Introduction to MicroGrids- Integration of Renewable Energy Nguyen Huu Phục Email: nhphuc@hcmut.vn; nhphuc123@yahoo.com; Klipsch School of Electrical- Computer Engineering New Mexico State University Microgrid Definitions °U. DOE: A microgrid is a localized grouping of electricity sources and loads that normally operates connected to and synchronous with the _ traditional centralized grid (macrogrid), but can disconnect and function autonomously as physical and/or economic conditions dictate. *CIGRE Working Group: Microgrids are electricity distribution systems containing loads and distributed energy resources, (such as_ distributed generators, storage devices, or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while islanded. What is a Microgrid? That Was Then.
Legacy Bulk Electrical System. Lhis is Now Microgrids Generation End Use Transmission Distribution (high voltage) (medlum voltage, T. KHANH = 2 DS: Distribution Substation TL: Transmission Line wl. 4P a $ ps $27 oy ri eee ate 2 HÀ HÀ ne B89 RD What is a Microgrid? Microgrid — Grid-Connected Mode Microgrid — Islanding Mode ti BP © s0 _§ x ¬ - DS cân awa | @ DS To a system operator, a | Geeta aie Lf microgrid looks like a treats tt T7)! GH controllable load or l| PT Lí Xi Hi Pte ol generator lÌ [EEBBI x Ì „ a TIL LIN ighbourhood |" + @ What is Microgrid? elt is connected to both the local generating units and the utility grid thus preventing power outages.
eExcess power can be sold to the utility grid. ¢Size of the Microgrid may range from housing estate to municipal regions. ° Introduction To Microgrid ¢ Microgrid Components e Distributed Generation e Loads e Immediate storage e Controller e Point of Common Coupling Typical Microgrid is shown below: In the event power is severed from commercial sources. Microgrid Operating Modes ® Grid Connected Mode: = Feeder A ¢ Utility grid is active.
Y \ 4 _ FeederB - ® Static switch is closed Tự \ + ¢ All the feeders are being ti i _ Feeder C supplied by utility grid. eh : a Point of B A ae Feeder D , ove Microgrid Operating Modes ® Island Mode: * Utility grid is not supplying power * Static switch is open. e Feeder A, B, C are being supplied by Microsources. e Feeder D (not sensitive ) is dead.
Feeder A Feeder B State Switch Open =P Point of Common T1 : Coupling The Need Of Microgrid Interconnected Microgrids Interconnected Microgrids — Power Parks e Microgrid could be the answer to our energy crisis. e Practical size of Microgrids is limited to a few MVA. e Transmission losses gets highly reduced. e For larger loads, it is desirable to interconnect many e Microgrid results in substantial savings and cuts Microgrids to form a larger Microgrid network called emissions without major changes to lifestyles.
e The advantages of this Microgrid structure insures + EO a ete ae rear ae eek sappy to greater stability and controllability for the Power Parks. critical loads Environmental Aspects Conventional Grid vs. Microgrid e Efficiency of conventional grid is very low as compared e Microgrid encourages the use of the renewable energy to Microgrid sources. : : e Large amount of energy in the form of heat is wasted in e Large land use impacts are avoided.
as elionclieta grid. ¢ CO2 Emissions are reduced. j ; : s Power sources in case of Microgrid (often referred to as Microsources) are small and are located in close proximity to load. Advantages & Disadvantages e Microgrid Advantages e A major advantage of a Microgrid, is its ability, during a utilit grid disturbance, to separate and isolate itself from the utility seamlessly with little or no disruption to the loads within the Microgrid.
¢ In peak load periods it prevents utility grid failure by reducing the load on the grid. ¢ Significant environmental benefits made possible by the use of low or zero emission generators. Advantages & Disadvantages e¢ Microgrid Advantages e The use of both electricity and heat permitted by the close proximity of the generator to the user, thereby increasing the overall energy efficiency. e Microgrid can act to mitigate the electricity costs to its users by generating some or all of its electricity needs.
Advantages & Disadvantages ¢ Microgrid Disadvantages ¢ Voltage, frequency and power quality are three main parameters that must be considered and controlled to acceptable standards whilst the power and energy balance is maintained. ¢ Electrical energy needs to be stored in battery banks thus requiring more space and maintenance. e Resynchronization with the utility grid is difficult. Advantages & Disadvantages ¢ Microgrid Disadvantages ¢ Microgrid protection is one of the most important challenges facing the implementation of Microgrids.
¢ Issues such as standby charges and net metering may pose obstacles for Microgrid. ¢ Interconnection standards needs to be developed to ensure consistency. IEEE P1547, a standard proposed by Institute of Electrical and Electronics Engineers may end up filling the void. Ideal Components of a Microgrid = Distributed Energy Resources = Generation “% @ = Storage &¿) ar = Flexible Loads ATA & js.
= Metering " Control a * Protection my & “ Communications = a Comparison How does this differ from a backup system, like what a campus has? Microgrid Campus w/ Backup Power System Bi-directional Flow Possible No (unidirectional) Functionality Controllable entity Uncontrollable load Generators Operation Always on As needed Mode Switching Seamless Disconnect/reconnect (blip) Loads Flexibility High Low Primary Source Grid/DER Grid ø Microgrid Challenges Voltage Regulation «High impedance (weak) system, non-radial source-demand configuration, multiple sources Increased Harmonics = Weak system, non-radial source-demand configuration, multiple sources Maintenance Safety « Non-radial configuration poses complex maintenance strategy Feeder Increased Short Circuit Levels 0 al * Sources close to loads. feed from multiple sources Oe Microgrid Challenges = Coordination of Protection Devices and Sensitivity "Multiple sources, de-sensitized radial protection schemes = Impact from High Penetration = Multiple and complex sources are difficult to model, utility resistance to experimentation = Islanding Control and Synchronization = Re-closure synchronization may be difficult with multiple generators, detection schemes may lack sensitivity đi = Legacy infrastructure and government policy = Existing systems can be expensive to upgrade, existing government policy restricted to nearly homogeneous power quality 11 Microgrid Operation and Control Operation and Control Outline Operational Issues to Consider = Stability (momentum and firmness) = Constantly changing demands may not match generation capacity = High impedance = Voltage issues and feeder upgrades are required = Synchronization = Solid communications is required for all DER = Transients = Microsecond speed events can resonate system Operational issues Controls Modes of operation Central controller / Intelligent agent 12 Control Aspects = Distributed Energy Resource Control = Coordinates demands with generation (P,V,Q Control) = Fast response to disturbances = Power and voltage control - load changes without relying on communications = Energy Management = Dispatching of power and voltage set points to each microsource controller = Demand response to load balance (instant and forecasted) = Minute timescale = Protection = Unique solutions to match network - ' 4 * Use of power electronics for DER “Control Aspects — System Parameters = Demand Voltage Frequency Efficiency optimization au Modes of Operation = Grid connected = Islanded Campus = Transition mode ( hi Transition mod ov an 2 AS F.—————— Modes of Operation and Control Many options for control to consider for each mode = Grid Connected Mode = Constant power mode for all DERs 14 Modes of Operation and Control = _ Islanded Control Options «= Master/Slave DER 1: Transfer to Master Mode DER 2: Slave Mode * Active Load Sharing = All DER transfer to voltage and frequency droop control for P and Q supply ; St | | +——— Open Loads Frequency and Voltage Control mm Master Constant Power Control | DER2 Slave 15 “mm Agent | \ j ¬” hag ⁄ Advanced Systems and Control — = Communications How fast is fast enough? = Wire/Fibre/Wireless = Information System = Grid/Load Controls Approach to Systems and Control Dependencies System Measurement systems? Economics Optimization (planned, real time) To generate or change demand: are they different ? Reliability DER Types Demand forecasting Energy forecasting Approach to Systems and Control Run of the River: 0.9 MWDiesel:1 MW G4 G1 G2 G3 Generation Monitoring and Optimization NWA PP 25 kV,3ph Intelligent Agent Demand Response Residential Meter “67 T3.v 5 KK Critical Load Backup Commercial Case Study: Boston Bar = Background Boston Bar Sub Station = Town of ~850 persons located ERT ee ee off the Trans-Canada ( Highway/Fraser River north-east wanna Z\ 00-25 kv of Vancouver ca A = Power System = BC Hydro grid-supplied by a 60 km, 69 kV line running through a | steep canyon that is frequently Bi a a a ccd subjected to rockslides, +aawriudsliđGS,}_ | storms, etc.s pr ©) -% ad frequently knocks out powerssmw | CH 4 i a.sskvG2 | At = Nearby independent powero.s pr | ¬ — 11,67 MVA producer (IPP) hydro-plant, 115 kva se ' Ipp Se AD Oe u “ '8%2L.22£% “v80: IfêliÊ2) rvice tet a * Canada Case Study: Boston Bar = Solution = Planned islanding of load (from BC Hydro grid) so that it can be fed from IPP Normal Inst. Trip Delay Trip Grid 60 Hz >60.5 N/A Connected Hz Dead Load 60 Hz <55, >67 Hz N/A Pickup Islanded 60 Hz <53, >67 Hz <59.5 State Hz, 20s All: Vin Cont: Delay 1 s: 0.1 = Went into development of IEEE 1547.4 guideline for intentional islanding experience 19 A Typical Remote Community Mini-grid Remote Communi ty = Atypical Canadian remote grid Electrical Systems =A HN mv Ga consists of a number of diesel Microgrids or Minigrids? or hydro generators serving community loads. = No communication between ARAKI supply and demand.
eT ae, = Balancing by generators and possibly dump loads. Residential Critical Commercial Load (> Jeese Backup oo oo ao] Po oBeE ORB aE A Typical Remote Community Mini-grid (100% Diesel) = Generator sizing strategy = Staged sizes to support most common demand profiles (i. winter demand, summer demand, service large commercial machine startups) = Generator backup sized for typical demand = Top 10% of demand often occur for small fractions of the total year (i. 20 An Ideal Advanced RC Mini-grid/Microgrid = Diesel Backup G2 G3 Generation Monitoring and —J / Load — “#VVVY* Demand Response Smart Meter ~X Network Commercial An advanced RC grid incorporates almost all elements of a typical microgrid, except for the grid connection Communication between supply and demand.
Balancing by all components of system. Load „ 21 An Ideal Advanced RC Mini-grid /Microgrid = Mix of generation sources and must be matched with demand AND total energy to guarantee the delivery of power = Combinations of dispatchable with non-dispatchable sources will require careful consideration to demand profiles — Why? Voltage and frequency vary with P+Q demands, parallel DERs can lose synchronization Voltage profiles can be difficult to maintain within +/-5% standard Remote Microgrids = Non-radial overcurrent protection can be difficult to synchronize and coordinate; may lack sensitivity = In effect, a remote community power system will reflect = Communications is key a microgrid if it balances supply and demand using (Advanced IT) resources from both sides, that is, generation optimization and load control/demand response.where such an approach is only possible with systems possessing the advanced communications infrastructure seen in the future smart grid. Remote Microgrid Implementation Benefits = Lower costs of generator operation = Reduced fuel consumption = Longer equipment lifetime = Diversified power generation = Increased renewables = More stable costs = Lower environmental impacts 22 = Increased customer engagement Types of Generation “ Dispatchable — can be used at a momenfs notice - _ Non-dispatchable - is not always available nor controllable “ Firm — can deliver a quaranteed quantity of power =" Renewable — uses replenishing natural resources such as water, sun, biomass, geothermal, wind * Induction/Synchronous - rotating machines susceptible to frequency fluctuations.