Research on Fault Tolerance Control of Cascade STATCOM with LCL filter

Abstract

In order to improve operating reliability of cascade STATCOM (6KV, 8Mvar) with LCL filter, and on the foundation of an accurate diagnosis on device faults, the paper makes adjustments to soft and hard structures of cascade STATCOM. It is done to guarantee that the device can run in a steady and reliable way even when it has fault. The paper solves problems of fault tolerance control with the combined approaches of analytical redundancy and hardware redundancy (with tier-one redundancy), and also incorporates PWM modulation strategy and the phase-to-phase or in-phase capacitor voltage balance control strategy into frame, both of which need to be put into fault tolerance control. When some parts of the device fails, the main circuit is isolated from the fault model by blocking drive pulse and bypass mechanism. Finally, fault diagnosis and fault tolerance control combine with each other seamlessly. The simulation and the experimental results show together that fault tolerance control has a good effect on dynamic compensation and allows the device to respond promptly.