On the Explicit Relation between Mains-Side Current THD and DC Link Voltage Controller Gain in Grid-Connected Converters

It is known that attainable DC link voltage loop bandwidth in grid-connected converters is limited due to trade-off with AC-side current total harmonic distortion (THD). The letter reveals that THD requirement inflicts the value of DC link voltage controller gain only at double-grid frequency. On the other hand, the desired phase margin poses another restriction on the controller performance. As a result, if a typical PI compensator is employed, two abovementioned performance merits impose DC link voltage loop dynamics. The letter concludes that dynamic performance may be improved without deteriorating grid-side current quality by adding a degree-of-freedom to compensator structure so that the loop gain magnitude at double-grid frequency and the crossover frequency are decoupled. Experimental results validate the revealed findings.