Abstract
Recent advances in distribution-level phasor measurement unit (D-PMU) technology have enabled the use of voltage phase angle measurements for direct load sharing control in distribution-level microgrid interconnections with high penetration of renewable distributed energy resources (DERs). In particular, D-PMU enabled voltage angle droop control has the potential to enhance stability and transient performance in such microgrid interconnections. However, these angle droop control designs are vulnerable to D-PMU angle measurement losses that frequently occur due to the unavailability of a global positioning system (GPS) signal for synchronization. In the event of such measurement losses, angle droop controlled microgrid interconnections may suffer from poor performance and potentially lose stability. In this paper, we propose a novel distributed mixed voltage angle and frequency droop control (D-MAFD) framework to improve the reliability of angle droop controlled microgrid interconnections. In this framework, when the D-PMU phase angle measurement is lost at a microgrid, conventional frequency droop control is temporarily used for primary control in place of angle droop control to guarantee stability. We model the microgrid interconnection with this primary control architecture as a nonlinear switched system and design distributed secondary controllers to guarantee stability of the network. Further, we incorporate performance specifications such as robustness to generation-load mismatch and network topology changes in the distributed control design. We demonstrate the performance of this control framework by simulation on a test 123-feeder distribution network.
Highlights
P HASOR measurement units (PMUs) have been extensively used in real-time wide-area monitoring, protection and control (WAMPAC) applications at the transmission level
In order to address stability and performance issues resulting from distribution-level phasor measurement unit (D-PMU) measurement losses in angle droop controlled microgrid interconnections, we introduce the idea of mixed voltage angle and frequency droop control (MAFD)
We show that the MAFD framework, along with a dissipativity-based distributed secondary controller, guarantees stability of angle droop controlled microgrid interconnections without any restrictions on the duration or probability distribution of D-PMU measurement losses
Summary
P HASOR measurement units (PMUs) have been extensively used in real-time wide-area monitoring, protection and control (WAMPAC) applications at the transmission level. The MAFD primary control architecture allows for indirect control of the real power sharing in the microgrid interconnection in a decentralized manner even when D-PMU angle measurements are lost With this architecture, a supplementary controller, termed as the secondary controller, must be designed to eliminate the voltage and angle errors that arise due to open-loop droop control. We propose a distributed secondary control design that uses only local information at each microgrid to regulate angle and voltage deviations and guarantee stability of the network of interconnected microgrids. Given the dynamics in (10) and its linear approximation (11), we would like to design a secondary controller that eliminates voltage and angle deviations in the microgrid interconnection and guarantees stability during D-PMU measurement losses. The proofs of all the results are provided in the Appendix
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