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.

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 Full-Observable Three-Phase State Estimation Algorithm Applied to Electric Distribution Grids

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1327 ◽  
Author(s):  
Thiago Soares ◽  
Ubiratan Bezerra ◽  
Maria Tostes
Keyword(s):  
State Estimation ◽  
Real Time ◽  
Distribution Systems ◽  
Phase State ◽  
Reactive Power ◽  
Estimation Algorithm ◽  
Load Flow ◽  
Electrical Network ◽  
The Real ◽  
Three Phase

This paper proposes the development of a three-phase state estimation algorithm, which ensures complete observability for the electric network and a low investment cost for application in typical electric power distribution systems, which usually exhibit low levels of supervision facilities and measurement redundancy. Using the customers´ energy bills to calculate average demands, a three-phase load flow algorithm is run to generate pseudo-measurements of voltage magnitudes, active and reactive power injections, as well as current injections which are used to ensure the electrical network is full-observable, even with measurements available at only one point, the substation-feeder coupling point. The estimation process begins with a load flow solution for the customers´ average demand and uses an adjustment mechanism to track the real-time operating state to calculate the pseudo-measurements successively. Besides estimating the real-time operation state the proposed methodology also generates nontechnical losses estimation for each operation state. The effectiveness of the state estimation procedure is demonstrated by simulation results obtained for the IEEE 13-bus test network and for a real urban feeder.

scholarly journals Voltage Support Experimental Analysis of a Low-Voltage Ride-Through Strategy Applied to Grid-Connected Distributed Inverters

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1949 ◽  
Author(s):  
Miguel Garnica ◽  
Luís García de Vicuña ◽  
Jaume Miret ◽  
Antonio Camacho ◽  
Ramón Guzmán
Keyword(s):  
Distributed Generation ◽  
Experimental Analysis ◽  
Reactive Power ◽  
Low Voltage ◽  
Control Strategies ◽  
Future Research ◽  
Low Voltage Ride Through ◽  
Distributed Power Generation ◽  
Object Of Study ◽  
Power Generation Systems

In recent decades, different control strategies have been designed for the increasing integration of distributed generation systems. These systems, most of them based on renewable energies, use electronic converters to exchange power with the grid. Capabilities such as low-voltage ride-through and reactive current injection have been experimentally explored and reported in many research papers with a single inverter; however, these capabilities have not been examined in depth in a scenario with multiple inverters connected to the grid. Only few simulation works that include certain methods of reactive power control to solve overvoltage issues in low voltage grids can be found in the literature. Therefore, the overall objective of the work presented in this paper is to provide an experimental analysis of a low-voltage ride-through strategy applied to distributed power generation systems to help support the grid during voltage sags. The amount of reactive power will depend on the capability of each inverter and the amount of generated active power. The obtained experimental results demonstrate that, depending on the configuration of distributed generation, diverse inverters could have different control strategies. In the same way, the discussion of these results shows that the present object of study is of great interest for future research.

Real and Reactive Power Transfer Allocation Utilizing Modified Nodal Equations

2008 ◽  
Vol 9 (6) ◽  
Author(s):  
Hussain Shareef ◽  
Mohd. Wazir Mustafa ◽  
Saifulnizam Abd Khalid ◽  
Azhar Khairuddin ◽  
Akhtar Kalam ◽  
...  
Keyword(s):  
Reactive Power ◽  
Load Flow ◽  
New Method ◽  
Power Transfer ◽  
Load Voltage ◽  
The Real ◽  
Admittance Matrix ◽  
Dependent Term ◽  
Voltage Dependent ◽  
Bus System

This paper proposes a new method to identify the real and reactive power transfer between generators and load using modified nodal equations. Based on available load flow results, the method partitions the Y-bus matrix to decompose the current of the load buses as a function of the generators' current and load voltages. Then, it uses the modified admittance matrix to decompose the load voltage-dependent term into components of generator dependent terms. By using these two decompositions of current and voltage terms, the real and reactive power transfer between loads and generators are obtained. The effectiveness of the proposed method is demonstrated by using a simple 5-bus system and the modified IEEE 30-bus system. The proposed methodology provides reasonable and acceptable results to real and reactive power transfer allocation.

scholarly journals Mitigation of overvoltage due to high penetration of solar photovoltaics using smart inverters volt/var control

2020 ◽  
Vol 19 (3) ◽  
pp. 1259
Author(s):  
Dilini Almeida ◽  
Jagadeesh Pasupuleti ◽  
Janaka Ekanayake ◽  
Eshan Karunarathne
Keyword(s):  
Reactive Power ◽  
Low Voltage ◽  
Distribution Networks ◽  
Solar Photovoltaics ◽  
Pv Inverter ◽  
High Penetration ◽  
Smart Control ◽  
Power Capability ◽  
Pv Penetration ◽  
Smart Inverters

The modern photovoltaic (PV) inverters are embedded with smart control capabilities such as Volt/Var and Volt/Watt functions to mitigate overvoltage issues. The Volt/Var control has gained a significant attention in regulating grid voltage through reactive power compensation. However, the reactive power capability of a PV inverter is limited during peak irradiance and could be improved by curtailing the active power generation and by oversizing the PV inverter. This paper analyzes the performance of Volt/Var function of smart PV inverters in mitigating overvoltage issues due to high PV integration and thus increasing the hosting capacity of low voltage distribution networks (LVDNs). The study is conducted on a real Malaysian LVDN considering two different Volt/Var set points under different PV penetration levels. Results demonstrate that the oversized smart PV inverter could enhance the Volt/Var functionality by increasing its reactive power capability than a typical smart PV inverter. Further it reveals that adaptation of sensitive Volt/Var set points with shorter deadbands increase the PV hosting capacity of LVDNs.

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.

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