L. E. Borges da Silva

Smart impedance: Expanding the hybrid active series power filter concept

Hybrid active series power filters, as originally proposed in the literature, presents a way to improve the physical limitation of tuned passive filters. However, these improvements are restricted to a single filter parameter, i.e., quality factor or tuned factor. To overcome these limitations, a hybrid system composed by active impedance, capacitor bank and appropriated control strategy, called smart impedance, is proposed. The system completely eliminates the necessity of the classical passive filter tuning procedure, which requires capacitor/inductor association for each frequency. All tuning issues are performed electronically. The proposed topology is able to manipulate, at the same time, the displacement power factor, harmonic current frequency compensation (single or multiple), quality factor and tuned factor. Practical results demonstrate the smart impedance performance and its interaction with the power system under multiples harmonics frequencies along with the displacement power factor compensation. The proposed system is simpler and more efficient than those reported in the literature. The control algorithm is executed using the DSP TMS320F2812 and the inverter switching frequency is 20 kHz.

Auto-Associative Neural Network Based Sensor Drift Compensation in Indirect Vector Controlled Drive System

The paper proposes an auto-associative neural network (AANN) based sensor drift compensation in an indirect vector-controlled induction motor drive. The feedback signals from the phase current sensors are given as the AANN input. The AANN then performs the auto-associative mapping of these signals so that its output is an estimate of the sensed signals. Since the AANN exploits the physical and analytical redundancy, whenever a sensor starts to drift, the drift is compensated at the output, and the performance of the drive system is barely affected. The paper describes the drive system, gives a brief overview of the AANN, presents the technical approach, and then gives some performance of the system demonstrating validity of the approach. Although current sensors are considered only in the paper, the same approach can be applied to voltage, speed, torque, flux, or any other type sensor.

PLL-less control strategy applied to Hybrid Active Series Power Filter

A simple control strategy for the Hybrid Active Series Power Filter (HASPF) based on P+Resonant compensators is presented. The structure allows the compensation of multiple selective harmonic components simultaneously. No mains voltage synchronization techniques, like a PLL, nor any voltage sensing are demanded. The entire control algorithm is performed directly in the abc frame. Practical results are presented to demonstrate the control efficacy.

Harmonic detection with LMS adaptive notch filter and transient detection

This paper presents the application of the adaptive filters for harmonic detection in shunt active power filters. Improve the transient response time of the adaptive filter is the final objective of the strategy. The Least Mean Square (LMS) algorithm was used to adjust the coefficients of the adaptive notch filter. An algorithm based on the Clarke Transformation was used to detect the load current amplitude transients and then modify the step-size value. Simulations using Matlab/Simulink are presented to clarify the algorithm. Also practical implementation is performed using the DSP Texas Instruments TMS320F2812 and the experimental results depicted.

Active impedance: A closed-loop approach on hybrid active series power filter

Hybrid active series power filters, as originally proposed, presents a way to improve the physical limitation of tuned passive filters. However these improvements are restricted to a single filter parameter: quality or tuned factor. To overcome these limitations, the active impedance has been proposed. By handling, at the same time, the quality and the tuned factor the topology is able to compensate multiple harmonic current just by using a single tuned passive filter. In this paper the details about active impedance concept are demonstrated. An appropriated control strategy based on P+Resonant Controller is used to implement the active filter complex gain. The performance of the hybrid active filter based on active impedance under multiples harmonics frequencies is investigated and confirms to be more efficient than those reported in the literature. The control algorithm is executed using the DSP TMS320F2812 and the inverter switching frequency is 20 kHz.

Improving the convergence time of adaptive notch filters to harmonic detection

This paper presents the application of adaptive notch filters for harmonic detection in shunt active power filters (SAPF). The orthogonal input signals to the adaptive notch filter are generated using the Clarke transformation of the load currents in such way that the Phased Looked Loop (PLL) is not necessary any more. The least mean square (LMS) and recursive least square (RLS) algorithms were used to adjust the coefficients of the adaptive notch filter. The final objective of the described strategy is to improve the speed of convergence of the adaptive notch filter, reducing the steady-state error and the transient response. All these features are very important to real time applications in active power filters. Simulations using Matlab/Simulink are presented to clarify the algorithm. Also, the implementation of the technique in a shunt active power filter is performed using the DSP Texas Instruments TMS320F2812, and the experimental results depicted.

Application of adaptive filters in active power filters

This paper presents a new idea applied to adaptive filters for harmonic detection in shunt active power filters. Improve the speed of convergence of the adaptive filter and reduces the steady-state error are the finals objectives of the strategy. Two cases are presented and discussed, one with a Finite Impulse Response (FIR) adaptive filter with 32 coefficients and another with an adaptive notch filter. The Least Mean Square (LMS) algorithm was used to adjust the coefficients in the both cases. An algorithm based on Coulon oscillator principle was used to determine the load current amplitude and then modify the step-size value. Simulations using Matlab are presented to clarify the algorithm. Also practical implementation is performed using the DSP Texas Instruments TMS320F2812 and the experimental results depicted.

STATCOM based on Modified Synchronous Reference Frame

This work presents the implementation of a single phase STATCOM based on the Modified Synchronous Reference Frame, an adaptation of the standard three-phase Synchronous Reference Frame applied to single-phase systems. The structure is able to compensate the reactive power flowing through the line, adjusting the displacement power factor and also acting on line voltage regulation. The proposed control algorithm is described and practical results are presented for a single phase prototype to validate the effectiveness of the developed system.

PLL-less control for hybrid active impedance

This work describes a PLL-Less control algorithm for the hybrid topology composed by a capacitor bank in series with an active impedance. This topology, named Smart Impedance, can be used in many applications. Hybrid Active Power Filter is one of these applications, where selective or simultaneous compensation of multiple harmonic components is possible. The control strategy uses the Proportional Resonant Compensators technique to achieve the desired behavior. The proposed algorithm totally eliminates the need for voltage synchronization as the resonant controller keeps track of the system current without the call for a PLL. The control algorithm is performed directly in the abc frame and practical results are presented to demonstrate the control performance and dynamics.

A control strategy for hybrid series active power filter based on resonant compensators

This paper proposes a control strategy for Hybrid Active Series Power Filter (HASPF) based on a P+Resonant compensator. The proposed control uses Modified Synchronous Reference Frame to isolate the harmonic content of the source current and a P+Resonant regulator to calculate the harmonic voltage signal necessary to properly tune the hybrid branch. This control strategy ensures multiple frequencies tuning by using only one passive filter. The details of the control algorithm and the design procedure are presented. Experimental results using a single-phase HASPF prototype confirm the effectiveness of the suggested approach. The control algorithm is executed in a DSP TMS320F2812 and the inverter switching frequency is 20 kHz.