Synthesizing variant impedances in SPICE. A fast solution for power electronics and electric power systems simulations

The Simulation Program with Integrated Circuit Emphasis (SPICE) is a program widely used to simulate electric circuits. Characteristics such as versatility, large component libraries, integration of schematic edition, simulation and analyses have made it popular. As many students use this program early on, there is a natural tendency to continue using it in power electronics, electrical drives and electric power system courses. SPICE was initially developed to simulate integrated circuits. Therefore, sometimes the program parameters and components must be adapted to power circuits and systems. For example, the tolerances and component parameters have to be changed. Variant impedances frequently are present in electrical/electronic circuits. For example, an incandescent bulb is a power-variant resistance. A thermistor is a resistance that varies according to the temperature. An ideal thyristor controlled reactor (TCR), used to control voltage in electric power systems, is a variable inductance that changes its value depending on a control signal. A thyristor controlled series capacitor (TCSC) or a static reactive power compensator are ideally modeled as variable capacitances. Simulating such circuits requires defining the sub-circuits that, at their terminals, behave like the desired variant impedance.