Implementation of grid-connected converters

Power electronic building blocks

With the advent of high performance digital controllers, the time and effort to implement new control algorithms for the control of power electronic converters have decreased drastically. Nevertheless, the design and the practical implementation of power electronic converters, intended for testing new control algorithms, are still complicated and time-consuming activities. Therefore, a fully equipped half bridge test platform was designed ready to use as a fundamental building block for various converter types. The test platform incorporates fault protection, measurements of well-selected voltages and currents, and is directly interfacable with most digital and analogue controllers. Due to these features and the flexibility of the board, this half bridge converter can be used for research as well as for educational purposes in applications ranging from a simple 100 W buck converter up to 10 kW inverters for motor control. Fig. 1 shows a picture of two building blocks, employed as a full-bridge converter.

Recently, a new version of this building block was developed. The new board offers more flexibility in converter topologies. Just like the first platform, it contains two switches in a half bridge configuration, though the switches can be disconnected in order to build topologies with separate switches. This allows the use of the platform in multilevel converters (neutral point clamped as well as flying capacitor) and in drives for switched reluctance machines. In the new building block, the power circuit is completely isolated from the measurement and protection circuit. A picture of the new platform is shown in Fig. 2.

Single-phase boost PFC converter

As input stage of many switching power supplies, a boost converter topology is used. This converter has a double objective: to control the waveform of the converter input current so that the regulations are met, and to control the dc voltage at the output of the converter to a (in most cases) constant level. The converter scheme is shown in Fig. 1 together with its control loops.

Single-phase full-bridge converter

The topology of the full-bridge ac-dc bidirectional converter is depicted in Fig. 1. The converter consists of an EMI-filter (capacitance Cg ) on the ac-side of the converter, and a boost-type full-bridge converter with two input inductors L/2, switches S1 to S4, and a buffer capacitor at the dc-side of the converter. The converter is controlled by a digital signal processor (DSP).