不平衡工况下新能源并网变换器韧性分析及优化控制  

Toughness Analysis and Optimal Control of Renewable Energy Grid-connected Converters Under Unbalanced Voltage Condition

作　　者：王祺[1] 秦文萍[1] 张宇[1] 王磊[1] 韩肖清[1] 王鹏[1] WANG Qi;QIN Wenping;ZHANG Yu;WANG Lei;HAN Xiaoqing;WANG Peng(Shanxi Key Laboratory of Power System Operation and Control(Taiyuan University of Technology),Taiyuan 030024,Shanxi Province,China)

机构地区：[1]电力系统运行与控制山西省重点实验室(太原理工大学),山西省太原市030024

出　　处：《电网技术》2020年第11期4337-4346,共10页Power System Technology

基　　金：国家重点研发计划(2018YFB0904700);山西省科技重大专项项目(20181102028)。

摘　　要：电网电压不平衡会影响并网逆变器稳定运行,且往往伴随着过流现象。传统控制方法通过调节电流指令值使并网电流维持在额定电流以内,然而,限流会使并网有功出力受限,变换器表现出低韧性状态,严重时会造成电网有功缺额甚至电网解列。针对上述情况,该文分析了不平衡工况下交直流侧谐波的交互影响,考虑变换器并网电流谐波、功率波动、直流侧电压波动等约束条件,绘制了在并网标准的约束下变换器运行的韧性区间,根据韧性区间选取了满足约束条件下的韧性最优点,进而提出一种提升变换器有功功率输出能力的优化控制策略。以功率在允许范围内波动为代价,提升了并网变换器的有功输出,同时兼顾了传统控制策略的控制目标的实现及限流功能,强化了并网变换器在不平衡电网情况下的韧性,仿真和实验验证了所提方法有效、可行。The unbalanced voltage condition will affect the stable operation of the grid-connected inverter which is often accompanied by an overcurrent phenomenon.The traditional control method keeps the grid-into current within the rated current by adjusting the current reference value.However,the current limitation restrains the grid-connected active power which will lead to a low-toughness state of the inverter.In severe cases,it may cause an active power shortage and even grid delinking.In view of the above situations,this paper proposes an optimization control strategy to improve the converter’s active power output capability.First,the interaction effects of AC and DC side harmonics under unbalanced voltage conditions are analyzed with the dynamic phasor method(DPM).Considering the constraints of grid-into current harmonics,power fluctuations,and DC side voltage fluctuations,the toughness interval of converter operation is then illustrated under the constraints of grid standards.With the power fluctuation within the allowable range,the active power output of the grid-connected converter is improved,while the control objectives of the traditional control strategy and its current-limiting function are realized.The toughness of the grid-connected converter is strengthened in an unbalanced power grid situation.Simulation and experiments verify that the proposed method is effective and feasible.

关 键 词：电压不平衡 并网变换器 韧性 谐波 有功输出能力 

分 类 号：TM721[电气工程—电力系统及自动化]