Abstract: This paper deals with a shunt active filter which will be installed by an electric utility, putting much emphasis on the control strategy and the best point of installation of the shunt active filter on a feeder in a power distribution system. The objective of the shunt active filter is to damp harmonic propagation, which results from harmonic resonance between many capacitors for power factor improvement and line inductors in the feeder, rather than to minimize voltage distortion throughout the feeder. Harmonic mitigation is a welcome "by-product" of the shunt active filter, which comes from damping of harmonic propagation. This paper concludes that the shunt active filter based on detection of voltage at the point of installation is superior in stability to others, and that the best site selection is not the beginning terminal but the end terminal of the primary line in the feeder. Computer simulation is performed to verify the validity and effectiveness of the shunt active filter by means of an analog circuit simulator, which is characterized by installing it on a feeder of a radial distribution system in a residential area.

Abstract: This paper presents a new control scheme for a parallel hybrid active filter system intended for harmonic compensation of large nonlinear loads up to 50 MVA, to meet IEEE 519 recommended harmonic standards. The active filter is small rated, 2%-3% of load kilovoltampere rating. The control scheme is based on the concept of synthesizing a dynamically variable inductance, and its usefulness is demonstrated for an active filtering application. A synchronous reference frame (SRF) controller implements the dynamically varying negative or positive inductance by generating active filter inverter voltage commands. This variable inductance controller parallel hybrid active filter system can selectively synthesize multiple "active inductances" at dominant harmonic frequencies without affecting passive filter impedances at all other frequencies. This controller also provides a "current limiting" function to prevent passive filter overloading under ambient harmonic loads and/or supply voltage distortions. Three implementation variations of a parallel hybrid active filter system are presented. This paper also proposes the use of power factor correction capacitors as low cost passive filters for a parallel hybrid active filter system, which are controlled to provide either single or multiple tuned harmonic sinks and to increase cost effectiveness for high power applications. Simulation results validate the proposed variable inductance controller operation for mistuned passive filters.

Abstract: By putting an LC filter between a PWM voltage source inverter and induction motor, standard industrial motors can also be utilized for adjustable speed drive applications. In this paper, the application of an LC filter to medium voltage motors fed by inverters with switching frequencies below 1000 Hz is described. For different filter topologies, rules for the electrical design are discussed as well as solutions for the stability problem. Also discussed are solutions against common mode voltage stress on the motor terminals. An example shows the implication of the filter on the minimum inverter power which has to be installed to feed a given motor.

Abstract: A new, substantial improvement of the hysteresis current control method for voltage source inverters is presented. A simple and fast prediction of the hysteresis band is added to a linearized version of the phase-locked loop control, thus ensuring constant switching frequency and tight control of the position of modulation pulses. This allows high accuracy in tracking highly distorted current waveforms and minimizes the ripple in multiphase systems. The implementation of this technique is very simple and robust, employing only a small number of conventional inexpensive analog and logic components. It does not require trimmings or tunings, giving the control the capability to adjust itself to the different operating conditions. The proposed method is compared with the most diffused modulation techniques, demonstrating its superior performance in responding to the most demanding conditions met in active filters. The behavior of the method has been fully verified by simulation and by experimental tests.

Abstract: This paper presents the control circuit of a shunt active power filter based on the instantaneous active and reactive current i/sub d/-i/sub q/ method The presented method is compared with the instantaneous active and reactive power p-q method under several mains voltage conditions and for different harmonic injection highpass filters The i/sub d/-i/sub q/ method as an excellent harmonic compensation performance and presents the advantage of being frequency-independent The DC voltage regulation system is analysed and its synthesis is performed Extensive simulation results are used to show the stability of the voltage regulation system and to establish the superior performance of i/sub d/-i/sub q/ method based compensator

Abstract: This article details a new transfer function approach in passive harmonic filter design for industrial and commercial power system applications Filter placement along with six common filter configurations are presented Harmonic impedance, voltage division and current division transfer functions are derived and used in a practical filter design procedure that incorporates IEEE-519 distortion limits directly into the design and component specification process A simple four-step filter design procedure is outlined and used in a variable speed motor drive pumping plant application

Abstract: Some novel multifunction biquadratic filters with voltage gain, each of which employs four current conveyors, two grounded capacitors, and three-five resistors, are presented. Each proposed circuit offers the following advantageous features: realization of different biquadratic filter signals from the same configuration, no requirements for component matching conditions, employment of only two grounded capacitors which are ideal for integration, orthogonal control of /spl omega//sub 0/ and Q and low sensitivities.

Abstract: In this paper, the impact of the inverter modulation strategy on common mode conducted emissions is addressed. Whereas typically passive filter designs are used to mitigate the common mode current produced by the inverter, active filtering is proven to greatly reduce common mode conducted emissions due to the modulation of the power converter. A new space vector modulation strategy is presented for common mode EMI reduction in three- and four-phase DC/AC power converters.

Abstract: A new technique for IIR multiple notch filter design is proposed. The specification of notch filter is first transformed into that of allpass filter. Then, we develop an effective approach to design this desired allpass filter. The realization of proposed notch filter is equivalent to the realization of an allpass filter. Due to the mirror-image symmetry relation between the numerator and denominator polynomials of allpass filter, the notch filter can be realized by a computationally efficient lattice structure with very low sensitivity. Moreover, some examples are presented to examine the effectiveness of proposed method.

Abstract: In high frequency inverter fed AC motor systems, high frequency leakage current generated by high dv/dt at switching times flows to the ground wire through the stray capacitor between motor windings and core. This paper proposes an active EMI filter to compensate common mode current using high frequency transistors as active elements and a high frequency common mode CT. It works just as a power active filter in the harmonic compensation in the power system. The leakage current is actively suppressed to under 1/50 of the uncompensated circuit. The proposed method is also effective to decrease the EMI more than 40 dB/spl mu/V.

Abstract: Inductorless bandpass filters have in the past been realized using all-pass circuits based on op amps. This work replaces the op amps with integrable fixed gain amplifiers to create the bandpass filter. Values of Q exceeding 100 with resonant frequencies approaching 50 MHz can be achieved with an integrated circuit implementation. A method to reduce the sensitivity of Q with respect to temperature is reported.

Abstract: A simple and low-cost control strategy for active power filters implemented with pulsewidth modulation voltage-source inverters (PWM-VSIs) connected in cascade is presented and analyzed in this paper. The principal component of the control circuit is an INTEL 8031 AH microcontroller, which generates the current reference waveforms and respective switching patterns for each inverter. The switching pattern is obtained by using a vector control technique. The proposed active power filter consists of two PWM-VSIs, connected in cascade, each operating at a different switching frequency. This paper presents the proposed control strategy in terms of principles of operation, circuit design and implementation. Finally, predicted results are verified experimentally on a 10 kVA breadboard model.

Abstract: A new current-mode (CM) universal active filter with single-input and three-outputs (SITO) employing only four CCIIs and a minimum number of passive components is presented. The proposed filter based on an RLC shunt circuit, has a good sensitivity performance and achieves the desired filter characteristics without any component matching.

Abstract: A high power amplifier system includes an on-line adaptive predistorter for generating predistorted complex data signals to a high power amplifier in response to receiving incoming complex data signals from a remote source. The predistorted complex data signals enable the high powered amplifier to output signals corresponding to the incoming complex data signals. The amplifier system includes an off-line adaptive predistorter which has an adaptive parametric forward filter for combining predistorted complex data signals and demodulated complex data signals, produced from the output of the high power amplifier, to produce an optimized forward amplitude filter that emulates the forward amplitude response of the amplifier, and an optimized inverse phase filter that emulates the inverse phase response of the amplifier. An adaptive parametric inverse filter combines random amplitude data and the optimized forward amplitude filter of the amplifier to produce an optimized inverse amplitude filter that emulates the inverse amplitude response of the amplifier. An off-line to on-line converter combines the optimized inverse amplitude filter, the optimized inverse phase filter and exemplary complex data to produce the predistorted complex data utilized by the on-line adaptive predistorter for generating the predistorted complex data signals.

Abstract: A dual band filter network for a radio communication apparatus is provided. The network has an antenna (212) for receiving and transmitting signals from a first frequency band and a second frequency band. The network has a first duplex pair (202) including a first transmit filter (204) including a first passband and stopband. The first duplex pair (202) also includes a second receive filter (206). The first filter (204) presents a consistent phase in the second passband due to the wide frequency separation between the first filter (204) and the second filter (206). The network has a second duplex pair (202') with similar characteristics as the first duplex pair (202). The network also has a switching circuitry (210) controlled by a switch control voltage (214) for selecting the appropriate filter circuitry. The network can be provided in a small sized, low cost package that also offers improved insertion loss performance.

Abstract: A novel process by which the utilization of a central processing unit (CPU) in performing filtering operations can be reduced by shortening the filter's length thus degrading the performance of the system down to a predetermined level or threshold. If the filter is adaptive (150), the process waits for the filter to converge (152). Then, the quality criteria is measured (154). If the measured quality criteria is above the quality threshold (158), then M taps are removed from the filter (156) and the process returns to step 150. If the measured quality criteria is below the threshold, M taps are added back to the filter (160) and the process terminates.

Abstract: The design and performance of a rail-to-rail low-voltage CMOS fifth-order elliptic low-pass GM-C filter for baseband mobile communication are presented. The operational transconductance amplifier (OTA) used in this filter is a low-voltage rail-to-rail voltage-to-current converter (V-I converter). In this V-I converter, an N-type V-I converter cell is connected in parallel with its counterpart, a P-type V-I converter cell, to achieve common-mode (CM) rail-to-rail operation. Two maximum-current selecting circuits and an output current subtraction circuit are utilized to generate constant-g/sub m/ output currents for this OTA. This fifth-order elliptic low-pass GM-C filter operates at a supply voltage of 3 V and has a cutoff frequency of 280 to 405 kHz. It provides up to 700 mV/sub pp/ output with 1% total harmonic distortion (THD), dissipates 2.48 mW at V/sub cm/=1.5 V, and occupies 1.62 mm/sup 2/ in a 1.2-/spl mu/m CMOS technology.

Abstract: This paper addresses the structure generation, analysis and synthesis of multiple loop feedback OTA-C filters. A systematic approach is proposed for all-pole filters, and the generation and design of minimum component structures are extensively exemplified. Two general methods for transmission zero realization are also suggested and two architectures with simple design formulas are illustrated. Using the theory many new interesting configurations can be produced alongside some known structures. All the filter architectures contain only grounded capacitors and all internal nodes in canonical realizations have a grounded capacitor. A general method for sensitivity analysis of the structures is formulated. Numerical design examples and simulation results are also presented. The essence of the theory is the establishment of the relationship between the filter structure and the feedback matrix, which makes systematic structure generation and general design equation formulation possible.

Abstract: A hybrid parallel active/passive filter system (30) is provided which provides line power harmonic isolation and compensation for power systems connected to high power non-linear loads (38). The hybrid filter (30) includes a passive filter (50, 52) connected in series with an active filter inverter (54, 56). The active filter inverter (54, 56) is controlled to generate inverter voltages such that the filter terminal voltage tracks the supply voltage harmonics at a selected dominant harmonic frequency to regulate the supply current harmonics to zero. A synchronous reference frame (SRF) based controller is used to generate harmonic inverter voltage commands based on measured supply current values. A feed forward command signal generator may be used to improve the response of the control system. The active filter inverter (54, 56) is preferably implemented as a square-wave inverter. The active filter inverter DC bus is controlled to achieve power balancing and to provide real power to compensate for losses of the inverter.

Abstract: The high requirement of rated power of an active power filter leads to high costs and limits the range of operation especially for high voltage applications. To overcome these problems, a combined system of a passive filter, using only one LC filter tuned to the lowest typical line current harmonic, and a shunt active power filter, sharing the filter capacitor to be decoupled from the fundamental line voltage, is proposed. These features strongly decrease the rated power of the active filter which is controlled only to suppress the harmonics of higher order and to eliminate resonance effects between the line impedance and the passive filter.

Abstract: A multiple-point equalization filter using the common acoustical poles of room transfer functions is proposed. The common acoustical poles correspond to the resonance frequencies, which are independent of source and receiver positions. They are estimated as common autoregressive (AR) coefficients from multiple room transfer functions. The equalization is achieved with a finite impulse response (FIR) filter, which has the inverse characteristics of the common acoustical pole function. Although the proposed filter cannot recover the frequency response dips of the multiple room transfer functions, it can suppress their common peaks due to resonance; it is also less sensitive to changes in receiver position. Evaluation of the proposed equalization filter using measured room transfer functions shows that it can reduce the deviations in the frequency characteristics of multiple room transfer functions better than a conventional multiple-point inverse filter. Experiments show that the proposed filter enables 1-5 dB additional amplifier gain in a public address system without acoustic feedback at multiple receiver positions. Furthermore, the proposed filter reduces the reflected sound in room impulse responses without the pre-echo that occurs with a multiple-point inverse filter. A multiple-point equalization filter using common acoustical poles can thus equalize multiple room transfer functions by suppressing their common peaks.

Abstract: This paper presents a technique for single phase power factor correction of nonlinear loads employing an active power filter. The current control strategy is the same used in the boost pre-regulator, which is the average current mode technique. The paper focuses on the design methodology and the analysis of the control strategy which allows the compensation of harmonics and phase displacement of the input current, for single and multiple nonlinear and linear loads. Simulation results of an active filter controlling a single load, which consists of a 1600 W rectifier with a capacitive filter, and a multiple load, which consists of a 800 W rectifier with a capacitive filter and a 800 W AC chopper, are provided. Experimental results of an active filter controlling a 400 W rectifier with a capacitive filter, a 800 W AC chopper and a 580 W multiple load, which consists of a rectifier with a capacitive filter and an AC chopper, are presented.

Abstract: Indexing terms: Active power filter, Harmonics, Sliding mode controller, Reactive power, Neutral current Abstract: The paper presents an active power filter (APF) to eliminate harmonics and to compensate reactive power and neutral current of three-phase four-wire symmetrical and unbalanced nonlinear loads. A set of three single- phase insulated-gate bipolar transistor (IGBT)- based voltage source inverter (VSI) bridges with a common DC bus capacitor is used as the APF. A sliding mode controller (SMC) over the average DC bus voltage is used for the control. A hysteresis rule based carrierless pulse width modulation (PWM) current control is employed to generate the gating signals to the switching devices. A set of three single-phase diode bridge rectifiers with capacitive-resistive loading is used for nonlinear loading. The simulation results show that the APF is capable of compensating reactive power, neutral current and load unbalance and reducing the harmonic level below the limit specified in IEEE-519 standard.

Abstract: In this paper, a new comb filter design method using fractional sample delay is presented. First, the specification of the comb filter design is transformed into that of fractional delay filter design. Then, conventional FIR and allpass filter design techniques are directly applied to design fractional delay filter with transformed specification. Next, we develop a constrained fractional delay filter design approach to improve the performance of the direct design method. Finally, several design examples are demonstrated to illustrate the effectiveness of this new design approach.

Abstract: This paper investigates parametric and catastrophic fault coverage of the oscillation-test strategy. A set of definitions to evaluate the efficiency of a test technique and to quantify the parametric fault coverage is therefore introduced. The oscillation-test strategy is a low-cost and practical test method which is very efficient for built-in self-testing of mixed-signal integrated circuits. Active analog filters are used as test vehicle and therefore design for testability techniques to convert them to oscillators have been presented. Discrete practical realizations and extensive simulations based on CMOS 1.2 /spl mu/m technology parameters affirm that the test technique presented for active analog filters ensures high fault coverage and requires a negligible area overhead.

Abstract: Characteristics of the instantaneous active/reactive powers and zero-sequence current/voltages are analyzed in three-phase four-wire systems. Control strategy for an active filter without energy storage components is proposed on the basis of mapping matrices. It can compensate for the zero-sequence current, irrespectively of whether or not a zero-sequence voltage exists in three-phase four-wire systems.

Abstract: The current-controlled second order multifunctional filter is described. It uses only three current controlled conveyors and two grounded capacitors. Three types of current transfers, highpass, bandpass, and lowpass, can be acheived simultaneously and both /spl omega/0, and Q are electronically adjustable. The circuit can also be modified to be a current controlled oscillator. The simulated results are illustrated.

Abstract: A digital loop filter in the carrier-recovery loop of a digital communications receiver. The recovery loop is a PLL that keeps the receiver oscillator locked to the carrier wave, and the loop filter provides control over the PLL's frequency response by conditioning an error signal that is fed back to the receiver oscillator. In the present invention, the error signal is a digital signal, and the loop filter is implemented in digital hardward. With this implementation the characteristics of the loop filter are determined by logic design rather than by physical features of analog components, thereby giving this filter a more precise function than one with analog integrators. This implementation is also immune to the low tolerances typical of the manufacturing process for analog devices (especially on monolithic circuits), and is more easily adjusted than its analog counterparts. Two gain coefficients characterize the loop filter in the present invention. These gain coefficients are chosen to be powers of two, simplifying the process of multiplying them with the digital error signal. The gain coefficients are read from a memory, making the loop filter easily programmable. By changing the gain coefficients during operation of the receiver, the carrier-recovery loop can be placed in one of the several operating modes, including acquisition, tracking, and hold. The receiver can be configured with the appropriate values of the gain coefficients for each operating mode during the initial assembly and during subsequent reconfigurations.

Abstract: A new current-mode universal filter is proposed. The filter uses only operational amplifiers and operational transconductance amplifiers (OTAs) and can realise lowpass, highpass, bandpass, notch and allpass responses without changing circuit topology. The parameters /spl omega//sub 0/, /spl omega//sub 0//Q/sub 0/, and the gain can be electronically tuned by adjusting the bias currents of the OTAs. The proposed circuit has low sensitivity.