New energy station dynamic reactive power compensation device voltage control method, system equipment and medium

Abstract

The present application belongs to the technical field of reactive power compensation, and particularly relates to a new energy station dynamic reactive power compensation device voltage control method, system equipment and medium. In view of the deficiency of the existing new energy station dynamic reactive power compensation device repeatedly switching between the steady-state AVC control mode and the transient emergency voltage support mode, the present application adopts the following technical scheme: the new energy station dynamic reactive power compensation device voltage control method comprises: when the emergency voltage support action or the system fault is cleared, and the actual voltage of the new energy station grid-connected point returns to the normal range, a time delay is first performed, during the time delay period, the dynamic reactive power compensation device adopts voltage closed-loop control, after the time delay is over, the dynamic reactive power compensation device maintains the current reactive power unchanged, until a new AVC reactive power regulation instruction is received, the steady-state AVC control is accepted, and the steady-state mode is entered. The present application has the beneficial effect of avoiding the oscillation problem caused by repeatedly entering and exiting the transient mode in a short time.

Description

Technical Field

[0001] This invention belongs to the field of reactive power compensation technology, specifically relating to voltage control methods, system equipment, and media for dynamic reactive power compensation devices in new energy power plants. Background Technology

[0002] As the penetration rate of new energy sources such as wind power and photovoltaics gradually increases in new power systems, the proportion of conventional synchronous units continues to decline, and the problem of system voltage stability is becoming increasingly prominent. Therefore, the active voltage and reactive power support capability of new energy power plants has become particularly important. According to GB / 19963 and GB / 19964, new energy power plants such as wind power and photovoltaics should make full use of their reactive power capacity and regulation capabilities. When the reactive power capacity of wind turbines or photovoltaic inverters cannot meet the system voltage regulation needs, reactive power compensation devices of appropriate capacity should be centrally installed in the new energy power plant, and dynamic reactive power compensation devices should be installed when necessary.

[0003] Dynamic reactive power compensation devices configured in renewable energy power plants typically possess multiple control methods, such as constant reactive power, constant voltage, and constant power factor. However, the lack of proper coordination between these control methods can easily lead to repeated automatic switching between modes, causing voltage and reactive power oscillations in renewable energy power plants and adversely affecting the stability of the power system.

[0004] Chinese invention patent application No. 201911071218.5 discloses a method and system for coordinated control of reactive power and voltage in wind farms. This patent application proposes that when the grid connection voltage of a wind farm exceeds a certain threshold range, the SVG (Static Var Generator, also known as a Dynamic Var Compensator) and wind turbines enter an emergency control mode. Based on the terminal voltage of the dynamic var compensator and the wind turbines, PI control is performed to adjust reactive power, enabling the renewable energy power station to actively provide dynamic reactive power support during large voltage disturbances. However, the emergency control mode proposed in this patent is not coordinated with AVC (Automatic Voltage Control) steady-state voltage control and renewable energy high-low voltage transient control, which may cause the dynamic var compensator to frequently enter and exit transient modes, leading to oscillation problems. The above problems have occurred in several wind farms in Zhejiang Province.

[0005] In addition, there is room for improvement in the method of obtaining voltage reference values ​​for voltage closed-loop control used during emergency voltage support; usually, multiple dynamic reactive power compensation devices operate in parallel at new energy power plants, and during emergency voltage support, there may be an imbalance in the reactive power distribution of multiple SVGs, resulting in reactive power circulation. Summary of the Invention

[0006] This invention addresses the shortcomings of existing dynamic reactive power compensation devices (SVG) in new energy power plants, which frequently enter and exit transient modes, causing oscillations. It provides a voltage control method for these devices, achieving stable switching between various control modes, including steady-state and transient modes. The invention also provides a voltage control system, computer equipment, and computer-readable storage medium for the dynamic reactive power compensation device. Furthermore, it resolves the lack of coordination when multiple SVG units are operating.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a voltage control method for a dynamic reactive power compensation device in a new energy power station, wherein the voltage control method for the dynamic reactive power compensation device in a new energy power station includes:

[0008] The steps for switching from transient mode to steady-state mode are as follows: In transient mode, when the emergency voltage support is activated or the system fault is cleared, and the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, there is a delay of Δt. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode.

[0009] The voltage control method of the dynamic reactive power compensation device for new energy power plants of the present invention, during the process of switching from transient mode to steady-state mode, after the actual voltage Us of the grid connection point of the new energy power plant recovers to the normal range, does not immediately accept steady-state AVC control, but first waits for a delay of Δt. During the delay period, the dynamic reactive power compensation device adopts voltage closed-loop control. After the delay period, the current reactive power remains unchanged until a new AVC reactive power adjustment command is received, at which point steady-state AVC control is accepted. This effectively avoids the oscillation problem caused by repeated switching between transient mode and steady-state mode.

[0010] As an improvement, in steady-state mode, the AVC substation collects the actual voltage Us at the grid connection point of the new energy power station in real time, and at the same time receives the system reactive power command Ucmd issued by the dispatch master station. After the reactive power allocation strategy, the reactive power command Qref of the dynamic reactive power compensation device of the new energy power station is generated to realize minute-level slow voltage reactive power control.

[0011] As an improvement, in transient mode, the new energy power station performs voltage closed-loop control to quickly generate a large amount of reactive power, achieving millisecond-level voltage and reactive power control.

[0012] As an improvement, the control process in transient mode includes:

[0013] The voltage reference value Uref is generated for voltage closed-loop control. ；

[0014] Based on the actual reactive power generated by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through differential control to achieve reasonable distribution of reactive power among multiple parallel-operating dynamic reactive power compensation devices, avoiding transient reactive power circulation. The correction formula for differential control is specifically expressed as follows:

[0015]

[0016] in, This is the voltage reference value after correction by droop control. This is the adjustment coefficient. This represents the actual reactive power currently generated by the dynamic reactive power compensation device.

[0017] According to voltage reference value The deviation from the actual voltage Us at the current grid connection point is multiplied by the voltage closed-loop proportional coefficient to calculate the reactive power command of the dynamic reactive power compensation device, thereby achieving millisecond-level transient voltage reactive power control.

[0018] As an improvement, the voltage reference value Uref for voltage closed-loop control is determined as follows:

[0019] Following the steady-state voltage before the fault, a delayed sliding window averaging method is used. The system voltage of the previous time period is recorded through a sliding window, and all voltage sampling points within the sliding window are sampled. The average value is taken as the reference value for voltage closed-loop control.

[0020] As an improvement, the voltage control method for the dynamic reactive power compensation device of the new energy power station also includes:

[0021] Steps for switching from steady-state mode to transient mode: When the actual voltage Us at the grid connection point of the new energy power station exceeds the upper and lower limits of the allowable steady-state operating range, the dynamic reactive power compensation device enters the emergency voltage support transient mode, and the dynamic reactive power compensation device switches to voltage closed-loop control to quickly generate dynamic reactive power.

[0022] As an improvement, the normal range U_ret1-U_ret2 is within the steady-state operating range Us_min-Us_max.

[0023] The voltage control system for the dynamic reactive power compensation device in new energy power plants includes:

[0024] Steady-state control module;

[0025] Transient control module;

[0026] The switching module is used to ensure that when the emergency voltage support is activated or the system fault is cleared, and the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, there is a delay of Δt. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode.

[0027] The computer device includes a processor and a storage medium, the storage medium storing a computer program, which, when executed by the processor, implements the aforementioned voltage control method for the dynamic reactive power compensation device of the new energy power station.

[0028] A computer-readable storage medium having a computer program stored thereon, which, when executed, implements the aforementioned voltage control method for the dynamic reactive power compensation device of a new energy power station. Attached Figure Description

[0029] Figure 1 This is a flowchart of the voltage control method for the dynamic reactive power compensation device of a new energy power station according to an embodiment of the present invention.

[0030] Figure 2 This is an architecture diagram of the voltage control system of the dynamic reactive power compensation device for new energy power plants according to an embodiment of the present invention.

[0031] Figure 3 This is the architecture diagram of the voltage control system of the existing dynamic reactive power compensation device in new energy power plants. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0033] See Figure 1 and Figure 2 The voltage control method for the dynamic reactive power compensation device of a new energy power station according to an embodiment of the present invention includes:

[0034] The steps for switching from transient mode to steady-state mode are as follows: In transient mode, when the emergency voltage support is activated or the system fault is cleared, the actual voltage Us at the grid connection point of the new energy power station returns to the normal range (U_ret1 to U_ret2). After a delay of Δt, the dynamic reactive power compensation device continues to use voltage closed-loop control during the delay period. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode.

[0035] In this embodiment, under steady-state mode, the AVC substation collects the actual voltage Us at the grid connection point of the new energy power station in real time, and at the same time receives the system reactive power command Ucmd issued by the dispatch master station. After the reactive power allocation strategy, the reactive power command Qref of the dynamic reactive power compensation device of the new energy power station is generated to realize minute-level slow voltage reactive power control.

[0036] In this embodiment, under transient mode, the new energy power station performs voltage closed-loop control to quickly generate a large amount of reactive power, achieving millisecond-level voltage and reactive power control.

[0037] In this embodiment, the control process in transient mode includes:

[0038] The voltage reference value Uref is generated for voltage closed-loop control. ；

[0039] Based on the actual reactive power generated by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through differential control to achieve reasonable distribution of reactive power among multiple parallel-operating dynamic reactive power compensation devices, avoiding transient reactive power circulation. The correction formula for differential control is specifically expressed as follows:

[0040]

[0041] in, This is the voltage reference value after correction by droop control. This is the adjustment coefficient. This represents the actual reactive power currently generated by the dynamic reactive power compensation device.

[0042] According to voltage reference value The deviation from the actual voltage Us at the current grid connection point is multiplied by the voltage closed-loop proportional coefficient to calculate the reactive power command of the dynamic reactive power compensation device, thereby achieving millisecond-level transient voltage reactive power control.

[0043] The voltage reference value Uref for voltage closed-loop control can be determined in the following ways:

[0044] Constant reference value;

[0045] Following the steady-state voltage before the fault, a delayed sliding window averaging method is used. The system voltage is recorded through a sliding window for a period of time before the fault occurs, and all voltage sampling points within the sliding window are analyzed. The average value is taken as the reference value for voltage closed-loop control.

[0046] A fixed difference is set, that is, a fixed voltage deviation △U is set. When the grid connection point voltage exceeds the upper limit of the steady-state operation boundary Us_max, voltage closed-loop control is performed according to Us_max-△U. When the grid connection point voltage exceeds the lower limit of the steady-state operation boundary Us_min, voltage closed-loop control is performed according to Us_min+△U.

[0047] The average value is calculated based on the average of the upper and lower limits of the steady-state operating boundary, Uref=(Us_max+Us_min) / 2.

[0048] In this embodiment, the method of following the steady-state voltage before the fault is adopted. Compared with the other three methods, the voltage reference value Uref changes in real time and is more accurate.

[0049] In this embodiment, the voltage control method for the dynamic reactive power compensation device of the new energy power station further includes:

[0050] Steps for switching from steady-state mode to transient mode: When the actual voltage Us at the grid connection point of the new energy power station exceeds the upper and lower limits of the allowable steady-state operating range, the dynamic reactive power compensation device enters the emergency voltage support transient mode, and the dynamic reactive power compensation device switches to voltage closed-loop control to quickly generate dynamic reactive power.

[0051] In this embodiment, the normal range U_ret1-U_ret2 is within the steady-state operating range Us_min-Us_max. For example, if the normal range is 227-240, the steady-state operating range is 225-242. After a voltage closed-loop control with a delay of Δt time, the voltage will be closer to the reference value (e.g., 230).

[0052] contrast Figure 2 and Figure 3 In steady-state mode, the process of existing control methods and the control method of this invention is basically the same.

[0053] When a system failure or other situation requiring emergency voltage support occurs, the switching process from steady-state mode to transient mode is the same in both existing control methods and the control method of this embodiment. Both methods determine that the actual voltage Us at the grid connection point is outside the steady-state operating boundary (greater than the upper limit of the steady-state operating boundary Us_max or less than the lower limit of the steady-state operating boundary Us_min) and then perform a switching operation to enter transient mode.

[0054] In transient mode, both existing control methods and the control method of this invention involve voltage closed-loop control of the renewable energy power station to rapidly generate a large amount of reactive power, achieving millisecond-level voltage and reactive power control. The difference lies in that existing control methods directly use the voltage reference value Uref of the voltage closed-loop control, while the control method of this invention uses a different method to determine the voltage reference value Uref and additionally performs differential control on the voltage reference value Uref of the voltage closed-loop control.

[0055] The control method of this invention uses a voltage reference value Uref that follows the steady-state voltage before the fault. Specifically, it employs a delayed sliding window averaging method, recording the system voltage of the previous time period through a sliding window, and sampling all voltage points within the sliding window. The average value is taken as the reference value for voltage closed-loop control.

[0056] The control method of this invention uses the following formula for differential control of the voltage reference value Uref:

[0057]

[0058] in, This is the voltage reference value after correction by droop control. This is the adjustment coefficient. This represents the current actual reactive power output of the dynamic reactive power compensation device.

[0059] The control method of this invention is based on the actual reactive power output of each dynamic reactive power compensation device. The voltage reference value Uref of the voltage closed-loop control is corrected so that when multiple dynamic reactive power compensation devices are running in parallel in a new energy power plant, the reactive power among the multiple dynamic reactive power compensation devices can be adaptively distributed to avoid reactive power circulation.

[0060] During the transition from transient mode to steady-state mode, the existing control method is as follows: when the emergency voltage support is activated or the system fault is cleared, and it is determined that the actual voltage Us at the grid connection point of the new energy power station has returned to the normal range (U_ret2 < Us < U_ret1), the dynamic reactive power compensation device immediately issues reactive power at the level before the fault. However, in the control method of this embodiment, after the emergency voltage support is activated or the system fault is cleared, and it is determined that the actual voltage Us at the grid connection point of the new energy power station has returned to the normal range (U_ret2 < Us < U_ret1), a delay of Δt time is first applied. During this delay period, the dynamic reactive power compensation device uses voltage closed-loop control. This delayed voltage closed-loop control makes the voltage closer to the reference value. After the delay ends, the dynamic reactive power compensation device maintains the current (at the end of the delay) reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control.

[0061] The existing control method assumes that before the accident, the dynamic reactive power compensation device at the renewable energy power station is in steady-state mode, receiving a reactive power command such as 10Mvar from the AVC. When the system fails and the voltage drops significantly, the dynamic reactive power compensation device enters transient mode. In transient mode, the dynamic reactive power compensation device switches to voltage closed-loop control mode and quickly issues reactive power such as 50Mvar according to the Qref2 reactive power command to support the grid connection point voltage back to the normal range. After the voltage returns to the normal range, the dynamic reactive power compensation device immediately issues reactive power of the same amount as before the fault, that is, executes the original Qref1 reactive power command of 10Mvar, resulting in insufficient reactive power (a permanent grid fault may cause long-term low voltage at the end of the system). The power station voltage will drop significantly again, and the dynamic reactive power compensation device will re-enter transient mode. Frequent entry and exit from transient mode will generate oscillations.

[0062] In the control method of this invention embodiment, under transient mode, when the emergency voltage support action is activated or the system fault is cleared, and the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, the voltage closed-loop control mode continues to be used for a delay time Δt to make the actual voltage Us closer to the reference value. After the delay time Δt, the dynamic reactive power compensation device maintains the current (at the end of the delay) reactive power fixed, such as 50Mvar, until a new AVC reactive power adjustment command is received (the AVC master station calculates the adjustment command based on the latest voltage and reactive power situation of the system), then it accepts steady-state AVC control, thereby maintaining the voltage within the normal range without dropping and avoiding repeated entry and exit from transient mode.

[0063] Emergency voltage support time is in the millisecond range (around 30 milliseconds), delay time Δt is in the second range (e.g., 1s to 10s), and AVC commands are in the minute range.

[0064] The voltage control method for the dynamic reactive power compensation device in new energy power plants according to this invention has a more accurate voltage reference value Uref, which follows the steady-state voltage before the fault. In transient mode, a differential control step is added to adaptively distribute reactive power among multiple dynamic reactive power compensation devices, avoiding reactive power circulation. During the transition from transient to steady-state mode, after the actual voltage Us at the grid connection point of the new energy power plant returns to the normal range, a delay of Δt is applied. During this delay, the dynamic reactive power compensation device uses closed-loop voltage control to make the actual voltage closer to the reference voltage. After the delay, the current reactive power remains fixed until a new AVC reactive power adjustment command is received, at which point steady-state AVC control is accepted. This effectively avoids the oscillation problem caused by frequent transitions between transient and steady-state modes.

[0065] This invention also provides a voltage control system for a dynamic reactive power compensation device in a new energy power station, comprising:

[0066] Steady-state control module;

[0067] Transient control module;

[0068] The switching module is used to switch between the steady-state control module and the transient control module. During the transition from transient mode to steady-state mode, after the actual voltage Us at the grid connection point of the new energy power plant returns to the normal range, there is a delay of Δt. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode.

[0069] This invention also provides a computer device, including a processor and a storage medium, wherein the storage medium stores a computer program, and when the computer program is executed by the processor, it implements the aforementioned voltage control method for the dynamic reactive power compensation device of a new energy power station.

[0070] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed, implements the aforementioned voltage control method for the dynamic reactive power compensation device of a new energy power station.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A voltage control method for a dynamic reactive power compensation device in a new energy power station, characterized in that: The voltage control method for the dynamic reactive power compensation device at the new energy power station includes: The steps for switching from transient mode to steady-state mode are as follows: In transient mode, when the emergency voltage support is activated or the system fault is cleared, and the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, there is a delay of Δt. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode. The control process in transient mode includes: The voltage reference value Uref is generated for voltage closed-loop control. ； Based on the actual reactive power generated by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through differential control to achieve reasonable distribution of reactive power among multiple parallel-operating dynamic reactive power compensation devices, avoiding transient reactive power circulation. The correction formula for differential control is specifically expressed as follows: in, This is the voltage reference value after correction by droop control. This is the adjustment coefficient. This represents the actual reactive power currently generated by the dynamic reactive power compensation device. According to voltage reference value The deviation from the actual voltage Us at the current grid connection point is multiplied by the voltage closed-loop proportional coefficient to calculate the reactive power command of the dynamic reactive power compensation device, thereby achieving millisecond-level transient voltage reactive power control.

2. The voltage control method for the dynamic reactive power compensation device of a new energy power station according to claim 1, characterized in that: In steady-state mode, the AVC substation collects the actual voltage Us at the grid connection point of the new energy power plant in real time, and at the same time receives the system reactive power command Ucmd issued by the dispatch master station, generates the reactive power command Qref of the dynamic reactive power compensation device of the new energy power plant, and realizes minute-level slow voltage reactive power control.

3. The voltage control method for the dynamic reactive power compensation device of a new energy power station according to claim 1, characterized in that: In transient mode, the renewable energy power station performs voltage closed-loop control, rapidly generating a large amount of reactive power, achieving millisecond-level voltage and reactive power control.

4. The voltage control method for the dynamic reactive power compensation device of a new energy power station according to claim 1, characterized in that: The voltage reference value Uref for voltage closed-loop control is determined as follows: Following the steady-state voltage before the fault, a delayed sliding window averaging method is adopted. The system voltage of the previous time period is recorded through a sliding window, and the average of all voltage sampling points within the sliding window is used as the reference value for voltage closed-loop control.

5. The voltage control method for the dynamic reactive power compensation device of a new energy power station according to claim 1, characterized in that: The voltage control method for the dynamic reactive power compensation device in the new energy power station also includes: Steps for switching from steady-state mode to transient mode: When the actual voltage Us at the grid connection point of the new energy power station exceeds the allowable steady-state operating range Us_min-Us_max, the dynamic reactive power compensation device enters the emergency voltage support transient mode, and the dynamic reactive power compensation device switches to voltage closed-loop control to quickly generate dynamic reactive power.

6. The voltage control method for the dynamic reactive power compensation device of a new energy power station according to claim 5, characterized in that: The normal range U_ret1-U_ret2 is within the steady-state operating range Us_min-Us_max.

7. A voltage control system for a dynamic reactive power compensation device in a new energy power station, employing the voltage control method for a dynamic reactive power compensation device in a new energy power station as described in any one of claims 1 to 6, characterized in that: include: Steady-state control module; Transient control module; The switching module is used to ensure that when the emergency voltage support is activated or the system fault is cleared, and the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, there is a delay of Δt. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until a new AVC reactive power adjustment command is received, at which point it accepts steady-state AVC control and enters steady-state mode.

8. A computer device, comprising a processor and a storage medium, wherein the storage medium stores a computer program, characterized in that: When the computer program is executed by the processor, it implements the voltage control method for the dynamic reactive power compensation device of the new energy power station as described in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: It stores a computer program, which, when executed, implements the voltage control method for the dynamic reactive power compensation device of the new energy power station as described in any one of claims 1 to 6.

Images