Control of digital AVR in stand alone generator for improved dynamic characteristics

AC brushless generator combined diesel engine is much used for the power supply equipment due to the stability and maintenance. At the starting of AC brushless generator, the output voltage from residual flux of a generator is very small. So, the AVR(automatic voltage regulator) should wake up with the low starting voltage. And the starting voltage is very low, it´s very difficult to excite the generator fully, and needs a well designed self- starting sequence. Furthermore, AVR uses rms voltage information from output terminal. This information has some time-delay for the filter and signal processing. The dynamic performance of conventional PID controller is degraded at sudden load change, because of the time-delay. This paper presents digital AVR in stand-alone generator combined with diesel engine using low voltage self-starting circuit and instantaneous voltage detector. The proposed low voltage self-starting circuit operates at the generator starting, and is stopped when the control power of AVR system is stable. During soft-start, only self-starting circuit feeds the power forwards to generator in order to build-up the rated voltage generation. The instantaneous voltage detector and limit comparator select the control signal of exciter current controller. In order to get a fast dynamic response, the proposed instantaneous voltage detector and limit comparator adjusts the PWM signal. The proposed digital AVR excitation system is tested for performance compensation.