弱电网下采用SVC与SVG补偿后新能源并网变换器的功率传输特性分析

在大规模新能源集中接入电网时,因弱电网线路的无功消耗会导致新能源并网点电压下降。为保证新能源的有效送出,在新能源并网点会集中接入SVC/SVG等无功补偿装置。然而,无功补偿对新能源并网变换器在弱电网条件下功率传输能力的提升力度及关键影响因素尚不明确。该文以新能源并网变换器为研究对象,首先分析它在不考虑无功补偿条件下并入弱电网时的功率传输特性,并重点探讨其极限输出功率的形成机理及其关键影响因素;其次,分析所接入的2种典型无功补偿装置(静止无功补偿器(static var compensator,SVC)和静止无功发生器(static var generator,SVG))的工作机理,研究考虑无功补偿后新能源并网变换器的功率传输特性,并分析其极限输出功率与短路比、无功补偿装置容量、无功补偿装置类型的约束关系;最后,通过MATLAB/Simulink仿真验证论文理论分析的正确性。

Analysis of Power Transmission Characteristics of Renewable Energy Grid-connected Converter Considering SVC and SVG Compensation Under Weak Grid Condition

When the large-scale renewable energy is connected to the power grid, the reactive power consumption of the weak current network will lead to voltage drop of its parallel network. To ensure the effective delivery of renewable energy, static var compensator/static var generator(SVC/SVG), and other reactive power compensation devices will be centrally connected to the common coupling point(PCC). However, it is not clear how much the reactive power compensation device improves the power transmission capacity of the renewable energy grid-connected converter under the condition of weak grid and the influencing factors. In this paper, the renewable energy grid-connected converter was taken as the research object. Firstly, its power transmission characteristics when it is connected to the weak grid without considering reactive compensation were analyzed, and the formation mechanism and key factors of the limit output power of renewable energy grid-connected converter were discussed. Secondly, the working mechanism of two kinds of typical reactive power compensation devices(SVC and SVG) was analyzed, the power transmission characteristics of renewable energy grid-connected converter considering reactive power compensation were studied, and the constraint relationship between its limit the output power and short circuit ratio(SCR), the capacity of reactive power compensation device, and type of reactive power compensation device was analyzed. Finally, Matlab/Simulink simulation was used to verify the correctness of the theoretical analysis.