Abstract
This paper proposes a pulse width modulation (PWM) strategy for improving the efficiency of a 5-level H-bridge T-type neutral point clamped (TNPC) inverter. In the case of the proposed PWM strategy, unlike the conventional PWM strategy in which both of the switching legs of the H-bridge inverter operate at a high frequency, one switching leg of the inverter operates at a low frequency. As the switching frequency is lowered, the switching loss is reduced, this improving the efficiency of the system. The duty references for the switching legs and the operating principle of the inverter are described in detail. The proposed PWM strategy, however, causes distortion of the output filter inductor current. The cause of the distortion has been analyzed and a compensation method is proposed to mitigate the distortion of the current. The effect of the proposed PWM strategy can be predicted through the loss calculation of the inverter for each modulation strategy. Furthermore, current distortion mitigation obtained by compensation method is confirmed through the simulation. In order to verify the effectiveness of the proposed strategy, a 2 kW H-bridge TNPC inverter prototype is implemented and tested. The simulation and experimental results show that the efficiency of the inverter is improved when the proposed PWM strategy is applied.
Highlights
As power consumption has increased recently, the power density of power electronic systems has become a major concern for researchers
[23], is applied to the simulation model to compare the results show that the efficiency of the 5-level H-bridge type neutral point clamped (TNPC) inverter is improved by applying the losses of the inverter for each
The 5-level H-bridge TNPC inverter shown in Figure 1 was implemented in PSIM 11.1.3 from
Summary
As power consumption has increased recently, the power density of power electronic systems has become a major concern for researchers. Studies focused on efficiency improvement and reducing the volume of the system have been carried out to maximize power transfer. Most inverters used in renewable energy systems, energy storage systems (ESS), uninterruptible power supply (UPS), and solid-state transformers (SST) adopt the topology of a 2-level inverter [1,2,3,4,5,6,7]. If the inverter topology is changed to a 3-level inverter, a filter size that is smaller than the output filter size of a 2-level inverter can be designed, reducing the size of the entire system. Examples of a 3-level inverter, such as neutral point clamped (NPC) inverter [8,10], T-type neutral point clamped (TNPC) inverter [11], and flying capacitor inverter [12] have been studied and widely used
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