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20 pages, 3971 KiB

Open AccessArticle

Potential of Photovoltaic Generation in the Putumayo Department of Colombia

by Carlos Fernando Luna Carlosama, Ricardo Moreno Chuquen, Luis Fernando Mulcue Nieto and Francy Nelly Jiménez García

Appl. Sci. 2021, 11(12), 5528; https://doi.org/10.3390/app11125528 - 15 Jun 2021

Cited by 3 | Viewed by 2052

Abstract

The potential for generating electricity with photovoltaic systems is high in Colombia given its geographical position in the tropic. Some departments in Colombia have low electricity coverage and high rates. In the department of Putumayo there is a low coverage rate and high [...] Read more.

The potential for generating electricity with photovoltaic systems is high in Colombia given its geographical position in the tropic. Some departments in Colombia have low electricity coverage and high rates. In the department of Putumayo there is a low coverage rate and high energy costs, while the solar radiation potential is high. Due to the geographical differences of the Putumayo subregions, the radiation potential for electricity generation is unknown. In addition, in this department the energy tariffs are above the national average. The objective of this paper is to determine the effective potential for solar photovoltaic power generation in the Putumayo department with a detailed methodology considering the information of different remote database and meteorological stations and some technical conditions. It was found that the highest effective solar potential occurs in the Amazon region, and the lowest in the Andean region in the Putumayo. On the other hand, when evaluating electricity consumption and tariffs in the regions, it is concluded that consumption can be satisfied with photovoltaic systems by producing self-generating electricity and distributed generation. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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13 pages, 2130 KiB

Open AccessArticle

Investigating the Effect of Uncertainty Characteristics of Renewable Energy Resources on Power System Flexibility

by Changgi Min

Appl. Sci. 2021, 11(12), 5381; https://doi.org/10.3390/app11125381 - 10 Jun 2021

Cited by 5 | Viewed by 1907

Abstract

This study investigates the effect of uncertainty characteristics of renewable energy resources on the flexibility of a power system. The more renewable energy resources introduced, the greater the imbalance between load and generation. Securing the flexibility of the system is becoming important to [...] Read more.

This study investigates the effect of uncertainty characteristics of renewable energy resources on the flexibility of a power system. The more renewable energy resources introduced, the greater the imbalance between load and generation. Securing the flexibility of the system is becoming important to manage this situation. The degree of flexibility cannot be independent of the uncertainty of the power system. However, most existing studies on flexibility have not explicitly considered the effects of uncertainty characteristics. Therefore, this study proposes a method to quantitatively analyze the effect of uncertainty characteristics on power system flexibility. Here, the uncertainties of the power system indicate the net load forecast error, which can be represented as a probability distribution. Of the characteristics of the net load forecast error, skewness and kurtosis were considered. The net load forecast error was modeled with a Pearson distribution, which has been widely used to generate the probability density function with skewness and kurtosis. Scenarios for the forecast net load, skewness, and kurtosis were generated, and their effects on flexibility were evaluated. The simulation results for the scenarios based on a modified IEEE-RTS-96 revealed that skewness is more effective than kurtosis. The proposed method can help system operators to efficiently respond to changes in the uncertainty characteristics of renewable energy resources. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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18 pages, 4989 KiB

Open AccessArticle

A Novel Method for Network Design and Optimization of District Energy Systems: Considering Network Topology Planning and Pipe Diameter

by Jiazheng Wu, Hongyun Liu, Yingjun Ruan, Shanshan Wang, Jiamin Yuan and Huiming Lu

Appl. Sci. 2021, 11(4), 1795; https://doi.org/10.3390/app11041795 - 18 Feb 2021

Cited by 2 | Viewed by 2305

Abstract

This paper proposes a new network topology design method that considers all the road nodes, energy stations and load centers to ensure the distribution of pipes along the road. The traditional graph theory and Prim Minimum Spanning Tree (MST) are used to simplify [...] Read more.

This paper proposes a new network topology design method that considers all the road nodes, energy stations and load centers to ensure the distribution of pipes along the road. The traditional graph theory and Prim Minimum Spanning Tree (MST) are used to simplify the map and minimize the length of the pipeline. After analyzing the limitations of the traditional network topology model, Point-to-Point (PTP), we present a new model, Energy Station-to-Load Point (ESLP). The model is optimized by minimum cost, not the shortest path. Finally, Pipe Diameter Grading (PDG) is proposed based on ESLP by solving for the pipe diameter that gives the minimum cost under different load demands in the process of optimization. The network design method is effectively applied in a case, and the results show that the path of the optimized plan is 1.88% longer than that of the pre-optimized plan, but the cost is 2.38% lower. The sensitivity analysis shows that the cost of pipeline construction, project life and electricity price all have an impact on the optimization results, and the cost of pipeline construction is the most significant. The difference between the different classifications of pipelines affects whether PDG is effective or not. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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19 pages, 9651 KiB

Open AccessArticle

Current Interactions Mitigation in 3-Phase PFC Modular Rectifier through Differential-Mode Choke Filter Boost Converter

by José Teixeira Gonçalves, Stanimir Valtchev and Rui Melicio

Appl. Sci. 2021, 11(4), 1684; https://doi.org/10.3390/app11041684 - 13 Feb 2021

Cited by 2 | Viewed by 2353

Abstract

In this paper, a new way to mitigate the current interactions is proposed. The problem of current interactions arises when a modular three-phase (3-phase) rectifier (three single-phase modules) with boost converter for power factor correction (PFC) is used. A new differential-mode choke filter [...] Read more.

In this paper, a new way to mitigate the current interactions is proposed. The problem of current interactions arises when a modular three-phase (3-phase) rectifier (three single-phase modules) with boost converter for power factor correction (PFC) is used. A new differential-mode choke filter is implemented in the developed boost converter. The choke here is a specially made differential inductor in the input of the boost converter that eliminates the known current interactions. To prove the new concept, a study of the level of mitigation of the current interactions is presented. The control is operated in continuous driving mode (CCM), and the popular UC3854B circuit was used for this. The rectifier proposal is validated through a set of simulations performed on the PSIM 12.0 platform, as well as the construction of a prototype. With the results obtained, it is confirmed that the differential-mode choke filter eliminates the current interactions. It is observed that at the input of the rectifier, a sinusoidal alternating current with a low level of harmonic distortion is consumed from the grid. The sinusoidal shape of the phase current proves that a better power factor capable of meeting the international standards is obtained, and that the circuit in its initial version is operational. This proven result promises a good PFC operation, to guarantee the better quality of the electrical energy, being able to be applied in systems that require a high PFC, e.g., in battery charging, wind systems, or in aeronautics and spacecrafts. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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19 pages, 4145 KiB

Open AccessArticle

Bi-Level Dispatch and Control Architecture for Power System in China Based on Grid-Friendly Virtual Power Plant

by Qingwen Xu, Yongji Cao, Hengxu Zhang, Wen Zhang and Vladimir Terzija

Appl. Sci. 2021, 11(3), 1282; https://doi.org/10.3390/app11031282 - 30 Jan 2021

Cited by 13 | Viewed by 2114

Abstract

Non-synchronous renewable energy sources (RESs) have strong volatility and low inertia, which brings about great challenges on the accommodation of RESs and the security and stability of power systems. This paper proposes a bi-level power system dispatch and control architecture based on the [...] Read more.

Non-synchronous renewable energy sources (RESs) have strong volatility and low inertia, which brings about great challenges on the accommodation of RESs and the security and stability of power systems. This paper proposes a bi-level power system dispatch and control architecture based on the grid-friendly virtual power plant (GVPP), so as to accommodate RESs flexibly and securely. The typical dispatch and control system of the power system in China is presented, and the particular challenges stemming from non-synchronous RESs are analyzed. The functional requirements, concept, and fundamental design of the GVPP are provided, which is distinguished from traditional virtual power plants (VPPs) for its active participation in power system stability control. Based on the cloud platform, a bi-level dispatch and control architecture considering two objectives is established. First, in the inner level, the GVPP operates to promote the accommodation of RESs under normal condition. Then, from the perspective of out-level power systems, GVPPs serve as spinning reserves for power support under contingencies. Besides, the key problems to be solved in the development of the GVPP-based architecture are summarized. Although the architecture is proposed for the power system in China, it can be applied to any power systems with similar challenges. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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18 pages, 675 KiB

Open AccessArticle

Optimal Coordination of Over-Current Relays in Microgrids Using Unsupervised Learning Techniques

by Sergio D. Saldarriaga-Zuluaga, Jesús M. López-Lezama and Nicolás Muñoz-Galeano

Appl. Sci. 2021, 11(3), 1241; https://doi.org/10.3390/app11031241 - 29 Jan 2021

Cited by 13 | Viewed by 2145

Abstract

Microgrids constitute complex systems that integrate distributed generation (DG) and feature different operational modes. The optimal coordination of directional over-current relays (DOCRs) in microgrids is a challenging task, especially if topology changes are taken into account. This paper proposes an adaptive protection approach [...] Read more.

Microgrids constitute complex systems that integrate distributed generation (DG) and feature different operational modes. The optimal coordination of directional over-current relays (DOCRs) in microgrids is a challenging task, especially if topology changes are taken into account. This paper proposes an adaptive protection approach that takes advantage of multiple setting groups that are available in commercial DOCRs to account for network topology changes in microgrids. Because the number of possible topologies is greater than the available setting groups, unsupervised learning techniques are explored to classify network topologies into a number of clusters that is equal to the number of setting groups. Subsequently, optimal settings are calculated for every topology cluster. Every setting is saved in the DOCRs as a different setting group that would be activated when a corresponding topology takes place. Several tests are performed on a benchmark IEC (International Electrotechnical Commission) microgrid, evidencing the applicability of the proposed approach. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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19 pages, 5303 KiB

Open AccessArticle

Optimization of Multi-Energy Microgrid Operation in the Presence of PV, Heterogeneous Energy Storage and Integrated Demand Response

by Jingshan Wang, Ke-Jun Li, Yongliang Liang and Zahid Javid

Appl. Sci. 2021, 11(3), 1005; https://doi.org/10.3390/app11031005 - 22 Jan 2021

Cited by 16 | Viewed by 2641

Abstract

In this paper, a model is proposed for the optimal operation of multi-energy microgrids (MEMGs) in the presence of solar photovoltaics (PV), heterogeneous energy storage (HES) and integrated demand response (IDR), considering technical and economic ties among the resources. Uncertainty of solar power [...] Read more.

In this paper, a model is proposed for the optimal operation of multi-energy microgrids (MEMGs) in the presence of solar photovoltaics (PV), heterogeneous energy storage (HES) and integrated demand response (IDR), considering technical and economic ties among the resources. Uncertainty of solar power as well as the flexibility of electrical, cooling and heat load demand are taken into account. A p-efficient point method is applied to compute PV power at different confidence levels based on historical data. This method converts the uncertain PV energy from stochastic to deterministic to be included in the optimization model. The concept of demand response is extended and mathematically modeled using a linear function based on the quantized flexibility interval of multi-energy load demand. As a result, the overall model is formulated as a mixed-integer linear program, which can be effectively solved by the commercial solvers. The proposed model is implemented on two typical summer and winter days for various cases. Results of case studies show the important benefits for maximum PV utilization, energy efficiency and economic system operation. Moreover, the influence of the different confidence levels of PV power and effectiveness of IDR in the stochastic circumstances are addressed in the optimization-based operation. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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18 pages, 8221 KiB

Open AccessArticle

Distributed Generation Control Using Modified PLL Based on Proportional-Resonant Controller

by Ahmad Zare, Mazda Moattari and Rui Melicio

Appl. Sci. 2020, 10(24), 8891; https://doi.org/10.3390/app10248891 - 12 Dec 2020

Cited by 7 | Viewed by 2179

Abstract

Due to the increasing necessity for electrical demand, the microgrids (MGs) based on distributed generations (DGs) within power electronic interfaces are being extended to improve the traditional network control. One of the common ways to achieve power sharing among the resources on an [...] Read more.

Due to the increasing necessity for electrical demand, the microgrids (MGs) based on distributed generations (DGs) within power electronic interfaces are being extended to improve the traditional network control. One of the common ways to achieve power sharing among the resources on an islanding MG is to use the droop control approach, performing based on proportional-integrator (PI) controllers. However, due to the effect of feeder impedance, obtaining the reactive power sharing using this method is not accurate and leads to overload in some DGs, resulting in the output terminal voltage of each DG going outside of the allowable range. The second problem arises when the frequency measurement is not performed precisely, leading to inaccurate active power sharing, which can be solved by using an improved phase locked loop (PLL). Therefore, the purpose of this paper is to propose an applicable and simple approach based on the use of conventional droop characteristics and a proportional-resonant (PR) controller in a DG control system. Due to the load changes in the microgrid and other contingencies, the proposed PLL-based controller is able to represent supreme performance with low error in several case studies. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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19 pages, 303 KiB

Open AccessArticle

An MI-SDP Model for Optimal Location and Sizing of Distributed Generators in DC Grids That Guarantees the Global Optimum

by Walter Gil-González, Alexander Molina-Cabrera, Oscar Danilo Montoya and Luis Fernando Grisales-Noreña

Appl. Sci. 2020, 10(21), 7681; https://doi.org/10.3390/app10217681 - 30 Oct 2020

Cited by 9 | Viewed by 2022

Abstract

This paper deals with a classical problem in power system analysis regarding the optimal location and sizing of distributed generators (DGs) in direct current (DC) distribution networks using the mathematical optimization. This optimization problem is divided into two sub-problems as follows: the optimal [...] Read more.

This paper deals with a classical problem in power system analysis regarding the optimal location and sizing of distributed generators (DGs) in direct current (DC) distribution networks using the mathematical optimization. This optimization problem is divided into two sub-problems as follows: the optimal location of DGs is a problem, with those with a binary structure being the first sub-problem; and the optimal sizing of DGs with a nonlinear programming (NLP) structure is the second sub-problem. These problems originate from a general mixed-integer nonlinear programming model (MINLP), which corresponds to an NP-hard optimization problem. It is not possible to provide the global optimum with conventional programming methods. A mixed-integer semidefinite programming (MI-SDP) model is proposed to address this problem, where the binary part is solved via the branch and bound (B&B) methods and the NLP part is solved via convex optimization (i.e., SDP). The main advantage of the proposed MI-SDP model is the possibility of guaranteeing a global optimum solution if each of the nodes in the B&B search is convex, as is ensured by the SDP method. Numerical validations in two test feeders composed of 21 and 69 nodes demonstrate that in all of these problems, the optimal global solution is reached by the MI-SDP approach, compared to the classical metaheuristic and hybrid programming models reported in the literature. All the simulations have been carried out using the MATLAB software with the CVX tool and the Mosek solver. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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13 pages, 2527 KiB

Open AccessArticle

Improving the Energy Conversion Efficiency for Hydrokinetic Turbines Using MPPT Controller

by Rareș-Andrei Chihaia, Ionuț Vasile, Gabriela Cîrciumaru, Sergiu Nicolaie, Emil Tudor and Constantin Dumitru

Appl. Sci. 2020, 10(21), 7560; https://doi.org/10.3390/app10217560 - 27 Oct 2020

Cited by 7 | Viewed by 2150

Abstract

The research presented in this paper involves the design of a power control system for a hydrokinetic turbine previously tested in real operating conditions. A maximum power point tracking (MPPT) algorithm was designed and simulated using the required parameters for a specific electric [...] Read more.

The research presented in this paper involves the design of a power control system for a hydrokinetic turbine previously tested in real operating conditions. A maximum power point tracking (MPPT) algorithm was designed and simulated using the required parameters for a specific electric generator. The proposed system consists of a generator connected to the hydrokinetic turbine, a three-phase uncontrolled rectifier, a direct current (DC) boost converter with MPPT control to extract maximum available power, and a buck converter to control the amount of power delivered to the load. In order to test the MPPT algorithm, we built the individual blocks on the basis of the corresponding equations of each component. The algorithm considered the specific parameters of the previously tested turbine as input data and simulated the same water velocities for which the turbine had been tested. Thus, the simulation predicted a power output of 105 W for a water velocity of 1.33 m/s, 60 W for 1 m/s, and 30 W for 0.83 m/s. The efficiency of the control system was demonstrated when the instantaneous power value was maintained at a maximum point, regardless of the rotational speed according to the experimental power curves of the driving rotor obtained for certain water velocities. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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21 pages, 3978 KiB

Open AccessArticle

Day Ahead Bidding of a Load Aggregator Considering Residential Consumers Demand Response Uncertainty Modeling

by Zhaofang Song, Jing Shi, Shujian Li, Zexu Chen, Wangwang Yang and Zitong Zhang

Appl. Sci. 2020, 10(20), 7310; https://doi.org/10.3390/app10207310 - 19 Oct 2020

Cited by 12 | Viewed by 1614

Abstract

As the electricity consumption and controllability of residential consumers are gradually increasing, demand response (DR) potentials of residential consumers are increasing among the demand side resources. Since the electricity consumption level of individual households is low, residents’ flexible load resources can participate in [...] Read more.

As the electricity consumption and controllability of residential consumers are gradually increasing, demand response (DR) potentials of residential consumers are increasing among the demand side resources. Since the electricity consumption level of individual households is low, residents’ flexible load resources can participate in demand side bidding through the integration of load aggregator (LA). However, there is uncertainty in residential consumers’ participation in DR. The LA has to face the risk that residents may refuse to participate in DR. In addition, demand side competition mechanism requires the LA to formulate reasonable bidding strategies to obtain the maximum profit. Accordingly, this paper focuses on how the LA formulate the optimal bidding strategy considering the uncertainty of residents’ participation in DR. Firstly, the physical models of flexible loads are established to evaluate the ideal DR potential. On this basis, to quantify the uncertainty of the residential consumers, this paper uses a fuzzy system to construct a model to evaluate the residents’ willingness to participate in DR. Then, based on the queuing method, a bidding decision-making model considering the uncertainty is constructed to maximize the LA’s income. Finally, based on a case simulation of a residential community, the results show that compared with the conventional bidding strategy, the optimal bidding model considering the residents’ willingness can reduce the response cost of the LA and increase the LA’s income. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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20 pages, 740 KiB

Open AccessArticle

A Mathematical Model for the Scheduling of Virtual Microgrids Topology into an Active Distribution Network

by Fernando García-Muñoz, Francisco Díaz-González and Cristina Corchero

Appl. Sci. 2020, 10(20), 7199; https://doi.org/10.3390/app10207199 - 15 Oct 2020

Viewed by 1618

Abstract

This article presents a method based on a mathematical optimization model for the scheduling operation of a distribution network (DN). The contribution of the proposed method is that it permits the configuration and operation of a DN as a set of virtual microgrids [...] Read more.

This article presents a method based on a mathematical optimization model for the scheduling operation of a distribution network (DN). The contribution of the proposed method is that it permits the configuration and operation of a DN as a set of virtual microgrids with a high penetration level of distributed generation (DG) and battery energy storage systems (BESS). The topology of such virtual microgrids are modulated in time in response to grid failures, thus minimizing load curtailment, and maximizing local renewable resource and storage utilization as well. The formulation provides the load reduced by bus to balance the system at every hour and the global probability to present energy not supplied (ENS). Furthermore, for every bus, a flexibility load response range is considered to avoid its total load curtailment for small load reductions. The model has been constructed considering a linear version of the AC optimal power flow (OPF) constraints extended for multiple periods, and it has been tested in a modified version of the IEEE 33-bus radial distribution system considering four different scenarios of 72 h, where the global energy curtailment has been 27.9% without demand-side response (DSR) and 10.4% considering a 30% of flexibility load response. Every scenario execution takes less than a minute, making it appropriate for distribution system operational planning. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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13 pages, 3630 KiB

Open AccessArticle

A Secondary Reconfigurable Inverter and Its Control Strategy

by Yan Li, Peng Xiang and Yandong Chen

Appl. Sci. 2020, 10(20), 7021; https://doi.org/10.3390/app10207021 - 09 Oct 2020

Viewed by 1428

Abstract

This article proposes a topology of the secondary reconfigurable inverter and the corresponding fault-tolerant control strategy. When the secondary reconfigurable inverter is operating normally, its topology structure is the TPSS circuit. When the power semiconductor devices in the inverter are faulty, the inverter [...] Read more.

This article proposes a topology of the secondary reconfigurable inverter and the corresponding fault-tolerant control strategy. When the secondary reconfigurable inverter is operating normally, its topology structure is the TPSS circuit. When the power semiconductor devices in the inverter are faulty, the inverter circuit needs to be reconfigured. After removing the faulty power semiconductor devices, the remaining power semiconductor devices and the DC side powers are reconstructed as the TPFS structure to keep the system running normally. This article also proposes a switch-pulse-resetting algorithm. This paper adopts the control strategy connecting the constant-voltage, constant-frequency control method with the switch pulse resetting algorithm. It need not change the control algorithm when the proposed reconfigurable inverter is transformed from the normal running state into the faulty running state. The inverter dependability is greatly improved. Finally, the feasibility and effectiveness of the proposed second reconfigurable inverter topology and control strategy are verified by simulation and experiment. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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18 pages, 4943 KiB

Open AccessArticle

Grounding System Modeling and Evaluation Using Integrated Circuit Based Fast Relaxed Vector Fitting Approach, Considering Soil Ionization

by Maziyar Fakhraei, Mehrdad Mahmoudian and Eduardo Manuel Godinho Rodrigues

Appl. Sci. 2020, 10(16), 5632; https://doi.org/10.3390/app10165632 - 14 Aug 2020

Cited by 5 | Viewed by 3639

Abstract

Since high voltage transmission line towers or wind turbines structures are installed in high-altitude areas, it is essential to achieve a high overvoltage protection system against direct and indirect lightning strikes collisions. The lightning current must be discharged quickly into the protective earth, [...] Read more.

Since high voltage transmission line towers or wind turbines structures are installed in high-altitude areas, it is essential to achieve a high overvoltage protection system against direct and indirect lightning strikes collisions. The lightning current must be discharged quickly into the protective earth, to prevent the dangerous over-voltages formation and define a reference voltage node. This paper presents a novel model to assess the behavior of the grounding system, based on Pocklington integral equations under lightning magnetic fields and variations in soil ionization, in which an explicit circuit-based vector fitting RLC admittance branches are proposed. The frequency-dependent behavior of grounding system frequency response and soil ionization effect is modeled in time domain, straightly to implement into the electro-magnetic transient program (EMTP). The model verification contains horizontal, vertical, and their combinations of grounding grids to represent the complete investigations under lightning strikes. The harmonic impedance mathematical formulations and principles are derived based on a rational function, that could be applicable on ground potential rise (GPR) investigation. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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30 pages, 4490 KiB

Open AccessArticle

Investigation the Integration of Heliostat Solar Receiver to Gas and Combined Cycles by Energy, Exergy, and Economic Point of Views

by S. M. Alizadeh, Arezoo Ghazanfari, M. A. Ehyaei, Abolfazal Ahmadi, D. H. Jamali, Navid Nedaei and Afshin Davarpanah

Appl. Sci. 2020, 10(15), 5307; https://doi.org/10.3390/app10155307 - 31 Jul 2020

Cited by 20 | Viewed by 3203

Abstract

Due to the high amount of natural gas resources in Iran, the gas cycle as one of the main important power production system is used to produce electricity. The gas cycle has some disadvantages such as power consumption of air compressors, which is [...] Read more.

Due to the high amount of natural gas resources in Iran, the gas cycle as one of the main important power production system is used to produce electricity. The gas cycle has some disadvantages such as power consumption of air compressors, which is a major part of gas turbine electrical production and a considerable reduction in electrical power production by increasing the environment temperature due to a reduction in air density and constant volumetric airflow through a gas cycle. To overcome these weaknesses, several methods are applied such as cooling the inlet air of the system by different methods and integration heat recovery steam generator (HRSG) with the gas cycle. In this paper, using a heliostat solar receiver (HSR) in gas and combined cycles are investigated by energy, exergy, and economic analyses in Tehran city. The heliostat solar receiver is used to heat the pressurized exhaust air from the air compressor in gas and combined cycles. The key parameter of the three mentioned analyses was calculated and compared by writing computer code in MATLAB software. Results showed the use of HSR in gas and combined cycles increase the annual average energy efficiency from 28.4% and 48.5% to 44% and 76.5%, respectively. Additionally, for exergy efficiency, these increases are from 29.2% and 49.8% to 45.2% and 78.5%, respectively. However, from an economic point of view, adding the HRSG increases the payback period (PP) and it decreases the net present value (NPV) and internal rate of return (IRR). Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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27 pages, 16716 KiB

Open AccessFeature PaperArticle

Power Quality Improvement with a Pulse Width Modulation Control Method in Modular Multilevel Converters under Varying Nonlinear Loads

by Majid Mehrasa, Radu Godina, Edris Pouresmaeil, Eduardo M. G. Rodrigues and João P. S. Catalão

Appl. Sci. 2020, 10(9), 3292; https://doi.org/10.3390/app10093292 - 09 May 2020

Cited by 3 | Viewed by 2024

Abstract

In order to reach better results for pulse width modulation (PWM)-based methods, the reference waveforms known as control laws have to be achieved with good accuracy. In this paper, three control laws are created by considering the harmonic components of modular multilevel converter [...] Read more.

In order to reach better results for pulse width modulation (PWM)-based methods, the reference waveforms known as control laws have to be achieved with good accuracy. In this paper, three control laws are created by considering the harmonic components of modular multilevel converter (MMC) state variables to suppress the circulating currents under nonlinear load variation. The first control law consists of only the harmonic components of the MMC’s output currents and voltages. Then, the second-order harmonic of circulating currents is also involved with both upper and lower arm currents in order to attain the second control law. Since circulating current suppression is the main aim of this work, the third control law is formed by measuring all harmonic components of circulating currents which impact on the arm currents as well. By making a comparison between the switching signals generated by the three proposed control laws, it is verified that the second-order harmonic of circulating currents can increase the switching losses. In addition, the existence of all circulating current harmonics causes distributed switching patterns, which is not suitable for the switches’ lifetime. Each upper and lower arm has changeable capacitors, named “equivalent submodule (SM) capacitors” in this paper. To further assess these capacitors, eliminating the harmonic components of circulating currents provides fluctuations with smaller magnitudes, as well as a smaller average value for the equivalent capacitors. Moreover, the second-order harmonic has a dominant role that leads to values higher than 3 F for equivalent capacitors. In comparison with the first and second control laws, the use of the third control-law-based method will result in very small circulating currents, since it is trying to control and eliminate all harmonic components of the circulating currents. This result leads to very small magnitudes for both the upper and lower arm currents, noticeably decreasing the total MMC losses. All simulation results are verified using MATLAB software in the SIMULINK environment. Full article

(This article belongs to the Special Issue Resilient and Sustainable Distributed Energy Systems)

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