Cascaded Multilevel Inverter Research Articles

Design of New Asymmetrical Cascaded Multilevel Inverter with Reduced Number of Switches

Design of New Asymmetrical Cascaded Multilevel Inverter with Reduced Number of Switches

A Home-type (H-type) Cascaded Multilevel Inverter with Reduced Device Count: Analysis and Implementation

Multilevel inverter (MLI) is increasingly recognized as a low distorted wave synthesizing power converter built using recent power semiconductor devices. However, MLIs suffer from the requirement of higher device count. In this paper, a 15-level Home-type (H-type) inverter topology is proposed to address this concern. The H-type inverter topology is cascaded to synthesize a higher number of levels in output voltage. Voltage ratings of the dc sources are designed to generate a large number of uniform steps in output voltage. Analysis of the proposed method is presented for required number of switches, dc voltage sources, driver circuits and blocking voltage of switches. Comparative study demonstrates that the suggested topology requires reduced device count compared to the similar topologies reported in the literature. Simulation and experimental studies have been carried out to validate the performance of proposed MLI topology.

Design and Implementation of 15-Level Multilevel Cascaded Type Inverter with Reduced Switching Count

In high and medium AC power applications, multilevel inverters (MLI) have significant importance in modern days. The architecture of multi-level cascaded type inverter is preferred because of reduced harmonic distortion, high quality AC output power, least switching loss and minimum switching stress. The existing method uses 8-number of switches to generate 11-level AC voltage. A new design of 15-level multilevel inverter with 6-switching devices is proposed in this paper and DC supply devices are similar to existing method, which outcomes in less switching loss, less complexity of circuit design and less cost. The DC supply for multilevel inverter is taken from solar panel with MPPT technique. The new 6-switch multilevel inverter circuit topology, switching pattern and gate pulse making is explained in this paper. The fast Fourier transform (FFT) analysis of the outputs of 11-level and 15-level of multilevel inverters are related. The new 6-switch 15 level cascaded type inverter circuit has been intended and modeled by using MATLAB software Simulink tool. The simulation outcomes are displayed with less total harmonic distortion and reduced switching loss has been achieved.

Design of a Single Phase H- Bridge Cascaded Multi Level Inverter (9 Level) for Solar Powered Utilities

Nine level inverter and converter which is used for solar powered utilities was proposed. The inverter has 7 switches in main circuit and 1 switch for high frequency switching for the generation of nine level output. The output in the inverter reduces overall THD, loss due to switching and improves the efficiency of the power in the output. In this paper the control circuit is simplified by using capacitors to balance the voltage automatically. Using MATLAB/Simulink simulation results are explained in detail.

Harmonic Reduction in Hybrid Cascaded Multilevel Inverter Using Modified Grey Wolf Optimization

This article proposes a modified grey wolf optimization (MGWO) which has improved rate of convergence and avoids local optima stagnation. This is achieved by improving the exploration-exploitation balance in conventional grey wolf optimization (GWO). Moreover, the use of weighted-distance strategy allows quick identification of the global optima in the proposed MGWO. This optimization is then applied for the control of a three-phase, 11-level hybrid cascaded multilevel inverter (HC-MLI). Selective harmonic elimination pulsewidth modulation technique is implemented through MGWO which generates optimal switching angles for the HC-MLI so as to eliminate lower order harmonics such as 5th, 7th, 11th, and 13th from the output voltage. In MGWO optimized HC-MLI, balancing of capacitor voltage is made possible at higher modulation index by making use of the available redundant switching states. The performance of the proposed work is validated through simulation and experimentation on a 1.5 kW prototype. The results obtained through simulation show that the MGWO algorithm is more efficient and accurate than other reported algorithms such as GWO, genetic algorithm, and particle swarm optimization in terms of performance, harmonic reduction, and convergence rate.

Fault-Tolerant Control of CPS-PWM-Based Cascaded Multilevel Inverter With Faulty Units

Bypassing the faulty power unit(s) of the regenerative cascaded multilevel inverter (CMI) directly results in a series of adverse influences. The existing solutions are not easy to implement and only effective for the Y-connected devices composed of regenerative CMIs. To bypass the faulty power units seamlessly, the corresponding control strategies must guarantee: 1) constant equivalent switching frequency; 2) constant sampling frequency; and 3) constant fundamental voltage amplitude. To this end, a generic fault-tolerant control strategy, which adjusts the carrier frequency and simultaneously changes the CMI dc voltage and/or the modulation ratio, is presented in this paper. It is applicable for the device composed of carrier phase-shifting pulsewidth modulation (CPS-PWM)-based CMIs to ride through faults seamlessly, whether it is a single-phase system, a three-phase system (being it $\Delta $ -connected or Y-connected), or a multiphase system. The detailed implementation is also analyzed by modeling the output voltage of the CPS-PWM-based CMI. The experimental results verify the validity and superiority of the proposed fault-tolerant strategy for the CPS-PWM-based CMI system with faulty power units.

A Single Source Cascaded Multilevel Inverter

A Single Source Cascaded Multilevel Inverter

A 40-Pulse Multiphase Staggering Modular Transformer With Power Quality Improvement in Multilevel Inverter Fed Medium-Voltage Induction Motor Drives

In this article, a new configuration of the adjustable speed drive is proposed for the medium-voltage industrial induction motor drives (IMDs). Here, a new configuration of a 40-pulse multiphase staggering modular transformer is proposed for power quality improvement in the vector-controlled induction motor drive (VCIMD) at the utility end. In it the two transformers (T1 and T2) are utilized and both have extended-delta configured input windings with +9° and −9° phase shift and their secondaries have two sets of five-phase ac supplies to achieve a 20-pulse ac–dc conversion. Because of these primary angles, these two transformers are reconfigured as a 40-pulse ac–dc converter. A new cascaded multilevel inverter (C-MLI) is proposed at the drive end. This C-MLI is cascading four two-level voltage source inverters in a unique manner to get nine levels in its line voltage. A modified sinusoidal pulsewidth modulation strategy is utilized, which offers very low switching frequency, low switching losses, enhanced fundamental magnitude, and low total harmonic distortion. The performance of the proposed VCIMD, is evaluated by simulating it in MATLAB Simulink. The performance of the proposed VCIMD is also verified using a scaled down laboratory prototype under various operating conditions such as steady state, starting, load perturbation, speed control, varying load conditions, and over a wide speed range of IMD.

Hybrid Asymmetric Cascaded Multilevel Inverters Based on Three- and Nine-Level H-Bridges

This paper proposes two hybrid asymmetric cascaded multilevel inverters for driving medium-voltage open-end winding motors. Each phase of the proposed systems consist of a three-level (3L) H-bridge cell and a nine-level (9L) H-bridge cell connected in series. An unequal dc-voltage ratio of 1:8 between cells is used, providing 19 phase voltage levels. The topologies of the 9L H-bridge cell are based on modular multilevel cascade converter (MMCC) with double-star chopper cells, while the 3L H-bridge cell is fed by a floating capacitor. Compared to conventional MMCC for open-end stator winding motor drives, the proposed inverters can produce more phase voltage levels. In addition, they require a smaller number of power semiconductor switches, drivers and capacitors. Simulations and experimental results are presented in order to demonstrate the performance and feasibility of the proposed topologies.

Reduced Switch Cascaded Multilevel Inverter With New Selective Harmonic Elimination Control for Standalone Renewable Energy System

Recently multilevel inverters (MLIs) have received wide attention from industry and academia, as they are changing into a viable technology for diverse applications. To produce high-quality output using less switch count, development of novel reduced switch MLI (RS MLI) topologies has been a focus of current research theme. This paper presents design and control of a switched-diode dual source single switch MLI (SDDS MLI). The generalized SDDS MLI is first designed using an asymmetric basic unit. Proposed SDDS MLI requires less switch count and driver circuit count compared with the few recently developed RS MLI topologies. To improve the voltage quality by eliminating targeted low-order harmonics, a modified version of fish swarm optimization algorithm is examined for computing optimum switching angles required to control the SDDS MLI. Moreover, suitability and superiority of the derived algorithm are established by comparing with traditional selective harmonic elimination techniques. The developed topology is investigated through several MATLAB simulations as well as experimental tests in the laboratory applying the modified control approach.

Model predictive current control based on a generalised adjacent voltage vectors approach for multilevel inverters

Model predictive current control (MPCC) uses the discrete-time model of a system to predict the future behaviour of the current for all voltage vectors (VVs) generated by a power converter. In multilevel inverters, the large number of VVs imposes a long computation time for the prediction and selection of the optimal state to be applied to the converter, which increases the sampling time and decreases the closed-loop performance. An MPCC is proposed based on the idea of generalised adjacent voltage vectors (GAVVs) for multilevel cascaded H-bridge inverters with a DC-link voltage fed by photovoltaic (PV) cells. This method deals with the voltage drop and often small inter-bridge voltage imbalance and irradiance issues that occur in PV power plants. The proposed GAVV method is analytically formulated to provide three types of subsets for a given number of inverter levels. The use of the newly added subsets of four and five VVs contributes to boosting the converter output voltage and achieving acceptably balanced current and line-to-line voltage under low irradiance compared with the classical approach. Simulation and experimental results show good current response and reduced switching frequency even under a high current reference with DC-link voltage drop.

Improved hyper-spherical search algorithm for voltage total harmonic distortion minimization in 27-level inverter

Multi-level inverters (MLIs) have become popular in different applications such as industrial power control systems and distributed generations. There are different forms of MLIs. The cascaded MLIs (CMLIs) have some special advantages among them such as more different output voltage levels using the same number of components and higher power quality. In this paper, a 27-level inverter switching algorithm considering total harmonic distortion (THD) minimization is investigated. Switching angles of the inverter switches are achieved by minimizing a THD-based objective function . In order to minimize the THD-based objective function, the hyper-spherical search (HSS) algorithm, as a novel optimization algorithm, is improved and the results of improved HSS (IHSS) are compared with HSS algorithm and other five evolutionary algorithms to show the advantages of IHSS algorithm.

DC Decoupling-Based Three-Phase Three-Level Transformerless PV Inverter Topology for Minimization of Leakage Current

This letter presents a three-phase three-level cascaded photovoltaic (PV) inverter configuration based on the dc decoupling strategy. The given configuration requires two additional decoupling switches for the minimization of the leakage current. The leakage current is minimized by avoiding or restricting the change in terminal voltages, during the common zero state. Further, a common zero state in all the three phases is obtained using a phase opposition disposition pulsewidth modulation technique. Once the common zero state is realized, the dc decoupling switches are used to isolate the PV source and output load. Apart from the terminal voltage, the proposed configuration also reduces the transitions in the common-mode voltage. Further, this letter also presents an analysis of the terminal voltage using the switching function concept. From the given switching function analysis, an analytical expression of the terminal voltage is derived and is used to obtain the analytical waveform, which matches with the simulation results. In addition to the terminal voltage, the leakage current waveform is also given. Fast Fourier transform spectrums of both are shown. These results are further supported by the experimental waveforms which match both simulation and analytical waveforms. Further, the proposed cascaded multilevel inverter (CMLI) is also compared with the conventional CMLI.

A modified cascaded h-bridge multilevel inverter based on particle swarm optimisation (PSO) technique

<span>In this paper, modified multilevel inverter, via addition of an auxiliary bidirectional switch, based on Newton Raphson (NR) and Particle Swarm Optimization (PSO) techniques is presented. The NR and PSO techniques were employed for selective harmonics elimination (SHE) solution in a modified Cascaded H Bridge Multilevel inverter (CHB-MLI). The Selective Harmonic Elimination Pulse-Width Modulation (SHE-PWM) is a powerful technique for harmonic minimization in multilevel inverter. The NR and PSO techniques were used to determine the switching angles by solving the non-linear equations of the output voltage waveform of the modified CHB-MLI in order to control the fundamental component and eliminate some low order harmonics. The proposed NR and PSO techniques are capable to minimize the Total Harmonic Distortion (THD) of the output voltage of the modified inverter within allowable limits. This paper aims to modeling and simulation by MATLAB of the modified topology of the CHB-MLI for a single-phase prototype for 13-levels. The inverter offers less THD and greater efficiency using PSO control algorithm compared with the NR algorithm. <br https://server9.kproxy.com/servlet/redirect.srv/sruj/snbzofspy/skvyzff/p1/> The performance of the proposed controllers based on NR and PSO techniques is verified through simulation.</span>

Diminution of Harmonics in a Cascaded Multilevel Inverter using Third Harmonics Injection PWM Technique

This paper is deals the Asymmetric cascaded three phase hybrid multilevel inverter for ac motor application. This proposed hybrid three phase inverter is used to diminishes the no of semiconductor device requirement and enhances the power distribution of each H-bridge cell. The Third Harmonics Injection (THIPWM) with sinusoidal pulse width modulation (SPWM) are used to regulate the output voltage of the inverter, further incorporate the Phase disposition (PD) and Alternative Phase Opposition disposition PWM (APOD) techniques. This control technique is applied to minimize the current harmonic and get the better recital of the system. The circuit is simulated using Mat-lab Simu-link. The circuit performance such as THD, line voltage and phase voltage are compared using two hybrid modulation techniques and verified with simulation results.

Execution of Artificial Neural Networks Based Controller for the Finalized Loop Control for Decrease in the Switching Losses

The main disadvantages of the cascade multilevel inverters is actually a necessity of a segregated dc current sources for each and every H-bridge, due to this main reason size of the inverter and also boost, through which reliability of the body decreases. This Downside of inverter is actually the crucial inspiration for the here and now work.In this newspaper Plunged Multilevel inverter for photo-voltaic creating device appears with minimized dc source to show the benefits of cascade the PV unit. Microinverters are really low power DC-AC converters that are attached to each image electric PV door of a renewable energy unit which are largely based upon flyback converter geography. In this particular paper, a distinct solitary stage zeta microinverter is really recommended. Higher voltage gain is in fact secured due to the modified inverter as well as hence bring in the low power inverter suited for the application of PV requests.

Fuzzy logic based open-circuit fault diagnosis in IGBT for CMLI fed PMSM drive

For the objective of enhancing the reliability in power electronics, a fault diagnosis technique has been reported for a three-phase cascaded multilevel inverter (CMLI). This paper presents a fuzzy based fault diagnosis technique based on the average current Parks vector technique for the three-phase CMLI fed permanent-magnet synchronous motor (PMSM) drive. The three-phase normalized currents divided into positive (Eq+) and negative groups (Eq−). Then the average current Park's vector technique is used to measure the fault symptom variables by using the phase current information. The proposed fault diagnosis technique can detect and locate the single or multiple open-circuit faults, and also the intermittent faults in IGBT's at any condition (ex., change in mechanical speed, change in load torque and change in system parameters), which can improve the reliability of the motor drive system. The effectiveness of the proposed method is validated by the simulation and experimental results.

A Novel Architecture of Boost Dc-Link Cascaded Multilevel Inverter for Harmonic Mitigation

Present years have seen the repeated use of the Multi Level Inverters (MLI) with the Photo voltaic (PV) panel in addition more than a few research works have as well been performed in this field. In the past two eras, decreasing the amount of electronic components such as switches, dc sources in MLI are the most important research works. This proposed method principally concentrates on implementing an effective topology with decreased amount of electronic elements for MLI. Reduction in switch count creates the system cost effective. A seven level inverter (+3Vdc, -3Vdc, +2Vdc,-2Vdc and +Vdc, -Vdc and 0) with a single dc source as well as reduced loss in switching power was designed. With the help of multicarrier sinusoidal pulse-width modulation (MCSPWM) method, DC-link switching is attained. It brings about enhanced quality of attained output AC power. Simulation model of a seven-level BDCLCMLI system is designed and to examine its performance for several modulation condition

Harmonic Minimization in Three-Phase Hybrid Cascaded Multilevel Inverter Using Modified Particle Swarm Optimization

This paper proposes a modified particle swarm optimization (MPSO) for fast convergence and harmonic minimization in three-phase eleven-level hybrid cascaded multilevel inverter (HC-MLI). Selective harmonic elimination pulsewidth modulation (SHE-PWM) technique implemented through MPSO has been used in the proposed work for synthesizing an eleven-level output voltage using two dc sources, a precharged capacitor, and twelve switches. The switching angles of the three-phase eleven-level HC-MLI has been computed for eliminating specified lower order odd harmonics such as 5th, 7th, 11th, and 13th from the output voltage of the HC-MLI. In the proposed MPSO optimized HC-MLI, capacitor voltage balance is also ensured even at higher modulation indices by utilizing the redundant switching states available at different switching instances of the HC-MLI. The performance of the MPSO optimized three-phase eleven-level HC-MLI has been verified through simulation and experimentation on a 1.5-kW prototype using closed-loop control. The results obtained through MPSO are compared with the results obtained through genetic algorithm (GA) and particle swarm optimization (PSO) in terms of convergence rate and harmonic content. It has been found that MPSO gives improved results in comparison to GA and PSO.

Floquet-Theory-Based Small-Signal Stability Analysis of Single-Phase Asymmetric Multilevel Inverters With SRF Voltage Control

This paper proposes a small-signal model and Floquet-theory-based method for analyzing small-signal stability of a single-phase asymmetric cascaded H-bridge multilevel inverter (ACHMI) operating in the stand-alone mode. The studied ACHMI system consists of the power stage and cascaded control loops, which includes the voltage loop in the synchronous reference frame (SRF), capacitor current feedback control, and hybrid modulation scheme. Due to the SRF voltage control, the derived small-signal model under linear and nonlinear load conditions are inherently periodically time-variant. Therefore, the Floquet theory is employed to analyze the stability regions of the dual-loop control parameters of the ACHMI. Furthermore, the loci and moduli of Floquet multipliers are calculated to accurately evaluate the respective effects of control parameters on the stability of the system. With the stability analysis based on the small-signal model and Floquet-theory-based method, an effective selection range of control parameters of the multilevel inverter can be obtained. Finally, the experimental results from a reduced-scale laboratory prototype ACHMI are presented to validate the theoretical analysis, and the effectiveness of proposed analysis method in high-power applications is verified by the simulation results from a 10-kV medium-voltage ACHMI.