Recent papers have shown advantages of robust controllers compared to controllers based on classical control theory. Further improvements in performance and stable operating range may be realized through the use of multiple robust controllers, but these are typically complicated to synthesize and implement. The complexity is somewhat relaxed for bumpless-transfer controllers, which have appeared in the literature as an ad-hoc gain-scheduling control scheme. The approach is less conservative, easier to synthesize, and easier to implement than a gain scheduled polytopic controller or other interpolation scheme, and has a larger operating range than a nominal controller. In this paper an inverter connected to a microgrid is modeled as a linear parameter varying (LPV) system and bumpless controllers are scheduled using polytopic coordinates and applied to inverters in a microgrid.
It is well known that power factor correction (PFC) circuits suffer from two fundamentally different operating modes over a given AC input cycle. These two modes, continuous conduction mode (CCM) and discontinuous conduction mode (DCM), have very different frequency-response characteristics that can make control design for PFC circuits challenging. The problem is exacerbated by attempts to improve efficiency by dynamically adjusting the PWM switching frequency based on the load. Adjusting the PWM frequency based on the load limits controller bandwidth and restricts dynamic performance. Prior work has made use of multiple controllers, however, they have not addressed the discontinuity (bump) that exists when switching between controllers. In this paper, bumpless controllers will be synthesized for a 750 watt, semi-bridgeless PFC for the CCM-DCM operating modes.
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