High-performance Active Filters using Selective Harmonic Control

The paper discusses the application of selective harmonic compensation for parallel active power filters based on current controlled inverters. A method based on closed-loop synchronous frame control of line currents is presented and compared with conventional, possibly selective, load current detection methods. Indeed, in active filter applications where distorting loads absorb slowly varying harmonics, the compensation of selected harmonics gives several advantages, such as rating optimisation, improved performance and robustness. In fact, the aforementioned methods are able to compensate for the inverter control, achieving full compensation on the selected harmonics, and to increase the stability margin of the system in case of capacitive or resonant loads. Experimental results of both control algorithms on a 5 kVA converter prototype confirm effectiveness and advantages of selected harmonic compensation.