Analytical calculation of the RMS current stress on the DC link capacitor of voltage DC link PWM converter systems

In this paper a simple analytical expression for the current stress on the DC link capacitor of a voltage DC link converter system, as caused by the load-side inverter is derived. There, a sinusoidal inverter output current and a constant value of the DC link voltage are assumed. The DC link capacitor current RMS value is determined by the modulation depth and by the amplitude and the phase angle of the inverter output current. Despite the neglection of the output current ripple the results of the analytical calculation match very well with a digital simulation even if the output current ripple is relatively high as given, e.g., for low-frequency IGBT inverter systems. Thus, the approximation can advantageously be used for designing the DC link capacitor of PWM converter systems.