ACTIVE GRID FILTER

Harmonic and Reactive Current Cancellation with PQF

Application for Single-phase and 3 Phase.  From 100kVA up to  3MVA.

Reactive and harmonic current control of  reduced power factor and low efficiency.  In order to eliminate these problems, a parallelly operating inverter-system can be used to shape the current to a sinusoidal waveform and to increase power factor. 

The principle of active grid control is based on measuring the harmonic currents and compensating them by current injection in the opposite phase. The compensating current is created by PWM of a two- or three- phase IGBT inverter and a DC capacitor bus. The inverter is connected to the grid by coils and a small filter circuit.

In contrast to traditional capacitor circuits, the reactive compensation by active-control is operating continuously without transients and switching distortions, and the fast reaction guarantees high quality of power. The compensation can be either capacitive or inductive according to the requirements of the application.

Example of a three phase active compensator

The graphs show a three phase grid connected to a non-linear load. The harmonic and reactive currents of the load are compensated.