finally, a stability analysis is performed on the hybrid grid-connected system based on the Nyquist criterion. If the system changes from unstable to stable, the capacity of the grid-connected energy storage system at this point is the minimum capacity required to suppress oscillations, i.e., the optimal capacity.

[0058] Specific implementation process four: Determining the optimal location for configuring the grid-type energy storage system This application applies to various optimization methods for optimizing the configuration location of grid-based energy storage systems. In this case, a traversal method is used, which is simple in principle and easy to implement. When changing the configuration location of the grid-based energy storage system, the total grid impedance is divided into two parts, which can be addressed by... This is used to represent different configuration locations. At this point, the configuration locations are traversed with a step size of 0.1. Under each configuration location, the optimal capacity under that location is obtained according to the method in process three. After the traversal is completed, the optimal configuration location and configuration capacity of the grid-type energy storage system can be obtained by comparison.

[0059] Based on the above scheme, the simulation results are analyzed as follows: First, impedance modeling and frequency sweep verification were performed on both new energy power plants and grid-based energy storage systems. Figure 10 and Figure 11 As shown. It should be noted that... Figure 10 and Figure 11 The equivalent positive and negative sequence impedances are obtained after considering the frequency coupling effect, rather than the positive and negative sequence impedances without considering the frequency coupling effect. In the figure, the solid line represents the theoretical modeling result, and the discrete points represent the results obtained by impedance frequency sweep. As can be seen from the figure, each discrete point falls accurately on the solid line, that is, the impedance frequency sweep result matches the theoretical modeling result well, verifying the accuracy of the theoretical modeling result.

[0060] At the initial configuration location, the impedance ratio Nyquist plots for different grid-type energy storage system capacities, obtained from the impedance model, are as follows: Figure 12 As shown in the figure, (a) is the Nyquist plot of impedance ratio when the capacity is 7.50% of the new energy power station capacity; (b) is the Nyquist plot of impedance ratio when the capacity is 8.25% of the new energy power station capacity. It can be seen from the figure that when the capacity of the grid-type energy storage system changes from 7.5% to 8.25% of the new energy power station capacity, the Nyquist curve does not encircle the point (-1, j0), and the system changes from unstable to stable. This indicates that the optimal capacity required to suppress oscillations at the initial position is only 8.25% of the power station capacity.

[0061] The output current of new energy power stations and their Fourier analysis results under different grid-type energy storage system capacities obtained from the simulation are as follows: Figure 13 As shown in the figure, (a) represents 7.5% of the capacity of the new energy power station, and (b) represents 8.3% of the capacity of the new energy power station. It can be seen from the figure that when the capacity of the grid-type energy storage system changes from 7.50% to 8.25% of the capacity of the new energy power station, the oscillation phenomenon of the new energy power station disappears, which is consistent with the theoretical analysis results.

[0062] Table 1 shows the optimal capacity of the grid-type energy storage system required to suppress oscillations, obtained by repeating process three at different configuration locations. As can be seen from the table, when the grid-type energy storage system is located close to the renewable energy power station, the optimal capacity required to suppress oscillations remains at a low level and first decreases and then increases with distance. When the configuration location is far from the renewable energy power station, the minimum capacity required to suppress oscillations increases significantly with increasing distance. At the optimal configuration location (… A grid-type energy storage system that requires only 7.5% of the site's capacity can suppress its broadband oscillation, saving 84.5% of the capacity compared to the worst-case configuration, thus saving investment costs.

[0063] Table 1. Optimal capacity of grid-type energy storage system required to suppress oscillations at different locations.

[0064] This application can be implemented on a single computer and requires a memory, a processor, and a computer program to implement the various processes of this application. When the processor executes the computer program, it performs a process of optimizing the allocation of capacity and location. The memory is used to store the program and its output data results. The computer program includes a simplified equivalent module, a modeling and analysis module, and an optimization module.

[0065] Simplified equivalent module: For complex real-world systems, the program uses a corresponding simplification method to simplify the new energy power plant, energy storage system, and AC power grid. The parameters of each simplified part are saved for subsequent modeling and analysis.

[0066] Modeling and Analysis Module: For a grid-type energy storage system with a specific configuration location and capacity, impedance modeling is performed on both the new energy power station and the grid-type energy storage system using an impedance modeling program stored on the computer's available hard drive, and the model is stored in memory. Then, a stability analysis program is used to obtain the stability analysis results for that configuration capacity and location, and these results are also saved in memory.

[0067] Optimization Configuration Module: This module optimizes the location and capacity of grid-type energy storage configurations using an optimization program stored on the computer's available hard drive. It continuously calls modeling and stability analysis programs, storing the optimal capacity results in memory. After optimization, the globally optimal capacity and its corresponding configuration location are saved as the optimal capacity and location.

[0068] The specific explanation is as follows: The second objective of this application is to provide a grid-type energy storage system configuration system for suppressing broadband oscillations, which implements the above-mentioned grid-type energy storage system configuration method for suppressing broadband oscillations. The system includes: A simplified equivalent module is used to simplify and equate the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids. The modeling and analysis module is used to perform impedance modeling on the simplified equivalent new energy power stations and grid-type energy storage systems respectively, and construct the equivalent circuit of the system; the impedance analysis method is used to determine the system stability of the equivalent circuit; The optimization configuration module is used to fix a certain configuration location of the grid-type energy storage system and determine the optimal capacity of the grid-type energy storage system at that configuration location; and to change the configuration location of the grid-type energy storage system and determine the global optimal capacity and the corresponding optimal configuration location.

[0069] A third objective of this application is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the aforementioned configuration method for a grid-type energy storage system that suppresses broadband oscillations. The device also includes a communication interface and a bus.

[0070] The fourth objective of this application is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for configuring a grid-type energy storage system to suppress broadband oscillations.

[0071] A fifth objective of this application is to provide a computer program product comprising computer instructions that instruct a computer to execute the above-described method for configuring a grid-type energy storage system to suppress broadband oscillations.

[0072] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0073] These computer program instructions can also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0074] This application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, readable storage media, optical storage, etc.) containing computer-usable program code.

[0075] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0076] Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation methods of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of this application.

Claims

1. A method for configuring a grid-type energy storage system to suppress broadband oscillations, characterized in that, Includes the following steps: S1 simplifies and equivalences the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids; S2, impedance modeling is performed on the simplified equivalent new energy power station and grid-type energy storage system respectively to construct the system equivalent circuit; impedance analysis method is used to determine the system stability of the equivalent circuit; S3, determine the optimal capacity of the grid-type energy storage system at a fixed configuration location; S4. Change the configuration location of the grid-type energy storage system to determine the global optimal capacity and the corresponding optimal configuration location.

2. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The simplified equivalent of the actual system including grid-connected control renewable energy power plants, grid-connected energy storage systems, and AC power grids includes: The multiple grid-connected converters in the new energy power station are aggregated and equivalent to a single grid-connected converter model, and the multiple grid-connected converters in the grid-connected energy storage system are aggregated and equivalent to a single grid-connected converter model, thus simplifying and equipping the AC power grid.

3. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The impedance modeling method is either the dq impedance modeling method or the sequence impedance modeling method. When using sequence impedance modeling, the frequency coupling effect is considered and the equivalent positive and negative sequence impedances are obtained by reducing the order.

4. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The process involves impedance modeling of the simplified equivalent new energy power stations and grid-type energy storage systems to construct the system equivalent circuit, including: When performing impedance modeling for new energy power plants and grid-type energy storage systems, dq impedance modeling or sequence impedance modeling methods are adopted to preserve the complete impedance characteristics of the grid-type energy storage system. After establishing the impedance models of new energy power plants and grid-type energy storage systems and their equivalents with the power grid, the new energy power plant is equivalent to a current source connected in parallel with its own impedance, the grid-type energy storage system is equivalent to a voltage source connected in series with its own impedance, and the power grid is equivalent to a voltage source connected in series with the grid impedance.

5. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The method of determining system stability using impedance analysis of the equivalent circuit includes: Before configuring grid-type energy storage, the stability is determined by the ratio of the impedance of the power grid and the new energy power station through stability criteria based on impedance analysis. After configuring the grid-connected energy storage system, the system becomes a hybrid grid-connected / grid-connected system, integrating the first part... The second part is included in the impedance calculation of the new energy power station. As a new grid impedance, the grid-connected energy storage system is then connected in parallel with the grid as an equivalent grid; then impedance analysis is used to determine the stability of the grid-connected system.

6. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The fixed grid-type energy storage system is configured at a specific location, and the optimal capacity of the grid-type energy storage system at that location is determined; including: At a certain configuration location, the grid-type energy storage capacity is changed, and impedance modeling and stability analysis are performed on the hybrid grid-connected system under each capacity. When the grid-type energy storage capacity is insufficient, the new energy power station is still unstable. When the grid-type energy storage capacity is excessive, the new energy power station is stable but it will cause waste. The algorithm is used to solve the critical grid-type energy storage capacity that makes the new energy power station change from unstable to stable, that is, the minimum capacity required to suppress oscillation, as the optimal capacity to save converter costs.

7. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The process of changing the configuration location to determine the globally optimal capacity and the corresponding optimal configuration location includes: By changing the configuration location of the grid-type energy storage system, S3 is repeated for the equivalent circuit model under different configuration locations to obtain the corresponding optimal capacity under that configuration location. Using the optimal capacity of grid-type energy storage at different locations as the optimization objective and the configuration location as the decision variable, the optimization algorithm is executed to obtain the global optimal capacity and the corresponding optimal configuration location of the grid-type energy storage system.

8. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The specific method for determining stability using impedance analysis is as follows: determine system stability based on the Nyquist criterion.

9. The method for configuring a grid-type energy storage system to suppress broadband oscillations according to claim 1, characterized in that, The control methods of the grid-type energy storage system include any one of droop control, virtual synchronous machine control, matching control, or virtual oscillator control. When different control methods are used, only the impedance model of the grid-type energy storage system needs to be reconstructed separately.

10. A grid-type energy storage system for suppressing broadband oscillations, characterized in that, include: A simplified equivalent module is used to simplify and equate the actual system including grid-connected control new energy power stations, grid-type energy storage systems and AC power grids. The modeling and analysis module is used to perform impedance modeling on the simplified equivalent new energy power stations and grid-type energy storage systems respectively, and construct the equivalent circuit of the system; the impedance analysis method is used to determine the system stability of the equivalent circuit; The optimization configuration module is used to fix a certain configuration location of the grid-type energy storage system and determine the optimal capacity of the grid-type energy storage system at that configuration location; and to change the configuration location of the grid-type energy storage system and determine the global optimal capacity and the corresponding optimal configuration location.

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