Synchronous Current Harmonic Optimal Pulsewidth Modulation for Three-Level Inverter

The Selective Harmonic Elimination PWM (SHEPWM) based on Walsh transform converts nonlinear transcendental equations in the Fourier domain to linear algebraic ones. Under appropriate initial condition, the piece-wise linear relation between fundamental voltage amplitude and switching angles is obtained, so voltage regulation and harmonic elimination can be realized online. Thus, the technique highly suits to the inverter of dynamic voltage restorer (DVR). In the paper, the sameness and the difference between switch angles distribution of SHEPWM and of Centroid PWM (CPWM) are summarized, and, according to the relationship between both PWM modes, a new method to solve SHE equation in Walsh domain is proposed. Based on the feature of harmonic distribution of the SHEPWM pulses, the paper presents design principle of inverter filter. The experimental result of 200 kVA DVR using SHEPWM indicates that the inverter can effectively restrain the harmonics and has good dynamic performance in all the range of output voltage.

The combination of five-level converters with selective harmonic elimination pulse-width modulation (SHEPWM) is a practical need in medium-voltage, high-power applications. However, how to suppress the common-mode voltage (CMV) in this case becomes a difficult problem. Although CMV suppression under high switching frequency (SF) modulations and three-level SHEPWM has been discussed in many studies, these methods are not applicable to five-level SHEPWM. This is partly because the zero-sequence voltage under SHEPWM is difficult to adjust and partly because the solution spaces of three- and five-level SHEPWM are completely different. Moreover, conventional CMV suppression in three-level SHEPWM must sacrifice the switching angles to control the zero-sequence voltage, which makes the equivalent SF increase. Therefore, in this article, we propose a novel CMV suppression method that effectively utilizes the multimode characteristics of five-level SHEPWM. Multimode characteristics refers to the output waveform containing different levels of jump patterns. Therefore, there are a large number of switching angle trajectories in five-level SHEPWM, which outputs the same fundamental voltage with different CMVs. The proposed method uses the special multimode characteristics to reduce the CMV without sacrificing the switching angles. Its effectiveness and feasibility are verified by experiments.

In this paper, in order to improve the control performance of a high-power electrically excited synchronous motor (EESM) under low switching frequency, and to improve the poor dynamic response of the traditional selective harmonic elimination pulse width modulation (SHEPWM) strategy, an optimized pulse width modulation (PWM) pulse mode with specific harmonic elimination and good dynamic performance is studied. Based on the fast response characteristics of predictive control, it combines the rolling time domain optimization theory with SHEPWM strategy. Firstly, the stator flux linkage of EESM is taken as the tracking target, and the real-time tracking error value of flux linkage is transformed into a voltage-second product; then, the predictive rolling time domain is established, the above error voltage-second product value is optimized in this time domain and the switching angle of SHEPWM is dynamically adjusted to minimize the stator tracking error so as to realize the dynamic adjustment of EESM at low switching frequency. Through MATLAB simulation and a 50 kW experimental platform, the optimized modulation strategy proposed in this paper has been verified to have good dynamic regulation performance at low switching frequency (≈500 Hz).

Offline pulse width modulation (PWM) techniques are employed to reduce the line current distortion in induction motor (IM) drives where the switching frequency is highly constrained. An optimal PWM technique is proposed here for a neutral point clamped (NPC) inverter fed IM drive to minimize the motor current distortion, subject to constraints on number of switching instants per quarter cycle. Two types of pole voltage waveforms of the NPC inverter are considered, namely type-I and type-II. This paper reports optimal switching angles for both type-I and type-II waveforms to minimize the resulting total harmonic distortion (THD) in motor current. In general optimal type-II is found to result in lower THD than optimal type-I PWM. The optimal type-II PWM offers superior performance in terms of motor current distortion than synchronized sine-triangle PWM and selective harmonic elimination PWM, as shown by simulation and experimental results on an NPC inverter fed 3.7 kW induction motor drive.

For medium- and high-power electronic application technologies, the three-level neutral-point-clamped (3L-NPC) inverter is an effective solution and modulation method is one of its research focuses. There are many modulation strategies for the 3L-NPC inverter, among them, the selective harmonic elimination pulse width modulation (SHEPWM) and selective harmonic mitigation pulse width modulation (SHMPWM) techniques are very useful technologies since they have the characteristics of selective harmonics reduction or elimination. In this paper, simulation models of the 3L-NPC inverter with 10kV grid based on total harmonic distortion (THD) using the SHEPWM and SHMPWM techniques are built in MATLAB/SIMULINK. Here, both the SHEPWM and SHMPWM techniques use fifteen switching angles to generate the switching pattern and the solutions of the nonlinear transcendental equations for these two kinds of PWM techniques are obtained by using the fmincon function with THD-based objective function in MATLAB. Finally, the comparative analysis of the SHEPWM and SHMPWM techniques for the 3L-NPC inverter with 10kV grid based on the THD of voltage and current up to the 50th and the 100th is proposed to verify the respective advantages of the SHEPWM and SHMPWM techniques in different harmonic suppression cases.

The inverters and control methods are applied in more and more fields with power electronics development. The technology of current hysteretic band PWM is a kind of easy and reliable control method. But the harmonic distortion of load current is big amplitude around switching frequency side band. The paper introduce a Varied Hysteretic-band Current control technique(VHBCC), this method can spreads the spectrum contents of load current around switching frequency side band, reduces the harmonic distortion of load current . At last, The results of simulation prove the method feasible and effective.

Renewable energy has a great importance for power generation as it does not use the fossils fuels. Energy generated from alternative energy sources are weather dependent. To generate a continuous power to meet the load requirements, Battery energy storage system are used. Power conversion process must be much efficient as possible to convert the DC stored energy into AC. This conversion process is usually done by the help of inverters. This paper gives the brief overview on three main categories of multilevel inverter like cascaded h-bridge, neutral point clamped and flying capacitor multilevel inverter and highlights their advantages which can also help the scholars to deeply explore the categories of multilevel inverter. Harmonic elimination is usually done by controlling the switching angles of the inverter. Among all the switching angles techniques, selective harmonic elimination pulse width modulation (SHEPWM) technique is widely used, that has also discussed in this paper. Furthermore, to eliminate the harmonics using SHEPWM, it has the set of nonlinear transcendental equations, these set of equations can be effieceintly solved by the optimization methods. The most efficient and reliable optimization method like particle swarm optimization has been discussed with multiple objective functions in this paper. This paper will help the scholars to understand the finest category of multilevel inverter for harmonic elimination in terms of efficiency and output quality.

In this paper, the modified single phase nine-level CHB-MLI is proposed based on the selective harmonic elimination pulse width modulation (SHE-PWM) using artificial neural network (ANN) technique. The number of proposed switching devices reduced in a now modified CHB-MLI compared with the conventional structure of CHB-MLI which decreases the switching frequency of the system, leading to a decrease in the total power switching losses. The switching angles of CHB-MLI in this paper are detected and controlled based on the ANN technique into selective harmonic elimination transcendental nonlinear equation which is considered as the popular and powerful method for minimizing the harmonic order at the output voltage waveform of the MLI and produces a low ratio of total harmonic distortion (THD%). This paper aims to design, simulate and build up new modified structure of the single-phase nine-levels CHB-MLI and predict the real-time switch in order to generate superior switching angles by using ANN technique. MATLAB simulation has been used for designing and simulating the nine-levels single-phase CHB-MLI with ANN technique for switching angles prediction. It is found the proposed technique able to reduce harmonic contents of output waveform.

specific odd harmonics can be mitigated by operating the semiconductor switches in H-bridge inverters at optimized switching angles of the PWM signals. These switching angles can be achieved by deriving a number of nonlinear equations using Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) method. Modulation index (m) is a significant parameter used to control the amplitude of the fundamental output voltage of DC-AC inverter. By changing the value of modulation index the Total Harmonics Distortion (THD) also will change. In this paper, the performance of single phase full-bridge inverter using SHE-PWM scheme with varying the modulation index is evaluated. In order to achieve a minimum THD, a different number of nonlinear equations are used to calculate the switching angles. The performance of a single phase unipolar inverter is simulated in Matlab.

An improved selective harmonic elimination‐pulse width modulation (SHE‐PWM) scheme has been proposed for a three‐phase seven‐level cascaded H‐bridge (CHB) inverter that enhances the power utilisation capability of the inverter by sharing the desired amount of power among the H‐bridge cells and also eliminates both 5th‐ and 7th‐order harmonic components from the inverter output voltage maintaining the desired fundamental voltage component for a wide range of modulation index. Compared to conventional SHE‐PWM, this scheme introduces two additional switching in the first cell, while the second and the third cells are switched at advanced switching angles. The differential search algorithm (DSA) technique has been applied to solve the proposed SHE‐PWM scheme, and it exhibited comparatively better performance than the algorithm based on genetic algorithm, BEE algorithm and particle swarm optimisation. The effectiveness of the proposed scheme has been verified by both simulation and experimental study on a seven‐level CHB inverter. Finally, the proposed scheme has been applied to the closed‐loop constant V/f control of the induction motor drive application. It has been established that the proposed scheme is independent of the load power factor angle, and it improved the power conversion efficiency of the conventional SHE‐PWM scheme.

This paper presents a new topology of three-level transformer-less photovoltaic (PV) inverter. In this topology, a 240V AC system is developed from a full bridge inverter circuit using PIC microcontroller (PIC16F628A-I/P) connected to an array of PV panel through a power factor correction circuit. The output waveform of the inverter depends on the type of pulse driver. The inverter is connected to the utility supply, on the clear day, the ac load is served by the inverter but on the cloudy day or night where solar irradiance is low, the inverter through its PIC microcontroller automatically changes from the usage of inverter to the utility supply. Objective of this paper is to optimize the maximum voltage angle to obtain the lowest current total harmonic distortion (CTHD) of the uninterruptible power supply (UPS) on the three-level single phase transformer-less inverter. In this paper, the maximum voltage angle optimization of the AC three-level waveform transformer-less PV inverter is developed and created by a microcontroller PIC16F627A-I/P changing maximum voltage angle of the AC three-level waveform from 20° to 180°. Resistive load of 30 W lamp and inductive load of 20 W water pump are applied to the transformer-less PV single phase inverter. The result shows that the lowest CTHD of 15.448% is obtained when the maximum voltage angle is 134°.

On-line solution of switching angles of Selective Harmonic Elimination (SHE) PWM inverter has been a subject of research since 70s. Recent research has suggested new on- line control techniques for microprocessor implementation of SHE PWM method such as regular sampled harmonic elimination, space vector techniques, Walsh function harmonic elimination. A method based on curve fitting has been proposed in this paper. The solution trajectories by Newton iteration method are approximately represented by using 7 th order polynomial. On-line computation of switching angle (α) is just evaluation of polynomial equation by substituting value of modulation index (m). The complete solutions for unipolar switching pattern to eliminate 3rd to 23rd harmonics in the VSI output using conventional technique and curve fitting technique has been given. The deviations of actual and approximate solutions are also presented along with corroborative experimental results on a 1ph, 230V, 5kVA IGBT based VSI controlled by TMS320LF2406, 16-bit fixed point DSP processor.

This paper presents a modulation method based on the selective harmonic elimination-pulse width modulation (SHE-PWM) technique. The aim is to determine the optimal switching angles (SA) using the teaching learning-based optimization algorithm (TLBOA), capable of reducing the voltage total harmonic distortion (THD) present in the output waveform of single-phase multi-level inverters (MLIs). The performance of proposed technique has been verified through simulation using Matlab script and Simulink environment. The TLBOA-based SHE-PWM technique is applied to a 17-level inverter to eliminate 5th, 7th, 11th, 13th, 17th, 19th and 23rd harmonics, achieving an improvement of up to 4.31% in the phase voltage THD content in the range of modulation index (MI) 0.5 to 0.95. Furthermore, the superiority of the proposed technique was confirmed by comparison with conventional modulation techniques, which showed that the proposed technique produces lower THD than those used in the equal phase (EP), half-equal phase (HEP), feed forward (FF) and half height (HH) methods.

Conversion of DC to AC is widely used as an essential need for the power system to harness renewable power source in this era. Multilevel inverter is a mechanism which capable of harnessing these renewable energies. Unfortunately, harmonics occur in the system due to distortions and causing much unwanted problems at the power output. Therefore, the elimination of harmonics and reduce Total Harmonics Distortion (THD) are needed to maintain good power output. Application of Selective Harmonics Elimination Pulse Width Modulation (SHEPWM) can be used in the multilevel inverter to solve the problem. In this paper, optimization algorithms such as Particle Swarm Optimization (PSO), Whale Optimization Algorithm (WOA) and Sine Cosine Algorithm (SCA) were applied for finding suitable switching angle for SHEPWM. The calculated switching angle was applied into seven-level five-phase multilevel inverter for various modulation indexes. In addition, the simulation of the multilevel inverter also done using PSIM software. The results show that the selective lower order harmonics, 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> and 7 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> are completely eliminated for all three algorithms. In addition, the time taken for newly discovered algorithms to find switching angles for seven-level five-phase inverter is faster compared to PSO.

ABSTRACTThe number of bridges, gate drive circuits and dc sources decrease by using asymmetrical is used to solve SHE equations to get the optimal switching angles. Genetic algorithm (GA) is also used to solve these equations to make comparison between Satin bowerbird optimisation (SBO) and GA algorithms. Matlab/Simulink software tool is used to carry out the simulation construction multilevel inverter. The selective harmonic elimination pulse width modulation (SHE-PWM) and sinusoidal pulse width modulation (SPWM) are carried out for a nine levels cascaded H-bridge (CHB) inverter with asymmetrical construction. Comparison between SHE and SPWM is done to get the benefit of SHE over SPWM. The elimination of some lower order harmonics and satisfy fundamental component in output voltage are the major purpose of SHE-PWM. The solving of the non-linear transcendental equations of SHE is the challenge to find out the switching angles, SBO technique.