Cristian Nichita

Modeling and optimal sizing of hybrid renewable energy system

This paper presents a new methodology of sizing optimization of a stand-alone hybrid renewable energy system. The developed approach makes use of a deterministic algorithm to minimize the life cycle cost of the system while guaranteeing the availability of the energy. Firstly, the mathematical modeling of the principal elements of the hybrid wind/PV system is exposed showing the main sizing variables. Then, the deterministic algorithm is presented and implemented to minimize the objective function which is equal to the life cycle cost of the hybrid system and finally, the obtained results are exposed and discussed.

Optimal sizing of stand-alone hybrid wind/PV system with battery storage

In this paper, a new methodology developed to design a hybrid wind/photovoltaic (wind/PV) system, is presented. Based on an optimization process using a deterministic algorithm, the developed methodology helps the authors to obtain the optimal number and type of PV panels, wind turbines and storage units ensuring that the system total cost is minimized while guaranteeing the permanent availability of energy to cover the load energy requirements. The hybrid system configuration and modeling are presented and the used deterministic algorithm (DIRECT algorithm) is described and implemented in MATLAB environment to optimize the hybrid wind/PV system.

Wind Turbine Simulation Procedures

The main goal of this work is to develop specific procedures for implementation in wind turbine simulators designed especially for small machines. Using blade element methodology, we establish procedures for the torque and power characteristics of a small wind turbine, where some physical construction parameters are known. The algorithm is developed for two simulation procedures, which differ by the parameter used for the set of characteristics (wind speed or pitch angle).

Modeling and optimization of wind/PV system for stand-alone site

In this paper a methodology for calculation of the optimum size of a stand-alone hybrid wind/photovoltaic (wind/PV) system is developed. The collection of six months of data of wind speed and ambient temperature recorded for every hour of the day and an estimate of solar irradiance were used. These data and manufacturers specifications on a wind turbine and a PV module were used to calculate the average power generated by the wind turbine and the PV module for each hour of the day. A deterministic algorithm is used to minimize the life cycle cost of the system while guaranteeing the satisfaction of the load. The mathematical modeling of the principal elements of the hybrid wind/PV system is exposed showing the main sizing variables. The deterministic algorithm is presented and implemented to minimize the objective function.

Performances study of direct coupled PM generator based small wind converters

This paper presents two wind converter structures based on an axial flux PM synchronous generator directly coupled to the wind turbine. For the generator model, a 2-D analytical solution of the Maxwells equations in the machine is used. A rectifier model is developed, taking into account the diodes commutation mode. The first topology which supplies a RL load is composed by a small wind turbine, PM generator, diode rectifier, and battery. A LC filter and a DC boost converter are introduced in the second topology, between the rectifier and the load. The wind converter configurations are analytically modelled, the simulations being performed in order to compare their performances for a given wind speed profile.

DC/DC converters control for embedded energy management — Supercapacitors and battery

This paper presents a study related to a more efficient energy management between battery and Supercapacitors (SC) for Hybrid Electric Vehicle (HEV) applications. This idea is due to the present trend in the field, knowing that the major drawback of the HEV is the autonomy problem. Thus, using supercapacitors and battery with a good energy management strategy improves the HEV performances. The originality of this paper is focused on DC-bus voltage and currents control strategy based on polynomial controller. This strategy is implemented in PIC18F4431 microcontroller for DC/DC converters control. For reasons of cost and available components (no optimized) such as the battery and power semiconductors (IGBT), the experimental test bench is designed in reduced scale. Through some simulations and experimental results the authors present an improved energy management strategy for HEV.

Improved sizing method of storage units for hybrid wind-diesel powered system

This paper deals with the segmentation of frequency domain to achieve DC bus stability by efficient design of storage and control principle. The wind energy disturbances measured on DC link are actively filtered by flywheel and battery storages to provide smoothed and secured behaviour of diesel engine. This is obtained by cascaded low pass filters applied to currents control when the dc link voltage is assumed constant. Thus, the templates, the degree of filters selectivity influence the sizing of storage units. This study focuses on the flywheel and battery sizing taking in to account wind energy path dynamics. Simulation results provide first step considerations for energy management tied to energy periodicity and system effectiveness.

Ultracapacitor integration for short‐term energy management in a hybrid system

Purpose – This paper aims to deal with the integration of energy storage devices (ultracapacitors) in wind energy applications to absorb the short terms fluctuations. The originality of this contribution is focused on energy management related to wind power frequency distribution between the hybrid sources. The robust and simplified control strategies are proposed and applied to DC‐DC converters without AC signals measurements. A novel MPPT method is introduced to operate the wind generator at the maximum power regardless of the wind speed variations. The fluctuating part of this power is mitigated by using a UC. The reference current of this last is obtained from a low pass filter. An innovative limitation algorithm of the UC voltage is proposed with aims to ensure optimal operation of the system. The control algorithms are implemented in a PIC18F4431 microcontroller. Some experimental results from this new approach are presented and analyzed.Design/methodology/approach – This study is organized accordin...

Efficient management of energy transfer in wind diesel hybrid system-battery and Ultracapacitors

This paper deals a new strategy for wind-diesel hybrid system energy improvement using Ultracapacitors (UC) and Battery. Energy management strategies are focused on the frequencies distribution of the wind generator current between UC and Battery. The developed control laws are based on the knowledge of the dynamic behavior of each source, in aim to prevent the diesel generator against the fluctuating currents while improving the batterys lifetime. The proposed strategies are implemented in the Microchip microcontroller (PIC18F4431) for experimental tests. Some experimental results obtained from this strategy are presented and analyzed.

A new method to define power and energy share in a DC link Hybrid wind-diesel powered system by means of storage and dual time-frequency approach

We show that frequency bands of interaction as well as dynamics of energy flow to the point of common coupling (PCC) lead to hybrid system design keys. Related to each power source and storage device, segmentation of frequency domain of the hybrid system is achieved by control strategy in time domain.