H. Okyere, H. Nouri, T.S. Davies, and R. Mukedkar (UK)
Micro-Controller, STATCOM, Multi-level Inverter, Reactive Power Compensation
The purpose of this paper is the design and study of a laboratory based five-level voltage sourced inverter (VSI) used in STATCOM to prevent voltage collapse. It primarily focuses on the application of microcontroller and microprocessor based, communication, and the control systems requirement for the STATCOM. Microcontrollers are used to generate the switching signals to drive the IGBTs (the switching device used in this study) drivers to generate quasi-sine wave voltage form. The control of the reactive and real power to prevent voltage collapse is achieved by using microprocessor based proportional and integral (PI) control and line synchronisation to charge or discharge the dc link capacitor, which serves as voltage source for the inverter. This allows the output voltage of the STATCOM to exceed or fall below that of the system voltage. The design also focuses on the communication using asynchronous serial communication and a designed protocol used in linking the various microcontrollers and the microprocessor to work in homogeneous way to achieve the required voltage level, harmonic content requirement of the voltage and the current drawn. The results to date suggest that the designed and its associated electronics control could be used successfully in a typical 415V distribution system. The main benefits of the chain circuit topology used in the VSI are: fast response to voltage changes in the system, able to increase the voltage level to that of the system to be able to use an inductor instead of a transformer to couple the two systems to reduce cost, able to achieve the specified harmonics in voltage generated and current drawn through out it full range of operation.
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