No abstract

The decreasing cost of photovoltaic (PV) systems allows the production of cheap renewable electricity. This has led to an increasing number of installed systems during the past years. Since the storage of electrical energy is still rather expensive, the optimization of the self-consumption coverage gains importance. One solution to higher self-consumption is a method called "PVto-Heat", where excess PV energy is not fed into the grid but stored in the form of hot water in the domestic boiler. This article describes a simplified hardware approach for a three-phase PWM chopper for AC/AC conversion. It is suited for low inductive loads like electric heaters. Compared to existing systems, the proposed converter design offers equal or better performance at very low cost and small size. The circuit allows full control of the power flow and provides sinusoidal and symmetrical load currents. The average electrical efficiency is 94.7% for a 6 kW test system. Unlike certain commercial products, there is no need to use a custom heater or access the star point of the load resistor.

Induction heating plays an important role in industrial processes and is becoming increasingly important for household appliances such as induction cookers. Most commonly, series or parallel resonant circuits based on IGBT technology are used due to their low cost. In contrast to these, non-resonant converter types are described in this paper for the first time regarding their use in single-phase induction heating applications up to 2 kW. The analysis is based on simulation and measurement results. The proposed non-resonant converter designs offer a very small size and allow full control of the output power. Different pulse pattern for controlling the induction power are investigated. It is found that the full-bridge inverter using block or PSM pulse pattern delivers the best performance and enough power capability. For the test system, the measured average electrical efficiency is 96.8 % over the input power range of 500 W to 1750 W.