In this paper, a power electronics controller implemented on one field-programmable gate array (FPGA) chip is proposed. The FPGA-based power electronics controller integrates the whole signal processing system including synchronous reference frame (SRF) algorithm, decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL) and hysteresis pulse-width modulation (PWM). It is applicable to three-phase four-wire hybrid active power filters (HAPFs), which use four-leg voltage source inverters (VSIs). Different from the conventional controller using instantaneous reactive power theory, the proposed controller could work when source voltages are unbalanced. The bit width and I/O ports of the FPGA-based controller are user-defined. Hence, the proposed FPGA-based controller is more flexible than those using digital signal processors (DSPs). Parallel processing in FPGA could also achieve a faster control. The prototype of a three-phase HAPF is built and the proposed FPGA-based controller is adopted. Experimental results are provided to show its validity.