Methods of unbalanced voltage control in nonsolidly grounded systems based on current injection

Abstract

SummaryIn nonsolidly grounded systems, 3-phase voltage imbalances endanger the system safety. On the basis of the principle of unbalanced voltage control through injecting current, the variation of unbalanced voltage along with the injected current's amplitude and phase was studied. Three practical closed-loop unbalanced voltage control methods are given, such as the 2-point method, the tracking method, and the synthetic method. The synthetic method combines the advantages of the 2-point method and the tracking method and is fast to control with a high precision. Compared with traditional methods, the proposed methods advance in means such as higher precision, more flexible control, less investments, and better adaptation in systems with dynamic changes. The methods are verified in designed simulation.