Switching Angles Research Articles

Selective harmonic mitigation based two-scale frequency control of cascaded modified packed U-Cell inverters

A new Modified Packed U-Cell (MPUC) converter architecture with cascading is proposed in this paper. To provide an output voltage of 25 levels, the proposed cascaded MPUC needs only twelve power switches and four power sources. The converter comprises two cascaded MPUCs with DC supply in a ratio of 5:1. One converter is operating at low frequency (LF) and the other at high frequency (HF) that leads to lower power losses and higher levels. Besides, a variable frequency method is anticipated to produce a 25-level output voltage which has low harmonic content (THD) with the help of Selective Harmonic Mitigation (SHM). The optimum switching angles for SHM are obtained through solving the SHM equations using the Genetic Algorithm (GA). The designed controller is efficient and suitable for applications that require low-frequency operation either in stand-alone or grid-tied. The proposed inverter and its operation procedure have been investigated using MATLAB®/Simulink software, and the findings demonstrate that the proposed inverter output voltage has reduced THD significantly. The simulation results are verified using the typhoon HIL-402 emulator. Also, the power loss analysis is done using PLECS. The maximum efficiency of the converter is found to be around 98.34%. The simulation results justified the efficiency and viability of low 25-level THD voltages.

ДОСЛІДЖЕННЯ СПОСОБІВ КЕРУВАННЯ ВЕНТИЛЬНО-ІНДУКТОРНИМ ПРИВОДОМ НАСОСНОГО ОБЛАДНАННЯ З ЦИКЛІЧНИМ НАВАНТАЖЕННЯМ

The electromechanical water supply system of a multi-storey building based on a switched reluctance motor is considered. A simulation model of the hydraulic network and criteria for evaluating the quasi-steady modes effectiveness of pumping equipment are given. A study of a centrifugal pump operational and energy characteristics has been carried out when adjusting its rotational speed to determine the frequencies at which the compliance of the pump pressure and flow with the hydraulic network requirements is ensured. Simulation models of control systems have been developed that provide the switched reluctance motor speeds at levels corresponding to specified flow rates of the hydraulic system pumping equipment, by means the phase voltage pulse-width regulation or the phase current limitation level adjustment. Comprehensive studies and comparative analysis of the switched reluctance centrifugal pump drive control principles were carried out according to the criteria for evaluating energy efficiency when regulating the rotational speed and changing the switching angles. As a result of this study, it was found that both pumping unit drive control principles provide its necessary productivity and are close in efficiency - a slightly higher efficiency can be achieved using the phase voltage pulse-width regulation of the switched reluctance motor with a changing the switching angles. References 10, figures 8.

A Simple Staircase Modulation for A Cascaded H-bridge Multilevel Inverter

This paper proposes a novel simple staircase modulation to obtain reasonable performance of an output voltage for a cascaded HBridgemultilevel inverter. The motivation of the proposed algorithm is that the inverter phase voltage intersects with an original sinusoidalwaveform at equal points in the y-axis. This modulation technique can calculate the independent switching angles more simply than thetraditional method, which employed Fourier’s series analysis, and can be applied to all kinds of multilevel inverters. In this paper, for the sake of validation, the technique was applied to a cascaded H-bridge inverter with unequal DC sources. Then, it was applied to the seventh, ninth, eleventh, and twenty-seventh levels of the multilevel inverter. In addition, pulse width modulation techniques used in this type of multilevel inverter are complicated. The PSIM software program was used for all simulation examples, and its results are consistent with the experimental results.

Low and High Frequency Control Strategy for Asymmetrically Switched Cascaded Multilevel Inverter

This paper proposes low and high frequency control techniques for asymmetrically switched cascaded multilevel inverters (MLI). Initially, Low frequency-based switching angle calculation methods are proposed for the suggested topology. Then high frequency-based Multi-carrier pulse width modulation (MCPWM) techniques are used to control the switching states of multilevel inverters for asymmetrical sources. The proposed multilevel inverter is a reduced switch topology with a modular version realized. From the modular version of the topology, three asymmetrically switched (7, 13 & 21) levels are simulated by MATLAB/Simulink environment and comparisons among themselves are also considered according to method of switching techniques and power quality, i.e. total harmonic distortion (THD). The designed inverters are recommended for photovoltaic power generation as they are suitable to integrate separate DC power sources. The inverters are designed and simulated with a proper simulation environment and experimentally verified through hardware in loop (HIL) using OPAL-RT (OP-5600) testbed.

Multilevel Selective Harmonic Modulation via Optimal Control

We consider the Selective Harmonic Modulation (SHM) problem, consisting in the design of a staircase control signal with some prescribed frequency components. In this work, we propose a novel methodology to address SHM as an optimal control problem in which the admissible controls are piecewise constant functions, taking values only in a given finite set. In order to fulfill this constraint, we introduce a cost functional with piecewise affine penalization for the control, which, by means of Pontryagin’s maximum principle, makes the optimal control have the desired staircase form. Moreover, the addition of the penalization term for the control provides uniqueness and continuity of the solution with respect to the target frequencies. Another advantage of our approach is that the number of switching angles and the waveform need not be determined a priori. Indeed, the solution to the optimal control problem is the entire control signal, and therefore, it determines the waveform and the location of the switches. We also provide numerical examples in which the SHM problem is solved by means of our approach.

Power Quality Improvement in a Solar PV Assisted Microgrid Using Upgraded ANN-Based Controller

This paper proposes the design of a controller using the artificial neural network (ANN) for a solar photovoltaic (PV)-fed cascaded multilevel inverter (CMLI) to enhance the power quality. The objective of this presented ANN controller is to obtain a maximum output voltage with no filter components. This paper also investigates and eliminates the voltage harmonics that occurred in a solar-fed cascaded 3-stage inverter using various techniques such as pulse width modulation (PWM), digital logic control (DLC), fuzzy logic controller (FLC), and ANN, and the results are compared. Based on the results, the proposed ANN-based controller efficiently reduces harmonics and improves the power quality. This is achieved by solving the harmonic equations and thereby changing the switching angles of each semiconductor to a minimum value. The ANN is trained by a dataset consisting of varying input voltage and switching angles. The simulation was performed using MATLAB/Simulink for different types of controllers like PWM, DLC, FLC, and ANN for the 3-stage inverter. The simulated results are compared with the results obtained from a 3 kWp photovoltaic plant connected to the CMLI. Finally, on the basis of performance analysis, it was confirmed that the ANN-based controller effectively eliminates harmonics and improves the power quality.

Online Unified Solution for Selective Harmonic Elimination Based on Stochastic Configuration Network and Levenberg–Marquardt Algorithm

In this article, an online unified solution based on stochastic configuration network (SCN) and Levenberg– Marquardt (LM) algorithm is proposed to generate optimal switching angles for selective harmonic elimination (SHE) in both the symmetric and asymmetric cascaded H-bridge (CHB) multilevel inverters (MLIs). Different from the traditional neural network framework for SHE, this unified solution uses SCN to only generate initial values of the switching angles online, which significantly reduce the precision demand on training SCN and avoids the local optima problem of gradient descent algorithm. After obtaining the initial values from SCN online, the LM algorithm can be used to rapidly solve the exact switching angles for SHE, which guarantees the solving efficiency and precision of the final solutions. Moreover, the stability of the proposed method is proved via Newton-like convergence theory. Compared with intelligent search algorithms and look-up table method, the proposed solution can not only online generate optimal theoretical switching angles but with much fewer data storage space. Experimental results of both symmetric and asymmetric MLI cases are presented to validate the correctness and online applicability of the proposed solution.

Differential Evolution Applied to a Multilevel Inverter—A Case Study

This work aims to obtain the switching angles to reduce the total harmonic distortion (THD) and compare the different sets of angles obtained by modifying the modular index (Mi) in a seven-level multilevel inverter using the differential evolution (DE) algorithm. A seven-level cascaded multilevel inverter with RL load was simulated in MATLAB Simulink. The Mi was varied (0.6 to 1.27) to check which set of switching angles is optimal to reduce the THD. These sets of angles are then experimentally validated on a test bench. A brief discussion of the results is presented, comparing the minimum THD found without considering Mi, versus the minimum THD obtained if Mi is less than 1.

Application of Newton Identities in Solving Selective Harmonic Elimination Problem With Algebraic Algorithms

Algebraic algorithms are powerful methods in solving the selective harmonic elimination (SHE) problem, which can find all exact solutions without the requirements of choosing initial values. However, the huge computational burden and long solving time limit the solving capability of algebraic algorithms. This article presents a novel Newton’s identifies-based method to simplify the SHE equations including the order reduction and the variable elimination, thereby reducing the computational burden and the solving time of algebraic algorithms or in other words improving the solving capability of the algebraic algorithms. Compared with existing simplification methods, the proposed method significantly improves the efficiency of solving SHE equations. With the proposed method, the degree of reduction is no longer the bottleneck of solving the SHE equations by using algebraic algorithms. By using the proposed method, the SHE equations with ten switching angles are completely solved with the algebraic algorithm for the first time. The simulation and experimental results indicate that the proposed method is effective and correct.

Real-Time Harmonic Optimization in Multilevel Inverter Using Artificial Neural Network (ANN)

Multilevel inverters (MLIs) are increasingly used in real time applications. Among several pulse width modulation (PMW) techniques currently deployed for the control of MLIs, selective harmonic elimination PWM (SHEPWM) technique arguably gives the best performance due to its direct harmonic mitigation capability. However, real time application of SHEPWM technique is presently infeasible due to the heavy computational cost involved in solving the transcendental nonlinear equations known as selective harmonic elimination (SHE) equations, which characterize the harmonics that are selected for elimination or mitigation. This paper presents a twostage approach to the online generation of switching angles that mitigate selected lower-order harmonics in multilevel inverters. The first stage involves an offline solution of SHE equations using ant colony optimisation (ACO). In the second stage, ACO computed results are used to train an artificial neural network (ANN) predictive model. The results obtained from the simulation of the proposed method in MATLAB/SIMULINK environment show that the method is highly efficient and accurate.

Dragonfly Algorithm-Based Optimization for Selective Harmonics Elimination in Cascaded H-Bridge Multilevel Inverters with Statistical Comparison

Harmonics worsen the quality of electrical signals, hence, there is a need to eliminate them. The test objects under discussion are single-phase versions of cascaded H-bridge (CHB) multilevel inverters (MLIs) whose switching angles are optimized to eliminate specific harmonics. The Dragonfly Algorithm (DA) is used to eradicate low-order harmonics, and its statistical performance is compared to that of many other optimization techniques, including Particle Swarm Optimization (PSO), Accelerated Particle Swarm Optimization (APSO), Differential Evolution (DE), and Grey Wolf Optimization (GWO). Various scenarios of the algorithms’ search agent population for inverters with seven, nine, and eleven levels of output voltages are comprehensively addressed in this research. No algorithm shows total dominance in every scenario. The DA is least impacted by the change in dimensions of the narrated problem.

PMSM Torque Ripple Minimization Based on Novel Low Carrier Ratio PWM Technique

Harmonic injection is commonly used in permanent magnet synchronous motor torque ripple minimization (TRM) of electric vehicle. Traditional inverter switching frequency limits TRM application at high speed due to harmonic modulation accuracy and inverter loss. To achieve TRM in the whole speed range and reduce inverter loss, a novel online calculated low carrier ratio pulsewidth modulation (LCRPWM) is proposed in this article. The carrier ratio determining regular according to the injected harmonics is established first. The relationship between injected harmonics and LCRPWM switching angle is revealed and a set of nonlinear equations is established. Thus, the problem is transformed from solving nonlinear equations into optimization by establishing a cost function. The analytical solutions of nonlinear equations are obtained, which avoids iterative operation and plunging into local minimum. Therefore, the switch angle solution method is suitable for online calculation. The LCRPWM is verified in simulation compared with the traditional regularly sampled space vector PWM, which achieves better results in voltage harmonic injection and flux tracking at a much lower switching frequency. At last, the LCRPWM is used in a test bench experiment that shows good TRM effects. The influence of sideband harmonics on torque ripple is analyzed.

Modified teaching learning based optimization for selective harmonic elimination in multilevel inverters

Renewable Energy sources are becoming an important source of energy generation. Battery energy storages systems are used to supply the power when there is variation in power generation due to climate change. Power stored in batteries need to be converted from Direct current (DC) into Alternating current (AC) current to integrate it with the grids. This paper presents the modification in a recently emerged teaching learning-based optimization (TLBO) to be implemented in multilevel inverters. The results obtained from proposed modified TLBO has been compared with existing TLBO, Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Artificial Bee Colony (ABC), and Imperialistic Competitive Algorithm (ICA). Furthermore, the proposed algorithm has been tested for four well-known mathematical functions like Greiwangks, Ackley’s Dejon’s and Drop wave and find out that the proposed algorithm has a better convergence rate than normal TLBO. Finally, the optimized switching angles obtained from the proposed algorithm has been tested in SIMULINK by designing an 11-level cascaded H-bridge multilevel inverter and observe the magnitude of individual harmonics. The results obtained from the proposed algorithm shows the better harmonic reduction while comparing with other algorithms.

Design and Analysis of Partial shading of the PV System Integrated with High-Frequency Inverter and Rectifier Operation for the Electric Vehicle

Solar photovoltaic cells are in high demand for sustainable energy generation because of their capacity to provide direct power. As a result, DC-DC converters that can enhance the output voltage and do so reliably while eliminating changes in solar panel outputs are required. Inconsistencies in sun-light availability, ambient temperature, and shadows, among many other considerations, cause the fluctuations. Compared to the typical DC-DC Boost converter, the suggested converter architecture has a higher efficiency of over 95%. In a resonant inductive coupled power transmission system for an electric vehicle, this research demonstrates partial shading of a 250-W PV solar-powered interfaced with a high-frequency resonant full-bridge inverter. The suggested system’s DC input is provided by a PV panel. The ratio of DC Input sources supplied to the high-frequency inverter is 1:3. For a fixed modulation of 0.7, the step modulated for a high-frequency inverter uses a pre-calculated switching angle. Due to a very high-frequency AC connection, the suggested system is more efficient than a traditional system of 50 Hz inverter operation and multiple-output transformer architecture. Zero Voltage Switching (ZVS) is ensured in this study, which decreases switching losses. In the MATLAB/ SIMULINK environment, the suggested approach has been validated. The research aims to investigate and illustrate the effect of partial shading with and without a bypass diode on the I (V) and P (V) properties of solar panels. Hence, the suggested approach’s performance is compared to the present method in terms of parameters, and 95 percent efficiency may be attained. When compared to shaded and unshaded situations, this paper displays greater feature modifications.

A Novel Approach for Mitigating Power Quality Issues in a PV Integrated Microgrid System Using an Improved Jelly Fish Algorithm

A two-step methodology was used to address and improve the power quality concerns for the PV-integrated microgrid system. First, partial shading was included to deal with the real-time issues. The Improved Jelly Fish Algorithm integrated Perturb and Obserb (IJFA-PO) has been proposed to track the Global Maximum Power Point (GMPP). Second, the main unit-powered via DC–AC converter is synchronised with the grid. To cope with the wide voltage variation and harmonic mitigation, an auxiliary unit undergoes a novel series compensation technique. Out of various switching approaches, IJFA-based Selective Harmonic Elimination (SHE) in 120° conduction gives the optimal solution. Three switching angles were obtained using IJFA, whose performance was equivalent to that of nine switching angles. Thus, the system is efficient with minimised higher-order harmonics and lower switching losses. The proposed system outperformed in terms of efficiency, metaheuristics, and convergence. The Total Harmonic Distortion (THD) obtained was 1.32%, which is within the IEEE 1547 and IEC tolerable limits. The model was developed in MATLAB/Simulink 2016b and verified with an experimental prototype of grid-synchronised PV capacity of 260 W tested under various loading conditions. The present model is reliable and features a simple controller that provides more convenient and adequate performance.

Neural network based harmonic elimination in single-phase inverters

PurposeThis study aims to present the experimental results for neural network (NN) based harmonic elimination technique for single-phase inverters.Design/methodology/approachSwitching angles applied to power switches are determined using the NN technique based on the harmonics to be suppressed. Thus, besides controlling the output voltage, NN controller provides elimination of predetermined harmonics from output signal of single-phase inverter. Simulation and experimental results for the elimination of 15 and 20 low-order harmonics are presented. The switching angle values calculated by a NN , fuzzy logic and Newton–Raphson are compared for elimination of first 10 harmonics.FindingsThis paper provides the harmonic spectra showing that first 15 and 20 harmonics are suppressed from output signal. The NN is proved to give closest results to angle values calculated by Newton–Raphson’s numerical solution method.Originality/valueThe value of this paper is to verify the simulation results with the experimental result for the elimination of 15 and 20 low-order harmonics. Both the simulation and the experimental results demonstrate the success of the NN based selected harmonic elimination.

Staircase modulation improvement to balance output power of stages of cascade H-bridge multilevel inverter

In this study, different methods are investigated to minimize the power imbalance between the stages of a cascade H-bridge (CHB) multilevel inverter (MLI). First-in-first-out (FIFO) and first-in-last-out (FILO) are two common staircase-modulation (SCM) methods. A CHB-MLI with FIFO modulation, even with the same conduction times, cannot distribute power equally between the stages. A new algorithm is presented in this study to balance the power between the inverter stages. This is important to increase the lifetime of the PV sources that feed the inverter. To implement the new algorithm, all possible switching patterns based on the angles obtained from the nearest level of control (NLC) method are defined as the sample spaces of random variables. Subsequently, a random vector is defined for a set of random variables, and an optimization problem with finite and discrete solutions is applied. This algorithm is effectively used to minimize the power imbalance between the stages, even in impedance loads, from the purely inductive to the pure capacitive range. In addition, with slight changes in the switching angles, the operation of the stages and the inverter efficiency increases. Finally, the simulation and experimental results confirm the validity and practicality of the proposed modulation.

Reptile Search Algorithm (RSA)-Based Selective Harmonic Elimination Technique in Packed E-Cell (PEC-9) Inverter

The multilevel inverters (MLIs) are capable of handling large quantities of power and generating high-quality output voltages. Consequently, the size of the filters is reduced, and the circuitry is simplified. As a result, they have a diverse range of uses in the industrial sector, especially in smart grids. The input voltage boosting feature is required to utilize the MLI with renewable energy. In addition, a large number of components are required to attain higher output voltage levels, which increases the cost of the circuit and weight. A variety of MLI topologies have been identified to reduce losses, device quantity, and device ratings. The selective harmonic elimination (SHE) approaches reduce distinct lower order harmonics by computing the ideal switching angles. This research presents a nine–level Packed E–Cell (PEC–9) inverter that uses selective harmonic elimination to eliminate total harmonic distortion. In order to calculate the best switching angle, the reptile search algorithm (RSA) is implemented in this paper, a nature–inspired metaheuristic algorithm inspired by the hunting behavior of the crocodile. The hunting behavior of crocodiles is implemented in two main steps: the first is encircling, which is accomplished by belly walking or high walking, and the second is hunting, which is accomplished by hunting cooperation or hunting coordination. In this technique, nonlinear transcendental equations have been solved. The simulation was run in the MATLAB R2021b software environment. The simulation results suggest that the RSA outperforms the other metaheuristic algorithms. Furthermore, the simulation result was validated on a hardware setup using DSP–TMS320F28379D in the laboratory.

Ferroelectric liquid-crystal modulator with large switching rotation angle for polarization-independent binary phase modulation

In this work a ferroelectric liquid crystal (FLC) modulator with a non-standard large switching rotation angle, close to 90∘, is fabricated and characterized. The modulator acts as a switchable wave-plate with an in-plane rotation of the principal axis under the action of a bipolar voltage. In the ideal situation of half-wave retardance, the device is shown to behave as a binary π phase modulator independently of the input state of polarization. We provide physico-chemical properties of the liquid crystalline mixture used to fabricate the FLC modulator with such large switching angle. The characterization method of the device optical properties is presented, which allows the localization of the two LC stable states, the unambiguous determination of the rotation angle, and the evaluation of the spectral retardance function. We demonstrate the polarization-independent π phase shift using an adapted Young's type interferometer for real-time measurements, where we further analyze the operational frequency limits of the device. This FLC operational mode can be exploited to produce binary-phase polarization-independent diffractive optical elements.

Comparative Study of Multiphase 5-Level Cascaded H-Bridge Multilevel Inverter System

In terms of cost and structural design, the cascaded H-bridge multilevel inverter (CHBMLI) has a significant advantage over diode clamped and capacitor clamped multilevel inverters. The total harmonic distortion (THD) of a 5-level CHBMLI system for three different phases (single-phase, three-phase, and six-phase system) is studied and compared in this work. As switching angles play a role in lowering THD, the switching angles for a 5-level CHBMLI are evaluated using four specific switching angle methods in the initial section of this paper. In the simulation of single-phase system, these angles are being utilized. The angles with the lowest THD value are chosen for three-phase and six-phase system simulation. Based on the findings, the higher phase of 5-level CHBMLI is more efficient in decreasing harmonics.