Modified Design and Implementation of Single Phase Seven Level Inverter with Different PWM Techniques

Abstract: The conventional two-level inverter is most commonly used for AC drive systems. The inverter produces harmonics, which will cause heating of the power electronic devices as well as load and deteriorate the life of it. Thus, anyhow harmonics should be suppressed or removed, the most common or well-known method to filter out harmonics are introduction of various filters between inverter and load according to requirements. The filters are mainly designed with L and C connection in different ways, the use of filters become more bulky and costly. To design accurate desired response filters are complex. These issues of filters for the high voltage ratings and higher power applications can be solved by multilevel (ML) inverters topology. In this paper cascaded 5-level and 7-level single phase inverter is being compared with conventional 2-level single phase inverter through proposed simulation model. MLI using cascaded H-Bridge is more advantageous than conventional 2-level such as reduced dv/dt stress improves the EMC problem. Multilevel inverters are more reliable than two-level inverters at lower speed. Voltage rating of each cell in cascaded H-Bridge inverter topology are of low values to obtain 230 AC output MLI is mostly used for stored power in batteries and fuel cell. The inverter can generate different level stepped staircase output voltages at load side to produce more sinusoidal voltage signals and to reduce the THD value. THD value of MLI using cascaded H-Bridge topology reduces on increasing number of levels. Keywords: Total harmonic distortion (THD), electromagnetic compatibility (EMC), and multilevel inverter (MLI) Cite this Article Vijay Shankar, Ankur Kumar, A.N. Tiwari. Harmonics Analysis of Single Phase VSI with 5-level and 7-level Inverter. Recent Trends in Electronics & Communication Systems. 2019; 6(1): 16–23p.

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%.

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.

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%.

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).

Multi-level inverter used in applications that require high power. The important factor in multi-level inverter is Total Harmonic Distortion (THD). This study discuss nine level cascaded H-bridge multilevel inverter. Also, proposed the effects of using filter on waveform and Total Harmonic Distortion (THD) of output voltage and current. Discussed LC low pass filter and sinusoidal pulse width modulation as control technique of switches. Comparison THD of nine level cascaded H-bridge multilevel inverter with and without filter. The proposed level and filter are design and simulate by MATLAB 2010 Version 7.11.0. The simulation results show the effects of using filter on THD and waveform of output voltage and current. Different methods for choosing filter value are used to illustrate the filter effect.

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.

Multilevel inverter units for stand-alone solar photovoltaic systems are gaining popularity in the present industrial environment. The number of switching devices, total harmonic distortion, number of output levels and number of sources are the governing factors in a multilevel inverter topology. The classical multilevel inverter topologies produce a considerable amount of switching losses due to handful number of switching devices as the number of output levels is increased. Therefore to overcome these drawbacks a multilevel inverter topology to maximize the number of output levels with reduced number of switching devices is opted. The staircase output voltages representing the total number of levels are obtained by the additive and subtractive combination of asymmetrically arranged voltage sources thereby reducing the total number of DC sources required. The reduction of THD and switching losses is done by selecting the suitable PWM technique with low switching frequency. Unlike in the central MPPT architecture, the distributed MPPT architecture is employed for the extraction of maximum power. A multilevel inverter for stand-alone solar PV system incorporating the features like reduced number of switches, reduced number of sources and maximizing the number of output levels with distributed MPPT architecture is designed. By this a better performance compared to the conventional methodology can be attain. The multilevel voltage source inverter with/without distributed MPPT and comparative analysis of the three types of Multicarrier Sinusoidal PWM techniques at low/high carrier wave frequency is modeled and simulation results have been taken. The simulation of the Multilevel VSI for stand-alone solar PV system is done using MATLAB R2014a software.

Multilevel converters in FACTS and distributed generation system are very promising area for academic researchers and industry interest. Here two different modulation schemes of 3-level Neutral point clamped inverter are proposed and presented. The inherent neutral point potential unbalance issues and balancing methods for LS-PWM and SVM techniques are analyzed in detail. Total Harmonic Distortion in output voltage and current is used as the performance indicator for the inverter. It can be concluded that LS-PWM has higher harmonic distortions and high losses when compared to SVM. SVM technique also is excellent in DC bus voltage balancing. The experimental results for a 1.5kW prototype validate the simulation and theoretical results.

A Multi Level Inverter (MLI) has numerous industrial applications over a conventional two-level inverter due to its attractive features like it produces staircase output waveform with very lower distortion, it has less dv/dt stresses on switches, it operates effectively in both symmetric and asymmetric states, it performs at lower switching frequency and hence lower switching loss, etc. But, unfortunately, it needs greater number of power semiconductor switches and associated gate drive circuits. So, it may cause the overall system to be more complex and expensive. This paper presents a new topology of MLI with reduced number of semi conductor switches typically called as generalized cascaded MLI (with constant DC voltage sources). It can be analysed in both symmetric and asymmetric states by considering different criteria for optimal structures such as minimum number of DC sources, gate driver circuits, power electronic switches, minimum standing voltage on switches etc. In this work, DC source is realized using Photo Voltaic (PV) systems. The most well-known Perturb and Observe (P&O) algorithm is used for PV systems to achieve Maximum Power Point (MPP). The efficacy of aforementioned method is verified through Total Harmonic Distortion by taking R and RL loads. The simulation has been accomplished in MATLAB.

Introduction. The advantages of a high-power quality waveform and a high voltage capability of multilevel inverters have made them increasingly popular in recent years. These inverters reduce harmonic distortion and improve the voltage output. Realistically speaking, as the number of voltage levels increases, so does the quality of the multilevel output-voltage waveform. When it comes to industrial power converters, these inverters are by far the most critical. Novelty. Multilevel cascade inverters can be used to convert multiple direct current sources into one direct current. These inverters have been getting a lot of attention recently for high-power applications. A cascade H-bridge multilevel inverter controller is proposed in this paper. A change in the pulse width of selective pulse width modulation modulates the output of the multilevel cascade inverter. Purpose. The total harmonic distortion can be reduced by using filters on controllers like PI and fuzzy logic controllers. Methods. The proposed topology is implemented with MATLAB/Simulink, using gating pulses and pulse width modulation methodology and fuzzy logic controllers. Moreover, the proposed model also has been validated and compared to the hardware system. Results. Total harmonic distortion, number of power switches, output voltage and number of DC sources are analyzed with conventional topologies. Practical value. The proposed topology has been very supportive for implementing photovoltaic based multilevel inverter, which is connected to large demand in grid and industry.

Recently, great attention has been addressed for multilevel inverters, as they exhibit low total harmonic distortion (THD) in the output voltage and low electromagnetic interference (EMI). This paper proposes a single-phase five-level pulse width modulation (PWM) inverter for grid connection. The proposed PWM technique has some switches operated at fundamental line frequency and the others operate at inverter switching frequency. The proposed inverter has advantages of less number of components and low THD compared with the conventional multilevel inverter. The inverter operational principles and the switching functions are analyzed in this paper. Moreover, a proportional integral (PI) current control algorithm is designed and implemented in DSPACE DS1103 to keep the current injected into the grid sinusoidal and in-phase with the grid voltage for unity power factor. Simulation and experimental results prove the powerful merits of the proposed multi-level inverter and the capabilities of the proposed PWM technique.

Converters are used in the utility interface of renewable energy system to reduce harmonic contents in line current/voltage and to increase reliability. These converters suffer from high level of Total Harmonic Distortion (THD) in the utility line currents/voltages which creates a lot of problems in the power system. In this paper selective harmonics are eliminated to reduce the THD, that is, the problem is to determine optimal switching angles for eliminate harmonics while maintaining the required fundamental currents/ voltages. The THD reduction is achieved by the help of multilevel inverter with equal separate dc sources using particle swarm optimization technique. This technique can be applied to multilevel inverters with any number of levels; as an example in this paper, an 11-level inverter is considered. Theoretical results are verified by experiments and simulations for an 11- level H-bridge inverter. Results show that the proposed method does effectively eliminate a great number of specific harmonics, and the output voltage is resulted in low total harmonic distortion.

The Doubly Fed Induction Motor (DFIM) is essential in Wind Energy Conversion Systems (WECS) for efficient wind energy harvesting. Conventional power converters in WECS often result in high Total Harmonic Distortion (THD) in output voltage and current, affecting wind energy economy. This research proposes replacing conventional converters with Modular Multi-level Converters (MMC) due to their scalable topology, low harmonic distortion, high efficiency, and the elimination of DC link capacitors. The MMC is connected in a back-to-back configuration between the rotor of the DFIM and the grid to enable four-quadrant operation. Circulating current in the MMC is minimized using a Modified Deer Hunting Optimization (MDHO) based Fractional Order PID (FOPID) controller and a Mexican Axolotl Optimization (MAO) based FOPID. Capacitor voltage balancing is achieved using Level-Shifting PWM (LSPWM) and Three-Dimensional Space Vector PWM (3D-SVPWM) techniques with voltage sorting algorithms. The impact of these control and modulation techniques on the DFIM is analyzed in terms of reduced THD, and steady state and transient performance. Simulations are conducted in MATLAB/R2022a, and experimental validation is performed using a 7-level 0.5 kW MMC in a Hardware-In-Loop (HIL) setup.

Study on Carrier Overlapping PWM Technique for Nine Level Inverter