A Modified Lyapunov Function Based Control Strategy for Single Phase Cascaded H-bridge Multilevel Inverter with Nonlinear Loads

The ELF (Extended Lyapunov Function) based control approach for single phase two-stage multitasking PV (photovoltaic) inverter is demonstrated in this paper. The introduced PV inverter can operate under the uncertainty of non-linear loads and PV characteristic beyond giving the closed feedback system stability analysis. The two stage PV inverter is introduced, in initial step a boost circuit is used to harnessing of crest power at PV panel side. Here time ratio of the boost circuit is planed with adaptive INC (Incremental Conductance Method). In the secondary step, the control of grid connected VSI (Voltage Source Inverter) is managed by ELF (Extended Lyapunov Function) strategy. To get best dynamic response, difference of PV feed forward to the loss component of DC bus capacitor. Other side, control of VSI and maintain stability of PV inverter, the ELF technique is reduces error in-between input and output, with there is no disturbance of equilibrium point in PV inverter. The PV inverter performance observed at changing of insolation and load variations using MATLAB /simulation. Various simulation results are presented to validate the harmonics compensation strategy.

In this paper, a novel multilevel DC-AC inverter is proposed. The proposed multilevel inverter generates seven-level AC output voltage with the appropriate gate signal design. In addition, the low pass filter is used to reduce the total harmonic distortion of the sinusoidal output voltage. The switching losses and the voltage stress across the power devices can be reduced in the proposed multilevel inverter. The operating principles of the proposed inverter and the voltage balancing method of input capacitors are discussed. Finally, a prototype multilevel inverter with an input voltage of 400 V, output voltage of 220 Vrms and output power of 2 kW is implemented. The multilevel inverter is controlled with the sinusoidal pulse-width modulation(SPWM) by TMS320LF2407 digital signal processor (DSP). The experimental results show that the maximum efficiency is 96.9% and the full load efficiency is 94.6%.

In this study, an extended Lyapunov-function-based control strategy that assures global asymptotic stability is proposed for single-phase UPS inverters. The Lyapunov function is formed from the energy stored in the inductor and capacitor due to the fact that the system states converge to the equilibrium point if the total energy is continuously dissipated. It is shown analytically that the classical Lyapunov-function-based control leads to a globally asymptotically stable system at the expense of steady-state errors in the output voltage, which exist due to the lack of outer voltage loop in the control input. Therefore, an extended Lyapunov-function-based control strategy is proposed, which eliminates the steady-state error without destroying the global stability of the closed-loop system. The steady state and dynamic performance of the proposed control strategy has been tested by simulations and experiments under resistive and diode bridge rectifier loads. The results obtained from a 1-kW inverter demonstrate that the developed control strategy not only offers global stability, but also leads to good quality sinusoidal voltage with a reasonably low THD, almost zero steady-state error in the output voltage, and fast dynamic response under linear and nonlinear loads.

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.

A novel multilevel DC-AC inverter is proposed in this paper. A seven level AC output voltage is generated using the proposed multilevel with the befitting gate signals design. The total harmonic distortion in the sinusoidal output voltage reduced using low pass filter. With the suggested multi-level inverter the switching losses and the voltage stress of power devices can be reduced. The operating principles of the proposed inverter and the voltage balancing method of input capacitors are discussed. Finally, a laboratory model of multilevel inverter with 400 V input voltage and output 220 V rms / 2kW is enforced. 16F877A PIC microcontroller is used to control the multilevel inverter with sinusoidal pulse-width modulation (SPWM).

Improvement in switching techniques is one of the effective methods for increasing the voltage quality in Multilevel Inverters. In this paper, a novel switching technique using frequency modulation is proposed to achieve high quality output voltage of multilevel inverters. This method is employed to different configurations of multilevel inverters consist of Diode Clamped (or Neutral Point Clamped), Flying Capacitor and Cascaded H-bridge. Each multilevel inverter which utilizes this technique is modeled and simulated to investigate the performance of this method by the help of MATLAB/Simulink software. The Results show that this innovative method considerably reduces total harmonic distortion (THD) of output voltage for diode clamped multilevel inverters in different kinds of loads and can solve the problem of transferring the active power in this type of inverters.

This paper presents an inverter topology based on series-voltage-action (SVA) used to generate additional levels. This inverter will be called as SVA Inverter. The SVA Inverter presents some advantages over the traditional inverters, such as output voltage higher than the dc-link voltage and lower distortion in output voltage. The complete analysis presented in this paper includes the inverter model and its operation and PWM strategy. A general comparison with conventional inverter is also presented. Simulated and experimental results corroborate the theoretical study.

Energy storage system (ESS) is generally used to manage the intermittency of the renewable energy sources (RESs). The proper control strategy is needed to effectively maintain the power balance between the RESs, load demand, and ESS. The conventional control strategy for the hybrid energy storage system (HESS) uses the high-/low-pass filter method for system net power decomposition and the ESS power dispatch. In this paper, a new joint control strategy is proposed for photovoltaic (PV) based DC grid system, with battery and supercapacitor (SC) as a HESS. The new joint control strategy utilizes the uncompensated power from the battery system to increase the performance of the overall HESS. The advantages of the proposed control strategy over the conventional control strategy are faster DC link voltage restoration and effective power sharing between the battery and the SC. The detailed stability analysis of the proposed control strategy is also presented. The effectiveness of the proposed control strategy over the conventional control strategy is validated with the short-term and long-term experimental studies.

Finite control set model predictive control (FCS-MPC) has been widely studied and applied to the power converters and motor drives. It provides the power electronics system with fast dynamic response, nonlinear system formulation, and flexible objectives and constraints integration. However, its variable switching frequency feature also induces severe concerns on the power loss, the thermal profile, and the filter design. Stemming from these concerns, this article investigates the variable switching frequency characteristics of FCS-MPC on the grid-connected inverters. An intuitive relationship between the switching frequency and the magnitude of the converter output voltage is proposed through the geometry analysis, where the switching frequency is maximized when the converter output voltage is around one-third of the DC bus voltage and decreasing when the output voltage moves away from this value. The impacts of this variable switching frequency property on the power loss and current harmonics are also analyzed. Simulation and experimental results both verify the proposed property. With this intrinsic property, FCS-MPC can autonomously achieve a less-varying temperature profile of power modules and an improved reliability compared with the conventional control strategy.

Extensive investigation of symmetrical and asymmetrical cascaded multilevel inverters for electric vehicle applications

This research compared the performance of PWM (Pulse Width Modulation) inverter and multilevel inverter in terms of their output voltage and current total harmonic distortion (THD). The inverters were designed to have the output voltage of 220 V at 50 Hz. The input voltage for both inverters are 400 VDC. For PWM inverter, the PWM technique utilized was sinusoidal PWM (SPWM) and for multilevel converter, the number of voltage level is five with diode-clamped topology. The study included circuit implementation, analysis, and THD calculation, all of which were carried out through simulation using PSpice software. In controlling the SPWM inverter output, the adjusted parameters included amplitude modulation ratio, frequency modulation ratio, and filter components’ parameters. On the other hand, the firing angles of the switching components were designated as controlling parameters in multilevel inverter. From the study, it was found that the best THD values of the designed SPWM inverter are 4.2% (voltage) and 1.7% (current), while those of multilevel inverter are 27% and 11%, for voltage and current, respectively. Thus, it can be concluded that SPWM inverter is better than 5-level inverter for the application in solar panel due to its lower THD. In our study, 5-level inverter did not satisfy the THD requirement specified in IEEE 512-1992, i.e. 5%.

In this paper, an improved Cascaded Multi-Level Inverter (CMLI) topology which can be "symmetric" or "asymmetric" is proposed. The improved topology can produce higher number of levels using lower number of components. Higher number of levels leads to generation of a high quality with low Total Harmonic Distortion (THD) output voltage waveform. To increase number of voltage levels, two algorithms are proposed for determination of magnitude of dc voltage sources, which are investigated and the most effective one is introduced. To verify operation of proposed topology, it is modeled and simulated in PSCAD/EMTDC software. Proper performance of proposed topology is confirmed by obtained simulation results.

<span lang="EN-US">Generally, PV cell converts sunlight into electricity in the form of dc. Integration of PV system with the existing grid requires dc-ac conversion. This conversion is possible with the help of a dc-ac converter known as an inverter. Among all types of the inverter, multilevel inverters (MLIs) are playing a major role with all their major privileges like High power quality, low distortion, less blocking voltages for switching devices. Conventional multilevel inverter topologies such as diode clamped, flying capacitor and cascaded MLIs are having so many disadvantages. One of the common disadvantage among all the conventional MLIs is the requirement of more number of power electronic components as the level of the output voltage increase. To reduce the power electronic components this paper proposes a multilevel inverter topology in symmetrical and asymmetrical configuration. The proposed MLI uses 12 switches and 19 diodes which are very less compared to conventional MLI topologies for generates nine and thirteen level output voltages. Comparison between presented MLI topology and conventional MLI topologies is presented in this paper. Finally, the proposed MLI whose input is fed from the PV system is integrated into the grid. The proposed concept is validated by using the MATLAB/SIMULINK software and the appropriate results are presented in this paper.</span>

This study presents the boost converter-based cascaded H-bridge (CHB) multilevel inverter with improved reliability for solar PV (photovoltaic) applications. The solar PV is associated with the boost converter to enhance DC link voltage by using the maximum power point tracking-perturb and observe (MPPT-P & O) technique. The proposed configuration is aimed toward the performance analysis of the boost converter-based CHB MLI by reducing the number of components, low total harmonic distortion (THD), reduced power, less cost function, low total standing voltage (TSV), improved reliability, and switching losses for solar PV application. In this study, a CHB multilevel inverter is used to obtain stepped pure sinusoidal AC from the solar PV array. The proposed boost converter extracts maximum power and enhances higher DC link voltage which provides high efficiency. The boost converter is integrated with a 27-level CHB multilevel inverter to generate near-sinusoidal output voltage with lower THD. The inverter is tested with linear and nonlinear loads for robustness, and during dynamic loads, inverter is stable and well suited to grid-connected applications. A detailed comparison is presented on the component count and reliability aspects with existing MLIs and 27-level MLIs. The simulation outcomes of the implemented arrangement are presented with the help of MATLAB/Simulink, an experimental prototype is developed using a dSPACE RTI1104 controller and also tested in the research laboratory for checking the possibility of the implemented arrangement.

In present days the Multi level inverter increasing popularly especial in high power and high voltage applications. The Multi level inverter having new set of features. When the level is increasing and output become nearly sinusoidal. When the sinusoidal means the output voltage having less losses the more levels of output voltage produces different methods is there the cascade H bridge is the most efficient method .In my project cascade H bridge used to producing more levels of output voltages in cascade H bridge. In this cascade H bridge two types of arrangement they are symmetrical and asymmetrical .In this cascade H bridge I find out experimentally that the asymmetrical Multi level inverter is most efficient method than the symmetrical method by using DTC technique. The DTC technique provides ripple losses and friction losses reduce. So the induction motor having the most efficient .Here we are using IGBT switching and for the controlling purpose uses the state vector modulation. The cascade out experiment show that an asymmetrical configuration provides nearly sinusoidal voltages with low distortion using less switching devices moreover torque ripples are reduced.