A New Six-Switch Five-Level Active Neutral Point Clamped Inverter for PV Application

ABSTRACT:

 Multilevel inverters are one of the preferred solutions for medium-voltage and high-power applications and have found successful industrial applications. Five-level Active Neutral Point Clamped inverter (5L-ANPC) is one of the most popular topologies among five-level inverters. A Six-Switch 5L-ANPC (6S-5L-ANPC) topology is proposed. Compared to the conventional 5L-ANPC inverters, the 6S-5L-ANPC reduces two active switches and has lower conduction loss. The proposed modulation enables the 6S-5L-ANPC inverter to operate under both active and reactive power conditions. The FC capacitance is designed under both active and reactive power conditions. The analysis shows the proposed topology is suitable for photovoltaic (PV) grid-connected applications. A 1KVA single-phase experimental prototype is built to verify the validity and flexibility of the proposed topology and modulation method.

KEYWORDS:

1.      Multilevel inverter

2.      Active Neutral Point Clamped (ANPC)

3.      Flying-Capacitor (FC)

4.      PWM modulation

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig.1. Configuration of the proposed 6S-5L-ANPC inverter.

 EXPECTED SIMULATION RESULTS

Fig. 2. Simulation results with 310 uF FC value under unity power factor condition. (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current. (d) THD of output current.

Fig. 3. Simulation results with 310 uF FC value under reactive power operation (PF = 0.9). (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current. (d) THD of output current.

Fig. 4. Simulation results with 56 uF FC value under unity power factor condition. (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current. (d) THD of output current.

Fig. 5. Simulation results with 56 uF FC value under reactive power operation (PF = 0.9). (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current. (d) THD of output current.

Fig. 6. Simulation results under low switching frequency operation (PF = 1). (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current.

Fig. 7. Simulation results under low switching frequency operation (PF = 0.9). (a) Inverter output voltage. (b) FC voltage. (c) Grid voltage and inverter output current.

Fig. 8. Simulation results with 15% FC voltage drop using different FC value.

CONCLUSION:

In this paper, a novel 6S-5L-ANPC inverter topology has been proposed. As compared with the conventional 5L-ANPC inverter, it requires only 6 switches for single phase, a reduction from 8 switches. The operating principles and switching states are presented. The results of comparison between 6S-5L-ANPC and the conventional 5L-ANPC topologies show that 6S-5L-ANPC topology has lower conduction loss and thus higher efficiency in high power condition. The specific modulation strategy of 6S-5L-ANPC inverter under reactive power operation has been proposed. Issues related to the DC-link capacitors and FC voltages balancing and the maximum reactive power capability are discussed. The equations to calculate the FC capacitance value in active and reactive power conditions are provided. Computer simulation and experimental prototype based on a single phase 1KVA prototype have been carried out in both active and reactive power conditions to demonstrate the reliability of the proposed topology and modulation method.

REFERENCES:

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