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17 pages, 9161 KiB

Open AccessArticle

Power Quality Enhancement in a Grid-Integrated Photovoltaic System Using Hybrid Techniques

by Prasad Kumar Bandahalli Mallappa, Herminio Martinez Garcia and Guillermo Velasco Quesada

Appl. Sci. 2021, 11(21), 10120; https://doi.org/10.3390/app112110120 - 28 Oct 2021

Cited by 1 | Viewed by 1630

In recent years, the photovoltaic (PV) system was designed to supply solar power through photovoltaic arrays. The PV generator exhibits nonlinear voltage–current characteristics and its maximum power point tracking (MPPT), which varies with temperature and radiation. In the event of non-uniform solar insolation, [...] Read more.

In recent years, the photovoltaic (PV) system was designed to supply solar power through photovoltaic arrays. The PV generator exhibits nonlinear voltage–current characteristics and its maximum power point tracking (MPPT), which varies with temperature and radiation. In the event of non-uniform solar insolation, several multiple maximum power points (MPPs) appear in the power–voltage characteristic of the PV module. Thus, a hybrid combination of binary particle swarm optimization (BPSO) and grey wolf optimization (GWO) is proposed herein to handle multiple MPPs. This combination is nowhere found in the literature, so the author chose this hybrid technique; and the main advantage of the proposed method is its ability to predict the global MPP (GMPP) in a very short time and to maintain accurate performance, even under different environmental conditions. Moreover, a 31-level multilevel inverter (MLI) was designed with a lower blocking voltage process to reduce the complexity of the circuit design. The entire system was executed in the MATLAB platform to examine the performance of the PV system, which was shown to extract a maximum power of 92.930 kW. The simulation design clearly showed that the proposed method with a 31-level MLI achieved better results in terms of total harmonic distortion (THD) at 1.60%, which is less when compared to the existing genetic algorithm (GA) and artificial neural networks (ANNs). Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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24 pages, 6784 KiB

Open AccessArticle

A Transformer-Less Multiconverter Having Output Voltage and Frequency Regulation Characteristics, Employed with Simple Switching Algorithms

by Naveed Ashraf, Ghulam Abbas, Irfan Khan, Ali Raza and Nasim Ullah

Appl. Sci. 2021, 11(7), 3075; https://doi.org/10.3390/app11073075 - 30 Mar 2021

Cited by 4 | Viewed by 1721

Abstract

The attractive features of the direct AC-AC converters increase their use in many applications such as voltage control for a heavy-duty load that has a high time constant, AC machine drives, and heating systems based on the induction process. These converters process power [...] Read more.

The attractive features of the direct AC-AC converters increase their use in many applications such as voltage control for a heavy-duty load that has a high time constant, AC machine drives, and heating systems based on the induction process. These converters process power in single-stage having simple circuit topologies with reduced switching devices and circuit components. These characteristics lead to the efficient power conversion process. The use of a low-frequency input transformer with multiple output tapping for the regulation of output voltage and frequency is one of the major sources of cost, size, and conversion losses. The complication in the switching algorithms is also the main concern in these converters. The preceding deficiencies lower their potency to be used in daily life. The costly controllers or processors are to be employed to realize the complex control techniques or algorithms. That increases the overall cost and circuit complication. This paper introduces the simple control techniques employed to a novel transformer less multi converter to have the various ac outputs for voltage and frequency regulation. The validation of power circuit and control schemes is tested through the simulation and practical results obtained in Simulink and practical setup respectively. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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16 pages, 3198 KiB

Open AccessArticle

Fault Current and Voltage Estimation for Pole-to-Pole Faults in Modular Multilevel Converter Based DC Grids Considering AC Active Power

by Hui Cai, Junli Zhang, Jingqiu Yu and Zheren Zhang

Appl. Sci. 2021, 11(6), 2882; https://doi.org/10.3390/app11062882 - 23 Mar 2021

Cited by 1 | Viewed by 1664

Abstract

DC short-circuit faults are one of the challenges for modular multilevel converter (MMC) based DC grid. It is vital for proper design of protection system to estimate the fault currents and voltages. The existing calculation methods based on RLC equivalent model of MMC [...] Read more.

DC short-circuit faults are one of the challenges for modular multilevel converter (MMC) based DC grid. It is vital for proper design of protection system to estimate the fault currents and voltages. The existing calculation methods based on RLC equivalent model of MMC have enough accuracy in estimating the branch currents but suffer from poor accuracy in estimating the node voltages. To better reflect the dynamics of MMC control during the fault, MMC is equivalent to a RLC series circuit in parallel with a variable controlled current source. This model not only considers the discharge of sub-module capacitors but also the AC active power and MMC control. Then, based on the discrete adjoint model of the equivalent MMC model and the RL series equivalent model of DC lines, the fault voltages and currents for the pre-fault and faulted DC grids could be easily obtained. From the aspect of power balance, the importance of AC active power on estimating the fault currents and voltages is discussed then. At last, based on the Zhangbei bipolar DC grid, comparisons are conducted between the simulations on PSCAD, the numerical calculation under the proposed method and the existing methods. The results show that the proposed method and the existing methods are both able to accurately estimate the fault currents within a relative error of 1%. However, compared with the error of the existing methods in calculating the fault voltages, the relative error for the proposed method is limited to less than 5% for the whole DC gird. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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18 pages, 390 KiB

Open AccessArticle

Efficient Operative Cost Reduction in Distribution Grids Considering the Optimal Placement and Sizing of D-STATCOMs Using a Discrete-Continuous VSA

by Oscar Danilo Montoya, Walter Gil-González and Jesus C. Hernández

Appl. Sci. 2021, 11(5), 2175; https://doi.org/10.3390/app11052175 - 02 Mar 2021

Cited by 31 | Viewed by 2264

Abstract

The problem of reactive power compensation in electric distribution networks is addressed in this research paper from the point of view of the combinatorial optimization using a new discrete-continuous version of the vortex search algorithm (DCVSA). To explore and exploit the solution space, [...] Read more.

The problem of reactive power compensation in electric distribution networks is addressed in this research paper from the point of view of the combinatorial optimization using a new discrete-continuous version of the vortex search algorithm (DCVSA). To explore and exploit the solution space, a discrete-continuous codification of the solution vector is proposed, where the discrete part determines the nodes where the distribution static compensator (D-STATCOM) will be installed, and the continuous part of the codification determines the optimal sizes of the D-STATCOMs. The main advantage of such codification is that the mixed-integer nonlinear programming model (MINLP) that represents the problem of optimal placement and sizing of the D-STATCOMs in distribution networks only requires a classical power flow method to evaluate the objective function, which implies that it can be implemented in any programming language. The objective function is the total costs of the grid power losses and the annualized investment costs in D-STATCOMs. In addition, to include the impact of the daily load variations, the active and reactive power demand curves are included in the optimization model. Numerical results in two radial test feeders with 33 and 69 buses demonstrate that the proposed DCVSA can solve the MINLP model with best results when compared with the MINLP solvers available in the GAMS software. All the simulations are implemented in MATLAB software using its programming environment. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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23 pages, 3788 KiB

Open AccessArticle

Household Energy Management

by Piotr Powroźnik, Robert Szulim, Wiesław Miczulski and Krzysztof Piotrowski

Appl. Sci. 2021, 11(4), 1626; https://doi.org/10.3390/app11041626 - 11 Feb 2021

Cited by 4 | Viewed by 1948

Abstract

Ensuring flexibility and security in power systems requires the use of appropriate management measures on the demand side. The article presents the results of work related to energy management in households in which renewable energy sources (RES) can be installed. The main part [...] Read more.

Ensuring flexibility and security in power systems requires the use of appropriate management measures on the demand side. The article presents the results of work related to energy management in households in which renewable energy sources (RES) can be installed. The main part of the article is about the developed elastic energy management algorithm (EEM), consisting of two algorithms, EEM1 and EEM2. The EEM1 algorithm is activated in time periods with a higher energy price. Its purpose is to reduce the power consumed by the appliances to the level defined by the consumer. In contrast, the EEM2 algorithm is run by the Distribution System Operator (DSO) when peak demand occurs. Its purpose is to reduce the power of appliances in a specified time period to the level defined by the DSO. The optimization tasks in both algorithms are based on the Greedy Randomized Adaptive Search Procedure (GRASP) metaheuristic algorithm. The EEM1 and EEM2 algorithms also provide energy consumer comfort. For this purpose, both algorithms take into account the smart appliance parameters proposed in the article: sections of the working devices, power reduction levels, priorities and enablingof time shifting devices. The EEM algorithm in its operation also takes into account the information about the production of power, e.g., generated by the photovoltaic systems. On this basis, it makes decisions on the control of smart appliances. The EEM algorithm also enables inverter control to limit the power transferred from the photovoltaic system to the energy system. Such action is taken on the basis of the DSO request containing the information on the power limits. Such a structure of EEM enables the balancing of energy demand and supply. The possibility of peak demand phenomenon will be reduced. The simulation and experiment results presented in the paper confirmed the rationality and effectiveness of the EEM algorithm. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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11 pages, 4769 KiB

Open AccessArticle

Attenuation of DC-Link Pulsation of a Four-Wire Inverter during Phase Unbalanced Current Operation

by Dariusz Zieliński and Karol Fatyga

Appl. Sci. 2021, 11(3), 1322; https://doi.org/10.3390/app11031322 - 01 Feb 2021

Cited by 1 | Viewed by 1964

Abstract

This paper proposes a control algorithm for a hybrid power electronic AC/DC converter for prosumer applications operating under deep phase current asymmetry. The proposed system allows independent control of active and reactive power for each phase of the power converter without current pulsation [...] Read more.

This paper proposes a control algorithm for a hybrid power electronic AC/DC converter for prosumer applications operating under deep phase current asymmetry. The proposed system allows independent control of active and reactive power for each phase of the power converter without current pulsation on the DC link connected to an energy store. The system and its algorithm are based on a three-phase converter in four-wire topology (AC/DC 3p-4w) with two dual-active bridge (DC/DC) converters, interfaced with a supercapacitor and an energy storage. The control algorithm tests were carried out in a Hardware in the Loop environment. Obtained results indicate that operation with deep unbalances and powers of opposite signs in individual phases leads to current oscillations in the DC link. This phenomenon significantly limits energy storage utilization due to safety and durability reasons. The proposed algorithm significantly reduces the level of pulsation in the DC link which increases safety and reduces strain on lithium-ion storage technology, enabling their application in four-wire converter applications. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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25 pages, 14073 KiB

Open AccessArticle

A Two-Grid Interline Dynamic Voltage Restorer Based on Two Three-Phase Input Matrix Converters

by Sergio Constantino Yáñez-Campos, Gustavo Cerda-Villafaña and José Merced Lozano-García

Appl. Sci. 2021, 11(2), 561; https://doi.org/10.3390/app11020561 - 08 Jan 2021

Cited by 8 | Viewed by 1777

Abstract

Energy quality problems can cause diverse failures of sensitive equipment. Dynamic voltage restorers (DVRs) are devices that have been proposed to protect sensitive loads from voltage sag effects. However, the compensation capacity of DVRs is limited by the amount of energy stored in [...] Read more.

Energy quality problems can cause diverse failures of sensitive equipment. Dynamic voltage restorers (DVRs) are devices that have been proposed to protect sensitive loads from voltage sag effects. However, the compensation capacity of DVRs is limited by the amount of energy stored in the restorer. One way to overcome this limitation is to use the interline DVR (IDVR) structure in which two or more DVRs connected to different feeders share a common DC-link. This paper proposes a new IDVR topology based on two three-phase input matrix converters (TTI-MC) without a capacitor in the dc-link. The TTI-MC integrates the power from two feeders and synthesizes the dc-link voltage. The inverters take the dc-link voltage and generate the appropriate compensation voltages to keep the load voltages stable. Each one of the inverters has its own modulation algorithm which are synchronized with the TTI-MC control. Inverter control is carried out in the reference frame dq and a modified space vector pulse width modulation (MSV-PWM) technique is used. TTI-MC control is performed in the dq reference frame with proportional-integral controllers and the modulation is based on the carrier-based pulse width modulation (MCB-PWM) technique. The proposed Two Input Interline DVR (TI-IDVR) extends its compensation range and has multifunctional capabilities. The efficiency of the proposed TI-IDVR is corroborated by simulations on MATLAB/Simulink. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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34 pages, 21783 KiB

Open AccessArticle

A Fast, Decentralized, Self-Aligned Carrier Method for Multicellular Converters

by Quoc Dung Phan, Guillaume Gateau, Phu Cong Nguyen, Marc Cousineau, Huu Phuc To, Bao Anh Nguyen, Lucas Veit, Romain De Milly and M.Mannes Hillesheim

Appl. Sci. 2021, 11(1), 137; https://doi.org/10.3390/app11010137 - 25 Dec 2020

Cited by 5 | Viewed by 2498

Abstract

This paper proposes a fast, decentralized method for self-aligning the carriers of a multiphase/multilevel converter operating on the basis of phase-shifted pulse width modulation or level-shifted pulse width modulation. In the proposed method, each cell of the converter synchronizes and updates simultaneously its [...] Read more.

This paper proposes a fast, decentralized method for self-aligning the carriers of a multiphase/multilevel converter operating on the basis of phase-shifted pulse width modulation or level-shifted pulse width modulation. In the proposed method, each cell of the converter synchronizes and updates simultaneously its own carrier angle or carrier level based on the information shared with its neighboring cell, such as its angle/level, its index number, and the total number of activated cells of the converter. Different from the conventional decentralized method (with basic and modified updating rules), which requires some conditions in terms of cell number and initial carrier angles to start up and operate properly, the proposed method can be applied to the system with any number of cells and does not require special conditions of initial carrier angles. Further, while the conventional method needs an iteration process to adjust the inter-carrier phase-shifts and can be applied only to a multiphase converter which uses phase-shifted pulse width modulation, the proposed method offers an accurate and fast alignment of phases (for phase-shifted pulse width modulation) or levels (for level-shifted pulse width modulation) and thus can be applied to both multiphase and multilevel converter types. The simulations and the experimental results are presented in detail to show the validity and the effectiveness of the proposed methods. Further, thorough simulations on multiphase converters with different number of cells also show that the proposed method is much faster than the conventional method in both configuration and reconfiguration processes, especially in case the system has a large number of cells. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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Review

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31 pages, 5401 KiB

Open AccessReview

On the Potential Contributions of Matrix Converters for the Future Grid Operation, Sustainable Transportation and Electrical Drives Innovation

by Alexandre Bento, Guilherme Paraíso, Pedro Costa, Lijun Zhang, Thomas Geury, Sónia Ferreira Pinto and José Fernando Silva

Appl. Sci. 2021, 11(10), 4597; https://doi.org/10.3390/app11104597 - 18 May 2021

Cited by 14 | Viewed by 3115

Abstract

Matrix converters have been extensively investigated in academia over the last 3 decades. Several review works targeting matrix converter topologies, commutation strategies, modulation and control techniques have been published. However, to the best of the authors’ knowledge, a review on the potential contributions [...] Read more.

Matrix converters have been extensively investigated in academia over the last 3 decades. Several review works targeting matrix converter topologies, commutation strategies, modulation and control techniques have been published. However, to the best of the authors’ knowledge, a review on the potential contributions of matrix converters for applications that are shaping the electric power sector transition towards decarbonization is lacking, namely applications on smart grids, sustainable transportation and electrical drives. This paper presents an extensive literature review on the more relevant research works targeting applications of matrix converters as an enabling key technology for smart and resilient grids, sustainable transportation, and innovation in variable speed electric drives. Full article

(This article belongs to the Special Issue Power Electronics in Power Networks)

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