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Special Issue "Distributed Renewable Generation"

A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (30 June 2016)

Special Issue Editor

Guest Editor
Prof. Dr. João P. S. Catalão

Faculty of Engineering of the University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal
Website | E-Mail
Interests: power system operations and planning; hydro and thermal scheduling; wind and price forecasting; distributed renewable generation; demand response and smart grids

Special Issue Information

Dear Colleagues,

We are inviting submissions to the Energies Special Issue on “Distributed Renewable Generation”.

In the last decade, the electric energy industry has shown a renewed interest in distributed generation. This new trend has been mainly motivated by advances in generation technologies that have made smaller generating units viable and feasible, along with an increasing awareness of environmental issues. The penetration level of distributed generation units is increasing, and it is expected that this growth will continue over the years to come.

Prospects for a decentralized and renewable-based power generation, eventually displacing conventional power plants, reducing the balancing role of the transmission grid, and shifting intelligence to the distribution grid through the creation of local and regional energy systems, become more and more likely in the near future. The widespread use of distributed generation, renewable technologies, and energy storage at the residential level is a major paradigm shift for the electric energy industry, which has traditionally relied on large centralized power generation, allowing to increase the share of locally- and domestically-produced electricity.

On the one hand, depending on its location and size, it can be beneficial in reducing power losses and increasing the overall efficiency of the power system, enabling the evolution towards a sustainable and smart grid. Distributed renewable generation is also an excellent way to power microgrids, increasing grid resilience through the local ability to deal with an emergency by operating off-grid. On the other hand, new difficulties arise related to stability, voltage control, and power quality issues, among others, which have to be addressed with novel research studies and innovative solutions.

Indeed, integrating massive distributed renewable generation into the grid poses many challenges to the electric energy sector. The uncertainty and variability of solar photovoltaic and wind energy resources adds significant complexity to maintain the security and reliability of the system, so adequate control, operations and planning methodologies and tools are required, as well as demand-side management capabilities. More sophisticated balancing and forecasting tools should also be developed to accommodate renewables intermittency.

The potential benefits, impacts and drawbacks have to the properly ascertained using realistic case studies, advanced simulation studies and/or comprehensive experimental tests, as well as cost-benefit and swot analyses. Hence, this Special Issue aims to address this important area of research related to “Distributed Renewable Generation”.

Prof. João P. S. Catalão
Guest Editor

Keywords

  • Distributed generation
  • Renewable technologies
  • Energy storage
  • Control, operations and planning
  • Demand-side management
  • Forecasting tools

Published Papers (17 papers)

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Research

Open AccessArticle Advanced Pareto Front Non-Dominated Sorting Multi-Objective Particle Swarm Optimization for Optimal Placement and Sizing of Distributed Generation
Energies 2016, 9(12), 982; doi:10.3390/en9120982
Received: 29 June 2016 / Revised: 19 October 2016 / Accepted: 15 November 2016 / Published: 25 November 2016
Cited by 10 | PDF Full-text (9115 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an advanced Pareto-front non-dominated sorting multi-objective particle swarm optimization (Advanced-PFNDMOPSO) method for optimal configuration (placement and sizing) of distributed generation (DG) in the radial distribution system. The distributed generation consists of single and multiple numbers of active power DG, reactive
[...] Read more.
This paper proposes an advanced Pareto-front non-dominated sorting multi-objective particle swarm optimization (Advanced-PFNDMOPSO) method for optimal configuration (placement and sizing) of distributed generation (DG) in the radial distribution system. The distributed generation consists of single and multiple numbers of active power DG, reactive power DG and simultaneous placement of active-reactive power DG. The optimization problem considers two multi-objective functions, i.e., power loss reduction and voltage stability improvements with voltage profile and power balance as constraints. First, the numerical output results of objective functions are obtained in the Pareto-optimal set. Later, fuzzy decision model is engendered for final selection of the compromised solution. The proposed method is employed and tested on standard IEEE 33 bus systems. Moreover, the results of proposed method are validated with other optimization algorithms as reported by others in the literature. The overall outcome shows that the proposed method for optimal placement and sizing gives higher capability and effectiveness to the final solution. The study also reveals that simultaneous placement of active-reactive power DG reduces more power losses, increases voltage stability and voltage profile of the system. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Stator Current Harmonic Reduction in a Novel Half Quasi-Z-Source Wind Power Generation System
Energies 2016, 9(10), 770; doi:10.3390/en9100770
Received: 2 May 2016 / Revised: 11 August 2016 / Accepted: 20 September 2016 / Published: 23 September 2016
PDF Full-text (5991 KB) | HTML Full-text | XML Full-text
Abstract
The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD) because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the
[...] Read more.
The generator stator current gets distorted with unacceptable levels of total harmonic distortion (THD) because impedance-source wind power generation systems use three-phase diode rectifiers. The stator current harmonics will cause increasing losses and torque ripple, which reduce the efficiency and stability of the system. This paper proposes a novel half quasi-Z-source inverter (H-qZSI) for grid-connected wind power generation systems, which can reduce the generator stator current harmonics a great deal. When H-qZSI operates in the shoot-through zero state, the derivative of the generator stator current is only determined by the instantaneous value of the generator stator voltage, so the nonlinear relationship between generator stator current and stator voltage is improved compared with the traditional impedance-source inverter. Theoretically, it is indicated that the stator current harmonics can be reduced effectively by means of the proposed H-qZSI. Finally, simulation and experimental results are given to verify the theoretical analysis. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Technical Evaluation of Superconducting Fault Current Limiters Used in a Micro-Grid by Considering the Fault Characteristics of Distributed Generation, Energy Storage and Power Loads
Energies 2016, 9(10), 769; doi:10.3390/en9100769
Received: 26 June 2016 / Revised: 6 September 2016 / Accepted: 19 September 2016 / Published: 23 September 2016
Cited by 3 | PDF Full-text (5785 KB) | HTML Full-text | XML Full-text
Abstract
Concerning the development of a micro-grid integrated with multiple intermittent renewable energy resources, one of the main issues is related to the improvement of its robustness against short-circuit faults. In a sense, the superconducting fault current limiter (SFCL) can be regarded as a
[...] Read more.
Concerning the development of a micro-grid integrated with multiple intermittent renewable energy resources, one of the main issues is related to the improvement of its robustness against short-circuit faults. In a sense, the superconducting fault current limiter (SFCL) can be regarded as a feasible approach to enhance the transient performance of a micro-grid under fault conditions. In this paper, the fault transient analysis of a micro-grid, including distributed generation, energy storage and power loads, is conducted, and regarding the application of one or more flux-coupling-type SFCLs in the micro-grid, an integrated technical evaluation method considering current-limiting performance, bus voltage stability and device cost is proposed. In order to assess the performance of the SFCLs and verify the effectiveness of the evaluation method, different fault cases of a 10-kV micro-grid with photovoltaic (PV), wind generator and energy storage are simulated in the MATLAB software. The results show that, the efficient use of the SFCLs for the micro-grid can contribute to reducing the fault current, improving the voltage sags and suppressing the frequency fluctuations. Moreover, there will be a compromise design to fully take advantage of the SFCL parameters, and thus, the transient performance of the micro-grid can be guaranteed. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Impact of Rural Grid-Connected Photovoltaic Generation Systems on Power Quality
Energies 2016, 9(9), 739; doi:10.3390/en9090739
Received: 21 June 2016 / Revised: 25 August 2016 / Accepted: 2 September 2016 / Published: 12 September 2016
Cited by 9 | PDF Full-text (2689 KB) | HTML Full-text | XML Full-text
Abstract
Photovoltaic (PV) generation systems have been increasingly used to generate electricity from renewable sources, attracting a growing interest. Recently, grid connected PV micro-generation facilities in individual homes have increased due to governmental policies as well as greater attention by industry. As low voltage
[...] Read more.
Photovoltaic (PV) generation systems have been increasingly used to generate electricity from renewable sources, attracting a growing interest. Recently, grid connected PV micro-generation facilities in individual homes have increased due to governmental policies as well as greater attention by industry. As low voltage (LV) distribution systems were built to make energy flow in one direction, the power feed-in of PV generation in rural low-voltage grids can influence power quality (PQ) as well as facility operation and reliability. This paper presents results on PQ analysis of a real PV generation facility connected to a rural low-voltage grid. Voltage fluctuations and voltage harmonic contents were observed. Statistical analysis shows a negative impact on PQ produced by this PV facility and also that only a small fraction of the energy available during a sunny day is converted, provoking losses of revenue and forcing the converter to work in an undesirable operating mode. We discuss the disturbances imposed upon the grid and their outcome regarding technical and economic viability of the PV system, as well as possible solutions. A low-voltage grid strengthening has been suggested and implemented. After that a new PQ analysis shows an improvement in the impact upon PQ, making this facility economically viable. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle A Unified Current Loop Tuning Approach for Grid-Connected Photovoltaic Inverters
Energies 2016, 9(9), 723; doi:10.3390/en9090723
Received: 5 May 2016 / Revised: 23 July 2016 / Accepted: 30 August 2016 / Published: 7 September 2016
Cited by 4 | PDF Full-text (3490 KB) | HTML Full-text | XML Full-text
Abstract
High level penetration of renewable energy sources has reshaped modern electrical grids. For the future grid, distributed renewable power generation plants can be integrated in a larger scale. Control of grid-connected converters is required to achieve fast power reference tracking and further to
[...] Read more.
High level penetration of renewable energy sources has reshaped modern electrical grids. For the future grid, distributed renewable power generation plants can be integrated in a larger scale. Control of grid-connected converters is required to achieve fast power reference tracking and further to present grid-supporting and fault ride-through performance. Among all of the aspects for converter control, the inner current loop for grid-connected converters characterizes the system performance considerably. This paper proposes a unified current loop tuning approach for grid-connected converters that is generally applicable in different cases. A direct discrete-time domain tuning procedure is used, and particularly, the selection of the phase margin and crossover frequency is analyzed, which acts as the main difference compared with the existing studies. As a general method, the approximation in the modeling of the controller and grid filter is avoided. The effectiveness of the tuning approach is validated in both simulation and experimental results with respect to power reference tracking, frequency and voltage supporting. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Optimal Placement of Energy Storage and Wind Power under Uncertainty
Energies 2016, 9(7), 528; doi:10.3390/en9070528
Received: 29 April 2016 / Revised: 4 July 2016 / Accepted: 5 July 2016 / Published: 11 July 2016
Cited by 5 | PDF Full-text (1840 KB) | HTML Full-text | XML Full-text
Abstract
Due to the rapid growth in the amount of wind energy connected to distribution grids, they are exposed to higher network constraints, which poses additional challenges to system operation. Based on regulation, the system operator has the right to curtail wind energy in
[...] Read more.
Due to the rapid growth in the amount of wind energy connected to distribution grids, they are exposed to higher network constraints, which poses additional challenges to system operation. Based on regulation, the system operator has the right to curtail wind energy in order to avoid any violation of system constraints. Energy storage systems (ESS) are considered to be a viable solution to solve this problem. The aim of this paper is to provide the best locations of both ESS and wind power by optimizing distribution system costs taking into account network constraints and the uncertainty associated to the nature of wind, load and price. To do that, we use a mixed integer linear programming (MILP) approach consisting of loss reduction, voltage improvement and minimization of generation costs. An alternative current (AC) linear optimal power flow (OPF), which employs binary variables to define the location of the generation, is implemented. The proposed stochastic MILP approach has been applied to the IEEE 69-bus distribution network and the results show the performance of the model under different values of installed capacities of ESS and wind power. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Study of Short-Term Photovoltaic Power Forecast Based on Error Calibration under Typical Climate Categories
Energies 2016, 9(7), 523; doi:10.3390/en9070523
Received: 25 May 2016 / Revised: 2 July 2016 / Accepted: 2 July 2016 / Published: 8 July 2016
Cited by 3 | PDF Full-text (3045 KB) | HTML Full-text | XML Full-text
Abstract
With the increasing permeability of photovoltaic (PV) power production, the uncertainties and randomness of PV power have played a critical role in the operation and dispatch of the power grid and amplified the abandon rate of PV power. Consequently, the accuracy of PV
[...] Read more.
With the increasing permeability of photovoltaic (PV) power production, the uncertainties and randomness of PV power have played a critical role in the operation and dispatch of the power grid and amplified the abandon rate of PV power. Consequently, the accuracy of PV power forecast urgently needs to be improved. Based on the amplitude and fluctuation characteristics of the PV power forecast error, a short-term PV output forecast method that considers the error calibration is proposed. Firstly, typical climate categories are defined to classify the historical PV power data. On the one hand, due to the non-negligible diversity of error amplitudes in different categories, the probability density distributions of relative error (RE) are generated for each category. Distribution fitting is performed to simulate probability density function (PDF) curves, and the RE samples are drawn from the fitted curves to obtain the sampling values of the RE. On the other hand, based on the fluctuation characteristic of RE, the recent RE data are utilized to analyze the error fluctuation conditions of the forecast points so as to obtain the compensation values of the RE. The compensation values are adopted to sequence the sampling values by choosing the sampling values closest to the compensation ones to be the fitted values of the RE. On this basis, the fitted values of the RE are employed to correct the forecast values of PV power and improve the forecast accuracy. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Quantification and Mitigation of Unfairness in Active Power Curtailment of Rooftop Photovoltaic Systems Using Sensitivity Based Coordinated Control
Energies 2016, 9(6), 436; doi:10.3390/en9060436
Received: 7 April 2016 / Revised: 28 May 2016 / Accepted: 31 May 2016 / Published: 4 June 2016
Cited by 4 | PDF Full-text (5020 KB) | HTML Full-text | XML Full-text
Abstract
With increasing photovoltaic (PV) penetration in low voltage networks (LVNs), voltage regulation is a challenge. Active power curtailment (APC) is one possible solution for mitigating over voltages resulting from active power injection in LVNs. There is an inherent unfairness in the APC scheme.
[...] Read more.
With increasing photovoltaic (PV) penetration in low voltage networks (LVNs), voltage regulation is a challenge. Active power curtailment (APC) is one possible solution for mitigating over voltages resulting from active power injection in LVNs. There is an inherent unfairness in the APC scheme. When generation is high and consumption is low, the voltages at the end of the feeder tend to be the highest. This results in high curtailment of active power output of the inverters located at the end of the feeder and low or even no curtailment for the inverts located closer to the transformer. A secondary voltage controller has been implemented to mitigate this unfairness in APC based voltage support schemes. The focus of this work is to quantify this unfairness and develop methods that enable residential PV owners serviced by the same feeder to participate equally in voltage regulation in the LVN. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
Open AccessArticle Adaptive Protection Scheme for a Distribution System Considering Grid-Connected and Islanded Modes of Operation
Energies 2016, 9(5), 378; doi:10.3390/en9050378
Received: 4 February 2016 / Revised: 8 April 2016 / Accepted: 3 May 2016 / Published: 18 May 2016
Cited by 4 | PDF Full-text (3491 KB) | HTML Full-text | XML Full-text
Abstract
The renewable energy-based distributed generation (DG) implementation in power systems has been an active research area during the last few decades due to several environmental, economic and political factors. Although the integration of DG offers many advantages, several concerns, including protection schemes in
[...] Read more.
The renewable energy-based distributed generation (DG) implementation in power systems has been an active research area during the last few decades due to several environmental, economic and political factors. Although the integration of DG offers many advantages, several concerns, including protection schemes in systems with the possibility of bi-directional power flow, are raised. Thus, new protection schemes are strongly required in power systems with a significant presence of DG. In this study, an adaptive protection strategy for a distribution system with DG integration is proposed. The proposed strategy considers both grid-connected and islanded operating modes, while the adaptive operation of the protection is dynamically realized considering the availability of DG power production (related to faults or meteorological conditions) in each time step. Besides, the modular structure and fast response of the proposed strategy is validated via simulations conducted on the IEEE 13-node test system. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Power Production Losses Study by Frequency Regulation in Weak-Grid-Connected Utility-Scale Photovoltaic Plants
Energies 2016, 9(5), 317; doi:10.3390/en9050317
Received: 17 February 2016 / Revised: 18 March 2016 / Accepted: 6 April 2016 / Published: 25 April 2016
PDF Full-text (1146 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, an increasing penetration of utility-scale photovoltaic plants (USPVPs) leads to a change in dynamic and operational characteristics of the power distribution system. USPVPs must help to maintain the system stability and reliability while implementing minimum technical requirements (MTRs) imposed by the utility
[...] Read more.
Nowadays, an increasing penetration of utility-scale photovoltaic plants (USPVPs) leads to a change in dynamic and operational characteristics of the power distribution system. USPVPs must help to maintain the system stability and reliability while implementing minimum technical requirements (MTRs) imposed by the utility grid. One of the most significant requirements is about frequency regulation (FR). Overall production of USPVPs is reduced significantly by applying FR curves, especially in weak grids with high rate of frequency faults. The introduction of a battery energy storage system (BESS) reduces losses and improves the grid system reliability. Experimental frequency and irradiance data of several weak grids have been used to analyse USPVPs losses related to FR requirements and benefits from the introduction of a BESS. Moreover, its economic viability is showen without the need for any economic incentives. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Load Concentration Factor Based Analytical Method for Optimal Placement of Multiple Distribution Generators for Loss Minimization and Voltage Profile Improvement
Energies 2016, 9(4), 287; doi:10.3390/en9040287
Received: 10 February 2016 / Revised: 28 March 2016 / Accepted: 6 April 2016 / Published: 14 April 2016
Cited by 6 | PDF Full-text (629 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents novel separate methods for finding optimal locations, sizes of multiple distributed generators (DGs) simultaneously and operational power factor in order to minimize power loss and improve the voltage profile in the distribution system. A load concentration factor (LCF) is introduced
[...] Read more.
This paper presents novel separate methods for finding optimal locations, sizes of multiple distributed generators (DGs) simultaneously and operational power factor in order to minimize power loss and improve the voltage profile in the distribution system. A load concentration factor (LCF) is introduced to select the optimal location(s) for DG placement. Exact loss formula based analytical expressions are derived for calculating the optimal sizes of any number of DGs simultaneously. Since neither optimizing the location nor optimizing the size is done iteratively, like existing methods do, the simulation time is reduced considerably. The exhaustive method is used to find the operational power factor, and it is shown with the results that the losses are further reduced and voltage profile is improved by operating the DGs at operational power factor. Results for power loss reduction and voltage profile improvement in IEEE 37 and 119 node radial distribution systems are presented and compared with the the loss sensitivity factor (LSF) method, improved analytical (IA) and exhaustive load flow method (ELF). The comparison for operational power factor and other power factors is also presented. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
Open AccessArticle Robust Optimization-Based Scheduling of Multi-Microgrids Considering Uncertainties
Energies 2016, 9(4), 278; doi:10.3390/en9040278
Received: 19 February 2016 / Revised: 25 March 2016 / Accepted: 1 April 2016 / Published: 9 April 2016
Cited by 24 | PDF Full-text (8187 KB) | HTML Full-text | XML Full-text
Abstract
Scheduling of multi-microgrids (MMGs) is one of the important tasks in MMG operation and it faces new challenges as the integration of demand response (DR) programs and renewable generation (wind and solar) sources increases. In order to address these challenges, robust optimization (RO)-based
[...] Read more.
Scheduling of multi-microgrids (MMGs) is one of the important tasks in MMG operation and it faces new challenges as the integration of demand response (DR) programs and renewable generation (wind and solar) sources increases. In order to address these challenges, robust optimization (RO)-based scheduling has been proposed in this paper considering uncertainties in both renewable energy sources and forecasted electric loads. Initially, a cost minimization deterministic model has been formulated for the MMG system. Then, it has been transformed to a min-max robust counterpart and finally, a traceable robust counterpart has been formulated using linear duality theory and Karush–Kuhn–Tucker (KKT) optimality conditions. The developed model provides immunity against the worst-case realization within the provided uncertainty bounds. Budget of uncertainty has been used to develop a trade-off between the conservatism of solution and probability of unfeasible solution. The effect of uncertainty gaps on internal and external trading, operation cost, unit commitment of dispatchable generators, and state of charge (SOC) of battery energy storage systems (BESSs) have also been analyzed in both grid-connected and islanded modes. Simulations results have proved the robustness of proposed strategy. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle A Novel DC-Bus Sensor-less MPPT Technique for Single-Stage PV Grid-Connected Inverters
Energies 2016, 9(4), 248; doi:10.3390/en9040248
Received: 29 December 2015 / Revised: 18 March 2016 / Accepted: 21 March 2016 / Published: 30 March 2016
Cited by 3 | PDF Full-text (12787 KB) | HTML Full-text | XML Full-text
Abstract
Single-stage grid connected inverters are considered as an economic, compact and simple topology compared with multi-stage inverters. In photovoltaic (PV) grid connected systems, the major requirement is to achieve maximum output power from the source. Maximum Power Point Tracking (MPPT) techniques require measurements
[...] Read more.
Single-stage grid connected inverters are considered as an economic, compact and simple topology compared with multi-stage inverters. In photovoltaic (PV) grid connected systems, the major requirement is to achieve maximum output power from the source. Maximum Power Point Tracking (MPPT) techniques require measurements on the DC side of the inverter connected to the PV in order to determine the current operating point on the power characteristics. Typically this is achieved by perturbing the reference output power and observe the change in the PV voltage, current or both. Based on the observation, it could be determined whether the current operating point is beyond or below maximum power. This paper presents an MPPT technique for a single-stage PV grid connected inverter where the MPPT algorithm determines the current operating point at different operating conditions based upon observing the inverter controller action. Such approach eliminates the requirement of sensing elements to be added to the converter which aids the advantages of the single-stage converter. Design of the utilized PV system is derived based on filter parameters, PV panel selection and controller parameters. Using simulation and practical implementation, the performance of the proposed MPPT technique is evaluated for the PV grid connected system. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
Open AccessArticle Modeling and Control of the Distributed Power Converters in a Standalone DC Microgrid
Energies 2016, 9(3), 217; doi:10.3390/en9030217
Received: 25 January 2016 / Revised: 13 March 2016 / Accepted: 14 March 2016 / Published: 18 March 2016
Cited by 7 | PDF Full-text (2691 KB) | HTML Full-text | XML Full-text
Abstract
A standalone DC microgrid integrated with distributed renewable energy sources, energy storage devices and loads is analyzed. To mitigate the interaction among distributed power modules, this paper describes a modeling and control design procedure for the distributed converters. The system configuration and steady-state
[...] Read more.
A standalone DC microgrid integrated with distributed renewable energy sources, energy storage devices and loads is analyzed. To mitigate the interaction among distributed power modules, this paper describes a modeling and control design procedure for the distributed converters. The system configuration and steady-state analysis of the standalone DC microgrid under study are discussed first. The dynamic models of the distributed converters are then developed from two aspects corresponding to their two operating modes, device-regulating mode and bus-regulating mode. Average current mode control and linear compensators are designed accordingly for each operating mode. The stability of the designed system is analyzed at last. The operation and control design of the system are verified by simulation results. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
Open AccessArticle Coordinated Voltage Control in Distribution Network with the Presence of DGs and Variable Loads Using Pareto and Fuzzy Logic
Energies 2016, 9(2), 107; doi:10.3390/en9020107
Received: 9 July 2015 / Revised: 22 December 2015 / Accepted: 13 January 2016 / Published: 17 February 2016
Cited by 1 | PDF Full-text (6609 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an efficient algorithm to solve the multi-objective (MO) voltage control problem in distribution networks. The proposed algorithm minimizes the following three objectives: voltage variation on pilot buses, reactive power production ratio deviation, and generator voltage deviation. This work leverages two
[...] Read more.
This paper presents an efficient algorithm to solve the multi-objective (MO) voltage control problem in distribution networks. The proposed algorithm minimizes the following three objectives: voltage variation on pilot buses, reactive power production ratio deviation, and generator voltage deviation. This work leverages two optimization techniques: fuzzy logic to find the optimum value of the reactive power of the distributed generation (DG) and Pareto optimization to find the optimal value of the pilot bus voltage so that this produces lower losses under the constraints that the voltage remains within established limits. Variable loads and DGs are taken into account in this paper. The algorithm is tested on an IEEE 13-node test feeder and the results show the effectiveness of the proposed model. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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Open AccessArticle Optimal Siting and Sizing of Distributed Generators in Distribution Systems Considering Cost of Operation Risk
Energies 2016, 9(1), 61; doi:10.3390/en9010061
Received: 9 December 2015 / Revised: 11 January 2016 / Accepted: 14 January 2016 / Published: 20 January 2016
Cited by 4 | PDF Full-text (4329 KB) | HTML Full-text | XML Full-text
Abstract
With the penetration of distributed generators (DGs), operation planning studies are essential in maintaining and operating a reliable and secure power system. Appropriate siting and sizing of DGs could lead to many positive effects forthe distribution system concerned, such as the reduced total
[...] Read more.
With the penetration of distributed generators (DGs), operation planning studies are essential in maintaining and operating a reliable and secure power system. Appropriate siting and sizing of DGs could lead to many positive effects forthe distribution system concerned, such as the reduced total costs associated with DGs, reduced network losses, and improved voltage profiles and enhanced power-supply reliability. In this paper, expected load interruption cost is used as the assessment of operation risk in distribution systems, which is assessed by the point estimate method (PEM). In light with the costs of system operation planning, a novel mathematical model of chance constrained programming (CCP) framework for optimal siting and sizing of DGs in distribution systems is proposed considering the uncertainties of DGs. And then, a hybrid genetic algorithm (HGA), which combines the GA with traditional optimization methods, is employed to solve the proposed CCP model. Finally,the feasibility and effectiveness of the proposed CCP model are verified by the modified IEEE 30-bus system, and the test results have demonstrated that this proposed CCP model is more reasonable to determine the siting and sizing of DGs compared with traditional CCP model. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
Open AccessArticle Capacitor Voltage Ripple Suppression for Z-Source Wind Energy Conversion System
Energies 2016, 9(1), 56; doi:10.3390/en9010056
Received: 8 December 2015 / Revised: 12 January 2016 / Accepted: 13 January 2016 / Published: 19 January 2016
Cited by 2 | PDF Full-text (3043 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an improved pulse-width modulation (PWM) strategy to reduce the capacitor voltage ripple in Z-source wind energy conversion system. In order to make sure that Z-source capacitor voltage has symmetrical maximum and minimum amplitudes in each active state, the shoot-through time
[...] Read more.
This paper proposes an improved pulse-width modulation (PWM) strategy to reduce the capacitor voltage ripple in Z-source wind energy conversion system. In order to make sure that Z-source capacitor voltage has symmetrical maximum and minimum amplitudes in each active state, the shoot-through time is divided into six unequal parts. According to the active state and zero state, the shoot-through time is rearranged to match the charging time and discharging time of the Z-source capacitors. Theoretically, it is indicated that the voltage ripple of the Z-source capacitors can be reduced effectively by means of the proposed PWM scheme. Finally, simulation and experimental results are given to verify the performance of the presented method. Full article
(This article belongs to the Special Issue Distributed Renewable Generation)
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