Real-time digital simulation of switching power circuits

Sophisticated power electronic apparatus and their digital control systems are finding increasing applications in electric power systems at generation, transmission, distribution and utilization levels. It is essential to carry out rigorous performance evaluation of the power electronic equipment and their digital controllers prior to their commissioning on the host power system. The current trend to achieve that goal is to interface a real-time digital simulator representing the power electronic apparatus and the host power system with the digital controller. This thesis addresses the issue of synchronization between the output signals of the digital controller for firing power electronic switches and the discrete time-step of the real-time simulator. It is shown that lack of such synchronization can lead to severe inaccuracies in the simulation results.; A novel real-time simulation algorithm is proposed for accounting incoming switching events in fixed step-size digital simulation. This algorithm relies on the registration of the timing of the switching events and a subsequent correction procedure to calculate the system state. Off-line time domain simulations of a Pulse Width Modulated (PWM) Voltage Source Inverter (VSI) system demonstrate a ten-fold improvement in accuracy of the proposed algorithm over the fixed step-size algorithm using the same step-size. Practical feasibility of the proposed algorithm is demonstrated by implementation on a digital computing platform comprising of a DSP and a FPGA. The hardware and software design process follows a modular approach which makes it amenable for implementation on next generation processors. A 5kVA experimental set-up of the PWM VSC system is used to verify the results of the real-time simulation.