Oahu Wind Integration Study - Hawaii Natural Energy Institute ...

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1.3. Challenges of operating Oahu’s system with high levels of wind power Large-scale wind power presents several potential challenges for operating a power system, particularly small island grids like the Oahu electrical system. This section describes some of these challenges and begins by discussing operation of the baseline system without any substantial variable renewable energy generation. Figure 1-3 illustrates the system load profile for a typical week for the Oahu system in a future year without any large wind or solar PV projects. 7 days Figure 1-3. An example of operation for the Baseline 2014 Oahu power system The graph shows the system load at a given point in time and the colors depict the dispatch of generating units to meet the load. The load profile of Oahu is characteristic of a residential customer base as tourism has a strong influence on the commercial sector. As such, system load does not deviate much from its profile. The system minimum load typically occurs from 10pm to 6am. The system day peak occurs between 12pm and 1pm and load remains relatively constant until the night peak between 6pm and 7pm. Generating units are characterized by three modes of operation: baseload, cycling and peaking. The baseload units are generally the largest and least-cost units to operate and remain online continuously throughout the year. These units are economically dispatched to meet system load. In Figure 1-3 the baseload units are situated at the bottom of the figure and consist of the Kalaeloa Combined Cycle plant, AES steam plant, and Kahe and Waiau reheat steam units. A small amount of baseload energy is provided by HPower (waste to energy), Honua (gasification) and OTEC (Ocean Thermal Energy Conversion). Honua and OTEC are not presently in operation, but were assumed to be in this future study year. Cycling units are smaller, non-reheat steam units. The cycling units are committed and shutdown daily to meet system demand and typically provide system up-reserves. The blue area represents cycling unit generation. The three peaking units are combustion turbines. These units are fueled by diesel fuel (Waiau 9 and Waiau 10) and biofuel (CIP-CT1). Four customer-owned diesel units can also provide peaking service. Peaking units are characterized as fast-start generation and are committed to meet peak demand and for system emergencies. The baseload plants remain online consistently and respond to a reduction in demand (load) in the off-peak period by reducing their power output. Each unit has a limit on how low it can 8
educe its output, while remaining in a stable operating state. Similarly, each unit has limits on how quickly it can adjust output (up or down) to meet changes in the demand (known as ramp rate limits). In the baseline system without wind power, some of the power plants reach their minimum operating constraints during the off-peak period. The variation in load (demand) does not challenge the capability of the units to change output (ramp up or down). Figure 1-4 contrasts the situation with a large amount of wind power added to the system. Scenario 5 Wind energy curtailment 7 days Figure 1-4. An example week of operation for the Oahu power system with 500 MW of wind power and 100 MW of solar power (Scenario 5) Figure 1-4 shows a simulation for the same period of time as that shown in Figure 1-3 with the addition of 500 MW of wind and 100 MW of solar power. The light green area represents the wind energy delivered to the system and the yellow area represents the solar energy delivered to the system. In this simulation, the renewable resources were added to the baseline system without incorporating any strategies or modifications to system operation. The system cannot accept all available wind energy during the system minimum load periods so excess wind energy is curtailed as represented by the grey shaded area. During the periods of wind curtailment, the thermal units are operating at a very low power output. Later in the report, the study results will show that more wind energy can be accepted by the system if operational strategies are implemented. The study also analyzed the variability of these renewable resources and its impact on the system. Figure 1-5 illustrates a significant change in wind power output on the third day of another week. 9
Page 1 and 2: Oahu Wind Integration Study Final R
Page 3 and 4: 1.0 Executive Summary Hawaii is an
Page 5 and 6: Oahu 100MW Wind 100MW PV Lanai 200M
Page 7: Figure 1-2. Renewable Integration S
Page 11 and 12: Figure 1-6. Share of annual energy
Page 13 and 14: Figure 1-8. Total annual variable c
Page 15 and 16: extreme downward variability over t
Page 17 and 18: 1.6. Short-timescale wind variabili
Page 19 and 20: Figure 1-11. Frequency performance
Page 21 and 22: down-reserve requirement. Alternati
Page 23 and 24: capability, the remaining 163 MW of
Page 25 and 26: o Table 1-2 showed that nearly 95%
Page 27 and 28: 1.8.2. Thermal Unit Modifications
Page 29 and 30: 6.3.1. Overview of the GE MAPS TM B
Page 31 and 32: 10.5.3. Down-reserve...............
Page 33 and 34: Figure 6-13. Baseline 2014 scenario
Page 35 and 36: tripped off-island wind plant carry
Page 37 and 38: Table 8-10. Summary of short-term a
Page 39 and 40: 2.0 Acknowledgements Our team would
Page 41 and 42: are presented in this section for S
Page 43 and 44: 4.1. Study objectives The General E
Page 45 and 46: human decision-making play a substa
Page 47 and 48: Voltage Governor Support Response P
Page 49 and 50: maneuvering that may be a result of
Page 51 and 52: hours of operation that warrant fur
Page 53 and 54: and maintenance costs) based on ass
Page 55 and 56: Another factor for consideration is
Page 57 and 58: Figure 5-3 GE MAPS TM model results
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models of all of HECO-owned and IPP
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Table 5-4 Proposed thermal unit gov
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Table 5-6 Summary of various dynami
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Table 5-8. Dynamic Database - Excit
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o 50 MW Oahu2: Modeled as a 50 MW g
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400 MW Off-island Oahu Wind Plant M
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turbine/governor systems in the dyn
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Pulsating logic: o All units under
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Hz 60.8 60.6 60.4 60.2 60 Frequency
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modeled as a single CT/ST and is ba
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6.2.1. Development of Wind and Sola
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Estimated power curve P farm = 30MW
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Figure 6-3 The largest 1 minute win
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Figure 6-5. Histogram of wind power
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At the request of the evaluation te
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6.2.5. Reserve requirements The Oah
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Figure 6-10. Thermal unit heat rate
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6.3.1.5.2. AES coal-fired steam pla
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Figure 6-12. Baseline 2014 scenario
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Methods to forecast solar power wer
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1. No forecast of wind and solar (S
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Table 6-3. Scenario 5: Wind and sol
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Figure 6-18. Scenario 5. Fuel energ
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Table 6-4. Scenario 3: Wind and sol
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6.7. Conclusions As the wind energy
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Figure 6-21. Scenario 3. Fuel energ
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The results of the scenario analysi
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Reduce On-line Regulating Reserves
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energy is accepted, these units are
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Figure 7-3. Scenario 5C: Fuel energ
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Sce nario 5C Scenario 5F1 40MW down
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Scenario 5F1 Scenario 5F2 Seasonal
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7.4.1. Sensitivity to Solar Forecas
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on the time of day and the load lev
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Figure 7-15. Scenario 5F3. Number o
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Figure 7-18. Renewable energy deliv
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more expensive cycling energy displ
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Figure 7-23. Delivered wind energy
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18-weeks during the year was includ
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should be noted that the effective
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Note that the average heat rate for
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The heat rate by unit type is shown
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The capacity factors of the renewab
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On the other hand, short-term analy
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Table 8-2. Long term screening resu
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Figure 8-4. Drop in wind and solar
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emain flat in their generation for
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Hz Hz 60.2 60 Frequency AGC Mode 59
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Figure 8-9. Long-term analysis for
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The up-range adequacy of the system
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The short-term screening results fo
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MW 120 100 80 60 40 20 0 0 600 200M
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Hz Hz 60.2 60 59.8 59.6 59.4 0 600
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events., which will be described la
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Figure 8-18. Down-range10 at the be
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o Frequency performance (Section 8.
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MW 450 400 350 300 250 200 Scenario
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8.5.3. Results Using the volatile w
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MW 80 60 40 K2 K3 K4 K5 K6 MW 100 2
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Figure 8-30 shows that the maneuver
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• The load flow model in GE PSLF
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Frequency RMS (Hz) 0.035 0.03 0.025
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Intermediate Farm power 1 1+ sT + _
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In step 2 above, the 0.1% percentil
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1 / 120 per unit Ramp Rate Power (M
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MW 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0
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MW MW 1.800 1.600 1.400 1.200 1.000
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Under the scenarios considered in t
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- No response (base case) - Moderat
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Hz MW 62 61.5 61 60.5 System freque
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esulted in noticeable improvements
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In both scenarios none of the 200 M
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Figure 8-49: Transient simulation r
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Figure 8-52: Transient simulation r
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o Wind turbine inertial response tr
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o Reducing the on-line regulating r
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9.2.5.3. Wind Plant Ramp Rate Limit
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o Given the high power rating of th
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power, thereby contributing to the
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10.1.5. Recommend that HECO evaluat
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10.2.2. Recommend solar plants to p
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o This recommendation assumes that
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acking down thermal units. In Scena
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o In Scenario 5F3 and 5F2 the regul
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10.5.5. Additional Operator Informa
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simultaneous occurrence of the larg
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