| Abstract |
This paper presents a design and an implementation of inverters with ultra-low total harmonic distortion (THD) under all kinds of loads. In this study, the ultra-low THD objective is achieved by combining theadvantages of the repetitive controller, the predictive-PID controller and the reference signal feedforwarding method in a multi-loop structure. The high performance uninterruptible power supply(UPS) and the transformer test converter applications where the ultra-low THD is desired require theuse of high performance controllers. This study successfully achieves the design of such a controller bymeans of computer simulation, which is based on the true model of the inverter system. The tuning ofthe controller and inverter parameters made through simulation has yielded a successful hardware designand a good performance during the experimental tests. The performance of controller is evaluated interms of output voltage waveform distortion under actual linear and nonlinear loads. The experimentalresults that demonstrate the success of the controller are obtained from the voltage source inverters (VSI)built for a three-phase UPS application at 30 kVA and a transformer test converter application at 300kVA. The maximum measured THD is less than 2.88\% under the worst nonlinear load case. Theconverters employing the designed controller are currently in use with success in the field. |
