Designing 3-phase inverters with Δ/Y output isolation transformer

3-phase inverters with isolating output transformer are capable of eliminating 3^rd and 9^th symmetrical harmonics of nonlinear loads, without any complicated controller. This fact has been realized in this paper by defining the proper value for leakage inductance of 3-phase Δ/Y transformer. In the controller of such an inverter, which includes an internal inductance-current loop and an external voltage loop, voltage regulation and also THD minimization is achieved by only using resonant compensators for the 1^st, 5^th and 7^th harmonics. Simulation results for a 40kw inverter show that at the maximum nonlinear load, output voltage THD is below 4.8% and maximum 3rd harmonic value is 2.5%. Moreover, load and line regulation factor is better than 0.75%, which meets the IEC64020-3 standard requirements.