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This paper presents the implementation of a simple and robust single-stage single-phase PV inverter with classical H-bridge inverter. A control algorithm for this converter is proposed integrating MPPT, DC link voltage regulation and inverter output current control in a cascaded control loop. The MPPT is a modified P&O with adaptive perturbation step and the output converter control is based on PR controllers. Both control algorithms are presented and explained in detail. Experimental results using a test bench built to emulate the behavior of a PV array are presented to demonstrate the control transient and steady state performance.

This paper presents a solution for the problem related to Partial Discharges (PD) source localization in oil- isolated transformers, using Genetic Algorithms. As known in literature, the simple PD detection is not enough to take a decision about intervening, so the localization is necessary to assess the risk and to plan corrective actions. The parameters extracted from the acoustic signals collected by piezoelectric sensors installed outside of the transformer, provide the correct position of PD. From parameters extracted of acoustic signals collected from piezoelectric sensors installed outside the transformer, the proposed algorithm provides the position where the PD is occurring. This work compares the performance of the method using Genetic Algorithms and those using iterative method, which is normally used to solve this problem. The conclusion describes the advantages of the proposed solution.

Distributed generation systems are growing, and their power converters and how they deal with the power flow when connected to the grid are key knowledge in this field. This work shows some technical and functional characteristics about a bidirectional converter, developed to assist the grid providing active or reactive power. The converter and control algorithms are presented, as well as a relation between the converter and synchronous generators, showing active and reactive power control capability. Simulation and practical results in a single-phase prototype demonstrate the system behavior.

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.

This work presents a comparison between two adaptive filters applied to harmonic and reactive power detection in power electronics conditioners. The objective is to demonstrate their ability of tracking the signal variations without the use of synchronization techniques, with fast dynamic response and low computational burden. The algorithms are simulated and implemented in DSP TMS320F2812 for power electronics appliances. Important aspects concerning the computational efficiency, convergence speed, steady-state error are analyzed, in order to present the advantages of adaptive filters over the synchronous reference frame and algorithms dependents on PLL techniques.

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.

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.

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.

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 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.

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.

This work proposes a new control strategy based on Adaptive Notch Filter applied to a Hybrid Active Var Compensator. The Hybrid Active Var Compensator is composed by a small rate active power filter in series with a capacitor bank. The objective is improving the behavior of the capacitor bank normally used as reactive power compensator. Under nonsinusoidal conditions the correct identification of the amount of reactive power needed is not an easy task. The proposed strategy using Adaptive Notch Filters can correctly identify the reactive power flowing through the distribution system even under nonsinusoidal conditions. The technique doesn't need any synchronization technique like a PLL. The control strategy is analyzed, simulated and practical results are presented in order to prove the effectiveness of the algorithm.

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.

This paper proposes a control strategy for Hybrid Active Series Power Filter (HASPF) based on a P+Resonant compensator. The proposed control uses Adaptive Notch Filter 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.

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.

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.

This paper presents the application of a neural adaptive notch filter for harmonic detection. The final objective of the strategy is improving the speed of convergence of the Neural Adaptive Filter and reduces the steady-state error. The Recursive Least Square (RLS) algorithm was used to adjust the coefficients. The new strategy proposed doesn't use a Phased Looked Loop (PLL) to generate the orthogonal input signals for the neural adaptive notch filter. These two signals are generated with Clarke transformation of the load current and then the two orthogonal signals are filtered. With this, the total transient response drops below one cycle of the fundamental frequency (60Hz). Simulations using Matlab/Simulink are presented to clarify the algorithm. Also practical implementation is performed using the DSP Texas Instruments TMS320F2812 in a shunt active power filters (SAPF) and the results depicted.

The properly behavior of power transformers is highly dependent of the insulation health. So, the insulation condition assessment can provide information to a system of diagnosis and prognosis, allowing for planning interventions at the appropriate time to avoid unexpected interruptions. This paper presents a technique that can detect moisture contamination in the insulating oil using acoustic signals of partial discharge. In this work, a piezoelectric sensor is mounted in a reservoir with insulating oils with different levels of moisture. A device to simulate partial discharges is immersed in those oils. The detected signals are processed using Discrete Wavelet Transform to extract time-frequency characteristics which are processing using the Principal Component Analysis in order to identify patterns of water content in insulating oil. The results are presented and the methodology has shown a very good technique to be implemented as on line monitoring system.

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.