PureWave AVC^® Adaptive VAR Compensator

How It Works

The PureWave AVC is installed in parallel with the dynamic load, as shown in the block diagram below, and continuously monitors line-to-neutral voltage and current on each phase of the feeder serving the load. By measuring the peak magnitude of the inductive component of the current-at the zero crossing of the corresponding line-to-neutral voltage waveform-the microprocessor controller determines the capacitive compensation necessary to maintain either the voltage or power factor. The appropriate reactive power is then injected into the system by closing the power-electronic switch during the following cycle. Utilizing an array of sophisticated algorithms, a response time close to ½ cycle (8.3 milliseconds for a 60-Hertz system) is achievable.

The capacitors are always charged and ready until the triggering signal is applied to the power-electronic switches. Switching is synchronized to occur at peak system voltage-at the natural zero crossing of the capacitor current, when the voltage across the power-electronic switch is near zero. As a result, the transients normally associated with capacitor switching are eliminated.

Each phase of the feeder is independently compensated, making the PureWave AVC ideal for application on unbalanced systems. This is an extremely important consideration, as the compensation required on a cycle-by-cycle basis is most often different for each phase.

The microprocessor controller updates the capacitor switching pattern up to every half-cycle and sets the optimum firing sequence of the power-electronic switches. Complete communication, display, and diagnostic capabilities are included.