A power coordination control method for improving voltage stability of a power grid by energy storage

Abstract

This invention discloses a power coordination control method for improving grid voltage stability through energy storage, comprising the following steps: collecting state variables related to voltage stability; constructing an optimized solution model for active and reactive power output based on the state variables, with the target being the maximum load-side node voltage or the maximum load-side node voltage increase; obtaining the optimal active and reactive power command values ​​based on the optimized solution model, and adjusting the active and reactive power output command values ​​of the energy storage; and after the load-side voltage recovers to the target range, controlling the energy storage device to gradually withdraw its support output and switch to steady-state operation. This invention adaptively evaluates the dominant factors based on line resistance, reactance, and power distribution, thereby dynamically determining the power distribution of the energy storage and achieving optimal coordinated support between the two. This invention requires fewer measurements and has clear control logic, effectively improving the recovery speed of the load-side voltage under sudden disturbances and significantly enhancing the system's operational stability.

Description

Technical Field

[0001] This invention belongs to the field of power system stability control and energy storage converter control technology, specifically relating to a power coordination control method for improving grid voltage stability through energy storage. Background Technology

[0002] In distribution networks, microgrids, and local power grids with a high proportion of renewable energy, load-side node voltages are prone to fluctuations due to factors such as load changes, line voltage drops, and local power imbalances. Especially in scenarios where the power grid transmits power to the load via lines, load-side node voltages are more likely to drop when the load's active and reactive power demands increase, the transmission distance is long, or the line impedance is high. In severe cases, this can affect power quality and reduce system operational stability.

[0003] To address the aforementioned issues, various methods for energy storage to participate in voltage support have been proposed in existing technologies. For grid-connected energy storage devices, regardless of whether a grid-connected or grid-linked control method is used, they can support node voltage by adjusting their output power. Therefore, existing research typically focuses on the impact of energy storage control modes, control parameters, connection location, and output characteristics on voltage stability, and further analyzes coordinated control methods for energy storage to participate in voltage support.

[0004] One type of method primarily focuses on the effect of reactive power output from energy storage on node voltage support. This typically involves establishing voltage-reactive power sensitivity relationships, VQ characteristic relationships, or Jacobian matrix mapping relationships to analyze the impact of energy storage and reactive power compensation devices at different locations on voltage recovery capabilities. This type of method is well-suited for grid reactance-dominant applications, but when line resistance cannot be ignored, or when there is a significant active component in load disturbances, relying solely on reactive power regulation often fails to achieve optimal voltage support. Another type of method considers the joint regulation of active and reactive power from energy storage. This involves constructing a voltage-power characteristic model incorporating the energy storage system to study the impact of active and reactive power output from energy storage on voltage stability, thereby improving the flexibility of voltage support. However, existing joint regulation methods often focus on empirical selection of the support direction under given operating conditions, or are based on specific network parameter conditions and simplified assumptions. They still lack a unified and clear approach to determining the optimal active and reactive power allocation ratio under limited energy storage capacity, and to avoiding consistently full energy storage output when voltage deviations are small.

[0005] In addition, some existing methods rely on complex mode switching, hierarchical allocation, or additional constraint processing. Although they are suitable for more complex scenarios, they often have problems such as complicated implementation logic and unintuitive parameter tuning in the initial engineering applications.

[0006] Therefore, it is still necessary to propose a simple and clear energy storage power coordination control method to find the active-reactive power distribution relationship that maximizes the load-side node voltage under the given total energy storage output, and to determine the actual support amount based on the target voltage within the upper limit of the available apparent power of energy storage, so as to give full play to the voltage support capability of energy storage. Summary of the Invention

[0007] This invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a power coordination control method for improving grid voltage stability through energy storage.

[0008] The technical solution of this invention is: a power coordination control method for improving grid voltage stability through energy storage, comprising the following steps: A. Collect state variables related to voltage stability; B. With the goal of maximizing the load-side node voltage or the load-side node voltage increase, construct an optimization solution model for active and reactive power output based on the state variables. C. Obtain the optimal active and reactive power command values ​​based on the optimization solution model, and adjust the active and reactive power output command values ​​of energy storage. D. After the load-side voltage recovers to the target range, control the energy storage device to gradually withdraw its support output and switch to steady-state operation mode.

[0009] Furthermore, the state variables in step A include the line resistance and reactance between the grid side and the energy storage, and the active and reactive power transmitted from the energy storage node to the load-side node.

[0010] Furthermore, step B also includes a constraint that is performed under the upper limit constraint of the apparent power of energy storage.

[0011] Furthermore, energy storage is connected to the load-side node or a node near the load in parallel; the energy storage device is controlled by a grid-connected converter or adopts a grid-connected operation mode.

[0012] Furthermore, in step B, an optimization model for active and reactive power outputs is constructed based on the state variables. The specific process is as follows: The relationship model is a functional relationship model of the load-side node voltage with respect to the active and reactive power outputs of energy storage. With the apparent power output of energy storage as the constraint and the load-side node voltage amplitude as the optimization objective, the optimization solution model is as follows: ; in, This represents the voltage amplitude at the load-side node. and These are the active power and reactive power outputs of the energy storage system. S To store energy and output apparent power, This represents the maximum energy storage capacity.

[0013] Furthermore, step C involves obtaining the optimal active and reactive power command values ​​based on the optimization solution model. The specific process is as follows: Solving the optimization model yields the optimal active and reactive power output values ​​for energy storage: ; in, and These are the line resistance, reactance, and impedance modulus between the grid-side node and the energy storage node. and These are the active power and reactive power transmitted from the energy storage node to the load-side node, respectively.

[0014] Furthermore, in step D, after the load-side voltage recovers to the target range, the active and reactive power outputs of the energy storage are gradually reduced according to the preset slope in step C, and then restored to the steady-state set value.

[0015] The technical features of this invention are as follows: This invention addresses the scenario of effectively utilizing energy storage to provide voltage support for load-side nodes. It establishes a relationship model between load-side node voltage and the active and reactive power outputs of energy storage. Under energy storage capacity constraints, and with the objective of maximizing load-side node voltage, it constructs an optimization model for the active and reactive power outputs of energy storage. Unlike existing control methods that select priority for reactive or active power support based on empirical rules, this invention calculates the optimal active-reactive power allocation ratio that maximizes the load-side node voltage given the total energy storage output. Furthermore, without exceeding the upper limit of the available apparent power of energy storage, it generates active and reactive power output commands based on this optimal allocation ratio.

[0016] The method of this invention operates on the energy storage power command allocation layer, and is applicable to both energy storage devices connected to the grid using a grid-based control method and energy storage devices connected to the grid using a grid-following control method. It features a clear model, well-defined objectives, and a wide range of applications.

[0017] The beneficial effects of this invention are as follows: Compared with existing control methods that use fixed reactive power compensation or fixed ratio active and reactive power distribution, this invention can adaptively select a more suitable energy storage support direction based on different line impedance conditions and different load disturbance types, thereby improving the pertinence and effectiveness of load-side voltage support.

[0018] This invention does not pre-limit the control method of energy storage, and can be applied to grid-connected and grid-linked energy storage systems. It requires fewer measurements and has clear control logic, making it easy to promote and apply in distribution networks, microgrids, and local systems with a high proportion of new energy sources. It plays a positive role in improving the voltage recovery speed on the load side, suppressing voltage deviation, and enhancing the stability of system operation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system for boosting load-side node voltage through energy storage in the embodiment; Figure 2 This is a comparison diagram between the method described in this embodiment and the scheme that only outputs reactive power. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments: like Figures 1 to 2 As shown, a power coordination control method for improving grid voltage stability through energy storage includes the following steps: A. Collect state variables related to voltage stability; B. With the goal of maximizing the load-side node voltage or the load-side node voltage increase, construct an optimization solution model for active and reactive power output based on the state variables. C. Obtain the optimal active and reactive power command values ​​based on the optimization solution model, and adjust the active and reactive power output command values ​​of energy storage. D. After the load-side voltage recovers to the target range, control the energy storage device to gradually withdraw its support output and switch to steady-state operation mode.

[0021] The state variables in step A include the line resistance and reactance between the grid side and the energy storage, and the active and reactive power transmitted from the energy storage node to the load-side node.

[0022] Step B also includes a constraint that is performed under the upper limit constraint of the apparent power of energy storage.

[0023] Energy storage is connected to load-side nodes or nodes near the load in parallel; the energy storage device is controlled by a grid-connected converter or adopts a grid-connected operation mode.

[0024] In step B, an optimization model for active and reactive power output is constructed based on the state variables. The specific process is as follows: The relationship model is a functional relationship model of the load-side node voltage with respect to the active and reactive power outputs of energy storage. With the apparent power output of energy storage as the constraint and the load-side node voltage amplitude as the optimization objective, the optimization solution model is as follows: ; in, This represents the voltage amplitude at the load-side node. and These are the active power and reactive power outputs of the energy storage system. S To store energy and output apparent power, This represents the maximum energy storage capacity.

[0025] Step C involves obtaining the optimal active and reactive power command values ​​based on the optimization solution model. The specific process is as follows: Solving the optimization model yields the optimal active and reactive power output values ​​for energy storage: ; in, and These are the line resistance, reactance, and impedance modulus between the grid-side node and the energy storage node. and These are the active power and reactive power transmitted from the energy storage node to the load-side node, respectively.

[0026] In step D, after the load-side voltage recovers to the target range, the active and reactive power outputs of the energy storage are gradually reduced according to the preset slope in step C, and then restored to the steady-state set value.

[0027] Specifically, the line impedance characteristic information in step A is used to characterize the strength of the influence of line resistance and line reactance on node voltage. This information can be obtained by offline parameter tuning or configured in the controller before operation. Example

[0028] The present invention will be further described below with reference to the accompanying drawings and specific simulation examples, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] This embodiment is built on the MATLAB / Simulink platform as follows: Figure 1 The power grid-energy storage-load system model shown.

[0030] In the above system, the power grid transmits power to the load side through the lines, and the energy storage device is connected in parallel near the load-side node to provide voltage support when the voltage drops due to load disturbances.

[0031] The main system parameters used in this embodiment are shown in Table 1. Voltage level and capacity parameters are expressed as actual values, while other electrical and operational parameters are expressed as per-unit values.

[0032] In the initial stage of the simulation, the system is in a stable operating state. At simulation time t=0.5s, the active power demand and reactive power demand on the load side are simultaneously increased to 3MW and 3Mvar, respectively. Due to the sudden increase in load, the load-side node voltage drops rapidly to 0.805 pu. At simulation time t=1.0s, two sets of comparison conditions are set: Firstly, in comparison condition 1: the energy storage system only outputs reactive power, providing pure reactive voltage support to the load-side nodes.

[0033] Secondly, in comparison condition 2: the energy storage system uses the optimal active-reactive power distribution ratio proposed in this patent to output active and reactive power to provide coordinated support for the load-side nodes.

[0034] Simulation results of load-side node voltage waveforms under two operating conditions are as follows: Figure 2 As shown, Figure 2 The red curve represents operating condition 1, with a total reactive power output of 1 p.u.; the blue curve represents operating condition 2, with active and reactive power outputs of 0.71 p.u. and 0.71 p.u., respectively. Figure 2 It is evident that after a load disturbance occurs, if energy storage only outputs reactive power, although it can raise the voltage of the load-side node to a certain extent, its voltage recovery effect is limited under the current line impedance and load disturbance conditions. However, by adopting the optimal active-reactive power distribution ratio proposed in this patent, energy storage can more effectively utilize the synergistic effect of active and reactive power support under the same apparent power constraint conditions, enabling the load-side node voltage to achieve a faster and higher recovery effect.

[0035] This embodiment demonstrates that the energy storage power coordination control method proposed in this invention can determine the optimal allocation and actual total support of active and reactive power output of energy storage based on the load-side node voltage improvement target under the condition of limited apparent energy storage power. Compared with the method of only using reactive power support, it can more effectively improve the load-side node voltage recovery capability and improve the system operation stability.

Claims

1. A power coordination control method for improving power grid voltage stability by energy storage, characterized in that: Includes the following steps: A. Collect state variables related to voltage stability; B. With the goal of maximizing the load-side node voltage or the load-side node voltage increase, construct an optimization solution model for active and reactive power output based on the state variables. C. Obtain the optimal active and reactive power command values ​​based on the optimization solution model, and adjust the active and reactive power output command values ​​of energy storage. D. After the load-side voltage recovers to the target range, control the energy storage device to gradually withdraw its support output and switch to steady-state operation mode.

2. The power coordination control method for improving grid voltage stability through energy storage according to claim 1, characterized in that: The state variables in step A include the line resistance and reactance between the grid side and the energy storage, and the active and reactive power transmitted from the energy storage node to the load-side node.

3. The power coordination control method for improving grid voltage stability through energy storage according to claim 1, characterized in that: Step B also includes a constraint that is performed under the upper limit constraint of the apparent power of energy storage.

4. The power coordination control method for improving grid voltage stability through energy storage according to claim 2, characterized in that: Energy storage is connected to load-side nodes or nodes near the load in parallel; the energy storage device is controlled by a grid-connected converter or adopts a grid-connected operation mode.

5. The power coordination control method for improving grid voltage stability through energy storage according to claim 1, characterized in that: In step B, an optimization model for active and reactive power output is constructed based on the state variables. The specific process is as follows: The relationship model is a functional relationship model of the load-side node voltage with respect to the active and reactive power outputs of energy storage. With the apparent power output of energy storage as the constraint and the load-side node voltage amplitude as the optimization objective, the optimization solution model is as follows: ； in, This represents the voltage amplitude at the load-side node. and These are the active power and reactive power outputs of the energy storage system. S To store energy and output apparent power, This represents the maximum energy storage capacity.

6. The power coordination control method for improving grid voltage stability through energy storage according to claim 1, characterized in that: Step C involves obtaining the optimal active and reactive power command values ​​based on the optimization solution model. The specific process is as follows: Solving the optimization model yields the optimal active and reactive power output values ​​for energy storage: ； in, and These are the line resistance, reactance, and impedance modulus between the grid-side node and the energy storage node. and These are the active power and reactive power transmitted from the energy storage node to the load-side node, respectively.

7. The power coordination control method for improving grid voltage stability through energy storage according to claim 1, characterized in that: In step D, after the load-side voltage recovers to the target range, the active and reactive power outputs of the energy storage are gradually reduced according to the preset slope in step C, and then restored to the steady-state set value.

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