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链式变换器适合于实现中高压无变压器直接并网,然而取消变压器通常会导致直流分量超标。特别在中高压应用场合,常采用电流互感器采样并网电流,其隔直效应将进一步导致输出直流分量不受控。建立含电流互感器的链式STATCOM系统模型,分析电流互感器导致直流分量放大的机理,提出一种基于直流侧电压纹波检测的并网电流直流分量抑制方法,并给出该方法的原理和设计原则。在一台25电平的链式STATCOM实验平台上验证该方法的可行性,实验结果表明,该方法即使在采样环节无法直接采集直流电流的条件下,也可有效抑制并网电流直流分量。
Chassis converters are suitable for direct and medium voltage transformers without grid connection, however the elimination of transformers usually leads to excessive DC components. Especially in medium and high voltage applications, current transformers are often used to sample grid-connected current. The blocking effect will further result in uncontrolled output DC components. A chain STATCOM system model with current transformer was established to analyze the mechanism of DC component amplification caused by current transformer. A method to suppress DC component of grid-connected current based on DC voltage ripple detection was proposed. The principle and Design Principles. The feasibility of this method is validated on a 25-level chain STATCOM experimental platform. The experimental results show that this method can effectively suppress the direct current component of grid-connected current even though the direct sampling current can not be collected directly.