Optimal Switching Angles Research Articles

Analytical Evaluation and Reduction of Torque Harmonics in Induction Motor Drives Operated at Low Pulse Numbers

Induction motor drives operated with a low ratio of the switching frequency to the fundamental frequency (i.e., pulse number) are prone to have high magnitudes of low-order torque harmonics. This paper proposes a method to analytically evaluate the harmonic torque spectrum based on the pulsewidth-modulated voltage waveforms for low pulse number operation. The predicted torque harmonic spectra for different pulsewidth-modulated waveforms are validated through simulations and experiments. This paper also reports optimal switching angles to minimize the total rms value of torque harmonics of order 6, 12, 18 $,\dots,$ $6(N-1)$ , considering the number of switching angles per quarter ( $N$ ) to be 4 and 5. Compared to sine triangle pulsewidth modulation and selective harmonic elimination pulsewidth modulation with the same pulse number, the proposed optimal switching angles significantly reduce the total rms value of all harmonic torques of order lower than $6N$ . Extensive simulation and experimental results on a 3.7-kW induction motor drive are presented to demonstrate the superior performance of the proposed optimal pulsewidth modulation.

Effective utilisation of cascade H-bridge multi level inverter integrate social spider optimisation for reduced total harmonics distortion

The significance intention of the proposed method is to eliminate total harmonics distortion (THD) in solar photovoltaic cells powered cascaded H-bridge multilevel inverter (CHMLI). This purpose incorporates Newton-Raphson (NR), particle swarm optimisation (PSO), artificial bee colony (ABC), genetic algorithm (GA), cuckoo search (CS) and social spider optimisation (SSO)-based selective harmonic elimination technique for solving a non-linear transcendental equation to obtain optimal switching angle to achieve minimise THD. The foremost goal to reduce THD value beyond IEEE standard allowable limit is to predict optimal switching angle. This prediction is done in offline then it utilises for online simulation process to achieve minimised THD. Amid, aforementioned techniques incorporate with CHMLI; SSO behaves literally better than all other comparative techniques to attain 3.6% of THD in line voltage from the modulation index of 0.95. This customised product development would enhance quality power flow in this power generation.

Integrating multilevel converters application on renewable energy sources—A survey

Multilevel inverters emerged as the solution for overcoming the limitations of two level inverters, such as total harmonic distortion, high magnetic interference, and high dv/dt in high power voltage applications. The ability to generate sinusoidal output voltage is another speciality of multilevel inverters. The wide range of applications in fields such as power grids, motor drives, and Volt-Ampere Reactive compensation enhances the visibility of multilevel inverters. This paper identifies the conventional multilevel inverter topologies such as diode clamped multilevel inverters, flying capacitor multilevel inverters, and cascaded H bridges and presents a literature review on the topologies considering the facts of structural and functional diversities over the ages which have been adapted right from the beginning of its emergence. It also details the various optimization technologies that are used in multilevel inverters to obtain the optimal switching angle for harmonic elimination. This paper also explains the modulation techniques that are in effect for a specific purpose in different applications to get the best possible result.

Harmonic Elimination of Cascaded Multilevel Inverter using Metaheuristic Optimization Methods

The harmonic elimination of multilevel inverters is a complicated task that includes nonlinear transcendental equations. With the increase in the level of the multilevel inverter, the no of variables of the equation also increases which makes the problem more complicated. Metaheuristic optimization algorithms play an important role in finding out optimum switching angles required for elimination of harmonics in a lesser computational time avoiding multiple local minima. This paper deals with the harmonic elimination of cascaded multilevel inverter using whale optimization algorithm. The whale optimization method has the ability to escape local minima and it takes less time of computation of results. Results are verified theoretically by taking an example of a 15-level cascaded H-bridge inverter fed from equal d.c.sources. The above scheme well minimizes lower order harmonics and gives better output voltage and a low total harmonic distortion.

SBO-based selective harmonic elimination for nine levels asymmetrical cascaded H-bridge multilevel inverter

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.

Selective Harmonic Elimination With Optimal DC Sources in Multilevel Inverters Using Generalized Pattern Search

This paper presents the computation of optimal dc sources and switching angles using the generalized pattern search (GPS) optimization method for harmonic elimination in a cascaded multilevel inverter. The goal is to solve nonlinear equations for eliminating low-order harmonics and reaching desired fundamental component. For case study, 5- and 7-level inverters are chosen. The 7-level inverter with equal dc sources and 5- and 7-level inverters with an optimal dc source are applied to eliminate fifth and seventh harmonics. To obtain this goal, MATLAB software is used. Considering simulation results, cost, and simpler implementation, 5-level inverter with an optimized dc source is more effective in all modulation indexes in comparison with 7-level inverter. Also, results demonstrate the superiority of GPS over genetic algorithm (GA) in attaining accurate global minima. For better evaluation of optimizing more dc sources and GPS performance in comparison with GA, 7-level inverter with two optimal dc sources is applied to eliminate fifth, seventh, 11th, and 13th harmonics. Finally, to validate the accuracy of the 5-level inverter with an optimal dc source and GPS performance, the experimental results are provided for a 5-level cascaded H-bridge inverter.

Application of swarm optimisation‐based modified algorithm for selective harmonic elimination in reduced switch count multilevel inverter

Multilevel inverters (MLIs) are nowadays extensively used in integration with renewable energy sources and in drives applications. The converter cost and voltage quality improvement are the utmost importance in such application of MLI. A six-switch seven-level reduced switch symmetrical MLI (6S-7L MLI) is proposed here. Compared to the conventional and similar existing MLI topologies, the proposed MLI uses less active switches and has less driver circuit requirement. A particle swarm optimisation (PSO)-based modified selected harmonic elimination technique is derived and analysed for computing optimal switching angles of proposed 6S-7L MLI to eliminate third- and fifth-order harmonics. Moreover, the performance of the proposed algorithm is compared with the two most commonly used PSO variants. The analysis shows the modified version of PSO is most suitable for optimising the output voltage of proposed MLI through targeted harmonic elimination. The proposed topology is investigated through simulation by applying the calculated switching angles using modified PSO algorithm. Finally, a single-phase experimental prototype is designed to verify the validity of the proposed structure.

A PWM for Minimum Current Harmonic Distortion in Metro Traction PMSM With Saliency Ratio and Load Angle Constrains

Permanent magnet synchronous motor (PMSM) has the advantages of flexible structure, high power density, and low noise. It is promising to be developed into railway traction system. This application of the PMSM is limited by the low switching frequency of the high power traction inverter. Therefore, it is necessary to restrain the output current harmonics by using the optimized synchronous pulse width modulation (PWM) method. In this paper, the relationship between the load current of PMSM and the output voltage of the inverter using synchronous PWM is analyzed, and the expression of the current harmonics is deduced. Then, a new current harmonic evaluation index considering the saliency ratio and load angle constraints is proposed. Based on this, a novel current harmonic distortion minimization PWM (CHMPWM) algorithm for the PMSM is constructed. Compared with the two existing CHMPWM algorithms, the proposed optimized PWM has better harmonic performance at any modulation index and load angle. Furthermore, according to the results of the proposed CHMPWM, the influence of the load angle variation on optimal switching angle distribution is analyzed when pulse ratio is less than or equal to 11. Experimental results verify the feasibility and effectiveness of the proposed algorithm.

A Reactive Power Compensation Scheme for Unbalanced Four-Wire System Using Virtual Y-TCR Model

A modified scheme for reactive power compensation using static VAr compensators (SVCs) has been proposed in this paper for unbalanced four-wire system. The conventional SVC-based scheme requires both delta ( $\Delta $ $)$ - and star (Y)-connected SVCs for the same purpose. The proposed scheme uses a single-equivalent delta-connected thyristor controlled reactor (TCR) along with a combination of Y- and $\Delta $ - connected thyristor switched capacitors for this purpose. The single-equivalent $\Delta $ -TCR in the present scheme is the result of a virtual Y-TCR and the conventional $\Delta $ -TCR. This can reduces effective number of switching devices, cost, complexity, and space requirement compared to the conventional SVC-based schemes. Moreover, the proposed scheme can have various advantageous features compared to newly used DSTATCOM. The proposed scheme can also prevent injection of triplen harmonics in to the line, which is injected by Y-TCR in the conventional scheme. An optimized switching function is adopted in the proposed scheme for reduction of additional injected harmonics by TCR. The optimized switching angles are computed offline using gravitational search algorithm and stored in the processor memory for online application. The viability of the proposed scheme is simulated using MATLAB/Simulink and verified by suitable experimental results on a practical system.

Multilevel inverter switching controller using a field programmable gate array (FPGA)

This paper presents the design and development of a switching controller using a field programmable gate array (FPGA)for a multilevel inverter application. SHE with PSO switching strategy was chosen and pre-calculated offline to obtain optimized switching angles for the power switches in the 5-level transistor-clamped H-bridge (TCHB) multilevel inverter. The designed switching controller produced 5-bit control signals, which connected to the power switches of the 5-level TCHB multilevel inverter. The switching controller utilized less than 1% of the total FPGA logic elements (LEs), which was equivalent to 96 out of 114,480 LEs. The execution speed of the switching controller using the FPGA chip was found to be 99.9% faster than microcontroller (PIC16F877A). Conducted simulation and measurement results verified and validated the switching controller design functionality and requirement. Keywords : multilevel inverter, switching controller; FPGA, general purpose processor (GPP);digital signal processing (DSP); IGBT; Verilog, power consumption; harmonic elimination (SHE).

Effective Utilization of Cascade H Bridge Multi Level Inverter Integrate Social Spider Optimization for Reduced Total Harmonics Distortion

The significance intention of the proposed method is to eliminate total harmonics distortion (THD) in solar photovoltaic cells powered cascaded H-bridge multilevel inverter (CHMLI). This purpose incorporates Newton-Raphson (NR), particle swarm optimisation (PSO), artificial bee colony (ABC), genetic algorithm (GA), cuckoo search (CS) and social spider optimisation (SSO)-based selective harmonic elimination technique for solving a non-linear transcendental equation to obtain optimal switching angle to achieve minimise THD. The foremost goal to reduce THD value beyond IEEE standard allowable limit is to predict optimal switching angle. This prediction is done in offline then it utilises for online simulation process to achieve minimised THD. Amid, aforementioned techniques incorporate with CHMLI; SSO behaves literally better than all other comparative techniques to attain 3.6% of THD in line voltage from the modulation index of 0.95. This customised product development would enhance quality power flow in this power generation.

Differential Evolution Algorithm with Triangular Adaptive Control Parameter for SHEPWM Switching Pattern Optimization

Differential evolution (DE) algorithm has been applied as a powerful tool to find optimum switching angles for selective harmonic elimination pulse width modulation (SHEPWM) inverters. However, the DE’s performace is very dependent on its control parameters. Conventional DE generally uses either trial and error mechanism or tuning technique to determine appropriate values of the control paramaters. The disadvantage of this process is that it is very time comsuming. In this paper, an adaptive control parameter is proposed in order to speed up the DE algorithm in optimizing SHEPWM switching angles precisely. The proposed adaptive control parameter is proven to enhance the convergence process of the DE algorithm without requiring initial guesses. The results for both negative and positive modulation index (<em>M</em>) also indicate that the proposed adaptive DE is superior to the conventional DE in generating SHEPWM switching patterns

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

<span lang="EN-US">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. </span>

Microcontroller Based Multilevel Inverter for Photovoltaic System

This paper proposes the hardware design and implementation of a microcontroller based single-phase five-level cascaded Hbridge multilevel inverter for photovoltaic system. The inverter is capable of producing five levels of output-voltage levels (2V dc , V dc , 0, -V dc , and -2V dc ) from the dc supply voltage. Selective harmonic elimination pulse width modulation (SHEPWM) technique was employed to improve the output waveform quality. Digital optimized switching angles algorithm was implemented in a low cost processor ATMega 8535 to generate switching signal. The proposed system was verified through a small-scale laboratory prototype was built and tested. Its results indicated the proposed method's effectiveness and the application feasibility of the fundamental frequency switching.

Total harmonic distortion minimisation in multilevel inverters using the teaching–learning-based optimisation algorithm

ABSTRACTIn this article, the minimisation of total harmonic distortion (THD) of the output voltage of a multilevel inverter is studied. The harmonic component of output voltage in the inverter is reduced in THD minimisation. The output voltage THD in multilevel inverters is minimised by proper selection of switching angles. The teaching–learning-based optimisation algorithm is used to find the optimum switching angles in order to generate the desired voltage value in the possible minimum THD. Experimental and simulation results depict advantages of this approach compared to published papers which discus this concept using genetic algorithm. The experiments conducted on a seven-level inverter confirm the feasibility of this approach.

Control of a Uniform Step Asymmetrical 13-Level Inverter Using Particle Swarm Optimization

Harmonic Elimination Strategy (HES) has been a widely researched alternative to traditional PWM techniques. This paper presents the harmonic elimination strategy of a Uniform Step Asymmetrical Multilevel Inverter (USAMI) using Particle Swarm Optimization (PSO) which eliminates specified higher order harmonics while maintaining the required fundamental voltage. This method can be applied to USAMI with any number of levels. As an example, in this paper a 13-level USAMI is considered and the optimum switching angles are calculated to eliminate the 5th, 7th, 11th, 13th and 17th harmonics. The HES-PSO approach is compared to the well-known Sinusoidal Pulse-Width Modulation (SPWM) strategy. Simulation results demonstrate the better performances and technical advantages of the HES-PSO controller in feeding an asynchronous machine. Indeed, the harmonic distortions are efficiently cancelled providing thus an optimized control signal for the asynchronous machine. Moreover, the technique presented here substantially reduces the torque undulations.

THD Minimization from H-Bridge Cascaded Multilevel Inverter Using Particle Swarm Optimization Technique

In this paper, PSO (Particle Swarm Optimization) based technique is proposed to derive optimized switching angles that minimizes the THD (Total Harmonic Distortion) and reduces the effect of selected low order non-triple harmonics from the output of the multilevel inverter. Conventional harmonic elimination techniques have plenty of limitations, and other heuristic techniques also not provide the satisfactory results. In this paper, single phase symmetrical cascaded H-Bridge 11-Level multilevel inverter is considered, and proposed algorithm is utilized to obtain the optimized switching angles that reduced the effect of 5th, 7th, 11th and 13th non-triplen harmonics from the output voltage of the multilevel inverter. A simulation result indicates that this technique outperforms other methods in terms of minimizing THD and provides high-quality output voltage waveform

Investigations on Optimal Pulse Width Modulation to Minimize Total Harmonic Distortion in the Line Current

High-power and high-speed motor drives have only a few switching transitions in each line cycle. Pulse width modulation (PWM) waveforms with positive voltage transition at the positive zero crossing of the fundamental voltage (type-A) are generally considered for PWM waveform with an even number of switching angles per quarter, whereas waveforms with negative voltage transition at the positive zero crossing (type-B) are considered for an odd number of switching angles per quarter. Optimal switching angles to minimize the total harmonic distortion (THD) in motor current are reported for both type-A and type-B waveforms of pulse numbers ( $P$ ) of 5, 7, 9, and 11. Based on simulation and experimental studies on a $3.7$ kW induction motor (IM) drive, optimal type-A and type-B PWM methods are shown to be better than each other in different modulation ranges for each pulse number. The space vector based analysis of optimal type-A and type-B waveforms brings out the optimal vector sequence at any modulation index for a given $P$ . Findings of the space vector based analysis lead to a new approach for determining optimal switching angles with much reduced computational effort. Compared to sine-triangle PWM, deployment of optimal vector sequences in an IM drive, having a maximum switching frequency of 250 Hz, leads to significant reduction in both THD of line current as well as motor losses over a wide range of speeds and load conditions.

An improved OMTHD technique for an $n$-level cascaded multilevel inverter with adjustable DC sources

Optimal minimization of total harmonic distortion (OMTHD) and selective harmonic elimination (SHE) switching techniques are usually employed to reduce generated harmonics of multilevel inverters. In the former technique, the THD of waveform is reduced without elimination of any harmonic order and the latter, in contrast, eliminates selected harmonic orders. In this paper, the harmonic elimination ability of the SHE technique is added to OMTHD and an improved OMTHD technique is proposed for an n-level cascaded multilevel inverter with adjustable DC sources. The main novelty of this switching technique is elimination of some harmonic orders, beside THD minimization. Moreover, optimal DC voltages and switching angles can be estimated simpler than conventional OMTHD technique. To show the advantages of the proposed technique, which is formulated for an n-level inverter, a 7-level one is simulated in MATLAB/Simulink with both improved and conventional OMTHD techniques. The obtained results show the elimination of two elective harmonics as well as THD minimization. Moreover, experiments on a 7-level inverter verify the superiority of the proposed technique.

Harmonic Optimization in Voltage Source Inverter for PV Application using Heuristic Algorithms

Abstract Selective Harmonic Elimination (SHE) technique is the fundamental switching frequency scheme that is used to eliminate specific order harmonics. Its application to minimize low order harmonics in a three level inverter is proposed in this paper. The modulation strategy used here is SHEPWM and the nonlinear equations, that characterize the low order harmonics, are solved using Harmony Search Algorithm (HSA) to obtain the optimal switching angles that minimize the required harmonics and maintain the fundamental at the desired value. Total Harmonic Distortion (THD) of the output voltage is minimized maintaining selected harmonics within allowable limits. A comparison has been drawn between HSA, Genetic Algorithm (GA) and Newton Raphson (NR) technique using MATLAB software to determine the effectiveness of getting optimized switching angles.