Programming and Use of TMS320F2812 DSP to
Control and Regulate Power Electronic Converters

by

Baris Bagci

Thesis submitted to the Faculty of
Information, Media and Electrical Engineering
in partial fulfillment of the requirements for the degree of
Master of Science
in
Electrical Engineering
Institute for Automation Engineering

Cologne, October 2003

Abstract

The purpose of this master thesis project has been to study, operate and program the 32-bit 150MIPS TMS320F2812 DSP developed by Texas Instruments Inc. In addition, it has also been a goal to implement fast estimation techniques for control of resonant converters. For this purpose, PWM signals that are generated using this DSP are used. The demands on the system and the hardware to solve the problem were already decided when I started the work. The algorithms were programmed in C/C++ language, compiled, debugged and transferred to the DSP development board in a compiling and simulation tool (downloader), called CCS (Code Composer Studio v2), also provided by Texas Instruments. In the first chapters of this thesis I give general information about control systems, digital signal processors, digital signal processing and the DSP used in this work. The following chapters tell about PWM, how to configure the PWM outputs and some examples related with PWM signals are given. After a short review of series resonant converters, I presented the last example implemented in this project. I conclude with a summary and provide some hints of future work.

Acknowledgements

I would like to thank everyone at the Faculty of Information, Media and Electrical Engineering at the University of Applied Sciences Cologne, who have helped me to accomplish this diploma work. Special thanks go to Professor van der Broeck for the valuable assistance, guidance and encouragement he gave during the work. Many thanks to Professor Große for acting as the second referee. I also wish to thank Mr. Kellersohn and Mr. Küster for the great co-operation. Last but not least, I would like to thank my parents for the opportunity to do my degree at all.

Baris Bagci

Table of Contents

Abstract ... 1

Acknowledgements  ... 2

Declaration  ... 3

Table of Contents  ... 4

List of Figures & Tables  ... 6

1. Introduction  ... 9
1.1 Power Electronic and Electrical Drive Systems  ... 9
1.1.1 Power Electronic Applications  ... 9
1.1.2 Switched Mode Operation  ... 10
1.1.3 Electrical Drive Applications  ... 11
1.1.3.1 Motion Control  ... 12
1.2 Control Systems  ... 16
1.2.1 Digital versus Analog Implementation  ... 16
1.2.1.1 Review of Today’s Servo Drive Systems  ... 18
1.2.2 Digital PWM Control Using DSP  ... 21
1.3 Digital Signal Processors  ... 23
1.3.1 Data Path of a DSP  ... 28
1.3.2 Peripherals of a DSP  ... 29
1.4 Digital Signal Processing  ... 32
1.4.1 The History of DSP  ... 33

2. The TMS320F2812 DSP  ... 36
2.1 Overview  ... 36
2.2 The Peripherals of F2812  ... 41

3. The eZdsp F2812 Board  ... 47
3.1 Overview  ... 47
3.2 eZdsp F2812 Connectors  ... 49

4. DSP Software Development  ... 54
4.1 Basic Software Tools Required  ... 54
4.2 Code Composer Studio  ... 56
4.2.1 Creating a New Project  ... 56
4.2.2 Adding Files to a Project  ... 57
4.2.3 Building and Running the Program  ... 59
4.2.4 Introduction to Breakpoints  ... 59
4.2.5 Watch Window  ... 61
4.2.6 Probe Points  ... 62
4.2.7 Displaying Graphs  ... 65

5. PWM  ... 67
5.1 Definition  ... 67
5.2 Event Manager PWM Waveform Generation  ... 68
5.3 Generation of PWM Outputs  ... 70
5.3.1 Asymmetric and Symmetric PWM Generation  ... 70
5.3.2 Program Example  ... 72
5.3.3 Dead-Time Generation on the TMS320C2812  ... 77
5.3.3.1 Configuring PWM Outputs with Dead Band  ... 80
5.4 Creating a PWM Signal with Fixed Duty Cycle and Frequency  ... 83
5.5 Creating a PWM Signal with Variable Duty Cycle and Frequency  ... 86

6. Applications  ... 92
6.1 Creating a Sine Modulated PWM Signal  ... 92
6.1.1 Sine Modulated PWM Generation to Control Inverters  ... 95
6.2 Control of a Half-Bridge of a Switched Mode Power Supply  ... 98
6.3 Control of a Series Resonant DC-DC Converter  ... 100
6.3.1 The Series Resonant DC-DC Converter  ... 101
6.3.1.1 SRC Operation Principle  ... 101
6.3.2 The Snubber Effect  ... 108

7. Conclusion and Recommended Continuation  ... 113
7.1 Conclusion  ... 113
7.2 Future Work  ... 113

Bibliography  ... 114

Appendix  ... 119
A. Program Codes  ... 119
B. Circuitry and Wiring Diagram of the Experimental Set-Up  ... 136
C. Acronyms and Abbreviations  ... 138
D. Schematics of the eZdsp F2812 Board  ... 140
E. Sine Values Contained in sinus.dat  ... 145

List of Figures & Tables
Figure 1.1 Power Electronic System Consisting of Power Electronics and Control  ... 9
Figure 1.2 Electrical Drive Consisting of Power Electronics, Electrical Machine and Control  ... 11
Figure 1.3 Basic Structure of a Typical Motion Control System  ... 13
Figure 1.4 Typical Microcontroller-Based Digital Control System Diagram for PWM DC/DC Converter  ... 20
Figure 1.5 Typical DSP-Based Digital Control System Diagram for PWM DC/DC Converter  ... 21
Figure 1.6 Architecture of Digital PWM Using Digital Signal Processor  ... 22
Figure 1.7 MAC Operation  ... 24
Figure 1.8 In DSPs, an Analog Signal such as Voice is Digitized by an Analog-to-Digital Converter  ... 25
Figure 1.9 Harvard Architecture  ... 25
Figure 1.10 Von Neumann Architecture  ... 26
Figure 2.1 A New TI DSP Product Line: 32-bit Flash Mixed Signal DSP  ... 36
Figure 2.2 C28x DSP Core  ... 37
Figure 2.3 On-Chip 12-bit Analog-to-Digital Converter  ... 38
Figure 2.4 2 On-Chip Event Managers  ... 39
Figure 2.5 TMS320F2812 DSP Simplified Hardware Diagram  ... 39
Figure 2.6 IQmath Library: Floating Point on a Fixed Point Machine  ... 40
Figure 2.7 IQmath Approach  ... 40
Figure 2.8 Block Diagram of the F2812 ADC Module  ... 44
Figure 3.1 Block Diagram of the eZdsp F2812  ... 48

[...]

Tables
Table 1.1 Evolution of DSPs  ... 34
Table 3.1 eZdsp F2812 Connectors  ... 50
Table 3.2 P8, I/O Connectors  ... 52
Table 3.3 P9, Analog Interface Connector  ... 53
Table 5.1 Deadband Register Settings for Dead-Band Generation  ... 89
Table 6.1 States of DIP Switches in Prg a  ... 96
Table 6.2 States of DIP Switches in Prg b  ... 98
Table 6.3 SRC Operating Modes  ... 102
Table E.1 The Sine Values Stored in File  ... 145

1. Introduction

1.1 Power Electronic and Electrical Drive Systems

The market for power electronics and power-electronic-controlled electrical drives is rapidly growing. Often, the application of power electronic and electrical drive (PE&ED) systems requires careful engineering because PE&ED systems are utilized as energy converters or as actuators embedded in larger engineering systems. Control systems are required to obtain the desired characteristics of the PE&ED systems and the entire application. The diversity of applications is reflected in a correspondingly wide range of control methods. Hence, a large variety and a large volume of control systems have to be designed, implemented and tested.

1.1.1 Power Electronic Applications

Power electronics constitutes an electrical engineering system, which is always embedded in a system comprising an electric power supply and an electrical load as depicted in Figure 1.1. Note that power electronics itself does not constitute a source of electric power but transforms electrical energy. Electrical energy can be supplied by the electric utility grid comprising remote energy sources and transmission devices. Alternatively, it might be supplied by local energy sources, such as solar cells, wind or hydro generators or energy storage elements like electrochemical batteries [1].

Figure 1.1 Power Electronic System Consisting of Power Electronics and Control Embedded between a Power Supply and an Electrical Load
[in Downloaddatei enthalten]

If the characteristics of the energy source do not meet the requirements of the load then power electronics is used as an interface between the energy source and the load. This might for instance be related to the amplitude of dc systems, the amplitude and frequency of fixed frequency ac systems or disturbances caused by other loads connected to the same power supply. Thus, the task of power electronics can be defined as converting electric energy and controlling the flow of electric power by means of power semiconductor devices in accordance with the requirements of the load. The latter may comprise specifications on amplitude, frequency, and number of phases, allowed harmonic distortion and transient voltages. High efficiency is most often a major requirement for power electronic circuits due to the cost of energy and cooling systems.

Power electronics covers a wide range of applications including the following [1]:

• Energy conversion as part of electrical drives
• DC/DC converters of virtual any power range
• Unity-power-factor rectifiers for applications including railway traction drives which operate of a single-phase ac catenary supply
• Generation of (multi-phase) voltage systems of virtually any frequency or amplitude
• Power engineering applications such as ‘flexible ac transmission systems’ optimizing the utilization of electrical power transmission equipment

Most current power electronics (PE) systems are implemented using an intermediate dc link between two stages of power conversion. Depending on the energy storage element used, these systems impress voltages or currents on their loads and are thus called voltage source inverters (VSIs) or current source inverters (CSIs), respectively.

1.1.2 Switched Mode Operation

‘Switched mode operation’ is applied by power electronic circuits due to efficiency requirements and feasibility. In contrast, linear electronic systems use semiconductor devices as adjustable resistors by operating them in their linear region. This results in a low energy efficiency, which is not tolerable or even feasible at high energy levels or the energy density prevailing in power electronics [2]. For this reason, power electronics embodies power semiconductors used as switches that are either (ideally) fully on or fully off. The power semiconductors are operated that way that they switch between conducting and blocking states in a cyclic manner. The high efficiency achieved by this ‘switched mode’ operation is quite important due to the cost of wasted energy and the difficulty of removing the generated heat.

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