PWM sensor-less balancing technique for the three-phase seven level PUC-NPC converter

Researchers in the field of multilevel inverters (MLI) have recently been focused on decreasing the number of power switches while maintaining a higher-level AC (Alternating current) output voltage waveform with a very lower total harmonic distortion (THD) value. To generate a nine-level output waveform, this article introduces the new topology of an asymmetrical cascaded auxiliary module multilevel inverter (ACAM-MLI). Twelve switches and four DC sources are needed by a traditional cascaded H-Bridge inverter to provide the same output voltage but the proposed inverter requires eight switched and a single DC source. The nearest level control (NLC)-PWM is applied to the proposed topology, and the results are compared to those obtained using a conventional seven-level full bridge cascaded multilevel inverter. To test the performance of the ACAM-MLI, inverter implemented on MATLAB 2023a and results presented at different load conditions.

The paper presents a new transformer‐less step‐up multilevel inverter structure with a single DC source. The concept was based on cascaded connection of bipolar T‐type 5‐level modules. Proper charging and discharging of capacitors across the load in prearranged time durations would make a nearly sinusoidal staircase voltage. The output voltage amplitude was several times greater than the DC input depending on the number of modules and charging mode of the capacitors. Multiplying the input voltage, self‐balancing, generating bipolar voltage waveform, easy circuit expansion and considerably low THD (Total Harmonic Distortion) were found to be the advantages of the proposed topology. The paper also adds operating principle, simulation and experimental results of a 29‐level prototype based on the presented inverter structure.

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.

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 article proposes a single dc source-based hybrid three-phase thirteen-level inverter suitable for medium voltage applications. The multilevel structure is composed of a three-level T-type neutral point clamped (NPC), half-bridge, and three-level Flying capacitor converter with optimal switch count and high dc bus voltage utilization as high as 0.63 times the dc-link voltage. This requires a special attention to a novel capacitor balancing method using redundant switching states in order to operate at any power factor under grid-connected mode. A unified common-mode voltage is injected in the carrier based pulse width modulation (PWM) technique to maintain the voltage balance in dc-link capacitors as well as floating capacitors. Simulation results are presented under different operating conditions that include unity power factor operation with passive load as well as grid-connected inverter mode. The performance of the proposed multilevel inverter in the grid-connected mode is also validated with experimental results using a lab prototype.

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.

A modified T-type multilevel inverter for renewable energy applications

A novel three-phase multilevel inverter using a single dc source is proposed in this paper, which uses flying capacitors for generating different voltage levels. Pole voltage levels can be of five levels or higher than that. The structural similarity of the front end of the proposed inverter with that of the three-level neutral-point clamped inverter and the presence of redundant switching states helps in the voltage balancing of flying capacitors as well as dc bus capacitors. This inverter topology has advantages over traditional multilevel topologies in terms of the number of devices, fault-tolerant operation and performance under variable modulation index and load conditions. Simulation results are presented to illustrate the performance of a five-level proposed inverter fed induction motor drive. However, this topology can be extended further for higher levels by cascading multiple H-bridge circuits.

RETRACTED: Nonlinear Transformational Optimization (NTO) technique based Total Harmonics Distortion (THD) reduction of line to line voltage for multi-level inverters

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%.

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.

A new three phase multilevel inverter with reduced number of components count is proposed in this paper. This inverter is designed using a single DC source per phase to generate multiple level output voltage which makes it suitable for low and medium voltage applications, including ac-coupled renewables or energy storages. A generalized circuit configuration is shown in this paper following which the number of output voltage level can be increased as per expectation. Although, each element endures the voltage stress equivalent to the input DC voltage, the value of total standing voltage (TSV) is reduced by the utilization of minimized number of components with respect to the number of series connected capacitors. Further, staircase modulation scheme is used to generate the switching signals. Hence, the proposed inverter can be operated at low switching frequency with optimal output current harmonic distortion which decreases switching losses and suppresses power factor falling. In order to validate the theoretical explanations and practical performances of the proposed inverter, the hypothesis is simulated for 9, 13 and 39 output voltage level inverters for three phase with a line voltage total harmonic distortion (THD) of 6.06%, 4.16% and 2.10% respectively in MATLAB/Simulink and a 5-level single phase laboratory prototype is implemented in the laboratory.

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.

This paper presented the design and development of a multilevel inverter (MLI). The demand for better electronic devices increases rapidly. The multilevel inverter (MLI) which convert direct current (DC) to alternating current (AC) are widely used in the industry. The objective of this research is to design and simulate the 3-level and 3-level NPC MLI module using PLECS software. To develop the switching technique for each level of NPC MLI, and To analyse and validate the MLI in terms of harmonic. Although there is already an inverter in the market, the researcher still pursues to improve the efficiency, total harmonic distortion (THD), and reduce the size of the MLI. An THD can be improved using the suitable modulation technique and the size of the MLI can be reduced by designing better topologies. The modular NPC is using the three-level NPC as the main module and the number of levels can be increased by adding 2 level NPC modules to the main module. The switching technique was created to control the NPC MLI for each level.