当电网发生故障时,VSG难以支撑微网系统的电压和频率稳定运行。为了使逆变器能稳定运行不脱网,同时具备抑制故障冲击电流的能力,提出具有有功和无功补偿的VSG低电压穿越控制策略。首先,在常规VSG的基础上对VSG发生短路故障时的暂态特性进行分析。其次,针对故障状态下VSG存在的问题,对有功功率进行有功补偿、无功功率进行无功补偿,无功补偿带来的VSG内电势升高,重新整定计算给定电压,并对短路故障参考电流进行越限整定。最后,建立有功和无功补偿VSG低电压穿越控制策略仿真模型进行仿真测试,测试结果表明：改进VSG控制策略相比于常规VSG/有功补偿VSG控制策略,在电压暂降故障期间不仅能实现有功补偿灵活调节VSG输出功角基本与电网功角保持一致,且能实现无功补偿有效支撑VSG输出电压,抑制电压跌落,同时能更好地抑制故障冲击电流,提高系统的暂态稳定性。
Abstract
When the power grid fails, VSG is difficult to support the stable operation of voltage and frequency of the microgrid system. In order to make the inverter operate stably without disconnection, and have the ability to suppress fault impulse current, this paper proposes a VSG low voltage ride through（LVRT） control strategy with active and reactive power compensation. Firstly, based on the conventional VSG, the transient characteristics of VSG when short circuit fault occurs are analyzed. Secondly, in view of the problems existing in VSG under fault condition, active power is compensated for active power and reactive power is compensated for reactive power. The eletric potential in VSG increases due to reactive power compensation. The given voltage is reset and calculated, and the short-circuit fault reference current is adjusted under the limit. Finally, the simulation model of active and reactive compensation VSG LVRT control strategy is established for simulation test. The test results show that the improved VSG control strategy can not only realize active compensation and flexible adjustment of VSG output power angle during voltage sag fault, but also realize reactive compensation to effectively support VSG output voltage and suppress voltage drop, compared with the conventional VSG/active compensation VSG control strategy. At the same time, it can better restrain the fault impulse current and improve the transient stability of the system.
关键词
微电网 /
电压暂降 /
短路电流 /
暂态稳定性 /
低电压穿越
Key words
microgrid /
voltage drop /
fault current /
transient stability /
low voltage ride through
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基金
国家重点研发科技项目（YS2022YFB2400136）; 国网总部科技项目（5400-202216167A-1-1-ZN）
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