Output Voltage Of PWM Inverter Research Articles

Compensation method of PWM inverter output voltage under low sampling-to-fundamental frequency ratio operating conditions

Compensation method of PWM inverter output voltage under low sampling-to-fundamental frequency ratio operating conditions

Norton equivalent circuit for current control loop of grid-connected system

Modeling method for the current control loop of a grid-connected PWM inverter with the LCL output filter was discussed. Firstly, the current control loop with the LCL inverter-side current as feedback was established. Then, parameters of PI controller were calculated on the basis of an equivalent controlled object. Finally, Norton equivalent circuit for the current control loop of grid-connected system was derived by integrating one control equation, which connected the PWM inverter output voltage and the LCL inverter-side current, with two circuit equations, separately using the LCL inverter-side current and the injected current as loop currents. With the induced Norton equivalent circuit, system-level resonant and unstable issues on real grid-connected system applied in weak distributed power systems can be easily analyzed. The validity of substituting Norton equivalent circuit for grid-connected system is verified by simulation and experiment.

Hardware implementation of three-phase VSI using PIC16F877A microcontroller and optimisation using PSO

This paper reports hardware implementation of three-phase inverter using selective harmonic elimination technique by PIC16F877A microcontroller, whereas the notch angles are calculated through particle swarm optimisation (PSO) technique. This technique is proposed to minimise the overall total harmonic distortion (THD) of the output voltage of PWM inverter and corresponding switching angles are computed. This method is applied for the bipolar switching case, in three-phase inverter for three switching angles and five switching angles. The switching angles are computed to completely eliminate the lower order harmonics.

An application of PSO technique for harmonic elimination in a PWM inverter

Harmonic elimination problem in PWM inverter is treated as an optimization problem and solved using particle swarm optimization (PSO) technique. The derived equation for computation of total harmonic distortion (THD) of the output voltage of PWM inverter is used as the objective function in the PSO algorithm. The objective function is minimized to contribute the minimum THD in the voltage waveform and the corresponding switching angles are computed. The method is applied to investigate the switching patterns of both unipolar and bipolar case. While minimizing the objective function, the individual selected harmonics like 5th, 7th, 11th and 13th can be controlled within the allowable limits by incorporating the constraints in the PSO algorithm. The results of the unipolar case using five switching angles are compared with that of a recently reported work and it is observed that the proposed method is effective in reducing the voltage THD in a wide range of modulation index. The simulated results are also validated through suitable experiments.

A novel strategy for a high‐power utility interactive inverter with a series active filter

AbstractHigh‐power utility interactive inverters used for large‐capacity energy storage systems are composed of multiple connected inverters, in order to realize high efficiency and high performance of the harmonic elimination characteristic simultaneously. Some disadvantages of multiple connected inverters, such as harmonic current flowing from an inverter unit to the other one, and increase of the number of inverter units, cannot be overcome easily.This paper presents a novel strategy for a high‐power utility interactive inverter, which is composed of a large power with low‐switching‐frequency PWM inverter (high‐power PWM inverter), an LC passive filter, and a series active filter (series AF). Because harmonic components contained in the utility line current are absorbed by the series AF, the switching frequency of the PWM inverter can be selected to about 1 kHz. In addition because the power capacity and the output voltage of the series AF can be suppressed lower than 10% of the power capacity and the output voltage of PWM inverter, low‐voltage and high‐speed power devices can be applied to the series AF. Consequently, high power, high efficiency, and high harmonics elimination performance can be realized without increasing the number of inverter units. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 57–66, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10048

A Novel Strategy of High Power Utility Interactive Inverter with Series Active Filter

Large power utility interactive inverters used for large energy storage system are composed of the multiple connected inverters, in order to realize the high efficiency and the high performance on the harmonic elimination characteristic simultaneously. Some disadvantages on the multiple connected inverters, such as harmonic current flowing from an inverter unit to the other one, and increase of the number of inverter units, cannot be overcome easily.In this paper, a novel strategy of the high power utility interactive inverter, which is composed of a large power with low switching frequency PWM inverter (High Power PWM Inverter), a LC passive filter and a series active filter (Series AF), is presented. Because harmonic components contained in the utility line current is absorbed by the series AF, the switching frequency of the PWM inverter can be selected to about 1kHz. And, because the power capacity and the output voltage of the series AF can be suppressed lower than 10% of the power capacity and the output voltage of PWM inverter, low voltage and high-speed power devises can be applied to the series AF. Consequently high power, high efficiency and high harmonics elimination performance can be realized without increasing the number of inverter units.

Starting characteristics of motor in inverter-motor drive system

When the induction motor is fed from the PWM VSI inverter, with and without torque enhancing function, the variations of the starting torque and the starting current versus the starting frequency are analyzed, based on the steady state equivalent circuit of the induction motor. The corresponding expressions are derived, and the corresponding curves are also drawn, from which the initial starting frequency range can be determined properly and easily. The initial starting frequency range is the common range, in which the starting torque should be high enough and the starting current low enough. Some other useful formulas are also derived. These results are significant for electrical drive designers to make the starting schemes. The effects of the increase of the stator and the rotor resistances on the starting torque and the initial starting frequency range are also discussed, which is caused by the skin effects of the high order harmonics present in the PWM inverter output voltage.

Electromagnetic noise of induction motors driven by PWM inverters

When a squirrel cage induction motor is driven by a PWM inverter, electromagnetic noise different from that during commercial power source drive is experienced. This is because of sideband wave voltage induced in PWM inverter output voltage. This paper first describes the mechanism of electromagnetic noise generation in commercial power source drive, and then electromagnetic force considering the sideband frequency and voltage content and the mechanism of electromagnetic noise generation in PWM inverter drive. It also refers to the sideband frequency and voltage content because of operating time control. © 2000 Scripta Technica, Electr Eng Jpn, 133(3): 55–62, 2000

Walsh Function based Reconstruction Method of Triangular-wave PWM Command Voltage Waveform

This paper proposes a Walsh-function based reconstruction-method of command voltage waveform of a PWM inverter. The Fourier harmonics of PWM inverter output voltage show that the PWM switching harmonics spread toward lower frequency range and it makes difficult to reconstruct the PWM command voltage waveform especially in the case when the command voltage waveform has sharp edge. On the other hand, the Walsh harmonics show very good separation between original command voltage component and PWM switching component. Therefore, the Walsh-function based reconstruction-method can reconstruct the PWM command voltage waveform correctly. These remarkable features of the proposed method are clarified by several simulation results.

Electromagnetic Noise of Induction Motors driven by PWM inverters

When a squirrel cage induction motor is driven by a PWM inverter, electromagnetic noise different from the one during commercial power source drive is experienced. This is because of sideband wave voltage induced in PWM inverter output voltage. This paper describes the mechanism of electromagnetic noise generation in commercial source drive, then electromagnetic force considering the sideband frequency and voltage content and the mechanism of electromagnetic noise generation in PWM inverter drive. It also refers the sideband frequency and voltage content because of operating time in control.

Line conditioning system with simple control strategy and fast dynamic response

The performance and dynamic characteristics of a solid-state line conditioning system which simultaneously eliminates line current harmonics and compensates load power factor is presented and analysed. The line conditioning system is implemented with a pulsewidth modulated voltage-source inverter. Power factor compensation is achieved by controlling the magnitude and the phase angle (delta) of the transistorised PWM inverter output voltage. Fast response times are obtained by adjusting the amplitude of the PWM inverter output voltage through a modulation index control. The principal advantage of this scheme is that it can maintain a near unity mains overall power factor without sensing and computing the associated reactive power component. It can also substantially reduce the harmonic content of the line current when the load is nonlinear. A time domain model is derived and used to accurately predict dynamic behaviour, the stability region and to adjust system controllers. The transfer function of the line conditioning system for open-loop and closed-loop operation is derived. Experimental results confirm the operation characteristics obtained by computer simulation and mathematical analyses.

The Use of Harmonic Distortion to Increase the Output Voltage of a Three-Phase PWM Inverter

By adding a measure of third harmonic to the output of each phase of a three-phase inverter, it is possible to obtain a line-to-line output voltage that is 15 percent greater than that obtainable when pure sinusoidal modulation is employed. The line-to-line voltage is undistorted. The method permits the inverter to deliver an output voltage approximately equal to the voltage of the ac supply to the inverter. Thus an induction motor of standard rating with respect to the ac supply to the inverter can deliver very nearly full power at rated speed when supplied from the inverter. This is achieved without pulse dropping or any other form of mode-changing.