Ruben Barros Godoy

Differential-Evolution-Based Optimization of the Dynamic Response for Parallel Operation of Inverters With No Controller Interconnection

In this paper, the use of differential evolution (DE), a global search technique inspired by evolutionary theory, to find the parameters that are required to achieve optimum dynamic response of parallel operation of inverters with no interconnection among the controllers is proposed. Basically, in order to reach such a goal, the system is modeled in a certain way that the slopes of P- ω and Q -V curves are the parameters to be tuned. Such parameters, when properly tuned, result in systems eigenvalues located in positions that assure the systems stability and oscillation-free dynamic response with minimum settling time. This paper describes the modeling approach and provides an overview of the motivation for the optimization and a description of the DE technique. Simulation and experimental results are also presented, and they show the viability of the proposed method.

Multiple signal processing techniques based power quality disturbance detection, classification, and diagnostic software

This work presents the development steps of the software PQMON, which targets power quality analysis applications. The software detects and classifies electric system disturbances. Furthermore, it also makes diagnostics about what is causing such disturbances and suggests line of actions to mitigate them. Among the disturbances that can be detected and analyzed by this software are: harmonics, sag, swell and transients. PQMON is based on multiple signal processing techniques. Wavelet transform is used to detect the occurrence of the disturbances. The techniques used to do such feature extraction are: fast Fourier transform, discrete Fourier transform, periodogram, and statistics. Adaptive artificial neural network is also used due to its robustness in extracting features such as fundamental frequency and harmonic amplitudes. The probable causes of the disturbances are contained in a database, and their association to each disturbance is made through a cause-effect relationship algorithm, which is used to diagnose. The software also allows the users to include information about the equipments installed in the system under analysis, resulting in the direct nomination of any installed equipment during the diagnostic phase. In order to prove the effectiveness of software, simulated and real signals were analyzed by PQMON showing its excellent performance.

Voltage estimation in electrical distribution systems

The increasing demand for high power quality has increased the demand for power quality monitoring tools. The voltage performance monitoring for each feeder is one of the needs found by the utility companies. Since it is not economically viable to measure every single node in the system, it is necessary to use estimation techniques in order to get all needed information with a reduced the number of meters. These are basically interpolation techniques. Each interpolation provides different performance of estimations accordingly the application. In this work, it is proposed a non-linear non-parametric method which was found to get the best voltage estimates of feeders in relation to other more usual techniques. Comparative results for different methodologies in a hypothetic system are presented and discussed.

Three-phase Tri-State Current Source Inverter for photovoltaic energy stand-alone applications

This paper proposes the design of a Tri-State Boost Current Source Inverter with a Modified Space Vector Pulse Width Modulation. This converter is promising for many renewable energy applications. The Modified Space Vector PWM was created in order to determinate the converter state times and generate the switching signals, depending on the photovoltaic panel MPPT algorithm output and the modulation index. The Tri-State Boost CSI eliminates the RHP zero that is present in the Traditional Current Source Inverter by adding a freewheeling state. The partial experimental results show that this converter can operate as expected and is suitable for stand-alone situations that require high efficiency and reliability. The target application of the converter is to track the point which occur the maximum power transfer from the panel to the load.

Power flow optimization for grid connected inverter using evolutionary algorithm and additional control loop

In this work it is proposed to validate an evolutionary tuning algorithm in plants composed by a grid connected inverter. The optimization aims the tuning of the slopes of P-ω and Q-V curves so that the system is stable, damped and minimum settling time. Simulation and experimental results are presented to prove the feasibility of the proposed approach. However, experimental results demonstrate a compromising effect of grid frequency oscillations in the active power transferring. In addition, it was proposed an additional loop to compensate this effect ensuring a constant active power flow.

A straightforward closed-loop Wireless Power Transfer battery charger

Recent advances in Wireless Power Transfer (WPT) technology have allowed its application in numerous different fields. When employing loosely coupled coils to implement WPT systems, power transferred to the load tends to decrease as misalignment between antennas increases. In practical applications such as in electric vehicles (EV) wireless battery charging perfect coils positioning is hardly achieved without the use of position sensors. This paper presents a simple WPT system architecture with two closed-loops control algorithms that allow automatic power regulation up to a certain misalignment level. The proposed solution uses a small number of sensors and a simplex radio frequency communication channel to feed back voltage, current and power information from the secondary circuit to the primary side microcontroller.

A new microinverter topology for PV application with inductive power decoupling capability

An important trend in photovoltaic lines of research is the use of plug and play microinverters attached to the panel, allowing the so called AC module. However, these converters are subjected to high temperature and humidity. In order to improve reliability and achieve long lifetime, this work proposes a new topology, which provides inductive power decoupling and eliminates electrolytic and even film capacitors, using a single ceramic or mica capacitor. A thorough theoretical analysis of the topology is provided and simulation results prove its feasibility and advantages.

Procedure to match the dynamic response of MPPT and droop-controlled microinverters

Due to the absence of communication needs and great reliability, the droop-control technique is a great choice for controlling of inverters that are subjected to load sharing or to work in an islanded mode. On the other hand, current-controlled inverters are often used in grid-connected systems due to their fast response to power the implementation of maximum power point tracking (MPPT) algorithms to maximize the power extracted from these systems. However, the application of such algorithms in grid-connected droop-controlled systems is hampered by differences in the dynamic responses of the respective techniques. In this context, this study presents the development of a strategy that enables a push–pull converter controlled by MPPT and a low-power plug and play grid-connected inverter governed by droop control to operate stably even under variations in solar radiation. The goal is achieved based on the following two approaches: designing the dc-link capacitor properly and using a control loop in order to adapt the droop curves in accordance with the available input power. Theoretical analysis and experimental results have proven the viability of the approach.

Cost-effective photovoltaic water pumping system for remote regions communities

The work consists of the development of a cost-effective 480 W photovoltaic battery-less water pumping system. The main advantage of the system is the use of a three-phase induction motor for the water pump drive, which presents many advantages compared to commonly used direct current motors. The system is composed of two 240 Wp solar panels, a three-phase converter, a ½ hp water pump, hydraulic and mechanical components. The electronic stage involves a resonant DC-DC converter in series with voltage source three-phase inverter. The embedded control for the system output power maximization is digital, dsPIC-based, responsible for the algorithms of MPPT (maximum power point tracking) and scalar speed control of the motor. The work shows an analysis of the involved structures, experimental results, costs evaluation and performance of the system. The feasibility of the system is evaluated in a remote region school located at the Brazilian Pantanal wetlands.

MPP tracking for grid connected inverters controlled by drooping curves

This work presents a control methodology in order to enable connecting photovoltaic generators to the grid in such a way that the modules are always going to operate in their maximum power point (MPP). The work uses the droop control technique together with a MPPT method. The integration of these methods presents two crucial points. The first one is how the P-ω curve is modified according to the photovoltaic panel output power and the DC-DC converter output voltage. The second point is the establishment of a DC-link connecting the DC-DC converter to the inverter. Its goal is cancelling the impact caused by the different dynamic response of the methods. This work presents several advantages for environment and reliable and safe power system growing. The experimental results verify great tracking, stability and reliability, even during irradiation transients.