Adam Sparacino EPIC 2018

Grid Impacts and Modeling of Inverter‐Based Generation Adam R. Sparacino Senior Engineer Power Systems Engineering Division Mitsubishi Electric Power Products Inc. adam.Sparacino@meppi.com Electric Power Industry Conference/University of Pittsburgh October 15, 2018 COMPANY PROPRIETARY

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Increasing Penetration of Renewables

Electricity generation from selected fuels billion kilowatthours 2017 3,000 history projections

30 0

2,500

2017 projections

25 0 0

2,000

natural gas

1,500

20 0

15 0 0

renewables

1,000

coal

500

10 0

nuclear 50

Reference case 0 1990

Low Oil and Gas Resource and Technology

0

2000

2010

2020

2030

2040

2010 2020 2030 2040 2050 2050

U.S. Department of Energy (DOE), On the Path to SunShot DOE, Wind Vision Report U.S Energy Information Administration (EIA), Annual Energy Outlook 2018 COMPANY PROPRIETARY

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Single Line Diagram of a Feeder in a PV Plant

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PV Inverter Single Line Diagram

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Control Objectives of a Renewable Power Plant Controller •

•

The power plant controller controls the overall plant performance by giving set point commands (P, Q) to the individual inverters and adjusting the status of plant level shunt compensation and the tap setting of the station transformers LTC. Typically contain voltage, Var, and power factor control (some newer systems have power‐frequency droop).

Station Transformer POI Gen-Tie Line

MV Bus

Other parallel feeders Feeder N

Fixed or Dynamic Shunt Compensation

Feeder 2 Feeder 1

Vpoi

Q P

Q

P

PV

Q

P

PV

Q

P

PV

Power Plant Controller COMPANY PROPRIETARY

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PV Plant PQ Capability Curve (Example 1)

Reliability Guideline: Inverter-Based Resource Performance, NERC, September 2018 COMPANY PROPRIETARY

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PV Plant PQ Capability Curve (Example 2)

Reliability Guideline: Inverter-Based Resource Performance, NERC, September 2018 COMPANY PROPRIETARY

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Short‐Circuit Capacity Impact on Controls Systems •

When installing a power electronic device into a power system it is important to consider a range of possible system conditions.

•

The Short‐Circuit Ratio (SCR) – the relative size of a inverter and the system short‐ circuit capacity at the point of interconnection (POI) for the inverter have an impact on the stability of the inverter. ܵ‫ ܴܥ‬ൌ

‫ܣܸܯ‬ௌ௬௦௧௘௠ ‫ܣܸܯ‬ሺூ௡௩ሻ

Minimum Short-Circuit Capacity

Maximum Short-Circuit Capacity (3x Min.)

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Practices for Power System Modelling of PV/Wind Plants •

The PV/Wind plant are modeled using a single‐machine equivalent.

•

The equivalent generator and associated PF correction capacitors (if needed) represent the total generating capacity of all generators.

•

The equivalent generator step‐up transformer (pad‐mounted transformer) represents the aggregate effect of all WTG/PV step‐up transformers.

•

The equivalent collector system represents the aggregate effect of the PV/Wind plant collator system and should approximate real power losses and voltage drop out to the “average” PV/WTG.

Type 1 and 2 only

Single-Generator Equivalent Power Flow Representation PV/Wind WECC Wind Power Plant Power Flow Modeling Guide, WECC, 2008 COMPANY PROPRIETARY

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Control Block Diagram of a PV Inverter

Fast inner current control loop (kHz) regulates magnitude and phase of inverters generated voltage waveform. (Not modeled in PSS/E)

Phased locked loop (PLL) tracks the phase angle of grid voltage enabling the control system to follow the grid (Not modeled in PSS/E)

Slower outer loop controls modeled in PSS/E

Study and Development of Anti-Islanding Control for Grid-Connected Inverters. GE, 2004 COMPANY PROPRIETARY

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Weak Grid Response of a PSS/E and EMTP Model of an Inverter • • •

Response of an inverter to a 3LG fault in a “weak” grid.

The PSS/E model has no consideration of the fast inner loop controls or the PLL and as such responds “well” during this event.

The EMTP models show instability due to the tuning of the PLL/fast inner loop controls PSS/E Simple EMTP Detailed EMTP

Three Phase weak grid analysis of converter interfaced generation, EPRI, 2018 COMPANY PROPRIETARY

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Questions?

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