Simulation Analysis of Control System in an Innovative Magnetically-Saturated Controllable Reactor

Controllable saturation reactors are widely used in reactive power compensation. The control system of controllable saturation reactor determines adaption speed, accuracy, and stability. First, an innovative type of controllable saturation reactor is introduced. After that the control system is designed, and a self-tuning algorithm in PID controller is proposed in the paper. The algorithm tunes PID parameters automatically with different error signals caused by varied loads in power system. Then the feasibility of the above algorithm is verified by Simulink module of Matlab software. The results of simulation indicate that the control system can efficiently reduce adaption time and overshoot.

Effectiveness of Optimal Arrangement of the Residences Operated by Reactive Power Control for a Clustered Grid-Interconnected PV System

There is a danger of power generation efficiency decreasing due to voltage increase when clustered residential PV systems are grid-interconnected to a single distribution line. As a countermeasure, installation of the reactive power control of an inverter at each residence has been considered. However, there are not many types of inverters that can operate reactive power control because there are insufficient effects on a low voltage distribution line with low penetration PV with reactive power control. Therefore, it is necessary to consider how to increase generation efficiency with a lower number of inverters. In this paper, four Japanese standard distribution line structures, for example of a residential area on ＂C1＂, where 2,160 residential PV systems are grid-interconnected, are selected. The optimal setting of reactive power control at each residence is computed on the distribution lines with a greedy method.

Advanced Reactive Power Control at Individual Residences to Smooth Energy Loss Fluctuation for a Clustered Grid-Interconnected PV System

Reactive power control can control voltage within the proper range from the power network side or from the distribution generation （PV （photovoltaic）） side. Reactive power control from the power network side is simpler because little controlled object apparatus, such as STATCOM, is required. However, it is difficult to optimize the individual voltages of residential consumers because few data have been obtained by the power network side as compared with the power generation side. Energy loss at each residence with PV is different due to the difference in the grid-interconnection condition, such as distribution line impedance when the same operating voltage is set at all residences. Therefore, in this paper, the authors propose an advanced reactive power control method for residential PV systems in order to optimally control the voltage at individual residences so as to minimize energy loss fluctuation. The effectiveness of the proposed reactive power control is demonstrated by numerical simulation.

Neuro-Fuzzy Based Interline Power Flow Controller for Real Time Power Flow Control in Multiline Power System

This article investigates the power quality enhancement in power system using one of the most famous series converter based FACTS controller like IPFC (Interline Power Flow Controller) in Power Injection Model (PIM). The parameters of PIM are derived with help of the Newton-Raphson power flow algorithm. In general, a sample test power system without FACTs devices has generated more reactive power, decreased real power, more harmonics, small power factor and poor dynamic performance under line and load variations. In order to improve the real power, compensating the reactive power, proficient power factor and excellent load voltage regulation in the sample test power system, an IPFC is designed. The D-Q technique is utilized here to derive the reference current of the converter and its D.C link capacitor voltage is regulated. Also, the reference voltage of the inverter is arrived by park transformation technique and its load voltage is controlled. Here, a sample 230 KV test power system is taken for study. Further as the conventional PI controllers are designed at one nominal operating point they are not competent to respond satisfactorily in dynamic operating conditions. This can be circumvented by a Fuzzy and Neural network based IPFC and its detailed Simulink model is developed using MATLAB and the overall performance analysis is carried out under different operating state of affairs.

Design to conditioning circuits of dynamic compensation of reactive power in the intelligence voltage controller

The paper introduces one design idea that making use of SCM to control Real-timely the dynamic compensation of reactive power.Firstly,design one Circuit to Sample the voltage and current,and by these datas we can easily calculate the power factor,and Voltage controller in the microcontroller to determine whether input the compensation capacitance according to the size of power factor,the paper also analyzes the principle of capacitance compensation and calculation method. Dynamic compensation for the entire process is quick and accurate.

Fuzzy Decision Method Applied in Action of Reactive Power Compensation Devices in Wind System

Frequent occurrence of large-scale cascading trip-off of wind turbine raises the concern about the decision process of ordered control of reactive power compensation devices. The theory of fuzzy multi-attribute decision making is adopted to ascertain the action sequence of reactive power compensation devices. First, a set of evaluation indexes including control sensitivity, regulation margin, response time, response level and cost is set up, and fuzziness of the proposed qualitative indexes is introduced to make them comparable to the proposed quantitative indexes. Then a method to calculate fuzzy weight of each index is put forward for evaluating relative importance of the proposed indexes. Finally, the action sequence of reactive power compensation devices is determined through the theory of fuzzy compromise decision making. The case study shows that the proposed method is effective to obtain the action sequence of reactive power compensation device which correspond to experience.

Accurate Reactive Power Controller and Power Factor Correction Using Fuzzy Logic

This paper presents the use of fuzzy logic technique to control the reactive power of load and hence improve the source power factor. A shunt compensator is proposed, which consists of a voltage controlled reactor by full-wave thyristor bridge in parallel with a capacitor. The proposed voltage control technique composed of two independent fuzzy controllers, primary and secondary. The PFC （primary fuzzy controller） is designed based on linearization method to introduce to the network the nearest value of reactive power （VAR） required to correct the power factor. The SFC （secondary fuzzy controller） is designed to achieve accurate compensation for the required VAR to achieve the pre-set power factor value. Simulations for 15 different practical study cases are presented to evaluate the performance of the controller, and the results show how the designed controller is fast and accurate. Harmonics analyses are carried out up to the 13th harmonic to determine the requirement of harmonics filter.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances.This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering largescale wind-power transmission.First,the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model.In the secondary voltage-control level,reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference.Considering the uncertainty and fluctuation of wind power,the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies.Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of halfwavelength lines effectively in different wind-power penetrations.

A novel digital control strategy of three-phase shunt active power filter under non-ideal mains voltages

A novel control strategy for three-phase shunt active power filter (SAPF) was proposed to improve its performance under non-ideal mains voltages. The approach was inspired by our finding that the classic instantaneous reactive power theory based algorithm was unsatisfactory in terms of isolating positive sequence fundamental active components exactly under non-ideal mains voltages. So, a modified ip-iq reference current calculation method was presented. With usage of the new method, not only the positive sequence but also the fundamental active current components can be accurately isolated from load current. A deadbeat closed-loop control model is built in order to eliminate both delay error and tracking error between reference voltages and compensation voltages under unbalanced and distorted mains voltages. Computer simulation results show that the proposed strategy is effective with better tracking ability and lower total harmonic distortion (THD). The strategy is also applied to a 10 kV substation with a local electrolysis manganese plant injecting a large amount of harmonics into the power system, and is proved to be more practical and efficient.

Minimization of Reactive Power Fluctuation in JT-60SA Magnet Power Supply

This paper describes an asymmetric control method for the firing angle and a start/stop timing shift control of four thyristor converters called ＂Booster PS＂ to minimize the reactive power fluctuation during plasma initiation in JT-60SA. From the simulation using the ＂PSCAD/EMTDC＂ code, it is found that these control methods can drastically reduce the reac- tive power induced by the four units of the ＂Booster PS＂. In addition, the voltage fluctuation of the motor-generator connected to the ＂Booster PS＂ is expected to be suppressed. This can also contribute to achieve stable control of the JT-60SA magnet power supplies.

Effect of Probabilistic Pattern on System Voltage Stability in Decentralized Hybrid Power System

This paper presents an proportional integral (PI) based voltage-reactive power control for wind diesel based decentralized hybrid power system with wide range of disturbances to demonstrate the compensation effect on system with intelligent tuning methods such as genetic algorithm (GA), artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS). The effect of probabilistic load and/or input power pattern is introduced which is incorporated in MATLAB simulink model developed for the study of decentralized hybrid power system. Results show how tuning method becomes important with high percentage of probabilistic pattern in system. Testing of all tuning methods shows that GA, ANN and ANFIS can preserve optimal performances over wide range of disturbances with superiority to GA in terms of settling time using Integral of Square of Errors (ISE) criterion as fitness function.

Regulation of the Excitation Reactive Power of the Asynchronous Wind Turbine at Variable Speed

This work focuses, initially, on modeling and simulating an isolated wind system in MATLAB/SIMULINK. And in the second part, it presents the simulation results of the wind system to start unloading and in resistive load, and the third part will discuss the strategy for adjusting the output voltage of the wind system to connect it to a rural operating load. The results show that in a dynamic environment where the wind speed and the load, changes abruptly, the voltage of the output is controlled at the desired value.

Dispersed Wind Power Planning Method Considering Network Loss Correction with Cold Weather

In order to play a positive role of decentralised wind power on-grid for voltage stability improvement and loss reduction of distribution network,a multi-objective two-stage decentralised wind power planning method is proposed in the paper,which takes into account the network loss correction for the extreme cold region.Firstly,an electro-thermal model is introduced to reflect the effect of temperature on conductor resistance and to correct the results of active network loss calculation;secondly,a two-stage multi-objective two-stage decentralised wind power siting and capacity allocation and reactive voltage optimisation control model is constructed to take account of the network loss correction,and the multi-objective multi-planning model is established in the first stage to consider the whole-life cycle investment cost of WTGs,the system operating cost and the voltage quality of power supply,and the multi-objective planning model is established in the second stage.planning model,and the second stage further develops the reactive voltage control strategy of WTGs on this basis,and obtains the distribution network loss reduction method based on WTG siting and capacity allocation and reactive power control strategy.Finally,the optimal configuration scheme is solved by the manta ray foraging optimisation(MRFO)algorithm,and the loss of each branch line and bus loss of the distribution network before and after the adoption of this loss reduction method is calculated by taking the IEEE33 distribution system as an example,which verifies the practicability and validity of the proposed method,and provides a reference introduction for decision-making for the distributed energy planning of the distribution network.

基于DIgSILENT/PowerFactory的轻型直流输电系统建模和仿真

介绍了轻型直流输电系统的结构特点,建立了基于电力系统仿真软件DIgSILENT/PowerFactory的轻型直流输电系统模型,分析了基于同步d-q旋转坐标系下的电压源换流器的稳态数学模型和直流电压、有功功率和无功功率的控制策略,对系统在直流电压、有功功率及无功功率变化条件下的动态性能进行了仿真。仿真结果表明,该系统具有很好的动态响应能力和鲁棒性,可以稳定工作于2个电网之间,独立控制无功功率达到静态无功补偿的作用。

Steady-state Voltage Security-constrained Optimal Frequency Control for Weak HVDC Sending-end AC Power Systems

Due to the fact that a high share of renewable energy sources(RESs)are connected to high-voltage direct current(HVDC)sending-end AC power systems,the voltage and frequency regulation capabilities of HVDC sending-end AC power systems have diminished.This has resulted in potential system operating problems such as overvoltage and overfrequency,which occur simultaneously when block faults exist in the HVDC link.In this study,a steady-state voltage security-constrained optimal frequency control method for weak HVDC sending-end AC power systems is proposed.The integrated virtual inertia control of RESs is employed for system frequency regulation.Additional dynamic reactive power compensation devices are utilized to control the voltage of all nodes meet voltage security constraints.Then,an optimization model that simultaneously considers the frequency and steady-state voltage security constraints for weak HVDC sending-end AC power systems is established.The optimal control scheme with the minimum total cost of generation tripping and additional dynamic reactive power compensation required is obtained through the optimization solution.Simulations are conducted on a modified IEEE 9-bus test system and practical Qing-Yu line commutated converter based HVDC(LCC-HVDC)sending-end AC power system to verify the effectiveness of the proposed method.

Performance of PI controller for control of active and reactive power in DFIG operating in a grid-connected variable speed wind energy conversion system

Due to several factors, wind energy becomes an essential type of electricity generation. The share of this type of energy in the network is becoming increasingly important. The objective of this work is to present the modeling and control strategy of a grid connected wind power generation scheme using a doubly fed induction generator （DFIG） driven by the rotor. This paper is to present the complete modeling and simulation of a wind turbine driven DFIG in the second mode of operating （the wind turbine pitch control is deactivated）. It will introduce the vector control, which makes it possible to control independently the active and reactive power exchanged between the stator of the generator and the grid, based on vector control concept （with stator flux or voltage orientation） with classical PI controllers. Various simula- tion tests are conducted to observe the system behavior and evaluate the performance of the control for some optimization criteria （energy efficiency and the robustness of the control）. It is also interesting to play on the quality of electric power by controlling the reactive power exchanged with the grid, which will facilitate making a local correction of power factor.

A voltage support control strategy based on three-port flexible multi-state switch in distribution networks

Voltage sags in power system may lead to serious problems such as the off-grid of distributed generation and electrical equipment failures.As a novel type of power electronic equipment,a flexible multi-state switch(FMSS)is capable to support the voltage during the grid faults.In this paper,a voltage control strategy to support the voltage in a distribution network is proposed by introducing three-port FMSS.The positive-negative-sequence compensation(PNSC)scheme is adopted to control the active and reactive current.This control scheme eliminates active power oscillations at the port of voltage sags and reduces coupling oscillations of other ports.Based on the characteristics of the voltage support under PNSC scheme,two voltage support strategies are proposed.A proportional-integral controller is introduced to provide the reactive power references,which eliminates the errors when estimating the grid voltage and impedance.A current limiting scheme is adopted to keep the port current in a safe range by adjusting the active and reactive power references.The voltage support strategies in two different voltage sags are simulated,and results show the feasibility and effectiveness of the proposed control strategies.

Design and Analysis of the Main AC/DC Converter System for ITER

A design of the main AC/DC converter system for ITER is described and the configuration of the main AC/DC converters is presented. To reduce the reactive power absorbed from the converter units, the main AC/DC converters are designed to be series-connected and work in a sequential mode. The structure of the regulator of the converter system is described. A simulation model was built up for the PSCAD/EMTDC code, and the design was validated accordingly. Harmonic analysis and reactive power calculation of the converters units are presented. The results reveal the advantage of sequential control in reducing reactive power and harmonics.

Enhancement of Distributed Generation by Using Custom Power Device

Wind energy （WE） has become immensely popular for distributed generation （DG）. This case presents the monitoring, modeling, control, and analysis of the two-level three-phase WE based DG system where the electric grid interfacing custom power device （CPD） is controlled to perform the smart exchanging of electric power as per the Indian grid code. WE is connected to DC link of CPD for the grid integration purpose. The CPD based distributed static compensator, i.e. the distributed static synchronous compensator （DSTATCOM）, is utilized for injecting the wind power to the point of common coupling （PCC） and also acts against the reactive power demand. The novel indirect current control scheme of DSTATCOM regulates the power import and export between the WE and the electric grid system. It also acts as a compensator and performs both the key features simultaneously. Hence, the penetration of additional generated WE power to the grid is increased by 20% to 25%. The burden of reactive power compensation from grid is reduced by DSTATCOM. The modeling and simulation are done in MATLAB. The results are validated and verified.

Research on On-Line Coordinated Control Strategy to Improve the Voltage Vulnerability after Disturbance

The on-line coordinated control strategy among multi-voltage controls is important to keep voltage security in post-fault systems. Based on the wide area measuring information, the energy function, which can qualify the impacts of the different control actions on voltage of different nodes, is proposed. And then, considering the impacts of different control actions on the node voltage being treated as a weight matrix, the energy margin is used as the objective function and the reactive power margin is innovatively used as the constraint to regulate the control actions globally according to the weight values. At last, the objective functions are solved to get the optimal global coordinated control strategies. The proposed method is identified in an IEEE-30 Bus system and the simulation results show that it effectively improves the voltage stability.