Diagnostics

Lesson 3

Ewen Ritchie Krisztina Leban

1

2

1. Converter faults - General

2. PMSM + Inverter

3. IM + Inverter

4. DFIG + Inverter

5. References

6. Hybrid EV + Matrix converter

8. Monitoring - SCADA

When Dealing with Faults

� Monitor healthy systems

�Prevent system shutdown– the fault is incipient

� Identify fault – after shutdown

� Fault ride-through – surviving the fault

3[11]

Fault – Industrial Plants

� high nonlinearity

� noisy signals

� uncertainty

4[11]

Fault Diagnosis Systems

5[11]

� Using Hardware Redundancy

- uses multiplication of physical devices

- voting system - detects the fault and its location in the system

- expensive – need of extra equipment

� Using Analytical Redundancy.

- redundant functions between system variables

- no extra equipment is necessary

Fault diagnosis Task

6[11]

-consists of two main stages:

� residual* generation – algorithm

� decision making - examining the residual signals to locate

and isolate the fault

*A residual - procedure for extracting fault symptoms from the system, using available input and

output information;fault indicator, based on deviation between measurements and model-

equation-based computations

Modeling Systems with Faults

7[11]

� Compromise between model complexity and fault

simulation results

� If linearity cannot be assumed, linearise the system around

a few operating points

� Modeling errors affect the performances of the fault

diagnosis - especially for nonlinear systems

Modeling Systems with Faults -

Approaches

8[11]

� stochastic algorithms -for random processes

- neural networks

- fuzzy logic-based systems

- neuro-fuzzy hybrids

� evolutionary

- genetic algorithms

PMSM+INVERTER

9

Inverter + PMSM

10

Faults in the voltage source inverters

(PMSM)

1) DC link capacitor short-circuit fault

2) Open-circuit fault of inverter switch When the short

3) Short-circuit fault of inverter switch

11[1]

Faults in the voltage source inverters

(PMSM)

1) DC link capacitor short-circuit fault

detected by the DC link voltage sensing circuits.

2) Open-circuit fault of inverter switch

- abnormal over-current flows through inverter and machine,

- one of the over-current effects demagnetization fault of the PMSM

- the current distortion of the machine causes noise and vibration in the driving system

- bearing problem.

- open-circuit fault slow response compared with short-circuit fault.

- detection methods for open-circuit damage of a switch – voltage sensing devices

- some methods have slow responses - several current vector cycles pass before detecting

- possibility of wrong detection due to the indirect current sensing.

3) Short-circuit fault of inverter switch

- over-current - detection circuit.

12[1]

Conventional Switch Open Fault Detection Method

-use of a voltage sensor - sense the actual voltage applied to each phase of

the machine for the open-switch fault detection.

The voltage sensors can be inserted at the desired location to detect the

open-switch fault.

According to the location of voltage sensors, the detection techniques can be

classified as follows.

1) Terminal voltage measure method

2) Line voltage measure method

3) Phase voltage measure method

4) Neutral voltage measure method

13[1]

Open Fault Detection Method – voltage sensor

These methods

-have the relatively short fault detection time – fault measured when happens

-require the additional hardware - voltage sensors and isolation circuits.

-inverter output is PWM generated – expensive:

�voltage sensors and isolation circuits

�which detect the small amount of voltage drops in the switches,

�large reverse voltages,

�and turn on/off delay time are required to have high resolution gate

drive circuit for the open-switch fault detection.

-When the switches are turn on, the fault is judged by measuring the voltage

drops of the switches.

14

Open Switch Diagnosis

*only applicable to a specific gate drive circuit,

*hard to detect the faults when the gate drive circuit is broken.

15[1]

1. Built in voltage sensor

*detects the open-circuit fault in a phase leg without additional hardware

*detection by observing the difference between actual current and reference current.

* causes fault detection time delay - observing and saving the current vector trajectory of one cycle.

*needs large memory space to save the current vector trajectory

*no practical use in slow speed region - requires more memory space.

*fault detection method suited for sinusoidal current control scheme.

*may give detection errors at the high speed region and transient state (when the current suddenly

changes).

16[1]

Open Switch Diagnosis

2. Analyzing Current Vector Trajectory

Voltage Distortion In The Normal Switches

17[1]

18

IM+INVERTER

Induction Motor Drive Faults

19[3]

Voltage – fed inverter induction motor drive system

Various types of faults that can be classified as follows:

1) Input supply faults.

2) Three phase rectifier faults.

3) Three phase inverter faults.

4) Induction motor faults.

20[3]

21

DFIG+INVERTER

Doubly-Fed Induction Generator

22[6]

Open Switch Faults on Doubly-fed Induction Generator

-local effect - current flowing through the faulty converter-global effect is an effect on other system variables.

the current of the faulty phase loses one half cycle every period, either positive or negative depending on whether the top or bottom switch is faulty.

The current waveform of the faulty phase is similar to the current waveform of a halfwave rectifier.

According to the assumption that the summation of all three-phase currents is zero (ia+ i + ic = 0)

the other two healthy phase currents have DC offset. This local effect is presented in Fig 2.

23[6]

Fault Waveforms

24[6]

Rotor currents with one open

switch fault of the machine side

converter open

Line side converter currents with one

open switch fault of the line-side

converter open

Open Switch Fault – Global effects

-open switch fault does not immediately damage the converter or

cause any protection system to trip,

-can cause severe damage to the mechanical parts of the

generator and the turbine.

Generally, the operating speed of the DFIG is in the range of 3300

above and below synchronous speed.

The frequency of the rotor current referred to a stationary

reference frame will then vary from 0 to 3300 of line frequency.

25[6]

Open Switch Fault

26[6]

Line Side Converter CurrentsStator Currents

Figures: the effect of an open switch fault at phase A of the

machine-side converter under super synchronous generation.

Open Switch Fault – Machine Side

Converter

27[6]

Electromagnetic Torque Stator Active and Reactive Power

DFIG Inverter Open Switch

Fault Symphtoms

machine-side converter fault :

- torque oscillations which may cause

- low frequency speed oscillations and

- low frequency vibration of the generator shaft

an open switch fault in the machine side converter can also

cause a low frequency oscillation of the stator P and Q of the

generator.

28[6]

Spectrum of Torque

29[6]

Under Healthy ConditionOpen Switch Fault –

Machine Side Converter

Line-Side Converter

An open switch fault has less effect than a fault in the machine-

side converter.

The effect on generator variables is negligible. There is no

significant oscillation appearing on the stator active power and

reactive power signal as well as stator current.

However, once the open switch fault appears in the line side

converter, there is a DC component appearing on all three phase

currents of the line-side converter.

This can cause saturation in the inductor filter and the

transformer.

30

Open Switch Fault – Line-Side Converter

31

Stator Active and Reactive Power Stator Currents

Open Switch Fault Diagnosis Methods

� Park's Vector Method

� Slope Method

� Control Deviation Method

� Normalized DC Current Method

� Modified Normalized DC Current Method

� Simple DC Current Method

32[1]

33

HYBRID EV Dirive

Hybrid Electric Vehicle

34[7]

Control of HEV Drive

35[7]

36[7]

By using the matrix

converter-the large dc-bus

capacitor can be removed.

Four-leg-based fault tolerant matrix

converter

37[7]

� faulty module is isolated

� the controller replaces the faulty leg with the redundant one

� the developed fault-tolerant matrix converter drive can maintain sinusoidal input and output currents, even under fault situations.

� the function of breaking is performed by the clamp circuit of the matrix converter

Fault Tolerant Control Flowchart

38[7]

Supervisory Control And Data Acquisition

39

SCADA

SCADA

40[12]

SCADA is an application that collects data from a system and send them to a central computer for monitoring and control usages.

Remote measurements, reporting data and monitoring information are known as telemetry.

� SCADA Hardware: -A SCADA (RTU) system is made of a number of remote terminal units -collects data and sending them back to the main station. (wire, fiber optic, radio, telephone line, GPRS and even satellite.)

-The main station (or centre) collects data from the different RTUs and drives an interface to display information and control the remote sites.

�SCADA Software: -open source or proprietary; compatibility problems between the two

Condition monitoring

41[12]

The collection of data, communicating, transferring, analysing

and finally displaying the information on operator screens is

extremely important and can be seen in a supervisory control

system known as SCADA

Obtaining Residuals

42[12]

Signal analysis: a model-free method based on time and frequency signal analysis which are state-of-the-art in process monitoring.

Spectrum analysis method - includes Fourier Transformer - developedcurves which derive faults. This method has successfully been applied to estimate lifetime and other diagnosis purposes especially in rotating machinery

Methodology

43[12]

FACTS Background – Fault Ride-Through

44[14]

Flexible AC Transmission System (FACTS)

-solutions for fast dynamic control of the interrelated parameters (voltage,

impedance, and phase angle) of high voltage AC transmission systems

results:

increased power transfer capability,

increased power system security,

reliability

availability

increased dynamic and transient stability of the power system grid.

Devices for controlling and optimizing the dynamic performance of power

system include

STATCOM

Static Synchronous Series Compensator (SSSC)

Unified Power Flow Controller (UPFC).

The STATCOM – Fault Ride-Through

45[14]

�The STATic Synchronous COMpensator (STATCOM) is a shunt-

connected reactive power compensation device has the capability of

absorbing and/or generating reactive power.

�Reactive power must be fed into the short circuit- VPP-fault ride-through

The STATCOM output varied to control the interrelated parameters of an

electric power system.

The main building block of STATCOM is a Voltage Source Converter (VSC)

-the VSC output+ relatively small reactance (which is provided by either a

reactor or the leakage inductance of a coupling transformer).

End. see refs..

46

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[1]Simple Switch Open Fault Detection Method of Voltage Source Inverter Shin-Myung Jung†, Jin-Sik Park†, Hyoung-Suk Kim†, Hag-Wone Kim‡,

and Myung-Joong Youn† †Department of Electrical Engineering and Computer Science, KAIST 978-1-4244-2893-9/09/$25.00 ©2009 IEEE

[2]Failure-Mode Analysis and Protection of Three-Level Neutral-Point-Clamped PWM Voltage Source Converters Fei Wang, Fellow, IEEE, Rixin

Lai, Student Member, IEEE, Xibo Yuan, Student Member, IEEE, Fang Luo, Student Member, IEEE, Rolando Burgos, Member, IEEE, and Dushan

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 2, MARCH/APRIL 2010

[3]DEVELOPMENT OF AN EXPERT SYSTEM TO FAULT DIAGNOSIS OF THREE PHASE INDUCTION MOTOR DRIVE SYSTEM A.M.Elsaadawi- A.E.Kalas

and M.Fawzi 978-1-4244-1933-3/08/$25.00 ©2008 IEEE 978-1-4244-1933-3/08/$25.00 ©2008 IEEE

[4]Low Order PWM Inverter Harmonics Contributions to the Inverter-Fed Induction Machine Fault Diagnosis Bilal Akin, Student Member, IEEE,

Umut Orguner, Student Member, IEEE, Hamid A. Toliyat, Fellow, IEEE, and Mark Rayner IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS,

VOL. 55, NO. 2, FEBRUARY 2008; 0278-0046/$25.00 © 2008 IEEE

[5]Fault Diagnosis of Frequency Convert System Based on Networked Virtual Instrument Yunfei Li Ge Chen 978-1-4244-3864-8/09/$25.00

©2009 IEEE

[6]Open Switch Fault Diagnosis for a Doubly-Fed Induction Generator W. Sae-Kok and D M Grant Department of Electronic and Electrical

Engineering, University 1-4244-0645-5/07/$20.00©2007 IEEE

[7]Phase-Redundant-Based Reliable Direct AC/AC Converter Drive for Series Hybrid Off-Highway Heavy Electric Vehicles Sangshin Kwak,

Member, IEEE, Taehyung Kim, Member, IEEE, and Gwangmin Park 0018-9545/$26.00 © 2010 IEEE TRANSACTIONS ON VEHICULAR

TECHNOLOGY, VOL. 59, NO. 6, JULY 2010

[8]Convert System Based on Networked Virtual Instrument Yunfei Li Ge Chen 978-1-4244-3864-8/09/$25.00 ©2009 IEEE

[9]Failure-Mode Analysis and Protection of Three-Level Neutral-Point-Clamped PWM VoltageSource Converters Fei Wang, Fellow, IEEE, Rixin

Lai, Student Member, IEEE, Xibo Yuan, Student Member, IEEE, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 46, NO. 2, MARCH/APRIL

2010

[10]Fang Luo, Student Member, IEEE, Rolando Burgos, Member, IEEE, and Dushan 0093-9994/$26.00 © 2010 IEEE

SEMI-CONVERTER FAULT DIAGNOSIS IN DC MOTOR DRIVES, BY PARK'S VECTOR APPROACH A. J. Marques Cardoso and A. M. S. Mendes Power

Electronics and Variable Speed Drives', 23-25 September 1996, Conference Publication No. 429, 0 IEE, 1996

[11] Computational Intelligence in Fault Diagnosis Advanced Information and Knowledge Processing, Computational Intelligence Methodologies

in Fault Diagnosis: Review and State of the Art Cosmin danut Bocaneala and Vasile Palade, 2006, 1-36, DOI: 10.1007/978-1-84628-631-5_1

48

[12] Wind Turbine Condition Monitoring System 3 Month PhD Progress Report By Mani Entezami Supervisors Dr. Stuart Hillmansen Dr.

Clive Roberts 11 January 2010 University of Birmingham SCHOOL OF ELECTRONIC, ELECTRICAL AND COMPUTER ENGINEERING

[13]High Voltage Ride Through with FACTS for DFIG Based Wind urbines C. Wessels, F.W. Fuchs Institute of Power Electronics and

Electrical Drives,

[14]Modelling of Two-level, Multi-Pulse Voltage Source Converter for FACTS Systems M. K. Jalboub, H. S. Rajamani, J.C. Readle, R. A. Abd-Alhameed, A. M. Ihbal ICEGES 2009 Le Royal Hotel Amman, Jordan November, 10-12 2009 International Conference and Exhibition on Green Energy & Sustainability for Arid Regions & Mediterranean Countries School of Engineering, and Design and technology