Fast current controllers using FPGAs

This paper describes a FPGA (Field Programmable Grid Array) based PI controller and Pulse Width Modulator for a three-phase inverter. The signal processing circuitry is designed as a distributed pipelined architecture, consisting of several small building blocks. It is designed to be functionally equivalent to an analog PI-controller/modulator circuit. By using a high sampling rate, 1,5 MHz, the effects of sampling and delay in the feedback loop are small compared to the process time scale. The signal processing can be considered to be approximated quite closely as a continuous process, in contrast to common processor based digital implementations that have sample rates of one or two times the switching frequency. This allows for higher feedback loop gain, and shorter time constants. This gives better performance in applications like active filters, where response time is important.