Description

In this proposed implementation design is a three-phase transformerless cascade pulsewidth-modulation (PWM) STATic synchronous COMpensator (STATCOM) intended for installation on industrial and utility power distribution systems. It proposes a control algorithm that devotes itself not only to meeting the demand of reactive power but also to voltage balancing of multiple galvanically isolated and floating dc capacitors. The control algorithm based on a phase-shifted carrier modulation strategy is prominent in having no restriction on the cascade number. Cascade STATCOMs can be classified into staircase modulation and pulsewidth modulation (PWM) in terms of voltage control. In this proposed design is based on PWM. The ac voltage of the STATCOM is almost sinusoidal, so that it requires no harmonic filter. Each converter is equipped with a capacitor and a voltage sensor on the dc side, which are electrically isolated from each other. The STATCOM has the capability of self-starting and voltage-balancing without any external power supply or equipment. Thus results prove the stable operating performance of the proposed method in steady states and transient states.