A control method for high voltage ride through of energy storage power station

Abstract

The application discloses a control method for high-voltage ride-through of an energy storage power station, and according to the different degrees of fault and working states, three control methods in three states are given, namely, under normal working conditions, the DC chopper does not act, and the energy storage PCS system outputs a given value of reactive current; under a light degree of fault, the DC chopper acts, and the energy storage PCS system outputs a given value of reactive current; and under a deep degree of fault, a dynamic reactive power compensation device is put into use, the DC chopper acts, and the energy storage PCS system outputs a given value of reactive current. The method can judge the degrees and states of high-voltage faults of a power grid by detecting the voltage of a grid-connected point of the energy storage power station, switches different control modes, protects the PCS converter part of the energy storage power station, and keeps the energy storage power station from being disconnected from the power grid within a certain time when the high-voltage fault occurs.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, specifically the field of grid connection control strategy technology for energy storage power stations, and more specifically, a control method for high voltage ride-through of energy storage power stations. Background Technology

[0002] Considering that system voltage regulation mainly relies on reactive power compensation equipment such as capacitors, dynamic reactive power support capability is lacking. Electrochemical energy storage, with the assistance of dynamic energy storage converters (power conditioning systems, PCS), communication and control equipment, can regulate the voltage of transmission and distribution lines by adjusting the magnitude of their output reactive power. Reactive power support is a typical power-type application, which does not consume the stored energy of batteries, has a relatively short discharge time, but allows for a high frequency, and can significantly improve transient voltage quality due to its rapid response. However, similar to the grid connection of renewable energy sources such as wind turbines, energy storage PCS systems are connected to the grid through three-phase inverters. Therefore, when a sudden rise in grid voltage occurs, on the one hand, power cannot be transmitted from the grid side, and on the other hand, power flows from the grid into the inverter, causing the DC voltage to rise rapidly. If it exceeds the withstand voltage limit of the power semiconductor IGBT, it will cause damage to the inverter components. Therefore, in order to protect the energy storage PCS system, theoretically, the energy storage station should be disconnected in time when a low-voltage or high-voltage fault occurs in the grid. However, in the event of a high-voltage fault, the dynamic reactive power support function of the energy storage station itself requires that the energy storage station cannot be disconnected. Therefore, there is an urgent need to propose a high-voltage ride-through control strategy for energy storage power stations that allows energy storage to continue functioning even in the event of a high-voltage fault in the system, while fully protecting the energy storage power station. Summary of the Invention

[0003] To address the problems existing in the prior art, the purpose of this invention is to provide a control method for high-voltage ride-through in energy storage power stations. This method can provide reactive power support to the power grid during high-voltage faults while protecting the energy storage PCS system, thereby mitigating the impact of high-voltage faults in the system.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] Step 1: During normal grid-connected operation of the energy storage power station, the effective value of the grid connection point voltage is sampled in real time by sensors to obtain the effective value U of the grid connection voltage at the grid connection point. g (t);

[0006] Step 2: Based on the measured U g (t) Whether it exceeds 1.05 times its normal operating condition, determine whether a high-voltage fault has occurred in the power grid. g When (t)>1.05pu, it is determined that a high voltage fault has occurred in the power grid, and proceed to step three; otherwise, it is determined to be a normal operating condition.

[0007] Step 3: Based on the measured U g (t) Whether it exceeds 1.3 times its normal operating condition is used to determine the degree of high voltage fault in the power grid. g If (t)>1.3pu, it is judged as a deep high-voltage fault; otherwise, it is a shallow high-voltage fault.

[0008] Step 4: Switch the high-voltage ride-through control method for energy storage according to the three operating conditions: Under normal operating conditions, the high-voltage ride-through control method for the energy storage power station is as follows: the DC chopper does not operate, the energy storage process control system does not need to provide reactive power support, and the output reactive current setpoint is... Under mild fault conditions, to protect the converter stage of the energy storage process control system, the DC chopper operates. The energy storage process control system mitigates the high-voltage fault by providing reactive power support to the grid. At this time, the output reactive current setpoint is... In the event of a deep fault, to prevent the converter from entering an uncontrollable state, the dynamic reactive power compensation device is activated, the DC chopper operates synchronously, and the energy storage process control system provides reactive power support to the grid to the greatest extent possible, outputting a reactive current setpoint. Where: i max i is the maximum current that the converter is allowed to pass through. d For the active current output by the converter, ΔU g This represents the per-unit value of the increase in voltage relative to normal voltage during a high-voltage fault in the power grid.

[0009] This invention uses 1.05 times the voltage value under normal operating conditions as an indicator to determine whether a high-voltage fault has occurred; and 1.3 times the voltage value under normal operating conditions to determine the depth of the high-voltage fault. Under deep high-voltage faults, in conjunction with a dynamic reactive power compensation device, the energy storage process control system is protected to remain in a controllable state, thereby controlling the energy storage process control system to provide reactive power support to the grid to the greatest extent possible, and outputting a reactive current setpoint. This involves providing reactive power support to the system as much as possible, while ensuring the converter can withstand the maximum current. Under mild high-voltage faults, the energy storage process control system remains under control and can provide some reactive power support to the grid to assist in fault recovery, outputting a reactive current setpoint. ΔU g This represents the per-unit value of the increase in voltage between the grid voltage and the normal voltage during a high-voltage fault. In addition, when a fault occurs, to protect the equipment and ensure that the energy storage process control system has sufficient reactive power capacity, the output active power of the energy storage process control system can be reduced to 0.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1) The control method of the present invention can protect the process control system of the energy storage power station without disconnecting the energy storage power station when a high voltage fault occurs in the power grid system. Therefore, the energy storage power station itself can provide reactive power support to the power grid in the event of a fault by cooperating with the dynamic reactive power compensation device STATCOM according to the depth of the fault, thus helping the power grid to mitigate the impact of the high voltage fault.

[0012] 2) The method of the present invention can determine the depth and fault state of a high voltage fault in the power grid by detecting the voltage at the grid connection point of the energy storage power station, and switch different control modes to protect the PCS converter part of the energy storage power station while keeping the energy storage power station from disconnecting from the grid for a certain period of time when a high voltage fault occurs in the power grid. Attached Figure Description

[0013] Figure 1 This is a topology diagram of an energy storage system applicable to the method of the present invention.

[0014] Figure 2 This is the structural topology of the energy storage process control system with a DC chopper used in this invention.

[0015] Figure 3 This is a flowchart of the present invention.

[0016] Figure 4 This is a block diagram of the control method of the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The present invention incorporates a DC chopper circuit and a dynamic reactive power compensation device (STATCOM) based on a traditional grid-connected energy storage power station model. For example... Figure 1 As shown, a high-voltage fault occurs in the grid-side grid of the energy storage system. The topology of the process control PCS system of the energy storage power station is as follows: Figure 2 As shown, the control strategy of the energy storage power station (such as...) Figure 4 (As shown) provides the STATCOM switching signal for the dynamic reactive power compensation device, the DC chopper operation signal, and the PWM signal for the converter control section. Specific implementation steps are as follows: Figure 3 As shown, the details are as follows:

[0018] Step 1: During normal grid-connected operation of the energy storage power station, the effective value of the grid connection point voltage is sampled in real time by sensors to obtain the effective value U of the grid connection voltage at the grid connection point. g (t);

[0019] Step 2: Based on the measured U g (t) Whether it exceeds 1.05 times its normal operating condition, determine whether a high-voltage fault has occurred in the power grid. gWhen (t)>1.05pu, it is determined that a high voltage fault has occurred in the power grid, and proceed to step three; otherwise, it is determined to be a normal operating condition.

[0020] Step 3: Based on the measured U g (t) Whether it exceeds 1.3 times its normal operating condition is used to determine the degree of high voltage fault in the power grid. g If (t)>1.3pu, it is judged as a deep high-voltage fault; otherwise, it is a shallow high-voltage fault.

[0021] Step 4: Switch the high-voltage ride-through control method for energy storage according to the three operating conditions: Under normal operating conditions, the high-voltage ride-through control method for the energy storage power station is as follows: DC chopper does not operate, STATCOM is not engaged, the energy storage PCS system does not need to provide reactive power support, and the output reactive current setpoint is set. Under mild high-voltage fault conditions, to protect the converter stage of the energy storage PCS system, the DC chopper operates, the STATCOM is not engaged, and the energy storage PCS system mitigates the high-voltage fault by providing reactive power support to the grid. At this time, the output reactive current setpoint is... In the event of a deep high-voltage fault, to prevent the converter from entering an uncontrollable state, the STATCOM is activated, the DC chopper operates synchronously, and the energy storage PCS system provides reactive power support to the grid to the greatest extent possible, outputting a reactive current setpoint.

Claims

1. A control method for high-voltage ride-through in an energy storage power station, characterized in that: Includes the following steps: Step 1: During normal grid-connected operation of the energy storage power station, the effective value of the grid connection point voltage is sampled in real time by sensors to obtain the effective value of the grid connection voltage at the grid connection point. ; Step Two: Based on the measured... Whether the voltage exceeds 1.05 times its normal operating condition is used to determine if a high-voltage fault has occurred in the power grid. If the voltage is >1.05 pu, it is determined that a high voltage fault has occurred in the power grid, and proceed to step three; otherwise, it is determined to be a normal operating condition. Step 3: Based on the measured... Whether it exceeds 1.3 times its normal operating condition is used to determine the severity of a high-voltage fault in the power grid. A voltage level greater than 1.3 pu is considered a deep high-voltage fault; otherwise, it is a shallow high-voltage fault. Step 4: Switch the high-voltage ride-through control method of the energy storage power station according to the three operating conditions: Under normal operating conditions, the high-voltage ride-through control method of the energy storage power station is as follows: the DC chopper does not operate, the energy storage process control system does not need to provide reactive power support, and the output reactive current setpoint is... Under mild high-voltage fault conditions, to protect the converter stage of the energy storage process control system, the DC chopper operates. The energy storage process control system mitigates the high-voltage fault by providing reactive power support to the grid. At this time, the output reactive current setpoint is... In the event of a deep high-voltage fault, to prevent the converter from entering an uncontrollable state, a dynamic reactive power compensation device is activated, the DC chopper operates synchronously, and the energy storage process control system provides reactive power support to the grid, outputting a reactive current setpoint. ,in: The maximum current that the converter is allowed to pass through. To provide active current for the converter output, This represents the per-unit value of the increase in voltage relative to normal voltage during a high-voltage fault in the power grid.

2. The control method for high voltage ride-through of an energy storage power station according to claim 1, characterized in that: Under deep high-voltage faults, the energy storage process control system provides reactive power support to the grid and outputs a reactive current setpoint. This is the result of providing reactive power support in addition to providing active power to the system, taking into account the maximum current that the converter can withstand.

3. The control method for high voltage ride-through of an energy storage power station according to claim 1, characterized in that: Under mild high-voltage faults, the energy storage process control system remains in a controllable state, capable of providing reactive power support to the grid, assisting in grid fault recovery, and outputting a reactive current setpoint. ; In addition, when a fault occurs, in order to protect the equipment and ensure that the energy storage process control system has reactive power capacity, the output active power of the energy storage process control system is reduced to 0.

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