modern design for variable speed motor-generators · 7 converter fed synchronous machine: p mech...
TRANSCRIPT
1 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Modern Design for Variable Speed Motor-Generators: Asynchronous and Synchronous Electric
Machinery Options for Pumped Storage
Power Plants
SHF - Enhancing Hydropower plants Grenoble, April 9-11, 2014
2 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
|Pshaft|
( nsync ) nmax nmin
• Maximum shaft
power depending
on rotational speed
• Limitation by stator
/ rotor / converter
currents, voltages
(-> field weakening
range), torque,
transformer power
Variable Speed Motor-Generators
Shaft Power over Speed
3 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
FixSpeed
• Synchronous Machine
with Salient Poles (SYM)
as Generators & Motor-
Generators
• (2 Speed -> Pole Switching
Synchronous Machine)
• Stator Fed Synchronous
Machine
• Double Fed Induction
Machine
VarSpeed
Variable Speed Motor-Generators
Overview Electric Machinery
4 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Only Visual Comparison - Not to Scale
Ro
tor
of S
yn
ch
ron
ou
s M
ach
ine
Ro
tor
of D
ou
ble
Fe
d In
du
ctio
n
Ma
ch
ine
Variable Speed Motor-Generators
Overview Electric Machinery
5 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Synchronous Machine: Rotor Pole
- Salient Poles
- DC Field Winding
- Damper Winding
- Stacked Pole Body with Solid Endplates
Induction Machine: Rotor Pole Pitch
- No Salient Poles
- 3-phase AC Winding
- No Damper Winding
- Stacked Rotor Body (Silicon Steel Laminates)
Synchronous Machine: Salient Pole Induction Machine: Pole Pitch
Variable Speed Motor-Generators
Overview Electric Machinery
6 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Synchro
nous M
achin
e
Double
Fed I
nduction M
achin
e
Variable Speed Motor-Generators
2D-FEM Calculation Magnetic Induction
7
Converter Fed Synchronous Machine:
Pmech ≈ Sstator ≈ Sstator-side conv ≈ P.F. * Sgrid-side conv ≈ P.F. * Stransformer
Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Synchronous
M-G
~
= DC-Link
Stator-Side Converter
Unit Grid-Side Converter
Unit
Block Transformer
High Voltage Grid
~
=
Full Power Converter
Pump-
Turbine
DC-Excitation
Additional transformer may
be required for retrofit or
special applications
Variable Speed Motor-Generators
Overview Electric Machinery
8
DFIM
Pump-
Turbine
AC-Excitation System Block Transformer
High Voltage Grid
~
= DC-Link
Rotor-Side
Converter Unit Grid-Side
Converter Unit
~
=
AC-Excitation
Transformer
Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Sum of stator and rotor branch: - Active Power and
- Reactive Power
- Failure Currents
- Harmonics (Voltage Waveform)
Variable Speed Motor-Generators
Overview Electric Machinery
9 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Harmonic Distortion THD of the stator voltage at 1.5 Hz rotor fundamental:
• THD < 0.8% with converter fed rotor
for comparison:
• THD < 0.5% for sinusoidal rotor voltage
Rotor (Converter) Voltage Spectrum Stator Voltage Spectrum
Rotor fed by
converter
(clocked voltage
source)
Variable Speed Motor-Generators
Example THD
10 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Double Fed Induction Machine:
• Grid code requirements ► rotor-side converter
• Power factor ► converter & rotor & stator
• Time for mode changes ► rotor & converter voltage
• Black start capability ► converter
Converter Fed Synchronous Machine:
• Bypass required ? ► motor-generator
• Moment of inertia (limiting hydraulic overpressure)
► motor-generator (number of pole pairs)
Variable Speed Motor-Generators
Major influence on components
11 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Synchronous Machine with Full
Power Converter
DF Induction Machine with AC-Excitation
System
Operation mode :
428.6rpm; 102MW;
Total 110MVA, p.f. 0.90;
Stator 101MVA, p.f. 1.0
428.6rpm; 102MW;
Total 111MVA, p.f. 0.90;
Stator 110MVA, p.f. 0.92
Friction losses 480 kW 580 kW
No-load losses 210 kW 200 kW
Stator I2R losses 210 kW 250 kW
Rotor I2R losses 110 kW 390 kW
Additional losses 160 kW 300 kW
Excit. system losses 20 kW 380 kW (incl. AC-Excitation)
Converter losses 1510 kW (≈ 98.5 %) -
Total losses / efficiency 2700 kW / 97.3 % 2100 kW / 97.9 %
(≈ 98.8 %) (≈ 98.3 %)
Variable Speed Motor-Generators
Efficiency
12 Synchronous Machine: Ventilation axial-radial
• axial air intake into the pole gaps
or radial-radial possible.
Induction Machine: Ventilation radial-radial
• air intake into the rotor hub.
SYM: Axial intake into pole gaps, or
radial-radial air-flow DFIM: Radial-radial air-flow
Variable Speed Motor-Generators
Ventilation Concept
Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
13 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Verification by CFD Analysis:
• Air-flow distribution
• Cooling air velocity
• Verification of ventilation losses
• Estimation of heat transfer
Variable Speed Motor-Generators
Ventilation Concept
14 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
• Closed air circulation
• Self ventilated sliprings plus shaft
mounted radial fan
• Filter and air-water heat
exchangers on top
• Open ventilation concept
• Self ventilated sliprings
• Combined system for heated air and
carbon dust extraction
Air intake
Manifold
Variable Speed Motor-Generators
Ventilation Concept
15 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
• Clocked voltage with high dU/dt
• Additional loading for the corona
protection system
• Capacitive current through the main
insulation (-> bearing currents)
• The standard equivalent circuits do
not represent the reaction on high
frequency events, such as voltage
peaks with high dU/dt.
R‘(f)
R‘(DC)
L‘i(f), L‘a
R‘_Fe(f)
C‘r
R‘(DC)
R‘(f)
L‘i(f), L‘a
R‘_Fe(f)
Variable Speed Motor-Generators
Challenges for the Winding System
16 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
SYM with Converter DF-IM
(+) Synchronous machine (-) DF-IM as more complex machine
(-) Converter cost for full stator power (+) Converter for rotor power only
(-) Efficiency drop due to converter losses (+) Higher efficiency
(-) Additional converter power required for
power factor regulation
(+) Separate active and reactive power
control
(+) By-pass operation possible (-) Practically converter always in operation
(+) Very flexible operation, incl. e.g. high
speed power shifts and mode changes.
(o) Flexible operation, incl. e.g. high speed
power shifts (but limited by the speed
range)
(+) Very quick startup (pump in water) (-) Startup of pump with runner in air
(+) Black-start capability (o) Additional provisions for black-start
(+) Retrofit opportunity to speed variable units (-) Complete new rotor plus converter
Variable Speed Motor-Generators
Overview Electric Machinery
17 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10
Contact:
Ludger Koedding
Tel. +49 7321 37-2915
18 Modern Design for Variable Speed Motor Generators | SHF 2014 | Ludger Koedding | 2014-04-10