Real-time digital simulation of power electronic apparatus interfaced with digital controllers

This paper presents a new approach for the real-time digital simulation of power electronic controllers in power systems. Digital controllers for power electronic systems present a problem when testing in real-time using a digital simulator due to the discrete nature of their outputs which are not necessarily in synchronism with the time step of the simulator. The proposed algorithm combines the variable step-size numerical integration method with linear interpolation for the synchronization of a real-time digital simulator and a digital controller. It is shown that lack of such synchronization leads to inaccurate simulation results, specifically with regard to the fundamental and harmonics of the voltage and current signals. Sampling theory is used to model the interaction between a digital simulator and a digital controller. A Pulse Width Modulated (PWM) Voltage Source Converter (VSC) based reactive power compensator system is used as an illustrative example for the simulation.