VOLTAGE BALANCING USING SWITCHED CAPACITORS

Thyristor switched capacitors (TSCs) are a useful means of load balancing and reactive power support. The control of a general load by a binary weighted switched capacitor system is discussed in this paper along with a simple control scheme where the capacitor bank across a line pair is adjusted to control the fundamental voltage magnitude for that line pair. In a three-phase three-wire system, it is shown that an ideal reactive source can control positive sequence magnitude and cancel any negative phase sequence terms. With the quantized control levels available in a TSC, a ramping scheme with input hysteresis is shown to be effective in balancing in simulations and in a laboratory test with three banks in each phase. Low transient switching is employed with binary weighted capacitor banks to give a smooth variation of the reactive power supplied.