Search

Recently, the danger of a long blackout is discussed in Europe. Blackouts can be caused by failures in the energy distribution, errors in large power plants or even cyber-attacks. This can lead to a chain reaction and a disintegration of the mains. Longer blackouts have an extreme impact on the economy as a whole and on local households. Therefore, a small local grid at home which can supply the most important loads over some time has garnered increasing interest. With a small direct current (DC) grid, critical loads such as for deep freezers and refrigerators can be supplied, and some LED lights can be used in the evening or at night. Solar generators (panels) can be used to charge energy storage devices, e.g., batteries. A DC grid can not only be used in the case of an emergency, but can also be used to reduce energy consumption out of the public mains and reduce energy bills. The architecture of the household emergency DC grid is discussed; suggestions for batteries are given; two simple chargers, based on DC-DC-converters like the Buck (step-down) and on the Boost (step-up) converters, are shown; dimensioning suggestions are given; and simple, robust controllers, a P-controller with disturbance feedforward and a hysteresis controller, are treated and tested via simulations. The goal of the paper is to show a simple autonomous home energy system without an external fieldbus, LAN or internet connection with special focus on simple charger topologies. [ABSTRACT FROM AUTHOR]

A high-efficiency dc-to-ac inverter for stand-alone and direct ac mains connection is described. This structure uses only off-line switches to generate the ac voltage. Due to safety reasons, the input voltage (e.g., the voltage of solar cells or batteries) is limited. Therefore, high currents on the primary side are necessary to obtain the required output power. The overall efficiency of the inverter depends to a high degree on the number of switching elements in the current path. The structure described here has only one active switch in the main path. This can he obtained by applying a diode with controlled turn-off capability (like a thyristor or other derivatives). High duty cycles (d near one) of the main switch at high currents lead to low duty cycles (1-d near zero) of the switchable diode. For that reason, a series connection of two active switches in the main path has to be avoided. The new inverter leads to improved efficiency and is therefore well suited for solar and renewable energy as well as for aerospace applications. The improvement of the efficiency is due to the new topology and not due to overdimensioning of the semiconductors. Hence, an additional potential of efficiency improvement is still available. Index Terms - Grid-connected, high efficiency, inverter, standalone.

In this study, a switch-mode three-phase active tracking AC-AC voltage regulator based on the boost converter is proposed with a moderate number of active and passive elements used in the topology. A robust hybrid control, where a novel designed feedforward controller supports the closed-loop PID controller, is proposed for the control of the regulator apart from similar studies in the literature. Active tracking response of the reference output phase voltages is augmented by the proposed hybrid control method. Thus nearly close to sine-wave output phase voltages can be obtained, whether the input AC phase voltages are ideal pure sine or not. Also, the modular structure of the regulator topology enables independent control for each output phase. Thus, the supply of balanced/unbalanced wye-connected three-phase loads or independent single-phase loads with nearly close to ideal sine wave voltages can be achieved by the modularity of the regulator. Both experimental and simulation test studies are performed for the proposed regulator system. A laboratory set-up for the regulator is designed for 0-200 Vp input phase voltages (50 Hz), and 0-300 Vp output phase voltages, and 1.8 kW output power. The achieved results for both simulation and experimental tests verify the proposed switch-mode boost-type regulator’s ability to provide output phase voltages nearly close to sine wave with total harmonic distortion (THD) values under 5%. [ABSTRACT FROM AUTHOR]

A new concept for reducing the losses in a boost converter is described. With the help of an auxiliary switch and a resonant circuit, zero-voltage switching at turn-off and zerocurrent switching during turn-on are achieved. The modes of the circuit are shown in detail. The energy recovery of the turn-off is analyzed and the recovered energy is calculated; an optimized switching concept therefore is described. The influence of the parasitic capacity of the switch is discussed. Dimensioning hints for the converter and the design of the recuperation circuit are given. A bread-boarded design shows the functional efficiency of the concept. [ABSTRACT FROM AUTHOR]