Post on 16-Sep-2018
Studies on low inertia systems and application of synchronous condensersFrom Danish project SCAPP
Guangya Yang
Center for Electric Power and EnergyDepartment of Electrical EngineeringTechnical University of Denmark
2 DTU Electrical Engineering, Technical University of Denmark
Current system operation• Rotational mass from synchronous machines acting as the inertia of the system
for frequency regulation– Stabilize small imbalances in power generation and consumption;– In quasi-static operation the speed of the machine is a global measure of power balance;– Provide inertia to the system when subject to large power imbalances due to e.g. short circuit, which
limits the rate of change of frequency;
• Also acting as a strong voltage source– High short circuit power level that stabilizes the voltage fluctuations due to variation of loads and retain
power quality;– Overload capacity during faults that supplies short circuit current to the fault locations that retains the
reliability of the protection system operations.– Stiff grid enhances the commutation of HVDCs and connectivity of resources of different properties
such as power electronic devices, e.g. renewables, battery storage;
3 DTU Electrical Engineering, Technical University of Denmark
Converters vs synchronous machines• Converters are power electronics that have different nature as synchronous
machines– No rotational mass that supports frequency;– Significantly reduced short circuit current supply capability during severe voltage dips due to
limited overload capability of IGBTs;– Flexible in operation yet the response is dependent on the control systems;
• Response speed of the control system can differ due to different control parametersused;
• Different control strategies yield different outputs during faulty situations especially;– Lack of grid code that specifies the characteristics of the control to the extent that can be
useful for all operational situations;– Various grid connection conditions may yield control problems;– Testing methods are still under development for high power equipment;
4 DTU Electrical Engineering, Technical University of Denmark
A condenser
5 DTU Electrical Engineering, Technical University of Denmark
Future energy system
Inverter based generation
Inertia response
Frequency control
Short circuit power
Phase out synchronous generators
AC/DC mixed network
Volt/Var support
SCAPP OverviewSynchronous condensers may be a critical component for the transition.
The project will look at the following issues with a focus on the application of synchronous condensers (SC)
System frequency and inertia characterisation;
Short-circuit power and performance key protection relays;
Hardware-in-the-loop testing for validation;
Optimal properties of SC;
Use of RTDS at PowerlabDK; Intensive R&D project; Close DTU-Siemens collaboration;
6 DTU Electrical Engineering, Technical University of Denmark
Synchronous condensers in DK
Station Area kV Mvar YearBjæverskov DK2 400 270 2013Herslev DK2 400 200 2014Fraugde DK1 400 200 2014
• 7 synchronous condensers in DK • 3 recent synchronous condensers• Short circuit power
– BJS(2013) >800 MVA;– FGD/HKS (2014) > 1000 MVA;
• Reactive power compensation– -150/215 Mvar (BJS)– -120/180 Mvar (FGD/HKS)
• Installed at HVDC converter stations
7 DTU Electrical Engineering, Technical University of Denmark
Frequency and Inertia response
DK1 system
~
~
~
TJE
GER
NJVB2,3
NVV
~
Sweden
VHA
TRI
MKS SSVB3,4
~
~
~
ENVB3
EDR
ESVB3
FVO
~
FYVB7
FGDLAG
SHE
SVS
VKE
REV
KAS
~
~
~
FER
SKVB3
AHA
22/0.69 kV
8 DTU Electrical Engineering, Technical University of Denmark
Frequency response validation
110 115 120 125 130 135 140
Time (s)
49.995
50
50.005
50.01
50.015
50.02
50.025
50.03
50.035
50.04
50.045
f(Hz)
Frequency from PMU (Energinet.dk)
f-KASX: 115.1
Y: 50.04
X: 125.2
Y: 50
0 5 10 15 20 25 30
Time (s)
49.97
49.98
49.99
50
50.01
50.02
50.03
f (H
z)
Frequency from RTDS Simulation
f-KAS
X: 13.14
Y: 49.98
X: 3.058
Y: 50.02
9 DTU Electrical Engineering, Technical University of Denmark
Short circuit current validation
10 DTU Electrical Engineering, Technical University of Denmark
Hardware in the Loop testingHardware
Simulation
RTDS (Grid and synchronous
condenser models )
Communication Interface
Synchronous condenser automatic voltage regulator and
protection system
Communication and amplification Interface
Extract signals from simulation
to physical
Control and protection
signals
11 DTU Electrical Engineering, Technical University of Denmark
Frequency study results – base case
12 DTU Electrical Engineering, Technical University of Denmark
Frequency study results - – base case
13 DTU Electrical Engineering, Technical University of Denmark
Frequency study results - HWHL
14 DTU Electrical Engineering, Technical University of Denmark
Frequency study results - HWHL
15 DTU Electrical Engineering, Technical University of Denmark
Frequency study results – Short circuit + load trip
16 DTU Electrical Engineering, Technical University of Denmark
Frequency study results – Short circuit + load trip
17 DTU Electrical Engineering, Technical University of Denmark
Converter control strategies during fault• Synchronous reference frame (SRF) vector control
– Positive sequence only with current limit;
• Flexible power control– Sequence power controlled separately – Considering both positive and negative sequence;
• both directions𝒊𝒊𝒓𝒓𝒓𝒓𝒓𝒓 = 𝒊𝒊𝒑𝒑
𝒓𝒓𝒓𝒓𝒓𝒓 + 𝒊𝒊𝒒𝒒𝒓𝒓𝒓𝒓𝒓𝒓
– Active power control
𝒊𝒊𝑝𝑝𝑟𝑟𝑟𝑟𝑟𝑟 =
𝑃𝑃𝑟𝑟𝑟𝑟𝑟𝑟
𝑽𝑽+ 2 + 𝑘𝑘𝑝𝑝 𝑽𝑽− 2 (𝑽𝑽+ + 𝑘𝑘𝑝𝑝𝑽𝑽−)
– Reactive power control
𝒊𝒊𝑞𝑞𝑟𝑟𝑟𝑟𝑟𝑟 =
𝑄𝑄𝑟𝑟𝑟𝑟𝑟𝑟
𝑽𝑽+ 2 + 𝑘𝑘𝑞𝑞 𝑽𝑽− 2 (𝑽𝑽⊥+ + 𝑘𝑘𝑞𝑞𝑽𝑽⊥−)
18 DTU Electrical Engineering, Technical University of Denmark
Control effects• Strategy 1: Constant active power control (𝒌𝒌𝒑𝒑=-1, 𝒌𝒌𝒒𝒒=1)
• Strategy 2: Balanced fault current control (𝒌𝒌𝒑𝒑=0, 𝒌𝒌𝒒𝒒=0)
• Strategy 3: Constant reactive power control (𝒌𝒌𝒑𝒑=1, 𝒌𝒌𝒒𝒒=-1)
-0.06504 -0.03333 0 0.03333 0.06667 0.1 0.13333-2
-1.33333
-0.66667
0
0.66667
1.33333
2
p.u.
IAH IBH ICH SL1
-0.06504 -0.03333 0 0.03333 0.06667 0.1 0.13333-100
16.667
133.333
250
366.667
483.333
600
MW
or M
var
P_HVDC Q_HVDC
-0.03333 0 0.03333 0.06667 0.1 0.13333-100
16.667
133.333
250
366.667
483.333
600
MW
or M
var
P_HVDC Q_HVDC
-0.03333 0 0.03333 0.06667 0.1 0.13333-2
-1.33333
-0.66667
0
0.66667
1.33333
2
p.u.
IAH IBH ICH SL1
-0.05615 -0.03333 0 0.03333 0.06667 0.1 0.13333-100
16.667
133.333
250
366.667
483.333
600
MW
or M
var
P_HVDC Q_HVDC
-0.05615 -0.03333 0 0.03333 0.06667 0.1 0.13333-2
-1.33333
-0.66667
0
0.66667
1.33333
2
p.u.
IAH IBH ICH SL1
19 DTU Electrical Engineering, Technical University of Denmark
Results - HiL• Real relay is used for test
• Relay performance is adversely affected by converters
• Generally more SC capacity, better relay performance
20 DTU Electrical Engineering, Technical University of Denmark
Short circuit power from converters• In general, all control strategies will not overcome the current limits given by the power electronic
elements. • Increasing the number of elements in the converter for higher current carrying capability will
increase the costs• Depending on the circuit parameters and the control system response time, the current phase can
differ from the ones provided by other elements;• The impact on the relays should be considered both on the current magnitude and phase;• Problems can occur either due to less fault current level, or relay cannot detect the fault;• Due to lack of requirements in general in this field (esp. unbalanced faults), there are needs for
more detailed specifications.
21 DTU Electrical Engineering, Technical University of Denmark
QUESTIONS?
Thank you for your attention!
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