• Journal of Power Electronics
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• v.9 no.3
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• pp.481-490
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• 2009

This paper describes a SVPWM overmodulation scheme of NPC type three-level inverter for traction drives which extends the modulation index from MI=0.907 to unity. SVPWM strategy is organized by two operation modes of under-modulation and over-modulation. The switching states under the under-modulation modes are determined by dividing them with two linear regions and one hybrid region the same as the conventional three-level inverter. On the other hand, under the over-modulation mode, they are generated by doing it with two over-modulation regions the same as the conventional over-modulation strategy of a two level inverter. Following the description of over-modulation scheme of a three-level inverter, the system description of a vector controlled induction motor for traction drives has been discussed. Finally, the validity of the proposed modulation algorithm has been verified through simulation and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.341-351
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• 1996

The values for the average and rms currents in a three-level PWM inverter are required in order to select the various components such as power semiconductor devices, capacitors and reactors of inverter circuit. And those are very useful for the designing of the heat sink. In this paper, therefore, the simple current equations are proposed for a three-level PWM inverter. Analysis of inverter current waveforms indicate that the average and rms inverter currents are dependent on the load power factor and PWM modulation index (Ma). Error analysis and experiment results verify the effectiveness of the proposed current equations. (author). refs., figs., tabs.

• Journal of the Semiconductor & Display Technology
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• v.14 no.4
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• pp.72-77
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• 2015

Three-level diode clamped multilevel inverter, generally known as neutral point clamped (NPC) inverter, has an inherent problem causing neutral point (NP) potential variation. Until now, the NP potential problem of variation has been investigated and lots of solutions have also been proposed. This paper presents a neutral point voltage control technology using the anti-windup PI controller and offset technology of PWM (Pulse Width Modulation) to control the variation of NPC 3-phase three-level inverter neutral point voltage. And the proposed algorithm is tested and verified using a PLL (Phase Locked Loop) in order to synchronize the phase voltage from the line voltage of grid. It significantly improves the voltage balancing under a solar fluctuation conditions of the inverter. Experimental results show the good performance and effectiveness of the proposed method.

• Journal of Power Electronics
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• v.12 no.2
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• pp.285-293
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• 2012

Multilevel inverters have gained attention in high-power applications due to their numerous advantages in comparison with conventional two-level inverters. In this paper a simplified Space-Vector Modulation (SVM) algorithm for a three-level Neutral-Point Clamped (NPC) inverter is implemented on a Freescale$^{(R)}$ DSP56F8037. The algorithm is based on a simplification of the space-vector diagram for a three-level inverter so that it can be used with a two-level inverter. Once the simplification has been achieved, calculation of the dwell times and the switching sequences are carried out in the same way as for the two-level SVM method. Details of the hardware design are included. Experimental results are analyzed to validate the performance of the simplified algorithm.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1821-1834
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• 2017

Medium voltage control applications due to obtain better output voltage and reduced electro-magnetic interference multi level inverter is used. In closed loop control with inverter, the PI controller does not operate satisfactorily when the operating point changes. This paper presents the performance of Co-Efficient diagram PI controller based indirect vector controlled induction motor drive fed from three-level inverter under different operating conditions (dynamic and steady state). The proposed Co-Efficient diagram PI controller based three level inverter significantly reduces the torque ripple compared to that of conventional PI controller. The performance of the indirect vector controlled induction motor drive has been simulated at different operating conditions. For three-level inverter control, a simplified space vector modulation technique is implemented, which reduces the coordinate transformations complications in the algorithms. The performance parameters, torque ripple contents and THD of induction motor drive with three-level inverter is compared under different operating conditions using CDM-PI and conventional PI controllers.

• Journal of Power Electronics
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• v.5 no.3
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• pp.224-232
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• 2005

A new three phase three-level Pulse Width Modulation (PWM) Switched Voltage Source (SVS) inverter with zero neutral point potential is proposed. It consists of three single-phase inverter modules. Each module is composed of a switched voltage source and inverter switches. The major advantage is that the peak value of the phase output voltage is twice as high as that of a conventional neutral-point-clamped (NPC) PWM inverter. Thus, the proposed inverter is suitable for applications with low voltage sources such as batteries, fuel cells, or solar cells. Furthermore, three-level waveforms of the proposed inverter can be achieved without the switch voltage imbalance problem. Since the average neutral point potential of the proposed inverter is zero, a common ground between the input stage and the output stage is possible. Therefore, it can be applied to a transformer-less Power Conditioning System (PCS). The proposed inverter is verified by a PSpice simulation and experimental results based on a laboratory prototype.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.152-159
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• 2018

In this paper, a novel topology of two-level voltage-type inverter is proposed. The proposed inverter has three bridge arms while each bridge is made up of two thyristors, one IGBT and four diodes. Thyristors complete the phase positioning of the inverter, IGBT completes the modulation of different modulation modes such as SPWM, SVPWM, and SHPWM, and the diodes complete the commutation of the bridge arms. Compared to the traditional voltage-type inverter with six IGBTs, the proposed voltage-type inverter using three IGBTs can achieve the same function with highly reduced cost. The principle of the proposed two-level inverter is explained in detail. The simulation and experiment results demonstrate the performance and effectiveness of the proposed inverter-type inverter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.268-275
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• 2015

This paper proposes a method of switching to improve power loss for the single-phase three-level NPC inverter. The conventional switching methods, which are called as the bipolar and unipolar switching methods, are used for single phase inverters using three-level topology. However, these switching method have disadvantage in the power loss. Because all of the switch are operated. To reduce the power loss of the three-level NPC inverter, clamp switching method is introduced in this paper. This way, one of the lag is fixed that switching loss is reduced. This paper analyzes and compares power losses of unipolar method and clamp method. The validity of the power loss analysis is verified through the simulation and experimental results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• Journal of Power Electronics
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• v.18 no.2
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• pp.522-532
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• 2018

The cascaded H Bridge (CHB) multilevel inverter (MLI) is popular among the classical MLI topologies due to its modularity and reliability. Although space vector modulation (SVM) is the most suitable modulation scheme for MLIs, it has not been used widely in industry due to the higher complexity involved in its implementation. In this paper, a simple and novel generalized SVM algorithm is proposed, which has both reduced time and space complexity. The proposed SVM involves the generalization of both the duty cycle calculation and switching sequence generation for any n-level inverter. In order to generate the gate pulses for an inverter, a generalized switch matrix (SM) for the CHB inverter is also introduced, which further simplifies the algorithm. The algorithm is tested and verified for three-phase, three-level and five-level CHB inverters in simulations and hardware implementation. A comparison of the proposed method with existing SVM schemes shows the superiority of the proposed scheme.