Study of the Steinmetz Circuit Influence on AC Traction System Resonance

Traction systems are single-phase, nonlinear loads, which can unbalance and pollute supply voltages. To reduce voltage unbalance, reactances are usually connected in delta configuration with traction systems. This setup is called the Steinmetz circuit. Parallel and series resonances can occur between the Steinmetz capacitor and system inductors, increasing voltage distortion. Thus, it is important to analyze the parallel resonance “observed” from the traction system to avoid harmonic problems due to its injected harmonic currents. This paper studies this resonance analytically and presents simple expressions to locate it. Experimental measurements are also provided to validate the obtained analytical results. These expressions are also used to analyze resonance in several power systems in the literature.