Research on control strategies for distributed inverters in low voltage micro-grids

2010 ◽  
Author(s):  
Chen Hongbing ◽  
Zhang Xing ◽  
Liu Shengyong ◽  
Yang Shuying
Keyword(s):  
Low Voltage ◽  
Control Strategies ◽  
Micro Grids

A Review of Classical and Modern Control Techniques Utilized in Modern Microgrids

2021 ◽  
Vol 14 ◽  
Author(s):  
Muhammad Hamza Shahbaz ◽  
Arslan Ahmed Amin
Keyword(s):  
Control Strategies ◽  
Optimal Solution ◽  
Energy Resources ◽  
Control Methods ◽  
Research Gaps ◽  
Control Techniques ◽  
Micro Grid ◽  
Exciting Development ◽  
Micro Grids ◽  
Modern Control

: Because of the consistently expanding energy request, the introduction of a decentralized micro-grid based on energy resources will soon be the most exciting development in the power system. Micro-grids, which are mainly based on inverters, are becoming more popular as they can handle different forms of renewable energy effectively. However, one of the most challenging areas of research is their control. In the last few years, many control strategies have been developed. In this review, different control methods have been discussed that apply to the micro-grid system. Furthermore, the comparative analysis of classical and modern control strategies is also considered. This survey guides the new researchers about all available control strategies and room for improvement towards the optimal solution of the micro-grid control techniques. It also identifies several research gaps and future trends therein as well as provides a solution to manage problems in MGs. The strategies are then compared based on their applicability to different control requirements.

scholarly journals Comparison of Local Volt/var Control Strategies for PV Hosting Capacity Enhancement of Low Voltage Feeders

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1560 ◽  
Author(s):  
Daniel-Leon Schultis
Keyword(s):  
Reactive Power ◽  
Low Voltage ◽  
Control Strategies ◽  
Load Flow ◽  
Overhead Line ◽  
The Real ◽  
Capacity Increase ◽  
Current Limit ◽  
Theoretical Test ◽  
Pv Penetration

The PV hosting capacity of low voltage feeders is restricted by voltage and current limits, and in many cases, voltage limit violations are the limiting factor for photovoltaic integration. To control the voltage, local Volt/var control strategies absorb or inject reactive power, provoking an additional current. This study analyzes the hosting capacity increase potential and the associated additional grid losses of local cosφ(P)- and Q(U)-control of photovoltaic inverters, and of local L(U)-control of inductive devices and its combination with Q-Autarkic prosumers. Therefore, four theoretical and one real low voltage test-feeders with distinct structures are considered: long overhead line, short overhead line, long cable, short cable and branched cable. While the theoretical test-feeders host homogeneously distributed PV-plants, the real one hosts heterogeneously distributed PV-plants. Each test-feeder is used to conduct load flow simulations in the presence of no-control and the different control strategies separately, while gradually increasing the PV-penetration. The minimum PV-penetration that provokes voltage or current limit violations is compared for the different control strategies and test-feeders. Simulation results of the theoretical test-feeders show that the hosting capacity increase potential of all local Volt/var control strategies is higher for the overhead line feeders than for the cable ones. Local L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of all low voltage test-feeders significantly. The PV-inverter-based local Volt/var control strategies, i.e., Q(U)- and cosφ(P)-control, enable lower hosting capacity increases; in particular, cosφ(P)-control causes high additional currents, allowing the feeder to host only a relatively small PV-module rating per prosumer. Q(U)- and cosφ(P)-control are not sufficient to increase the hosting capacity of the long cable feeder significantly; they provoke high additional grid losses for the overhead line test-feeders. Meanwhile, L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of the long cable feeder significantly, causing high additional grid losses during peak production of PV-plants. Regarding the real test-feeder with heterogeneously distributed PV-plants, on the one hand, the same trend concerning the HC increase prevails for the real branched cable test-feeder as for the theoretical short cable one. On the other hand, higher losses occur for the branched feeder in the case of L(U)-control and its combination with Q-Autarkic prosumers, due to the lower voltage set-points that have to be used for the inductive devices. All in all, the use of local L(U)-control, whether combined with Q-Autarkic prosumers or not, enables the effective and complete utilization of the existing radial low voltage feeders.

Improvement of Power Quality for Microgrid using Fuzzy Based UPQC Controller

2015 ◽  
Vol 4 (2) ◽  
pp. 37
Author(s):  
Abdul Rasheed ◽  
G. Keshava Rao
Keyword(s):  
Fuzzy Logic ◽  
Power Systems ◽  
Power Quality ◽  
Fuzzy Logic Controller ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
Distributed Energy ◽  
Micro Grid ◽  
Hybrid Filters ◽  
Micro Grids

<p>Generally, the power systems are mainly effected by the continuous changes in operational requirement and increasing amount of distributed energy systems. This paper proposes a new concept of power-control strategies for a micro grid generation system for better transfer of power. The micro grids are obtained with the general renewable energy sources and this concept provides the maximum utilization of power at environmental free conditions with low losses; then the system efficiency is also improved. This paper proposes a single stage converter based micro grid to reduce the number of converters in an individual ac or dc grid. The proposed micro grid concept can work in both stand-alone mode and also in grid interfaced mode. The distortions that occur in power system due to changes in load or because of usage of non-linear loads, can be eliminated by using control strategies designed for shunt active hybrid filters such as series and shunt converters. A conventional Proportional Integral (PI) and Fuzzy Logic Controllers are used for power quality enhancement by reducing the distortions in the output power. The simulation results are compared among the two control strategies, that fuzzy logic controller and pi controller.</p>

Medium and low voltage control strategies for a smart distribution grid

2016 ◽  
Author(s):  
Kamil Korotkiewicz ◽  
Philippe Steinbusch ◽  
Marcel Ludwig ◽  
Felix Dorsemagen ◽  
Marcus Stotzel ◽  
...  
Keyword(s):  
Low Voltage ◽  
Control Strategies ◽  
Voltage Control ◽  
Distribution Grid ◽  
Smart Distribution Grid

Control of Quasi-Z Source Inverter with Super Capacitor under Unbalanced Grid Fault Conditions

2013 ◽  
Vol 291-294 ◽  
pp. 2124-2131
Author(s):  
Feng Lin Li ◽  
Shu Ju Hu ◽  
Ling Ling Wang
Keyword(s):  
Reference Frames ◽  
Control Method ◽  
Low Voltage ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
Super Capacitor ◽  
Loop Control ◽  
Control Scheme ◽  
Unbalanced Grid ◽  
Generation Unit

The quasi-Z-source inverter (qZSI) has some unique advantages and is suitable for renewable energy sources such as solar and wind generation system. In order to make the inverter have the ride-through ability and the current into the grid symmetrical when unbalanced grid faults occur, the topology of qZSI with super capacitor substituting the low voltage capacitor and the unbalance control strategy were proposed. With a super capacitor the system can balance and smooth the power between the generation unit and grid, also the current injected into the grid can be symmetrical through the unbalance control method. The circuit of the new topology and the mathematical model of the three-phase converter under grid voltage unbalance conditions have been analyzed. And then, closed-loop control scheme for the proposed system is used to control the power flow of generation unit, grid and super capacitor in this system, also unbalance control strategies in positive (dq) + and negative (dq) – reference frames have been implemented in the grid-connected qZSI system to make the current into the grid symmetrical during the grid fault. The operating mode during unbalanced grid fault is simulated in MATLAB/Simulink, and the simulation results are presented to verify the theoretical analysis and the control scheme.

scholarly journals Effect of Individual Volt/var Control Strategies in LINK-Based Smart Grids with a High Photovoltaic Share

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5641
Author(s):  
Daniel-Leon Schultis ◽  
Albana Ilo
Keyword(s):  
Local Control ◽  
Smart Grids ◽  
Reactive Power ◽  
Low Voltage ◽  
Control Strategies ◽  
Load Flow ◽  
Electric Power System ◽  
Mobility Control ◽  
Holistic View ◽  
Voltage Limit

The increasing share of distributed energy resources aggravates voltage limit compliance within the electric power system. Nowadays, various inverter-based Volt/var control strategies, such as cosφ(P) and Q(U), for low voltage feeder connected L(U) local control and on-load tap changers in distribution substations are investigated to mitigate the voltage limit violations caused by the extensive integration of rooftop photovoltaics. This study extends the L(U) control strategy to X(U) to also cover the case of a significant load increase, e.g., related to e-mobility. Control ensembles, including the reactive power autarky of customer plants, are also considered. All Volt/var control strategies are compared by conducting load flow calculations in a test distribution grid. For the first time, they are embedded into the LINK-based Volt/var chain scheme to provide a holistic view of their behavior and to facilitate systematic analysis. Their effect is assessed by calculating the voltage limit distortion and reactive power flows at different Link-Grid boundaries, the corresponding active power losses, and the distribution transformer loadings. The results show that the control ensemble X(U) local control combined with reactive power self-sufficient customer plants performs better than the cosφ(P) and Q(U) local control strategies and the on-load tap changers in distribution substations.

scholarly journals Control Strategies of Full-Voltage to Half-Voltage Operation for LCC and Hybrid LCC/MMC based UHVDC Systems

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 742 ◽  
Author(s):  
Gen Li ◽  
Wei Liu ◽  
Tibin Joseph ◽  
Jun Liang ◽  
Ting An ◽  
...  
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Control Strategies ◽  
Control Process ◽  
Voltage Control ◽  
Load Shedding ◽  
Long Distance ◽  
High Voltage Direct Current ◽  
Bulk Power ◽  
The Time Domain

With the increasing demand of transmitting bulk-power over long-distance, the ultra high-voltage direct-current (UHVDC) transmission systems become an attractive option. Nowadays, not only the line commutated converter (LCC) based systems, but also the modular multilevel converter (MMC) based systems have reached UHVDC levels. The converter stations of UHVDC systems normally utilize two series-connected valve-groups to reduce the difficulties of device manufacturing and transportation. This high-voltage and low-voltage valve-group configuration allows the UHVDC systems to achieve a full-voltage to half-voltage operation which increases the flexibility of the systems. However, the existing research only focuses on the full-voltage to half-voltage control of LCC-UHVDC systems. The control strategies for hybrid LCC/MMC UHVDC systems are underresearched. Moreover, the approaches to reduce the load-shedding caused by the full-voltage to half-voltage control for both LCC and hybrid LCC/MMC based UHVDC systems have not been investigated. In this paper, full-voltage to half-voltage control strategies for both LCC and hybrid LCC/MMC based UHVDC systems have been proposed. Moreover, to avoid load-shedding caused by the half-voltage operation, a power rescheduling method that re-sets the power references of the half-voltage operating and full-voltage operating poles has been proposed. The proposed full-voltage to half-voltage control strategies and power rescheduling method can achieve a stable and fast control process with a minimum power loss. The proposed methods have been verified through the time-domain simulations conducted in PSCAD/EMTDC.

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