A Distributed Scalable Architecture using L1 Adaptive Controllers for Primary Voltage Control of DC Microgrids

Abstract

This paper proposes a new distributed control architecture for distributed generation units in heterogeneous DC islanded microgrids. Each unit is equipped with state-feedback baseline and augmenting L1 adaptive voltage controllers at the primary level of the microgrid control hierarchy. Local controller synthesis is scalable as it only requires information about corresponding units, couplings, and at most, the addition of state-predictor measurements of neighbouring controllers. Global asymptotic stability of the microgrid is guaranteed in a plug-and-play fashion by exploiting Lyapunov functions and algebraic Riccati equations. The performance of the proposed architecture is evaluated using a heterogeneous DC islanded microgrid that consists of 6 DC-DC boost converters configured in a radial and meshed topology. The use of L1 adaptive controllers achieves fast and robust microgrid voltage stability in the presence of plug-and-play operations, topology changes and unknown load changes. Finally, the distributed architecture is tested on a bus-connected islanded-microgrid consisting of linear resistive load and non-linear DC motor.

Voltage Control of DC Islanded Microgrids: Scalable Decentralised L1 Adaptive Controllers

“…Future work will consider line-independent and distributed control architectures 7 in order to guar- 7 Two separate pieces of Work on the theory and implementation of a scalable distributed control architecture that guarantees GAS in a PnP fashion and incorporates L 1 adaptive controllers has been submitted to journals IEEE Transactions on Automatic Control and IEEE Transactions on Smart Grid. Pre-prints are found in [70] and [72] respectively.…”

Decentralised L1 Adaptive Primary Controllers and Distributed Consensus-Based Secondary Control for DC Microgrids with Constant-Power Loads

“…Centralised L 1 AC architectures have been notably successful in safety-critical applications including; sub-scale NASA aircraft auto-pilots [34], manned aircraft [35], and unmanned water/aerial vehicles [36,37]. In addition to our decentralised [28] and distributed [29] L 1 AC architectures, decentralised schemes were formulated in [38,39], and were implemented to augment aircraft baseline controllers [40]. Unlike [34][35][36][37][38][39][40], we consider unmatched interconnections and provide robustness to constant disturbances via integral action.…”

“…Therefore, the desired dynamics must be carefully designed to be minimum-phased. This can be done by transforming local systems to control-canonical form, as performed in [29]. Finally, lim…”

“…However, global asymptotic stability (GAS) is achieved in a conservative fashion, while its computation is non-scalable. Subsequently, we formulated a distributed L 1 AC architecture to guarantee GAS in a scalable, PnP manner [29]. Ultimately, these approaches are predicated on the ability to access hardware or software in order to augment or retrofit existing baseline controllers.…”