Voltage control method and system equipment for dynamic reactive power compensation device of new energy station and medium

Abstract

The invention 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 a medium. In order to overcome the defect that an existing new energy station dynamic reactive power compensation device is repeatedly switched between a steady state AVC control mode and a transient state emergency voltage support mode, the invention adopts the following technical scheme: the new energy station dynamic reactive power compensation device voltage control method comprises the following steps: when an emergency voltage support action or system fault clearing is carried out; after the actual voltage of the grid-connected point of the new energy station recovers to return to a normal range, a period of time delay is performed, the dynamic reactive power compensation device adopts voltage closed-loop control within the time delay period, the dynamic reactive power compensation device keeps the current reactive power unchanged after the time delay is ended, and the dynamic reactive power compensation device receives steady-state AVC control until a new AVC reactive power regulation instruction is received. And entering a steady-state mode. The method has the beneficial effect that the oscillation problem caused by repeatedly entering and exiting a transient mode in a short time is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of reactive power compensation, and particularly relates to a voltage control method, system equipment and medium for a dynamic reactive power compensation device in a new energy power station. Background Art

[0002] With the gradual increase in the penetration rate of new energy sources such as wind power and photovoltaic power in the new power system and the continuous decrease in the proportion of conventional synchronous units, the problem of system voltage stability has gradually become prominent, and the voltage reactive power active support ability of new energy power stations has become particularly important. According to the regulations of GB / 19963 and GB / 19964, new energy power stations such as wind power and photovoltaic power should make full use of their reactive power capacity and its regulation ability. When the reactive power capacity of wind turbines or photovoltaic inverters cannot meet the system voltage regulation requirements, a reactive power compensation device with an appropriate capacity should be centrally installed in the new energy power station, and a dynamic reactive power compensation device should be installed if necessary.

[0003] The dynamic reactive power compensation devices configured in new energy power stations usually have various control means such as constant reactive power, constant voltage, and constant power factor. However, the switching between control means lacks reasonable coordination, which easily leads to automatic repeated switching between modes, causing oscillations in the voltage and reactive power of new energy power stations and having an adverse impact on the stability of the power system.

[0004] The Chinese invention patent application with the patent application number 201911071218.5 discloses a method and system for coordinated control of reactive power and voltage in a wind farm. The invention patent application proposes that when the grid connection point voltage of the wind farm exceeds a certain threshold range, the SVG (Static Var Generator, that is, the dynamic reactive power compensation device) and the wind turbine enter the emergency control mode, and PI control is carried out based on the terminal voltage of the dynamic reactive power compensation device and the wind turbine to adjust the reactive power, so that the new energy power station actively provides dynamic reactive power support during the large voltage disturbance process. However, the emergency control mode proposed in this patent does not cooperate with the AVC (Automatic Voltage Control) steady-state voltage control and the new energy high and low voltage ride-through transient voltage control, which may cause the dynamic reactive power compensation device to frequently enter and exit the transient mode, bringing oscillation problems. The above problems have occurred in many wind farms in Zhejiang.

[0005] In addition, there is also room for improvement in the acquisition method of the voltage reference value of the voltage closed-loop control used during emergency voltage support; usually, multiple dynamic reactive power compensation devices in a new energy power station operate in parallel. During the emergency voltage support process, the reactive power distribution of multiple SVG devices may be unbalanced, resulting in reactive power circulation. Summary of the Invention

[0006] In view of the deficiency that the existing dynamic reactive power compensation devices in new energy power stations are prone to frequently enter and exit the transient mode, causing oscillations, the present invention provides a voltage control method for a dynamic reactive power compensation device in a new energy power station, realizing stable switching between multiple control modes of steady state / transient state. The present invention also provides a voltage control system, a computer device, and a computer-readable storage medium for a dynamic reactive power compensation device in a new energy power station. Further, it solves the deficiency of the lack of coordination in the operation of multiple SVG units.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A voltage control method for a dynamic reactive power compensation device in a new energy power station, the voltage control method for the dynamic reactive power compensation device in the new energy power station includes: Switching step from transient mode to steady state mode: In the transient mode, when the emergency voltage support action occurs or the system fault is cleared, after the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, first, there is a delay of △t time. During the delay period, the dynamic reactive power compensation device continues to adopt voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until it receives a new AVC reactive power regulation instruction and then accepts the steady-state AVC control and enters the steady state mode.

[0008] In the voltage control method of the dynamic reactive power compensation device in the new energy power station of the present invention, during the process of switching from the transient mode to the steady state mode, after the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, it does not immediately accept the steady-state AVC control. Instead, there is a delay of △t time first. During the delay period, the dynamic reactive power compensation device adopts voltage closed-loop control. After the delay period, the current reactive power is maintained unchanged until it receives a new AVC reactive power regulation instruction and then accepts the steady-state AVC control, thus effectively avoiding the oscillation problem caused by the repeated switching between the transient mode and the steady state mode.

[0009] As an improvement, in the steady state mode, the AVC substation real-time collects the actual voltage Us at the grid connection point of the new energy power station, and at the same time receives the system reactive power instruction Ucmd issued by the dispatching master station. After the reactive power distribution strategy, it generates the reactive power instruction Qref for the dynamic reactive power compensation device in the new energy power station to achieve slow voltage reactive power control at the minute level.

[0010] As an improvement, in the transient mode, the new energy power station conducts voltage closed-loop control and quickly emits a large amount of reactive power to achieve voltage reactive power control at the millisecond level.

[0011] As an improvement, the control process in the transient mode includes: Generating the voltage reference value Uref for voltage closed-loop control ； According to the reactive power actually generated by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through droop control to achieve a reasonable distribution of the reactive power of multiple dynamically reactive power compensation devices operating in parallel, avoiding the occurrence of transient reactive power circulation. The correction formula of the droop control is specifically expressed as:

[0012] Wherein, is the voltage reference value corrected by the droop control, is the droop coefficient, is the reactive power actually generated by the dynamic reactive power compensation device at present; According to the deviation between the voltage reference value and the actual voltage Us of the current grid connection point, multiplying by the voltage closed-loop proportional coefficient, the reactive power command of the dynamic reactive power compensation device is calculated to achieve millisecond-level transient voltage and reactive power control.

[0013] As an improvement, the determination method of the voltage reference value Uref of the voltage closed-loop control is: Following the steady-state voltage before the fault, adopting the method of delayed sliding window averaging, recording the system voltage of the previous time period through the sliding window, and taking the average of all voltage sampling points within the sliding window as the reference value of the voltage closed-loop control.

[0014] As an improvement, the voltage control method of the dynamic reactive power compensation device in the new energy power station also includes: Steady-state mode to transient mode switching step: When the actual voltage Us of the grid connection point of the new energy power station exceeds the upper and lower limits of the allowable steady-state operation 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 and quickly generates dynamic reactive power.

[0015] As an improvement, the normal range U_ret1 - U_ret2 is within the steady-state operation range Us_min - Us_max.

[0016] The voltage control system of the dynamic reactive power compensation device in the new energy power station includes: Steady-state control module; Transient control module; Switching module, used for when the emergency voltage support action or the system fault is cleared, and the actual voltage Us of the grid connection point of the new energy power station returns to the normal range, after a delay of △t time. During the delay period, the dynamic reactive power compensation device continues to adopt voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power unchanged until it receives a new AVC reactive power regulation command and then accepts the steady-state AVC control and enters the steady-state mode.

[0017] A computer device, including a processor and a storage medium, stores a computer program in the storage medium. When the computer program is executed by the processor, it implements the voltage control method of the new energy power station dynamic reactive power compensation device described above.

[0018] A computer-readable storage medium stores a computer program thereon. When the computer program is executed, it implements the voltage control method of the new energy power station dynamic reactive power compensation device described above. Description of the Drawings

[0019] Figure 1 It is a flowchart of the voltage control method of the new energy power station dynamic reactive power compensation device according to an embodiment of the present invention.

[0020] Figure 2 It is an architecture diagram of the voltage control system of the new energy power station dynamic reactive power compensation device according to an embodiment of the present invention.

[0021] Figure 3 It is an architecture diagram of the existing voltage control system of the new energy power station dynamic reactive power compensation device. Detailed Embodiments

[0022] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only the preferred embodiments of the present invention and not all of them. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention.

[0023] Refer to Figure 1 and Figure 2 , the voltage control method of the new energy power station dynamic reactive power compensation device according to an embodiment of the present invention, the voltage control method of the new energy power station dynamic reactive power compensation device includes: Step of switching from transient mode to steady state mode: In transient mode, when an emergency voltage support action or 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 (U_ret1 to U_ret2), after a delay of △t time. 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 it receives a new AVC reactive power regulation command and then accepts steady-state AVC control to enter the steady state mode.

[0024] In this embodiment, 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 dispatching master station. After the reactive power distribution strategy, it generates the reactive power command Qref of the new energy power station dynamic reactive power compensation device to achieve slow voltage reactive power control at the minute level.

[0025] In this embodiment, in the transient mode, the new energy power station performs voltage closed-loop control, quickly emits a large amount of reactive power, and realizes millisecond-level voltage reactive power control.

[0026] In this embodiment, the control process in the transient mode includes: Generating a voltage reference value Uref for voltage closed-loop control ； According to the reactive power actually emitted by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through droop control to realize reasonable distribution of the reactive power of multiple parallel-operating dynamic reactive power compensation devices and avoid transient reactive power circulation. The correction formula of the droop control is specifically expressed as:

[0027] Wherein, is the voltage reference value corrected by the droop control, is the droop coefficient, is the reactive power actually emitted by the dynamic reactive power compensation device currently; According to the 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, realizing millisecond-level transient voltage reactive power control.

[0028] The determination methods of the voltage reference value Uref for voltage closed-loop control are as follows: Constant reference value; Following the steady-state voltage before the fault, using the time-delay sliding window average method, the system voltage in a period before the fault occurrence is recorded through the sliding window, and all voltage sampling points are averaged to be used as the reference value for voltage closed-loop control; Fixed difference, that is, a fixed voltage deviation △U is set. When the grid connection point voltage exceeds the upper limit Us_max of the steady-state operation boundary, voltage closed-loop control is performed according to Us_max - △U. When the grid connection point voltage exceeds the lower limit Us_min of the steady-state operation boundary, voltage closed-loop control is performed according to Us_min + △U; Average value, that is, calculated according to the average value of the upper and lower limits of the steady-state operation boundary, Uref = (Us_max + Us_min) / 2.

[0029] In this embodiment, by adopting the method of following the steady-state voltage before the fault, compared with the other three methods, the voltage reference value Uref changes in real time and follows more accurately.

[0030] In this embodiment, the voltage control method of the dynamic reactive power compensation device of the new energy power station further includes: Steps for switching from the steady-state mode to the 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 operation 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 and quickly emits dynamic reactive power.

[0031] In this embodiment, the normal range U_ret1 - U_ret2 is within the steady-state operation range Us_min - Us_max. For example, if the normal range is 227 - 240 and the steady-state operation range is 225 - 242. After the voltage closed-loop control with a time delay of △t, the voltage will be closer to the reference value (such as 230).

[0032] Comparison Figure 2 and Figure 3 , in the steady-state mode, the processes of the existing control method and the control method of this embodiment of the present invention are basically the same.

[0033] When a system fault or other situations requiring emergency voltage support occur, the switching processes from the steady-state mode to the transient mode of the existing control method and the control method of this embodiment of the present invention are the same. Both judge that the actual voltage Us at the grid connection point is outside the steady-state operation boundary (greater than the upper limit Us_max of the steady-state operation boundary or less than the lower limit Us_min of the steady-state operation boundary), and then perform the switching operation to enter the transient mode.

[0034] In the transient mode, both the existing control method and the control method of this embodiment of the present invention perform voltage closed-loop control for the new energy power station, quickly emit a large amount of reactive power, and achieve millisecond-level voltage and reactive power control. The difference is that the existing control method directly uses the voltage reference value Uref of the voltage closed-loop control, while the control method of this embodiment of the present invention determines the voltage reference value Uref in a different way and additionally performs differential control on the voltage reference value Uref of the voltage closed-loop control.

[0035] For the control method of this embodiment of the present invention, the voltage reference value Uref follows the steady-state voltage before the fault. Specifically, in the way of delayed sliding window averaging, the system voltage in the previous time period is recorded through the sliding window, and the average value of all voltage sampling points in the sliding window is taken as the reference value for voltage closed-loop control.

[0036] For the control method of this embodiment of the present invention, the formula for performing differential control on the voltage reference value Uref is:

[0037] Where, is the voltage reference value corrected by differential control, is the differential coefficient, is the actual reactive power currently emitted by the dynamic reactive power compensation device.

[0038] The control method of the embodiment of the present invention corrects the voltage reference value Uref of the voltage closed-loop control according to the actual reactive power currently generated by each dynamic reactive power compensation device so that when multiple dynamic reactive power compensation devices operate in parallel in a new energy power station, the reactive power between the multiple dynamic reactive power compensation devices can be adaptively allocated to avoid reactive power circulation.

[0039] During the switching process from the transient mode to the steady state mode, the existing control method is as follows: when the emergency voltage support action or the system fault is cleared, after it is judged that the actual voltage Us at the grid connection point of the new energy power station returns to the normal range (U_ret2 < Us < U_ret1), the dynamic reactive power compensation device immediately emits the reactive power of the same magnitude as before the fault. However, for the control method of the embodiment of the present invention, after the emergency voltage support action or the system fault is cleared and it is judged that the actual voltage Us at the grid connection point of the new energy power station returns to the normal range (U_ret2 < Us < U_ret1), it first delays for a period of Δt. During the delay period, the dynamic reactive power compensation device adopts voltage closed-loop control. The 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 (when the delay ends) reactive power unchanged until it receives a new AVC reactive power regulation instruction and then accepts the steady state AVC control.

[0040] For the existing control method, it is assumed that before the accident, the dynamic reactive power compensation device of the new energy power station is in the steady state mode and receives a reactive power instruction from the AVC, such as 10 Mvar. When a system fault occurs and the voltage drops significantly, the dynamic reactive power compensation device enters the transient mode. In the transient mode, the dynamic reactive power compensation device switches to the voltage closed-loop control mode and quickly emits reactive power, such as 50 Mvar, according to the Qref2 reactive power instruction 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 emits the reactive power of the same magnitude as before the fault, that is, executes the original Qref1 reactive power instruction of 10 Mvar, resulting in insufficient reactive power (a permanent grid fault may cause long-term low voltage at the end of the system), and the voltage of the power station will drop significantly again. The dynamic reactive power compensation device enters the transient mode again, frequently entering and leaving the transient mode, generating oscillations.

[0041] In the control method according to the embodiment of the present invention, in the transient mode, when the emergency voltage support action or 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 is continued for a delay time △t to make the actual voltage Us closer to the reference value. After the delay time △t, the dynamic reactive power compensation device maintains the current (at the end of the delay) reactive power constant, such as 50 Mvar, until a new AVC reactive power regulation instruction (calculated by the AVC master station based on the latest voltage and reactive power conditions of the system) is received, and then the steady-state AVC control is accepted, so as to maintain the voltage within the normal range without dropping and avoid repeatedly entering and exiting the transient mode.

[0042] The emergency voltage support time is in the millisecond level (about 30 milliseconds), the delay time △t is in the second level (such as 1 s to 10 s), and the AVC instruction is in the minute level.

[0043] In the voltage control method of the dynamic reactive power compensation device of the new energy power station according to the embodiment of the present invention, compared with the existing control method, the voltage reference value Uref follows the steady-state voltage before the fault, and the voltage reference value is more accurate; in the transient mode, a differential control step is added, which can adaptively distribute the reactive power between multiple dynamic reactive power compensation devices to avoid reactive power circulation; during the process of switching from the transient mode to the steady-state mode, after the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, it first passes through a delay of △t time. During the delay period, the dynamic reactive power compensation device adopts voltage closed-loop control to make the actual voltage closer to the reference voltage. After the delay period, the current reactive power is maintained constant until a new AVC reactive power regulation instruction is received, and then the steady-state AVC control is accepted, thus effectively avoiding the oscillation problem caused by frequently entering and exiting the transient mode.

[0044] The embodiment of the present invention also provides a voltage control system for a dynamic reactive power compensation device of a new energy power station, including: A steady-state control module; A transient control module; A switching module for switching between the steady-state control module and the transient control module. During the process of switching from the transient mode to the steady-state mode, when the actual voltage Us at the grid connection point of the new energy power station returns to the normal range, it first passes through a delay of △t time. During the delay period, the dynamic reactive power compensation device continues to adopt voltage closed-loop control. After the delay ends, the dynamic reactive power compensation device maintains the current reactive power constant until a new AVC reactive power regulation instruction is received, and then the steady-state AVC control is accepted and the steady-state mode is entered.

[0045] The embodiment of the present invention also provides a computer device, including a processor and a storage medium. The storage medium stores a computer program, and when the computer program is executed by the processor, it implements the foregoing voltage control method of the dynamic reactive power compensation device of the new energy power station.

[0046] An embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed, the foregoing voltage control method for the dynamic reactive power compensation device of the new energy power station is implemented.

[0047] As described above, the above are only specific embodiments of the present invention, but the protection scope 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 modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A voltage control method for a dynamic reactive power compensation device in a new energy station, characterized in that: The voltage control method of the dynamic reactive power compensation device of the new energy station includes: Steps for switching from transient mode to steady-state mode: In transient mode, when the emergency voltage support is activated or the system fault is cleared, and the actual voltage Us at the grid-connected point of the new energy station returns to the normal range, it will first undergo a delay of △t time. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay, the dynamic reactive power compensation device maintains the current reactive power unchanged until it receives a new AVC reactive power adjustment instruction, then it accepts steady-state AVC control and enters steady-state mode.

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

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

4. The voltage control method of the dynamic reactive power compensation device of the new energy station according to claim 3 is characterized in that: The control process in transient mode includes: Generates voltage reference value Uref for voltage closed-loop control ； According to the reactive power actually generated by the dynamic reactive power compensation device, the voltage reference value Uref is dynamically adjusted through differential control to achieve reasonable reactive power distribution of multiple parallel-operating dynamic reactive power compensation devices and avoid transient reactive circulating current. The correction formula of differential control is specifically expressed as: in, is the voltage reference value after correction by differential control, is the adjustment coefficient, It is the reactive power actually generated by the dynamic reactive power compensation device at present; According to the voltage reference The deviation from the actual voltage Us at the current grid-connected point is multiplied by the voltage closed-loop proportional coefficient to calculate the reactive power command of the dynamic reactive power compensation device, thus achieving millisecond-level transient voltage reactive power control.

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

6. The voltage control method of the dynamic reactive power compensation device of the new energy station according to claim 1 is characterized in that: The voltage control method of the dynamic reactive power compensation device of the new energy 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 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.

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

8. A voltage control system for a dynamic reactive power compensation device of a new energy station, adopting a voltage control method for a dynamic reactive power compensation device of a new energy station as claimed in any one of claims 1 to 7, characterized in that: include: Steady state control module; Transient control module; The switching module is used 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 station returns to the normal range. It will first undergo a delay of △t. During the delay period, the dynamic reactive power compensation device continues to use voltage closed-loop control. After the delay, the dynamic reactive power compensation device maintains the current reactive power unchanged until it receives a new AVC reactive power adjustment instruction, then it accepts steady-state AVC control and enters steady-state mode.

9. 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 a processor, the voltage control method of the dynamic reactive power compensation device of a new energy station is implemented as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, a voltage control method for a dynamic reactive power compensation device of a new energy station as described in any one of claims 1 to 7 is implemented.

Images