KHIAT Mounir, BENAAMA Kamel, KELKOUL IlyesLaboratory SCAMRE, ENPO-MA , Oran, Algeria

Khiat2_2000@yahoo.fr

Modeling and Real Time Simulation of Wind Power Systems Using Rt-Lab

Platform

1- Introduction

2- Real-Time Simulation

3- RT-LAB Platform In SCAMRE Laboratory

4- Modeling and Real Time Simulation of Wind Power Systems

5- Results and Discussion

6- Conclusion

Plan of presentation

1- Introduction

In response to the increasing demands of electrical systems for performance,reliability and cost, The control and protection equipments has becomeincreasingly sophisticated.

It is essential to validate these equipment before they are installed on the realpower system.

To accelerate the development and validation cycle of these equipments, toreduce costs and risks, the current trend is to test these equipments with areal-time digital simulator.

2- Real-Time Simulation

The objective of the real - time simulator is to test the differentelectrical equipments in the most natural possible conditions: asif they were connected to the real physical systems associatedwith them.

Therefore, the real-time simulator must reproduce as closely aspossible the dynamic behavior of the electrical system undercontrol.

The real-time simulation of the electrical system to becontrolled passes first through:

1- A modeling phase that consists in the putting of equation ofthe system.

2-Then a phase of conception of an algorithmic specification(choice of sampling period, discretization andquantification)

3- And finally, a phase of real - time implantation.

Among the real-time digital simulators used in the world, are:

RT-LAB of OPAL-RT Technologies (CANADA).

ARENE URT (EDF R&D, France).

RTDS (RTDS Inc.,Manitoba/Canada).

NETOMAC (SIEMENS, Allemagne).

Etc.

3- RT-LAB Platform In SCAMRE Laboratory

The real-time simulator used in our SCAMRE laboratory is the RT-LAB digital simulatordeveloped by OPAL-RT Technologies (Montreal, Canada).

RT-LAB Platform in SCAMRE Laboratory

AC / DC / AC converter (Triphase), 17 KW, connected to the real-time simulator.

3.1 Hardware Architecture

The hardware architecture installed within our laboratory SCAMRE, it iscomposed of two connected simulators, the Wanda 4u and the OP 5600 . Thetarget is equipped with two CPU processers (Intel Xenon six-core, 3.33 GHZ,12 M, 6.4 GT/s), including 2 cores enabled and 16 I/O, for Wanda and twoCPU processers (Intel Xenon six-core, 3.46 GHZ, 12 M, 6.4 GT/s) including 2cores enabled and 16 I/O, for OP5600

The target is responsible for the execution of models. Development, edit,verification, and compilation of models are all done on the host computer;moreover, it works as a console or command station in charge of control andobservation during simulation. Ethernet is used to communicate between hostsand targets. Communication among nodes is used by shared-memoryarchitecture. The host computer is a general PC.

System Hardware Overview for op5600 and Wanda 4u System Connection Overview

3.2. Software Architecture

The figure represents the software architecture on the host. All the studied models aredeveloped under the Matlab/Simulink environment. RT-LAB is a real-time GUI platform

and it is designed to make the real-time simulation of the Simulink models on the

clusters. RT-LAB builds parallel tasks from the original Simulink models and run them

on each core of the multi-core CPU computer or on the separate computers.

RT-LAB

(Real Time Simulation GUI platform)

MATLAB / SIMPOWER

(Model Development Environment)

eMEGASim With Artemis

(Fixed-Step Solvers For Real Time

Simulation)

Software Architecture

In the RT-LAB simulation platform, a solver named Artemis which is designed

specifically for power system can improve the simulation speed greatly, and the multi-

processor operating mode makes it available to do real-time simulations on RT-LAB

platform by separating a complex system to some simple subsystems and do parallel

operations in multiprocessor.

RT-LAB can also connect physical devices to the simulation system to make the

simulation closer to the reality and to get more convincing results.

4- Modeling and Real Time Simulation of Wind Power Systems

4.1 Wind turbine system configurationThe dominant technology for utility-scale applications is the horizontal axis windturbine. Typical ratings range from 500 kW to 5 MW. It must be noted that the poweroutput is inherently fluctuating and non-dispatchable. A typical wind turbineconsists of the following subsystems:-Rotor (consists of blades and hub);- Drive-train (shafts, gearbox, couplings, mechanical brake, and electrical generator) ;- Nacelle and main-frame (housing, bedplate, and yaw system);- Tower and foundation;- Electrical system (cables, switchgear, transformers, and power electronicconverters if present).

Modern wind turbine diagram

This presentation, describes the detailed modeling and simulation of a wind

farm based on Doubly-Fed Induction Generators (DFIG), integrated in to

the power grid.

The main advantage of the DFIG is the possibility of operating at variable

speed, For it, the system of DFIG adjusts the speed of the rotor depending on

the wind speed.

Indeed, the DFIG allows to run in hyposynchronous and hypersynchronous

generator. Thus we arrive to extract maximum possible power.

The interest of the variable speed for a wind turbine is to be able to run over a

wide range of wind speeds and to get the maximum power possible for each

wind speed.

The DFIG configuration in which the voltage on the stator is applied from the

grid and the voltage on the rotor is induced by the rotor-side converter. The

frequency difference between the mechanical frequency (rotor side) and the

electrical frequency (stator side) is compensated through a converter that

injects a variable frequency rotor current both in normal and fault condition

operation.

4.2 DFIG Model

Today, 80% of new aerogenerators contain Doubly Fed Asynchronous (with rotorcoil).

One characteristic of the DFIG-based wind turbine system is the bidirectionalpower flow of the rotor. When ωr >ωs the power flows from the rotor to the powernetwork. When ωr

4.3 Implementation

The model of the power system used in this study, is Composed of a 12 DFIG

connected to a system of transmission to high voltage 220KV with 19 buses,

power stations of generation (synchronous machines and regulators), and 11

loads. The nominal operating frequency of the network is 50 Hz.

B19

SM 3

L4L5

L1

L24

L22

L28L27 L26

B6

B5

B4

B2B3

Idealsource

B15

B16 B14

B11

B17

B7

B12 B13

B8

B9

B10

B1L25

L19

L31 L32

L30

L20 L21 L23

L13 L14

L15 L16

L17 L18

L2

L6 L3

L7 L8

L9 L10

L11

L12

SM 1

SM 2

SM 4

SM 5

L29

B18

Wind Farm (12 DFIG) UnitsGrid

Single-line diagram of the power system under investigation

4.3.1 Model description

The transmission grid is divided into two subsystems namely

"SS_NETWORK_A" and "SS_NETWORK_B". SS NETWORK_A consists of

the swing bus, buses (07) to (17), seven loads and three power stations of

generation. Buses (1) to (6) and buses (18) and (19) are located in

SS_NETWORK_B which contains also two power stations of generation. This

subsystem also consists of four loads and a tie in to the wind farm. The regulation

and control of generators are placed in SM _Control subsystem. Thewind farm

subsystem is designated by SS_Wind Farm and it is connected to the transmission

system.

The WANDA and OP5600 digital simulators are limited by the number of

processors enabled on the simulation target. In the case of this study, the

maximum number of active processors (CPU) licensed was four, hence the power

system could be broken into a maximum four subsystems, as shown in Figure .

The first CPU takes in charge the synchronous generators and their regulator

simulation. The 19 buses are distributed on CPU 2 and CPU 3 as shown in figures

15 and 16, respectively; the last CPU is reserved to the simulation of twelve

DFIGs with their controls.

Model Implementation of Park Aerogenerators Integrated Network.

Length: 75km

Length: 75km

Length: 75km

Length: 75km

Discrete,Ts = 5e-005 s.

powergui

control-WF

result-WF

A1

B1

C1

A2

B2

C2

A3

B3

C3

A4

B4

C4

SS_Wind_Farm

Cotrol-Bresult-B

A5

B5

C5

A6

B6

C6

A7

B7

C7

A8

B8

C8

B6a1

B6b1

B6c1

B6a2

B6b2

B6c2

SS_Network_B

control-A

result-A

B7a1

B7b1

B7c1

B7a2

B7b2

B7c2

SS_Network_A

fault

result-A

result-B

result-WF

result

control-A

control-B

SM_Control

resultcontrol-WF

fault

SC_Scoop

DPL

Length:75km

DPL

Length: 75km

DPL

DPL

DPL

DPL

ARTEMiS GuideTs=50 usSSN: OFF

5 Results and discussion

The system is running at the real time step of 50 μs. The parameters of the DFIG based wind

turbine are shown in next table. As can be seen from next figure 18, the adopt wind profile variesbetween 8m/s and 12m/s for turbines in Wind-Farm subsystem.

0 10 20 300

5

10

Time [s]

speed [

m/s

]

Wind speed profile.

Parameter Value

Nominal power 1 MVA

Gear ratio 80.27

Line to line voltage 400 V

Frequency 50 HZ

DC-bus voltage 1250 V

Pole pairs 1

Stator resistant 0.0256294 pu

Rotor resistant 0.0100649 pu

Stator inductor 0.0998644 pu

Rotor inductor 9.62367 pu

Mutual inductance 3.47857 pu

Generator inertia 0.62 kg m2

Filter inductor 0.001 H

DC-bus capacitor 0.025 F

Kp and Ki for Pitch control PI 150 , 50

Kp and Ki for Pitch compensation PI 3 , 4

Kp and Ki for torque control PI 3 , 0.6

Kp and Ki for RSC (current regulation) 1.896 , 60.9162

Kp and Ki for RSC (voltage regulation) 0.87946 , 60.905

Kp and Ki for GSC (current regulation) 4.158 , 500

Kp and Ki for GSC (DC regulation) 1.25 , 200

Wind turbine (DFIG) parameters

5.1 Wind turbine performanceSince the wind turbines are similar and present the same behavior, it is enough topresent the performance of the first wind turbine.

Figure 1 and Figure 2 show the behavior of the three-phase currents and voltagesgenerated by each DFIG. It is clear that the voltages and currents are perfectly stable andsinusoidal during steady-state operation.

Figure 3 shows the active and reactive powers generated by the wind turbine. Thesepowers are controlled by the rotor side converter (RSC).

Figure 4 shows the DC bus voltage, thanks to the grid side converter control (GSC) theDC bus is almost a constant value, in which the DC voltage can be maintained at 1250V.A stable voltage at the DC bus could help the GSC to control the active and reactivepowers.

The turbine and electromagnetic torques of the DFIG, as shown in Figures 5 and 6,respectively are following the wind speed profile in the aim to extract the maximumpower. The sign of torques is as function of the slip sign. When the slip is negative(over-synchronism) the electromagnetic and mechanical torque are negative obviouslyin steady-state.

0 5 10 15 20 25 30-400

-200

0

200

400

600

800

Time [s]

U [

V]

U1

U2

U3 10 10.01 10.02

-500

0

500

0 5 10 15 20 25 30

-0.2

0

0.2

0.4

0.6

Time [s]

I [A

]

Ia

Ib

Ic

×104

0 5 10 15 20 25 30

-0.4

-0.2

0

0.2

0.4

0.6

Time [s]

P[M

W],

Q[M

VA

r]

P Q

1- Wind generator voltage power 2-Wind generator currents 3- Wind generator active and

reactive

10 10.01 10.02-0.4-0.2

00.2

×104

0 0.51245

1250

0 5 10 15 20 25 300

500

1000

1500

Time [s]

Udc [

V]

0 0.51245

1250

0 5 10 15 20 25 30

-0.25

-0.2

-0.15

-0.1

-0.05

0

Time [s]

Tm

[kN

.m]

0 5 10 15 20 25 30-0.4

-0.3

-0.2

-0.1

0

0.1

Time [s]

Te [

kN

.m]

4- DC-bus voltage 5-Turbine torque 6- Electromagnetic torque.

5.2 Wind farm and grid performances

In this part, the simulation results obtained at bus 6 are presented. The bus 6 is chosen asmeasurement bus because it is connected to the transformer that joints the wind farm to thepower grid. At that bus, the three-phase voltages and currents are shown in figures 6 and 7,respectively.

It is can be seen that the waveforms are perfectly stable, and take sinusoidal shapes atsteady-state.

The voltage takes the value of 200 kV after being increased by the transformer connected atbus 18 where the voltage was 25 kV.

Figure 8 presents the active and reactive powers measured at bus 6. It is interesting tonotice that the active and reactive powers are totally decoupled.

The active power takes a value about -102 MW produced by the machine SM1 and windfarm, taking into account the loads consumption.

0 5 10 15 20 25 30-2

0

2

4x 10

5

Time [s]

U [

V]

U

a

Ub

Uc 10 10.01 10.02

-2

0

2x 10

5

0 5 10 15 20 25 30

-400

-200

0

200

400

600

800

Time [s]

I [A

]

Ia

Ib

Ic

10 10.01 10.02-500

0

500

0 5 10 15 20 25 30-15

-10

-5

0x 10

7

Time [s]

P [

W],

Q [

VA

r]

P Q

0 10 20 30

-1.025

-1.02

-1.015

-1.01x 10

8

6- Bus 6 voltages. 7-Bus 6 currents. 8-Bus 6 power.

5.3 System performance under faulty conditions

In order to exhibit the behavior of the proposed power system under faulty

conditions the bus 6 is grounded at t=5s, and the applied three-phase fault lasted for

1s. The real simulations results under the bus 6 grounding are recorded at buses 1,

6, and line 5-6.

The following figures show the results obtained for buses 6,1 and line 5-6under faulty conditions.

0 5 10 15-20

-15

-10

-5

0

x 107

Time [s]

P [

W]

0 5 10 15

-2

0

2

4

6x 10

5

Time [s]

U [

V]

U

a

Ub

Uc

11 11.01 11.02-2

02

x 105

0 5 10 15

-1

-0.5

0

0.5

1

1.5x 10

4

Time [s]

I [A

]

Ia

Ib

Ic

11 11.01 11.02-500

0

500

Voltages at Bus 6. Currents at Bus 6. Active power at Bus 6.

0 5 10 15-0.5

0

0.5

1

1.5

2

2.5x 10

6

Time [s]

P [

W]

106

0.5

-0.1

0.1

0.2

0.3

0.4

5 10 15 20 25 300

200

400

600

800

1000

1200

Time [s]

U d

c

0 5 10 15

-3

-2

-1

0

1

2

x 108

Time [t]

P [

W]

0 5 10 15

-2

0

2

4

6x 10

5

Time [s]

U [

V]

Ua

Ua

Ua 11 11.01 11.02

-2

0

2x 10

5

0 5 10 15

-1500

-1000

-500

0

500

1000

1500

2000

Time [s]

I [A

]

Ia

Ib

Ic 11 11.01 11.02

-200

0

200

0 5 10 15-4

-3

-2

-1

0

1

2x 10

8

Time [s]

P [

W]

5 5.5 6

-4

-2

0x 10

7

Voltages at Bus1 Currents at Bus1 Active power at Bus1.

Wind generator active power. DC-bus voltage Active power at line5-6.

5 6 71100

1200

1300

6. Conclusion

In this presentation, a detailed wind farm model based on DFIG connected to alarge power system is designed and simulated using eMEGASim, real-time digitalsimulator, In order to allow for a higher level of wind turbines integration inelectric grid without affecting the quality of the generated electric power.

Simulation results show clearly the good performance of the overall system basedon eMEGASim, real-time. Indeed, with much less time consuming, this simulatorhas demonstrated to be an effective way to study interactions between complexnonlinear power system components as in real operating conditions.

THANK YOU