No abstract

A low-power low-cost highly efficient maximum power point tracker (MPPT) to be integrated into a photovoltaic (PV) panel is proposed. This can result in a 25% energy enhancement compared to a standard photovoltaic panel, while performing functions like battery voltage regulation and matching of the PV array with the load. Instead of using an externally connected MPPT, it is proposed to use an integrated MPPT converter as part of the PV panel. It is proposed that this integrated MPPT uses a simple controller in order to be cost effective. Furthermore, the converter has to be very efficient, in order to transfer more energy to the load than a directly coupled system. This is achieved by using a simple soft-switched topology. A much higher conversion efficiency at lower cost will then result, making the MPPT an affordable solution for small PV energy systems.

No abstract

No abstract

Significant variation of the resource kinetic energy, in the form of wind speed, results in substantially reduced energy capture in a fixed speed wind turbine. In order to increase the wind energy capture in the turbine, variable speed generation (VSG) strategies have been proposed and implemented. However, that requires an expensive AC/AC power converter which increases the capital investment significantly. Consequently doubly-fed systems have been proposed to reduce the size of the power converter and thereby the associated cost. Additionally, in doubly-fed systems, at a fixed operating point (power and speed), power flow can be regulated between the two winding systems on the machine. This feature can be utilized to essentially minimize losses in the machine associated with the given operating point or achieve other desired performance enhancements. In this paper, a brushless doubly-fed machine (BDFM) is utilized to develop a VSG wind power generator. The VSG controller employs a wind speed estimation based maximum power point tracker (MPP") and a heuristic mode1 based maximum efficiency point tracker (MEW to optimize the power output of the system. The controller has been verified for efflcacy on a 1.5 kW laboratory VSG wind generator. The strategy is applicable to all doubly-fed configurations, including conventional wound rotor induction machines, Scherbius cascades, brushless doubly-fed machines, doubly-fed reluctance machines.

No abstract

No abstract

The grid faces a number of challenges related to large-scale integration of intermittent distributed generation (DG) such as photovoltaics (PV). Power quality challenges include voltage regulation issues, flicker, and frequency volatility. Operational challenges include the need for extension of the command-and-control infrastructure to millions of devices anticipated on the low-voltage (service) side of the distribution network. This paper presents an advanced grid-tied inverter controls concept designed to address such challenges. This controls concept is based on reproducing favorable characteristics of traditional generators that result in load-following tendencies, and is accordingly dubbed Generator Emulation Controls (GEC). Traditional generators are analyzed with specific focus on such favorable characteristics as inertial dynamics and controlled impedance. Details of GEC are then presented, and its implementation is outlined based on the evolution of conventional grid-tied inverter controls. This is followed by an examination of the system impact of GEC-operated devices. GEC allows DG inverters to perform voltage regulation support, reactive power compensation, and fault ride-through. GEC also allows DG inverters to form scalable inverter-based microgrids, capable of operating in grid-tied mode or separating and supporting an islanded load. Simulation results are presented to examine the impact on voltage regulation and power losses across a distribution feeder. Two experimental test beds are used to demonstrate voltage regulation support, transient suppression, and microgridding capabilities.