PV Grid Integration Research in the U.S.

Transcription

1 PV Grid Integration Research in the U.S. Barry Mather Ph.D. NREL- Power Systems Engineering Center HEPIA IEA PVPS Task 14 Utility Workshop Geneva, Switzerland March 31 st, 2014 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

2 Presentation Overview Photovoltaic solar integration on distribution systems in the U.S. U.S. PV market overview NREL/SCE High-penetration PV grid integration project Advanced screen development for distribution interconnection (EPRI/NREL/SNL) Wind and solar integration on the U.S. Western Interconnection WWSIS II WWSIS III

3 U.S. PV Market Overview Graph credit: SEIA seia.org Total installed solar is about 13 GW at year-end 2013 Roughly 10 GW of PV, 3 GW of CSP Of installed PV, about 60% is large scale utility PV

4 NREL/SCE High-Pen PV Project 1.5 MW Auto-Cap 1.8 MVAr PV 3 MW Auto-Cap 1.2 MVAr PV Substation Auto-Cap 1.8 MVAr I I RCS I I X PS X PS I I PS Auto-Cap 1.2 MVAr R Adjacent Feeders Focus developing new rules of thumb for utility planning engineers for interconnecting large (1-5MW) PV systems on medium voltage (MV) distribution circuits and developing methods to reduce the PV impacts on these systems 4

5 Comparison of Quasi-Static Time-Series and Transient Simulation Analysis Techniques IEEE 8500 node test feeder model Evaluated quasi-static time-series analysis results at multiple time steps over a 16 minute period Analysis run times are on the order of 5 hours for PSCAD and 5 seconds for OpenDSS PSCAD OpenDSS 5s 10s 15s 30s 40s 50s Max Load tap Min changer # of actions Max A Min # of actions Max Reg. #3 B Min # of actions Max C Min # of actions Cap. #1 Opening time (s) See: D. Paradis, F. Katiraei and B. Mather, Comparative analysis of time-series studies and transient simulations for impact assessment of PV integration on reduces IEEE 8500 node feeder, IEEE PES GM, Vancouver, Canada, July,

6 Voltage (PU) Inclusion of the Control Dynamics Voltage (PU) Voltage (PU) PV 1 Interconnection Point Voltage Phase A Phase B Phase C Voltage at Voltage Regulator #2 Phase A Phase B Phase C Time (Second) Time (Second) Voltage at Capacitor #1 Phase A Phase B Phase C Time (Second) 6

7 Voltage (pu) Q/Rated P (%) Modeling Disparate PV Mitigation Controls Voltage at PCC of multiple PV with different mitigation controls Reactive power contribution with different mitigation controls PV1, PF = -0.9 PV2, PF = -0.9 PV3, PF = PV1, Drop Coef = 4% PV 2, PF = -0.9 PV3, Const Q = 25%*Rated P PV1, PF=-0.9 PV2, PF=-0.9 PV3, PF=-0.95 PV1, Drop Coef=4% PV2, PF=-0.9 PV3, Q=25% Rated P Time (Second) Time (Second) Study conclusions show that supervisory controller interaction may more stable than originally hypothesized, equity in var production as a % of real power produced may be a more important interaction between disparate mitigation control types 7

8 Anti-Islanding Testing via PHIL PHIL Implementation Dist. Cir. Model High-bandwidth emulation of the timevarying impedance of the PCC By modeling the distribution system point of common-coupling (PCC) complex impedance with a higher bandwidth than the PV inverter s anti-islanding function, it is possible to evaluate the PV inverter s performance as if it were installed on the distribution circuit 8

9 AI Testing via PHIL Initial Results PHIL P=8kw Q = 4 Trad. Load Bank P=8kw Q = 4 PHIL AI testing seems possible but we really need to test this at high-power (100+ kw) where PHIL AI testing is very advantageous 9

10 Dev. of Adv. PV Interconnection Screens Collaborative project with EPRI, NREL, SNL and CA utilities to develop advanced screening methods for distributed PV grid interconnection Advanced screens will inform CA Rule 21 and will allow more PV to be interconnected quickly when those systems will not adversely effect the interconnected system and will reduce utility interconnection queue 15% 10

11 Review of Utility Interconnection Screens California Rule 21 Initial Review Screens 1. Not a secondary network 2. Not exporting across PCC 3. Certified equipment 4. <15% of peak load in line section 5. Starting voltage drop within limits 6. <=11 kva nameplate rating If > 11 kva rating 7. Nameplate and short circuit contribution ratio within limits 8. Compatible transformer connection If project passes all screens, interconnection agreement approved Source: SCE Rule 21 Generating Facility Interconnections, August

12 General Survey Findings Common Practices Include: Online applications, guidelines Low-cost/no-cost application Uniform state rules for all utilities (e.g. Rule 21) Standard approach to evaluating applications Supplemental screening options Standardized distribution modeling platform Emphasis on good communication with applicant Online tracking system Standard impact studies (when required) 12

13 Specific Survey Responses: PV Penetration The technical screen fast track advisory limits are 2 MW for 12 kv circuits, and 3 MW for 21 kv circuits. Circuits rated at 12 kv and 16 kv are allowed to have a maximum of 450 Amps of generation, which is about 10 MW on the 12 kv circuits and 13.5 MW on the 16 kv circuits. The rule of thumb within the engineering departments has been a maximum of 10 MW of DG on any feeder. We use 100% of minimum daytime load or 30% of the daytime peak load as a penetration parameter, rather than 15% of minimum 24/7 load, for PV system screening. 13

14 Specific Survey Responses: Hi-Pen Mitigation Developers are asked to operate their systems with a power factor of +/ PF which may be moving towards +/ PF at some point in time. Voltage regulation devices are reset, relocated or sometimes replaced with new bi-directional regulators for large systems. Regarding modifications to system protection: Both distribution and transmission are considered. System Protection evaluates all reclosers and fuses 150 Amps and above. 14

15 Western Wind and Solar Integration Study 2 (WWSIS2) Generation 5-min. dispatch for high solar scenario - July Energy Penetration: 25% Solar (PV & CSP), 8% Wind

16 Western Wind and Solar Integration Study 3 (WWSIS3) in progress outlook 10.3 GW of PV 21.6 GW of Wind Light Spring System Loading WWSIS3 includes the bulk system response to large amounts of DG (mostly PV) interconnected in California

17 Thank you for your attention Contact: Barry Mather Ph.D. National Renewable Energy Laboratory