Flicker Mitigation Research Articles

M-ary Variable Period Modulation for Indoor Visible Light Communication System

M-ary variable period modulation is proposed in this paper as a candidate modulation scheme for an indoor visible light communication system. The principle of M-ary variable period modulation is described in details, the parameter selection guide and flicker mitigation and dimming control choices are discussed. Theoretical analysis and experimental results indicate that the method proposed is effective for an indoor visible light communication system.

Mitigation of Voltage flicker and reduction in THD by using STATCOM

Voltage flicker is considered as one of the most severe power quality problems (especially in loads like electrical arc furnaces) and much attention has been paid to it lately. Due to the latest achievements in the semiconductors industry and consequently the emergence of the compensators based on voltage source converters, FACTS devices have been gradually noticed to be used for voltage flicker compensation. This paper covers the contrasting approaches; dealing with the voltage flicker mitigation in three stages and reduction in total harmonic distortion and assessing the related results in details. Initially, the voltage flicker mitigation, using FCTCR (Fixed Capacitor Thyristor Controlled Reactor), was simulated. Secondly, the compensation for the six-pulse as well as 12-pulse Static Synchronous Compensator (STATCOM) has been performed. In this case, injection of harmonics into the system caused some problems which were later overcome by using 12-pulse assignment of SATCOM and RLC filter (three phase harmonic filter). The obtained results show that STATCOM is very efficient and effective for the flicker compensation as well as harmonic sprectrum. All the simulations have been performed on the MATLAB Software. DOI: http://dx.doi.org/10.11591/ijece.v3i1.1951

Compensation of Voltage Flicker by Using Facts Devices

Voltage flicker occurs when heavy loads are periodically turned on and off in a weak distribution system. If the distribution system’s short circuit capacity is not large enough, voltage fluctuations will occur. Voltage flickering can be extremely harmful to sensitive electronic equipment. Computerized equipment requires stable voltage to perform properly. This paper covers the contrasting approaches; dealing with the voltage flicker mitigation in three stages and assessing the related results in details. Initially, the voltage flicker mitigation, using FCTCR (Fixed Capacitor Thyristor Controlled Reactor), was simulated. Secondly, the compensation for the Static Synchronous Compensator (STATCOM) has been performed. In this case, injection of harmonics into the system caused some problems which were later overcome by using 12-pulse assignment of SATCOM and RLC filters. The obtained results show that STATCOM is very efficient and effective for the flicker compensation. All the simulations have been performed on the MATLAB Software

Multi-objective reactive power support from wind farms for network performance enhancement

This paper examines the ability of the doubly fed induction generator (DFIG) to deliver multiple reactive power objectives during variable wind conditions. The reactive power requirement is decomposed based on various control objectives (e.g. power factor control, voltage control, loss minimisation, and flicker mitigation) defined around different time frames (i.e. seconds, minutes, and hourly), and the control reference is generated by aggregating the individual reactive power requirement for each control strategy. A novel coordinated controller is implemented for the rotor-side converter and the grid-side converter considering their capability curves and illustrating that it can effectively utilise the aggregated DFIG reactive power capability for system performance enhancement. The performance of the multi-objective strategy is examined for a range of wind and network conditions, and it is shown that for the majority of the scenarios, more than 92% of the main control objective can be achieved while introducing the integrated flicker control scheme with the main reactive power control scheme. Therefore, optimal control coordination across the different control strategies can maximise the availability of ancillary services from DFIG-based wind farms without additional dynamic reactive power devices being installed in power networks

Effective Mitigation of Voltage Flicker in Power System using 12-Pulse Converter based Statcom

A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end user equipments. Voltage flicker is considered as one of the most severe power quality problems caused by large time-varying loads like arc furnaces. To reduce this kind of disturbances, Static Var Compensators (SVC) has been used so far which have a limited flicker mitigation capability. In the paper, 12-pulse converter based STATCOM has been proposed for effective mitigation of Voltage flicker and reduction of total harmonic distortion in the system. All the simulations have been performed using MATLAB Software. The obtained results show that 12-pulse converter based STATCOM is very efficient and effective for the mitigation of voltage flickering and THD reduction.

Flicker Suppression Scheme for Variable-Speed Wind Turbine Systems

This paper proposes a strategy of flicker mitigation for doubly-fed induction generator (DFIG) wind turbine systems. In the weak grid system where the grid impedance ratio is low, the reactive power compensation only cannot suppress the flicker sufficiently due to the limited power capacity of the converters or the DFIG. For the full suppression of flickers, the active power smoothening using the energy storage system (ESS) needs to be utilized together with the reactive power compensation. The effectiveness of the proposed method is verified by PSCAD/EMTDC simulation results for a 2[MW] DFIG wind turbine system and by experimental results for a 3[kW] wind turbine simulator.

A Flexible DG Interface Based on a New RLS Algorithm for Power Quality Improvement

Distributed generation (DG) exists in distribution systems and is installed by either the utility or the customers. This paper proposes a novel utilization of the existing DG interface to not only control the active power flow, but also to mitigate unbalance, harmonics and voltage flicker, and manage the reactive power of the system. The proposed flexible distributed generation (FDG) is similar in functionality to FACTS, but works at the distribution level. Moreover, a novel recursive least square (RLS) structure is presented. The new structure is applied to multi-output (MO) systems for parameter tracking/estimation, and is called MO-RLS. It is dedicated to symmetrical components estimation. An innovative processing unit-based RLS is investigated to deal with unbalance, harmonics, and reactive power compensation. In addition, this paper portrays a technique for flicker mitigation based on the RLS algorithm for instantaneous tracking of the measured voltage envelope. One advantage of the proposed control system is its insensitivity to parameter variation, a necessity for distribution system applications. Simulations of the suggested FDG based control algorithm are conducted to evaluate the performance of the proposed system.

Residential shadow flicker monitoring: a case study in IoT product development

In almost every field, the technological advancements that have led to the so-called Internet of Things (IoT) era, such as low-energy computing and the increasing speed/decreasing cost of internet data, are enabling the development of new and interesting connected devices. One recent example is the development of a device for monitoring wind turbine shadow flicker at residential properties. The monitoring device provides accurate data for wind operators, residents and local authorities to investigate and fine-tune flicker mitigation measures.

Mitigation of Arc Furnace Voltage Flicker Using an Innovative Scheme of Adaptive Notch Filters

This paper presents an innovative application of the adaptive notch filters for flicker disturbance extraction and mitigation. This paper demonstrates a new cascaded scheme of adaptive notch filters and regular notch filters. This suggested scheme is used for tracking the frequencies of flicker disturbances and for the instantaneous extraction of these disturbances. Furthermore, this paper exhibits the utilization of a developed compensation strategy that employs shunt and series power conditioners to intelligently mitigate voltage flicker that emanates from electric arc furnaces. The proposed schemes for frequency tracking, disturbance extraction, and flicker mitigation are verified by simulation results using real voltage and current flicker waveforms of the ac arc furnace.

Mitigation of Flicker using STATCOM with Three-Level 12-pulse Voltage Source Inverter

Mitigation of Flicker using STATCOM with Three-Level 12-pulse Voltage Source Inverter

Flicker mitigation in a doubly fed induction generator wind turbine system

This paper describes a doubly fed induction generator (DFIG) control for wind energy generation. The DFIG model is established and the adopted control strategies for machine side and grid side converters are described. Flicker phenomenon is defined and its emission of variable speed wind turbine with DFIG during continuous operation is studied. Calculation of flicker severity is evaluated using flickermeter. Appropriate vector power control of the machine side converter is proposed and applied to achieve flicker mitigation.

Power ramp rate control and flicker mitigation for directly grid connected wind turbines

Power variation, voltage fluctuation and resultant flicker are critical issues related to the integration of directly grid-connected constant-speed wind turbines. This study introduces a methodology to enhance the quality of the power and voltage, and minimise the flicker produced from constant-speed direct-connected wind turbines. The method uses an electrolyser/fuel cell combination to be connected to the point of common coupling via limited rating converters. The control scheme is designed to keep the power ramp rate and voltage fluctuation within their limits and minimise the rating of the converters used to interface the electrolyser and the fuel cell. The incorporation of STATCOM and its effect on the generated power and flicker level have been investigated. Simulation results are carried out to demonstrate and validate the proposed technique.

Electric Arc Furnace Voltage Flicker Mitigation by Applying a Predictive Method with Closed Loop Control of the TCR/FC Compensator

Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.

영구자석형 동기발전기를 이용한 풍력단지의 플리커 저감

The power quality of wind energy becomes more and more important in connecting wind-farms to the grid, especially weak grid. This paper presents the simulation of a wind farm of a permanent magnet synchronous generator (PMSG) and a doubly fed induction generator (DFIG). Flicker mitigation is performed by using PMSG as a static synchronous compensator (STATCOM) to regulate the voltage at the point of common coupling (PCC). A benefit of the measure is that integrating two function of to control the active power flow and to reduce the voltage flicker in a wind farm. Simulation results show that controlling PMSG is an effective and economic measure in reducing the flicker during continuous operation of grid connected wind turbines regardless of short circuit capacity ratio, turbulence intensity and grid impedance angle.

Mitigation of the Flicker Level of a DFIG Using Power Factor Angle Control

The flicker emission of the wind turbine is affected by wind speed, wind turbulence, generator type, and grid conditions (e.g., the short-circuit ratio, the grid impedance, and the load type). In this letter, an effective control scheme to mitigate flicker emission of a doubly fed induction generator (DFIG) is suggested. By controlling the power factor angle of the DFIG, the flicker is more effectively removed than any other flicker mitigation methods.

Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines With Full-Scale Back-to-Back Power Converters

Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a megawatt-level variable-speed wind turbine with a full-scale back-to-back power converter developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. Reactive power compensation is mostly adopted for flicker mitigation. However, the flicker mitigation technique shows its limits, when the grid impedance angle is low in some distribution networks. A new method of flicker mitigation by controlling active power is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the dc-link voltage of the full-scale converter. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation controller is an effective means for flicker mitigation of variable-speed wind turbines with full-scale back-to-back power converters during continuous operation.

Power System Flicker Analysis by RMS Voltage Values and Numeric Flicker Meter Emulation

This paper introduces a new methodology of flicker analysis by using root-mean-square (rms) voltage values. The main objective is to simplify flicker assessment in a large-scale grid and propose adequate methods in order to carry out flicker analysis with general power system software. The basis of this paper is that the common flicker frequency of industrial loads is lower than 25 Hz; this makes it possible to use rms values instead of waveform samples to perform flicker computation. The researches are focused on the following three key points in flicker analysis: (1) fast voltage change-dependent distribution load model used for flicker propagation study, (2) IEC 61000-4-15 flicker meter emulators, and (3) simplified dynamic flicker load models. The studied load models and flicker meter emulators have been integrated in power-quality simulation software with the electromechanical transient analysis module. Field measurements have been used to verify and support the proposed methodology. Different case studies show that this approach gives satisfied results in flicker assessment and flicker mitigation. It is also used by utilities to perform flicker assessment prior to the connection of a disturbance load.

Reactive and real power compensation with DSTATCOM and BESS for mitigation of flicker

Voltage flicker, a phenomenon of annoying light intensity fluctuation, caused by rapid change in industrial and domestic load such as electric arc furnaces (EAF), rolling mills, welding equipments and pumps operating periodically, has been a major concern for supply utilities, electricity regulatory agencies and costumers. The FACTS devices like SVC's, STATCOM and custom power devices like DSTATCOM have been able to solve the voltage flicker problems by rapidly controlling the reactive power. But, control of active power along with reactive power control helps to mitigate the voltage flicker problem more effectively. In this paper, voltage flicker mitigation of electric arc welder with DSTATCOM along with battery energy storage system (BESS) is analysed using the PSCAD/EMTDC software. The proposed algorithm controls the voltage oscillations and fluctuations. The mathematical model of resistance welder suitable for the flicker phenomenon is presented. The dynamic operation is investigated using this algorithm.

Flicker Mitigation With a Hybrid Compensator

This paper concentrates on a solution for the voltage flicker problem caused by a resistance spot welding process. Resistance spot welding is characterized by high currents lasting for a few mains voltage periods and followed by idle time lasting several cycles. This causes repetitive voltage changes and creates a phenomenon called flicker. Voltage fluctuations are difficult to compensate since the length of the welding period, the delay time between cycles, and the amplitude of currents may vary substantially. In the literature, active compensators such as active filters have been found effective in compensating changing loads, providing fast compensating responses. However, they should be rated on the basis of the maximum compensating power needed. This paper examines a solution based on a hybrid compensator. The system consists of an active compensator and a fixed detuned filter. The main task of the active part is to compensate changes in the fundamental reactive power, whereas the passive part provides a reduction in the ratings of the active compensator. Since the active part incorporates an active filter, load current harmonics are also compensated as a "by-product." The system stability is analyzed, and the performance is examined in simulations and practical experiments. The resulting flicker severity indices are also assessed. The results show that with the proposed system, voltage fluctuations and flicker levels can be greatly reduced. The dynamics of the combination are found to be fast enough to compensate the rapid variations in the reactive power of the plant. A further benefit is smoothed instantaneous active power drawn from the mains.

전기로 부하에서 SVC의 고조파 및 플리커 효과에 관한 연구

Large steel industries have time-varying nonlinear loads including electric arc furnaces. These nonlinear loads generate harmonic currents and create distortions on the sinusoidal voltage of the power system. Flicker can be defined as the effect produced on the human visual perception by a changing emission of light lamps subjected to magnitude fluctuations of their supply voltage. The main objective of the static var compensator(SVC) is to maintain the rms voltage at the point of common coupling within the limit. In this paper, harmonic and flicker mitigation studies with and without the SVC are investigated and are evaluated by the IEC 61000-3-6 and IEC 61000-3-7.