New energy station reactive voltage regulation technology research and application based on SVG device

Abstract

The invention relates to the technical field of reactive power voltage regulation of new energy stations, and discloses research and application of a reactive power voltage regulation technology of a new energy station based on an SVG device, and the SVG device comprises an SVG body which comprises the following working modes: a manual reactive power output mode; a constant voltage control mode; a constant reactive power control mode; and a constant power factor control mode. When the communication is interrupted, the reactive power generated by the SVG body does not jump, the stable operation of the control bus voltage is ensured, the power supply quality of the power system is improved, the generation and propagation of harmonic waves can be reduced by installing the filter at the inverter output end of the photovoltaic power station or the power grid access point, the control strategy of the inverter can be optimized, and the power supply efficiency is improved. The nonlinear characteristic of the inverter during working is reduced, the generation of harmonic waves is reduced, the impedance characteristic of the SVG body is improved, the resonance suppression capability of the SVG body is improved, the probability of resonance of the system is reduced, and the use effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of reactive voltage regulation in new energy stations, and in particular to research and application of reactive voltage regulation technology in new energy stations based on SVG devices. Background Art

[0002] With the continuous growth of new energy installed capacity in the power grid, the difficulty of grid voltage control is increasing day by day. AVC system and SVG equipment are indispensable technical measures for reactive voltage regulation in power system operation. They play an important role in maintaining the safe and economic operation of the power grid, and their role in ensuring supply in the power grid is becoming increasingly prominent. However, compared with traditional power stations, new energy sites are slightly insufficient in terms of personnel allocation, the ability and quality of production personnel are uneven, production technology management is not in place, and there is insufficient understanding of SVG's own reactive voltage regulation technology, resulting in frequent equipment failures in the station and system voltage fluctuations. Summary of the invention

[0003] The purpose of the present invention is to provide research and application of reactive voltage regulation technology for new energy stations based on SVG devices, so as to solve the problems raised in the above background technology that the existing new energy stations are slightly insufficient in personnel allocation compared with traditional power stations, the ability and quality of production personnel are uneven, the production technology management is not in place, and the understanding of SVG's own reactive voltage regulation technology is insufficient, resulting in frequent equipment failures in the station and system voltage fluctuations.

[0004] In order to solve the above technical problems, the present invention is achieved through the following technical solutions: The present invention is a research and application of reactive voltage regulation technology for new energy stations based on SVG devices, including an SVG body, wherein the SVG body includes the following working modes: Manual reactive power output mode, wherein the manual reactive power output mode is to set relevant fixed values ​​so that the device outputs a constant reactive power; A constant voltage control mode, in which the reactive power absorption and generation of the device is automatically adjusted. When the system voltage is lower than the set voltage reference value, the device outputs capacitive reactive power to increase the system voltage. When the system voltage is higher than the reference value, the device outputs inductive reactive power to reduce the system voltage. Constant reactive power control mode, in which a reactive power target value on the incoming line side is set, and the reactive power output of the device is automatically adjusted by detecting the reactive load on the incoming line to meet the reactive power control target on the incoming line side; Constant power factor control mode, in which the power factor target value on the incoming line side is set, the actual power factor value on the incoming line side is calculated by detecting the active load and reactive load of the busbar, and the reactive power output of the device is automatically adjusted to meet the power factor control target on the incoming line side and provide power quality.

[0005] Furthermore, in the manual reactive power output mode, "+" indicates the generation of capacitive reactive power (increasing the voltage), and "-" indicates the generation of inductive reactive power (reducing the voltage).

[0006] Furthermore, after the communication between the SVG body and the AVC system is interrupted, the operation mode is a constant reactive power control mode and the reactive power instruction should be kept as the original instruction for execution.

[0007] Furthermore, the DC side of the SVG body is a storage capacitor, which provides DC voltage support for the device. The magnitude, frequency and phase of the AC voltage output by the device can be controlled by controlling the drive pulse of the switchable device in the inverter bridge.

[0008] Furthermore, the SVG body transient starting setting refers to the SVG body underpressure compensation setting and the SVG body overpressure compensation setting, and the SVG body transient starting setting interval should be larger than the operating interval given by the power grid, and should be consistent with the AVC system bus voltage high and low blocking setting range.

[0009] Furthermore, during the use of the SVG body, a filter needs to be installed at the inverter output end of the photovoltaic power station or the grid access point to reduce the generation and propagation of harmonics. The control strategy of the inverter can also be optimized to reduce the nonlinear characteristics of the inverter during operation and reduce the generation of harmonics.

[0010] The present invention has the following beneficial effects: The present invention sets an SVG body. Under normal circumstances, in a new energy station where an AVC system is put into use, after the communication between the SVG body and the AVC system is interrupted, the operation mode of the SVG body is a constant reactive power control mode, and the reactive power instruction should be kept as the original instruction execution. When the communication is interrupted, the operation strategy will not cause the reactive power generated by the SVG body to jump, thereby ensuring the stable operation of the control bus voltage. Moreover, installing a filter at the inverter output end or the grid access point of the photovoltaic power station can reduce the generation and propagation of harmonics, optimize the control strategy of the inverter, reduce the nonlinear characteristics of the inverter when it is working, reduce the generation of harmonics, improve the impedance characteristics of the SVG body, increase the resonance suppression capability of the SVG body, reduce the probability of resonance in the system, and improve the use effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0012] Figure 1 This is a schematic diagram of the SVG body principle of the present invention; Figure 2 It is a schematic diagram of the operation mode and compensation characteristics of the SVG body of the present invention; Figure 3 This is a schematic diagram of the influence of harmonics on voltage and current waveforms of the present invention. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0015] See also Figure 1-3 As shown, the present invention is a research and application of reactive voltage regulation technology for new energy stations based on SVG devices, including an SVG body, which includes the following working modes: Manual reactive power output mode: Manual reactive power output mode is to set relevant fixed values ​​to make the device output constant reactive power; In manual reactive power output mode, "+" indicates capacitive reactive power (increasing voltage), and "-" indicates inductive reactive power (reducing voltage).

[0016] Constant voltage control mode: In constant voltage control mode, the device automatically adjusts the reactive power absorption and generation. When the system voltage is lower than the set voltage reference value, the device outputs capacitive reactive power to increase the system voltage. When the system voltage is higher than the reference value, the device outputs inductive reactive power to reduce the system voltage.

[0017] Constant reactive power control mode: In constant reactive power control mode, the reactive power target value on the incoming line is set. By detecting the reactive load on the incoming line, the reactive power output of the device is automatically adjusted to meet the reactive power control target on the incoming line.

[0018] In constant power factor control mode, the power factor target value on the incoming line is set in constant factor control mode. By detecting the active load and reactive load of the bus, the actual power factor value on the incoming line is calculated, and the reactive power output of the device is automatically adjusted to meet the power factor control target on the incoming line and provide power quality. Under normal circumstances, in a new energy station with an AVC system, when the communication between the SVG body and the AVC system is interrupted, the actual operation mode of the SVG body is constant reactive power control mode and the reactive power instruction should be kept as the original instruction. This operation strategy will not cause the reactive power generated by the SVG body to jump when the communication is interrupted, ensuring the stable operation of the control bus voltage.

[0019] After the communication between the SVG body and the AVC system is interrupted, the operation mode is the constant reactive power control mode and the reactive power instruction should be kept as the original instruction execution. The basic principle is to use the high-power power electronic devices (such as IGBT) that can be turned off to form a bridge circuit. The self-commutated bridge circuit is connected to the power grid in parallel through the reactor. The phase and amplitude of the output voltage on the AC side of the bridge circuit are properly adjusted or the AC side current is directly controlled so that the circuit absorbs or emits reactive current that meets the requirements to achieve the purpose of reactive dynamic compensation. The nature and capacity of the output power are determined by the relationship between the AC side output voltage amplitude and the system voltage amplitude. When its amplitude is greater than the system side voltage amplitude, capacitive reactive power is output, and when it is less than the system side voltage amplitude, inductive reactive power is output. The DC side of the SVG body is an energy storage capacitor, which provides DC voltage support for the device. The size, frequency and phase of the AC voltage output by the device can be controlled by controlling the drive pulse of the turnable device in the inverter bridge.

[0020] The transient start setting of the SVG body refers to the under-pressure compensation setting of the SVG body and the over-pressure compensation setting of the SVG body, and the transient start setting range of the SVG body should be larger than the operating range given by the power grid, and should be consistent with the high and low blocking setting range of the AVC system bus voltage; when the operating voltage of the bus controlled by the SVG body is lower than the under-pressure compensation setting and reaches the under-pressure compensation delay setting, the SVG body enters an autonomous transient response, adjusts the reactive power of the SVG body to increase the controlled bus voltage, and when the operating voltage of the bus controlled by the SVG body is higher than the over-pressure compensation setting and reaches the over-pressure compensation delay setting, the SVG body enters an autonomous transient response, adjusts the reactive power of the SVG body to reduce the controlled bus voltage, and the high and low blocking value of the bus voltage of the AVC system is used to deal with the situation of serious voltage exceeding the limit in the power grid. At this time, the dynamic reactive equipment such as the SVG body quickly enters the transient voltage regulation to give priority to the safety of the bus voltage. During this period, the AVC is blocked to avoid affecting the voltage regulation effect of the SVG body.

[0021] The following factors are considered when selecting the SVG body: reactive power compensation requirements, device capacity, control strategy, equipment reliability, coordination with the AVC system, sealing, cooling method, quality of power modules and communication equipment. For sealing, container-type SVG body is preferred, and for cooling, water cooling with special coolant is adopted.

[0022] The SVG main body control strategy selection mainly includes two strategies based on current loop control and voltage loop control, and is equipped with automatic short-circuit protection function.

[0023] During the use of SVG, filters need to be installed at the inverter output end or grid access point of the photovoltaic power station to reduce the generation and propagation of harmonics. The control strategy of the inverter can also be optimized to reduce the nonlinear characteristics of the inverter during operation and reduce the generation of harmonics. For SVG that is greatly affected by harmonics, the latest program version can be upgraded to optimize the control parameters. The impact of harmonics on the SVG body. Harmonics will distort the current and voltage waveforms in the power grid. When the SVG body collects obvious harmonics in the 35kV system, the voltage instantaneous value mutation multiple is greater than 8 times the rated zero-crossing voltage slope, and the SVG body triggers pulse blocking. If the voltage instantaneous value mutation multiple is less than 8 times the rated zero-crossing voltage slope, the pulse is unlocked. The SVG body frequently and repeatedly triggers pulse blocking and unlocking, causing the reactive power of the SVG body to switch between the target value given by the AVC system and 0. If it is in the reactive power generation state, the bus voltage of the system in the station will gradually decrease. If it is in the reactive power absorption state, the bus voltage of the system in the station will gradually increase. Finally, the SVG body trips and stops due to bus voltage oscillation.

[0024] Working principle: Under normal circumstances, in a new energy station with AVC system, when the communication between SVG and AVC system is interrupted, the operation mode of SVG is constant reactive power control mode, and the reactive power instruction should be kept as the original instruction. SVG works in constant reactive power mode, and controls the voltage of the grid-connected point control bus by receiving the adjustment command of the automatic voltage control (AVC) system. The AVC system receives the voltage target value from the grid dispatching management agency, and compares the received voltage target value with the real-time voltage of the grid-connected point control bus in the station. If the target value is higher than the real-time value, it sends a reactive power increase command to SVG, and if the target value is lower than the real-time value, it sends a reactive power reduction command to SVG. SVG adjusts the operation status in real time according to the received reactive power command. SVG is in capacitive working state when sending reactive power, and inductive working state when absorbing reactive power.

[0025] This solution will not cause the reactive power generated by the SVG to jump when communication is interrupted, ensuring stable operation of the control bus voltage and improving the power supply quality of the power system. Installing filters at the inverter output end or grid access point of the photovoltaic power station can reduce the generation and propagation of harmonics, optimize the inverter control strategy, reduce the nonlinear characteristics of the inverter during operation, reduce the generation of harmonics, improve the impedance characteristics of the SVG body, increase the resonance suppression capability of the SVG body, reduce the probability of resonance in the system, and improve the use effect.

[0026] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Research and application of reactive voltage regulation technology for new energy stations based on SVG devices, characterized in that: The SVG body includes the following working modes: Manual reactive power output mode, wherein the manual reactive power output mode is to set relevant fixed values ​​so that the device outputs a constant reactive power; A constant voltage control mode, in which the reactive power absorption and generation of the device is automatically adjusted. When the system voltage is lower than the set voltage reference value, the device outputs capacitive reactive power to increase the system voltage. When the system voltage is higher than the reference value, the device outputs inductive reactive power to reduce the system voltage. Constant reactive power control mode, in which a reactive power target value on the incoming line side is set, and the reactive power output of the device is automatically adjusted by detecting the reactive load on the incoming line to meet the reactive power control target on the incoming line side; Constant power factor control mode, in which the power factor target value on the incoming line side is set, the actual power factor value on the incoming line side is calculated by detecting the active load and reactive load of the busbar, and the reactive power output of the device is automatically adjusted to meet the power factor control target on the incoming line side and provide power quality.

2. The research and application of reactive voltage regulation technology for new energy stations based on SVG devices according to claim 1 is characterized by: In the manual reactive power output mode, "+" indicates the generation of capacitive reactive power (increasing the voltage), and "-" indicates the generation of inductive reactive power (reducing the voltage).

3. The research and application of reactive voltage regulation technology for new energy stations based on SVG devices according to claim 1 is characterized by: After the communication between the SVG body and the AVC system is interrupted, the operation mode is the constant reactive power control mode and the reactive power instruction should be kept as the original instruction for execution.

4. The research and application of reactive voltage regulation technology for new energy stations based on SVG devices according to claim 1 is characterized by: The DC side of the SVG body is an energy storage capacitor, which provides DC voltage support for the device. The magnitude, frequency and phase of the AC voltage output by the device can be controlled by controlling the drive pulse of the switchable device in the inverter bridge.

5. The research and application of reactive voltage regulation technology for new energy stations based on SVG devices according to claim 1 is characterized by: The SVG body transient starting setting refers to the SVG body underpressure compensation setting and the SVG body overpressure compensation setting, and the SVG body transient starting setting range should be larger than the operating range given by the power grid, and should be consistent with the AVC system bus voltage high and low blocking setting range.

6. The research and application of reactive voltage regulation technology for new energy stations based on SVG devices according to claim 1 is characterized by: During the use of the SVG body, a filter needs to be installed at the inverter output end of the photovoltaic power station or the grid access point to reduce the generation and propagation of harmonics. The control strategy of the inverter can also be optimized to reduce the nonlinear characteristics of the inverter during operation and reduce the generation of harmonics.

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