A Single-Phase Cascaded Multilevel Inverter Based on a New Basic Unit with Reduced Number of Power Switches

Transcription

1 Page number 1 A Single-Phase Cascaded Multilevel Inverter Based on a New Basic Unit with Reduced Number of Power Switches Abstract The demand for high-voltage high-power inverters is increasing, and it is impossible to connect a power semiconductor switch to a high-voltage network directly. Therefore, multilevel inverters had been introduced and are being developed now. With an increasing number of dc voltage sources in the input side, a sinusoidal like waveform can be generated at the output. As a result, the total harmonic distortion (THD) decreases, and the output waveform quality increases, which are the two main advantages of multilevel inverters. In addition, lower switching losses, lower voltage stress of dv/dt on switches, and better electromagnetic interference are the other most important advantages of multilevel inverters. These kinds of inverters are generally divided into three main categories, i.e., neutral-point-clamped multilevel inverters, flying capacitor multilevel inverters, and cascaded multilevel inverters. There is no diode clamped or flying capacitors in cascaded multilevel inverters. Moreover, these inverters consist of modularity, simplicity of control, and reliability, and they require the lowest

2 Page number 2 number of power semiconductor devices to generate a particular level. Existing system A cascaded H-bridges multilevel inverter is simply a series connection of multiple Hbridge inverters. Each H-bridge inverter has the same configuration as a typical single-phase full-bridge inverter. The cascaded H-bridges multilevel inverter introduces the idea of using Separate DC Sources (SDCSs) to produce an AC voltage waveform. Each H-bridge inverter is connected to its own DC source Vdc. By cascading the AC outputs of each H-bridge inverter, an AC voltage waveform is produced. By closing the appropriate switches, each H-bridge inverter can produce three different voltages: +Vdc, 0 and -Vdc. It is also possible to modularize circuit layout and packaging because each level has the same structure, and there are no extra clamping diodes or voltage balancing capacitors. Proposed system In order to increase the number of generated output levels by using a lower number of power electronic devices, a new basic unit is proposed in this paper. By a series connection of several proposed basic units, a new cascaded multilevel inverter is proposed. Then, to generate all positive and negative levels at

3 Page number 3 the output, an H-bridge will be added to this inverter because the proposed inverter only generates positive levels. This inverter is called the developed proposed cascaded multilevel inverter. In order to generate all voltage levels at the output, four different algorithms are proposed. Advantages Requires the minimum number of power switches, IGBTs, power diodes, driver circuits, and dc voltage sources. Reduction in the installation space and total cost of the inverter

4 Page number 4 Block diagram UNIT1 CIRCUIT UNIT 1 FULL BRIDGE INVERTER LOAD UNIT2 CIRCUIT UNIT 2 UNIT3 CIRCUIT UNIT 3 DRIVER CIRCUIT 12V DC 12V DC OPTO ISOLATOR CIRCUIT 5V DC PIC CONTROLLER Copyright WITH 2015 LeMeniz Infotech. All rights reserved BUFFER

5 Page number 5 Tools and software MPLAB microcontroller programming. ORCAD circuit layout. MATLAB/Simulink Simulation.