scholarly journals Control Strategy to Regulate Voltage and Share Reactive Power Using Variable Virtual Impedance for a Microgrid

2019 ◽  
Vol 9 (22) ◽  
pp. 4876 ◽  
Author(s):  
Eder Molina ◽  
John E. Candelo-Becerra ◽  
Fredy E. Hoyos
Keyword(s):  
Power Control ◽  
Electric Vehicles ◽  
Control Strategy ◽  
Reactive Power ◽  
Control Variable ◽  
Control Voltage ◽  
Primary Control ◽  
Distributed Generator ◽  
Distributed Generators ◽  
Virtual Impedance

This paper presents a control strategy to regulate voltage and share reactive power from distributed generators in a microgrid when electric vehicles (EVs) are connected and disconnected at different nodes and times. The control strategy considers fixed and variable virtual impedances created in the microgrid (MG) when loads change (EVs are connected or disconnected). Fixed virtual impedance is related to the distance from each house to the power inverter and is used as an input of the primary control. Variable virtual impedance is associated with the distance from each EV to the power inverter and is also used as an input of the primary control. Thus, the control of the inverter seeks to regulate the voltage where the EVs create variations in the network. The results show that the control strategy regulates well the voltage of different nodes, and the reactive power is distributed to renewable generators based on the distance from the loads to the inverters. By considering the fixed and variable virtual impedances in the primary control, voltage can be regulated, assuming various consumptions of EVs in the network. This result is promising for reactive power control and sharing for each distributed generator (DG) in a microgrid where a great number of EVs affect the operation.

scholarly journals Precise Reactive Power-Voltage Droop Control of Parallel Virtual Synchronous Generators that Considers Line Impedance

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1344
Author(s):  
Xiangwu Yan ◽  
Hongbin Ma ◽  
Jiaoxin Jia ◽  
Waseem Aslam ◽  
Chenguang Wang ◽  
...  
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Integrated Control ◽  
Synchronous Generator ◽  
Control Voltage ◽  
Droop Control ◽  
Parallel Operation ◽  
Distributed Generators ◽  
Power Decoupling ◽  
Virtual Synchronous Generator

Problems such as high power coupling, low distribution accuracy, and insufficient reactive power-voltage droop accuracy occur when distributed generators are operated in parallel due to the influence of line impedance. The precise control of output reactive power and voltage is difficult to achieve using traditional virtual synchronous generator (VSG) control. Taking this into consideration, this study proposes a virtual synchronous generator reactive power-voltage integrated control strategy that considers line parameters to solve this problem. First, the impedance voltage drop of the line is compensated for in accordance with local information control to ensure the consistency of the control voltage in parallel operation of distributed generators and to realize the precise droop control of reactive power and the voltage of the point of common coupling (UPCC). Second, virtual negative impedance control is added to change the equivalent output impedance characteristics of the system and achieve power decoupling. On this basis, the active frequency and reactive voltage decoupling control effect of the improved control strategy is quantified and analyzed using the relative gain matrix. The accuracy of reactive power distribution and droop control is theoretically derived and analyzed by establishing a small-signal model of a two-machine parallel system. Finally, the accuracy and effectiveness of the proposed integrated control strategy are verified via a simulation model and an experimental platform for parallel operation. Results show that the proposed integrated control strategy can effectively solve the problems of power decoupling and accurate distribution, reduce system loop current, and realize accurate reactive power-voltage droop. Compared with the traditional VSG control strategy, the dynamic deviation of UPCC is reduced by at least 40% when a large-scale load disturbance occurs.

scholarly journals Reactive power sharing in microgrid using virtual voltage

2021 ◽  
Vol 11 (4) ◽  
pp. 2743
Author(s):  
Eder A. Molina-Viloria ◽  
John E. Candelo Becerra ◽  
Fredy E. Hoyos Velasco
Keyword(s):  
Power Control ◽  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Active Power ◽  
Power Sharing ◽  
Droop Control ◽  
Matlab Simulink ◽  
Distributed Generators ◽  
Additional Coefficient

The traditional droop control strategy has been applied previously in microgrids (MGs) to share accurately the active power. However, in some cases the result obtained when sharing reactive power is not the best, because of the parameters related to the distances from distributed generators (DGs) to the loads and the power variations. Therefore, this paper proposes a reactive power control strategy for a low voltage MG, where the unequal impedance related to the distances between generators and loads requires adjustments to work with the conventional frequency and voltage droop methods. Thus, an additional coefficient is calculated from parameters of the network that relate the location of elements. The test is perfomed by simulations in the MATLAB-Simulink software, considering a three-node MG with three DGs and a load that can change power at different periods of time. The results show that it is possible to improve reactive power sharing between the DGs located in the MG according to the load changes simulated and to improve voltages with this method.

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