Dynamic characterization of power converters : methods and actuators

The availability of methods and devices to support the implementation of the Smart Grid represents the real key point to design modern power networks, both for large size and for local distribution systems (Microgrids). Efficient management of energy flows and the exploitation of the renewable energy sources can be carried out using smart power electronic interfaces. The interaction of multiple power converters among sub-grids or grids and distribution nodes can give rise to not trivial stability issues. The experimental dynamic characterization of power converters represent a critical issue in micro power systems analysis. It allows to evaluate not only performances of power circuits in terms of bandwidth, transient response, etc, but also their dynamic influence on the whole system. Techniques for loop gain measurements are well established and usually adopted in test procedures. Not so for the experimental characterization of input and output closed loop transfer functions, which imply the use of auxiliary circuitry to inject small signals upon the steady state values in high voltage or with high output current. The paper discusses different approaches to dynamic measurements and proposes some actuators for signal injection. Experimental results are provided.