Zhe Yu

A Distributed Cooperative Control Framework for Synchronized Reconnection of a Multi-Bus Microgrid

One critical value microgrids brings to power systems is resilience, the capability of being able to island from the main grid under certain conditions and connect back when necessary. Once islanded, a microgrid must be synchronized to the main grid before reconnection to prevent severe consequences. In general, synchronization of a single machine with the grid can be easily achieved using a synchronizer. The problem becomes more challenging when it comes to a multi-bus microgrid with multiple distributed generators (DGs) and dispersed loads. All DGs need to be properly controlled in a coordinated way to achieve synchronization. This paper presents a novel bi-level distributed cooperative control framework for a multi-bus microgrid. In this framework, DGs work collaboratively in a distributed manner using minimum and sparse communication. The topology of the communication network can be flexible which supports the plug-and-play feature of microgrids. Fast and deterministic synchronization can be achieved with tolerance to communication latency. Experimental results obtained from hardware-in-the-loop simulation demonstrate the effectiveness of the proposed approach.

Bilevel optimization based transmission expansion planning considering phase shifting transformer

In this paper, the phase shifting transformer (PST) is introduced in the Transmission Expansion Planning (TEP) problem considering significant wind power integration. The proposed planning model is formulated as a bilevel program which seeks to determine the optimal strategy for the network reinforcements and the PST locations. The objective of the upper level problem is to minimize the total consumer payment, the investment cost on transmission line and PST. The lower level problems designate the electricity market clearing conditions under different load-wind scenarios. The bilevel model is transformed into a single level mixed integer linear program (MILP) by replacing each lower level problem with its primal-dual formulation. The numerical case studies based on IEEE 24-bus system demonstrate the characteristics of the proposed model. Moreover, the simulation results show that the installation of PST adds flexibility to the TEP and facilitates the integration of wind power.

Online Calibration of Phasor Measurement Unit Using Density-Based Spatial Clustering

Data quality of the phasor measurement unit (PMU) is receiving increasing attention as it has been identified as one of the limiting factors that affect many wide-area measurement system-based applications. In general, existing PMU calibration methods include offline testing and model-based approaches. However, in practice, the effectiveness of both is limited due to the very strong assumptions employed. This paper presents a novel framework for online bias error detection and the calibration of PMU measurements using density-based spatial clustering of applications with noise based on much relaxed assumptions. With a new problem formulation, the proposed data mining-based methodology is applicable across a wide spectrum of practical conditions and one side product of it is more accurate transmission-line parameters for energy-management system (EMS) database and protective relay settings. Case studies demonstrate the effectiveness of the proposed approach.