Abstract
This paper presents a new configuration of voltage source inverter with a simplified circuit for generating five-level pulse width modulation (PWM) voltage waveform. Compared with conventional inverter configuration, this circuit is drastically able to simplify the structure and reduce the required number of active switch components. The new inverter circuit is very suitable for the use of open-end connection loads such as open-end winding ac motor drive application. Instead of using separated dc power sources, the new inverter circuit configuration is also possible to utilize only one dc voltage source, so the power supply circuits can be made simpler. Furthermore, to reduce ripples of dc capacitor voltages, the voltage stabilizing circuit of capacitors at the input side was proposed and applied. The stabilizing circuit is capable to work reducing the size of dc capacitors, and maintaining voltage stability of capacitors through charging and discharging operation modes. The working principles of inverter circuit were evaluated and examined by means of computer simulations using PSIM software. In addition, experimental test results of the prototype were also provided. Test results proved that the new five-level PWM inverter operated well generating five-level output waveform with smaller distortion and less voltage ripples of dc capacitors.
Highlights
A multilevel inverter is a type of inverter working to produce ac voltage or ac current waveforms with three or more level numbers of waveforms [1,2,3]
The inverter Vcircuit dc voltage source was applied to the input side of the inverter
The new inverter circuit can reduce six power switches, three isolated gate drive circuits and six gate drive circuits compared with a conventional inverter
Summary
A multilevel inverter is a type of inverter working to produce ac voltage or ac current waveforms with three or more level numbers of waveforms [1,2,3]. If the input is in the form of dc current source, the inverter circuit is included as the current source inverter type [4]. In a regular two-level voltage source inverter, output voltage before the filter circuit is a discrete ac voltage waveform with a large dv/dt value, whereas in the two-level current source inverter, the output current wave before the filter is a discrete ac current wave with a large di/dt value. Multilevel inverters are able to work generating ac output voltages or currents with a smaller distortion value, smaller filter size, smaller dv/dt or di/dt value, and the ability to work at a greater power capacity [5,6]. The first topology connects some H-bridge inverters in a series to synthesize multilevel voltage waveform. More complex dc power source circuits are required when the power sources are rectifier systems
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