A Novel RMS Voltage Control Method for UPS Applications

In this study a new RMS control technique is proposed for Uninterruptible Power Supply (UPS) output voltage control. In contrast to the traditional RMS value calculation, which is carried out in each mains period, the proposed method allows continuous updating, so that an instantaneous RMS value is obtained. The moving RMS value is used in the controller. The output voltage response to sudden load changes is improved. The traditional and the proposed control methods are simulated with MATLAB and experimental results are taken. The theoretical and experimental results were found to be in good agreement. The proposed method can be used in UPS applications supplying critical and pulse loads such as CNC machines, MRI devices, tomography devices, punch machines and spotwelding machines. The proposed method requires calculation of the root main square value at every sampling period. RMS voltage error values in two different control methods are given. It is seen that the proposed method has a superior response in case of sudden load changes.