A Novel Asymmetrical 21-Level Inverter for Solar PV Energy System With Reduced Switch Count
TL;DR: In this article, a novel asymmetric 21-level multilevel inverter topology for solar PV application is presented, where the PV voltage is boosted over the DC link voltage using a three-level DC-DC boost converter interfaced in between the solar panels and the inverter.
Abstract: This article presents a novel asymmetrical 21-level multilevel inverter topology for solar PV application. The proposed topology achieves 21-level output voltage without H-bridge using asymmetric DC sources. This reduces the devices, cost and size. The PV standalone system needs a constant DC voltage magnitude from the solar panels, maximum power point tracking (MPPT) technique used for getting a stable output by using perturb and observe (P&O) algorithm. The PV voltage is boosted over the DC link voltage using a three-level DC-DC boost converter interfaced in between the solar panels and the inverter. The inverter is tested experimentally with various combinational loads and under dynamic load variations with sudden load disturbances. Total standing voltage with a cost function for the proposed MLI is calculated and compared with multiple topologies published recently and found to be cost-effective. A detailed comparison is made in terms of switches count, and sources count, gate driver boards, the number of diodes and capacitor count and component count level factor with the same and other levels of multilevel inverter and found to be the proposed topology is helpful in terms of its less TSV value, devices count, efficient and cost-effective. In both simulation and experimental results, total harmonic distortion (THD) is observed to be the same and is lower than 5% which is under IEEE standards. A hardware prototype is implemented in the laboratory and verified experimentally under dynamic load variations, whereas the simulations are done in MATLAB/Simulink.
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TL;DR: In this paper , a new single-phase asymmetrical multilevel inverter (MLI) that can generate 33 levels at the output with fewer components and lower total standing voltage (TSV) at the switches is presented.
Abstract: Multilevel inverters with a high device count, low boosting and DC voltage imbalance are all common problems exists in the traditional topologies. In this article, a new single-phase asymmetrical multilevel inverter (MLI) that can generate 33 levels at the output with fewer components and lower total standing voltage (TSV) at the switches is presented. The multiple input sources of the proposed inverter make it suited for the use in renewable energy generating systems which have a variety of DC sources. The stress distribution among the switches is investigated that reduces the use of high rated devices with which overall cost of the inverter gets reduced. The topology can be extended by adding the circuits in series for higher levels. The performance of the inverter is calculated considering a variety of critical parameters such as TSV, cost function (CF), power loss, and efficiency calculations. The MLI is tested under dynamic load conditions with sudden load disturbances with a range of combinational loads and it has been determined to be stable throughout its operation. A detailed comparison is made based on stress across the switches, stress distribution, switches count, DC sources count, gate driver circuits, component count factor, TSV, CF, and other existing topologies using graphical representations and shown to be cost-effective and superior in all aspects. The total harmonic distortion (THD) derived from simulation and experiment complies with IEEE standards. The proposed framework has been developed in MATLAB/Simulink and tested in a laboratory environment with hardware.
9 citations
TL;DR: In this paper , the authors proposed two types of FPGA-based digital switching controllers, namely selective harmonic elimination (SHE) and sinusoidal pulse width modulation (SPWM), for a 21-level multilevel inverter.
Abstract: Multilevel inverters are a type of power electronic circuit that converts direct current (DC) to alternating current (AC) for use in high-voltage and high-power applications. Many recent studies on multilevel inverters have used field-programmable gate arrays (FPGAs) as a switching controller device to overcome the limitations of microcontrollers or DSPs, such as limited sampling rate, low execution speed, and a limited number of IO pins. However, the design techniques of most existing FPGA-based switching controllers require large amounts of memory (RAM) for storage of sampled data points as well as complex controller architectures to generate the output gating pulses. Therefore, in this paper, we propose two types of FPGA-based digital switching controllers, namely selective harmonic elimination (SHE) and sinusoidal pulse width modulation (SPWM), for a 21-level multilevel inverter. Both switching controllers were designed with minimal hardware complexity and logic utilisation. The designed SHE switching controller mainly consists of a four-bit finite state machine (FSM) and a 13-bit counter, while the SPWM switching controller employs a simple iterative CORDIC algorithm with a small amount of data storage requirement, a six-bit up-down counter, and a few adders. Initially, both digital switching controllers (SHE and SPWM) were designed using the hardware description language (HDL) in Verilog codes and functionally verified using the developed testbenches. The designed digital switching controllers were then synthesised and downloaded to the Intel FPGA (DE2-115) board for real-time verification purposes. For system-level verification, both switching controllers were tested on five cascaded H-Bridge circuits for a 21-level multilevel inverter model using the HDL co-simulation method in MATLAB Simulink. From the synthesised logic gates, it was found that the designed SHE and SPWM switching controllers require only 186 and 369 logic elements (LEs), respectively, which is less than 1% of the total LEs in an FPGA (Cyclone IV E) chip. The execution speed of the SHE switching controller implemented in the FPGA (Cyclone IV E) chip was found to be a maximum of 99.97% faster when compared with the microcontroller (PIC16F877A). The THD percentage of the 21-level SHE digital switching controller (3.91%) was found to be 37% less than that of the SPWM digital switching controller (6.17%). In conclusion, the proposed simplified design architectures of SHE and SPWM digital switching controllers have been proven to not only require minimal logic resources, achieve high processing speeds, and function correctly when tested on a real-time FPGA board, but also generate the desired 21-level stepped sine-wave output voltage (±360 VPP) at a frequency of 50 Hz with low THD percentages when tested on a 21-level cascaded H-Bridge multilevel inverter model.
8 citations
TL;DR: A comprehensive overview of recently developed multilevel inverters and a solution for developing the MLIs for future research on renewable energy applications is provided in this article , where the design and functioning of each topology as well as each group are examined in this study.
8 citations
21 May 2021
TL;DR: In this article, the authors analyze the multilevel inverters (MLI) topologies into two categories which are symmetric and asymmetric configuration which contain the reduced number of switches.
Abstract: Multilevel inverters (MLIs) are extremely influential in renewable energy systems, are used to convert DC power into AC. MLIs are more beneficial in comparison to the two-level conventional inverter in terms of lower total harmonic distortion (THD), lesser electromagnetic interference (EMI), increases the capability of fault tolerance, and are more efficient. The major aspect of this review article is to analyze the recent (MLI) topologies into two categories which are symmetric and asymmetric configuration which contains the reduced number of switches $(\mathrm{N}_{\mathrm{S}\mathrm{W}})$. currently, Researchers have an eye on the using reduced number of components in MLI topologies for lesser voltage stress and high efficiency. Performance parameters such as total standing voltage (TSV), THD, and modulation techniques are briefly discussed in this article. furthermore, the general comparison of these topologies is depicted in tabular & graphical representation based on the required number of switches, number of the gate drivers $(\mathrm{N}_{\mathrm{G}\mathrm{D}})$, Number of dc voltage sources $(\mathrm{N}_{\mathrm{D}\mathrm{C}})$, THD, and the number of level $(\mathrm{N}_{\mathrm{L}})$ that are obtained through the multilevel inverter topologies.
7 citations
References
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TL;DR: In this article, the authors proposed a method of modeling and simulation of photovoltaic arrays by adjusting the curve at three points: open circuit, maximum power, and short circuit.
Abstract: This paper proposes a method of modeling and simulation of photovoltaic arrays. The main objective is to find the parameters of the nonlinear I-V equation by adjusting the curve at three points: open circuit, maximum power, and short circuit. Given these three points, which are provided by all commercial array data sheets, the method finds the best I-V equation for the single-diode photovoltaic (PV) model including the effect of the series and parallel resistances, and warranties that the maximum power of the model matches with the maximum power of the real array. With the parameters of the adjusted I-V equation, one can build a PV circuit model with any circuit simulator by using basic math blocks. The modeling method and the proposed circuit model are useful for power electronics designers who need a simple, fast, accurate, and easy-to-use modeling method for using in simulations of PV systems. In the first pages, the reader will find a tutorial on PV devices and will understand the parameters that compose the single-diode PV model. The modeling method is then introduced and presented in details. The model is validated with experimental data of commercial PV arrays.
3,811 citations
TL;DR: In this paper, the most relevant characteristics of multilevel converters, to motivate possible solutions, and to show that energy companies have to bet on these converters as a good solution compared with classic two-level converters.
Abstract: This work is devoted to review and analyze the most relevant characteristics of multilevel converters, to motivate possible solutions, and to show that we are in a decisive instant in which energy companies have to bet on these converters as a good solution compared with classic two-level converters. This article presents a brief overview of the actual applications of multilevel converters and provides an introduction of the modeling techniques and the most common modulation strategies. It also addresses the operational and technological issues.
1,847 citations
TL;DR: In this article, some of the recently proposed multilevel inverter topologies with reduced power switch count are reviewed and analyzed, both in terms of the qualitative and quantitative parameters.
Abstract: Multilevel inverters have created a new wave of interest in industry and research. While the classical topologies have proved to be a viable alternative in a wide range of high-power medium-voltage applications, there has been an active interest in the evolution of newer topologies. Reduction in overall part count as compared to the classical topologies has been an important objective in the recently introduced topologies. In this paper, some of the recently proposed multilevel inverter topologies with reduced power switch count are reviewed and analyzed. The paper will serve as an introduction and an update to these topologies, both in terms of the qualitative and quantitative parameters. Also, it takes into account the challenges which arise when an attempt is made to reduce the device count. Based on a detailed comparison of these topologies as presented in this paper, appropriate multilevel solution can be arrived at for a given application.
890 citations
TL;DR: In this paper, the authors proposed an adaptive MPPT algorithm for photovoltaic (PV) power generation systems based on a short-current pulse of the PV to determine an optimum operating current where the maximum output power can be obtained and completely differs from conventional hill-climbing-based methods.
Abstract: This paper proposes a novel maximum-power-point tracking (MPPT) method with a simple algorithm for photovoltaic (PV) power generation systems. The method is based on use of a short-current pulse of the PV to determine an optimum operating current where the maximum output power can be obtained and completely differs from conventional hill-climbing-based methods. In the proposed system, the optimum operating current is instantaneously determined simply by taking a product of the short-current pulse amplitude and a parameter k because the optimum operating current is exactly proportional to the short current under various conditions of illuminance and temperature. Also, the system offers an identification capability of k by means of fast power-versus-current curve scanning, which makes the short-current pulse-based MPPT method adaptive to disturbances such as shades partially covering the PV panels and surface contamination. The above adaptive MPPT algorithm has been introduced into a current-controlled boost chopper and a multiple power converter system composed of PV-and-chopper modules. Various operating characteristics have experimentally been examined on this multiple PV-and-chopper module system from a practical viewpoint and excellent MPPT performance has been confirmed through the tests.
642 citations
TL;DR: It is shown that versatile stand-alone photovoltaic (PV) systems still demand on at least one battery inverter with improved characteristics of robustness and efficiency, which can be achieved using multilevel topologies.
Abstract: This paper shows that versatile stand-alone photovoltaic (PV) systems still demand on at least one battery inverter with improved characteristics of robustness and efficiency, which can be achieved using multilevel topologies. A compilation of the most common topologies of multilevel converters is presented, and it shows which ones are best suitable to implement inverters for stand-alone applications in the range of a few kilowatts. As an example, a prototype of 3 kVA was implemented, and peak efficiency of 96.0% was achieved.
593 citations