Publications by Liang Che
The optimal planning of the interconnected network of multi-microgrids is discussed in this paper... more The optimal planning of the interconnected network of multi-microgrids is discussed in this paper. The interconnection planning will enhance the reliability and the economic operation of a community of microgrids. The proposed approach will apply a probabilistic minimal cut-set-based iterative methodology for the optimal planning of interconnection among microgrids with variable renewable energy sources. The optimal planning takes into account various factors including the economics, reliability, and variability of renewables, network- and resource-based uncertainties, and adaptability to accommodate the prevailing operating concerns. A clustering-based method is considered for analyzing the variable data concerning the potential deployment of renewable energy in microgrids. The proposed interconnection planning methodology is applied to a six-microgrid system and the planning results are discussed. The numerical results demonstrate that the proposed interconnection planning methodology will determine an optimal topology accurately and efficiently for a cluster of microgrids, and show that the proposed adaptive planning methodology can easily be applied to practical microgrid applications.
In a nutshell, smart grids are about reacting to storms and outages and limiting the amount and s... more In a nutshell, smart grids are about reacting to storms and outages and limiting the amount and severity of power outages. Another tool—microgrids—is about stopping power outages from the get-go. The advent of modern distribution networks with DERs has changed the service restoration paradigm. Such distribution networks are equipped with local generation sources that behave like virtual power plants and active loads that provide ancillary services such as frequency and voltage. support and service restoration to the utility. Under such conditions, the operation of the distribution network necessitates enhanced protocols for communication at all levels of the distribution system to assist distribution management system (DMS) operators with real-time decisions.
The additional deployment of distributed energy resources (DERs) has attracted further attention ... more The additional deployment of distributed energy resources (DERs) has attracted further attention to dc microgrid applications. The objective of the study is to discuss the possibili- ties and the merits of adopting a dc control system for enhancing the economics and the resilient operation of a dc microgrid, and to test the proposed hierarchical control strategy that applies to a dc microgrid. This paper provides case studies in which an existing microgrid at the Illinois Institute of Technology (IIT) is operated as a dc microgrid and the results for each case are compared with the ac model. The structure, components, and control strategies of IIT dc microgrids are discussed and the economic operation of a grid-connected dc microgrid through tertiary control, as well as islanding, load restoration, and resyn- chronization of the dc microgrid are simulated. The dc microgrid simulation results are compared with those of an ac microgrid, which demonstrate that the proposed coordinated dc strategy for the optimal operation of DERs is an effective way of ensur- ing the resilient response of dc microgrid to emergencies and its economic operation at steady state.
In this paper, a community microgrid with multiple ac and dc microgrids is introduced and analyze... more In this paper, a community microgrid with multiple ac and dc microgrids is introduced and analyzed. Individual microgrids with different frequency and voltage requirements would operate as self-controlled entities, which could also cooperate with neighboring microgrids for providing backup operations in the community microgrid. A hierarchical coordination strategy with primary, secondary, and tertiary coordination is proposed for the economic operation of an islanded community microgrid. The hierarchical strategy is also applied to a grid-connected community microgrid and the results are discussed. The simulation results verify that the proposed hierarchical coordination strategy is an effective and efficient way for coordinating microgrid flows in an islanded community microgrid, while maintaining the rated frequency and voltage with each microgrid. The simulation results also demonstrate the economic operation of a grid-connected community microgrid in which individual microgrids operate as autonomous agents, while satisfying the community objectives.
One of the prominent challenges in microgrid operations is the design of a proper protection sche... more One of the prominent challenges in microgrid operations is the design of a proper protection scheme for microgrids. In this article, protection system challenges in microgrids are discussed and protection practices in the context of a functional microgrid system at the Illinois Institute of Technology (IIT) are presented. We address the structure and design of the IIT microgrid and analyze technical approaches for protecting the IIT microgrid in grid-connected and island modes.
This paper compares a DC microgrid model with its AC version with regard to the dynamic responses... more This paper compares a DC microgrid model with its AC version with regard to the dynamic responses to major disturbances, for discussing the possibilities and the merits of adopting DC microgrid based strategy to enhance the resilience and dynamic performance of distributed generation systems. An existing microgrid at Illinois Institute of Technology (IIT) is remodeled as a DC microgrid, based on which a hierarchical control strategy is investigated and applied. The simulation results are compared with those of the IIT AC microgrid and demonstrate the proposed strategy of coordinated DC microgrid as an effective way of ensuring the system resilience and dynamic performance in both steady state and emergencies.
The implementation of high-reliability microgrids requires proper protection schemes that effecti... more The implementation of high-reliability microgrids requires proper protection schemes that effectively function in both grid-connected and island modes. This paper presents a communication-assisted four-level hierarchical protection strategy for high-reliability microgrids, and tests the proposed protection strategy based on a loop structured microgrid. The simulation results demonstrate the proposed strategy to be an effective and efficient option for microgrid protection.
In this paper, the impact of natural gas system on the short-term scheduling with high penetratio... more In this paper, the impact of natural gas system on the short-term scheduling with high penetration of renewable energy is illustrated and analyzed. The natural gas infrastructure constraints are integrated into the security-constrained unit commitment model, which minimizes the expected operation cost while considering the variable wind power generation. Benders decomposition is applied to solve the problem with non-linear natural gas network constraints. Illustrative examples demonstrate the effectiveness of the proposed approach for analyzing the impact natural gas system on system scheduling with volatile renewable energy.
This paper presents an integrated long-term expansion planning model that considers the interdepe... more This paper presents an integrated long-term expansion planning model that considers the interdependency of natural gas and electricity infrastructures. The integrated planning problem determined the least-cost planning schedule of candidate generating units, transmission lines, and natural gas pipelines. The fuel supply feasibility was represented by the natural gas transportation constraints. The Investment decisions of electricity and natural gas infrastructures would satisfy the desired power system reliability criterion. Numerical simulations demonstrate the effectiveness of the proposed integrated planning approach.
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Publications by Liang Che