asynchronous startup of a salient pole synchronous generator · a view on operas conductors (and...

A View on Operas Conductors (and other Features)

Asynchronous Startup of a Salient Pole Synchronous Generator

VF EUGM 2015, Dr. G. Maier

Pumped Storage plants – topologies

Impact of Asynchronous Startup on machine design

FE Model Features

FE Model Symmetry

Circuits

Controlling via motion.comi

Further features to include in circuits

Results

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Contents

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Pumped Storage - Topologies

MG

P

MG Motor – Generator

C Clutch

HC Hydraulic converter

T Turbine

P Pump

PT Pump-Turbine

ST Starting turbine

FC Frequency converter

PM Pony motor

CL Current limiter

T

HC

MG

ST

PT

MG

PT

FC

One question is: How to bring up the pump to synchronous speed

Only a few illustrational examples shown. No claim of completeness.

MG

PT

Asyn

Sta

rtu

p

MG

P

T

C

ST

… by hydraulic means … by electrical means

MG

PT

PM CL

Shown arrangements differ by

Operational flexibility

power change rate / switch over time (approx. 40 … 700s)

Necessity of pump dewatering

Necessity of standstill between turbine and pump operation

Controllability of pump power

Complexity of the plant

Number of hydraulic & electric machines and their necessary rating

Power electronics involved

Waterway

Arrangement, size & complexity of surge tanks

Shaft length

Building volume / excavation volume

Cost

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Pumped Storage – Topologies II

Examples for pumped storage

with asynchronous startup:

La Rance (Tidal, France)

Lower Olt (Romania)

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Interesting. But what does

this have to do with Opera?

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Asynchronous startup can yield

a rather simple arrangement, but possesses an

untypical loading of a salient pole machines damper.

E/M engineers will have to do FE.

Interesting. But what does

this have to do with Opera?

Asynchronous startup – especially under mechanic load – causes a high load for the

damper winding

Typical items of interest (for the electric engineer)

Startup time

Damper bar currents

Damper bar temperatures (considering skin effect)

Grid disturbances (flicker, voltage dip)

Further on for the mechanical engineer

Thermally induced stresses and

Deformations in all parts of the damper system

Today, FE is the typically chosen tool

Time to calculate: 10 … (60s) … 120s depending on topology and conditions Therefore there’s a strong need to keep it 2D.

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Impact of Asynchronous Startup on machine design

Possible „screws“ to achieve the

desired performance are e.g. stator

winding, pole shoe contour, damper

slot geometry, damper materials,

damper bar distribution on the pole

shoe,…

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FE Model Features

Stator laminations

Pole body

Field winding

(filamentary or eddy current)

Pole shoe Stator bars (filamentary)

Damper winding (eddy current)

Opera circuits including external

elements for:

Stator winding (connected to grid)

Field winding

Damper winding

Long “time to solve” needs a fast and efficient model.

To limit the necessary number of poles in the FE model, substituting a fractional

slot stator winding by a integer slot one can be considered.

It has to be noted, that effects connected to the stator winding scheme (e.g. pull up torques)

will appear differently in the model than in reality. If these are of interest, a model using the

exact representation of the stator winding has to be used.

For integer slot stator windings one pole in

the FE model is sufficient, although the

circuit connections across the (negative)

symmetry boundary have to be set up with

special care.

Verification especially of the damper circuits

against a model comprising 2 poles is

recommended.

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FE Model Symmetry

0

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Damper Circuits

1 2 3 4 5 6 6

Opera conductors

Portion of the bars

outside the 2D model

Circuits as entered in

Opera

Negative

symmetry

connection

Elements representing

the bar to bar

connections of both

sides

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Damper Circuits

1 2 3 4 5 6 6

Opera conductors

Portion of the bars



Opera

Negative

symmetry

connection


the bar to bar

connections of both

sides

Short circuit of one conductor

But: The short circuit of bar 1 cannot be observed in the results.

All bars show reasonable current amplitudes

Phase shift between bar currents is as expected

Open circuit bar voltages (ring with very high resistivity) show a similar image. No bar stands

out of the crowd, phase shifts as expected.

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Damper Circuits II

What‘s wrong?!

0 0

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Damper Circuits III

1 2 3 4 5 6 6

Opera conductors

Portion of the bars



Opera

Negative

symmetry

connection


the bar to bar

connections of one

side

This schematic does not have one bar shorted.

Calculated results can be explained

But: The schematic is different to the one

entered in Operas circuits!

Be careful when translating Operas circuits into schematics


the bar to bar

connections of one

side

For analyzing synchronous salient pole machines we use a home „grown“ pre- and post

processor for

Building the model

Setting up & controlling the analysis

Post processing & setting up the next simulation

Evaluating the results & report generation

For easiest integration of some „special features“ of the built up asynchronous startup

models in the above environment, it would have been beneficial to have some basic result

evaluations available right at the end of the simulation.

Motion.comi is a comi getting called at every time step

Intended for calculating #accel for mechanically coupled models (e.g. motor – shaft – load)

During my studies it turned out to be a bit like a (of course full of )

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Motion.comi

COOL!

?

Motion.comi behaviour the user might not expect

Gets called several times before the solver calculates timestep 1

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Motion.comi II

...

Unlabelled and Default Drives will use:

DEFAULT: DC drive

Running command file

motion.comi called

Value of ttime: 0.0

motion.comi called

Value of ttime: 0.0

Warning: Variable #ACCEL has not been defined in the comi file. Using value from simple coupling.

Warning: Variable #ACCEL2 has not been defined in the comi file. Using zero.

Number of nodes = 11033, number of elements= 8314

Number of fixed Potential nodes = 28

Checking Circuit data:

No errors found.

CIRCUIT DATA USED FOR THIS SOLUTION

Circuit 1:...

Motion.comi:

$displayline 'motion.comi called‘

$displayline 'Value of ttime: %REAL(ttime)'

...

Called at the very beginning of the run (when the

model / circuit data is set up)

Section f

rom

.re

s file

Might get called multiple times during one timestep

Can get called with ttime not monotonic ascending (e.g. adaptive timestepping)

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Motion.comi III

...

Converged in 1 iterations to 5.0E-05 (Mu change=2.33882E-16)

motion.comi called

Value of ttime: 7.08339E-03

motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called


motion.comi called



Motion.comi:



...

Section f

rom

.re

s file

Loops might show unexpected behaviour

Variables can get reset

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Motion.comi IV

...

motion.comi called


Opening file for reading: test.txt

25 items read from file

Value of #p_ber: 0.0

Value of #Rt #Rid4: 4.1667E-04 4.349108E-07

...

Value of #Rt #Rid4: 8.3334E-03 2.582376E-05


Command file error 150 at line 47.

$ end while

BreakError: control exited a loop

File closed


...

motion.comi called



...

motion.comi called


Opening file for reading: test.txt

25 items read from file


Value of #Rt #Rid4: 4.1667E-04 4.349108E-07

File closed


...

Motion.comi:



...

$if ((#tmax-0)*#dt+#t0-ttime)<=1E-6

$if #p_berechnet EQ 0

$ open 8 test.txt read

$ read 8 -print

$cons #loop 1

$ errorhandler no

$while #loop

$displayline 'Value of #p_ber: %REAL(#p_berechnet)'

$ read 8 #Rt #Rid4 ... -print

$ breakerror

$displayline 'Value of #Rt #Rid4: %REAL(#Rt) %REAL(#Rid4)'

$ end while

$ errorhandler yes

/

$ close 8

$displayline 'File closed'

$cons #p_berechnet 1

$displayline 'Value of #p_ber: %REAL(#p_berechnet)'

$end if

$end if

Loop reading the file gets executed only once! (only first line; no breakerror)

P_berechnet got reset! (permitting execution of the rest)

Section f

rom

.re

s file

When using motion.comi for anything „off label“ (for the „on label“ use see the

2D reference)

Use $displayline command in motion.comi for validation of correct execution + debugging

(especially loops + if-clauses)

Study the .res file carefully

Do not use code, that relies on monotonic ascending ttime or a defined call sequence of the

motion.comi

Judge results critically and carefully

In this case, simulations finally had to be done +/- completely outside of our

processing environment. New comi file for controlling simulation setup,

postprocessing, result evaluation + restarts. Motion.comi used only to a very

minor extent.

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Motion comi – (my) conclusion

Saturable reactors change their value typically depending on the current.

Opera permits functional inductances and capacitances in circuits.

Different from resistors, the actual value used is only updated at restarts (NOT every timestep / substep)

Further on, trying to find, what value has actually been used ( debugging), yields different results, depending on where you look.

„Edit circuit“ shows the name of the function

„List circuit“ shows a value (in henry), but this is updated according to the function

Consulting the “CIRCUIT DATA” section of the .res file seems most reliable.

The saturation characteristic to be used for the reactor needs to take into account the way the inductance value will be computed (e.g using peak current data or using rms current data); Nevertheless, it will be a +/- severe (depending on the application) simplification.

A more accurate possibility would be the inclusion via functional drives, although at the price of a higher complexity ( debugging)

$para #u +/-L(#some_current) * some_didt

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Further features – saturable reactors in circuits

check the sign;

equation to use has to follow the circuit topology

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Results

(Simple) Thermal model in the control routine

Functional conductivity of the damper bars

Taking the temperature calculated at the end of the previous run

Changing skin effect with changing conductivity considered

Especially interesting for materials with (comparatively) high TC

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Any Questions?

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