基于多绕组调节模式的变压器式可控电抗器谐波电流优化

Harmonic Current Optimization of Controllable Reactor of Transformer Type Based on Multi-Winding Regulation Mode

变压器式可控电抗器(controllable reactor of transformer type,CRT)目前的调节模式仅限于单绕组调节模式,此时CRT的谐波电流含量无法满足要求更高的应用场合。为进一步改善CRT的谐波性能,提出了多绕组调节模式的基本概念;采用分段线性化的方法,推出CRT工作绕组瞬时电流的计算通式;利用傅里叶级数分析方法求得工作绕组电流基波及各次谐波分量有效值与各触发角之间的函数关系式。将CRT整个容量范围进行离散,依次以各离散容量点为等式约束,以CRT向电网注入的谐波电流含量为目标函数,建立非线性优化模型,并调用Matlab中的求解非线性约束最小化问题的函数(Fmincon)逐点求解,从而实现了CRT的谐波优化调节模式。算例分析显示谐波优化调节模式的谐波性能明显优于目前公认的谐波性能最好的固定单支路调节模式。最后借助CRT等值电路仿真模型指出文中提出的谐波优化方法的本质是基于谐波对消原理,在相控方式下,"对消"原理比已有的"稀释"原理能够更显著地减小CRT注入电网的谐波含量。

Regulation mode of controllable reactor of transformer type （CRT） at present is restricted to single winding regulation, and corresponding harmonic current content cannot meet higher requirements. To further improve harmonic characteristic of CRT, concept of multi-winding regulation mode is proposed, and formula for calculating working winding＇s instantaneous current is obtained by means of subsection linearization, then functional relationships between working winding＇s fundamental and harmonic current RMS and all control windings＇ triggered angles are acquired with Fourier series. Discretizing the range of CRT output power, nonlinear optimal model is built, which contains objective function of the harmonic current content injected into power grid and equality constraint for each given output power. Solving optimal models based on different output powers by calling Fmincon algorithm which can find minimum of constrained nonlinear multivariable function in Matlab, harmonic optimization regulation mode is obtained. Example shows that the proposed harmonic optimization regulation mode has much better harmonic characteristic than fixed-single-branch regulation mode recognized as the best harmonic characteristic at present. Simulation result obtained using equivalent circuit of CRT presented in relevant literatures indicates that harmonic optimization method described in this paper takes full advantage of harmonic offsetting, decreasing harmonic current injected into power grid more significantly than traditional method based on harmonic dilution.