Project 1.3 Status Monitoring, Disturbance Detection, Diagnostics, and Protection for Intelligent Microgrids Dr Wilsun Xu C. Jiang, H. Yazdanpa, Y. Tian & A. Pezol www.smart-microgrid.ca Project 1 of 3: How to protect MG from short-circuit faults? Problems faced by industry: • Overcurrent protections are widely used in various facilities (basis of MG) • DGs (distributed generators) create difficulties for over-current protections • Can we find a method for DGs to work with the protection scheme? Proposed solutions and innovations: • Introduce the concept of fault current restriction for DGs • Each DG can only produces a limited amount of short-circuit currents • Develop current restriction schemes for 4 types of DGs Potential benefits: • Both utilities and DG owners are very interested in finding a simple solution to the problem. This solution does not require changes to utility system • The results will lower the interconnection barrier for DGs www.smart-microgrid.ca Project 2 of 3: How to monitor and diagnose MG conditions? Problems faced by industry: • Even with ICT, it is still costly and difficult to monitor loads in a MG • Can we monitor the loads at locations where power sensors are not available? • The information will help to characterize the load behaviors in a MG and to support demand response and other energy-saving activities Proposed solutions and innovations: • Introduce the concept of micro-grid state estimator (MG-SE) • The estimator uses measured voltages to estimate loads in a MG • The proposed system could solve the sub-metering problem Potential benefits: • The problem is of significant interest to commercial facility owners • The results will enable more energy-efficient activities in MG & commercial buildings www.smart-microgrid.ca Project 3 of 3: Home-based MG or “nano-grid” Microgrid Concept Home area network Concept Future Smart Home Energy generation: Energy storage: Energy consumption: Solar & natural gas Electric vehicle Home appliances Nano-grid is a system for managing the generation, storage, consumption of energy in homes. It is build on the concepts of microgrid and home area network. • Home-based MG could be the future form of energy use in homes • The results will facilitate the energy saving activities of home owners www.smart-microgrid.ca 2011 Proj 1: Propose and confirm solutions for 2 types of DGs Proj 2: Complete technical feasibility study Proj 3: Complete review and formulate research strategy 2013 Proj 1: Propose and confirm solutions for other DG types Complete project Proj 2: Complete research work Proj 3: Establish blueprints for nano-grid with research results 2015 Proj 1: Technology transfer Proj 2: Complete demo & tech transfer, complete study on sub-metering applications Proj 3: Complete research work and tech transfer www.smart-microgrid.ca 2.1: Cost-benefit 2.3: Demand responses 1.1 Control & operation 1.2: Power management 1.4 Operational strategies of MG 3.1: HAN (Home area network) 3.3: Automation Proposed projects www.smart-microgrid.ca Collaboration items - General 1. Establish MG test cases (steady-state, dynamics and transients) 2. Experimental facilities available for the network. Especially on how to access BCIT facility Collaboration items - Specific 1. Experimental studies of fault current restriction schemes 2. MG State estimator: formulation, algorithms and experimental studies 3. Nanogrid: a) MG expertise and HAN expertise b) architecture consideration of nanogrid c) Experimental facility d) Implications to power systems (theme 1) www.smart-microgrid.ca Project 1 Details: Fault current restriction strategy for DG Every DG shall not contribute to fault current that is higher than k-times of its normal operating current (k=1.2 to 1.5) Synchronous generator We propose crowbar control to limit excitation current S1 E xcite r SM S2 C on tr o l C row bar Period critical to relay www.smart-microgrid.ca Project 1 Details: Fault current restriction strategy for DG Inverter-based generator We propose a control that reduces inverter output when sag is detected • In traditional control, during voltage sags, inverter current is increased until it reaches the current threshold which is normally set to 1.3~2 Irated . • In our control strategy, converter current is reduced in proportional to severity of sag level Operation during low-impedance fault www.smart-microgrid.ca Operation during high-impedance fault Project 2 Details: Micro-grid state estimator Panel 1 Panel 2 Panel 3 The currents of Load 1-3 are not known, we may only know the panel 1 current If we know the voltages of buses X,Y and Z and the network impedances, the currents can be estimated The voltages are much easier to measure with the help of distributed plug-in voltage sensors X Y Z Load-1 Load-2 Load-3 Traditional SE: estimate V using known I or S Microgrid SE: estimate I using known V www.smart-microgrid.ca