scholarly journals Phase Balancing and Reactive Power Support Services for Microgrids

2019 ◽  
Vol 9 (23) ◽  
pp. 5067 ◽  
Author(s):  
Anastasis Charalambous ◽  
Lenos Hadjidemetriou ◽  
Lazaros Zacharia ◽  
Angelina D. Bintoudi ◽  
Apostolos C. Tsolakis ◽  
...  
Keyword(s):  
Distribution System ◽  
Reactive Power ◽  
Renewable Energy Sources ◽  
Ancillary Services ◽  
Active Components ◽  
Modern Distribution ◽  
Central Controller ◽  
High Penetration ◽  
Point Of Common Coupling ◽  
Distribution Grids

Alternating current (AC) microgrids are expected to operate as active components within smart distribution grids in the near future. The high penetration of intermittent renewable energy sources and the rapid electrification of the thermal and transportation sectors pose serious challenges that must be addressed by modern distribution system operators. Hence, new solutions should be developed to overcome these issues. Microgrids can be considered as a great candidate for the provision of ancillary services since they are more flexible to coordinate their distributed generation sources and their loads. This paper proposes a method for compensating microgrid power factor and loads asymmetries by utilizing advanced functionalities enabled by grid tied inverters of photovoltaics and energy storage systems. Further, a central controller has been developed for adaptively regulating the provision of both reactive power and phase balancing services according to the measured loading conditions at the microgrid’s point of common coupling. An experimental validation with a laboratory scale inverter and a real time hardware in the loop investigation demonstrates that the provision of such ancillary services by the microgrid can significantly improve the operation of distribution grids in terms of power quality, energy losses and utilization of available capacity.

scholarly journals Microgrids as Flexible and Network-Connected Grid Assets in Active Distribution Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Lei Shao ◽  
Xu Zhou ◽  
Ji Li ◽  
Hongli Liu ◽  
Xiaoqi Chen
Keyword(s):  
Renewable Energy ◽  
Distribution System ◽  
Distribution Systems ◽  
Renewable Energy Sources ◽  
Optimal Operation ◽  
Operation Strategy ◽  
Energy Integration ◽  
Modern Distribution ◽  
High Penetration ◽  
Networked Microgrids

The functionalities of microgrids are detailed and thereby expanded in active distribution systems. A versatile and coordinated operation among multiple microgrids is proposed to facilitate the integration of renewable energy sources (RES) in modern distribution grids. Particularly, to meet the requirements of high penetration level of renewables (e.g., photovoltaics and small hydro), more than one networked controlled microgrids are deployed simultaneously in different locations of a distribution system. Therefore, local RES can be aggregated in each microgrids. In order to satisfy the latest standards in terms of renewable energy integration (i.e., IEEE Std. 1547 Rev), an optimal operation strategy is designed to coordinate the operation of multiple microgrids. A simulation model is implemented in MATLAB to validate the proposed networked microgrids and the corresponding operation strategy.

scholarly journals A Two-Step State Estimation Algorithm for Hybrid AC-DC Distribution Grids

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1967
Author(s):  
Gaurav Kumar Roy ◽  
Marco Pau ◽  
Ferdinanda Ponci ◽  
Antonello Monti
Keyword(s):  
State Estimation ◽  
Distribution System ◽  
Renewable Energy Sources ◽  
Estimation Algorithm ◽  
The State ◽  
Second Step ◽  
Distribution Grid ◽  
Dc Distribution ◽  
Attractive Option ◽  
Distribution Grids

Direct Current (DC) grids are considered an attractive option for integrating high shares of renewable energy sources in the electrical distribution grid. Hence, in the future, Alternating Current (AC) and DC systems could be interconnected to form hybrid AC-DC distribution grids. This paper presents a two-step state estimation formulation for the monitoring of hybrid AC-DC grids. In the first step, state estimation is executed independently for the AC and DC areas of the distribution system. The second step refines the estimation results by exchanging boundary quantities at the AC-DC converters. To this purpose, the modulation index and phase angle control of the AC-DC converters are integrated into the second step of the proposed state estimation formulation. This allows providing additional inputs to the state estimation algorithm, which eventually leads to improve the accuracy of the state estimation results. Simulations on a sample AC-DC distribution grid are performed to highlight the benefits resulting from the integration of these converter control parameters for the estimation of both the AC and DC grid quantities.

Analysing integration issues of the microgrid system with utility grid network

2021 ◽  
Vol 22 (1) ◽  
pp. 113-127
Author(s):  
Mulualem Tesfaye ◽  
Baseem Khan ◽  
Om Prakash Mahela ◽  
Hassan Haes Alhelou ◽  
Neeraj Gupta ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Distribution System ◽  
Reactive Power ◽  
Renewable Energy Sources ◽  
Operating Conditions ◽  
Control Mode ◽  
Voltage Source ◽  
Modulation Scheme ◽  
Main Challenge ◽  
Utility Grid

Abstract Generation of renewable energy sources and their interfacing to the main system has turn out to be most fascinating challenge. Renewable energy generation requires stable and reliable incorporation of energy to the low or medium voltage networks. This paper presents the microgrid modeling as an alternative and feasible power supply for Institute of Technology, Hawassa University, Ethiopia. This microgrid consists of a 60 kW photo voltaic (PV) and a 20 kW wind turbine (WT) system; that is linked to the electrical distribution system of the campus by a 3-phase pulse width modulation scheme based voltage source inverters (VSI) and supplying power to the university buildings. The main challenge in this work is related to the interconnection of microgrid with utility grid, using 3-phase VSI controller. The PV and WT of the microgrid are controlled in active and reactive power (PQ) control mode during grid connected operation and in voltage/frequency (V/F) control mode, when the microgrid is switched to the stand-alone operation. To demonstrate the feasibility of proposed microgrid model, MATLAB/Simulink software has been employed. The performance of fully functioning microgrid is analyzed and simulated for a number of operating conditions. Simulation results supported the usefulness of developed microgrid in both mode of operation.

scholarly journals A Proposed Harmonic Monitoring System for Large Power Users Considering Harmonic Limits

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4507
Author(s):  
Rosalia Sinvula ◽  
Khaled Mohamed Abo-Al-Ez ◽  
Mohamed Tariq Kahn
Keyword(s):  
Monitoring System ◽  
Renewable Energy Sources ◽  
Electronic Devices ◽  
Harmonic Distortion ◽  
Large Power ◽  
High Penetration ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
Power Utilities ◽  
The Individual

Most power utilities within Southern Africa are faced with the challenges of harmonic distortion due to the high penetration of renewable energy sources (RES) and the use of electronic devices. There is an excessive total harmonic distortion (THD) measured at the point of common coupling (PCC). In this paper, a proposed harmonic monitoring system for large power users (LPUs) is developed. This proposed system considers harmonic limits of the individual and THD of the customers allowed injecting into the network, which should be part of the contractual electricity supply agreement (ESA). Hence, it will enable the monitoring of harmonic distortion to be smooth by determining whether the customer has passed or failed compliance for individual harmonic order and the THD of the voltage. The measurements of harmonic distortion are done using the Unipower power quality (PQ) analyzers that are connected at different points within the industrial network. Measurements of harmonic distortion of an industrial site are compared to the simulation results performed by DIgSILENT software to validate the proposed harmonic monitoring system. Based on the validation results, it is recommended that the ESA between the power utilities and the customers should consist of the harmonic limits.

scholarly journals Application-Oriented Reactive Power Management in German Distribution Systems Using Decentralized Energy Resources

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4949
Author(s):  
Haonan Wang ◽  
Markus Kraiczy ◽  
Denis Mende ◽  
Sebastian Stöcklein ◽  
Martin Braun
Keyword(s):  
Power Management ◽  
Distribution System ◽  
Distribution Systems ◽  
Reactive Power ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
Measurement Data ◽  
Power Exchange ◽  
High Investment ◽  
Decentralized Energy

Due to higher penetration of renewable energy sources, grid reinforcements, and the utilization of local voltage control strategies, a significant change in the reactive power behavior as well as an increased demand for additional reactive power flexibility in the German power system can be predicted. In this paper, an application-oriented reactive power management concept is proposed, which allows distribution system operators (DSO) to enable a certain amount of reactive power flexibility at the grid interfaces while supporting voltage imitations in the grid. To evaluate its feasibility, the proposed concept is applied for real medium voltage grids in the south of Germany and is investigated comprehensively in different case studies. The results prove the feasibility and reliability of the proposed concept, which allows the DSO to control the reactive power exchange at grid interfaces without causing undesired local voltage problems. In addition, it can be simply adjusted and widely applied in real distribution grids without requiring high investment costs for complex information and communication infrastructures. As a significant contribution, this study provides an ideal bridging solution for DSOs who are facing reactive power issues but have no detailed and advanced monitoring system for their grid. Moreover, the comprehensive investigations in this study are performed in close cooperation with a German DSO, based on a detailed grid model and real measurement data.

scholarly journals Experimental Assessment of a Centralised Controller for High-RES Active Distribution Networks

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3364 ◽  
Author(s):  
Francisco García-López ◽  
Manuel Barragán-Villarejo ◽  
Alejandro Marano-Marcolini ◽  
José Maza-Ortega ◽  
José Martínez-Ramos
Keyword(s):  
Renewable Energy ◽  
Distribution System ◽  
Reactive Power ◽  
Renewable Energy Sources ◽  
Distribution Networks ◽  
Energy Sources ◽  
Renewable Energy Resources ◽  
Real Time Control ◽  
Control Actions ◽  
Active Distribution Networks

This paper assesses the behaviour of active distribution networks with high penetration of renewable energy sources when the control is performed in a centralised manner. The control assets are the on-load tap changers of transformers at the primary substation, the reactive power injections of the renewable energy sources, and the active and reactive power exchanged between adjacent feeders when they are interconnected through a DC link. A scaled-down distribution network is used as the testbed to emulate the behaviour of an active distribution system with massive penetration of renewable energy resources. The laboratory testbed involves hardware devices, real-time control, and communication infrastructure. Several key performance indices are adopted to assess the effects of the different control actions on the system’s operation. The experimental results demonstrate that the combination of control actions enables the optimal integration of a massive penetration of renewable energy.

scholarly journals Reactive Power Management Considering Stochastic Optimization under the Portuguese Reactive Power Policy Applied to DER in Distribution Networks

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4028 ◽  
Author(s):  
Abreu ◽  
Soares ◽  
Carvalho ◽  
Morais ◽  
Simão ◽  
...  
Keyword(s):  
Power Management ◽  
Distribution System ◽  
Power Flow ◽  
Optimal Power Flow ◽  
Reactive Power ◽  
Renewable Energy Sources ◽  
Distribution Network ◽  
Real Data ◽  
Distribution Networks ◽  
System Operator

Challenges in the coordination between the transmission system operator (TSO) and the distribution system operator (DSO) have risen continuously with the integration of distributed energy resources (DER). These technologies have the possibility to provide reactive power support for system operators. Considering the Portuguese reactive power policy as an example of the regulatory framework, this paper proposes a methodology for proactive reactive power management of the DSO using the renewable energy sources (RES) considering forecast uncertainty available in the distribution system. The proposed method applies a stochastic sequential alternative current (AC)-optimal power flow (SOPF) that returns trustworthy solutions for the DSO and optimizes the use of reactive power between the DSO and DER. The method is validated using a 37-bus distribution network considering real data. Results proved that the method improves the reactive power management by taking advantage of the full capabilities of the DER and by reducing the injection of reactive power by the TSO in the distribution network and, therefore, reducing losses.

scholarly journals Ancillary Services Offered by Distributed Renewable Energy Sources at the Distribution Grid Level: An Attempt at Proper Definition and Quantification

2020 ◽  
Vol 10 (20) ◽  
pp. 7106
Author(s):  
Charis S. Demoulias ◽  
Kyriaki-Nefeli D. Malamaki ◽  
Spyros Gkavanoudis ◽  
Juan Manuel Mauricio ◽  
Georgios C. Kryonidis ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Power Plants ◽  
Business Models ◽  
Reactive Power ◽  
Renewable Energy Sources ◽  
Voltage Regulation ◽  
Ancillary Services ◽  
Energy Sources ◽  
Distribution Grid ◽  
Support Functions

The gradual displacement of synchronous generators driven by conventional power plants, due to the increasing penetration of distributed renewable energy sources (DRES) in distribution grids, is creating a shortage of crucial ancillary services (AS) which are vital for the frequency and voltage stability of the grid. These AS, and some new ones, could now be offered by the DRES, particularly those that are converter interfaced, in a coordinated way in order to preserve the grid stability and resilience. Although recent standards and grid codes specify that the DRES exhibit some system support functions, there are no specifications on how to measure and quantify (M & Q) them both at DRES level and in aggregated form. The M & Q of AS is crucial, since it would allow the AS to be treated as tradable AS in the current and future AS markets. This paper attempts to define a number of AS that can be offered by converter-interfaced DRES and suggests methods for their M & Q. The new AS addressed are: (1) inertial response; (2) primary frequency response; (3) active power smoothing (ramp-rate limitation); (4) exchange of reactive power for voltage regulation; (5) fault-ride-through (FRT) and contribution to fault clearing; (6) voltage harmonic mitigation. Additionally, a rough estimation of the additional investment and operational cost, as well as the financial benefits associated with each AS is provided in order to form the basis for the development of business models around each AS in the near future.

A Novel Multi-Functional Grid-Connected Inverter of Renewable Energy Resources

2013 ◽  
Vol 448-453 ◽  
pp. 2191-2194
Author(s):  
Lei Zhou ◽  
Hong Da Liu ◽  
Ming Jie Chen ◽  
Nai Jun Shen
Keyword(s):  
Renewable Energy ◽  
Distribution Systems ◽  
Reactive Power ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
Unit Vector ◽  
Renewable Energy Resources ◽  
Point Of Common Coupling ◽  
Grid Connected Inverter ◽  
And Control

On the basis of analyzing the synthesis application of p-q (instantaneous reactive power) theory and unit vector template, a multi-functional grid-connected inverter (MFGCI) with auxiliary services on power quality enhancement in micro-grid (MG) is presented. The novel control strategy for achieving maximum benefits from these MFGCI when installed in AC MG access to 3-phase 4-wire distribution systems by isolated transformer at the point of common coupling (PCC). This kind of inverter can not only deliver the power generation of renewable energy sources (RESs), but also can perform as active power filter (APF) at their PCC as well as can improve the efficiency of inverter and decrease the hardware investment. Finally, both feasibility and effectiveness of this new topologies and control strategies of MFGCI are verified by PSCAD/EMTDC.

scholarly journals An Improved Dispatch Strategy of a Grid-Connected Hybrid Energy System with High Penetration Level of Renewable Energy

2014 ◽  
Vol 2014 ◽  
pp. 1-18
Author(s):  
Yan Zhang ◽  
Jie Meng ◽  
Bo Guo ◽  
Tao Zhang
Keyword(s):  
Renewable Energy ◽  
Distribution System ◽  
Renewable Energy Sources ◽  
Energy System ◽  
Fast Response ◽  
Time Shift ◽  
Frequency Regulation ◽  
Hybrid Energy ◽  
High Penetration ◽  
Battery Energy

As more and more renewable energy sources (RES) integrated into the conventional distribution system, how to make the current electric grid more reliable and efficient is becoming an important topic the world must face. In order to achieve these goals, grid-connected hybrid energy systems (HES) which contain battery energy storage systems (BESS) and many other advanced technologies have been developed and applied. Many benefits of BESS, such as high density of energy and power, have fast response in energy time-shift, frequency regulation, and so on. This paper focuses on the fluctuation alleviation and power quality improvement of grid-connected HES with high penetration level of RES. A multistage dispatch strategy of BESS for HES is proposed in this paper to mitigate the randomness and intermittence of the power flowed in HES because of high penetration level of RES integration. Four other conventional strategies are also discussed for evaluating the performance of the method proposed in this paper. Detailed cases and corresponding discussions are implemented, and the results show that the method proposed in this paper is more effective and robust than the other conventional strategies.

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