Marc Langevin, eng., Ph.D.

Marc Soullière, tech.

Jean Bélanger, eng.

*

A Real-Time Regulator, Turbine and Alternator Test Bench for Ensuring Generators Under Test Contribute

to Whole System Stability

AC Generator in Operation

Synchronous Operation; Operation in Islanded System; In both modes of operation,

Speed/Frequency control is required.

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AC Generator in Operation in Both Modes

To maintain balance and stability, mechanical power must equal electric load;

After a disturbance, system frequency should reset to its set point value as fast as possible;

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Frequency behavior of an AC generator in an islanded mode of operation

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Frequency Behavior in a Multi-Machine System

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Important Principles

Two Important Principles to Consider when Adjusting a Speed Governor:

Speed governor must be set to ensure operating stability in an islanded power system;

Speed governor must avoid contributing to natural electro-mechanical power oscillations;

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Synchronized Generator

The synchronous interconnection transfers the stabilizing energy from the stable units to the unstable units;

But does not stabilize a power system where most of the units would be unstable in an islanded system;

Conclusion: every unit should be set to be stable in islanded operation mode. That’s the speed governor job.

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P.S.S. Interference

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Real-Time Islanded Mode Simulator

MAKE THE ACTUAL GENERATOR BEHAVE AS IF OPERATING IN ISLANDED MODE WHILE REMAINING SYNCHRONIZED WITH THE MAIN GRID;

And set the speed governor accordingly

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Modern PID Speed Governor

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Servomotors Chain

Permanent Droop

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Hydraulic Turbine Non-Linear Model

.

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Water Flow

Net Head

Head Losses

Water Starting Time

Many Uncertainties

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Effective Opening

Efficiency

Gross Head

Test Bench Setup for Actual Test in Powerhouse

.

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RT-LAB BERTA TEST BENCH

SPEED GOVERNOR TURBINE GENERATOR

IFAC 2009 – Tampere, Finland

MECHANICAL SWITCH

Islanded System vs Test Bench Real-Time Simulator. Stable Case

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Islanded System vs Test Bench Real-Time Simulator. Unstable Case

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P.S.S. Simulation Function

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On-site Testing in Hydro-Québec Powerhouse.

Two different sets of PID gains. Frequency variation

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On-site Testing in Hydro-Québec Powerhouse

Two different sets of PID gains. Gate servomotors variation

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On-site Testing in Hydro-Québec Powerhouse

Two different sets of settings. Mechanical Power Variation

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On-Site Testing VS Classical Modelling

What if your classical model is wrong? See next slide;

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Reality vs. Classical Model Simulation

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Reality vs. Classical Model Simulation

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.

H-Q grid actual frequency

Simulator Generated Frequency

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Islanded Operation Simulation Unstable Case

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Islanded Operation Simulation Stable Case

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On-site Testing. Boxes and Real-Time Station

RT-LAB BERTA’s real-time computer, junction and switching boxes and flat screen during on-site testing by Hydro-Québec powerhouse, November 2008

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On-site Testing. Real-Time Station Rear View

Rear view of the RT-LAB BERTA real-time computer showing the I/O connection with the speed governor during on-site testing by Hydro-Québec powerhouse, November 2008

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Conclusions & Benefits

Until now, it has been almost impossible to assess with a high degree of accuracy the behavior of a synchronous generator in an islanded power system. Characterizing such behavior is indispensable to properly set a speed governor.

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Conclusions & Benefits

To date, model and parameter identification tests have been very expensive and don’t provide an accurate and robust model of a turbine. The process is time-consuming and arduous as described by the following steps that must be performed for each machine:

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Conclusions & Benefits

The process is time-consuming and arduous as described by the following steps that must be performed for each machine:

Preliminary settings based on specifications provided by the manufacturers of the turbine and generator;

Model and parameter identification tests in the power station;

Off-line stability studies to recommend the appropriate settings, based on the models and parameters as determined by tests carried out at the power station;

Return to the power station to implement new appropriate settings on the speed governor

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Conclusions & Benefits

The proposed Test Bench allows these operations to be carried out in a single test run at the power station with the following benefits:

Accuracy of speed governor control settings ensuring that each machine has a stabilizing effect on the power system;

Validation of PSS low frequency settings ensuring that the PSS and the speed governor do not react against each other;

Accuracy of speed governor and turbine models; Stability and reduction of demand on servomotors by

applying appropriate settings; Productivity gain for model identification and control setting; Shorter tests in the power station due to ease of use of

Test Bench.

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Thank You

Questions?

Join us for a Demonstration at the Opal-RT Booth located near the Conference Coffee Break Area

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