Presented by:Rojan Bhattarai

MVS Workshop: Gaps in Modeling Hydro Power Plant in Steady-state and Dynamic analysis

Team Members:Slaven Kincic1

Nader Samaan1

Sohom Datta1

Abhishek Somani1

Jin Tan2

Rojan Bhattarai3

Thomas M. Mosier3

1 Pacific Northwest National Laboratory2 National Renewable Energy Laboratory3 Idaho National Laboratory

Project Overview

❑Team with INL, NREL and PNNL is looking into gaps or issues related to current modelling approach of hydropower plant through:➢Industry Engagement and Discussion

➢Literature review

➢Performing simulation studies with varying dynamic model parameters

❑So far, the following gaps/challenges have been identified:➢Lack of incorporation of water availability (head height)

➢Lack of modelling of hydropower plant interdependencies

➢Inability to model rough zones

➢Issues with inaccurate frequency response compared to actual generators (arising from deadband, secondary control loop etc.)

➢Erroneous parameterization leading to Pgen > Pmax

➢Lack of standard models for pumped hydro storage plants

Challenges and Issues• Not all hydro models have “Head Parameter” as input variable. Among the hydro models

available, only H6EU1 and HYG3U1 have head available as input parameter.

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WSHYGP WSHYDD PIDGOV IEEEG3 HYGOVR1 HYGOV H6EU1 HYG3U1

Number of different Hydro Governor Models in WECC Database

Schematic Diagram of IEEEG3

Schematic Diagram of HYGOV

Nominal Head Fixed at 1

Head can be specified

Part of Schematic Diagram of HYG3U1

Head parameter cannot be specified

Simulation based analysis of hydropower modelling gaps• Switched analysis from WECC operational model to

“MiniWECC” model to see responses of various hydrogovernor models under head variation.

• Replaced the steam turbine governors “TGOV1” model in Northwest U.S. and British Columbia, Canada with hydrogovernor models “HYG3U1”. (highlighted in green)

• HYG3U1 model allows variation of nominal head parameter “H0”

• Simulation performed with variation of “H0” while keeping other parameters/variables unchanged.

Schematic of Hydro governor “HYG3U1”

“MiniWECC” Model

Some Observations from Dynamic Simulations..

• Simulation results show that the combined change in mechanical power output of hydro generators decreases as the nominal head parameter is lowered.

• This impacts the frequency response of the system. Frequency response of the system worsened as the nominal head parameter of the hydro governor is lowered.

Variation of nominal head parameter

Some Observations from Dynamic Simulations..

• The ability of existing hydrogovernor models to limit their power output at rated capacity was tested by running a loss of generator contingency scenario when hydrogenerators are operating in their rated capacity.

• Results show that the mechanical power output of hydrogovernor can exceed their rated capacity, thus resulting the frequency response of the system to be more optimistic.

Mechanical power output of turbine exceeding rated capacity

Some Observations from Dynamic Simulations..Impact of variation of Turbine Gain Parameter• The turbine gate parameter is defined by:

▪ At = 1/(gFL-gNL), where, gFL = full load gate opening (p.u.) (0<gFL≤1), gNL = no load gate opening (p.u.) (0<gNL≤1)

• As head varies, the gate opening of the hydrogovernor turbine system varies.

• Initial results show that changes in turbine gain affects the mechanical power output response of hydro governors, thus impacting the overall frequency response.

Conclusion/Findings so far..• Majority of the models currently used in PSSE and PSLF do not allow user to change nominal head

parameters.

• Even though some models allow nominal head to be changed, the interdependencies of other turbine governor parameters on head value is not captured well by the models.

• Interaction and interdependencies of various model parameters needs to be established.

• Dynamic model doesn’t necessarily respect the maximum limitation set by governor or machine rating resulting in optimistic estimation of governor response.

Steps ahead..

• Have more extensive discussion and get feedback from model developers and industry experts on hydro generator modelling and simulation.

• Perform more simulation studies to refine understanding of the limitations of the existing hydro governor models.

FEEDBACK & DISCUSSION