Design Guidelines for Active Power Filters Operating in Disturbed Industrial Environments

Regenerative testing systems of AC–AC industrial power converters (diode or thyristor rectifier and inverter) at the end of the production line are common solutions to reduce the energy drawn from the grid during the testing. However, they inherently introduce severe harmonic distortion, causing disturbances for all local loads. Shunt-type active power filters (APFs) are widely adopted to mitigate these issues. Since the APF is an add-on for the testing system in mass production facilities, it must be cost effective and with high efficiency for not affecting the overall losses for the testing. Moreover, higher switching frequencies are often used to reduce grid-interfacing filter size, further impacting APF efficiency. As the industrial environments are highly disturbed, the APF operation must be extremely robust against these disturbances. In light of the aforementioned issues, this article provides guidelines for the design of an APF intended to operate in an industrial environment characterized by significant electrical disturbances. In particular, the article demonstrates how the adoption of a dedicated discontinuous pulsewidth modulation (DPWM) technique for APFs, namely APFGDPWM, allows minimizing the impact of the APF on power line consumption and reducing the stress on the APF semiconductors and on the filters for grid interfacing. Unlike other DPWM strategies in the literature designed for APFs, APFGDPWM proves to be robust against high frequency disturbances circulating on the power lines. Moreover, a design procedure for the differential mode (DM) LCL filter is proposed and used to build two distinct prototypes: an APF implementing space vector pulsewidth modulation (SVPWM) and an APF using APF-GDPWM. Experimental tests are conducted on an industrial prototype (TRL 9), 100 kVA two-level APF interfaced to the grid through the previously designed DM LCL filters, while compensating for the distorted input current of a regenerative system testing 260 kVA power converters