Grid Integration of Renewable Energy. Robert S. Kaneshiro, P.E. Operations Assistant Superintendent Hawaii Electric Light Company (HELCO)

Transcription

1 Grid Integration of Renewable Energy Robert S. Kaneshiro, P.E. Operations Assistant Superintendent Hawaii Electric Light Company (HELCO) October 2012

2 Contents HELCO System Overview Challenges of integrating solar at the distribution level System-wide operations issues that arise in small systems with large levels of renewables.

3 HELCO System Overview Autonomous system (no interconnections) Minimum load ~90MW Day peak ~160MW Evening Peak ~180MW Automatic Generation Control (AGC) performs frequency control and economic dispatch. Renewable energy available from wind, hydro, geothermal and solar.

4 HELCO System Overview (cont d) Generation Capacity: Conventional (Fossil Fuel) unit dispatchable by AGC Must-Run (24-hour) Units 3-Steam Units (49MW) 2-Combined Cycle Combustion Turbine Units (55MW) 1-Geothermal (27MW off-peak, 30MW on-peak) Intermediate Units 2-2 nd Combine Cycle Combustion Turbine Units (55MW) 1-Simple Cycle Gas Turbine (20MW)

5 HELCO System Overview (cont d) Generation Capacity (cont d): Peaking/Emergency Units 2-Simple Cycle Gas Turbines (25MW) 14-Small Diesel Generators (28MW) Reserve Units (Requires >12hrs notice) 2-Small Steam Units (15MW)

6 HELCO System Overview (cont d) Generation Capacity (cont d): Renewable Must-Run unit dispatchable by AGC Geothermal (38MW) Must-Take (As-Available) Wind (30MW) Run-of-River Hydroelectric (15MW) Distributed Generation Feed-In Tariff Net Energy Metering No Sale Schedule Q

7 2000 Energy Source Simple Cycle, 17.4% Diesel, 7.7% Hydro, 4.4% Combined Cycle, 3.8% Other, 29.8% Geothermal, 23.9% Steam Combined Cycle Simple Cycle Diesel Hydro Geothermal Wind Steam, 41.3% Wind, 1.5%

8 2012 YTD Energy Source Simple Cycle, 0.3% Diesel, 0.3% Hydro, 5.4% Combined Cycle, 37.3% Other, 40.9% Geothermal, 22.5% Wind, 13.0% Steam Combined Cycle Simple Cycle Diesel Hydro Geothermal Wind Steam, 21.2%

9 Renewable Energy Percentage Duration June RE / Sys Load (%) RE+PV RE Duration (Seconds)

10 Average Daily %RE Profile 70% 60% 50% RE / System Load (%) 40% 30% %RE Hi Lo 20% 10% 0% 3:00 6:00 9:00 12:00 15:00 18:00 21:00 June 2012

11 Growth of DG (Primarily PV) MW Planned (MW) Installed (MW) <= * 2013* As of August 2012

12 Distributed Generation PV Hydro Wind FIT 250kW - - NEM 13,579kW 49kW 121kW No Sale (SIA) 3,096kW - 40kW Schedule Q 100kW 168kW - TOTAL 17,025kW 217kW 161kW As of August 2012

13 Challenges of Integrating Solar at the distribution level

14 HELCO has: 64 Distribution Substations island-wide 143 Distribution Circuits Until recently, any circuit that had DG more than 15% of the peak load required an engineering study.

15 Traditional distribution power circuits: Power flows from distribution substation to the loads; as loads increase so does current flow, and voltage decreases. Substation transformer Load Tap Changers (LTC) automatically adjusts as load changes to maintain the circuit voltage within ±5%. Distribution transformers are normally installed with a common tap setting regardless of its location. Voltage regulators and capacitors are strategically placed on the distribution circuit to help maintain voltage on longer or heavier loaded circuits.

16 With the installation of Distributed Generation (DG): Power does not always flow from distribution substation breakers to the loads; depending on where the DG is located (and time of day for PV), it becomes challenging to determine the voltages on the distribution circuit. Distribution circuit voltage may not be adequately adjusted by the substation transformers Load Tap Changer (LTC) as the substation may not have sufficient voltage feedback. Same applies to voltage regulators. Equipment that regulate voltage may end up operating more often and require more maintenance. Modeling of distribution circuits have numerous assumptions, with countless number of scenarios. Testing of the models require feedback from actual installations.

17 Modeling of distribution circuits require: Complete diagram of circuit, including all branch circuits, power equipment, distributed generation and loads. Distribution circuit impedance based on conductor quantity, length, size, material, arrangement and spacing Model of customer load profile and distributed generation resource.

18 Challenges of creating/up-keeping distribution circuit models: Time required to collect necessary information. Time required to construct model. Model is constantly evolving with new construction, demolition, and customer changes (moving in addition to modifications). Model must be validated against actual data before it can be accepted. Does not take operational load transfers in to consideration.

19 Circuit Customer Count , ,694

20 Distribution Circuit Load

21 System Issues due to large levels of Renewable Energy

22 Renewable Energy Impacts To HELCO System System Load Reduction Operating traditional units at less efficient levels. Traditional units are forced to deep cycle and/or shut down. Adds challenge to incorporate new renewable energy. Challenges in forecasting System Loads It is unknown how much power is generated by the DG at anytime. Errors cause over or under commitment of units.

23 Renewable Energy Impacts To HELCO System (cont d) Adds another variable when restoring power, and could be very problematic when restoring from an island-wide outage. As penetration becomes greater, there may be other unintended consequences (risks).

24 Generation and Load Low Amount of Must-Take :00 6:00 9:00 12:00 15:00 18:00 21:00 System Load Regulating Renew Geothermal Sys_Load Base+Int BaseLoad

25 Generation and Load High Amount of Must-Take :00 6:00 9:00 12:00 15:00 18:00 21:00 System Load Regulating Renew Geothermal Sys_Load Base+Int BaseLoad

26 Generation and Load Lower Minimum Loads on Must Run :00 6:00 9:00 12:00 15:00 18:00 21:00 System Load Regulating Renew Geothermal Sys_Load Base+Int BaseLoad

27 Generation and Load Variable Winds/Commitment Errors :00 6:00 9:00 12:00 15:00 18:00 21:00 System Load Regulating Renew Geothermal Sys_Load Base+Int BaseLoad

28 Load Change over past 5 years System Load (MW) Besides decrease in overall load, notice daytime load profile has flattened out :00 06:00 09:00 12:00 15:00 18:00 21:00 Thursday before Good Friday

29 Current Load Profile with estimated PV load added Load (MW) Calc_Tot SYS_MW EST_PV :00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 October 1-7, 2012

30 Extrapolated Load profile with 28.2MW (+65%) PV Load (MW) PV +65% Future_LD :00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 6:00 12:00 18:00 October 1-7, 2012

31 Variability of Solar

32 Unexpected Fast Change in System Load System Load (MW) System Load decreased about 3MW within 8-minutes. Overall PV generation was estimated to increase from 6MW to 8MW, primarily occurring on the west side of the island :1 12:15:00 12:2 12:25:00 12:3 12:35:00 12:4 Thursday, February 16, 2012

33 Frequency Disturbance Early PV Inverters are set to trip when frequency is below 59.0hz System Load (MW) On Sept 21, a generator tripped off-line unexpectedly and frequency dipped to 58.85hz. After 20-seconds of frequency below 59.3hz, the Kicker block of Underfrequency Loadshed operated Frequency (Hz) SYS_LOAD FREQUENCY It was estimated that there was 4MW of PV generation at the time, and some of the inverters tripped as a result of the frequency :47:30 8:48:00 8:48:30 8:49:00 8:49:30 8:5 8:50:30 Friday, September 21, 2012

34 Momentary Interruption of Power Line 6500 Load (MW/MVAR) On July 19, there was a significant load increase following transmission line fault, something never noticed before. There was also a load change that appear to be a PV inverter switching off and on :3 12:35:00 12:4 12:45:00 Thursday, July 19, System Frequency (Hz) 6500 MW 6500 MVAR FREQUENCY Estimated 400kW PV generated At the time.

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36 How to Mitigate Impacts Be informed of the risks: Perform a System Impact Study that will at a minimum examine: Fault analysis / System stability Equipment protection coordination System frequency response Unit Cycling Analysis Generation reserve requirements Forecasting strategies

37 Other Considerations DG Standards review/updates. Costs for making changes to DG equipment if it becomes necessary. Excess energy / Curtailment policies and procedures.

38 Questions?

39 Have a nice day!