scholarly journals Effectiveness of Distributed vs. Concentrated Volt/Var Local Control Strategies in Low-Voltage Grids

2018 ◽  
Vol 8 (8) ◽  
pp. 1382 ◽  
Author(s):  
Albana Ilo ◽  
Daniel-Leon Schultis ◽  
Christian Schirmer
Keyword(s):  
Local Control ◽  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Control Strategies ◽  
Distribution Transformer ◽  
Medium Voltage ◽  
Power Exchange ◽  
Voltage Limit ◽  
The Impact

This paper introduces a novel local Volt/var control strategy in a low-voltage smart grid. Nowadays, various Volt/var local control strategies built on customer photovoltaic inverters, e.g., cosφ(P) and Q(U), are introduced to mitigate the upper voltage limit violations in feeders with high prosumer share. Nevertheless, although these strategies are further refined by including more local variables, their use is still very limited. In this study, the effects of a new concentrated Volt/var local control strategy in low-voltage grids are investigated. Concentrated var-sinks, e.g., coils-L(U), are set at the end of each violated feeder. The concentrated local control strategy L(U) is compared with the distributed cosφ(P) and Q(U) strategies. Initially, both control strategies are theoretically investigated, followed by simulations in a test feeder. Finally, the expected practical significance of the findings is verified through simulations in a real typical urban and rural grid. Additionally, the impact of the different local control strategies used in low-voltage grids on the behavior of the medium-voltage grid is analyzed. The results show that the concentrated Volt/var control strategy eliminates the violation of upper voltage limit even in longer feeders, where both distributed local strategies fail. In addition, the concentrated L(U) local control causes less reactive power exchange on the distribution transformer level than the distributed cosφ(P) and Q(U) strategies. Therefore, the reactive power exchange with the medium-voltage grid and thus the distribution transformer loading are smaller in the case of concentrated local control strategy.

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 A Comparative Study of the Voltage Sag Propagation under Un-Symmetrical Faults through Distribution Transformer on Low Voltage Power Network

2021 ◽  
Vol 19 (1) ◽  
pp. 90-94
Author(s):  
Abdul K. Junejo ◽  
Muhammad U. Keerio ◽  
Mohsin A. Koondhar ◽  
Munawar A. Memon ◽  
Muhammad I. Jamali ◽  
...  
Keyword(s):  
Control Strategy ◽  
Low Voltage ◽  
Power Transformers ◽  
Voltage Sag ◽  
Power Network ◽  
Distribution Transformer ◽  
Sequence Components ◽  
The Impact ◽  
Symmetrical Sequence

In this paper, the characterization of the voltage sag propagation under unsymmetrical faults through distribution transformer for low voltage power network is tested with the help of a power analyzer, which is based on sequence components. The voltage sag is a big issue of the power quality (PQ) for the power system networks, which must be analyzed and characterized for the suitable protection schemes and the control strategy, separately. In this study, the voltage sag characterization is fully examined under the unsymmetrical faults through the delta-star with ground (D-Yg) connection, which is commonly imlemented in the distribution power transformers. The MATLAB/Simulink and power analyzer tools are used to characterize the voltage sag propagation. The power analyzer works on the symmetrical sequence component’s method of the voltage. Moreover, the phasor diagram of the voltage sag is also given in this paper for better understanding. The obtained results would help in the design of the protection schemes for low-voltage and controlling the impact of voltage sag through filters.

A Improved LVRT Control Strategy Based on Active and Reactive Power for Direct-Drive PMSG Wind Generation System

2013 ◽  
Vol 732-733 ◽  
pp. 1184-1187
Author(s):  
Guo Liang Yang ◽  
Shuo Yang Liu ◽  
Xin Yan Chang ◽  
En Bei Zhang
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Control Strategies ◽  
Synchronous Generator ◽  
Direct Drive ◽  
Pwm Inverter ◽  
Low Voltage Ride Through ◽  
Active And Reactive Power ◽  
Grid Side

The structure of the uncontrolled rectifier + Boost circuit + PWM inverter is taken for direct-drive permanent magnet synchronous generator (PMSG) wind-power system. on the basis of the analysis for two different traditional control strategies for the grid side converter, a new control strategy Based on active and reactive power for the low voltage ride through running is proposed and described in detail. The simulation results verify that the given control strategy can be better to provide a reliable guarantee for the system low voltage ride through capability and to provide some reference for the actual control system design.

scholarly journals Using Energy Storage Inverters of Prosumer Installations for Voltage Control in Low-Voltage Distribution Networks

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1121
Author(s):  
Rozmysław Mieński ◽  
Przemysław Urbanek ◽  
Irena Wasiak
Keyword(s):  
Energy Storage ◽  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Storage System ◽  
Distribution Networks ◽  
Energy Storage System ◽  
Voltage Regulation ◽  
Active Power ◽  
Total Power

The paper includes the analysis of the operation of low-voltage prosumer installation consisting of receivers and electricity sources and equipped with a 3-phase energy storage system. The aim of the storage application is the management of active power within the installation to decrease the total power exchanged with the supplying network and thus reduce energy costs borne by the prosumer. A solution for the effective implementation of the storage system is presented. Apart from the active power management performed according to the prosumer’s needs, the storage inverter provides the ancillary service of voltage regulation in the network according to the requirements of the network operator. A control strategy involving algorithms for voltage regulation without prejudice to the prosumer’s interest is described in the paper. Reactive power is used first as a control signal and if the required voltage effect cannot be reached, then the active power in the controlled phase is additionally changed and the Energy Storage System (ESS) loading is redistributed in phases in such a way that the total active power set by the prosumer program remains unchanged. The efficiency of the control strategy was tested by means of a simulation model in the PSCAD/EMTDC program. The results of the simulations are presented.

DC-Link Voltage Balancing Strategy Based on SVM and Reactive Power Exchange for a 5L-MPC Back-to-Back Converter for Medium-Voltage Drives

2016 ◽  
Vol 63 (12) ◽  
pp. 7864-7875 ◽  
Author(s):  
Mikel Mazuela ◽  
Igor Baraia ◽  
Alain Sanchez-Ruiz ◽  
Ivan Echeverria ◽  
Inigo Torre ◽  
...  
Keyword(s):  
Reactive Power ◽  
Voltage Balancing ◽  
Medium Voltage ◽  
Power Exchange

The reactive power voltage control strategy of PV systems in low-voltage string lines

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xiaolong Guo ◽  
Xiqiang Chang ◽  
Guowei Fan ◽  
Lianger Chen ◽  
...  
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Voltage Control ◽  
Voltage Control Strategy ◽  
Pv Systems

scholarly journals A Novel Hierarchical Control Strategy for Low-Voltage Islanded Microgrids Based on the Concept of Cyber Physical System

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1835 ◽  
Author(s):  
Qiuxia Yang ◽  
Dongmei Yuan ◽  
Xiaoqiang Guo ◽  
Bo Zhang ◽  
Cheng Zhi
Keyword(s):  
Control Strategy ◽  
Physical System ◽  
Reactive Power ◽  
Low Voltage ◽  
Hierarchical Control ◽  
Physical Layer ◽  
Cyber Physical System ◽  
Droop Control ◽  
Control Effect ◽  
Consensus Control

Based on the concept of cyber physical system (CPS), a novel hierarchical control strategy for islanded microgrids is proposed in this paper. The control structure consists of physical and cyber layers. It’s used to improve the control effect on the output voltages and frequency by droop control of distributed energy resources (DERs), share the reactive power among DERs more reasonably and solve the problem of circumfluence in microgrids. The specific designs are as follows: to improve the control effect on voltages and frequency of DERs, an event-trigger mechanism is designed in the physical layer. When the trigger conditions in the mechanism aren’t met, only the droop control (i.e., primary control) is used in the controlled system. Otherwise, a virtual leader-following consensus control method is used in the cyber layer to accomplish the secondary control on DERs; to share the reactive power reasonably, a method of double virtual impedance is designed in the physical layer to adjust the output reactive power of DERs; to suppress circumfluence, a method combined with consensus control without leader and sliding mode control (SMC) is used in the cyber layer. Finally, the effectiveness of the proposed hierarchical control strategy is confirmed by simulation results.

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 Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3865 ◽  
Author(s):  
Daniel-Leon Schultis ◽  
Albana Ilo
Keyword(s):  
Power Flow ◽  
Large Scale ◽  
Reactive Power ◽  
Low Voltage ◽  
Information And Communications Technology ◽  
Optimal Arrangement ◽  
Reactive Power Flow ◽  
Voltage Limit ◽  
Scale Integration ◽  
Distribution Grids

The large-scale integration of rooftop PVs stalls due to the voltage limit violations they provoke, the uncontrolled reactive power flow in the superordinate grids and the information and communications technology (ICT) related challenges that arise in solving the voltage limit violation problem. This paper attempts to solve these issues using the LINK-based holistic architecture, which takes into account the behaviour of the entire power system, including customer plants. It focuses on the analysis of the behaviour of distribution grids with the highest PV share, leading to the determination of the structure of the Volt/var control chain. The voltage limit violations in low voltage grid and the ICT challenge are solved by using concentrated reactive devices at the end of low voltage feeders. Q-Autarkic customer plants relieve grids from the load-related reactive power. The optimal arrangement of the compensation devices is determined by a series of simulations. They are conducted in a common model of medium and low voltage grids. Results show that the best performance is achieved by placing compensation devices at the secondary side of the supplying transformer. The Volt/var control chain consists of two Volt/var secondary controls; one at medium voltage level (which also controls the TSO-DSO reactive power exchange), the other at the customer plant level.

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.

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