Grid Forming Inverters in Interconnected Systems

Transcription

1 Grid Forming Inverters in Interconnected Systems P R E S E N T E D B Y Abraham Ellis aellis@sandia.gov SAND C CO- AU T H O R S Brian Johnson, University of Washington Rober t Lasseter, University of Wisconsin Yashen Lin, National Renewable Energ y Laborator y Ryan Elliott, Brian Pier re, Sandia National Laboratories Joseph Eto, Lawrence Berkeley National Lab Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy s National Nuclear Security Administration under contract DE-NA

2 2 The grid of the future More wind and solar generation, more storage, more electronic load (e.g., EV). All distributed and inverter-based Lower system inertia, faster dynamics, more challenging control requirements. Extremely difficult to approach 100% share in large interconnected systems. Grid Forming Inverters deserve careful consideration as a potential solution.

3 Grid following Vs grid forming inverter controls Two fundamental types of inverter controls Grid Following Control (GFL) Controls current and phase angle Grid Forming Control (GFM) Controls voltage magnitude and frequency Control of active & reactive power as well as fault currents Instantaneously balances loads without coordination controls Cannot operate standalone Cannot achieve 100% penetration Can operate standalone Can achieve 100% penetration

4 GFM inverters were studied and deployed in DOE/CERTS microgrids Santa Rita Jail Microgrid, dedicated 3/22/2012. Static disconnect switch at the point of common coupling Five 2.3 kw wind turbines Utility Interface Two 1.2 MW backup diesel generators Distributed Energy Resources Management System (DERMS) 1 MW fuel cell 2 MW/ 4 MW-hr energy storage system When a disturbance to the utility grid occurs, the automatic disconnect switch enables the facility to island itself from the main utility grid. 1.2 MW rooftop solar PV system

5 GFM inverters were studied and deployed in DOE/CERTS microgrids Seamlessly switches between grid and island operation and back Stable without communications Sources are plug-and-play Proven in microgrid applications E. Alegria, T. Brown, E. Minear, R. Lasseter, CERTS Microgrid Demonstration With Large-Scale Energy Storage and Renewable Generation,, IEEE Transactions on Smart Grid, Vol. 5, No. 2, March C. Marnay, N. DeForest, M. Stadler, J. Donadee, C. Dierckxsens, G. Mendes, J. Lai, and G. F. Cardoso, A green prison: Santa Rita Jail Creeps Towards Zero Net Energy (ZNE), in Proc. ECEEE, 2011.

6 6 What about GFM inverters operating as part of large grids? Many open questions How do GFM inverters behave in a large interconnected system? How does a system defined by GFM inverters behave? What are the fundamental dynamic characteristics? What are the most promising GFM control architectures? What functions & operating modes are required? How are the GFM inverter hardware requirements? How do we protect the network? What are the modeling gaps for large-scale simulation? etc., etc.

7 7 Preliminary observations frequency control with low inertia Simulated frequency response for 5% load drop event, as a function of residual inertia 20% 50% 80% Grid following (GFL) inverters with freqwatt functionality (a) (b) (c) Grid forming (GFM) inverters Time(s) Time(s)

8 8 Case study O ahu, Hawai i, 50% distributed PV System at 920 MW load, 466 MW PV Event is loss of 62 MW load GFL controls w/ frequency-watt function GFM CERTS controls GFM inverters responds much faster Frequency Aggregated PV output

9 9 Case study O ahu, Hawai i, 50% distributed PV System at 1,080 MW load, 540 MW PV Event is loss of 200 MW generator M. E. Khatib, W. Du, R. Lasseter, Evaluation of Inverter-based Grid Frequency Support using Frequency-Watt and Grid Forming PV Inverters, SAND ID # GFM CERTS controls GFL controls with frequency-watt function Better frequency control avoids load tripping Load tripping events Frequency Total System Load

10 10 A current USDOE GFM controls project, led by NREL Develop and implement in hardware GFM controls, specifically Virtual Oscillator Controls (VOC) Study methods to aggregate distributed inverters for large-scale simulations Assess GFM modeling requirements for large-scale simulation platforms (e.g., PSSE, PSLF) Compare performance vs. GFL inverters for increasing % share Identify research gaps and priorities for possible future investment

11 11 GFM/VOC project Controls development, hardware implementation The VOC is implemented and tested in two sets of hardware test beds: NREL customized multiinverter hardware test bed. Off the shelf multi-inverter hardware test bed with SunPower. Johnson BB, Sinha M, Ainsworth NG, Dörfler F, Dhople SV. Synthesizing virtual oscillators to control islanded inverters. IEEE Transactions on Power Electronics Aug;31(8):

12 12 GFM/VOC project Model aggregation for system studies Developed model aggregation method, validated using prototype VOC inverters [2] Scaling laws for grid forming: M. Khan, B. Johnson, V. Purba, and S. Dhople, A Reducedorder Aggregated Model for Parallel Inverter Systems Controlled with Virtual Oscillator Control, Workshop on Control and Modeling for Power Electronics, 2018.

13 13 GFM/VOC project Model aggregation for system studies Custom PSLF model of GFM VOC controls Preliminary simulation results with 39-bus system representative of large grid (e.g., WECC) Refinement and validation efforts under way System at ~50% share of inverter-based generation (PV) Simulated a generator trip (Unit 10, ~4% of pgen)

14 14 Upcoming USDOE Workshop You are Invited! Grid-Forming Inverters for Low-inertia Power Systems February *, 2019 NREL, Golden Colorado, USA Confirmed Speakers: Vijay Vittal (ASU), ark Ahlstrom (NextEra Energy), Danny Zimmanck (Enphase), Thibault Prevost (RTE), Alejandro Domingues Garcia (UIUC), Aranya Chakraorty (NCSU), Marcelo Colombino (NREL), Scott Mason (SEL), Kevin Schneider (PNNL), Duncak Calloway (UC-Berkeley), David Porter (S&C Electric), Deepak Romasubramanian (EPRI), Ulrich Muenz (Siemens), Philipp Strauss (Fraunhofer-IWES) For more information, contact: Brian Johnson, Yashen Lin, Abraham Ellis, This workshop will gather experts from universities, research institutes, equipment manufactures and utilities interested in Grid Forming Inverters. Participants will review the state-of-the-art, and identify future research needs.