S. C. Ferreira

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.

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.

Adaptive Notch filter applied to hybrid active var compensator under nonsinusoidal and unbalanced conditions

This work proposes a new control strategy based on Adaptive Notch Filter applied to a Hybrid Active Var Compensator. The proposed strategy using Adaptive Notch Filters can correctly identify the reactive power flowing through the distribution system even under unbalance and nonsinusoidal conditions. The control strategy is simulated and implemented showing all its capability. Practical results are presented in order to prove the effectiveness of the topology improving the behavior of the capacitor bank normally used as reactive power compensator.

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.

Implementation of a grid-forming converter based on modified synchronous reference frame

Renewable resources power generation systems are mainly constituted by power converters. These converters can be controlled in several ways to execute different functions inside microgrids. Some of the converters cannot operate on isolated grids, that is, without connection to the electrical grid. Therefore, there are converters whose purpose is to provide a voltage reference so that other converters continue to deliver power independent of grid presence. These devices are called grid-forming converters and are usually constituted by a converter associated to an energy storage system. This paper presents the practical implementation of a grid-forming converter using the Modified Synchronous Reference Frame as base structure for the converter control. The developed control strategies are described along with experimental results of a single-phase 5 kVA prototype.

Hybrid active power filter applied to harmonic compensation of current-source type and voltage-source type nonlinear loads

The nonlinear loads can be divided in two distinct groups, according to its harmonic characteristics, called current-source type or voltage-source type nonlinear loads. The first one can be modeled as a harmonic current source and the second one as a harmonic voltage source. Traditional Shunt Active Filters are not effective for compensating harmonics from voltage-source type loads. This work presents the use of a Hybrid Active Filter for harmonic mitigation from both nonlinear loads. Practical results demonstrate that the Hybrid Active Filter is effective for harmonic compensation in any load condition, independent of its characteristics.

Smart impedance application on unbalanced harmonic mitigation in three-phase four-wire systems

This paper describes the newest hybrid active filter topology, the Smart Impedance, under unbalanced harmonic mitigation in three-phase four-wire systems. A three-phase modular approach permits the selective compensation of unbalanced harmonic components, no matter the current imbalance level or the harmonic sequence components flowing through the line. The Smart Impedance effectiveness highlights its capability of mitigating harmonics from voltage-source or current-source nonlinear loads emerging as an option to Parallel Active Filter or Parallel Passive Filter and classical hybrid active filter. The control algorithm is based on Proportional Resonant Controller. Practical results demonstrate the effectiveness of the Smart Impedance topology under unbalanced and different load conditions.

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.

Adaptive algorithm for real-time power quality measurement according to IEEE Std. 1459–2000

This paper introduces the development and implementation of an algorithm for real-time measurement of powers under sinusoidal, nonsinusoidal, balanced and unbalanced conditions. The power calculations are based on the definitions given by the IEEE Std. 1459–2000 and the adaptive filtering. The results are obtained in two ways: through simulation methods and practical implementation of the algorithm on DSP TMS320F2812. These results are compared and the efficiency of the algorithm is proven.