Four-switch three-phase SEPIC-based inverter

Four-switch three-phase (FSTP) inverter has been proposed as an innovative inverter design to reduce the cost, complexity, size, and switching losses of the DC-AC conversion system. Traditional FSTP inverter usually operates at half the DC input voltage, hence, the output line voltage cannot exceed this value. This paper proposes a novel design for the FSTP inverter based on the topology of the single-ended primary-inductance converter (SEPIC). With this topology, the obtained output voltage is a pure sine-wave without a need of an output filter. Compared to the traditional FSTP inverter, the proposed FSTP SEPIC inverter improves the voltage utilization factor of the input DC supply, where the obtained output line voltage can be extended up to the full value of the DC input voltage. For the purpose of optimizing the dynamics of the proposed SEPIC inverter while ensuring correct operation in any working condition, a sliding-mode controller is applied. Derivation of the equations describing the operation of the SEPIC converter based on state space analysis, validation through simulations in MATLAB/SIMULINK and experimental results on a laboratory setup are presented in this paper.