1.Improved performance low-cost incremental conductance PV MPPT technique
Improved performance low-cost incremental conductance PV MPPT technique
Variable-step incremental conductance (Inc.Cond.) technique, for photovoltaic (PV) maximum power point tracking, has merits of good tracking accuracy and fast convergence speed. Yet, it lacks simplicity in its implementation due to the mathematical division computations involved in its algorithm structure. Furthermore, the conventional variable stepsize, based on the division of the PV module power change by the PV voltage change, encounters steady state power oscillations and dynamic problems especially under sudden environmental changes. In this study, an enhancement is introduced to Inc.Cond. algorithm in order to entirely eliminate the division calculations involved in its structure. Hence, algorithm implementation complexity is minimized enabling the utilization of low-cost microcontrollers to cut down system cost. Moreover, the required real processing time is reduced, thus sampling rate can be improved to fasten system response during sudden changes. Regarding the applied stepsize, a modified variable-step size, which depends solely on PV power, is proposed. The latter achieves enhanced transient performance with minimal steady-state power oscillations around the MPP even under partial shading. For proposed technique’s validation, simulation work is carried out and an experimental set up is implemented in which ARDUINO Uno board, based on low-cost Atmega328 microcontroller, is employed.
2. Decentralized Power Management in a Hybrid Fuel Cell Ultra capacitor System
Decentralized Power Management in a Hybrid Fuel Cell Ultra capacitor System
This paper addresses decentralized control of a hybrid energy system consisting of a fuel cell (FC) and an ultra capacitor. Separate controllers are developed for the FC and the ultra capacitor for power management rather than one central controller. Explicit communication between controllers, such as exchange of locally sensed information, is absent. The former operates the FC in a load-following mode, while attenuating transient fluctuations in fuel utilization. The latter allows the ultra capacitor to be used as an energy buffer. The paper proposes a simple energy-conservation-based approach where the FC controller estimates the energy gap that is compensated for by the capacitor, based on its own transient response history. Accordingly, it modulates its own output power. The capacitor control, in turn, imparts robustness to the collective performance of the controllers by either dissipating excess energy or regulating the load voltage. Together, synergistic power management is achieved within a decentralized framework. An experimental test stand is developed to validate the approach and experimental results are provided. This paper considers one power source and one energy storage element, and further research must be done to translate this approach to power networks.
3.A New Bidirectional DC-DC Converter for Fuel Cell, Solar Cell and Battery Systems
A New Bidirectional DC-DC Converter for Fuel Cell, Solar Cell and Battery Systems
This paper describes a new zero voltage switching (ZVS) bidirectional DC-DC converter (BDC) module. Compared to existing bidirectional DC-DC converter (BDC) modules for the same application, the new BDC module has the advantage of high efficiency, high power density and isolation. These advantages make the new BDC promising for medium and high power fuel cell, solar cell and battery applications where high power density, high efficiency, high reliability and lightweight power converters are needed. A real world implementation of 384 V to 48 V and 48 V to 384 V BDC is described, implemented and simulated using existing old components and proposed new power components for power level up to 1.65 kW. A new BDC provides a +13.5% increase in efficiency at 10% load, a +3.4% increase at 50% load and a +1.5% increase at 100% load in both forward and backward mode and more than double power density.
4.Optimized Resource Management for PV-Fuel Cell Based Micro grids using Load Characterizations
Optimized Resource Management for PV-Fuel Cell Based Micro grids using Load Characterizations
Maintaining a reliable and cost effective operation in micro grids has significant importance. One factor required for optimal operation of the micro grid is to keep a certain energy reserve without unnecessary cost to satisfy load variations. In this paper, an optimal reserve assessment of photovoltaic and fuel cell based micro grids are investigated while considering reliability and economic aspects. A typical residential load is predicted to introduce an optimal power sharing approach, and accordingly, to achieve reliable and cost effective system operation. Load sharing between sources in micro grids affects the cost, and also affects the source’s ability in responding to load variations. A nonlinear frequency droop scheme is then used as a tool to achieve the optimization objectives such that the operating cost is minimized without jeopardizing the micro grid’s ability of responding to sudden load variations. Presented results confirm the validity of the power sharing approach and verify its effectiveness and feasibility.