Active Filters

This paper investigates the design,analysis and simulation of a Distribution-STATic COMpensator(D-STATCOM) for non-linear load Composite(harmonic and reactive power) compensation on a three phase bus network. Composite compensation is achieved by implementation of a p-q controller, which monitors the load current and injects equal amplitude and opposite phase compensation currents to neutralize load reactive power and harmonics. This ensures the source current remains fundamental. This paper simulated results in MATLAB platform and showed that a D-STATCOM is suited for use in reactive power and harmonic compensation on any bus on a power system network.

This paper describes the current conveyors used as a basic building block in a variety of electronic circuit in instrumentation and communication systems. Today these systems are replacing the conventional Op-amp in so many applications such as active filters, analog signal processing, and converters. A detailed study is presented here for its applications.

Two new voltage-mode multifunction filters using only one positive-type second generation current conveyor (CCII+) or current feedback op-amp (CFOA, commercially available chip AD844), two resistors and two capacitors are proposed. The proposed filters which have three inputs and one output can generate all biquadratic filtering functions namely: low-pass (LP), band-pass (BP), high-pass (HP), band-reject (BR) and allpass (AP) at the output terminal by selecting different input signal combinations. Literature survey concerning the component number is also discussed. PSpice simulations and experimental results confirm the results of the theoretical analysis.

This letter presents a novel recursive active filter topology that provides dual-band performance, with independent tuning capability in both bands. The dual-band operation is achieved by using two independent feedback lines. Additionally, linear phase shifters based on left-handed cells are included in these two branches in order to tune the center frequency of both pass bands.

The expanding industrial employment of medium frequency electric energy demands the energy supply of medium frequency consumers to be ensured by developing medium frequency distribution networks instead of feeding these consumers individually. The aim of this investigation was to work out theoretically variants of energy supply, ensuring on the one hand independent operation of the consumers connected to the medium frequency network, and on the other hand facilitating the transportation of medium frequency energy to large distances while consumers' requirement are fulfilled. It has been verified that the approximately constant voltage or current along the transmission line necessary for the independence of consumers and for energy transport to great distances can be maintained with the aid of compensating elements to be inserted in the line. In the course of the investigation of the various compensating methods, the values of the compensating reactances have been determined, and the effects of the variation of certain system parameters (load, frequency) have been checked. It has been concluded that the most favourable solution to the problem examined is obtained by the insertion of 7r or Tarrangements of appropriate compensating reactances into the transmission line.

Abstract
The pervasive use of medium voltage drives (MVDs) in heavy industrial environments has dramatically improved energy efficiency and process control; however, these devices also introduce significant harmonic distortions into power systems. Harmonic pollution from MVDs can degrade power quality, increase losses, overheat electrical equipment, reduce system reliability, and trigger protective devices unnecessarily. As industrial facilities expand and electrical systems become more complex, effective harmonic mitigation has become essential for maintaining stable and efficient operations. This paper explores state-of-the-art techniques for mitigating harmonics generated by medium voltage drives in heavy industrial loads, including passive filters, active power filters (APFs), hybrid filter solutions, multi-pulse rectification, and advanced control strategies such as real time adaptive compensation and predictive algorithms. The relative advantages, limitations, and practical considerations of each technique are examined within the context of industrial power distribution systems, emphasizing response speed, implementation cost, system compatibility, and harmonic cancellation performance. Case studies and simulation results demonstrate how combinations of passive and active mitigation solutions can significantly reduce total harmonic distortion (THD), improve voltage waveform quality, and enhance overall system performance. The paper also highlights future research directions, including integration with smart grid technologies, real time optimization of mitigation devices, and machine learning based harmonic prediction models. By providing a comprehensive overview of harmonic mitigation strategies tailored to medium voltage drives in industrial settings, this study offers practical guidance for engineers and system designers seeking to improve power quality, system resilience, and operational efficiency in heavy industrial loads.

This paper presents a modified predictive current control strategy which allows one to have control over the spectrum of the load current. The proposed method uses a model of the system to predict the behavior of the current for each possible voltage vector generated by the inverter. For that purpose, at each sampling interval, signal predictions are evaluated using a cost function that quantifies the desired system behavior. The cost function used in this work evaluates the filtered error of the load currents. The inclusion of a filter for the load error allows one to manipulate current spectra. Thus, by designing this filter appropriately, the load spectrum can be shaped. The performance of the proposed control strategy is verified by simulation and experimental results.

In this paper, equivalents circuits of the three phase induction motor high frequency are presented; the proposed model detailed separately the common Mode and differential mode characteristics AC electrical motor. The high-frequency model has been obtained by means of a frequency domain analysis using MATLAB program.

Power quality problems in power systems have been improved due to nonlinear loads. To compensate these problems Direct Power Compensator was proposed in this paper. A Direct Power Compensator (DPC) is proposed in this paper to eliminate the harmonic currents, compensate power factor and voltage unbalance problems created by the nonlinear loads present in three phase systems. A DPC contains back to back converter by sharing the same dc link power and v/v transformer to provide a voltage balance in transmission line. Hysteresis harmonic current regulator is used to produce pulse for back to back converter. A controller maintains the dc-link voltage and compensates the power factor, harmonic currents. A comparative analysis for traction system with and without DPC was performed using MATLAB Simulink. Simulation results show the controller advantages and the applicability of the proposed method in railway systems. MANIFESTATION TERM -Active filters, harmonics distortion, power control, rail transportation power system, Direct Power Compensator (DPC).

Power quality problems in power systems have been improved due to nonlinear loads. To compensate these problems Direct Power Compensator was proposed in this paper. A Direct Power Compensator (DPC) is proposed in this paper to eliminate the harmonic currents, compensate power factor and voltage unbalance problems created by the nonlinear loads present in three phase systems. A DPC contains back to back converter by sharing the same dc link power and v/v transformer to provide a voltage balance in transmission line. Hysteresis harmonic current regulator is used to produce pulse for back to back converter. A controller maintains the dc-link voltage and compensates the power factor, harmonic currents. A comparative analysis for traction system with and without DPC was performed using MATLAB Simulink. Simulation results show the controller advantages and the applicability of the proposed method in railway systems. MANIFESTATION TERM -Active filters, harmonics distortion, power control, rail transportation power system, Direct Power Compensator (DPC).

Power quality problems in power systems have been improved due to nonlinear loads. To compensate these problems Direct Power Compensator was suggested in this paper. A Direct Power Compensator (DPC) is proposed in this paper to reduce the harmonic currents, compensate power factor and voltage unbalance problems generated by the nonlinear loads present in three phase systems. A DPC contains back to back converter by sharing the same dc link power and v/v transformer to provide a voltage balance in transmission line. Hysteresis harmonic current regulator is used to create pulse for back to back converter. A controller maintains the dc-link voltage and compensates the power factor, harmonic currents. A comparative analysis for traction system with and without DPC was performed using MATLAB Simulink. Simulation results show the controller advantages and the applicability of the proposed method in railway systems.

A full compensating system for distribution networks which is able to eliminate harmonics, correct unbalanced loads and generate or absorb reactive power is presented. The system is based on a combination of a Thyristor Binary Compensator (TBC), and a PWM-IGBT Active Power Filter (APF) connected in cascade. The TBC compensates the fundamental reactive power and balances the load connected to the system. The APF eliminates the harmonics and compensates the small amounts of load unbalances or power factor that the TBC cannot eliminate due to its binary condition. The TBC is based on a chain of binary-scaled capacitors and one inductor per phase. This topology allows, with an adequate number of capacitors, a soft variation of reactive power compensation and a negligible generation of harmonics. The capacitors are switched-on when the line voltage reaches its peak value, avoiding inrush currents generation. The inductor helps to balance the load, and absorbs reactive power when required. The APF works measuring the source currents, forcing them to be sinusoidal. The two converters (TBC and APF) work independently, making the control of the system simpler and more reliable. The system is able to respond to many kinds of transient perturbations in no more than a couple of cycles. The paper analyzes the circuit proposed, the way it works and the results obtained under operation with different types of loads.

The present work proposes a new current-mode, programmable Kerwin Huelsman Newcomb (KHN) filter suitable for very low frequency processing. The proposed implementation, developed with only six current mirrors and two large-valued, programmable active resistors, solves some of the more challenging problems of low frequency filtering. HSPICE simulation results using BSIM3.3 models for a 0.5-µm CMOS technology, are shown. Center frequencies in the range of 12.4 Hz -33 Hz, total harmonic distortion less than 1 %, and static power consumption of 1.05 mW, were observed.

In this paper, a new method to control an active power filter using Neural Networks is presented. Currently, there is an increase of voltage and current harmonics in power systems, caused by nonlinear loads. The Active Power Filters (APFs) are used to compensate the generated harmonics and to correct the load power factor. The proposed control design is a Pulse Width Modulation (PWM) control with two blocks that include Neural Networks. Adaptive networks estimate the reference compensation currents. On the other hand, a multilayer feedforward network (trained by a backpropagation algorithm) that works as hysteresis band comparator is used. A practical case with Matlab-Simulink is presented to check the proposed control performance.

Along the last years, the practical use of active filters to mitigate harmonics has been extended in electric power systems. Different configurations of series active filters versus shunt active filters have been proposed, among them, hybrid topologies which combine active and passive filters. Nevertheless, there is not any clear accordance about the most suitable configuration for each type of harmonic sources. In this paper, four different topologies of active power filters to eliminate harmonics have been analyzed. An experimental prototype has been implemented to each configuration and have been submitted to different performance tests. With this objective, a test bank has been developed, which includes nonlinear loads kind harmonic current source, ahrmonic voltage source, and other whose behavior is between they both. The analysis of experimental results obtained allows the most suitable active filter power topology to be determined for each type of load.

This paper presents the design of a shunt active filter to compensate reactive power and harmonics in the medium voltage level of a power distribution system. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The alternative of shunt active filter compensation connected to the 13.8 kV level is analyzed. Two alternatives are proposed, the first one considers full compensation with the active filter while the second one uses the existing capacitor bank and builds the complementary compensation with the active filter. In the last case, the capacitor bank is modified to make a 5 th harmonic filter to avoid system resonances. Both proposals show very good performance.

The behavior of the actual load of an electric energy distribution utility by means of voltage and current measurements is analyzed in this paper. Steady and transient states are taken into account. The main attention is fixed in points where present shunt compensation is installed. Results of field measurements and the connection and disconnection of capacitor banks are shown. Studies for future compensation are detailed and the possible advantages of active filter incorporation are analyzed in order to replace or complement the existing compensation. The minimal requirements are established in order to consider the design of the active filters and their compatibility with the existing installations.

The problem of reactive power and harmonics in the medium voltage level of a power distribution system is considered in this paper. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The alternative of a shunt hybrid active filter connected to the 13.8-kV level to enhance the power quality is analyzed in this paper. This proposal uses the existing capacitor bank to build a hybrid filter in which the complementary compensation is performed by the active filter. The performance of the hybrid filter is evaluated with extensive simulations considering reactive power, harmonics, and unbalance compensation. It shows very good behavior in steady-state and transient conditions.

This paper deals with the problem of reactive power and harmonics in a standard medium-voltage (MV) distribution network. It proposes a simple and inexpensive solution to enhance power quality when a particular connection to the high-voltage transmission network is required. It presents the design of a hybrid active filter topology connected to the MV level of a power distribution system. Its main task is to regulate a 132-kV voltage level. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The topology of a shunt hybrid active filter is analyzed. It is built with the series connection of a passive filter and a low-rated active filter. The proposed filter is directly connected to a 13.8-kV level with no need of a step-down transformer. The possibility of different levels of reactive power compensation is implemented. The proposal shows very good performance for different load demands.

The analytical design procedure of lowsensitivity, low-power, low-pass (LP) 2 nd -and 3 rd -order class-4 active-RC allpole filters, using impedance tapering, has already been published [1][2]. In this paper the desensitisation using impedance tapering is applied to the design of LP 4 th -order filters. The numerical design procedure was performed by Newton's iterative method. Analytically designed unity-gain LP 4 th -order filters [3] can provide initial values for Newton's method. The sensitivities of a filter transfer function to passive component tolerances, as well as active gain variations are examined by the Schoeffler sensitivity and Monte Carlo PSpice simulation. Butterworth and Chebyshev 0.5dB filter examples illustrate the design method.

Most of the pollution issues created in power systems are due to the non-linear characteristics and fast switching of power electronic equipment. The use of the power electronic devices in power distribution system gives rise to harmonics and reactive power disturbances. The harmonics and reactive power cause a number of undesirable effects in the power system. Active Power Filters(APF) have been developed over the years to solve these problems to improve power quality .This paper presents a comprehensive review of Active Power filter configurations, control strategies and the Total Harmonic Distortion(THD) for different control strategies both in analog and digital(DSP, FPGA) environments.

This article concludes a six-part series on the intuitive approach to active digital filter (ADF) design, which has introduced a novel branch in digital signal processing (DSP) termed "Active DSP." This designation reflects the authors' pioneering work and the creative freedom to define it. The previous five parts covered the principles and applications of ADFs across major filter types. ADF design is likened to art, requiring talent and creativity, and to magic, as skilled designers can achieve remarkable outcomes. This final part focuses on active inverse filtering, a transformative technique in active DSP. The article demonstrates how a high-pass filtered ECG signal can be effortlessly restored to its original form using an inverse ADF. Practical applications, including square-root and RMS calculations, synchronous filtering, impedance balance, automatic gain control, and phase-locked loops, are summarized to provide a comprehensive overview of some of the major applications of active DSP.

The developed intuitive approach to active digital filter (ADF) design has introduced a new branch in digital signal processing (DSP) called "Active DSP". This term "active" reflects its reliance on digital integrators that function as digital operational amplifiers within closed-loop filtering systems. The approach bridges the gap between analog and digital filter design, translating analog filters into their digital counterparts and enabling the creation of entirely new filter designs. Thus far, the methodology has been presented in a four-part series. It begins with first-order filters, continues through second and higher-order low-pass and high-pass filters, and culminates with active biquads, the universal filtering stages in ADF design. This paper, Part V of the series, focuses on the design of active all-pass filters (APFs), a type of filter not yet explored in ADF. It offers a detailed tutorial on intuitively translating analog APFs into their digital counterparts and demonstrates how the universal digital filters, introduced in previous parts, can be easily upgraded to provide APF outputs.

The recently developed intuitive approach to active digital filter (ADF) design represents a straightforward and efficient method for designing digital filters. This approach explores the similarity between digital integrators and operational amplifiers in analog filter design. By connecting digital integrators as signal followers, first-order ADFs are implemented. By inserting first-order ADFs into the feedback loop of another ADF, second-order or biquadratic ADFs (biquads) are created. Cascading multiple biquads allows the construction of higher-order filters. This paper, Part IV of the series, focuses on the design of active biquads as fundamental filtering stages in ADF design. A universal biquad architecture, capable of simultaneously generating low-pass, high-pass, band-pass, and band-tejection responses, is introduced and thoroughly examined. Special attention is given to the use of positive feedback as an approach to increase the Q-factor in bandpass biquads. Finally, the application of biquad notch filtering to suppress 50 Hz power-line interference in electrocardiogram signals is demonstrated.

Intuitive engineering is a valuable skill that empowers engineers to effectively tackle problems using straightforward methodologies and simple calculations, rather than relying solely on complex techniques and higher mathematics. Recently, a comprehensive foundation for intuitive active digital filter (ADF) design has been published in a two-part series. Part I introduced the fundamental principles of first-order ADFs, demonstrating their application in designing low-pass, high-pass, band-pass, and band-rejection filters. Part II further explored the design of higher-order lowpass filters (LPFs), serving as a guide for the design strategy of high-pass filters (HPFs). This article continues the series on ADF design by focusing on second and higher-order active HPFs. Similar to Part II, popular filter approximations, such as Bessel, Butterworth, and Chebyshev are discussed and compared to their analog Sallen-Key counterparts. Additionally, second-order active high-pass filtering of electrocardiogram (ECG) signals is demonstrated, indicating its better ability to suppress baseline drift from ECG signals.

Analog signals are usually digitized and further processed using various algorithms and procedures for digital data analysis. In digital signal processing (DSP), digital filtering is a crucial signal processing task that is used to enhance signal quality and increase the signal-to-noise ratio of a processed stream. This paper presents an original, intuitive, and easy-to-implement approach to the design of integratorbased closed-loop infinite-impulse-response filters, namely active digital filters. The approach is based on the feedback control theory and uses digital integrators to build stable negative feedback DSP systems that allow easy implementation of various filtering functions: low-pass, high-pass, etc. The filter cutoff frequency can be controlled using a single coefficient and adapted to the application needs. The presented active filters offer the simplest possible architecture and are well-suited for many DSP applications.

Bus voltage control is an essential issue in a DC microgrid (MG). In this paper, a decentralized composite controller (DCC) is proposed to unify two types of voltage controls, i.e., constant voltage mode and droop mode, and simultaneously realize global system large-signal stability of the MG. The main idea of the DCC is to partition the MG into dispatchable unit (DU) subsystems and the lumped load. A well-devised high gain observer is adopted to estimate the electrical coupling of a particular DU subsystem with other DUs and the load. Then, rather than dealing with the MG as a whole, the DCC is locally designed to offset the estimated coupling and stabilize the internal states of the DU subsystem. By doing so, each subsystem can be virtually decoupled from the MG and functions in an isolated fashion. When DU subsystems are interlinked, large-signal stabilization of the entire MG would be obtained by only guaranteeing the localized stability of individual subsystems. This stabilizing strategy has not been reported in the literature thus far. Relevant theoretical analyses are rigorously conducted by employing Lyapunov stability theorem. The effectiveness of the DCC has been verified by simulations. Experimentations show that the DCC enables faster system performance recovery and provides wider stability margin than the conventional PI controller.

In this paper, a new form of signal flow graph technique is used for modeling a bidirectional buck-boost converter and extracting the needed transfer functions. The signal flow graph method has a more simple process in comparison with other modeling techniques. The modeled converter is employed in energy management system of an electric vehicle. The energy system of the electric vehicle is composed of two energy sources; ultra-capacitor and battery pack. The proposed hybrid source has the advantages like: high energy density transmission and high instantaneous power output on the ultra-capacitor. Here, by using the mentioned converter, the energy management between the two sources is performed. Furthermore, the needed configuration for energy management system is presented and a proper controller based on obtained model for energy management in hybrid sources is proposed. Finally, the simulation results are brought to verify the precision of the proposed modeling technique and effec...

This paper presents the principles of three PWM control strategies, namely Harmonic Elimination Control Scheme, Current Hysteresis Control Scheme and Space Vector Control Scheme, which are used in the development of a lOOKVA IGBT wind turbine inverter. Based on the simulation and the output current waveform analysis, these three PWM control strategies are investigated and compared. The simulation results and certain field test waveforms are also provided in this paper.