Toma Patarau

An energy converter method for battery cell balancing

Batteries packs made of series-parallel connected cells have developed a lot lately. These new solutions brought along with them some safety issues due to the possibility of overcharging or under-discharging of every individual cell that forms the pack. Balancing is one of the most important issues regarding battery management, as without it the individual cell voltages will draft apart over time and the packs total capacity will also decrease more quickly. This paper presents some theory behind the balancing methods developed so far and presents a new system used for cell balancing.

A Maximum Power Point tracker for a photovoltaic system under changing luminosity conditions

In order to increase the output efficiency of a PV energy system, it has to be forced to operate near the maximum power point (MPP). A photovoltaic (PV) system, including Maximum Power Point Tracking (MPPT) controller that extracts the maximum possible output power from the solar panel is built. Simulation and experimental results show that the proposed system, making use of several MPPT control algorithms (Perturb and Observe (P&O), Incremental conductance (INC), Fuzzy Logic), provides good tracking performance.

Single-stage low cost grid connected inverter in photovoltaic energy applications

Due to the rising fuel costs and growing worldwide demand for electricity, renewable energy sources become a necessity rather than a luxury. This paper presents an original control strategy for a buck-boost based converter used as a low cost inverter in a photovoltaic (PV) system. The main objective of the inverter is to harvest maximum power from the PV module and to inject it into the grid. The design of the converter is detailed and, together with the control method, a macro-model for the inverter is proposed. The macro-model is developed in order to have shorter simulation times and test various maximum power point tracking (MPPT) algorithms. Simulations and experimental results validate the proposed PV system.

Sizing photovoltaic-geothermal smart microgrid with battery storage interface

This paper presents a detailed sizing method of a hybrid photovoltaic-geothermal smart microgrid with battery storage. The goal is to find the optimal number of photovoltaic panels and batteries to identify the system which works without loss of power supply. To achieve this goal a PC interface was designed. This computer program is built around given meteorological data and consumer load characteristics, around fundamentals photovoltaic, storage capacity model, hourly radiation prediction algorithm, Loss of Power Supply Probability (LPSP) algorithm and Levelized Cost of Energy (LCE) algorithm. The lowest LCE suggests the optimal number of components. Through this application the user can change the location (setting the latitude and longitude data), modify the meteorological data, set the photovoltaic, geothermal and battery characteristics, and can analyze different cases easily.

Analysis and optimization of a geothermal, biomass, solar hybrid system: An application of PV*Sol software

The paper presents the techno-economic analysis and optimization of a hybrid renewable energy system composed of solar panels, batteries a geothermal generator and a biomass generator in the region of Oradea, Romania that is intended to supply a vegetable greenhouse. Based on the load specifications, after calculation and optimization, the minimum required sizes of the generators are: 14 solar panels, eight 230 Ah batteries and a minimum cumulated power of 2 kW for the biomass and geothermal generator. The renewable energy system is than optimized using PV*Sol software.

Comparison between digital average current mode control and digital one cycle control for a bridgeless PFC boost converter

This paper presents a comparison between two digital control methods for a boost power factor correction (PFC) converter based on the dynamic response at load changes and levels for the harmonic currents injected back on to the network. The power topology used is a bridgeless boost converter due to its high efficiency and low electromagnetic interferences (EMI) levels. The algorithms compared are average current mode control and one cycle control. A procedure to develop the digital control methods using software blocks is proposed starting from the standard analog controllers for PFC regulators.

A novel implementation of a Maximum Power Point Tracking system with digital control

This paper presents a novel Maximum Power Point Tracking(MPPT) method with digital control, together with an original Perturb and Observe (P&O) algorithm with variable step size. The step size calculation is independent of the slope of the power-voltage (P-V) characteristic of the solar panel. Simulation and experimental results are provided to show the efficiency of the system.

SCADA development for an islanded microgrid

The aim of this paper is to describe a SCADA tool for an intelligent microgrid. This application provides control over a smart microgrid that contains inverters, batteries and generators with power meters. In this system, the energy is generated by solar panels, a geothermal generator, a biomass generator and stored in batteries. The data is collected and represented on a PC Interface. The communication between the components and the application is accomplished through different protocols and standards. The connected devices can be detected, the inverters and power meter values, such as power and voltage, are read through the software application. These values, such as power, voltage, the speed of generators, can also be modified through this interface.

Microgrid model for fast development of energy management algorithms

The demand for electricity production increased in the last ten years leading to large investments and losses in the electricity grids. This forms the basis of decentralized hybrid energy system where the energy is produced in close proximity to the end user. This paper presents a simulation model for intelligent microgrids with distributed generation, also known as Smart Microgrids, focusing on the reduction of the simulation time in order to allow fast development of energy management algorithms. Photovoltaic panels and wind generators will be used as renewable energy primary sources and batteries as storage.

Digital control of bidirectional DC-DC converters in Smart Grids

The interest in the development towards intelligent microgrids which use renewable energy as primary sources has significantly increased in the last two years. The present paper examines and proposes a new digital control solution for bidirectional DC-DC converters. In order to control the converter in both directions the novel algorithm uses the current that charges and discharges the storage devices. The study treats and solves problems related to the battery charging algorithms and the power flow direction change.