• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• Journal of Power Electronics
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• v.8 no.2
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• pp.171-180
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• 2008

One of the major problems in electric power quality is the harmonic contents. There are several methods of indicating the quantity of harmonic contents. The most widely used measure is the total harmonic distortion (THD). Various switching techniques have been used in static converters to reduce the output harmonic content. This paper presents and compares the two harmonic optimization techniques, known as optimal minimization of the total harmonic distortion (OMTHD) technique and optimized harmonic stepped-waveform (OHSW) technique used in multi-level inverters with unequal dc sources. Both techniques are very effective and efficient for improving the quality of the inverter output voltage. First, we describe briefly the cascaded H-bridge multi-level inverter structure. Then, we present the switching algorithm for the inverter based on OHSW and OMTHD techniques. Finally, the results obtained for the two techniques are analyzed and compared. The results verify the effectiveness of the both techniques in multi-level voltage-source inverter with non-equal dc sources, clarifying the advantages of each technique.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.215-227
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• 2019

Grid-connected inverters should satisfy a certain level of total harmonic distortion (THD) to meet harmonics standards, such as IEEE 519 and P1547. The output quality of an inverter is typically degraded due to grid voltage harmonics, dead time effects, and the device's turn-on/turn-off delay, which all contribute to increasing the THD value of the output. The use of a harmonic controller is essential to meet the required THD value for inverter output under a distorted grid condition. In this study, an improved feedforward harmonic compensation method is proposed to effectively eliminate low-order harmonics in the inverter current to the grid. In the proposed method, harmonic components are directly compensated through feedforward terms generated by the proportional resonant controller with the grid current in a stationary frame. The proposed method is simple to implement but powerful in eliminating harmonics from the output. The effectiveness of the proposed method is verified through simulation using PSIM software and experiments with a 5 kW single-phase grid-connected inverter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.4
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• pp.124-134
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• 2011

A new dead time compensation scheme that can exactly estimate the dead time and inverter nonlinearity under parameter variations is proposed for a PWM inverter-fed PMSM drive. The proposed scheme uses the fact that the sixth harmonic component in total disturbance estimated under the presence of various uncertainties is mainly caused by the dead time and inverter nonlinearity. The total disturbance due to the parameter variations as well as the dead time and inverter nonlinearity is estimated by the adaptive scheme. The sixth harmonic component is extracted from this total disturbance through harmonic analysis. The obtained sixth harmonic is processed by the PI controller to estimate the disturbance caused by the dead time and inverter nonlinearity in the stationary reference frame. The effectiveness of the proposed scheme is verified. Without requiring an additional hardware, the proposed scheme can effectively compensate the dead time and inverter nonlinearity even under the parameter variations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.473-479
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• 2008

With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.236-241
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• 2008

With the advent of mobile phone, Digital multimedia broadcasting (DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion (THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.80-84
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• 1995

ABSTRACT - This paper presents a software based 3 phase 5 level pulse-width modulation(PWM) inverter to reduce total harmonic distortion. The proposed modulation technique can reduce total harmonic distortion and significantly improve the performance of the inverter. In the modulation mode where the frequency ratio is 36 and modulation index is 1.2∼2.0, harmonic components have been mostly eliminated and the magnitude of fundamental component have been maximized by the 3 phase 5 level PWM inverter.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.261-270
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• 2015

In this paper, the Optimal Harmonic Stepped Waveform (OHSW) method is proposed in order to eliminate the selective harmonic orders available at the output of cascaded multilevel inverter (CMLI) fed by solar photovoltaic (SPV). This technique is used to solve the harmonic elimination equations based on stepped waveform analysis in order to obtain the optimal switching angles which in turn reduce the Total Harmonic Distortion (THD). The OHSW method considers the output voltage waveform as four equal symmetries in each half cycle. In the proposed method, a solar fed fifteen level cascaded multilevel is considered where the magnitude of six numbers of harmonic orders is reduced. A programmable pulse generator is developed to carry the switching angles directly to the semiconductor switches obtained as a result of OHSW analysis. Simulations are carried out in MATLAB/Simulink in which a separate model is developed for solar photovoltaic which serves as the input for cascaded multilevel inverter. A 3kWp solar plant with multilevel inverter system is implemented in hardware to show the effectiveness of the proposed system. Based on the observation the OHSW method provides the reduced THD thereby improving power quality in renewable energy applications.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1889-1900
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• 2018

Harmonic current mitigation is vital in power distribution networks owing to the inflow of nonlinear loads, distributed generation, and renewable energy sources. The active power filter (APF) is the current electrical equipment that can dynamically compensate for harmonic distortion and eliminate asymmetrical loads. The compensation performance of an APF largely depends on the control strategy applied to the voltage source inverter (VSI). Model predictive control (MPC) has been demonstrated to be one of the effective control approaches to providing fast dynamic responses. This approach covers different types of power converters due to its several advantages, such as flexible control scheme and simple inclusion of nonlinearities and constraints within the controller design. In this study, a finite control set-MPC technique is proposed for the control of VSIs. Unlike conventional control methods, the proposed technique uses a discrete time model of the shunt APF to predict the future behavior of harmonic currents and determine the cost function so as to optimize current errors through the selection of appropriate switching states. The viability of this strategy in terms of harmonic mitigation is verified in MATLAB/Simulink. Experimental results show that MPC performs well in terms of reduced total harmonic distortion and is effective in APFs.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.613-615
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• 1996

Harmonic elimination method of using coupling transformer in twelve pulse inverter is presented for high power application. This method is using coupling transformer and PWM(pulse width modulation) switching and voltage source inverter. The object of proposed harmonic elimination method is obtained inverter output of low THD(Total Harmonic Distortion). The simulation results confirm the proposed harmonic elimination method.