A Novel Power Balancing Technique in Neutral Point Clamping Multilevel Inverters for the Electric Vehicle Industry under Distributed Unbalance Battery Powering Scheme

In electric vehicle (EV) application, three phase neutral point clamped multilevel inverter (NPC-MLI) is fed by parallel-series compound connected battery sets. Reaching a better and more reliable power utilization and management, in the proposed configuration, each phase is to be supplied by an individual dedicated battery set. However, such configuration will result in phase imbalance current due to the difference in the state of charge (SoC) of each battery set. Therefore, a new modified power imbalance mitigation is also introduced in this paper without adding any extra voltage or current sensors. A solution of the power imbalance between the phases is presented if separate DC sources is connected to each phase of the NPC-MLI. Consequently, phase imbalance compensation technique is used to update the modulating signal, which balances the output power delivered to the motor without any extra sensors or control complications. The phase imbalance compensation technique is used to modify the modulating index, which balances the individual phase's power delivered to the non-linear drive with no need for extra hardware for sensors or control loop add-on modifications. In summary, the system will adjust itself inherently and in an adaptive way. A MATLAB simulation model and laboratory prototype are constructed to provide the proof of the validity of the proposed configuration.