Energy Storage Control and Requirements For Inverter-Based Microgrids

The intermittent nature of distributed renewable sources such as wind or solar requires integration of energy storage systems. In this dissertation a distributed form of the Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) method is used to determine the energy storage requirements of three-phase inverter-based microgrids. The overall control is appropriate to be integrated into a hierarchical control system. As the primary control, a novel dq droop control sets the local references and is supported by a level-zero Hamiltonian controller which includes energy storage feed-forward and feedback, and an inverter feed-forward controls. Here, the energy storage element performs as the sole actuator of the system and enforces the references that are set by the droop control while the inverter feed-forward matches the voltage levels of the inverter to the local bus. The control method as well as the power flow and energy transfer model of the microgrid system enables the capacity and bandwidth of the storage system to be determined. The Hamiltonian control is further derived for parallel operation of hybrid, band-limited and reduced-order battery and flywheel storage systems. Moreover, a control scheme is proposed to enable sharing of power between parallel battery and flywheel storage systems according to their bandwidth support capabilities. Here, battery storage systems are considered as the primary storage elements while flywheel systems are controlled to complement the deficit for higher power fluctuations. Power and energy sizing guidelines are presented and relevant trade-offs are addressed in illustrative examples. Energy storage baseline requirements for pulsed power loads are also presented in this work. Here, the energy storage system combination with the pulsed load is controlled to mimic a constant power load that can further be integrated into power buffer systems. Examples of control and requirements for ideal, band-limited and reduced-order battery and flywheel storage systems are given. By considering these requirements, a system designer can derive the specifications for source-side or load-side energy storage elements and their control systems