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16 pages, 5907 KiB

Open AccessArticle

A Control Strategy for a Three-Phase Grid Connected PV System under Grid Faults

by El Malleh Khawla, Dhia Elhak Chariag and Lassaad Sbita

Electronics 2019, 8(8), 906; https://doi.org/10.3390/electronics8080906 - 18 Aug 2019

Cited by 20 | Viewed by 5155

Abstract

This paper proposes a Low-Voltage Ride-Through control strategy for a three-phase grid-connected photovoltaic (PV) system. At two stages, the topology is considered for the grid-tied system fed by a photovoltaic generator with a boost converter followed by a three-phase voltage source inverter. A [...] Read more.

This paper proposes a Low-Voltage Ride-Through control strategy for a three-phase grid-connected photovoltaic (PV) system. At two stages, the topology is considered for the grid-tied system fed by a photovoltaic generator with a boost converter followed by a three-phase voltage source inverter. A flexible control strategy is built for the proposed system. It accomplishes the PV converter operations under the normal operating mode and under grid faults (symmetrical and asymmetrical grid voltage sag). The boost converter is controlled via an incremental conductance maximum power point tracking technique to maximize the PV generator power extraction. In the case of voltage sag, the implemented control strategy provides a switch between MPPT mode and non-MPPT mode to ensure the protection of the power converters. Theoretical modeling and simulation studies were performed, and significant results are extracted and presented to prove the effectiveness of the proposed control algorithm. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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15 pages, 1655 KiB

Open AccessFeature PaperArticle

Ancillary Service with Grid Connected PV: A Real-Time Hardware-in-the-Loop Approach for Evaluation of Performances

by Yujia Huo and Giambattista Gruosso

Electronics 2019, 8(7), 809; https://doi.org/10.3390/electronics8070809 - 19 Jul 2019

Cited by 10 | Viewed by 3524

Abstract

The integration of photovoltaic (PV) systems with the grid is undoubtedly an issue of great interest both in terms of energy production, but also as a support to the grid as an ancillary service, but to evaluate the performance of the use of [...] Read more.

The integration of photovoltaic (PV) systems with the grid is undoubtedly an issue of great interest both in terms of energy production, but also as a support to the grid as an ancillary service, but to evaluate the performance of the use of PV in an unconventional way, it is necessary to have reference models to be applied to evaluate the characteristics and integration requirements. In this work, an ancillary service provided by a grid-connected PV is shown and a hardware in the loop simulation environment is created to simulate performances and integration issues. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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10 pages, 327 KiB

Open AccessFeature PaperArticle

Stability Analysis of Grid-Connected Photovoltaic Systems with Dynamic Phasor Model

by Md Rasel Mahmud, Ahmed F. Abdou and Hemanshu Pota

Electronics 2019, 8(7), 747; https://doi.org/10.3390/electronics8070747 - 02 Jul 2019

Cited by 9 | Viewed by 3252

Abstract

The typical layout of power systems is experiencing significant change, due to the high penetration of renewable energy sources (RESs). The ongoing evaluation of power systems is expecting more detailed and accurate mathematical modeling approaches for RESs which are dominated by power electronics. [...] Read more.

The typical layout of power systems is experiencing significant change, due to the high penetration of renewable energy sources (RESs). The ongoing evaluation of power systems is expecting more detailed and accurate mathematical modeling approaches for RESs which are dominated by power electronics. Although modeling techniques based on state–space averaging (SSA) have traditionally been used to mathematically represent the dynamics of power systems, the performance of such a model-based system degrades under high switching frequency. The multi-frequency averaging (MFA)-based higher-index dynamic phasor modeling tool is proposed in this paper, which is entirely new and can provide better estimations of dynamics. Dynamic stability analysis is presented in this paper for the MFA-based higher-index dynamical model of single-stage single-phase (SSSP) grid-connected photovoltaic (PV) systems under different switching frequencies. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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19 pages, 1711 KiB

Open AccessArticle

Analysis of DC Link Energy Storage for Single-Phase Grid-Connected PV Inverters

by Gurhan Ertasgin, David M. Whaley, Nesimi Ertugrul and Wen L. Soong

Electronics 2019, 8(6), 601; https://doi.org/10.3390/electronics8060601 - 29 May 2019

Cited by 13 | Viewed by 4721

Abstract

Single-phase grid-connected photovoltaic (PV) inverters (GCI) are commonly used to feed power back to the utility. However, the inverter output power fluctuates at 100 Hz, which can be seen by the PV panel, and this reduces the PV output power. It is important [...] Read more.

Single-phase grid-connected photovoltaic (PV) inverters (GCI) are commonly used to feed power back to the utility. However, the inverter output power fluctuates at 100 Hz, which can be seen by the PV panel, and this reduces the PV output power. It is important to determine and analyze the correlation between the array voltage and current ripple and the average output power reduction of PV array. Therefore, this paper investigates the relationships between the oscillations due to single-phase switching and the DC link energy storage for PV GCIs. The balanced ripple definition is introduced and compared with the more common centered ripple definition. Some examples are provided that demonstrate the importance of these results, in the inverter design industry. The analysis presented here incorporates inductor trade-offs, which are verified with experimental results. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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19 pages, 6491 KiB

Open AccessArticle

Design of Fuzzy-PI and Fuzzy-Sliding Mode Controllers for Single-Phase Two-Stages Grid-Connected Transformerless Photovoltaic Inverter

by Kamran Zeb, Saif Ul Islam, Waqar Ud Din, Imran Khan, Muhammad Ishfaq, Tiago Davi Curi Busarello, Iftikhar Ahmad and Hee Je Kim

Electronics 2019, 8(5), 520; https://doi.org/10.3390/electronics8050520 - 09 May 2019

Cited by 61 | Viewed by 8155

Abstract

Conventional Energy Resources (CER) are being rapidly replaced by Renewable Energy Resources (RER) due to their abundant, environmentally friendly, clean, and inexhaustible nature. In recent years, Solar Photovoltaic (SPV) energy installation is booming at a rapid rate among various RER. Grid-Connected PVS required [...] Read more.

Conventional Energy Resources (CER) are being rapidly replaced by Renewable Energy Resources (RER) due to their abundant, environmentally friendly, clean, and inexhaustible nature. In recent years, Solar Photovoltaic (SPV) energy installation is booming at a rapid rate among various RER. Grid-Connected PVS required advance DC-link controllers to overcome second harmonic ripple and current controllers to feed-in high-quality current to the grid. This paper successfully presents the design of a Fuzzy-Logic Based PI (F-PI) and Fuzzy-Logic based Sliding Mode Controller (F-SMC) for the DC-link voltage controller and Proportional Resonant (PR) with Resonant Harmonic Compensator (RHC) as a current controller for a Single-Phase Two-Stages Grid-connected Transformerless (STGT) Photovoltaic (PV) Inverter. The current controller is designed with and without a feedforward PV power loop to improve dynamics and control. A Second Order General Integral (SOGI)-based Phase Lock Loop (PLL) is also designed that has a fast-dynamic response, fast-tracking accuracy, and harmonic immunity. A 3 kW STGT-PV system is used for simulation in Matlab/Simulink. A comparative assessment of designed controllers is carried out with a conventionally well-tuned PI controller. The designed controllers improve the steady-state and dynamic performance of the grid-connected PV system. In addition, the results, performance measure analysis, and harmonics contents authenticate the robustness, fastness, and effectiveness of the designed controllers, related to former works. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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26 pages, 14233 KiB

Open AccessArticle

Design of Robust Fuzzy Logic Controller Based on the Levenberg Marquardt Algorithm and Fault Ride Trough Strategies for a Grid-Connected PV System

by Saif Ul Islam, Kamran Zeb, Waqar Ud Din, Imran Khan, Muhammad Ishfaq, Altaf Hussain, Tiago Davi Curi Busarello and Hee Je Kim

Electronics 2019, 8(4), 429; https://doi.org/10.3390/electronics8040429 - 12 Apr 2019

Cited by 17 | Viewed by 4297

Abstract

This paper emphasizes the design and investigation of a new optimization scheme for a grid-connected photovoltaic system (PVS) under unbalance faults. The proposed scheme includes fuzzy logic controller (FLC) based on the Levenberg–Marquardt (LM) optimization technique in coordination with bridge-type-fault-current limiter (BFCL) as [...] Read more.

This paper emphasizes the design and investigation of a new optimization scheme for a grid-connected photovoltaic system (PVS) under unbalance faults. The proposed scheme includes fuzzy logic controller (FLC) based on the Levenberg–Marquardt (LM) optimization technique in coordination with bridge-type-fault-current limiter (BFCL) as the fault ride through (FRT) Strategy. The LM optimization-based control is an iterative process with a fast and robust response and is always convergent. The BFCL reduces the fault currents to rated values without compromising at ripples. A keen and critical comparison of the designed strategy is carried out with a conventionally tuned proportional-integral (PI) controller in coordination with the crowbar FRT strategy. A 100kW MATLAB/Simulink model of a photovoltaic system is used for simulation and analysis of unbalance faults at the point of common-coupling (PCC) and at 5 km away from PCC. It is found that grid-connected PVS is highly influenced by the fault type and less effected by the distribution line length. The simulation results authenticated smooth, stable, ripples with free, robust, and fault-tolerant behavior of the proposed scheme. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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20 pages, 1721 KiB

Open AccessArticle

Improved Fractional Open Circuit Voltage MPPT Methods for PV Systems

by Dmitry Baimel, Saad Tapuchi, Yoash Levron and Juri Belikov

Electronics 2019, 8(3), 321; https://doi.org/10.3390/electronics8030321 - 14 Mar 2019

Cited by 90 | Viewed by 7571

Abstract

This paper proposes two new Maximum Power Point Tracking (MPPT) methods which improve the conventional Fractional Open Circuit Voltage (FOCV) method. The main novelty is a switched semi-pilot cell that is used for measuring the open-circuit voltage. In the first method this voltage [...] Read more.

This paper proposes two new Maximum Power Point Tracking (MPPT) methods which improve the conventional Fractional Open Circuit Voltage (FOCV) method. The main novelty is a switched semi-pilot cell that is used for measuring the open-circuit voltage. In the first method this voltage is measured on the semi-pilot cell located at the edge of PV panel. During the measurement the semi-pilot cell is disconnected from the panel by a pair of transistors, and bypassed by a diode. In the second Semi-Pilot Panel method the open circuit voltage is measured on a pilot panel in a large PV system. The proposed methods are validated using simulations and experiments. It is shown that both methods can accurately estimate the maximum power point voltage, and hence improve the system efficiency. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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15 pages, 3769 KiB

Open AccessArticle

Design of a Low-Cost PV Emulator Applied for PVECS

by Intissar Moussa, Adel Khedher and Adel Bouallegue

Electronics 2019, 8(2), 232; https://doi.org/10.3390/electronics8020232 - 19 Feb 2019

Cited by 41 | Viewed by 5803

Abstract

Applied tests on a real photovoltaic panel for a consolidated analysis require complex experiment setup and permanent availability of climatic conditions. This method is ineffective and can damage the PV system. As a result, PV emulators are highly requested in solar energy conversion [...] Read more.

Applied tests on a real photovoltaic panel for a consolidated analysis require complex experiment setup and permanent availability of climatic conditions. This method is ineffective and can damage the PV system. As a result, PV emulators are highly requested in solar energy conversion and generation research, which rests essentially on a maximum power point tracking control algorithm (MPPT) and an adapting power stage as the DC-DC converter and PV inverter. The PV emulator guarantees a controllable light source environment to act as a real PV system in the laboratory. This paper deals with the study and development of an experimental PV emulator based on logarithmic approximation of the ideal single diode model (ISDM), which is implemented using analog electronic components. Mainly, the PV model, the controller, and the power stages, forming the PV emulator, are described. This simple, low-cost, and efficient device is considered as a nonlinear power supply template replacing the real PV system for any operating point irrespective of the environmental condition changes. The emulated current-voltage and power-voltage curves are validated via resistive load and batteries. Then, the performance of the proposed PV emulator is evaluated by its ability to recharge properly two 12V 7 Ah batteries. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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17 pages, 3904 KiB

Open AccessArticle

LS-Solar-PV System Impact on Line Protection

by Qais Alsafasfeh, Omar A. Saraereh, Imran Khan and Sunghwan Kim

Electronics 2019, 8(2), 226; https://doi.org/10.3390/electronics8020226 - 18 Feb 2019

Cited by 11 | Viewed by 3546

Abstract

Large-scale photovoltaic power station access to the grid will profoundly change the fault current characteristics of the power station’s outgoing lines. This change results in adaptive problems in traditional protection phase selection components, which may cause incorrect actions in reclosing, protection ranging, and [...] Read more.

Large-scale photovoltaic power station access to the grid will profoundly change the fault current characteristics of the power station’s outgoing lines. This change results in adaptive problems in traditional protection phase selection components, which may cause incorrect actions in reclosing, protection ranging, and distance protection. Based on the fault current characteristics of the large-scale photovoltaic power station transmission line, this paper analyzes the adaptability of the phase current difference mutation and the sequence component phase selection component in protecting the Photovoltaic (PV) power plant side of the transmission line. Based on the fault current analytical formula, the phase relationship between the phase current difference and the current sequence component under different control targets, such as suppressing negative sequence current, suppressing the active power fluctuation, and suppressing the reactive power fluctuation, is derived. The operational performances of the phase–phase current difference of the abrupt phase selection component and the sequence component phase selection component of the power station side are degraded, which may cause incorrect operation of the phase selection component. Based on the actual engineering parameters of a PV power plant, a simulation model was built in Power System Computer Aided Design (PSCAD) to verify the correctness of the theoretical analysis. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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18 pages, 5085 KiB

Open AccessFeature PaperArticle

Mitigating the Load Frequency Fluctuations of Interconnected Power Systems Using Model Predictive Controller

by Muhammad Majid Gulzar, Syed Tahir Hussain Rizvi, Muhammad Yaqoob Javed, Daud Sibtain and Rubab Salah ud Din

Electronics 2019, 8(2), 156; https://doi.org/10.3390/electronics8020156 - 01 Feb 2019

Cited by 26 | Viewed by 4224

Abstract

The penetration of renewable energy sources into the conventional power systems are evolving day by day. Therefore, in this paper, a photovoltaic (PV) connected thermal system is discussed and analyzed by keeping PV to operate at maximum power point (MPP). The main problem [...] Read more.

The penetration of renewable energy sources into the conventional power systems are evolving day by day. Therefore, in this paper, a photovoltaic (PV) connected thermal system is discussed and analyzed by keeping PV to operate at maximum power point (MPP). The main problem in the interconnection of these systems is load frequency fluctuations due to different load changing conditions. The model predictive controller (MPC) has the ability to predict the target value at real-time with fast convergence. Therefore, MPC is proposed to negate this problem by giving minimum oscillation. The comparison analysis is carried out with other conventional controllers, including genetic algorithm-based PI, firefly algorithm-based PI and PI controller. Simulation results clearly exhibit the outclass performance of MPC over all other controllers. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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17 pages, 6700 KiB

Open AccessArticle

Economic Analysis of Grid-Connected PV System Regulations: A Hungarian Case Study

by Henrik Zsiborács, Nóra Hegedűsné Baranyai, Szilvia Csányi, András Vincze and Gábor Pintér

Electronics 2019, 8(2), 149; https://doi.org/10.3390/electronics8020149 - 31 Jan 2019

Cited by 34 | Viewed by 7871

Abstract

The energy demand of mankind is constantly growing, thus the utilization of various renewable energy sources, which also reduces negative environmental effects, is becoming more and more important. Because of the achievement of climate protection targets, photovoltaic (PV) energy has an increasing role [...] Read more.

The energy demand of mankind is constantly growing, thus the utilization of various renewable energy sources, which also reduces negative environmental effects, is becoming more and more important. Because of the achievement of climate protection targets, photovoltaic (PV) energy has an increasing role in the global energy mix. This paper presents the technical and economic aspects of different photovoltaic system configurations designed to suit the Hungarian renewable energy regulations. In this study, five alternative PV configurations were examined for systems with a capacity from 50 kW to 500 kW, related to low- and medium-voltage installations. This article also introduces and explains the Hungarian economic PV and Feed-in-Tariff (FiT) regulations, where three different investment alternatives are analyzed with the help of economic indicators. This study could help stakeholders in the market (e.g., the Hungarian industry sector and local governments) understand the possible directions of technical and economic PV development. According to the results, the payback periods in all the studied economic-technical cases were below 10 years. The experimental results show that each investment option may be a good decision from an economic and technical point of view under the Hungarian regulations in force in 2019. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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17 pages, 4890 KiB

Open AccessFeature PaperArticle

Performance Analysis of a Modernized Z-Source Inverter for Robust Boost Control in Photovoltaic Power Conditioning Systems

by Nafis Subhani, Ramani Kannan, Md Apel Mahmud and Mohd Fakhizan Romlie

Electronics 2019, 8(2), 139; https://doi.org/10.3390/electronics8020139 - 29 Jan 2019

Cited by 13 | Viewed by 3678

Abstract

In this paper, the performance of a new Z-source inverter (ZSI)-based single-stage power conditioning system (PCS) is analyzed for a standalone photovoltaic (PV) power generation system. The proposed ZSI-based PCS includes two main parts: one is the input from PV units and the [...] Read more.

In this paper, the performance of a new Z-source inverter (ZSI)-based single-stage power conditioning system (PCS) is analyzed for a standalone photovoltaic (PV) power generation system. The proposed ZSI-based PCS includes two main parts: one is the input from PV units and the other is the ZSI. In this work, a new topology, termed the switched inductor-assisted strong boost ZSI (SL-SBZSI), is introduced for improving the performance of the PCS. The proposed topology shows high boosting capability during the voltage sag in PV units due to variations in solar irradiation and temperature. Another key advantage is the reduced capacitor voltage stress and semiconductor switch voltage stress of the inverter bridge, which ultimately minimizes the size and cost of the single-stage PCS. The proposed ZSI topology falls under the doubly grounded category of inverter by sharing the common ground between the input and output. This is an additional feature that can minimize the leakage current of PV units at the ac output end. The operational principles, detailed mathematical modeling, and characteristics of the proposed SL-SBZSI for a standalone photovoltaic (PV) power generation system is presented in this paper for analyzing performance. The simulation results, which are performed in MATLAB/Simulink, demonstrate the improved performance of the proposed SL-SBZSI for the standalone PV system. The performance of the proposed topology is also evaluated through an experimental validation on a laboratory-based PV system. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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21 pages, 11778 KiB

Open AccessArticle

Rapid Prototyping of a Hybrid PV–Wind Generation System Implemented in a Real-Time Digital Simulation Platform and Arduino

by Víctor Pagola, Rafael Peña, Juan Segundo and Adalberto Ospino

Electronics 2019, 8(1), 102; https://doi.org/10.3390/electronics8010102 - 17 Jan 2019

Cited by 16 | Viewed by 4546

Abstract

The growing penetration of generation systems based on renewable energy in electric power systems is undeniable. These generation systems have many benefits, but also many challenges from the technical point of view. One of the biggest problems in the case of solar photovoltaic [...] Read more.

The growing penetration of generation systems based on renewable energy in electric power systems is undeniable. These generation systems have many benefits, but also many challenges from the technical point of view. One of the biggest problems in the case of solar photovoltaic (PV) and wind energy is the intermittency of the raw material, thus hybrid generation systems that contain both sources are being used to complement electric power generation. To analyze the problems of this type of hybrid generation systems, it is necessary to develop models and test systems that allows to study their dynamic behavior. Reported in this paper is the implementation of a full hybrid PV–wind generation system model in a real-time digital simulation platform, and the development of the electronic converter controls. These controllers were implemented in digital devices (Arduino Due) and connected to the simulation platform to test their performance in real-time. In addition, the procedure followed for the development and implementation of the controllers is presented. The proposed test system can be used in renewable energy integration studies and the development of new control strategies. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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20 pages, 10187 KiB

Open AccessArticle

Design of a Proportional Resonant Controller with Resonant Harmonic Compensator and Fault Ride Trough Strategies for a Grid-Connected Photovoltaic System

by Saif Ul Islam, Kamran Zeb, Waqar Ud Din, Imran Khan, Muhammad Ishfaq, Tiago Davi Curi Busarello and Hee Je Kim

Electronics 2018, 7(12), 451; https://doi.org/10.3390/electronics7120451 - 19 Dec 2018

Cited by 26 | Viewed by 8640

Abstract

This paper presents the design and analysis of a proportional resonant controller with a resonant harmonic compensator and switch-type fault current limiter, as a fault-ride through strategy for a three-phase, grid-connected photovoltaic (PV) system under normal conditions and asymmetrical faults. The switch-type fault [...] Read more.

This paper presents the design and analysis of a proportional resonant controller with a resonant harmonic compensator and switch-type fault current limiter, as a fault-ride through strategy for a three-phase, grid-connected photovoltaic (PV) system under normal conditions and asymmetrical faults. The switch-type fault limiter comprised of current-limiting inductors, a bridge rectifier, a snubber capacitor, linear transformers, and energy absorption bypass. Furthermore, a critical and analytical comparison of switch-type fault limiters is carried out, with the conventional crowbar as the fault-ride through strategy, in combination with a conventionally tuned proportional integrator controller. The designed fault-ride through strategies with proportional integrator and proportional resonant controllers with resonant harmonic compensators are tested at the point of common coupling of the photovoltaic system and at a distance of 19 km from the point of common coupling, in order to analyze the impacts of fault parameter with respect to location. A MATLAB/Simulink model of a 100 kW three-phase grid-connected photovoltaic system is used for analysis. The simulation results of the proposed switch-type fault limiter with proportional resonant controller effectively validate the stable, ripple-free, and robust response compared to all other configurations. In addition, it is also verified that the grid faults on the PV system have a significant impact on fault type, and less impact on fault location. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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18 pages, 5146 KiB

Open AccessArticle

An Advanced Maximum Power Point Tracking Method for Photovoltaic Systems by Using Variable Universe Fuzzy Logic Control Considering Temperature Variability

by Yiwang Wang, Yong Yang, Gang Fang, Bo Zhang, Huiqing Wen, Houjun Tang, Li Fu and Xiaogao Chen

Electronics 2018, 7(12), 355; https://doi.org/10.3390/electronics7120355 - 26 Nov 2018

Cited by 35 | Viewed by 4504

Abstract

In this study maximum power point tracking (MPPT) is applied to the photovoltaic (PV) system to harvest the maximum power output. The output power of the PV effect changes according to external solar irradiation and ambient temperature conditions. In the existing MPPT strategies, [...] Read more.

In this study maximum power point tracking (MPPT) is applied to the photovoltaic (PV) system to harvest the maximum power output. The output power of the PV effect changes according to external solar irradiation and ambient temperature conditions. In the existing MPPT strategies, most of them only take variations in radiation level into account, rarely considering the impact of temperature changes. However, the temperature coefficients (TC) play an important role in the PV system, especially in applications where ambient temperature changes are relatively large. In this paper, an MPPT method is presented for a PV system that considers the temperature change by using variable universe fuzzy logic control (VUFLC). By considering the ambient temperature change in PV modules, the proposed control method can regulate the contraction and expansion factor of VUFLC, which eliminates the influence of temperature variability and improves the performance of MPPT, therefore achieving fast and accurate tracking control. The proposed method was evaluated for a PV module under different ambient conditions and its control performance is compared with other MPPT strategies by simulation and experimental results. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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21 pages, 1795 KiB

Open AccessFeature PaperArticle

A Heuristics-Based Policy to Reduce the Curtailment of Solar-Power Generation Empowered by Energy-Storage Systems

by Robert Basmadjian and Hermann De Meer

Electronics 2018, 7(12), 349; https://doi.org/10.3390/electronics7120349 - 24 Nov 2018

Cited by 11 | Viewed by 3107

Abstract

Renewable energy sources, on one hand, are environmentally friendly, but on the other, they suffer from volatility in power generation, which endangers power-grid stability. A viable solution to circumvent the intermittent behavior of renewables is the usage of energy-storage systems. In this paper, [...] Read more.

Renewable energy sources, on one hand, are environmentally friendly, but on the other, they suffer from volatility in power generation, which endangers power-grid stability. A viable solution to circumvent the intermittent behavior of renewables is the usage of energy-storage systems. In this paper, we study the energy management of a proof-of-concept system consisting of solar panels, energy-storage systems, a power grid, and household loads. Using neural networks, we identify the most relevant parameters impacting the power generation of solar panels, and then train the corresponding network to derive forecasts. We also go one step further, and propose a heuristics-based energy-management policy for the purpose of reducing curtailments. We show that our proposed policy outperforms the naive policy by 8%, which does not consider any power-generation forecasts. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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20 pages, 4904 KiB

Open AccessArticle

Virtual Inertia-Based Control Strategy of Two-Stage Photovoltaic Inverters for Frequency Support in Islanded Micro-Grid

by Xin Huang, Keyou Wang, Guojie Li and Hua Zhang

Electronics 2018, 7(11), 340; https://doi.org/10.3390/electronics7110340 - 21 Nov 2018

Cited by 21 | Viewed by 4350

Abstract

For an islanded micro-grid with a high penetration of photovoltaic (PV) power generators, the low inertia reserve and the maximum peak power tracking control may increase the difficulty of maintaining the system’s supply–demand balance, and cause frequency instability, especially when the available generation [...] Read more.

For an islanded micro-grid with a high penetration of photovoltaic (PV) power generators, the low inertia reserve and the maximum peak power tracking control may increase the difficulty of maintaining the system’s supply–demand balance, and cause frequency instability, especially when the available generation is excessive. This will require changes in the way the PV inverter is controlled. In this paper, a virtual inertia frequency control (VIFC) strategy is proposed to let the two-stage PV inverters emulate inertia and support the system frequency with a timely response (e.g., inertia response), and the required power for inertia emulation is obtained from both the DC-link capacitor and the PV reserved energy. As the rate of the system frequency change can be reduced with the inertia increase, the proposed method can mitigate the frequency contingency event before the superior-level coordination control is enabled for the frequency restoration. The simulation results demonstrate the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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18 pages, 1537 KiB

Open AccessArticle

Partial Feedback Linearizing Model Predictive Controllers for Multiple Photovoltaic Units Connected to Grids through a Point of Common Coupling

by Tahsin Fahima Orchi, Md Apel Mahmud and Amanullah Maung Than Oo

Electronics 2018, 7(9), 175; https://doi.org/10.3390/electronics7090175 - 03 Sep 2018

Cited by 7 | Viewed by 3395

Abstract

In this paper, partial feedback linearizing model predictive controllers are designed for grid-connected systems comprising multiple photovoltaic (PV) units where these units are connected through a point of common coupling (PCC). The proposed controllers are designed for voltage source inverters (VSIs) based on [...] Read more.

In this paper, partial feedback linearizing model predictive controllers are designed for grid-connected systems comprising multiple photovoltaic (PV) units where these units are connected through a point of common coupling (PCC). The proposed controllers are designed for voltage source inverters (VSIs) based on comprehensive dynamical models of grid-connected PV systems with the proposed topology. The proposed partial feedback linearization scheme decouples multiple PV units in the forms of several reduced-order subsystems and enables linear controller design through the linear continuous-time receding horizon model predictive control scheme. The proposed partial feedback linearization scheme also considers dynamic interactions among multiple PV units as external noises or disturbances and decouples these noises. This paper includes the noise decoupling capability of the partial feedback linearization for grid-connected PV systems with multiple PV units which are connected through a PCC. Simulation results clearly demonstrate the effectiveness of the proposed scheme under different operating conditions as compared to an existing proportional integral controller. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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11 pages, 5508 KiB

Open AccessArticle

An Improved Frequency Measurement Method from the Digital PLL Structure for Single-Phase Grid-Connected PV Applications

by Byunggyu Yu

Electronics 2018, 7(8), 150; https://doi.org/10.3390/electronics7080150 - 20 Aug 2018

Cited by 17 | Viewed by 5126

Abstract

The Phase Locked Loop (PLL) technique has been studied to obtain the phase and frequency information in grid-connected distributed generations for the sake of synchronizing the grid voltage and the inverter output current. In particular, the line frequency information, such as the anti-islanding [...] Read more.

The Phase Locked Loop (PLL) technique has been studied to obtain the phase and frequency information in grid-connected distributed generations for the sake of synchronizing the grid voltage and the inverter output current. In particular, the line frequency information, such as the anti-islanding function, is very important for the grid connection requirement. This paper presents a novel frequency measurement method from the digital PLL control structure for single-phase grid-connected PV applications. The conventional PLL controller uses the phase information to calculate the frequency of PV inverter output voltage after every line cycle and has shown a relatively low accuracy. This paper uses the angular frequency to directly measure the frequency after every line cycle. To verify the validity of the proposed method compared with the conventional method, a simulation was conducted. According to the simulation results, the measurement error of the proposed method is 80 times lower than the conventional one. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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11 pages, 18658 KiB

Open AccessArticle

Photovoltaic-STATCOM with Low Voltage Ride through Strategy and Power Quality Enhancement in a Grid Integrated Wind-PV System

by Lakshman Naik Popavath and Palanisamy Kaliannan

Electronics 2018, 7(4), 51; https://doi.org/10.3390/electronics7040051 - 12 Apr 2018

Cited by 43 | Viewed by 8320

Abstract

The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind), resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the [...] Read more.

The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind), resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the islanding of renewables caused by severe voltage variations (voltage sag and swell). Current harmonics and voltage sag strongly affect the performance of renewable-based power systems. Various conventional methods (passive filters, capacitor bank, and UPS) are not able to mitigate harmonics and voltage sag completely. Based on several studies, custom power devices can mitigate harmonics completely and slightly mitigate voltage sags with reactive power supplies. To ensure the generating units remain grid-connected during voltage sags and to improve system operation during abnormal conditions, efficient and reliable utilization of PV solar farm inverter as STATCOMs is needed. This paper elaborates the dynamic performance of a VSC-based PV-STATCOM for power quality enhancement in a grid integrated system and low voltage ride through (LVRT) capability. LVRT requirements suggest that the injection of real and reactive power supports grid voltage during abnormal grid conditions. The proposed strategy was demonstrated with MATLAB simulations. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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18 pages, 1725 KiB

Open AccessReview

Small-Signal Stability Criteria in AC Distribution Systems—A Review

by Atta Ur Rahman, Irtaza Syed and Mukhtar Ullah

Electronics 2019, 8(2), 216; https://doi.org/10.3390/electronics8020216 - 15 Feb 2019

Cited by 7 | Viewed by 3865

Abstract

AC distribution grid is prone to instability due to negative impedance and constant power nature of the load if it is dominant with power electronics-based components. There are various time-domain and frequency-domain modelling methods which use various methodologies and analytical tools. Also, there [...] Read more.

AC distribution grid is prone to instability due to negative impedance and constant power nature of the load if it is dominant with power electronics-based components. There are various time-domain and frequency-domain modelling methods which use various methodologies and analytical tools. Also, there are many small-signal stability analysis (SSSA) methods and their different variants for different specific conditions and situation. This paper presents a review of SSSA methods in AC distribution grid using impedance-based models in a synchronous reference frame (SRF). By simplifying and converting the system into load and source subsystem, the impedances of both subsystems are determined by perturbation method. For a single-phase system, Hilbert transform can be used to derive the equivalent SRF model. Afterwards, the Nyquist stability criterion can be used for stability analysis. Full article

(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)

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