B. Silva, Senior Researcher, INESC TEC
Contribution of variable-speed pump hydro storage for power system dynamic performance
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Framework
The work presented was developed within the framework of FP7- HyperboleProject.The Hyperbole project intend to study the flexibility of hydro technology from
a mechanical an electrical perspective.
From the electrical perspective, variable speed pump storage powerplants
(var-speed PSP) were detailed studied.
HYPERBOLE
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Objective
• Develop a var-speed PSP reduced-order model in PSS/E to assess the impact overcoming from the progressive integration of such units in the Portuguese Power System dynamic performance
HOW?
1. Develop a PSS/E model which describes the main dynamics of frequency responsive PSP
2. Integrate the model in the Portuguese Power system PSS/E model
3. Play major disturbances leading to generation/load mismatch frequency deviation
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Development of frequency-responsive PSP model
• Based on the research developed within the Hyperbole Project, a PSP was to be developed in PSS/E in order to be further integrated with Portuguese grid Model;
• Initial approach:
• Graphical Model Builder (GMB) PSS/E toolbox
Several difficulties regarding severe limitations disabling its adoption;
• Alternative approach:
• Design a frequency responsive power injector associated with PSP control schemes, representing its main dynamics.
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Development of frequency-responsive PSP model
Key assumptions:• Generators are electronically interfaced (focus on deriving a model representing the
operation of a full size frequency converter - FSFC);
• Generators (FSFC) are represented by a controllable load (approach adopted for modelling electronic interface units such as Wind and PV farms);
• The load model (power injector) reacts to grid disturbances by setting an active power variation proportionally to the frequency deviation Fortran user-written model
• Pinj<0 Pump mode;• Pinj>0 Turbine mode;
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Integrate the model in the Portuguese Power system PSS/E model
• REN provided representative grid scenarios Valley hours was adopted to take advantage of having PSP operating in pump mode.
• Spanish-grid side was not represented due to confidentiality aspects dynamic equivalents were developed and included in each PT-ES interconnection.
• The aforementioned grid was considered to be the “BASE CASE” scenario;
• Progressive integration of frequency-responsive variable-speed PSP model in the study case;
• Python script to monitor the amount of non-Fault ride-through compliant WF.
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Scenario #1: Fault at Lavos substation
Variable-speed Units
CASE A None BASE CASE
CASE B Venda Nova III 1 x 360 MW
CASE CVenda Nova III 1 x 360 MW
Aguieira 3 x 91 MW
CASE D
Venda Nova III 1 x 360 MW
Aguieira 3 x 91 MW
Alqueva 4 x 110 MW
Venda Nova II
Aguieira
Alqueva
Disturbance: • 3-phase short-circuit at Lavos 400 kV busbar• The disturbance led to the sudden
disconnection of 1130 MW of non-Fault Ride-Through compliant wind farms
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Results – Fault at Lavos Busbar
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Results – Fault at Lavos Busbar
• Variable-speed PSP are able to respond by providing active power support (reduction of absorbed power) and thus helping the system frequency support;
• The presence of variable-speed PSP helps on damping resulting oscillations.
• The increase of frequency-responsive variable-speed PSP helps on the achievement of faster frequency recovery and reduction on the minimum frequency excursion, enhancing the power system dynamic performance.
• The observed Active power oscillations for the cases where var-speed PSP are set to respond to primary frequency control are related with voltage oscillations and the modelling of electronic units as constant admittance.
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Scenario #1: Generation trip at Pêgo powerplant
Variable-speed Units
CASE A None BASE CASE
CASE B Venda Nova III 1 x 360 MW
CASE CVenda Nova III 1 x 360 MW
Aguieira 3 x 91 MW
CASE D
Venda Nova III 1 x 360 MW
Aguieira 3 x 91 MW
Alqueva 4 x 110 MW
Venda Nova II
Aguieira
Alqueva
Disturbance:
Sudden disconnection of Pêgo thermal powerplantthat was generating 220 MW
Pêgo thermal powerplant
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Results – Generation trip at Pêgo thermal Powerplant
• Hydro pumping units are able to respond by providing active power (absorption reduction) and thus helping the system frequency support;
• The presence of variable-speed units helps on damping aftermath oscillations.
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Results – Generation trip at Pêgo thermal Powerplant
A slight power increase can beobserved for the base casefollowing the disturbance since itis related with the powercalculation methods that aredependent of voltage variations.
The variable-speed PSP is able to respond by decreasing the active power absorbed
Venda Nova III- Trip of Pêgo powerplant
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Main Conclusions
• A reduced order model has been developed and tested in PSS/E;
• The model allowed to assess the impact of having frequency responsive var-speed hydro pumping units in the Portuguese power system modelled in PSS/E;
• The results showed that the var-speed PSP can play an important role on providing primary frequency support in scenarios of large-scale renewable integration where reduced amount of synchronous generation units are connected to the system
• This model can be used by TSO for assessing the impact of variable-speed frequency-responsive PSP in power systems planning and operational perspectives;
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Thank [email protected]