In a three-phase three-wire ( 3Φ3W) converter, the average common-mode voltage between the neutral point of its ac source and the dc-source positive or negative rail over one switching cycle can be proved to be an arbitrary value. Therefore, 3Φ3W LCL (a filter that is composed of inductors, capacitors, and inductors) converters can be decoupled and controlled phase by phase in a natural frame, which results in equivalent three single-phase controls. With the single-phase control, inductance, dc-link voltage, and grid-voltage variations can be taken into account readily, yielding low-total harmonic distortion (THD) currents under distorted and unbalanced grid voltages. However, the 3Φ operations are still coupled each other and, moreover, the 3Φ filter inductances are varying with their currents simultaneously. This article presents system modeling of the decoupled digital controlled LCL converter from which coupled current tracking capability and stability of the system are investigated. Comparison between coupled and decoupled current tracking capability and stability has been verified with pole-zero plot and step response. The tracking performances of a 10 kVA with two types of feedback signals are compared and discussed. Moreover, simulated and experimental results of a 20-kVA 3Φ3W LCL grid-connected converter with wide filter inductance variation and distorted grid voltages have verified the analyses and discussions.

中文翻译：

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具有解耦控制和可变滤波电感的3Φ3W LCL变换器的耦合电流跟踪能力和稳定性分析


在三相三线（3Φ3W）变换器中，一个开关周期内交流电源中性点与直流电源正轨或负轨之间的平均共模电压可以被证明是任意值。因此，3Φ3W LCL（由电感、电容和电感组成的滤波器）变换器可以在自然框架中逐相解耦和控制，从而实现等效的三个单相控制。通过单相控制，可以轻松考虑电感、直流母线电压和电网电压变化，从而在失真和不平衡电网电压下产生低总谐波失真 (THD) 电流。然而，3Φ操作仍然相互耦合，而且3Φ滤波电感随电流同时变化。本文介绍了解耦数控 LCL 转换器的系统建模，并研究了系统的耦合电流跟踪能力和稳定性。耦合和解耦电流跟踪能力和稳定性之间的比较已通过零极点图和阶跃响应进行了验证。对具有两种反馈信号的 10 kVA 的跟踪性能进行了比较和讨论。此外，具有宽滤波电感变化和畸变电网电压的20kVA 3Φ3W LCL并网变流器的仿真和实验结果验证了分析和讨论。