Radu Etz

A comparison between digital and analog control for a buck converter

This paper presents an approach of digital control with average current mode control. The model takes into account the non idealities of the components, the discrete time modeling of the Z transform, sampling, delays in the control loop and the quantization of coefficients for the control loop. First the analog compensation is made and then based on the poles and zeros, the bilinear function in Matlab is used to find the coefficients. The model is simulated in PSIM with step load current.

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.

Simulink test bench for a hybrid battery-supercapacitor power system

This paper presents a test bench for a hybrid power system composed of a Lithium-ion rechargeable battery and a supercapacitor. Using this test-bench the parameters and the functionality of the entire hybrid power system can be estimated. The purpose of the paper is to test the behavior of the complete system during high load variations. In a power system the advantage of battery storage consists in high charge/discharge efficiency with the condition that the charging/discharging cycles are carefully controlled. The high power demand in many applications with short power surges increases the battery stress, drastically affecting its life time and capacity. A method to reduce this stress is proposed in the paper by using a supercapacitor connected in parallel with the battery. A comparison between the proposed system and one using only a Lithium-ion battery is conducted and the results are presented.

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.

Optimal scheduling of an islanded microgrid based on minimum cost

In this paper, the optimal operation of a photovoltaic unit, a geothermal generator, a biomass generator and a storage system is determined by a mixed-integer linear programming algorithm. Modeling, control and optimal operation of intelligent smart islanded microgrids with renewable energy resources (RES) have gotten high attention in the past years. Optimal operation scheduling of the generators and the batteries is a crucial issue in these systems. Starting and stopping the generation units at the right time can maximize the systems performance, minimize the operation cost and ensure a more reliable power balance for the microgrid. A PC software was developed to determine these start- and stop-moments for each generator and the charge of batteries. This Supervisory Control and Data Acquisition (SCADA) system can ensure the optimal scheduling of the generation units and guarantees correct functioning of the equipment, focusing on the operation cost, the generation and control measurements. The results are presented in a GUI (Graphical User Interface).

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.