Load Compensation in Three Phase Power Systems

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Art: Diplomarbeit
Autor: Andreas Beuschel
Abgabedatum: November 2002
Umfang: 166 Seiten
Note: 1,0
Institution / Hochschule: Fachhochschule Regensburg Deutschland
ISBN (Paperback) :
978-3-8324-6836-1 P
ISBN (CD) :978-3-8324-6836-1 CD
Sprache: Englisch
Prämierung:
Arbeit zitieren: Beuschel, Andreas November 2002: Load Compensation in Three Phase Power Systems, Hamburg: Diplomica Verlag
Schlagworte: Digital Signal Processor, Remote Monitoring, LEM, TMS320F243 Texas Instruments DSP, Czarnecki

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Diplomarbeit von Andreas Beuschel

Abstract:

The object of this thesis is to design software and hardware to obtain the device parameters of a compensator. This compensator should restore the balance and the power factor of a three-phase three-wire system by using reactive elements only. The derived parameters should be accessible remotely and displayed on a PC.

L. S. Czarnecki recently presented a highly respected approach to derive the device parameters of the compensating susceptances. He defined the admittances Ye and A which represent the conditions in a three-phase system. He also suggested a way to derive these susceptances by measuring two line-to-line voltages and two line currents. The load balancing technique used in this project was based on Czarnecki’s approach.

The first phase of the project concentrated on understanding and proving the theory behind the project by means of computer simulation.

The second phase of the project involved writing software for the DSP and building an interface to successfully task the requirements set by the theory. The aspect of being able to transfer the data to a PC via a modem-to-modem connection was taken into account too.

In the final stage it is shown that the implemented system is able to derive the necessary parameters in order to balance the currents and restore the power factor as supplied from mains. It was found that even though the supply from the University of Cape Town does not meet the requirements of the theory in terms of harmonic distortion, it is possible to achieve sufficient load balancing and power factor correction.

It was not possible to establish a reliable connection from one modem to the other because of the limitations of the telephone exchange system used at the University of Cape Town. The parts that are necessary for communication, however, were implemented and tested successfully. Therefore it was solely a reliable transmission of data that was unsuccessful and this was due to factors beyond the control or influence of the author.

Table of Contents:

	ERKLÄRUNG	II
	Acknowledgements	III
	Terms of Reference	IV
	Synopsis	V
	Table of Contents	VI
	List of Figures	X
	List of Tables	XIII
	Glossary	XIV
1	Introduction	1
1.1	The Need for Load Compensation	1
1.2	The Thesis as a Part of a Project	2
1.3	Objectives of the Thesis	2
2	Theory for Balancing a Three-Phase Three-Wire System	3
2.1	Fictitious Impedance	3
2.2	Sufficient Condition for Balancing a Three-Phase Load	5
2.2.1	Compensator to Balance Currents	6
2.2.2	Compensator with Reactive Susceptances	8
2.3	Single-Phase Load as an Extreme Case of Imbalance	9
2.4	Resistive Single-Phase Load	11
2.5	Resistive and Reactive Load	13
2.6	Extension from an One-Phase to a Two-Phase Load	15
2.7	Further Equations	16
2.8	Conclusion	17
3	Computer Simulations	18
3.1	Orcad	18
3.2	Matlab m-file	21
3.3	Simulink	22
3.3.1	Results of the Simulations	23
a	Single Resistor	23
b	Load with Three Resistors (unbalanced / symmetric)	25
c	Load with Resistors and Reactances	27
4	Hardware Description	30
4.1	DSP TMS320F243 from Texas Instruments	30
4.1.1	Interrupts	30
4.1.2	Event Manager (EV2)	32
4.1.3	Digital Input / Output Ports (I/O)	33
4.1.4	Interfaces for Communication	35
a	Serial Communication Interface (SCI)	35
b	Serial Peripheral Interface (SPI)	36
4.1.5	Analog to Digital Converter (ADC)	37
4.2	Intelligent Liquid Crystal Display (LCD)	39
4.3	DSP Board	41
4.3.1	Digital to Analog Converter (DAC)	42
4.4	Interface Board	43
4.5	LEM-box	45
4.6	Phase Shifting Circuitry	49
4.7	Modems and their Usage	50
4.7.1	The Hyper Terminal	51
4.7.2	The AT-Command Set	52
5	Software Description	53
5.1	The File System to Program the DSP	53
5.2	The EditPlus Editor	55
5.3	Description of the Functions Implemented in the Program	56
5.3.1	Function arctan	56
5.3.2	Function decimal	59
5.3.3	Function displaydigits	60
5.3.4	Function DACoutput	60
5.3.5	Function byteTX	61
5.3.6	Function strInRXBuf	61
5.3.7	Function waitRXOK	62
5.4	The Main Function	63
5.4.1	Settings and Initializations	64
a	LCD	64
b	Interrupts	64
c	Timer	65
d	SPI	66
e	SCI	66
f	Cellular Modem	66
5.4.2	Infinite Loop	67
a	Calculations	67
b	Presentation of the Results on the LCD	68
c	Communication Part	68
5.5	Interrupt Service Routines (ISRs)	69
5.5.1	GPT1_Periodmatch Interrupt	69
a	Processing the Reading of Current I1	70
b	Processing of Current I1 and Voltage V13	70
c	Processing after 2048 Readings	71
5.5.2	SCIRXTX Interrupt	71
6	Results and Discussion	72
6.1	Balancing a Resistive Single-Phase Load	72
6.2	Balancing a resistive and reactive Single-Phase Load	75
6.3	Balancing a Resistive Three-Phase Load	76
6.4	Balancing a Three-Phase Load with Reactances	80
6.5	Communications	83
7	Conclusions	86
	Bibliography	87
	Internet Links	88
	Appendices	89
	Appendix A	89
	Appendix B	91
	Appendix C	97
	Appendix D	101
	Appendix E	125
	Appendix F	126
	Appendix G	129
	Appendix H	130
	Appendix I	131