Multi-Converter Power Systems Response to Controller’s Communication Network Delays and Loading Parameters

Abstract:
With the rising demand and employment of power electronic converters in microgrids and systems such as shipboard power systems, renewable energy systems and DC distribution systems, voltage conversion required to service various types of electrical loads is possible. A few to hundreds of converters are interconnected together in the composition of these multi-converter power systems and they become instrumental in relieving the dependency on tap changers and capacitors that are conventionally used for voltage regulation. Therefore, control of the output voltage becomes critical for power support in these types of systems. In a system with multi-converters and electromechanical equipment a large variety of dynamic and static interactions are possible and these can lead to irregular behavior of a converter, a group of converters or the whole system. This inherent cross-regulation behavior can lead to exceeding controllers' limits, which results in harmful operation situations during system disturbances. It is significant then to monitor the system during perturbations; their underlying dynamics exhibit trajectories that not only depend on their independent operation modes. Thus the incorporation of these system dynamics into their corresponding modeling formulation is an important feature. Furthermore, if a main control center oversees the operation of a number of remotely located converter systems, such control will be accomplished through the leveraging of communication networks. To ensure desired converter performance, it becomes imperative that appropriate network control systems (NCS) are employed. However, in this case, system operation becomes dependent not only on the control schemes in place but the communication infrastructure as well due to the inherent presence of communication network traffic and noise. This work provides insight into appropriate modeling and simulation of single- and multi-converter systems and the analysis to describe the existence of bounds for plant as well as network parameters; e.g. by analyzing the system’s response to load changes and/or changes in network delay. Once these boundaries are breached the system becomes unstable limiting the effectiveness of available control parameters.