A method and system for grid-forming energy storage inertia regulation

Abstract

The present application relates to the technical field of energy storage grid-connected control, and discloses a grid-connected energy storage inertia regulation method and system, comprising the following steps: determining a grid-connected point frequency deviation based on frequency sampling values, and determining a frequency disturbance phase of a photovoltaic power station grid-connected point based on the grid-connected point frequency deviation and a grid-connected point frequency change rate; determining inertia regulation constraint information of grid-connected energy storage participating in inertia support; determining target virtual inertia parameters and target virtual damping parameters; inputting the target virtual inertia parameters and the target virtual damping parameters into a virtual synchronous machine control loop of the grid-connected energy storage, generating an active power support instruction, and adjusting active output of the grid-connected energy storage. The present scheme can enable the grid-connected energy storage to dynamically adjust virtual inertia and virtual damping according to a photovoltaic weak grid frequency disturbance phase and available support capacity of the grid-connected energy storage, thereby improving frequency active support effect and reducing active response tailing in the recovery phase.

Description

Technical Field

[0001] This invention relates to the field of energy storage grid connection control technology, and in particular to a method and system for adjusting the inertia of grid-connected energy storage. Background Technology

[0002] As the scale of centralized photovoltaic (PV) power plants continues to increase, some PV sites located at the end of the grid or in areas with weak transmission channels are no longer just power generation units, but directly affect the frequency stability of the local power grid. Especially in weak grid scenarios with high altitudes, long transmission lines, and low short-circuit capacity, PV output is easily affected by factors such as cloud cover, the lifting of power curtailment, and power ramp-up control, leading to rapid changes in active power output within a short period. Due to insufficient synchronous power support in these areas and the low inertia of the grid itself, the grid connection frequency is highly sensitive to active power disturbances. Rapid changes in PV output may cause accelerated frequency drift, thereby affecting the grid connection stability and transmission capacity of the PV sites.

[0003] In existing grid-connected energy storage control systems, grid-connected energy storage typically relies on grid voltage and frequency signals for operation, primarily serving as a peak-shaving, power smoothing, or frequency regulation auxiliary agent. It struggles to proactively provide voltage and frequency support during the initial stages of weak grid disturbances. While grid-connected energy storage can provide virtual inertia and damping through virtual synchronous machine control, in engineering applications, the virtual inertia parameter is often set to a fixed value or simply adjusted based on frequency deviation. This approach provides some support under normal operating conditions, but it remains insufficient in weak photovoltaic grid scenarios.

[0004] Specifically, when photovoltaic output declines rapidly and causes the frequency to continue deviating from the rated frequency, grid-connected energy storage needs to promptly increase its inertia support capability to slow down the frequency change rate. However, when the frequency has already entered the recovery process, maintaining a high virtual inertia can easily lead to a trailing effect in the active power response of the energy storage, thus affecting the frequency recovery speed. Furthermore, the energy storage itself is limited by the State of Charge (SOC), converter output boundaries, and the current active power output state. Blindly increasing the virtual inertia parameter without considering available support margins may consume subsequent frequency regulation margins or even trigger power limiting. Therefore, there is an urgent need for a grid-connected energy storage inertia adjustment method for photovoltaic power plants in weak grid scenarios, enabling the virtual inertia and virtual damping to be rationally adjusted according to the frequency disturbance stage and the energy storage support capability. Summary of the Invention

[0005] This invention provides a method and system for adjusting the inertia of grid-connected energy storage, aiming to solve at least one of the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides a method for adjusting the inertia of grid-connected energy storage, comprising the following steps: Acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of frequency at the grid connection point, the change in photovoltaic active power output, and the operational status data of grid-type energy storage. The frequency deviation at the grid connection point is determined based on the frequency sampling value, and the frequency disturbance stage at the grid connection point of the photovoltaic power station is determined based on the frequency deviation at the grid connection point and the frequency change rate at the grid connection point. Based on the changes in photovoltaic active power output and the operating status data of the grid-type energy storage, the inertia adjustment constraint information for grid-type energy storage to participate in inertia support is determined. Based on the frequency disturbance stage and the inertia adjustment constraint information, the target virtual inertia parameter and the target virtual damping parameter are determined. The target virtual inertia parameter and the target virtual damping parameter are input into the virtual synchronous machine control loop of the grid-type energy storage to generate an active power support command, and the active power output of the grid-type energy storage is adjusted based on the active power support command.

[0007] Furthermore, to achieve the above objectives, the present invention also provides a grid-based energy storage inertia regulation system, comprising: The data acquisition module is used to acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of the grid connection point frequency, the change of photovoltaic active power output, and the operating status data of the grid-type energy storage. The first processing module is used to determine the grid connection point frequency deviation based on the frequency sampling value, and to determine the frequency disturbance stage of the photovoltaic power station grid connection point based on the grid connection point frequency deviation and the grid connection point frequency change rate. The second processing module is used to determine the inertia adjustment constraint information for grid-type energy storage to participate in inertia support based on the change in photovoltaic active power output and the operating status data of the grid-type energy storage. The parameter generation module is used to determine the target virtual inertia parameter and the target virtual damping parameter based on the frequency disturbance stage and the inertia adjustment constraint information; The adjustment module is used to input the target virtual inertia parameter and the target virtual damping parameter into the virtual synchronous machine control loop of the grid-type energy storage, generate active power support command, and adjust the active power output of the grid-type energy storage based on the active power support command.

[0008] The beneficial effects of this invention are as follows: by integrating the frequency changes at the grid connection point of the photovoltaic power plant, the changes in photovoltaic active power output, and the operating status of the grid-connected energy storage itself into the inertia adjustment process, it is possible to first determine whether the frequency disturbance is in a state of continued deviation, recovery, or stability, and then limit the virtual inertia adjustment range by combining the photovoltaic power output disturbance and the available support capacity of the energy storage. This avoids insufficient support from the grid-connected energy storage in the early stage of the disturbance, and also avoids maintaining an excessively high virtual inertia during the frequency recovery phase, which would result in active power response tailing. By inputting the target virtual inertia parameters and the target virtual damping parameters into the virtual synchronous machine control loop, the active power output of the energy storage can be made to better match the photovoltaic weak grid disturbance process, improving the active frequency support capability at the grid connection point while reducing the occupation of the subsequent frequency regulation margin and operating boundary of the energy storage. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the device structure of the hardware operating environment involved in the embodiments of the present invention; Figure 2 This is a flowchart illustrating an embodiment of the grid-connected energy storage inertia adjustment method of the present invention; Figure 3 This is a timing diagram of the frequency disturbance stage at the grid connection point of the photovoltaic power plant according to the present invention; Figure 4 This is a flowchart illustrating the inertia adjustment constraint information generation process of the present invention. Figure 5 This is a structural block diagram of a grid-based energy storage inertia regulation system according to an embodiment of the present invention. Detailed Implementation

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0011] like Figure 1 As shown, Figure 1 This is a schematic diagram of the device structure of the hardware operating environment involved in the embodiments of the present invention.

[0012] like Figure 1 As shown, the device may include: a processor 1001, such as a CPU; a communication bus 1002; a user interface 1003; a network interface 1004; and a memory 1005. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0013] Those skilled in the art will understand that Figure 1 The structure of the device shown does not constitute a limitation on the device and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0014] like Figure 1As shown, the memory 1005, which serves as a computer storage medium, may include an acquisition module, a first processing module, a second processing module, a parameter generation module, an adjustment module, and a grid energy storage inertia adjustment program.

[0015] exist Figure 1 In the terminal shown, network interface 1004 is mainly used to connect to the backend server and communicate with it; user interface 1003 is mainly used to connect to the client (user terminal) and communicate with it; while processor 1001 can be used to call the network energy storage inertia adjustment program stored in memory 1005. Acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of frequency at the grid connection point, the change in photovoltaic active power output, and the operational status data of grid-type energy storage. The frequency deviation at the grid connection point is determined based on the frequency sampling value, and the frequency disturbance stage at the grid connection point of the photovoltaic power station is determined based on the frequency deviation at the grid connection point and the frequency change rate at the grid connection point. Based on the changes in photovoltaic active power output and the operating status data of the grid-type energy storage, the inertia adjustment constraint information for grid-type energy storage to participate in inertia support is determined. Based on the frequency disturbance stage and the inertia adjustment constraint information, the target virtual inertia parameter and the target virtual damping parameter are determined. The target virtual inertia parameter and the target virtual damping parameter are input into the virtual synchronous machine control loop of the grid-type energy storage to generate an active power support command, and the active power output of the grid-type energy storage is adjusted based on the active power support command.

[0016] This invention provides a method for adjusting the inertia of grid-connected energy storage, referring to... Figure 2 , Figure 2 This is a schematic flowchart illustrating an embodiment of the grid-based energy storage inertia adjustment method of the present invention.

[0017] In this embodiment, a method for adjusting the inertia of grid-connected energy storage includes the following steps: S100: Acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of the grid connection point frequency, the change of photovoltaic active power output, and the operating status data of grid-type energy storage.

[0018] S200: Determine the grid connection point frequency deviation based on the frequency sampling value, and determine the frequency disturbance stage of the photovoltaic power station grid connection point based on the grid connection point frequency deviation and the grid connection point frequency change rate.

[0019] S300: Based on the changes in photovoltaic active power output and the operating status data of the grid-type energy storage, determine the inertia adjustment constraint information for grid-type energy storage to participate in inertia support.

[0020] S400: Based on the frequency disturbance stage and the inertia adjustment constraint information, determine the target virtual inertia parameter and the target virtual damping parameter.

[0021] S500: Input the target virtual inertia parameter and the target virtual damping parameter into the virtual synchronous machine control loop of the grid-type energy storage, generate an active power support command, and adjust the active power output of the grid-type energy storage based on the active power support command.

[0022] Specifically, step S100 includes acquiring the frequency sampling value of the photovoltaic power station's grid connection point, the rate of change of the grid connection point frequency, the change in photovoltaic active power output, and the operating status data of the grid-type energy storage.

[0023] In practical implementation, a frequency measurement unit is configured at the grid connection point of the photovoltaic power station to collect the grid connection point voltage signal according to a preset sampling period, and the frequency sample value is obtained by phase-locked loop calculation or frequency measurement algorithm. The rate of change of the grid connection point frequency can be obtained by the difference of the frequency sample values ​​in adjacent sampling periods, or it can be directly output by the frequency detection link inside the station monitoring system or the grid-type energy storage controller. The data format should be able to reflect the direction of change of the grid connection point frequency, whether it is increasing or decreasing.

[0024] The change in photovoltaic (PV) active power output can be calculated based on the collected power of the PV inverter or the active power on the PV side at the grid connection point. For example, the difference between the PV active power output at the current sampling time and the PV active power output at the previous sampling time or the previous control cycle is calculated to obtain the change in PV active power output with increasing or decreasing directions. This data is used to reflect the impact of PV output on grid connection point frequency disturbances during cloud shadowing, power curtailment removal, or power ramp-up processes.

[0025] The operational status data of grid-based energy storage can be provided by energy storage management devices, converter controllers, or battery management devices, and at least includes data characterizing the current active power regulation capability of the grid-based energy storage. Preferably, the operational status data of the grid-based energy storage includes the current active power output of the grid-based energy storage, the energy storage SOC, and the allowable active power output boundary of the converter. After time alignment, the above data forms an input data set within the same control cycle, which is used by subsequent steps to determine the grid connection point frequency deviation, frequency disturbance stage, and inertia regulation constraint information.

[0026] Specifically, step S200 includes determining the grid connection point frequency deviation based on the frequency sampling value, including: obtaining the rated frequency value corresponding to the grid connection point of the photovoltaic power station; calculating the difference between the frequency sampling value and the rated frequency value to obtain the grid connection point frequency deviation with the deviation direction.

[0027] Determining the frequency disturbance stage of the grid connection point of a photovoltaic power plant based on the grid connection point frequency deviation and the grid connection point frequency change rate includes: comparing the grid connection point frequency deviation with a preset frequency deviation threshold and comparing the grid connection point frequency change rate with a preset frequency change rate threshold; if the grid connection point frequency deviation exceeds the preset frequency deviation threshold and the grid connection point frequency change rate indicates that the grid connection point frequency continues to deviate from the rated frequency value, then the frequency disturbance stage is determined to be the disturbance leading edge stage; if the grid connection point frequency deviation exceeds the preset frequency deviation threshold and the grid connection point frequency change rate indicates that the grid connection point frequency recovers to the rated frequency value, then the frequency disturbance stage is determined to be the frequency recovery stage; if the grid connection point frequency deviation does not exceed the preset frequency deviation threshold and the grid connection point frequency change rate does not exceed the preset frequency change rate threshold, then the frequency disturbance stage is determined to be the stable maintenance stage.

[0028] Step S200 is used to determine whether the current grid connection point frequency is in a state of deepening disturbance, disturbance recovery, or stable maintenance, based on the frequency sampling value and grid connection point frequency change rate obtained in step S100. This step does not directly generate energy storage active power commands, but rather provides a stage basis for the selection of subsequent virtual inertia parameters and virtual damping parameters, enabling grid-type energy storage to adopt different support methods during different frequency changes.

[0029] In one embodiment, the rated frequency value corresponding to the grid connection point of the photovoltaic power station is first obtained. This rated frequency value can be the standard grid frequency value or the grid connection point operating reference frequency value issued by the dispatching side. Taking my country's conventional AC power grid as an example, the rated frequency value can be taken as 50Hz. The frequency sampling value obtained within the current control cycle is recorded as... The rated frequency value is recorded as The frequency deviation at the grid connection point can then be expressed as: ; in, This refers to the frequency deviation at the grid connection point with a deviated direction. When When, it indicates that the grid connection point frequency is higher than the rated frequency value; when When the frequency at the grid connection point is lower than the rated frequency, it indicates that the frequency is lower than the rated frequency. This deviation direction is of practical significance in subsequent judgments because the direction of active power regulation of energy storage is different for frequency increases and frequency decreases, and cannot be replaced by the absolute value of the deviation alone.

[0030] After obtaining the grid connection point frequency deviation, the frequency deviation is compared with a preset frequency deviation threshold, and the rate of change of the grid connection point frequency is compared with a preset rate of change threshold. To avoid ambiguity caused by positive or negative directions, the absolute value of the frequency deviation and the absolute value of the rate of change of the grid connection point frequency can be compared with the preset frequency deviation threshold, respectively. The preset frequency deviation threshold and the preset rate of change threshold can be preset based on the grid connection point short-circuit capacity, photovoltaic power station installed capacity, grid-connected energy storage rated capacity, and grid dispatch assessment requirements, or they can be adjusted under different operating seasons or different grid connection methods.

[0031] When the frequency deviation at the grid connection point exceeds the preset frequency deviation threshold, and the rate of change of the grid connection point frequency indicates that the grid connection point frequency is continuing to move away from the rated frequency value, the frequency disturbance stage is determined to be the disturbance leading edge stage. In engineering implementation, this can be achieved through... Make a judgment.

[0032] like and This indicates that the frequency is below the rated frequency value and is still decreasing; if and This indicates that the frequency is higher than the rated frequency and is still rising. Both of these situations indicate that the frequency deviation is deepening, and grid-type energy storage will need to have a faster inertia support response in the future.

[0033] When the frequency deviation at the grid connection point exceeds the preset frequency deviation threshold, but the rate of change of the grid connection point frequency indicates that the grid connection point frequency is recovering to the rated frequency value, the frequency disturbance stage is determined to be the frequency recovery stage. This state can be determined by... This is confirmed by checking if the frequency deviation still exceeds the threshold. At this point, the frequency has not yet returned to the allowable range, but the deviation trend has weakened. Subsequent control is more suitable for reducing the excessive virtual inertia and suppressing the swing back through virtual damping, so as to avoid excessive delay in the recovery process of the energy storage active power output.

[0034] When the frequency deviation at the grid connection point does not exceed the preset frequency deviation threshold, and the rate of change of the grid connection point frequency does not exceed the preset rate of change threshold, the frequency disturbance stage is determined to be a stable maintenance stage. This stage indicates that the grid connection point frequency is within an acceptable stable range, and subsequent steps can maintain the virtual inertia parameter and virtual damping parameter at the baseline state, avoiding frequent adjustments of control parameters due to small fluctuations in grid-type energy storage.

[0035] In one possible implementation, Figure 3The process of frequency change at the grid connection point of a photovoltaic power plant over time is shown. Stage A is the disturbance leading edge stage, where the frequency deviation exceeds the threshold and the frequency continues to deviate from the rated frequency value; Stage B is the frequency recovery stage, where the frequency deviation still exceeds the threshold, but the direction of frequency change has pointed to the rated frequency value; Stage C is the stable maintenance stage, where both the frequency deviation and the frequency change rate are within the allowable range.

[0036] In other implementations, when a photovoltaic power station is located at the end of a weak grid, the voltage phase may experience a brief jump within several control cycles after a line fault is cleared. The frequency measurement unit may easily misidentify the phase recovery process as a rapid frequency change, causing the frequency disturbance phase to be misjudged as the disturbance leading edge phase. To avoid this problem, before calculating the grid connection point frequency deviation, the effective value of the grid connection point voltage is read, and it is determined whether the effective value of the grid connection point voltage is lower than the low voltage ride-through trigger value within the previous preset time window.

[0037] If a low-voltage ride-through occurs, the frequency sample values ​​will be continuously verified within the preset recovery window after the fault is cleared. Only when the frequency sample values ​​of two adjacent sampling periods change in the same direction, and the effective value of the grid connection point voltage has recovered to the preset voltage recovery range, will the frequency sample value be allowed to participate in the test. and Calculation. If the above conditions are not met, within the invalid frequency sampling period, the frequency disturbance stage corresponding to the control cycle that has most recently passed the continuity check and voltage recovery check is called as the frequency disturbance stage of the current control cycle. This embodiment can avoid the phase jump interference of the inertia adjustment judgment at the moment of fault clearing, so that the grid-type energy storage will not prematurely increase the virtual inertia parameter due to the measurement of false disturbances.

[0038] Specifically, step S300 includes determining inertia adjustment constraint information for grid-type energy storage to participate in inertia support based on the change in photovoltaic active power output and the operating status data of the grid-type energy storage. This includes: comparing the change in photovoltaic active power output with a preset photovoltaic output change threshold to determine the photovoltaic output disturbance state; determining the active power adjustment margin of the grid-type energy storage that can be used for inertia support based on the operating status data of the grid-type energy storage; and determining the inertia adjustment constraint information for grid-type energy storage to participate in inertia support based on the photovoltaic output disturbance state and the active power adjustment margin. The inertia adjustment constraint information is used to limit the adjustment range of the target virtual inertia parameter.

[0039] Based on the operational status data of the grid-type energy storage, the active power regulation margin that the grid-type energy storage can use for inertia support is determined, including: extracting the current active power output of the grid-type energy storage, the energy storage SOC, and the converter's allowable active power output boundary from the operational status data of the grid-type energy storage; determining the SOC constraint boundary for the grid-type energy storage to participate in inertia support based on the energy storage SOC; and determining the active power regulation margin that the grid-type energy storage can use for inertia support based on the converter's allowable active power output boundary, the SOC constraint boundary, and the current active power output of the grid-type energy storage.

[0040] Step S300, based on the obtained frequency disturbance stage, further determines whether grid-connected energy storage is suitable for increasing the virtual inertia parameter, and what limitations should be placed on the increase. Since frequency disturbances at the grid connection point of a photovoltaic power plant may be related to rapid changes in photovoltaic output, or may originate from external grid or load-side disturbances, if the photovoltaic output disturbance state is not distinguished, grid-connected energy storage can easily enter a strong inertia support state unnecessarily. On the other hand, when grid-connected energy storage participates in inertia support, it needs to release or absorb active power, and its capability is constrained by the current active power output, energy storage SOC, and converter output boundary. Therefore, step S300 does not directly generate virtual inertia parameters, but first forms inertia adjustment constraint information as the boundary condition for step S400 to determine the target virtual inertia parameter.

[0041] In one embodiment, such as Figure 4 The change in photovoltaic active power output is denoted as The preset photovoltaic output change threshold is denoted as .when When the photovoltaic output disturbance state is determined to be an effective disturbance state, it indicates that the active power on the photovoltaic side has undergone a change sufficient to affect the frequency of the weak grid within the current control cycle. If If the photovoltaic output disturbance state is determined to be an ineffective disturbance state, the subsequent inertia adjustment constraint information should not allow a significant increase in the target virtual inertia parameter. The preset photovoltaic output change threshold can be adjusted according to the installed capacity of the photovoltaic power station, the short-circuit capacity at the grid connection point, and the rated power of the grid-type energy storage. For example, for a large-capacity centralized photovoltaic power station, it can be set according to a certain proportion of the rated photovoltaic active power capacity, or it can be set according to the measured power ramp-up characteristics of the station.

[0042] Grid-based energy storage can be used for active power regulation margins supported by inertia, which can be further obtained from the operating status data of grid-based energy storage. In specific implementation, the current active power output, energy storage SOC, and allowable active power output boundary of the converter are extracted from the operating status data of the grid-based energy storage. The current active power output of the grid-based energy storage is denoted as... Its positive and negative directions can be determined according to the station control agreement. The allowable active power output boundary of the converter includes the upper boundary of the allowable discharge power and the lower boundary of the allowable charging power, denoted as , respectively. and .in, Used to limit the maximum capacity of grid-connected energy storage to increase active power output to the grid connection point. Used to limit the maximum active power absorption capacity of grid-type energy storage.

[0043] The State of Charge (SOC) of energy storage is used to determine whether the battery side is allowed to continue releasing or absorbing energy. The SOC constraint boundary for grid-type energy storage participating in inertia support can be determined based on the energy storage SOC. For example, when the energy storage SOC is close to the preset lower limit, the inertia support capability in the discharge direction should be limited; when the energy storage SOC is close to the preset upper limit, the inertia support capability in the charging direction should be limited. To facilitate controller execution, the SOC constraint boundary can be converted into the SOC allowable power boundary, denoted as... and This conversion can be performed using a lookup table or directly determined based on the allowable charge and discharge power output by the battery management device. The specific method does not affect the implementation of this embodiment.

[0044] After determining the allowable active power output boundary and SOC constraint boundary of the converter, the active power regulation margin is calculated based on the current active power output of the grid-type energy storage. For frequency drop scenarios requiring increased discharge support, the following can be taken: ; in, This indicates the active power regulation margin for grid-type energy storage in the discharge direction that can be used for inertia support. For frequency-increased scenarios requiring reduced output or absorbed power, the following can be taken: ; in, This indicates the active power regulation margin of grid-type energy storage that can be used for inertia support in the charging direction. The above expression is used to illustrate an executable calculation method. In actual engineering, it can also be rewritten into an equivalent form according to the sign convention of converter power, as long as it can reflect the adjustable space between the current active power output of grid-type energy storage and the allowable active power output boundary.

[0045] After obtaining the photovoltaic output disturbance state and active power regulation margin, inertia regulation constraint information is generated. This inertia regulation constraint information is used to limit the adjustment range of the target virtual inertia parameter. Preferably, when the photovoltaic output disturbance state is an effective disturbance state, and the active power regulation margin in the corresponding power direction is greater than a preset support margin threshold, the inertia regulation constraint information allows the target virtual inertia parameter to be increased to a larger support value in step S400. When the photovoltaic output disturbance state is an effective disturbance state, but the active power regulation margin is insufficient, the inertia regulation constraint information only allows the target virtual inertia parameter to increase slightly, or limits it to not exceeding a preset intermediate inertia value. When the photovoltaic output disturbance state is an ineffective disturbance state, the inertia regulation constraint information can limit the target virtual inertia parameter to remain near a reference virtual inertia parameter. Through this process, step S300 simultaneously transforms the photovoltaic-side disturbance intensity and the available support capacity on the energy storage side into constraints for subsequent parameter selection, ensuring that the virtual inertia adjustment does not deviate from the actual output changes of the photovoltaic power station, nor does it exceed the operating boundary of the grid-type energy storage itself.

[0046] Specifically, in step S400, the process of determining the target virtual inertia parameter includes: when the frequency disturbance stage is the disturbance leading edge stage and the inertia adjustment constraint information allows for an increase in the virtual inertia parameter, adjusting the reference virtual inertia parameter to the target virtual inertia parameter according to a preset inertia increase range; when the frequency disturbance stage is the frequency recovery stage, adjusting the target virtual inertia parameter to a level lower than the recovery virtual inertia parameter of the disturbance leading edge stage; when the frequency disturbance stage is the stable maintenance stage, or when the inertia adjustment constraint information does not allow for an increase in the virtual inertia parameter, determining the target virtual inertia parameter as the reference virtual inertia parameter.

[0047] The virtual inertia parameter is used to determine the strength of active power support for grid-type energy storage in the early stages of frequency changes. This parameter is not suitable to remain fixed throughout the entire disturbance process; otherwise, it will provide insufficient support when the frequency deviates rapidly and may cause active power response tailing when the frequency returns to normal. Therefore, in this embodiment, the virtual inertia parameter is determined in segments according to the disturbance development state.

[0048] Let the reference virtual inertia parameter be denoted as The preset inertia increase is recorded as When the frequency disturbance stage is the leading edge of the disturbance, and the inertia adjustment constraint information allows for an increase in the virtual inertia parameter, it indicates that the grid connection point frequency is continuing to move away from the rated frequency value, while the grid-type energy storage still has an active power adjustment margin that can be used for inertia support. At this time, the target virtual inertia parameter can be determined as: ; in, This represents the target virtual inertia parameter. The preset inertia increase range can be pre-set according to the short-circuit capacity of the photovoltaic power station's grid connection point, the rated power of the grid-type energy storage, and the allowable active power regulation margin, or it can be selected by looking up a table. If the inertia regulation constraint information provides multiple allowable regulation levels, The corresponding increase can be selected for different levels.

[0049] When the frequency disturbance stage is the frequency recovery stage, it indicates that the frequency deviation at the grid connection point has not been completely eliminated, but the direction of frequency change has already pointed towards the rated frequency value. Maintaining a high virtual inertia at this time, similar to the disturbance leading edge stage, will cause the energy storage active power output to maintain a strong inertial response, which is detrimental to subsequent damping control takeover. Therefore, the recovered virtual inertia parameter, which is lower than the virtual inertia parameter corresponding to the disturbance leading edge stage, can be determined as the target virtual inertia parameter. For example, the recovered virtual inertia parameter can be denoted as... and satisfy When the frequency recovers quickly or the active power regulation margin is low, It can also be taken directly as .

[0050] When the frequency disturbance phase is a stable maintenance phase, or when the inertia adjustment constraint information does not allow for an increase in the virtual inertia parameter, the target virtual inertia parameter is determined as the reference virtual inertia parameter. This process ensures that when the grid-connected energy storage is in a stable frequency range at the grid connection point, or when the energy storage SOC and converter output boundaries are not suitable for continuing to release support capacity, the virtual inertia parameter will no longer be increased, thus maintaining the control parameters consistent with the actual support capacity of the energy storage.

[0051] In other embodiments, during actual operation, photovoltaic power plants may experience a rapid increase in power output after the lifting of dispatch restrictions. At this time, the grid connection frequency may rise briefly. The inertia support direction of grid-connected energy storage should be biased towards absorbing active power, rather than releasing it. To avoid errors in direction due to relying solely on the total active power margin of energy storage, the inertia support direction can be determined based on the positive and negative directions of the change in photovoltaic active power output and the direction of the grid connection frequency deviation when determining the active power regulation margin.

[0052] when and When the charging direction margin is available, it is used as the active power adjustment margin; when and In this case, the available margin in the discharge direction is used as the active power regulation margin. If the direction of change in photovoltaic active power output is inconsistent with the direction of frequency deviation at the grid connection point, the inertia regulation constraint information is limited to not allowing the virtual inertia parameter to be increased. This embodiment enables the inertia regulation constraint information to simultaneously reflect the intensity of photovoltaic disturbance and the support direction, avoiding the output direction of grid-connected energy storage being opposite to the frequency suppression direction during the rapid ramp-up of photovoltaic power or the recovery of power rationing.

[0053] Specifically, in step S400, the process of determining the target virtual damping parameter includes: when the frequency disturbance stage is the disturbance leading edge stage, determining the target virtual damping parameter as the leading edge virtual damping parameter that matches the target virtual inertia parameter; when the frequency disturbance stage is the frequency recovery stage, adjusting the reference virtual damping parameter to the target virtual damping parameter according to a preset damping increase magnitude; and when the frequency disturbance stage is the stable maintenance stage, determining the target virtual damping parameter as the reference virtual damping parameter.

[0054] Let the benchmark virtual damping parameter be denoted as When the frequency disturbance stage is the disturbance leading edge stage, it indicates that the grid connection point frequency is continuing to deviate from the rated frequency value. At this time, the target virtual inertia parameter has usually been increased to the value of the leading edge support. To avoid active power output oscillation caused by the rapid increase of the inertia support power component, the target virtual damping parameter can be determined as the leading edge virtual damping parameter that matches the target virtual inertia parameter. The leading edge virtual damping parameter can be selected through a preset parameter table or determined according to the level of the target virtual inertia parameter. For example, when the target virtual inertia parameter is At that time, the leading-edge virtual damping parameters can be selected. This allows energy storage to maintain a controllable output slope while increasing active power support.

[0055] When the frequency disturbance stage is the frequency recovery stage, the frequency deviation still exists, but the direction of frequency change has already pointed towards the rated frequency value. This stage focuses more on the smoothness of the frequency recovery process. The reference virtual damping parameter can be adjusted to the target virtual damping parameter according to a preset damping increase, specifically expressed as: ; in, Indicates the target virtual damping parameter. This indicates the preset damping increase. By increasing the virtual damping parameter during the recovery phase, grid-type energy storage can more quickly reduce the remaining support corresponding to the frequency deviation when calculating active power support commands, thus reducing sway when the frequency approaches the rated frequency value.

[0056] When the frequency disturbance phase is a stable maintenance phase, the target virtual damping parameter is determined as the reference virtual damping parameter. This setting is suitable when both the grid connection point frequency deviation and the grid connection point frequency change rate are within the allowable range, allowing the virtual synchronous machine control loop to maintain normal damping characteristics and preventing grid-type energy storage from frequently increasing damping parameters due to small frequency fluctuations.

[0057] The above-mentioned method for determining the target virtual damping parameters can be performed synchronously with the target virtual inertia parameters, or it can be performed after the target virtual inertia parameters are determined, as long as the target virtual inertia parameters and target virtual damping parameters ultimately input into the virtual synchronous machine control loop correspond to the same frequency disturbance stage.

[0058] Specifically, in step S500, the target virtual inertia parameter and the target virtual damping parameter are input into the virtual synchronous machine control loop of the grid-type energy storage to generate an active power support command. This includes: calculating the inertia support power component and the damping support power component of the grid-type energy storage based on the target virtual inertia parameter, the target virtual damping parameter, the grid connection point frequency deviation, and the grid connection point frequency change rate; performing inverse superposition of the inertia support power component and the damping support power component to obtain the active power support setpoint of the virtual synchronous machine control loop; and generating an active power support command based on the active power support setpoint and the current active power output of the grid-type energy storage.

[0059] The calculation rule for the inertia support power component is as follows: ; The calculation rule for the damping support power component is as follows: ; in, Indicates the inertia-supporting power component; Indicates the damping support power component; Indicates the target virtual inertia parameter; Indicates the target virtual damping parameters; Indicates the frequency deviation at the grid connection point; Indicates the rate of change of the frequency of grid connection points; Indicating the inertia support correction factor for discrimination: .

[0060] When the virtual synchronous machine control loop performs active power support, it needs to consider both the frequency change rate and the frequency deviation itself. The frequency change rate reflects how fast the disturbance is developing, while the frequency deviation reflects the degree to which the grid connection point frequency has deviated from the rated frequency value. In this embodiment, these two are respectively introduced into the inertia support power component and the damping support power component, making the source of the control quantity clearer and facilitating subsequent limiting and distribution.

[0061] In one embodiment, the inertia support power component is calculated according to the following formula: ; The power component of the damping support is calculated according to the following formula: ; in, This represents the inertia-supporting power component. Indicates the damping support power component. Represents the target virtual inertia parameter. Indicates the target virtual damping parameter. Indicates the frequency deviation at the grid connection point. This represents the rate of change of the grid connection point frequency. The aforementioned grid connection point frequency deviation can be obtained from step S200. The frequency change rate at the grid connection point can be obtained by using the frequency difference between adjacent control cycles, or by using the change rate data output by the frequency detection stage.

[0062] Inertia support correction factor Used to determine whether the current inertia support needs to be strengthened, its value can satisfy: ; in, This represents the preset frequency deviation correction coefficient. When... At this time, it indicates that the direction of the frequency deviation at the grid connection point is consistent with the direction of frequency change, and the frequency continues to move away from the rated frequency value. At this time, through... Amplifying the inertia-supported power component enables grid-type energy storage to generate active power support more quickly during the disturbance front stage. When the frequency has stopped deviating from the rated frequency value, or when the recovery process has begun, the inertia support correction factor is taken as the reference value to avoid further amplification of the inertia response during the recovery phase.

[0063] Based on the inertia-supported power component and the damping-supported power component, the sum of the two can be reversed to obtain the active power setpoint of the virtual synchronous machine control loop: ; When using this symbol convention, if the grid connection point frequency is lower than the rated frequency value and continues to decrease, then , Calculated A positive value indicates that grid-type energy storage requires increased active power output; if the grid connection point frequency is higher than the rated frequency and continues to rise, then... A negative value indicates that the grid-type energy storage needs to reduce its active power output or absorb active power. Subsequently, based on the current active power output of the grid-type energy storage, the active power support setpoint is converted into an active power support command that can be executed on the converter side, and then sent to the power control loop of the grid-type energy storage according to the control cycle.

[0064] In another embodiment, when grid-based energy storage performs inertia support in a weak grid scenario, if the frequency change rate fluctuates significantly in a short period of time, the inertia support power component... Rapid and continuous changes can cause high-frequency fluctuations in the converter's active power output command. Especially in areas with strong winds, sandstorms, and high cloud speeds, photovoltaic output can fluctuate multiple times within seconds. If directly relying on instantaneous data... Calculating the power component supported by inertia can easily cause frequent fluctuations in the active power output of energy storage.

[0065] Therefore, after generating the active power support setpoint, the slope of change of the inertial support power component is also limited. Specifically, the inertial support power component corresponding to the previous control cycle is read. And calculate the inertia support power component of the current control cycle. and The change between the values; if the change per unit time exceeds the preset inertia power change rate threshold, then the current inertia support power component is limited and corrected according to the preset inertia power change rate threshold before participating in the calculation of the subsequent active power support setpoint. This embodiment can reduce the amplification effect of frequency measurement perturbations and short-term photovoltaic power fluctuations on the active power output command of energy storage, enabling grid-type energy storage to maintain a relatively stable active power support change process during continuous frequency disturbances.

[0066] In one application example, a 250MW centralized photovoltaic power station at high altitude is used as an example. The photovoltaic power station is equipped with a 50MW / 100MWh grid-connected energy storage system, and the photovoltaic power station is connected to a weak grid via a 220kV line. Assume the rated frequency value... The preset frequency deviation threshold is 50Hz. The preset frequency change rate threshold is 0.03Hz. The preset threshold for photovoltaic power output variation is 0.08 Hz / s. The capacity is 8MW. During a certain control period, cloud cover caused the active power output of the photovoltaic system to decrease from 182MW to 168MW. The sampling frequency at the grid connection point decreased from 49.98Hz to 49.94Hz, and the calculated values ​​were... , .because ,and We have determined that the current stage is the disturbance frontier.

[0067] At this point, the active power output of the grid-type energy storage is 6MW, the energy storage SOC is 58%, and the converter's allowable discharge limit is 50MW. Based on the SOC constraint boundary and the converter output boundary, the active power regulation margin in the discharge direction is calculated to be 38MW, which meets the inertia support requirements. The controller adjusts the reference virtual inertia parameter from 4.0 to 6.5 and sets the target virtual damping parameter to the matching leading-edge virtual damping parameter. Approximately 3 seconds later, the frequency sampling value rises to 49.96Hz. , , Switching to the frequency recovery phase, the target virtual inertia parameter is adjusted to 4.8, and the target virtual damping parameter is increased to the recovery damping parameter to reduce active response tailing.

[0068] Reference Figure 5 , Figure 5 This is a structural block diagram of an embodiment of the grid-connected energy storage inertia regulation system of the present invention.

[0069] like Figure 5 As shown, the grid-connected energy storage inertia regulation system proposed in this embodiment of the invention includes: The data acquisition module is used to acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of the grid connection point frequency, the change of photovoltaic active power output, and the operating status data of the grid-type energy storage. The first processing module is used to determine the grid connection point frequency deviation based on the frequency sampling value, and to determine the frequency disturbance stage of the photovoltaic power station grid connection point based on the grid connection point frequency deviation and the grid connection point frequency change rate. The second processing module is used to determine the inertia adjustment constraint information for grid-type energy storage to participate in inertia support based on the change in photovoltaic active power output and the operating status data of the grid-type energy storage. The parameter generation module is used to determine the target virtual inertia parameter and the target virtual damping parameter based on the frequency disturbance stage and the inertia adjustment constraint information; The adjustment module is used to input the target virtual inertia parameter and the target virtual damping parameter into the virtual synchronous machine control loop of the grid-type energy storage, generate active power support command, and adjust the active power output of the grid-type energy storage based on the active power support command.

[0070] Other embodiments or specific implementations of the grid-connected energy storage inertia regulation system of the present invention can be referred to the above-described method embodiments, and will not be repeated here.

[0071] It is understood that in the description of this specification, references to terms such as "one embodiment," "another embodiment," "other embodiments," or "first embodiment to Nth embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0073] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0074] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0075] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for regulating the inertia of grid-connected energy storage, characterized in that, Includes the following steps: Acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of frequency at the grid connection point, the change in photovoltaic active power output, and the operational status data of grid-type energy storage. The frequency deviation at the grid connection point is determined based on the frequency sampling value, and the frequency disturbance stage at the grid connection point of the photovoltaic power station is determined based on the frequency deviation at the grid connection point and the frequency change rate at the grid connection point. Based on the changes in photovoltaic active power output and the operating status data of the grid-type energy storage, the inertia adjustment constraint information for grid-type energy storage to participate in inertia support is determined. Based on the frequency disturbance stage and the inertia adjustment constraint information, the target virtual inertia parameter and the target virtual damping parameter are determined. The target virtual inertia parameter and the target virtual damping parameter are input into the virtual synchronous machine control loop of the grid-type energy storage to generate an active power support command, and the active power output of the grid-type energy storage is adjusted based on the active power support command.

2. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, Determining the grid connection point frequency deviation based on the frequency sampled values ​​includes: Obtain the rated frequency value corresponding to the grid connection point of the photovoltaic power station; The difference between the frequency sample value and the rated frequency value is calculated to obtain the grid connection point frequency deviation with the deviation direction.

3. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, The frequency disturbance stage of the photovoltaic power plant's grid connection point is determined based on the grid connection point frequency deviation and the grid connection point frequency change rate, including: The frequency deviation at the grid connection point is compared with a preset frequency deviation threshold, and the frequency change rate at the grid connection point is compared with a preset frequency change rate threshold. If the frequency deviation at the grid connection point exceeds the preset frequency deviation threshold, and the frequency change rate at the grid connection point indicates that the frequency at the grid connection point continues to deviate from the rated frequency value, then the frequency disturbance stage is determined to be the disturbance leading edge stage. If the frequency deviation at the grid connection point exceeds the preset frequency deviation threshold, and the frequency change rate at the grid connection point represents the recovery of the grid connection point frequency to the rated frequency value, then the frequency disturbance stage is determined to be the frequency recovery stage. If the frequency deviation at the grid connection point does not exceed the preset frequency deviation threshold, and the frequency change rate at the grid connection point does not exceed the preset frequency change rate threshold, then the frequency disturbance stage is determined to be a stable maintenance stage.

4. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, Based on the changes in photovoltaic active power output and the operational status data of the grid-type energy storage, the inertia regulation constraint information for grid-type energy storage to participate in inertia support is determined, including: The photovoltaic active power output change is compared with a preset photovoltaic power output change threshold to determine the photovoltaic power output disturbance state. Based on the operational status data of the grid-type energy storage, the active power regulation margin that the grid-type energy storage can be used for inertia support is determined. Based on the photovoltaic output disturbance state and the active power regulation margin, the inertia regulation constraint information for grid-type energy storage to participate in inertia support is determined. The inertia regulation constraint information is used to limit the adjustment range of the target virtual inertia parameter.

5. The method for adjusting the inertia of grid-connected energy storage as described in claim 4, characterized in that, Based on the operational status data of the grid-type energy storage, the active power regulation margin that the grid-type energy storage can use for inertia support is determined, including: Extract the current active power output, energy storage SOC, and converter allowable active power output boundary from the network-type energy storage operation status data; Based on the aforementioned energy storage SOC, determine the SOC constraint boundary for grid-type energy storage participating in inertia support; Based on the converter's allowed active power output boundary, the SOC constraint boundary, and the current active power output of the grid-type energy storage, the active power regulation margin that the grid-type energy storage can use for inertia support is determined.

6. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, The process of determining the target virtual inertia parameters includes: When the frequency disturbance stage is the disturbance leading edge stage, and the inertia adjustment constraint information allows for an increase in the virtual inertia parameter, the reference virtual inertia parameter is adjusted to the target virtual inertia parameter according to the preset inertia increase range. When the frequency disturbance phase is the frequency recovery phase, the target virtual inertia parameter is adjusted to be lower than the recovery virtual inertia parameter of the disturbance leading edge phase; When the frequency disturbance phase is a stable maintenance phase, or when the inertia adjustment constraint information does not allow for an increase in the virtual inertia parameter, the target virtual inertia parameter is determined as the reference virtual inertia parameter.

7. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, The process of determining the target virtual damping parameters includes: When the frequency disturbance stage is the disturbance leading edge stage, the target virtual damping parameter is determined as the leading edge virtual damping parameter that matches the target virtual inertia parameter; When the frequency disturbance phase is the frequency recovery phase, the reference virtual damping parameter is adjusted to the target virtual damping parameter according to the preset damping increase magnitude; When the frequency disturbance phase is a stable maintenance phase, the target virtual damping parameter is determined as the reference virtual damping parameter.

8. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, The target virtual inertia parameters and the target virtual damping parameters are input into the virtual synchronous machine control loop of the grid-type energy storage system to generate active power support commands, including: Based on the target virtual inertia parameter, the target virtual damping parameter, the grid connection point frequency deviation and the grid connection point frequency change rate, the inertia support power component and the damping support power component of the grid-type energy storage are calculated. The active power setpoint of the virtual synchronous machine control loop is obtained by superimposing the inertia support power component and the damping support power component in reverse. Based on the given active power support value and the current active power output of the grid-type energy storage, an active power support command is generated.

9. The method for adjusting the inertia of grid-connected energy storage as described in claim 1, characterized in that, The calculation rule for the inertia support power component is as follows: ； The calculation rule for the damping support power component is as follows: ； in, Indicates the inertia-supporting power component; Indicates the damping support power component; Indicates the target virtual inertia parameter; Indicates the target virtual damping parameters; Indicates the frequency deviation at the grid connection point; Indicates the rate of change of the frequency of grid connection points; Indicating the inertia support correction factor for discrimination: 。 10. A grid-connected energy storage inertia regulation system, characterized in that, The system includes: The data acquisition module is used to acquire frequency sampling values ​​at the grid connection point of the photovoltaic power plant, the rate of change of the grid connection point frequency, the change of photovoltaic active power output, and the operating status data of the grid-type energy storage. The first processing module is used to determine the grid connection point frequency deviation based on the frequency sampling value, and to determine the frequency disturbance stage of the photovoltaic power station grid connection point based on the grid connection point frequency deviation and the grid connection point frequency change rate. The second processing module is used to determine the inertia adjustment constraint information for grid-type energy storage to participate in inertia support based on the change in photovoltaic active power output and the operating status data of the grid-type energy storage. The parameter generation module is used to determine the target virtual inertia parameter and the target virtual damping parameter based on the frequency disturbance stage and the inertia adjustment constraint information; The adjustment module is used to input the target virtual inertia parameters and the target virtual damping parameters into the virtual synchronous machine control loop of the grid-type energy storage, generate active power support commands, and adjust the active power output of the grid-type energy storage based on the active power support commands.

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