Amount Of Reactive Power Compensation Research Articles

Volt-Var Control for Utility-Scale Solar PV Plants to Downsize SVCs and Curtailment Effects

One way to increase solar photovoltaic penetration in the grid is the management of voltage fluctuations. This is because a photovoltaic plant cannot be interconnected to the grid if it causes voltage violations. Voltage violation is where voltage exceeds the acceptable range. Often, grid operators request photovoltaic plant owners to regulate voltage sufficiently with expensive and space-consuming static Var compensators. Unfortunately, this sometimes makes the project less feasible. This paper argues that there are better ways to regulate voltage. It also asserts that these ways must be sought before blindly procuring a static Var compensator or seeking battery storage. We simulated with a 70-MW photovoltaic plant as an addition to the grid. Without voltage regulation, voltage violations in Spring were found to be particularly significant. However, the proposed reactive power compensation removed all voltage violations smartly. Furthermore, the study results demonstrated that the operator-induced curtailment effectively reduced the necessary amount of reactive power compensation, leading to a smaller size of SVC, as it occurred specifically at certain overvoltage points. This paper argues that the economic and spatial efficiency of reactive power compensation devices is key to increasing photovoltaic penetration. It argues that one-sided bearing of the cost of reactive compensation devices is inefficient.

Network partition-based hierarchical decentralised voltage control for distribution networks with distributed PV systems

The integration of large-scale distributed photovoltaics (PVs) in distribution networks (DNs) causes reverse power flow and the voltage violation problem. However, in some rural area, DNs do not have sufficient measuring information and communication ability to meet the challenge. In order to solve the voltage violation problem, this study proposes a voltage profile perception method and a voltage regulation analysis model as an alternative method to power flow calculations to guide the partition and voltage control of DNs. We then propose a novel hierarchical decentralised voltage control method strategy that combines cluster autonomous optimisation and cluster coordination optimisation in different time scales based on the DN partition. The optimal control is conducted for voltage regulation to minimise the amount of reactive power compensation and the active power curtailment under the DN operation constraints. The effectiveness and feasibility of the proposed method are demonstrated via simulation tests on a real 10.5 kV 34-node feeder in China.

Network Partition-Based Zonal Voltage Control for Distribution Networks With Distributed PV Systems

As the penetration level of distributed photovoltaic (PV) systems keeps increasing in distribution networks, overvoltage due to reverse power flow is an urgent issue to be addressed. This paper proposes a voltage regulation method by utilizing the voltage control capability of PV inverters. A novel network partition approach based on a community detection algorithm is presented to realize zonal voltage control in a shorter control response time using the minimum amount of reactive power compensation and active power curtailment. An improved modularity index that considers local reactive power balance is introduced to partition a distribution network into several clusters/communities with PVs based on the node voltage sensitivity analysis. An optimal reactive and active power control strategy is proposed for voltage control in each cluster. The voltage management of the overall system can be achieved by controlling each cluster separately. The proposed approach is applied to the voltage control of a practical 10 kV, 37-node feeder. Case studies on the real distribution network and a modified IEEE 123-node system are carried out to verify the feasibility and effectiveness of the proposed method.

Hybrid Structure of Static Var Compensator and Hybrid Active Power Filter (SVC//HAPF) for Medium-Voltage Heavy Loads Compensation

In this paper, the structure, modeling, parameter design, and control method are proposed for a new hybrid structure of a static var compensator in parallel with a hybrid active power filter (SVC//HAPF). The SVC part of the SVC//HAPF is used to dynamically compensate the reactive power. And, the HAPF part is used to provide harmonic power and small amount of reactive power compensation. Due to the large fundamental voltage drop on coupling the LC part, the active inverter part of the SVC//HAPF has low voltage rating. Meanwhile, the parallel-connected SVC acts as a current divider to reduce the active inverter current. Therefore, the proposed SVC//HAPF shows the great promise in compensating harmonic current and wide-range reactive power with a low (both) voltage and current rating active inverter part. To show the advantages of the proposed SVC//HAPF, simulation comparisons among the active power filter (APF), HAPF, SVC in series with HAPF (SVC−HAPF), and the proposed SVC//HAPF are provided. Finally, experimental results based on the laboratory-scaled hardware prototype are given to show the validity of the SVC//HAPF.

A Dynamic Reactive Power Compensation Method of Super High-Power and High-Voltage Motor

According to the low power factor and low running efficiency, a dynamic reactive power compensation method of the super high-power and high-voltage motor is proposed in this paper. The following works have been done in the study: topology of the dynamic reactive power compensation device; principle of the dynamic reactive power compensation method; control system of the dynamic reactive power compensation device; implementation of the dynamic reactive power compensation method. The amount of reactive power compensation can be adjusted smoothly and dynamically in the process of the super high-power and high-voltage motor soft-starting. The research of this paper has laid a theoretical foundation for this compensator in industrial applications. The novel design is characterized by flexible parameter setting, excellent soft starting performance of the super high-power and high-voltage motor and bright prospect in application.

Capacitor Voltage Balancing of Three-Phase Neutral-Point-Clamped Rectifier Using Modified Reference Vector

This paper presents a control strategy using optimized switching sequences which results in capacitor voltage balancing of a three-phase neutral-point-clamped rectifier. In front end rectifiers, magnitude and lag angle of reference current vector (w.r.t supply voltage vector) varies depending upon amount of reactive power compensation and load current. Accordingly, the effectiveness of small and medium vectors (using SVPWM) for same switching state varies in each sector and its regions. This observation along with detailed analysis of current pattern for both the capacitors and their effect on neutral point voltage forms the basis of the proposed approach, which is to modify the reference vector for changing the number of sampling periods within each sector and its regions. The rectifier exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum possible switching losses, reduced-rippled, and well-regulated dc-bus voltage, particularly, the capacitor voltage balancing. The proposed control algorithm is tested through exhaustive simulations and validated through experimental results obtained from a laboratory prototype of the rectifier.

Capacitor voltage balancing of a three‐phase neutral‐point clamped bi‐directional rectifier using optimised switching sequences

In this study, a modulation strategy is presented using minimum number of switching transitions of optimised switching sequences for balancing of DC-bus capacitor voltages of a three-phase neutral-point clamped bi-directional converter. This new approach is derived from the fact that in front end AC–DC converters, the location of supply voltage vector and reference current vector (magnitude and lag angle) vary depending upon the amount of reactive power compensation and the load current to be supplied by converter. Accordingly, the effect of small and medium vectors (using space vector pulse-width modulation) for same switching state varies in each sector and its regions resulting in DC-bus capacitor voltage unbalancing. This observation along with the detailed analysis of current pattern for both the capacitors within each sector and its regions and its effect on neutral-point voltage deviation forms the basis of proposed approach of maintaining optimised space vector sequences and changing the number of sampling periods within each sector and its regions, thus resulting in DC-bus capacitor voltage balancing. As a result, modified reference current vector spends different amount of time in alternate sectors (moves faster and slower in alternate sectors) but total time for one complete cycle is same as actual current vector. The converter exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum switching losses, reduced ripple factor of the regulated DC output voltage and particularly, the neutral-point voltage deviation under dynamic load conditions both for rectification and inversion modes of operation.

Fast control strategy for stabilising fixed‐speed induction‐generator‐based wind turbines in an islanded distributed system

Distributed generation systems (DGS) with fixed-speed induction-generator-based wind turbines (FSWT) are sensitive and vulnerable to voltage disturbances and reactive power deficiency. Consequently, the control and protection strategies for such a DGS should be prompt and precise to avoid undesired wind generator cutting off. This study investigates and analyses the dynamic characteristics of an FSWT to reveal the behaviours of an FSWT under disturbances. Then a fast control strategy for stabilising an islanded DGS is proposed. The main contributions of the control strategy are: the total amount of reactive power compensation and load shedding may be determined precisely; all the operation execution points may be decided accurately to improve DGS stability. Furthermore, the implementation of the fast control strategy is also discussed. A case study is presented to demonstrate the effectiveness of the proposed method.

An autonomous decentralized voltage control scheme in PEV charging devices on the distribution network- reactive power compensation for voltage decreases caused by household loads and charging devices

SUMMARY Plug-in electric vehicles (PEVs) will spread as environmental awareness continues to grow. As a result, many PEV batteries are likely to be charged in residential areas overnight, but this will cause a significant voltage decrease in the distribution network. As a countermeasure that does not require capital investment to strengthen the network, this paper proposes an autonomous decentralized voltage control scheme using a PEV battery charger. The scheme can continuously estimate household loads consumption and calculate the reactive power required for compensating the voltage decreases caused by household load consumption and PEV charging. Because only the measured voltage and current at the connecting point of the PEV battery and the impedance between this point and the nearest distributing substation are required to calculate the necessary amount of reactive power compensation, the control scheme can be implemented merely by modifying the control logic circuit built into the PEV battery charger at almost no extra cost. A realistic model of the distribution network and the standard daily demand curve in residential areas in Japan are used to validate the performance of the new scheme. Copyright © 2012 John Wiley & Sons, Ltd.

ANN Based DSPIC Controller for Reactive Power Compensation

In India with a power shortage of about 10% of installed capacity, the transmission and distribution losses are relatively high. One of the reasons for the large loss is the excessive reactive loads on the primary distribution feeder. With the right amount of reactive power compensation, as system load varies, line losses can be considerably reduced. The application of Artificial Neural Network (ANN) is an emerging area where a properly trained ANN can be advantageously used for sufficient amount of reactive power compensation under varying load conditions. This paper describes the methodology adopted for training an ANN network for reactive power compensation without human intervention. The ANN is implemented using a DSPIC 30F2010 (Digital Signal Peripheral Interface Controller) and verified on a simulated laboratory network . The results obtained are satisfactory.

On-line reactive power compensation schemes for unbalanced three phase four wire distribution feeders

A new reactive power compensation method is developed to reduce the negative and zero sequence components of load currents and to improve the load bus power factor of unbalanced three-phase four-wire distribution feeders. Negative and zero sequence currents may cause additional losses and damage to power systems. Load compensation at the load bus is an effective method to eliminate those undesired sequence currents. The compensation technique uses a Y-connected and a Delta -connected static reactive power compensators (SVCs) to give a different amount of reactive power compensation to each phase. The compensation formulas are very suitable for on-line control by measurement of phase voltages and currents in real time. The compensation effect can also be achieved even if one leg of the SVCs is out of service. In addition to balancing effect and power factor improvement at the load bus, the SVCs can also be used to support the load bus voltage and to maintain the substation feeder at unity power factor. Digital simulations are made with the load data measured from an 11.4 kV secondary substation feeder.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>