A Three-Phase PWM Inverter For Double Conversion UPS That Complies With the Standard IEC 62040-3

This paper proposes an improved digital voltage controller suitable for three-phase PWM inverters with output transformer for medium and high power uninterruptible power supplies (UPS). The proposed controller is derived from the internal model principle using a state-variable approach in stationary alphabeta frame. With this controller it is possible to obtain a high performance in both steady-state and load transients. In addition, with the selected internal model, DC components result from real circuit implementation non-idealities are not amplified avoiding in this way, the transformer saturation. The UPS output voltages have reduced total harmonic distortion (THD) for both balanced and unbalanced non-linear loads. Regarding the transient performance, load steps responses are improved with the proposed digital controller and as a result the UPS compliant with the classification 1 of the international standard IEC 62040-3. In order to validate the proposed digital controller and to demonstrate the steady-state and transient performance, experimental results from a 10 kVA space vector modulated three-phase inverter, fully controlled by a DSP TMS320F241, are presented