University of ManitobaDepartment of Electrical & Computer Engineering

ECE 4600 Group Design Project

Progress Report

Design and Harware Implementation of a Supervisory Controller for

a Wind Power Turbine

byGroup 09

Alimujiang, Abulizijiang Gill, AjaypalPrzybytkowski, Daniel Uppal, Laraib

Academic Supervisor(s)

Annakkage, Udaya D., P.Eng

McNeill, Dean, P.Eng

Industry Supervisors

Bagen Bagen, Dr. – Manitoba Hydro

Date of Submission

January 12, 2015Copyright © 2015 Abulizijiang Alimujiang, Ajaypal Gill, Daniel Przybytkowski, Laraib

Uppal

Supervisory Controller TABLE OF CONTENTS

Table of Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Project Progress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2.1 Pitch Angle Control in Software (Ajaypal, Laraib) . . . . . . . . . . . . . . . 1

2.2 Optimum Power Control in Software (Ajaypal, Laraib) . . . . . . . . . . . . . 2

2.3 Breaker Control in Software (Ajaypal) . . . . . . . . . . . . . . . . . . . . . . 2

2.4 Fault Introduction and Duration Control in Software (Laraib) . . . . . . . . . 2

2.5 Pitch Angle Control in Hardware (Abulizijiang, Daniel) . . . . . . . . . . . . 3

2.6 Optimum Power Control in Hardware (Daniel) . . . . . . . . . . . . . . . . . 3

2.7 Fault Detection in Hardware (Abulizijiang, Daniel) . . . . . . . . . . . . . . . 4

2.8 Low Voltage Ride-Through in Hardware (Abulizijiang) . . . . . . . . . . . . . 4

3 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Appendix A Updated Gantt Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Appendix B Updated Budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Appendix C Power Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Appendix D Low Voltage Ride-Through . . . . . . . . . . . . . . . . . . . . . . . . . . 14

i

Supervisory Controller 1 Introduction

1 Introduction

In a modern wind power plant, a supervisory controller is used to control the operation of multiple

wind turbines. The objective of this project is to design a supervisory controller for a single Type-3

2MW rated wind turbine. The supervisory controller will control the power output of the wind

turbine through the regulation of rotor speed and rotor blade pitch angle as per industry practice.

Under normal conditions, the controller will monitor wind speed, and the turbine will generate

power in accordance with the typical power curve of a Type-3 wind turbine. The controller will

carry out Low Voltage Ride-Through (LVRT) under fault conditions as required by the Canadian

Grid Code for Wind Development.

At this present time, the supervisory controller simulation in RSCAD and the hardware im-

plementation are progressing as scheduled. Future work will consist of optimizing the controller

performance and analyzing the behavior of the wind power system.

2 Project Progress

The project is progressing on schedule as shown in the updated Gantt Chart in Appendix A, Figure

A.1. The total cost used thus far is $159.20 out of the allocated $400.00 for the project budget

shown in Appendix B, Figure B.1. The progress made for the project will be discussed in the

following eight sections. The sections refer to the regions of the power curve [1] shown in Appendix

C, Figure C.1 and the low voltage ride-through curve [2] shown in Appendix D, Figure D.1.

2.1 Pitch Angle Control in Software (Ajaypal, Laraib)

The pitch angle control was designed to change the blade angle of the wind turbine model in

RSCAD. The pitch angle can be modified using a control system which receives the wind turbine

speed as an input and calculates the pitch angle in degrees as an output. A comparator block was

designed that sends the turbine speed as an input to the pitch angle control system for wind speeds

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Supervisory Controller 2 Project Progress

between 11.5 m/s and 20 m/s. The control system contains a limiter that limits the blade angle

between 0 and 36 degrees. The calculated pitch angle is then sent back to the wind turbine through

a feedback loop in order to maintain rated power output for wind speeds between 11.5 m/s and 20

m/s.

2.2 Optimum Power Control in Software (Ajaypal, Laraib)

In order to maintain a constant tip to speed ratio for winds speeds between 3 m/s and 11.5

m/s, an optimal power calculation logic was simulated to determine the optimum torque for any

given wind speed. The optimum torque enables the control of the rotor speed of the Doubly-Fed

Induction Generator (DFIG). In order to implement a constant tip to speed ratio in hardware,

the understanding and testing of the provided optimum power block in RSCAD was necessary, as

explained further in the hardware section.

2.3 Breaker Control in Software (Ajaypal)

Control logic was designed which detects the wind speed and determines whether the wind turbine

system should be connected to the transmission system. A breaker control system was simulated

which disconnects the wind turbine system from the grid for wind speeds below 3 m/s and above

20 m/s.

2.4 Fault Introduction and Duration Control in Software (Laraib)

The simulation of the wind turbine for fault conditions began with the design and introduction of

a 50 km transmission line within a separate RSCAD file. The transmission line connects the wind

turbine to the strong grid, enabling the introduction, detection, and control of faults on the sending

end of the transmission line after a 33kV/230kV step-up transformer.

A 3-phase line to ground fault simulating a worst case scenario was introduced using a push

button. The plot of the three phase voltage displayed the effect of the fault on both the turbine

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Supervisory Controller 2 Project Progress

and the power grid sides of the line. The next step was to control the duration of the fault, which

provided a method to determine the voltage recovery time of the system for varied fault durations.

2.5 Pitch Angle Control in Hardware (Abulizijiang, Daniel)

To maintain constant rated power output for wind speeds between 11.5 m/s and 20 m/s, the power

output is controlled through the control of pitch angle. An Arduino Due microcontroller reads the

wind speed through an analog input converting this voltage to a numerical value. If the wind speed

is under 11.5 m/s, the pitch angle is set to zero by sending a zero voltage through a DAC to RDTS.

Once above 11.5 m/s, the speed of the rotor is measured through an analog input pin. The rotor

speed should be maintained at a rated speed of 1.2 pu, resulting in maximum power output of 2

MW. As the wind speed increases, the rotor speed will also increase. The rotor speed is decreased

by stepping up the voltage sent from the DAC to RDTS, which results in an increase of pitch angle

to maintain the rotor speed at 1.2 pu.

2.6 Optimum Power Control in Hardware (Daniel)

The turbine power is controlled by a constant tip to speed ratio between wind speeds of 3 m/s

and 11.5 m/s through the calculation of optimum torque. The rotor speed is measured through

an analog pin on the Arduino Due. Taking into account the turbine speed ratio and DFIG to

turbine factor, the optimum torque is calculated on the Arduino Due and sent back to RDTS.

With the use of the slip angle, the rotor currents in RSCAD are converted into their respective

direct and quadrature axis components, allowing control of electrical torque and excitation current.

The calculated quadrature axis rotor current is subtracted from the reference signal, which is the

optimum torque that the Arduino Due calculates, which in turn adjusts the firing angle of the rotor

side voltage source converter.

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Supervisory Controller 2 Project Progress

2.7 Fault Detection in Hardware (Abulizijiang, Daniel)

Issues arose with being able to detect a fault because the Arduino Due cannot accept negative

voltage on its analog pins. Therefore, the full wave line voltage could not be used. The first

solution was to send the line voltage to the Arduino Due through a half wave rectifier with a

smoothing capacitor. When a fault occurs, the line voltage drops to zero. Smoothing the waveform

with a capacitor between half waves would keep the voltage above zero and an interrupt could be

used to detect a voltage drop to zero. This method would, however, introduce a delay of a few

milliseconds if a fault occurred during the smoothing cycle. Also, the Arduino Due’s interrupt

would trigger at a low voltage of 1.5V causing a fault to almost constantly be detected. Therefore,

a new method was required.

A full wave rectifier could not be used because RTDS was unable to provide the positive and

negative of the line voltage signal. The second method designed was to use a summing amplifier.

The full waveform of the line voltage could now be used without a rectifier and no interrupts.

A DC offset was inputted to shift the waveform above zero volts. When a fault occurs, the DC

offset voltage is the new zero voltage and the offset voltage can be used to determine if a fault has

occurred.

2.8 Low Voltage Ride-Through in Hardware (Abulizijiang)

Using the line voltage mentioned in section 2.7, an analog input pin was assigned for reading the

line voltage, and an output pin was assigned for tripping the system. The line voltage was scaled to

an acceptable range for the Arduino Due. When the system needs to be stalled, the tripping signal

is set to low, which results in the transmission line breakers to trip. At the same time, the electrical

torque is set to zero, causing the rotor speed to drop to zero as well. When the system needs to

be reconnected, the tripping signal is set to high, resulting in the closing of the breakers and the

DFIG to be connected back to the strong grid. The tripping signal functionality was successfully

tested for normal and fault conditions with the interface of RSCAD and RTDS.

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Supervisory Controller 3 Future Work

LVRT was implemented on the Arduino Due by reading the line voltage using a polling method.

The polling method reads the line voltage each time the Arduino Due cycles through its entire

program. The line voltage is a sinusoidal waveform with a DC offset that passes through the offset

voltage every 8.33 milliseconds. If the offset voltage is detected, the line voltage is instantly read

again in order to determine whether a fault has occurred. If a fault is detected, the program is

delayed by 130 milliseconds in order to obtain the 150 milliseconds duration based on Appendix D,

Figure D.1. The tripping signal is set to low if the fault has not been cleared at this time instant. In

order to avoid the 150 milliseconds delay during the next cycle, a fault condition boolean variable

is set to true, and a counter begins to increment. At the moment that the counter has reached

a value corresponding to a 3 second duration, the line voltage is read again. If there is a voltage

recovery of 85%, the system is reconnected by setting the tripping signal to high.

3 Future Work

Future work will consist of the design of a breaker control system in RSCAD. The breaker system

will detect whether a fault has occurred on the sending end of the transmission line. If a fault is

detected, the breaker system will use control logic in order to disconnect the wind turbine from the

strong grid. The control logic will perform the low voltage ride-through based on the Canadian Grid

Code. Upon the successful completion of the supervisory controller functionality for both software

simulation and hardware implementation, the software and hardware performance of pitch angle

control, optimum power, real output power, and low voltage ride-through will be compared.

The length of the transmission line will be varied, and the behavior of the system will be

analyzed. The pitch angle control, optimum power, and low voltage ride-through will also be

optimized to improve system performance. However, the varying of the length of the transmission

line and the optimization of the hardware system are beyond the scope of the project proposal and

will be completed if time permits.

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Supervisory Controller 4 Conclusions

4 Conclusions

As of present, the project is progressing on schedule as can be seen in the updated Gantt Chart.

Individual members of the team have fulfilled their respective roles and responsibilities towards the

project. The total cost used thus far is $159.20 out of the allocated $400.00 for the project budget.

The tasks to be completed include the design of the breaker control system in RSCAD simulation.

The project is expected to be completed by the proposed deadline.

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Supervisory Controller REFERENCES

References

[1] Vestas. 2 mw platform (2013 edition). [Online]. Available: http://www.vestas.com/en/products and services/turbines

[2] G. Hassan. Canadian grid code for wind development- review and recommendations (2005 edi-tion). [Online]. Available: http://www.nrcan.gc.ca/energy/publications/sciences-technology/renewable/smart-grid/6081

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Supervisory Controller

Appendix A

Updated Gantt Chart

The updated Gantt chart for the project is shown in Figure A.1. The project is progressing on

schedule. The leftmost column shows the milestones and the corresponding tasks that are to be

completed for the project. The orange bars in the Gantt chart represent the total expected time

to complete each milestone. The bars that are colored in blue represent the expected start and

completion date of each task. The bars that are colored in red represent the actual start and

completion up-to-date of each task.

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Supervisory Controller

Fig. A.1: Project Gantt Chart

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Appendix B

Updated Budget

The total expected cost is $359.20 out of the budget of $400 that is allocated for the capstone

design project as shown in Figure B.1. The only cost comes from ordering one Arduino Due and

two MAX520BCPE+-ND DACs, both supplied by Digikey. An overhead cost of 20% has been

included to cover costs of components supplied by the tech shop. A replacement development kit

is still included in the budget and has been allocated $200. However, the Arduino Due has been

sufficient thus far, and there has been no need to order a new kit.

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Supervisory Controller

Fig. B.1: Project budget

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Appendix C

Power Curve

The supervisory controller must control operation of the turbine under normal conditions based

on the power curve of the V110-2.0 MW shown in Figure C.1. For wind speeds under 3 m/s, the

turbine will be stalled. At the cut-in wind speed of 3 m/s up to the rated wind speed of 11.5 m/s,

the turbine will operate at a constant tip to speed ratio through the control of rotor speed. From

the rated wind speed of 11.5 m/s to the cut-out wind speed of 20 m/s, the pitch angle of the turbine

will be controlled to maintain a constant rated power of 2MW. Due to engineering design limits

and safety constraints, the turbine will be stalled at wind speeds above 20 m/s.

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Supervisory Controller

Fig. C.1: Power Curve

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Appendix D

Low Voltage Ride-Through

According to the Canadian Grid Code for Wind Development, the wind turbines must adhere to

the LVRT curve as shown in Figure D.1. When a fault occurs, the wind turbine will continue

operating for a period of 150ms after which the turbine must be stalled. After a total duration of 3

seconds after a fault has occurred, the system will check for an 85% or greater recovery of voltage.

If the voltage has recovered to the 85% or greater level, the turbine will be re-connected to the

system. However, should this threshold not be met after the 3 second time interval, the system will

remain stalled.

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Supervisory Controller

Fig. D.1: Low Voltage Ride-Through

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