University of Illinois UrbanaChampaign Integration and Interconnection of

University of Illinois Urbana-Champaign Integration and Interconnection of Distributed Energy Resources Geza Joos, Professor Electric Energy Systems Laboratory Department of Electrical and Computer Engineering Mc. Gill University 4 November 2013 Mc. Gill University 1 G. Joos

Overview and issues addressed n Background Ø Distributed generation and resources – definition and classification Ø Benefits and constraints n Grid integration issues n Grid interconnection and relevant standards Ø Distribution systems standards Ø Steady state and transient operating requirements n Protection requirements Ø General requirements – types of protection Ø Islanding detection n Concluding comments Ø Distributed energy resources – microgrids and isolated systems Ø Future scenarios 2 Mc. Gill University G. Joos

Electrical power system – renewable generation Residential Mc. Gill University 3 G. Joos

Future electric distribution systems – a scenario Mc. Gill University 4 G. Joos

Distributed generation – definition – classification n A subset of Distributed Energy Resources (DER), comprising electrical generators and electricity storage systems n Size – from the k. W (1) to the MW (10 -20) range n Energy resource Ø Renewables – biomass, solar (concentrating and photovoltaic), wind, small hydro Ø Fossil fuels – microturbines, engine-generator sets Ø Electrical storage – batteries (Lead-Acid, Li-Ion) Ø Other – fuel cells (hydrogen source required) n Connection Ø Grid connected – distribution grid, dispersed or embedded generation, may be connected close to the load center, voltage and frequency st by the electric power system Ø Isolated systems – voltage and frequency set by a reference generator 5 Mc. Gill University G. Joos

Distributed generation – definition – features n Not centrally planned (CIGRE) – is often installed, owned and operated by an independent power producer (IPP) n Not centrally dispatched (CIGRE) – IPP paid for the energy produced and may be required to provide ancillary services (reactive power, voltage support, frequency support and regulation) n Connection – at any point in the electric power system (IEEE) Ø Interconnection studies required to determine impact on the grid Ø May modify operation of the distribution grid n Types of distributed generation Ø Dispatchable (if desired) – engine-generator systems (natural gas, biogas, small hydro) Ø Non dispatchable (unless associated with electricity storage) – wind, solar 6 Mc. Gill University G. Joos

Distributed generation – installations n Typical installations, from large to small Ø Industrial – Generating plants on industrial sites, high efficiency, in combined heat and power (CHP) configurations Ø Commercial Ø Residential installations, typically solar panels (PV) n Features of smaller power dispersed generation Ø Can typically be deployed in a large number of units Ø Not necessarily integrated in the generation dispatch, not under the control of the power system operator (location, sizing, etc) 7 Mc. Gill University G. Joos

Distributed generation – drivers n Promoting the use of local energy sources – wind, solar, hydro, biomass, biogas, others n Creating local revenue streams (electricity sales) n Creating employment opportunities (manufacturing, erection, maintenance, operation) n Responding to public interest and concerns about the environment – public acceptance can be secured n Green power – Greenhouse Gas (GHG) reduction Mc. Gill University 8 G. Joos

Distributed generation – technical benefits n Enhanced reliability – generation close to the load n Peak load shaving – reduction of peak demand n Infrastructure expansion deferral – local generation n Distribution (and transmission) system loss reduction – generation close to load centers n Lower grid integration costs – local generation reduces size of connection to the main grid n Distribution voltage connection (rather than transmission) – ease of installation and lower cost n Voltage support of weak distribution grids Mc. Gill University 9 G. Joos

Distributed generation – typical installations n Typical power plant types Ø Ø Hydraulic, 5 -10 MW Biomass, 5 -10 MW Biogas, 5 -10 MW Wind, 10 -25 MW n Total installed power (2011): 61 plants, 350 MW n Connection: MV grid (25 k. V, nominal 10 MW feeders typical for Canadian utilities) Ref: Presentation Hydro-Quebec Distribution, 2011 Mc. Gill University 10 G. Joos

Hydro-Quebec – on-going projects 2011 -2015 n Biomass Ø 4 plants Ø 25 MW on MV grid Ø Commissioning 2012 -2013 n Small hydro Ø 8 plants Ø 54 MW on MV grid Ø Commissioning 2010 -2013 n Wind power plants Ø 5 plants Ø 125 MW on MV grid Ø Commissioning 2014 -2015 Mc. Gill University 11 G. Joos

DG connection to the grid – options n Connection options Ø Distribution network – low (LV), typically 600 V, and up to 500 k. W Ø Distribution network - medium voltage (MV), up to 69 k. V, typically 25 k. V, up to 10 -20 MW Ø Transmission network – aggregated units, typically 100 MW or more n Power system impacts Ø Distribution – local, typically radial systems Ø Transmission – system wide, typically meshed systems n Differing responsibilities and concerns Ø Distribution – power quality (voltage), short circuit levels Ø Transmission – stability, voltage support, generation dispatch n Integration constraints – in relation to the electric power grid Ø Power quality – should not be deteriorated Ø Power supply reliability and security – should not be compromised Mc. Gill University 12 G. Joos

Integration and interconnection issues n Integration of the generation into existing grids – constraints Ø Operating constraints – maximum power (IPP paid for k. Wh produced), desired operation at minimum reactive power (unity power factor) Ø Dealing with variability and balancing requirements (if integrated into generation dispatch) – characteristic of wind and solar installations Ø Integration into the generation dispatch – requires monitoring, energy production forecasting n Interconnection into the existing grid – constraints Ø Connection to legacy systems – protection coordination, transformer and line loading, impact on system losses Ø Reverse power flow – from end-user/producer to substation Ø Increased short circuit current – DG contribution Ø Operational issues – grid support requirements and contribution Mc. Gill University 13 G. Joos

Specific DG interconnection issues n Generation power output variability Ø Short term fluctuations – flicker (wind, solar) Ø Long term fluctuations – voltage regulation, voltage rise at connection n Reactive power / Voltage regulation – coordination Ø Reactive compensation – interaction with switched capacitor (pf) Ø Voltage regulation – impact on tap-changing transformer operation Ø Impact on Volt/Var compensation – interference n Harmonics and static power converter filter interaction Ø Voltage distortion produced by power converter current harmonics Ø Resonances with system compensating capacitors n Islanding and microgrid operation Ø Operation in grid connected and islanded modes – transfer Ø Microgrids – possibility of islanded operation – aid to system restoration Mc. Gill University 14 G. Joos

DG interconnection and control requirements n Reactive power and power factor control – required n Voltage regulation – may be required (using reactive power) n Synchronization – to the electric power system n Response to voltage disturbances – steady state and transient n Response to frequency disturbances – steady state and transient n Anti-islanding – usually required (to avoid safety hazards) n Fault, internal and external – overcurrent protection n Power quality – harmonics, voltage distortion (flicker) n Grounding, isolation n Operation and fault monitoring n Grid support – larger units Mc. Gill University G. Joos

General DG standards n Distributed resources (DR) standards Ø IEEE 1547, Standard for Interconnecting Distributed Resources with Electric Power Systems and applies to DR less than 10 MW n Generally applicable standards for the connection of electric equipment to the electric grid. Ø IEEE in North America and IEC in Europe, cover harmonic interference and electrical impacts on the grid. Ø Most commonly used are the IEEE 519 and the IEC 61000 series. n Utility interconnection grid codes and regulations – issued by regional grid operators as conditions for connecting DGs to the electric grid 16 Mc. Gill University G. Joos

Operational requirements – larger installations n Based in part on conventional generation (synchronous) – may apply to DGs connected to the distribution grid n Voltage regulation – may be enabled n Frequency regulation – may be required n Low voltage ride through (LVRT) – may be required n Power curtailment and external tripping control – may be required n Control of rate of change of active power – ramp rates n Other features – typically required for large wind farms (> 100 MW, transmission connected), may be required for farms > 5 -25 MW Ø Ø Mc. Gill University control of active power on demand reactive power on demand inertial response for short term frequency support Power System Stabilization functions (PSS) – special function 17 G. Joos

DG protection issues – general considerations n Operational requirements Ø Distribution system – must be protected from influences caused by DG during faults and abnormal operating conditions Ø DG – must be protected from faults within DG and from faults and abnormal operating conditions caused by distribution circuits n Specific considerations Ø Impact of different DG technologies on short circuit contribution and voltage support under faults – induction generators, synchronous generators, static power converters (inverters) Ø Impact of power flow directionality (reversal) on existing distribution system protection n Instantaneous reclosing following temporary faults Ø Utility breaker reclosing before DG has disconnected – may lead to outof-phase switching – avoided by disconnecting the DG during the autoreclosing dead time (as low as 0. 2 s) Mc. Gill University G. Joos

Protection system – role and requirements n Role – to detect and isolate only the faulty section of a system so that to maintain the security and the stability of the system n Abnormal conditions – include effect of short circuits, overfrequency, overvoltages, unbalanced currents, over/under frequency, etc. n Protection system requirements Ø rated adequately Ø selective – will respond only to adverse events within their zones of protection Ø dependable – will operate when required Ø secure – will not operate when not required n Faults seen by the DG Ø Short circuits on the feeder Ø Loss of mains – feeder opening and islanding Mc. Gill University 19 G. Joos

Protection functions of a DG interconnection PCC -HV bus T 1 PCC -LV bus cb 1 ~ Line 2 Line 1 Line 3 cb 4 S cb 7 cb 2 T 2 R 7 cb T 3 R 7 L 3 cb 5 TL cb 8 L 1 DG 1 L 2 L 4 DG 2 - Mc. Gill University 20 G. Joos

DG islanding detection – requirements n Unintentional islanding defined as DG continuing to energize part of distribution system when connection(s) with area-EPS are severed (also referred to as “loss of mains”) n IEEE 1547 - the DG shall cease to energize the Area EPS circuit to which it is connected prior to reclosure by the Area EPS n Repercussions of an island remaining energized include: Ø Personnel safety at risk Ø Poor power quality within the energized island Ø Possibility of damage to connected equipment within the island, including DG (due to voltage and frequency variations) n Utility grid codes may allow islanded operation during major outages – may help restore service in distribution system Mc. Gill University 21 G. Joos

Islanding detection techniques – passive n Passive approaches Ø Frequency relays (Under/Over-frequency) - use of the active power mismatch between island load and DG production levels Ø Voltage relays (Under/Over Voltage) - based on voltage variations occurring during islanding, resulting from reactive power mismatch Ø ROCOF relays (Rate Of Change Of Frequency – resulting from real power mismatch in the case an island is created Ø Reactive power rate of change – resulting from reactive power mismatch in the case an island is created n Other approaches Ø Active protection – based on difference in area-EPS response at DG site when islanded; injection of signature signals at specific intervals Ø Communication-based protection – using a communication link between DG and area EPS (usually at the substation level) to convey info on loss of mains (and possibly activate a transfer-trip) Mc. Gill University 22 G. Joos

Alternative approach – intelligent relays n Alternative (intelligent) proposed approach – passive, using only measured signals (current, voltage and derived signals) n Use of a multivariate approach to develop a data base of islanding patterns n Use of data mining to extract features from the running of a large number of operating conditions (normal) and contingencies (faults) n Use of extracted features to develop decision trees that define relay settings Mc. Gill University 23 G. Joos

DG variables monitored – multivariable approach Mc. Gill University 24 G. Joos

Feature extraction – methodology n Data Mining – a hierarchical procedure that has the ability to identify the most critical DG variables for islanding pattern detection, or protection handles n Decision Trees – define decision nodes; every decision node uses different DG variables to proceed with decision making on identifying the islanding events n Training data set – islanding (contingencies) and non-islanding events n Time dependent decision trees generated – extracted at different time steps up to the maximum time considered/allowable n Choice of decision tree for relay setting (best) – based on Dependability (ability to detect an islanding event as such) and Security (ability to identify a non-islanding event as such) indices Mc. Gill University 25 G. Joos

Performance requirements – islanding detection n Requirements - defining maximum permissible islanding detection time (typically 0. 5 to 2 s) n Performance indices Ø Dependability and Security indices Ø Speed of response, or detection time Ø Existence of non detection zones n Constraints Ø accounting for Interconnection Protection response times (reclosers) Ø detection of islanding and tripping before utility attempts reclosing (out of phase reclosing may be damageable) n Nature of relay and impact on performance requirements – short circuit detection needs to be faster that islanding detection – allows additional to refine the decision tree Mc. Gill University 26 G. Joos

Real Time Simulator set up – basic relay testing Distribution system Part 1 Part 2 Islanding relay Mc. Gill University 27 G. Joos

Decision trees – typical results Mc. Gill University 28 G. Joos

Comparative performance – relay settings Mc. Gill University 29 G. Joos

Dependability indices – comparative evaluation Mc. Gill University 30 G. Joos

Security indices – comparative evaluation Mc. Gill University 31 G. Joos

Non detection zones – comparative evaluation Mc. Gill University 32 G. Joos

Feasibility and performance of intelligent relays n The proposed data mining approach is capable of Ø Identifying the DG variables that capture the signature of islanding events, in any given time interval Ø Recommending variables and thresholds for protection relay setting n The islanding intelligent relay Ø Operates within prescribed time requirements (or faster) Ø Can be configured for delayed operation possible Ø Dependability and security indices typical better than existing passive techniques Ø Offers improved performance, including smaller non detection zones Ø Can be configured for different types of DG (rotating and power converters based), multiple DG systems and mixed DG type systems Ø Can also be used for short circuit detection (including high impedance faults) and other types of faults Mc. Gill University 33 G. Joos

Impact of DG technology on protection design n DG operation dependent upon the type of generator used Ø Rotating converters: synchronous and induction generators Ø Static power converter interfaces (inverter based): wind turbine (Type 4), solar power converters Ø Mixed: doubly-fed induction generators (wind turbine, Type 3) n Impact of the type of generator connected to the grid on protection design Ø Short circuit level – typically lower in inverter based systems (1 -2 pu) Ø Transients – fully controlled in inverter based systems, dependent on controller settings Ø Speed of response of real and reactive power injection – typically much faster in inverter based systems Ø Real and reactive power capability and control – independent control in inverter based systems Mc. Gill University 34 G. Joos

DER integration – opportunities in microgrids n DER integration into distribution systems Ø As individual systems, either generation or storage, connected to a feeder or in a substation Ø Integrated into a self managed system, or microgrid Ø Aggregated to form a Virtual Power Plant n Microgrid definition – a distribution system featuring Ø Sufficient local generation to allow operation in islanded mode Ø A number of distributed generators and storage systems, including generation based on renewable energy resources Ø A local energy management system Ø A single connection to the electric power system, with possibility of islanded operation Ø The controllers required to allow connection and disconnection and interaction with the main Mc. Gill University 35 G. Joos

Microgrid – types and uses n Microgrid deployment drivers – general and current Ø Increasing the resiliency and reliability of critical infrastructure and specific entities, in the context of exceptional events (storms) – reducing dependence on central generation and the transmission grid Ø Facilitating the integrating renewable energy resources – managing variability locally Ø Taking advantage of available local energy resources – renewables and fossil fuels (shale gas) Ø Reducing greenhouse gases and reliance on fossil fuels – costs n Types, applications and loads Ø Ø Mc. Gill University Military bases – embedded or remote Large self managed entities – university campuses, prisons Industrial and commercial installations Communities – managing storage and generation locally 36 G. Joos

Isolated/autonomous grids – applying DER Isolated Microgrid Solar Wind Battery storage Synchronous generator Distributed Energy Resources Mc. Gill University Conventional Generation 37 G. Joos

Benefits of storage and demand response n In conjunction with renewable DG Ø Ø Ø Reducing power variations in variable and intermittent generation Ability to provide voltage support and voltage regulation Enabling operation of DG at peak power and efficiency Power quality – voltage sag and flicker mitigation Possibility of islanded operation – microgrid operation n Distribution system benefits Ø Ø Ø Mc. Gill University Ability to dispatch/store energy and manage peak demand Reduced line loading – managing line congestion Frequency regulation, black start, reactive power Ability to provide other ancillary services Ability to perform arbitrage on electricity prices – market context 38 G. Joos

Electrical storage technologies Source: Fraunhofer UMSIGHT Mc. Gill University 39 G. Joos

Demand response – characteristics n Available loads Ø Electric hot water heaters – thermal storage Ø Other curtailable loads – on critical Ø Electric vehicle battery storage systems n Features of loads Ø Ø Mc. Gill University Dispersed – low power, large numbers are required Availability – short duty cycles Controllability – usually only in curtailment, possibly as additional laod Duration of service – limited curtailment 40 G. Joos

Storage vs demand response – interchangeable? n Demand response Ø Benefits: instantaneous response Ø Drawbacks: unavailability, discrete control, requires a large number of loads (stochastic behavior) Ø Others: no power quality issues, but discrete steps Ø Operational: energy restoration time management Ø Implementation, hardware: minimal n Electrical storage Ø Benefits: fully controllable, can inject energy into the system Ø Drawbacks, implementation: complex, requires power electronic converters, life expectancy, maintenance Ø Other: losses (standby), energy efficiency Ø Operational: recharging management Mc. Gill University 41 G. Joos

Distributed energy reources – scenarios 2020 n Scenario 1 – Low DG penetration (<10 %), connection mostly to the MV grid – business as usual Ø Reduction of impact on existing grid – power quality (flicker, voltage variation) Ø Source of power (MW) – limited contribution to voltage and frequency regulation Ø Islanding required in case of loss of mains n Scenario 2 – Increase in DER penetration (> 20 %? ), connection mostly to the MV grid – individual or in microgrids Ø Integration into the generation dispatch – need for monitoring and forecasting production (wind and solar) Ø Participation in ancillary services – voltage and frequency regulation Ø Requirements to remain connected for temporary loss of mains – low voltage ride through Mc. Gill University 42 G. Joos

Distributed energy resources – scenarios 2020 n Scenario 3 – Increase in the penetration of DER, with connection to the MV grid and the low voltage grid – PV panels, smaller units, controllable loads, including electric vehicles n For MV connections, same considerations as for Scenario 2 n For low voltage connections (residential, commercial), with a large number of units, a number of outstanding questions Ø Ø Ø Mc. Gill University Integration in generation dispatch – included? Participation in ancillary services – frequency/voltage regulation? Role of smart grids in managing a large penetration Financial consideration – generation (feed-in tariffs), ancillary services impacts on the grid – power quality (voltage rise), distribution system loading 43 G. Joos