A Grid-Voltage-Sensorless Resistive-Active Power Filter With Series LC-Filter

Voltage-sensorless control has been investigated for voltage source inverters (VSIs) for many years due to the reduced system cost and potentially improved system reliability. The VSI-based resistive-active power filters (R-APFs) are now widely used to prevent the harmonic resonance in power distribution network, for which the voltage sensors are needed in order to obtain the current reference. In this paper, a grid-voltage-sensorless control strategy is proposed for the R-APF with series LC-filter. Unlike the traditional resistance emulation method, this proposed control method reshapes the output impedance of the R-APF at the harmonic frequencies, which is independent of the current reference. A fundamental grid-voltage estimation method is also proposed to control the dc-link voltage. The performance of the proposed control method is verified in both simulations and experiments. The results show good accuracy of the emulated resistance and functionality of the dc-link voltage control. With the proposed method, the cost of the R-APF can also be reduced with potentially improved system reliability.