DC Voltage Reduction in PV connected LV D-STATCOM with In-Phase Series Voltage Injection and Improved Transformer Ratings

Abstract

This paper deals with DC voltage reduction in shunt compensator for non-linear and reactive loads. A novel converter topology-control combinations is proposed to reduce the DC-voltage requirement. The proposed configuration consists of transformer based hybrid series-shunt solution (non-isolated) with intentional series voltage injection. Such configuration will be suitable for the applications where direct line frequency transformer is used to achieve DC bus voltage reduction (like DSTATCOM connected with PV, line interactive uninterruptable power supply system etc.). The proposed solution is compared with (a) direct transformer based solution, (b) series LC filter based hybrid-active filter. The series capacitor based solution has certain operational limits for lagging loads and it does not work with leading loads at PCC. However, the proposed solution does not have such restrictions in operation for both lagging and leading loads and it is achieved at the cost of few additional power circuit components. It can be observed that for a given DC bus reduction, the size of the transformer is reduced for the proposed series voltage injection case compared to that in direct transformer coupled solutions. The concept is verified through simulation results and analysis from a three phase 440V L-L 25kVA shunt compensator. � 2018 IEEE.