The study on control technique of multi-function feedback electronic load

This paper presents an implementation method for 40 KVA feedback electronic load with multiple functions. It designs the circuit of control unit and researches on the control technique. The control unit is designed with LPC2136 and CPLD as the core. Through the Direct Digital Synthesis approach we get sine wave with low frequency and triangular wave with high frequency, and generate the SPWM wave by use of analogue technique. Using 6-channel high speed and high accuracy ADC we implement synchronous detection to the input, output power signal and the internal electric source signal of the electronic load to realize the ability of speed setting and feedback. The control unit also has the ability of monitoring input and setting the work status. With these abilities, it allows real-time processing of the fault. This paper provides a digital PID adjustment method with constant current and power setting mode, which explains the control characteristic of the electronic load when it works under power source with high-power and frequency conversion, power switch and transformer with high power. The method presented in the paper has been successfully applied to 40 KVA electronic load equipment with power factor adjustment, which allows event triggering and can save 90% power dissipation.