Smart Grid: Characteristics, Opportunities and Challenges Dr. Salman Mohagheghi Department of Electrical Engineering and Computer Science Colorado School of Mines Golden, CO 80401 smohaghe@mines.edu
Smart Grid The Reality The grid has always been smart; however, it is now smarter The modern power grid is different from the traditional power grid in several aspects: More data captured from across the grid More opportunities for remote control Open non-proprietary designs Access to more computational power Abundance of structured data More reliable and efficient communication networks To Summarize: Smart Grid is more about Creation, Transmission and Utilization of Smart Data 2/38
Smart Grid Requirements Availability Data Quality Sustainability Automation Redundancy Fault Tolerance Self-Healing QoS Validity Accuracy Integrity Low Carbon Footprint Asset Mgmt. Energy Conservation Observability Controllability M2M Scalability Security Interoperability Low Cost Upgradability Evolvability System Growth Big Data Cyber-Security Confidentiality Privacy Multi-Vendor Plug & Play Deployment Maintenance Energy 3/38
Smart Grid Conceptual Model NIST has divided the smart grid into 7 domains Smart grid is a cyberphysical system that is achieved by overlaying communication infrastructure with the electric grid 4/38
Smart Grid Hierarchical View 5/38
Smart Grid What Has Changed? Abundance of Data: obtained from multitude of sensors, meters and Intelligent Electronic Devices (IEDs) from across the grid Automated Solutions: in theory, every device can be remotely monitored, configured and controlled Faster Dynamics: high penetration of non-dispatchable renewable resources across the grid Active Consumers: introduce a new set of dynamics Electric Vehicles: mobiles loads (and in the future: energy resources) 6/38
Smart Grid What Is Needed? Dynamic Dispatch of Energy Resources 7/38
Distributed Generation Historically: Embedded Generation/Dispersed Generation/Decentralized Generation Distributed Generation Distributed Energy Resources (DER); often meant to include both DG and Energy Storage (ES) No unique definition exists One definition: An electric power source connected directly to the distribution network or on the customer side of the meter According to this definition, a Combined Heat and Power (CHP) located on a large industrial site at the transmission level is still DG, whereas a medium-sized wind farm connected to the transmission system is not 8/38
DG Classification Dispatchable vs. Non-Dispatchable Rotory Based vs. Non-Rotory Based Based on size Physical interface and control methods Conventional DG Nonconventional DG Primary Energy Source Reciprocating Engines Small Hydro Fixed-Speed Wind Turbine Variable-Speed Wind Turbine Microturbine Solar PV, Fuel Cell SG IM Interface AC/DC/AC Converters DC/DC/AC Converters Power Flow Control AVR/Governor (+P, ±Q) Stall/Pitch Control (+P, Q) Turbine Speed, DC Link Control (+P, ±Q) MPPT, DC Link Control (+P, ±Q) 9/38
DG Sizes No general consensus In general, assumed to be connected to the distribution system (although some authors do not agree) < 10MW Size range examples: A few kw up to 50MW by EPRI Up to 25MW by Gas Research Institute Smaller than 50-100 MW by CIGRÉ A DER unit of 250 kva or more should have means for monitoring its connection status, real power output, reactive power output and the voltage at the PCC 10/38
DG Grid Integration Smaller generators are not connected to the transmission network due to cost of HV transformers/switchgear, and also transmission network is often far from the renewable energy resource In different countries, if the power of the DG is higher than some percentage of transformer capacity (for example 40%), a dedicated feeder or a larger transformer is used Depending on the impedance of the system at the PCC, the appropriate size of DG is determined Network Location Out on 400V network At 400V busbars Out on 11kV network At 11kV busbars On 15kV or 20kV network and at busbars On 63kV to 90kV network Maximum Capacity of DG 50kVA 200 250kVA 2 3MVA 8MVA 6.5 10MVA 10 40MVA 11/38
DG Interconnection Requirements General requirements according to IEEE 1547 v2003 Disconnection due to voltage change Voltage Range (p.u) Time to Disconnect (sec) < 0.5 0.16 0.5 ~ 0.88 2.00 1.1 ~ 1.2 1.00 > 1.2 0.16 Disconnection due to frequency change DER Size Frequency Range (Hz) Time to Disconnect (sec) < 30 kw > 60.5 0.16 < 59.3 0.16 > 60.5 0.16 > 30 kw < {59.8 57} Adjustable 0.16 to 300 Adjustable < 57 0.16 Maximum acceptable harmonic injection Total Current Harmonic h < 11 11 ~ 17 17 ~ 23 23 ~ 35 35 Distortion % 4 2 1.5 0.6 0.3 5 12/38
DG Interconnection Requirements Requirements for connection to secondary networks (IEEE 1547.6 v2011) For a customer facility with DG: 13/38
Microgrid A local energy network, with distributed energy resources (DG, energy storage) and demand responsive loads, which can operate in parallel with the grid or in an intentional island mode to provide high reliability and resilience to grid disturbances Can provide continuous and high-quality supply of power in remote areas, or for protection of critical loads against power grid disturbances 14/38
Drivers for Microgrids Power grid operating closer to operational limits Latest advances in high efficiency DER Smart switches/smart meters Advanced automation techniques DER is becoming more decentralized Higher demand for uninterruptible power supply and higher quality of service Restructured electricity markets 15/38
No Unique Definition Expert opinions from DTE Energy, CERTS, EPRI, European Research Project Cluster, Northern Power, PSERC, ENCORP, Sandia National Lab, NREL, LBNL, GE. Raw data extracted from the presentation Microgrid Business Cases by Public Interest Energy Research Program, California Energy Commission, December 2004 16/38
Microgrid Classification based on Application Campus Environment/Institutional Microgrids Single owner of both generation and loads; from 4MW to 40+ MW Remote Off-grid Microgrids In island mode at all times; ideal for remote villages, islands Military Base Microgrids Focus on both physical and cyber security for military facilities Commercial and Industrial (C&I) Microgrids Maturing quickly in North America and Asia Pacific Community/Utility Microgrids Europe leads this segment; usually do not island Disaster-Relief Microgrids When grid is down and power is needed for post-disaster recovery Source: Asmus and Stimmel, Utility Distribution Microgrids 2012 17/38
Predictions Likely industries to deploy over the next 5 years: Source: Jim Riley, Challenges for Microgrid Deployment Interoperability and Technological Readiness, 2013. 18/38
Microgrid Classification based on Topology According to IEEE 1547.4-2011 19/38
Microgrid Classification based on Size Single Facility Microgrid (< 2MW) Industrial and commercial buildings, residential buildings and hospitals Multiple Facility Microgrid (2-5MW) Spans multiple buildings or structures with a typical load of 2-5 MW Examples include campuses, military bases, industrial and commercial complexes and building residential developments Feeder Microgrid (5-10MW) May include smaller single or multiple facility Microgrids Manages the whole distribution feeder Substation Microgrid (10+ MW) Manages the whole distribution substation Likely to include some generation directly at the substation 20/38
Micro-Generators Grid Forming Units Diesel generator or a battery inverter One master controls the frequency and voltage by balancing the power Grid Supporting Unit Active and reactive power are determined by the voltage and frequency Grid Parallel Units Uncontrolled generators such as wind energy converters or PV-inverters without control 21/38
Microgrid Control Grid Forming Control During island mode Need to set voltage and frequency For multiple-unit case, we can have Master-Slave or Multi- Master control mode 22/38
Demand Response 23/38
Demand Response Reliability-Based Programs Direct Load Control Shutting down the directly controllable loads of the customers For residential and commercial customers; short notice; often uses a one-way remote switch Interruptible and Curtailable(I&C) DR Sending curtailment request signals to the customers For commercial and industrial customers; larger amounts of power ~ several kw; 30-minutes to a few hours of advance notice Emergency GR: for large commercial and industrial customers DR Bids Receiving and (if economically viable) accepting Curtailment Bids from customers 24/38
Demand Response Price-Based Programs Critical Peak Pricing (CPP) Time-of-Use Pricing (TOU) Real-Time Pricing (RTP) 25/38
Demand Response 26/38
Demand Response Chronological Steps 27/38
Industrial Sector and DR Opportunity:2-8% of total customers, up to 80% of electricity usage During peak load can assist the utility through On-site generation Demand Shifting Curtailment of Noncritical Loads Temporary Shutdown Challenges: Loss of load leads to loss of revenue, not just inconvenience More difficult to determine critical loads versus non-critical loads Scheduled maintenance, crew management, inventory management, workstation characteristics (capacity, configuration) 28/38
Dynamic DR for Industrial Systems Source: S. Mohagheghi and N. Raji, Dynamic Demand Response, IEEE Industry Applications Magazine, March/April 2015. 29/38
Supplying Critical Loads during an Outage Transfer Switch UPS Flywheel 30/38
Service Restoration Objective: Use alternate sources and alternative routes to provide power to the outage area Select N/O tie-switches that now have to be closed Algorithm needs to: Estimate the free capacity of the alternate source Estimate the free capacity of the alternate route Estimate the total load requirements of the outage area Suggest a plan if load balance adds up Benefits: faster restoration reduces the stress on UPS and emergency backup power 31/38
Service Restoration 32/38
Service Restoration 33/38
Service Restoration 34/38
Smart Grid Deployment Challenges: Installation and maintenance cost of advanced components Need for implementing a scalable and flexible communication infrastructure Need for implementing communication resources (bandwidth, spectrum, memory) Incorporating less-economical renewable resources into grid operation and dispatch Sophisticated platforms for data management (access, privacy, security) No short term ROI 35/38
Smart Grid Deployment Opportunities: Promising advances in energy-aware and resourceaware sensors and actuators More energy efficient interfaces for DER Decrease in the cost of communication devices and networks Increase in the number of success stories 36/38
Concluding Remarks Smart Grid paradigm can help customers in various ways: DER/Microgrid: Offer flexibility and a certain level of autonomy Distribution and Feeder Automation: Can improve reliability and reduce the frequency/duration of outages Demand Response: Leads to a less volatile electricity market and more transparency Asset management: Helps optimize the utilization of assets, and reduces the need for repair and replacement. This reduces the overall operational cost of the grid. 37/38
Concluding Remarks However: Solutions can be expensive Cost of electricity could increase temporarily ROI is not immediate Need to value benefits in the context of risk Need to promote the culture of sustainability 38/38