Power eletronics

224

Journal of Power Electronics, Vol. 5, No. 3, July 2005

JPE 5-3-8

A Three Phase Three-level PWM Switched Voltage Source Inverter with Zero Neutral Point Potential
Won-Sik Oh*, Sang-Kyoo Han*, Seong-Wook Choi* and Gun-Woo Moon†

†*

Dept. of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology, Korea

ABSTRACT A new three phase three-level Pulse Width Modulation (PWM) Switched Voltage Source (SVS) inverter with zero neutral point potential is proposed. It consists of three single-phase inverter modules. Each module is composed of a switched voltage source and inverter switches. The major advantage is that the peak value of the phase output voltage is twice as high as that of a conventional neutral-point-clamped (NPC) PWM inverter. Thus, the proposed inverter is suitable for applications with low voltage sources such as batteries, fuel cells, or solar cells. Furthermore, three-level waveforms of the proposed inverter can be achieved without the switch voltage imbalance problem. Since the average neutral point potential of the proposed inverter is zero, a common ground between the input stage and the output stage is possible. Therefore, it can be applied to a transformer-less Power Conditioning System (PCS). The proposed inverter is verified by a PSpice simulation and experimental results based on a laboratory prototype. Keywords: multi-level inverter, switched voltage source

1. Introduction
In recent years, industry has begun to demand higher power equipment. Multi-level inverters have been attracting increasing attention for power conversion in high-power applications due to their lower harmonics, higher efficiency, and lower voltage stress compared to two-level inverters. Numerous topologies for multi-level inverters have been introduced and widely studied[1-5]. The most important of these topologies, as shown in Fig. 1, are the diode-clamped (neutral-point-clamped) inverter[6], the capacitor-clamped