Selective Harmonic Elimination Modulation Research Articles

Modular Three-Phase Diode Rectifier With High-Frequency Isolation and Selective Harmonic Elimination Modulation

This article proposes a modular three-phase diode rectifier with high frequency isolation and selective harmonic elimination in input currents. The proposed system consists of modular ac–ac converters with 20 kHz transformer isolation on the primary side followed by a three-phase diode rectifier to produce a high quality dc output voltage. A new hybrid pulsewidth modulation scheme is proposed that combines the high frequency 20 kHz transformer operating frequency with a low frequency selective elimination of 5th, 7th, 11th, and 13th current harmonics in the 60 Hz input currents resulting in near sinusoidal waveform.Therefore, high quality input current is achieved in open loop. The secondary side consists of a three-phase diode rectifier with high quality output, suitable for ev-charging/switch mode power supplied in data centers etc. The output dc voltage is shown to be regulated via a simple duty cycle control of the high frequency (20 kHz) without affecting the harmonic elimination features in the input currents. The proposed approach is modular and can adapt to higher input voltages. Simulation results are discussed, which explore all the features of the proposed high performance ac to dc rectifier. Select results are verified experimentally on a 120 V rms line-to-line, three-phase, 1 kW laboratory prototype system. <xref ref-type="fn" rid="fn1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">¹</xref> <fn id="fn1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><label>¹</label> This article is the updated version of [1] and include more details about the output DC voltage regulation, the design of input (AC) and output (DC) filter, additional experimental results among other changes </fn>

Harmonic reduction using Particle Swarm Optimization based SHE Modulation Technique in Asymmetrical DC-AC Converter

Many inverters play an important role in transmitting and processing energy to power system networks. To reduce the cost and size of multilevel inverters, various topologies have been included in the literature. But these topologies do not look at the complete harmonic distortion in the output waveform. In this study, a modern multilevel inverter structure, a mutated H-bridge inverter is adopted that demands a small amount of switches, driver circuits, power diodes and DC voltage sources compared to conventional multilevel inverters to produce the required level in the output voltage. The mutated H-bridge converter uses a nearest-level control method, produces high value of total harmonic at the output voltage and low-level harmonics content is also high, which is more dangerous than high-order harmonics. Therefore, the selective harmonic elimination (SHE) method is used to reduce the low frequency harmonics and the total harmonic distortion to the output voltage. Comparison of complete harmonic deviation and low-level harmonic content using the above-mentioned control strategies on the 31-level inverter is presented. Simulation studies confirm the performance of a 31-level inverter with low-order harmonics and a complete harmonic distortion using the SHE process. The effectiveness and accuracy of the SHE in producing 31 level waveform is demonstrated by utilizing the test outcomes and the THD found is of the order of 2.8%, 1.7%, 1.7% and 1% for the modulation index values of 0.5590, 0.7440, and 0.8380 and 0.9110 respectively.

Selective Harmonic Elimination Technique for a 27-Level Asymmetric Multilevel Converter

In this paper, we present an implementation of selective harmonic elimination modulation technique in a 27-Level asymmetric multilevel converter. The main issue in this kind of converters is the generation of the gating patterns to obtain an optimized AC voltage waveform. State-of-the art solutions use deep mathematical analysis in the frequency domain by means of the Fourier series, but they are mainly applied for two-level or symmetric multilevel converters. On the other hand, the modulation for asymmetric multilevel converters is mainly focused on nearest level control or nearest vector control. In this work, we propose a novel modulating technique that takes advantage of the switching angles optimization for a 27-level waveform. In fact, different set of solutions are obtained and presented in order to define the modulation index as well as the value of the switching angles for the multilevel waveform. A modulation index sweep was performed for the entire operating region of the converter, where it can be observed that the number of levels decreases when the modulation index is low, which are calculated in order to minimize the total harmonic distortion (THD) of the resulting voltage waveform. In order to validate the proposal, these results for different modulation indexes values are simulated, obtaining a THD &lt; 5% for a modulation index 0.75&lt;M&lt;1.0. Finally, a small scale proof-of-concept prototype is implemented in order to validate the proposal.

Design of a multi-level inverter for applications in distributed generation

At present, the use of electricity generation systems through alternative sources of energy is continuously increasing, due to the increase in global energy demand, and a trend in which CO2 emissions are being reduced. As a result of these trends, the implementation of these energy sources has increased steadily in the last quarter of a century. For the integration of these alternative forms of electricity generation to be adequate, especially in the use of solar energy and wind energy, because it is necessary to condition them, it has become latent the need to implement electronic power devices such as inverters (continuous current - alternating current), which currently seek to have small, medium and high power sources of electricity, which meet the requirements of efficiency, quality and safety established by the Commission Federal de Electrician (CFE). In the present work, the design and the implementation of a DC/AC converter (direct current - alternating current) using a topology for the inverter of cascaded H - bridges with independent DC sources in a multilevel configuration of 11 voltage levels of control. Applying the technique of the Selective Harmonic Elimination modulation, technique that allows it by Fourier series analysis appropriately chooses the switching angles for the elimination of harmonics of the most significant low frequency.

Crystal Structure Algorithm (CryStAl) Based Selective Harmonic Elimination Modulation in a Cascaded H-Bridge Multilevel Inverter

This paper introduces an effective Selective Harmonic Elimination (SHE) modulation technique in a five, seven, and nine-level cascaded H-bridge (CHB) multilevel inverter (MLI). Minimization of the harmonics and device counts is the basis for the ongoing research in the area of MLI. Reduced harmonics and hence the lower Total Harmonic Distortion (THD), improve the output power quality. SHE is a low-frequency modulation scheme to achieve this goal. SHE techniques are used to eliminate the distinct lower-order harmonics by determining the optimum switching angles. These angles are evaluated by solving the non-linear transcendental equations using any optimization technique. For this purpose, the Crystal Structure Algorithm (CryStAl) has been used in this paper. It is a metaheuristic, nature-inspired, and highly efficient optimization technique. CryStAl is a simple and parameter-free algorithm that doesn’t require the determination of any internal parameter during the optimization process. It is based on the concept of crystal structure formation by joining the basis and lattice point. This natural occurrence can be realized in crystalline minerals in their symmetrically organized components: ions, atoms, and molecules. The concept has been utilized to solve non-linear transcendental equations. SIMULINK/MATLAB environment has been used for the simulation. The simulation result shows that the crystal structure algorithm is very effective and excels the other metaheuristic algorithm. Hardware results validate the performance.

Selective Harmonic Elimination of Five Level Cascaded H-Bridge Inverter Using the Newton-Raphson Technique

Multilevel inverter becomes an alternative for high power and medium voltage applications recently and is more popular in renewable energy. The cascaded H-bridge multilevel inverter is more suitable for the Photovoltaic application because it acts as a separate DC source for each bridge. This paper presents a selective harmonic elimination (SHE) modulation for single-phase cascaded H-bridge (CHB) five level inverter. The optimum angle of the transcendental equations is solved the fundamental and harmonic elements using the Newton-Raphson (NR) process. The proposed selective harmonic elimination (SHE) scheme is tested using MATLAB/Simulink simulation. These simulation results are then verified through experiment using microcontroller. The proposed SHE is efficient in eliminating the 5th order harmonics and producing a higher quality output waveform with a better harmonic profile.

CC-LA: determining optimal switching angles in a cascaded H-bridge multilevel inverter with the aid of binary cat cubpool-based lion algorithm

A multilevel inverter (MLI) is a power electronic device that includes the capability to offer the preferred voltage level (alternating) in the output. Accordingly, selective harmonic elimination (SHE) or pulse width modulation (PWM) methodologies were deployed widely. However, these techniques are not appropriate in a certain situation which involves a huge number of switching angles if an excellent primary guess is not obtainable. Hence, this paper intends to determine the optimum switching angles of a cascaded H-bridge multilevel inverter (CH-MLI) using a hybrid lion optimization algorithm (LOA) and binary cat swarm algorithm (BCSO). The objective of optimizing the switching angle is to generate the needed fundamental voltage and minimize the harmonic content. This is done by resolving the transcendental equations characterizing the harmonic content. The switching angles, i.e., α1, α2.... αm, should be tuned in such a way that it satisfies the condition [Formula: see text]. Here, the optimal tuning of switching angles is done by the proposed binary cat cubpool-based lion algorithm (BCC-LA). In addition, the analysis is done for the proposed method over the state-of-the-art models in terms of total harmonic distortion (THD), and the impact of varying loads is also examined for the proposed and traditional models, and thus, the superior performance of the proposed model is validated.

Dynamic and Steady State Response Analysis of Selective Harmonic Elimination in High Power Inverters

Selective harmonic elimination (SHE) technique has drawn tremendous interests for its superior harmonic performance, especially in high power devices where switching power loss and passive filter size are the main concerns. However, the drawbacks of slow dynamic response and difficulties in hardware implementation limit its engineering application. Based on a 3-level inverter, this paper analyzes the dynamic response of SHE. A system model is established and an improved method of updating the switching angles at sampling frequency is proposed. And a combination of notch filters and low-pass filter is designed to achieve a higher system bandwidth. The dynamic response and stability of the system are analyzed in detail. In addition, the influence of control errors on steady-state performance during hardware implementation is also discussed. A simple hardware structure of a DSP with a small-scale FPGA is adopted to realize the above method. Both dynamic response and steady-state response of the improved system are analyzed and compared with the regular SHE modulation and the widely used sinusoidal pulse width modulation (SPWM). Simulation and experimental results provided that the improved method proposed in this paper retains the excellent steady-state characteristics of the regular SHE modulation, and at the same time achieves as good dynamic performance as SPWM.

Application of a Non-carrier-Based Modulation for Current Harmonics Spectrum Control during Regenerative Braking of the Electric Vehicle

The regenerative braking of railway vehicles is widely used in DC railway systems all over the world. This mode of operation provides an opportunity to reuse part of the energy consumed by vehicles, and makes the railway system more energy efficient. During regenerative braking, not only energy management is an issue, but also Electromagnetic Compatibility EMC issues, such as interference of generated current harmonics with a railway signaling system. In this paper, the selective harmonic elimination modulation technique (SHE-PWM) was introduced to the traction drive with a three-level inverter to reduce specific catenary current harmonics generated during regenerative braking. The simulation model of a traction drive appropriate for harmonics analysis was proposed and verified by the measurements in the low-power laboratory drive system. The model was re-scaled to the 3 kV DC system for further study. The model of an induction motor with electromotive force and the method of its calculation was proposed. Furthermore, an analysis of the braking chopper operation was carried out. The asymmetric control of braking chopper was proposed to reduce the current harmonics below limits during chopper operation.

An Active Bypass Pulse Injection-Based Low Switching Frequency PWM Approach for Harmonic Compensation of Current-Source Converters

In this article, a bypass pulse injection-based pulsewidth modulation approach is proposed for mitigating line current harmonics of grid-tied current-source converters (CSCs) operating at a low switching frequency. First, the relationship between the CSC output harmonic current and the format of the bypass pulse is analyzed. Then, through online adjustment of both bypass pulse location and width, the seventh harmonic component of the output current is actively regulated to mitigate the corresponding seventh line harmonic current. Meanwhile, this action may be associated with additional amplification of the fifth output current. To deal with this issue, the unsymmetrical selective harmonic elimination (SHE) modulation with online adjustable switching angles is applied to further mitigate the fifth harmonic line current. It has been experimentally validated that with the application of both the bypass pulse injection and the unsymmetrical SHE-based modulation approaches, both the fifth and the seventh harmonic line currents can be simultaneously suppressed with ultralow switching frequency below 1 kHz.

Five-Level Single Source Voltage Converter Controlled Using Selective Harmonic Elimination

The paper presents a 5-level cascaded H-bridge voltage source inverter. The converter topology composed of two-cascaded H-bridge modules connected in parallel and powered by a single DC source. The benefit of this topology in comparison with the conventional H-Bridge configuration is that it uses single input DC source instead of two to achieve the same output steps/levels. Selective Harmonic Elimination (SHE) is the modulation technique employed. The generated non-linear transcendental equations are solved using an optimised Genetic algorithms to find the switching angles. This property makes the topology and the control function suitable for three phase applications where triplen harmonics are said to cancel out at the line-to-line voltages. This concept of SHE modulation extends the value of the filter cut-off frequency, which translates to smaller sized filter, compact cooling system and reduced system weight. This advantage makes the topology attractive to automotive and renewable energy applications. The topology was simulated using PSIM software.

Selective Harmonic Elimination Technique With Control of Capacitive DC-Link Voltages in an Asymmetric Cascaded H-Bridge Inverter for STATCOM Application

In this paper, the selective harmonic elimination (SHE) technique is introduced for a cascaded H-bridge-based static VAR compensator (CHB-STATCOM) with unequal capacitive dc-link voltages. The asymmetric topology allows increasing the number of voltage levels while keeping the converter losses low. Moreover, reactive power control is realized by using the decoupled current control, and the voltage of individual capacitors is controlled by the help of SHE modulation. Mathematical equations are derived for synthesizing the multilevel ac waveform and regulation of dc-link voltages for a CHB inverter with an arbitrary number of H-bridge cells. Then, to verify the theoretical claims, simulation and experimental results are provided for a three-phase CHB inverter with two H-bridge cells in each phase.

Hybrid optimization algorithm applied for selective harmonic elimination in multilevel inverter with reduced switch topology

This paper presents, ant colony optimization based hybrid algorithm for selective harmonic elimination in single phase seven level multilevel inverter with reduced switches. For high power and high voltage applications, multilevel structure with selective harmonic elimination (SHE) modulation scheme is used. The output voltage of multilevel inverter contains fundamental component along with harmonics. SHE technique aims to solve non-linear transcendental equations maintaining the fundamental harmonic component to its desired value and to eliminate lower order odd harmonics. Many optimization algorithms have been implemented to solve this problem. But these algorithms are complicated and time consuming. The Newton–Raphson algorithm is also very convergent for solving these non-linear equations. The main disadvantage of this method is, it requires strong initial guess. To overcome these drawbacks, hybrid optimization algorithm is used in this paper. This algorithm is performed in two stages, during first stage ant colony optimization has been run and in second stage the solutions obtained from ACO is used as a initial guess for Newton–Raphson algorithm which confirms the exact converged solution. Thus the drawback of Newton’s method i.e. requirement of good initial guess is overcomed by proposed hybrid algorithm. The MATLAB/SlMULINK software is used for comprehensive simulation of seven-level inverter. Experimental results validate the simulated results.

Effect of the supply voltage fluctuations on the efficiency of the technique of shaping the current spectrum generated by VSI traction drive

The issue of interfering influence of traction vehicles on railway traffic control systems is a serious problem posing a threat to railway traffic safety. This issue is gaining in importance as more and more vehicles equipped with traction inverters are put into service. Current harmonics generated by traction vehicles equipped with voltage source inverters can be controlled in such a way that they do not exceed the limits imposed by railway operators. One of the current harmonic control techniques, proposed by the authors, is the use of a combination of SHE (Selective Harmonic Elimination) and SHM (Selective Harmonic Mitigation) techniques to control the traction voltage source inverter. In this article, the author present the results of investigations on the influence of supply voltage fluctuations on the efficiency of shaping techniques of the current harmonic spectra taken from the DC network by VSI traction drive system, using the SHE and SHM modulation techniques. Regarding the fact that in 3 kV DC electric traction systems, fluctuations of the vehicle's supplying voltage are accepted in a wide range, it is necessary to determine the influence of voltage changes on the proposed modulation techniques. The research object is a simulation model of traction drive which consisting of an asynchronous motor fed by a voltage source inverter. The simulation model was verified by the means of measurements performed at a low scale laboratory stand. Analysis of the tested techniques when supplying voltage is fluctuating, allows to evaluate their usefulness in real operating conditions. The results obtained for SHE and SHM techniques were compared with SPWM modulation.

Selective Harmonic Elimination Based on Newton-raphson Method for Cascaded H-bridge Multilevel Inverter

&lt;span lang="EN-US"&gt;Multilevel inverters are emerging as the new breed of power converter options for high power applications. They typically synthesis the staircase voltage waveform (from several dc sources) which reduced harmonic content. This paper presents a simple selective harmonic elimination (SHE) modulation for single-phase cascaded H-bridge (CHB) multilevel inverter. The optimum switching angle of the transcendental equations describing the fundamental and harmonic components is solved by means of the Newton-Raphson (NR) method. The proposed SHE scheme is performed through simulation using MATLAB/Simulink. This simulation results are then verified through experiment using Altera DE0-Nano field-programmable gate array (FPGA). The proposed SHE is efficient in eliminating the lowest-order harmonics and producing a higher quality output waveform with a better harmonic profile. &lt;/span&gt;

Selective Harmonic Elimination Model Predictive Control for Multilevel Power Converters

In this study, a model predictive control (MPC) strategy that combines finite-control-set MPC with selective harmonic elimination (SHE) modulation pattern in its formulation is proposed to govern multilevel power converters. Based on a desired operating point for the system state (converter current reference), an associated predefined SHE voltage pattern is obtained as a required steady-state control input reference. Then, the cost function is formulated with the inclusion of both system state and control input references. According with the proposed reference and cost function formulation, the predictive controller prefers to track the converter output current reference in transients, while preserving the SHE voltage pattern in steady state. Hence, as evidenced by experimental results, a fast dynamic response is obtained throughout transients while a predefined voltage and current spectrum with low switching frequency is achieved in steady state.

Power Quality Analysis of HP Electric Drive based on 3L NPC AFE Rectifiers with SHE Modulation Method

This paper presents power quality analysis of high power (HP) electric drive based on three level neutral point clamped active front end (3L NPC AFE) rectifiers with selective harmonic elimination (SHE) modulation method. As an object of the study has been chosen a power circuit of main electric drive of rolling stand plate mill 5000 JSC "MMK". The main drive is a system in which each 12 MW motor is connected to the grid via 18-pulse connection circuit based on three 3L NPC AFE rectifiers and transformers connected in parallel. The rectifiers operate on the basis of SHE modulation method with elimination: 5, 7, 11 and 13; 5, 7, 17 and 19; 17, 19, 35 and 37 harmonics. The research results has been obtained on the primary and secondary side of the transformers by mathematical modeling and calculated voltage and current harmonic spectrums and total harmonic distortion (THD) at consumption of the rated current. A mathematical model was developed in Matlab/Simulink program. It was determined that SHE modulation method with elimination of 5, 7, 17 and 19 harmonics is the most appropriate for the considered object.

Grid Harmonics Compensation Using High-Power PWM Converters Based on Combination Approach

For high-power pulsewidth modulation (PWM) converters, selective harmonic elimination (SHE) modulation scheme is commonly adopted to reduce the low-order harmonics caused by a low switching frequency. However, the SHE scheme itself lacks the capability to actively compensate the grid background harmonics. To enable the active compensation ability of the SHE-modulated PWM converters, a selective harmonic compensation scheme and an SHE phase jittering method have been proposed in the previous works, and their effectiveness to actively attenuate the one grid line current harmonic was verified on a high-power PWM current-source rectifier (CSR) system application. Nevertheless, both the two methods have difficulty in compensating two harmonics simultaneously, which limits their applications with a low resonant frequency of converter system's filter circuit. This paper extends the previous studies to enable the high-power PWM converters to actively compensate two grid background harmonics. The proposed method can not only further reduce the grid line current distortion but also make the application of the active compensation no longer limited by the filter circuit. The experimental results of its application on a high-power PWM CSR system are provided to verify the effectiveness.

A Review of Multilevel Inverter Topology and Control Techniques

This paper focused on reviewing the main types of topologies and control strategies employed for the operation of multilevel inverter. Advantages and disadvantages of the topologies and the control techniques in relation to one another are equally reviewed. Recent proposed methods employed to improve the harmonic performance, reduce electromagnetic interference (EMI), lower stress on the power switches, eliminate DC link voltage imbalance and simplify the pulse width modulation control algorithms are fully reviewed. Selective harmonic elimination modulation technique is used in generating the 11-level of output voltage. It is aimed at reducing the total harmonic distortion as low as possible.

Minimization of Switching Losses in Grid Interfaced PV Inverters using SHE Modulation Strategy

Grid interfacing of multi-megawatt photovoltaic inverters is getting a closer attention in recent past. It is always a hard and challenging task for the engineers as there are certain priorities to be taken while interfacingPV cells to grid without which there will bean unsatisfactory operation of the system will taken. Somehow for high power and medium voltage grid invertersthe priorities like IEEE and IEC standards, satisfaction of grid codes and switching losses are to be strictly considered. Mitigation of switching losses is the active area of research for the PV systems. To meet such requirements weare using the traditional and conventional modulation strategy like SHE (Selective Harmonic Elimination). This paper focus on the reduction of switching losses with the help of new implementation technique for SHE that uses the third harmonics to have the switching angles over 90°, which also increases the modulation index. The Selective harmonic elimination strategy can allow the grid connected inverters to operate using a switching frequency less than 1 KHz while it is still able to provide satisfactory operation like simplicity in operation, independent control of active and reactive powers which is not possible in other cases. To validate potential benefits of SHE, it is compared with THI PWM which is controlled with an operating frequency of 2 KHz.