New trends in active filters for improving power quality

Since their basic compensation principles were proposed around 1970, active filters have been studied by many researchers and engineers aiming to put them into practical applications. Shunt active filters for harmonic compensation with or without reactive power compensation, flicker compensation or voltage regulation have been put on a commercial base in Japan, and their rating or capacity has ranged from 50 kVA to 60 MVA at present. In near future, the term of active filters will cover a much wider sense than that of active filters in the 1970s did. The function of active filters will be expanded from voltage flicker compensation or voltage regulation into power quality improvement for power distribution systems as the capacity of active filters becomes larger. This paper describes present states of the active filters based on state-of-the-art power electronics technology, and their future prospects toward the 21st century, including the personal view and expectation of the author</p

FOPID Controlled Shunt Active Filter in IEEE Thirty Bus System with Improved Dynamic Time Response

This paper aims on improving the dynamic time response of a Wind Energy Conversion System (WECS) connected to IEEE Thirty Bus System(TBS) using Permanent Magnet Synchronous Generator (PMSG) in closed loop controlled Active Power Filter with FOPID. The simulation results are presented to find the effect of shunt active filter using FOPID controller. Open Loop Thirty Bus System (OLTBS) with change in load is simulated. The simulation results with PI and FOPID Controller based SAF are compared and the corresponding time-domain parameters are presented. The results indicate that FOPID Controller system has better response than PI controlled system

Adaptive Predictive Deadbeat Current Control of Single-Phase Multi-tuned Shunt Hybrid Active Power Filters

This paper suggests an adaptive predictive deadbeat current control method for single-phase multi-tuned shunt hybrid active power filters (HAPFs) to improve the power quality of single-phase and three-phase four-wire utility grids. The HAPF structure eliminates the resonance between the passive power filter and the grid impedance. Furthermore, it can be integrated into passive filters to enhance their filtering performance. In this paper, a digital algorithm is proposed for managing the performance of each converter leg accurately. To do so, an exact model of the high-order system is developed, and the transfer function of the plant is calculated in continuous and discrete time domains. Then, a predictive deadbeat technique for HAPF current control is presented, which benefits from high accuracy, fast dynamics, and low sensitivity to system parameter mismatches. Extensive simulation and experimental tests are conducted and the results match well to confirm the success and appropriate performance of the overall system. Also, performance comparison with conventional solutions demonstrates the superiority of the suggested filtering technique

Mitigation of power quality issues due to high penetration of renewable energy sources in electric grid systems using three-phase APF/STATCOM technologies: a review.

This study summarizes an analytical review on the comparison of three-phase static compensator (STATCOM) and active power filter (APF) inverter topologies and their control schemes using industrial standards and advanced high-power configurations. Transformerless and reduced switch count topologies are the leading technologies in power electronics that aim to reduce system cost and offer the additional benefits of small volumetric size, lightweight and compact structure, and high reliability. A detailed comparison of the topologies, control strategies and implementation structures of grid-connected high-power converters is presented. However, reducing the number of power semiconductor devices, sensors, and control circuits requires complex control strategies. This study focuses on different topological devices, namely, passive filters, shunt and hybrid filters, and STATCOMs, which are typically used for power quality improvement. Additionally, appropriate control schemes, such as sinusoidal pulse width modulation (SPWM) and space vector PWM techniques, are selected. According to recent developments in shunt APF/STATCOM inverters, simulation and experimental results prove the effectiveness of APF/STATCOM systems for harmonic mitigation based on the defined limit in IEEE-519

An 'active' passive-filter topology for low power DC/AC inverters

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis presents a new output passive filter for voltage source inverter applications which is based on a shunt connected single tuned filter topology. The proposed circuit has the advantage of tracing harmonic components wherever its location in the frequency spectrum. The change in the harmonic location might be as a result of a change in the inverter operating frequency. Also, the proposed filter achieves harmonic reduction close to the traditional single tuned passive filter. In order to show the superiority of the proposed model, a comparison is introduced with other self tuning harmonic filters showing merits and drawbacks of each technique. The proposed circuit (when integrated in square wave inverter) has also shown a tremendous reduction in the switching losses in comparison with high frequency Pulse Width Modulation inverter. Mathematical analyses showing the design of the proposed filter together with extensive simulation results to verify the design are also introduced. The practical implementation of the system is presented and the results show excellent agreement with the theory and simulation. In order to appreciate the proposed filter a new method for classifying passive power filters is introduced. The review includes a comparison of these configurations showing their merit and drawbacks

Data-driven model-based approaches to condition monitoring and improving power output of wind turbines

The development of the wind farm has grown dramatically in worldwide over the past 20 years. In order to satisfy the reliability requirement of the power grid, the wind farm should generate sufficient active power to make the frequency stable. Consequently, many methods have been proposed to achieve optimizing wind farm active power dispatch strategy. In previous research, it assumed that each wind turbine has the same health condition in the wind farm, hence the power dispatch for healthy and sub-healthy wind turbines are treated equally. It will accelerate the sub-healthy wind turbines damage, which may leads to decrease generating efficiency and increases operating cost of the wind farm. Thus, a novel wind farm active power dispatch strategy considering the health condition of wind turbines and wind turbine health condition estimation method are the proposed. A modelbased CM approach for wind turbines based on the extreme learning machine (ELM) algorithm and analytic hierarchy process (AHP) are used to estimate health condition of the wind turbine. Essentially, the aim of the proposed method is to make the healthy wind turbines generate power as much as possible and reduce fatigue loads on the sub-healthy wind turbines. Compared with previous methods, the proposed methods is able to dramatically reduce the fatigue loads on subhealthy wind turbines under the condition of satisfying network operator active power demand and maximize the operation efficiency of those healthy turbines. Subsequently, shunt active power filters (SAPFs) are used to improve power quality of the grid by mitigating harmonics injected from nonlinear loads, which is further to increase the reliability of the wind turbine system

Analysis, Dimensioning and Robust Control of Shunt Active Filter for Harmonic Currents Compensation in Electrical Mains

In this chapter some results related to Shunt Active Filters (SAFs) and obtained by the authors and some coauthors are reported. SAFs are complex power electronics equipments adopted to compensate for cur-rent harmonic pollution in electric mains, due to nonlinear loads. By using a proper "floating" capacitor as energy reservoir, the SAF purpose is to inject in the line grid currents canceling the polluting har-monics. Control algorithms play a key role for such devices and, in general, in many power electronics applications. Moreover, systems theory is crucial, since it is the mathematical tool that enables a deep understanding of the involved dynamics of such systems, allowing a correct dimensioning, beside an effective control. As a matter of facts, current injection objective can be straightforwardly formulated as an output tracking control problem. In this fashion, the structural and insidious marginally-stable internal/zero dynamics of SAFs can be immediately highlighted and characterized in terms of sizing and control issues. For what concerns the control design strictly, time-scale separation among output and internal dynamics can be effectively exploited to split the control design in different stages that can be later aggregated, by using singular perturbation analysis. In addition, for robust asymptotic output tracking the Internal Model Principle is adopted.Comment: Paper presented at the AUTOMATICA_IT 2011 conference, Pisa, Italy, September 201

Neural Networks based Shunt Hybrid Active Power Filter for Harmonic Elimination

The growing use of nonlinear devices is introducing harmonics in the power system networks that results in distortion of current and voltage signals causing damage to the power distribution system. Therefore, in power systems, the elimination of harmonics is of great concern. This paper presents an efficient techno-economical approach to suppress harmonics and improve the power factor in the power distribution network using neural network algorithms-based Shunt Hybrid Active Power Filter (SHAPF), such as Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Recurrent Neural Network (RNN). The objective of the proposed algorithms for SHAPF is to reduce Total Harmonic Distortion (THD) within an acceptable range to improve system quality. In our filter design approach, we tested and compared conventional pq0 theory and neural networks to detect the harmonics present in the power system. Moreover, for the regulation of the DC supply to the inverter of the SHAPF, the conventional PI controller and neural networks-based controllers are used and compared. The applicability of the proposed filter is tested for three different nonlinear load cases. The simulation results show that the neural networks-based filter control techniques satisfy all international standards with minimum current THD, neutral wire current elimination, and small DC voltage fluctuations for voltage regulation current. Furthermore, all three neural network architectures are tested and compared based on accuracy and computational complexity, with RNN outperforming the rest

Addressing Instability Issues in Microgrids Caused By Constant Power Loads Using Energy Storage Systems

Renewable energy sources, the most reasonable fuel-shift taken over the naturally limited conventional fuels, necessarily deal with the self-functional microgrid system rather than the traditional grid distribution system. The study shows that the microgrid system, a comparatively low-powered system, experiences the challenge of instability due to the constant power load (CPL) from many electronic devices such as inverter-based systems. In this dissertation, as a methodical approach to mitigate the instability complication, AC microgrid stability is thoroughly investigated for each and every considerable parameter of the system. Furthermore, a specific loading limit is depicted by evaluating the stability margin from the small signal analysis of the microgrid scheme. After demonstrating all cases regarding the instability problem, the storage-based virtual impedance power compensation method is introduced to restore the system stability and literally extend the loading limit of the microgrid system. Here, a PID controller is implemented to maintain the constant terminal voltage of CPL via current injection method from storage. Since the system is highly nonlinear by nature, advanced nonlinear control techniques, such as Sliding Mode Control and Lyapunov Redesign Control technique, are implemented to control the entire nonlinear system. Robustness, noise rejection, and frequency variation are scrutinized rigorously in a virtual platform such as Matlab/Simulink with appreciable aftermaths. After that, a comparative analysis is presented between SMC and LRC controller robustness by varying CPL power. From this analysis, it is evident that Lyapunov redesign controller performs better than the previous one in retaining microgrid stability for dense CPL-loaded conditions. Finally, to ensure a robust storage system, Hybrid Energy Storage System is introduced and its advantages are discussed as extended research work