Hybrid optimization approach for optimal switching loss reduction in three-phase VSI

With rapid advancement in technologies used in solid-state electronics, nowadays, the conversion and control of electrical power has become easy due to inclusion of power electronics-based devices. With the help of these devices, accurate and smooth control of electrical power conversion can be consummated in three-phase voltage source inverters. But uses of power electronics devices also result in Total Harmonic Distortion (THD), which distorts overall system performance. Eliminating some selected harmonic in a system can quickly be done by using optimization techniques. This manuscript focuses on analysis of harmonics in a 3-phase voltage source inverter using Gravitational Search Algorithm (GSA) and Particle Swarm Optimization (PSO) technique.

This paper compares the efficiencies of insulated gate bipolar transistor-based voltage and current source inverters. Test circuits that replicate the functionality of a single switching pole of each converter topology are used to measure the switching trajectories and loss characteristics of the semiconductor devices. These results are then used to simulate the losses for complete 3-phase voltage and current source inverters. Switching losses are shown to be dominant in the voltage source inverter whilst conduction loss is dominant in the current source inverter. It is shown that neither power converter operates more efficiently than the other over the complete operating range, with an equivalently rated voltage source inverter being preferable at lower power levels and the current source inverter being more efficient at higher power levels. (6 pages)

Harmonics can be characterized as components with periodic waveforms having multiples of a fundamental frequency. Harmonics, one of the most critical issues of power quality, have recently come into prominence despite being known in advance. Many scientists and researchers have suggested various methods for decreasing or eliminating these low-order and high-order harmonics since the early time of the ac power systems. Selective Harmonic Elimination Method (SHEM) in the proposed methods is shown superior performance on low-order harmonics in low switching frequencies. Various Meta-Heuristic Algorithms (MHA) are used to solve the equations included in this method and to reduce the computational burden. In this study, Grey Wolf Optimizer (GWO) which is a metaheuristic method added to literature in recent history, is applied to 3-phase Voltage Source Inverter (VSI) system using SHEM for harmonic elimination. GWO technique is analyzed and implemented for calculating the switching angles for Voltage Source Inverter (VSI). Total harmonic distortion (THD) values of GWO and without GWO methods of the inverter system are also compared with Cuckoo Search (CS) and Genetic Algorithm (GA). Our results show that using GWO method eliminates low-order harmonics and reduces THD value of the system according to power quality standards.

Bus-clamping Pulse Width Modulation (PWM) is an effective method to reduce the switching loss in a three-phase voltage source inverter (VSI). In bus-clamping PWM scheme, the phase legs are switched using high frequency PWM signals for two-third of the line cycle, while for the remaining duration of cycle, the pole voltage is clamped to either positive or negative rail of the DC bus. In PWM operation of a half bridge, a dead-time is applied between the gate signals of complementary switches to ensure safe and reliable operation. However, introduction of dead-time leads to poor power quality, increased Total Harmonic Distortion (THD) and variation in actual voltage compared to the intended pole voltage. Moreover, when the bus-clamping technique is used, the PWM has both high frequency switching region and clamped region in a line cycle, and consequently, the undesired effects of dead-time are further aggravated. Therefore, in order to enhance the quality of output voltage, this paper presents a dead-time compensation strategy for a VSI operating with bus-clamping PWM. The proposed method calculates the required compensation term to be added on the modulation signal considering wide range of operating conditions. Additionally, the compensation includes a new strategy for low current conditions near zero-crossing to avoid distortion. The proposed method is verified by simulation and experiments in a three-phase VSI with a switching frequency of 100 kHz and a fundamental frequency of 60Hz.

Technological developments such as Flexible AC Transmission Systems (FACTS) can improve the power quality of the power system and can respond to the ever-increasing demand for electrical energy.Superconducting magnetic energy storage (SMES) is a FACTS device that has been used for several years at utility and industrial sites throughout the United States, Japan, Europe, and South Africa to provide both transmission voltage support and power quality to customers who are vulnerable to fluctuating power quality [1]- [3].SMES systems are classified into two groups: voltage source inverter (VSI) and current source inverter (CSI) SMES.The VSI SMES has many advantages when compared with the CSI SMES; for example, in the VSI SMES, the power rating of power electronic devices that are used in the inverter is much less than that of the CSI SMES, resulting in fewer switching and power losses.Also, the VSI SMES can be used as a Static synchronous Compensator (STATCOM) when its chopper is out of service.Moreover, for the same condition, the VSI SMES can store more energy than the CSI SMES; these advantages encouraged the authors to study VSI SMES.This type of SMES is composed of a magnetic energy storage coil with various structures and power conditioning systems that are also composed of different parts, such as AC-DC filters, a multi-level chopper, a capacitor bank, and a multi-level converter (i.e. an inverter or rectifier).These power conditioning systems are also used in many different sustainable energy systems, such as bio fuels, solar power, wind power, wave power, geothermal power, and tidal power.The converter is an interface between the power network and the capacitor bank and controls the electrical energy exchange between the two.Likewise, the chopper is also an interface between the magnetic energy storage coil and the capacitor bank, and controls electrical energy exchange between them.To store the electrical energy in the capacitor bank and the magnetic energy storage coil in the range of mega joules, it is necessary to employ high power-rating converters; to overcome the limitations of the current and voltage range of the semiconductors, multi-level converters are used.The advantages of using such converters include reducing voltage on the switches, harmonic order correction, decreasing or eliminating lateral equipment, decreasing switching frequency, decreasing total harmonic distortion (THD), decreasing switching losses, and decreasing the output current ripple.

The pulse width modulation (PWM) strategy employed in the voltage source inverter (VSI) not only control the magnitude of the output voltage but also the quality. Performance evaluations of such strategies are done in terms of fundamental voltage, total harmonic distortion (THD), switching losses etc. (primary indices) and also in terms of acoustic noise, electromagnetic interference (EMI), harmonic spread factor, distribution of harmonic power etc. (secondary indices). Multilevel inverter (MLI) has become unanimous choice in medium and high power applications due to their superior performance compared to three level inverters. The conventional Sub-Harmonic PWM (SHPWM) scheme and its variations offer the output voltage spectrum with high intensity harmonic components around the switching frequency; it will end with cluster harmonic with high acoustic noise. The first objective of this paper is to investigate harmonic spreading effects of existing multilevel inverter (MLI) strategies. Secondly the developing innovative PWM strategies for MLIs based on modified reference and carrier functions, which were proved for superior the primary indices at three-level VSI. Thorough simulation study of Pulse width modulation strategies such as SHPWM, inverted sine carrier PWM, MWM PWM, third harmonic injection PWM, triplen harmonic injection PWM, analog space vector PWM, trapezoidal PWM and discontinuous PWM for a cascaded multilevel inverter, are presented with results of primary and secondary indices. Hence, the PWM strategies of MLI are evaluated for harmonic spreading effect first time and a guide line for a beginner to select the PWM scheme for MLI fed drive systems is stenciled.

Variable switching frequency hybrid PWM technique for switching loss reduction in a three-phase two-level voltage source inverter

The latest trend in modern industrial application is the use of variable voltage supply to the AC drives from a three phase voltage source inverter (VSI). Different types of Pulse Width Modulation (PWM) scheme are used to modulate output voltage of VSI. The most commonly used PWM schemes for three-phase VSI are carrier-based sinusoidal PWM and Hybrid Space Vector PWM (HSVPWM). Researchers adequately prefer the use of HSVPWM because of their easier digital realization and better dc bus utilization. The advantages of HSVPWM are reduction of total harmonic distortion, improvement in output voltage and reduction of torque ripple in induction motor drives. This paper provides a comprehensive literature review on different topologies of HSVPWM. These includes Advanced Bus Clamped SVPWM (ABCSVPWM), Neutral Point Clamped SVPWM (NPCSVPWM) and Diode Clamped SVPWM (DCSVPWM).

ABSTRACTThe present study explores the influence exerted by various pulse width modulation (PWM) techniques upon harmonic distortion and switching losses of a voltage source inverter. In the context of this inquiry, a generalized algorithm for variable frequency operations, inspired by continuous and discontinuous PWM is outlined in this article. The algorithm is explicitly formulated as a function of fundamental frequency and the load power factor angle with the objective of minimizing total harmonic distortion (THD) and switching losses within a specified frequency range. The algorithm is segmented into various regions of frequency, guided by the theory that each region corresponds to a distinct PWM technique that yields reduced harmonic distortion. In this article, a minimum switching loss algorithm is introduced and implemented using both BCPWM and ABCPWM techniques. The algorithm is specifically designed to minimize switching losses across the entire range of load power factor angles. The integration of switching loss algorithm with the selection of the optimal PWM technique across different frequency ranges results in reduced switching losses and harmonic distortion. This leads to a comprehensive PWM algorithm that efficiently reduces both THD and switching losses during dynamic frequency and load changes. Experimental and theoretical evidences demonstrate the efficacy of the proposed algorithm in attaining minimum harmonic distortion and reduced switching loss operation during variations in fundamental frequency and load.

Conventional Sinusoidal Pulse Width Modulation (SPWM) topology is one of the essential Pulse Width Modulation (PWM) topologies used in Voltage Source Inverter (VSI) applications such as adjustable speed motor control, Uninterrupted Power Supplies (UPS) and Photovoltaic (PV) Systems. Although conventional SPWM is used in VSI applications, the output voltage waveform of VSI based on this topology contains a high content of harmonic distortion. Hence, this paper presents a modified SPWM topology with an Artificial Neural Network (ANN) technique. The ANN technique was applied to minimize the Total Harmonic Distortion (THD) present in the output voltage waveform of the VSI. The proposed system was designed and evaluated with MATLAB/Simulink software. Based on the comparative evaluation, the paper proves that the proposed system contributes to a 9.1 % reduction in the THD value of a three-phase two-level VSI's output voltage waveform.

Optimal design of shunt active power filter for power quality enhancement using predator-prey based firefly optimization

Recent R& D advances on megawatt power, high-frequency nanocrystalline transformer [1] and high-voltage, high-frequency SiC based semiconductor devices [2] present possibility of a shift in the design of high-power inverters from a one based on complicated structure with line-frequency switching to the one based on simple topology and operates at 10 - 20 kHz frequency. In line with these ongoing advancements, in this paper, a summary of performance for a multiphase high-frequency-link (HFL) high-power inverter using a new innovation (here after referred to as ldquohybrid modulationrdquo [3] - [5]) have been outlined in the presence of hard-switched and soft-switched front-end. Unlike conventional constant-dc-link inverters, the hybrid-modulation-based inverter applies a high-frequency pulsating dc link voltage to the output ac/ac stage, whose structure is identical to a three-phase voltage source inverter (VSI). The former has comparable bus voltage utilization and total harmonic distortion (THD) performance as the conventional constant dc-link VSI but possesses other additional advantages such as: 1) elimination of dc filter; 2) reduced switching and conduction losses of high-voltage switches; and 3) reduced RMS current and di/dt stress of high-voltage devices. Finally, straightforward topological scalability using the hybrid modulation based converters is also demonstrated.

This paper demonstrates improved performance of a three-phase voltage source inverter (VSI) when digital multisampled space vector modulation is used. The modulator and the inverter controller are implemented entirely using a field-programmable gate array platform, thus achieving increased bandwidth with respect to a typical digital signal processor or microprocessor-based controller. Increased controller bandwidth results in lower output voltage harmonic distortion in the frequency range above the fundamental and below the switching frequency. Experimental validation is presented together with the analysis carried out using a state space model of a VSI with an output LC filter.

In general, the induction motor (IM) is extremely nonlinear in nature and frequency dependent. In most cases, the power generated by the IM has a low power factor (PF), which exhibits detrimental effect on the extent to which the whole transmission and distribution system functions. Since there exists more current harmonics as an outcome of minimized PF, the efficiency of the power system suffers due to transmission line heating and voltage distortion characteristics. Therefore, this paper proposes a power factor correction (PFC) method to overcome the aforementioned issues. Here, by the utilization of AC-DC bridgeless SEPIC-Cuk converter, the power quality is improved by reducing reactive power consumption and enabling better control of voltage and current outputs. To maintain the stable DC link voltage with reduced ripples, the adaptive proportional-integral (PI) controller is used in this work. The three-phase voltage source inverter (VSI) transitioning function is controlled by cascaded fuzzy logic (CFL) controller, which is also utilized for regulating the speed of the three-phase IM. Implementing the proposed control strategy improves power quality significantly by reducing total harmonic distortion (THD). The proposed system is simulated in the MATLAB platform and the attained outcomes, it is clear that the proposed system is highly effective.

Novel control approach for enhancing multi-performance of two-stage converter during power transfer from solar photo-voltaic array to AC grid