scholarly journals Reactive Power Compensation and Imbalance Suppression by Star-Connected Buck-Type D-CAP

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1914 ◽  
Author(s):  
Xiaosheng Wang ◽  
Ke Dai ◽  
Xinwen Chen ◽  
Xin Zhang ◽  
Qi Wu ◽  
...  
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Reactive Power Compensation ◽  
Positive Sequence ◽  
Negative Sequence ◽  
Type D ◽  
Load Imbalance ◽  
Three Phase ◽  
Unbalanced Load ◽  
Line Loss

Reactive power and negative-sequence current generated by inductive unbalanced load will not only increase line loss, but also cause the malfunction of relay protection devices triggered by a negative-sequence component in the power grid, which threatens the safe operation of the power system, so it is particularly important to compensate reactive power and suppress load imbalance. In this paper, reactive power compensation and imbalance suppression by a three-phase star-connected Buck-type dynamic capacitor (D-CAP) under an inductive unbalanced load are studied. Firstly, the relationship between power factor correction and imbalance suppression in a three-phase three-wire system is discussed, and the principle of D-CAP suppressing load imbalance is analyzed. Next, its compensation ability for negative-sequence currents is determined, which contains theoretical and actual compensation ability. Then an improved control strategy to compensate reactive power and suppress imbalance is proposed. If the load is slightly unbalanced, the D-CAP can completely compensate the reactive power and negative-sequence currents. If the load is heavily unbalanced, the D-CAP can only compensate the positive-sequence reactive power and a part of the negative-sequence currents due to the limit of compensation ability. Finally, a 33 kVar/220 V D-CAP prototype is built and experimental results verify the theoretical analysis and control strategy.

scholarly journals Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network

2019 ◽  
Vol 10 (1) ◽  
pp. 113 ◽  
Author(s):  
Pedro A. Blasco ◽  
Rafael Montoya-Mira ◽  
José M. Diez ◽  
Rafael Montoya ◽  
Miguel J. Reig
Keyword(s):  
Linear Systems ◽  
Reactive Power ◽  
Current System ◽  
Positive Sequence ◽  
Power Network ◽  
Negative Sequence ◽  
Three Phase ◽  
Network Losses ◽  
Infinite Power

The compensation of an electrical system from passive compensators mainly focuses on linear systems where the consumption of charges does not vary significantly over time. In three-phase three-wire systems, when the network voltages are unbalanced, negative-sequence voltages and currents appear, which can significantly increase the total apparent power supplied by the network. This also increases the network losses. This paper presents a method for calculating the compensation of the positive-sequence reactive power and unbalanced powers caused by the negative-sequence line currents using reactive elements (coils and/or capacitors). The compensation is applied to three-phase three-wire linear systems with unbalanced voltages and loads, which are connected to an infinite power network. The method is independent of the load characteristics, where only the line-to-line voltages and line currents, at the point where compensation is desired, need to be known in advance. The solution obtained is optimal, and the system observed from the network behaves as one that only consumes the active power required by a load with a fully balanced current system. To understand the proposed method and demonstrate its validity, a case study of a three-phase three-wire linear system connected to an infinite power network with unbalanced voltages and currents is conducted.

scholarly journals Increase of Reactive Power Compensation Efficiency on the Basis of Individual Phase Compensation Devices

2019 ◽  
pp. 1-11
Author(s):  
Sergey V. Kuzmin ◽  
Artem A. Zavalov ◽  
Roman S. Kuzmin ◽  
Vitalii A. Menshikov
Keyword(s):  
Power Supply ◽  
Thermal Destruction ◽  
Reactive Power ◽  
Reactive Power Compensation ◽  
Phase Compensation ◽  
Individual Phase ◽  
Three Phase ◽  
Unbalanced Load ◽  
Emergency Mode ◽  
Independent Individual

The purpose of this article is to establish an effective method for compensating reactive power in four-wire networks voltage up to 1000 V with a solidly grounded neutral. The method and the device for independent individual phase reactive power compensation are presented. The known devices and methods for symmetric reactive power compensation in three-phase four-wire networks are ineffective. Under certain circumstances, probability of emergency mode increases. Asymmetrical and unbalanced load on network phases dominate in three-phase four-wire networks. As a result, current in the neutral wire increases several times. This can lead to thermal destruction of the neutral wire and failure of power supply cable. By reducing load unbalance in network phases and eliminating effects of undercompensation and overcompensation, the method of independent individual phase reactive power compensation makes it possible to reduce the current in the neutral. The method of independent individual phase compensation is preferred when using devices reactive power compensation in three-phase networks with solidly grounded neutral. This method allows to increase transfer capacity, to reduce losses, and also reduces chance of emergency mode. Results of introduction of devices for individual phase reactive power compensation into operation prove the efficiency of the proposed method

Modified Power Compensation Control Strategy of Three-Phase Grid-Connected Inverter under Unbalanced Grid Voltage Conditions

2015 ◽  
Vol 740 ◽  
pp. 335-338 ◽  
Author(s):  
Shao Hua Sun ◽  
Hong Qi Ben
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Positive Sequence ◽  
Grid Voltage ◽  
Compensation Control ◽  
Active And Reactive Power ◽  
Three Phase ◽  
Grid Connected Inverter ◽  
Three Phase Inverter ◽  
Unbalanced Grid

Control strategy under unbalanced grid voltage conditions is one of the most important issues for grid-connected inverter. Under unbalanced grid voltage conditions, the 2nd active and reactive power ripples generate, they pollute the grid. To meet the demands of IEEE Std.929-2000, this paper proposed a modified power compensation control strategy; the proposed solution is based on direct power control. To provide accurate compensating power, the power model of three-phase inverter under unbalanced grid voltage conditions is given, using the positive sequence current component and the negative sequence voltage component, the compensating powers are calculated in details. Theoretical analysis and comparative simulation verification are presented to demonstrate the effectiveness of the proposed control strategy.

scholarly journals Decoupled Control of Three Phase Grid Connected Solar PV System

2019 ◽  
Vol 9 (2) ◽  
pp. 4218-4222
Keyword(s):  
Solar Energy ◽  
Power Factor ◽  
Control Strategy ◽  
Reactive Power ◽  
Standard Test ◽  
Effective Control ◽  
Solar Pv ◽  
Pv System ◽  
Three Phase ◽  
Decoupled Control

A reliable grid connected Photovoltaic (PV) system require effective control schemes for efficient use of solar energy. This paper presents a three-phase grid tied PV system with decoupled real and reactive power control to achieve desired power factor with Maximum Power Point Tracking (MPPT) controller to get maximum solar energy. The synchronous reference frame (dq) control along with decoupling concept is used to control the DC-AC inverter output, while the Phase Locked Loop (PLL) synchronization technique is used to monitor and synchronize the voltage and current at the grid side. The DC-DC converter with Incremental Conductance (InC) based MPPT model is also designed in this paper due to better accuracy compared to Perturb & Observe (P&O) algorithm. The simulation is performed in MATLAB/SIMULINK and a 31.5 kW PV system is modelled to get 30 kW power with the help of MPPT at Standard Test Conditions (STC). Any power factor value between 0.85 lagging to 0.9 leading can be obtained by changingreference q current in this inverter control strategy. The simulation results show that the change of reactive powerdoes not affecttheactive power values of the system, which verifies the effectiveness of the decoupled control strategy of the inverter.

scholarly journals Three Phase Auto-tuned Shunt Hybrid Filter for Harmonic and Reactive Power Compensation

2015 ◽  
Vol 21 ◽  
pp. 482-489 ◽  
Author(s):  
M.R. Sindhu ◽  
Manjula G. Nair ◽  
T.N.P. Nambiar
Keyword(s):  
Reactive Power ◽  
Reactive Power Compensation ◽  
Hybrid Filter ◽  
Three Phase

A Novel Current Reference Calculation Method for Shunt Active Power Filter under Nonideal Mains Voltages

2012 ◽  
Vol 468-471 ◽  
pp. 245-251
Author(s):  
Shou Ming Liu ◽  
Hong Wei Shi ◽  
Qian Zhang ◽  
Zhi Kun Hu
Keyword(s):  
Calculation Method ◽  
Reactive Power ◽  
Active Power Filter ◽  
Reactive Power Compensation ◽  
Active Power ◽  
Positive Sequence ◽  
Shunt Active Power Filter ◽  
Power Filter ◽  
Current Reference ◽  
Iq Method

In this paper, the impuissance of traditional ip-iq method in reactive power compensation applications under nonideal mains voltages is illustrated first, and then a novel current reference calculation method for Shunt Active Power Filter (SAPF) based on p-q transformation is proposed. By means of the proposed method, the positive sequence fundamental active current component of the load current can be isolated under distorted and/or unbalanced mains voltages, which makes SAPF be capable of harmonic cancellation and reactive power compensation at the same time under nonideal mains voltages. The effectiveness of the new proposed method is mathematically studied and verified by computer simulation under ideal and nonideal mains voltages.

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