Abstract
In a three-level (NPC) converter, the voltage imbalance problem in the DC-link capacitors is major issue. This paper proposes the DC-link capacitor voltage imbalance compensation method, where a common offset voltage is injected for a multi-module NPC inverter. The offset voltage consists of a harmonic voltage and a voltage difference between the upper and lower capacitors. The proposed method does not require any hardware modification, so that it is easily implemented. In order to show the effectiveness of the proposed balancing method, theoretical analysis is provided to balance the voltages, and both the simulations and the experiments were carried out to show that the voltage difference of the DC-link was decreased by the proposed method.
Highlights
In DC distribution systems, multi-level topologies have been considered because of the electrical characteristics of high voltage (HV) or medium voltage (MV) applications [1,2,3,4,5,6,7,8,9]
NPC inverters, order to verify the DC-link capacitor balancing for multi-module ainverters, 3-kW simulation model has been configured by using
This paper described the DC-link capacitor voltage error compensation method for multi-module
Summary
In DC distribution systems, multi-level topologies have been considered because of the electrical characteristics of high voltage (HV) or medium voltage (MV) applications [1,2,3,4,5,6,7,8,9]. Three-level neutral-point-clamped (NPC) inverters have been widely used in MV and HV applications. Compared with two-level inverter systems, three-level NPC inverters have some advantages. NPC inverters have less harmonic component on output current. NPC inverters can use low level switches because of the dv/dt value on switching devices during switching operation, which is half of the two-level inverter. NPC inverters have lower voltage stress than two-level inverters. NPC inverters have a major drawback associated with the neutral-point voltage
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