Cascade Static Synchronous Compensator Research Articles

Switching transient analysis of the cascade STATCOM by the equivalent model with redundant H-bridge submodules

Cascade Static Synchronous Compensator (STATCOM) is a multilevel power electronic device, and its safety, reliability, and operation life are directly affected by switching transient processes. The work presented a switching transient analysis of the redundancy fault-tolerant control for the Cascaded STATCOM by the proposed contactor equivalent model. It was more accurate, ignoring fast dynamic changes and replacing the instantaneous speed with the average speed. Redundancy fault-tolerant control of submodules was crucial to the reliability of Cascade STATCOM. The closing and opening process of the AC contactor generally lasted for several milliseconds. When failure occurred in H-bridge, many factors such as the change of excitation circuit, the resistance, and the capacitance affected the electromagnetic transient process during the closing of the AC contactor. Arc discharge occurred when the H-bridge submodule was re-entered, and the AC contactor was turned off. Based on this, an equivalent model of ac contactor suitable for h-bridge was proposed, considering the influences of excitation circuit, arc discharge, and distribution parameters on switching transient. Simulation and experiments were used to analyze the electromagnetic transient waveform of a single H-bridge sub-module in the contactor closure and disconnection process, and the electromagnetic transient waveform of cascade STATCOM in the redundant sub-module contactor closure and disconnection process. The results showed that the transient change of the proposed model during sub module’s bypass and re-entry process was closer to the physical process. The equivalent model obtained in the work provides the theoretical and numerical basis for the design and operation of high-power power electronic equipment.

A Simplified Pulse Width Modulation Algorithm for Model Prediction of Cascade Static Synchronous Compensator

A Simplified Pulse Width Modulation Algorithm for Model Prediction of Cascade Static Synchronous Compensator

Effect of cascade STATCOM on stabilising voltage in high voltage direct current

Yongfu high voltage direct current (HVDC) project in Yunnan is the main access to send the power out and also an important part of the channel of transmission of power in west to east in China southern power grid. However, the Funing Converter Station of the project connects to a weak AC system; thus, there is a need for a Static Synchronous Compensator (STATCOM) to compensate the reactive power. This study presents the principle of the STATCOM, all kinds of the topologies of STATCOM, with their advantages and disadvantages compared to each other and the representative projects. Then, the cascade STATCOM is emphatically analysed that is applied to the project. Also, the cascade STATCOM model and the project model are established in PSCAD/EMTDC. Afterwards, the effect of STATCOM on the converter station is studied, which works in steady state and in transient of varieties of short circuit faults. Finally, the simulation results verify the effectiveness of cascade STATCOM on stabilising the voltage.

Harmonic Frequency Cascade Static Synchronous Compensator

Traditional Static Synchronous Compensator(STATCOM ) compensates most singly for reactive power or steady state voltage in high power field. On this point, the paper puts forward a harmonic frequency compensation technique, which can realize dynamic reactive power compensation as well as harmonic control of less than 20th power. Then, using average switching method, it gives the mathematical model on the device. Active and reactive current decoupling is realized. For the electrical model, the compensator developed uses 8-cascaded H bridge structure, together with the carrier phase-shifted SVM technology, can realize 17 level voltage waveform output, having high utilization and easy to realize digital. Finally, simulation and experimental results show that the harmonic frequency control technology developed for 6kV cascade compensator can be used on the actual electric network, with low switching frequency. The device can together compensate reactive power and control harmonic accurately and effectively.