Network Unbalance Compensation Comparison: Conventional pq Theory vs the General Power Theory

Compensation for harmonics and unbalance has become increasingly important to improve power quality, for load balancing and avoid loss of revenue. However, conventional converter control strategies use power theories that are based on the reactive power concept which has no physical interpretation. The general power theory (GPT) is formulated without reactive power and can calculate optimal compensation currents to deliver power with minimum losses. In this paper, a controlled current source was used to inject compensation currents calculated using the pq theory and the GPT in a simple two-bus network. Compared against the pq theory, delivery losses were reduced to a minimum using the GPT. Unbalance was reduced with pq-compensation whereas the GPT completely eliminated the unbalance. These findings validate the optimized approach of the GPT. The implications of the study are more efficient power electronic converter design and control, optimized billing without unnecessary charges, and representative voltage stability analysis.