Static Synchronous Series Compensator Based on Voltage Source Converter with DSP

TMS320LF2407A

Mahesh Kumar koliM-Tech Power system

EEE Department

Project Guide

Dr. Sishaj P Simon

Electrical & Electronics Engg. Deptt.

National Institute of Technology Tiruchirappalli

Objective

• To design a DSP(TMS320LF2407) based SSSC.• Hardware implementation of the SSSC.• Power flow control(Active and Reactive power).• For increasing the power capability and

controllability of the transmission lines.

Introduction

The static synchronous series compensator (SSSC), using a based on VSC-DSP to inject a controllable voltage in quadrature with the line current of a power system, its provide both capacitive and inductive impedance compensation independent of the line current. The VSC based series compensator, is called static synchronous series compensator (SSSC).

Equivalent Circuit Diagram of SSSC

Vq lags by 90° plus (Capacitive Compensation)

Vq Leads by 90° plus (Inductive Compensation)

Vq= Injected AC voltage

The concept of series capacitive compensation

• The basic idea of series capacitive compensation is to decrease the overall effective series transmission impedance from sending end to receiving end, i.e. X in the

The effective impedance of transmission line

K= The degree of the transmission line, i.e.K = Xc/X 0 ≤ k ≤ 1

INTRODUCTION TO THE TMSLF2407 DSP CONTROLLER

• The Texas Instruments TMS320LF2407 DSP Controller is a programmable digital controller with a C2xx DSP central processing unit (CPU) as the core processor .

• The LF2407 contains the DSP core processor and useful peripherals integrated onto a single piece of silicon. The LF2407 combines the powerful CPU with on-chip memory and peripherals.

• The LF2407 DSP controller offers 40 million instructions per second (MIPS) performance. This high processing speed of the C2xx CPU allows users to compute parameters in real time rather than look up approximations from tables stored in memory.

• The “brain” of the LF2407 DSP is the C2xx core, the LF2407 contains several control-orientated peripherals onboard .

• The peripherals on the LF2407 make virtually any digital control requirement possible.

• Their applications range from analog to digital conversion to pulse width modulation (PWM) generation.

• Communication peripherals make possible the communication with external peripherals, personal computers, or other DSP processors.

Brief listing of the different peripherals onboard the TMS320LF2407 A

• Two Event Managers (A and B) • General Purpose (GP) timers • PWM generators for digital motor control • Analog-to-digital converter • Serial Peripheral Interface (SPI) – synchronous serial port • Serial Communications Interface (SCI) – asynchrones serial

port • General-Purpose bi-directional digital I/O (GPIO) pins • Watchdog Timer (“time-out” DSP reset device for system

integrity)

Joint Test Action Group (JTAG) Port

• The JTAG port provides a standard method of interfacing a personal computer with the DSP controller for emulation and development.

• The XDS510PP or equivalent emulator pod provides the connection between the JTAG module on the LF2407 and the personal computer.

• The JTAG module allows the PC to take full control over the DSP processor while Code Composer Studio TM is running.

PC to DSP connection scheme

Memory

• There are three main blocks of memory which are present on the LF2407 chip: B0, B1, and B2.

• Additionally, there are two different memory “spaces” (program, data) in which blocks are used.

• The LF2407 has 544 16-bit words of on-chip DARAM that are divided into three main memory blocks named B0, B1, and B2.

• In addition to the DARAM, there are also 2000 16-bit words of SARAM.

• The main difference between DARAM and SARAM is that DARAM memory can be accessed twice per clock cycle and SARAM can only be accessed once per cycle. Thus, DARAM reads and writes twice as fast as SARAM.

Memory Allocation Spaces

• The LF2407 DSP Controller has three different allocations of memory it can use.

1. Data memory space.

2. Program memory space.

3. I/O memory space.

Data space is used for program calculations, look-up tables, and any other memory used by an algorithm. Data memory can be in the form of the on-chip random access memory (RAM) or external RAM.

The Components of the C2xx DSP Core

• The DSP core (like all microprocessors) consists of several subcomponents necessary to perform arithmetic operations on 16-bit binary numbers.

• A 32-bit central arithmetic logic unit (CALU).• A 32-bit accumulator (used frequently in programs).• Input and output data-scaling shifters for the CALU. • A (16-bit by 16-bit) multiplier. • A product-scaling shifter.• Eight auxiliary registers (AR0 – AR7) and an auxiliary

register arithmetic unit (ARAU).

Memory Addressing Modes

• There are three basic memory addressing modes used by the C2xx instruction set. The three modes are:

• Immediate addressing mode (does not actually access memory)

1. Short-immediate addressing. The instructions that use short-immediate addressing have an 8-bit.

LACL #44h

2. Long-immediate addressing. Instructions that use long-immediate addressing have a 16-bit constant as an operand.

LACC #4444h

• Direct addressing mode • In direct addressing, data memory is first addressed in blocks of 128

words called data pages. The entire 64K of data memory consists of 512 DPs labeled 0 through 511 .

• The DP of a particular memory address can be found easily by dividing the address (in hexadecimal) by 80h.

• Indirect addressing mode • Indirect addressing is a powerful way of addressing data

memory. When using indirect addressing you load the memory space that you would like to access into one of the auxiliary registers (ARx). The current auxiliary register acts as a pointer that points to a specific memory address.

General Purpose (GP) Timers

• A General Purpose (GP) timer is simply a 16-bit counter, which may be configured to count up, down, or continuously up and down.

• There are two GP• Timers in each EV: Timer1 and Timer2 for EVA and Timer3

and Timer4 for EVB.• The GP Timers include: setting the sampling period for the

ADC by triggering the start of conversion; or providing the switching period for the generation of a PWM signal.

Shows a block diagram of a GP Timer. There are two cases that1. When “x” = 2, “y” = 1 and “n” = 22. When “x” = 4, “y” = 3 and “n” = 4

General purpose Configuration Diagram

Each GP Timer consists of the following components

• One readable and writeable (RW) 16-bit up and up/down counter register• TxCNT (x = 1, 2, 3, 4). This register holds the current count value and

increments or decrements depending on the direction of counting• 16-bit timer compare register, TxCMPR (x = 1, 2, 3, 4)• 16-bit timer period register, TxPR (x = 1, 2, 3, 4)• 16-bit individual timer control register, TxCON (x = 1, 2, 3, 4)• Programmable input clock divider (pre-scaler) applicable to both internal• and external clock inputs• One GP Timer compare output pin, TxCMP (x = 1, 2, 3, 4)• Interrupt logic

PWM Technique

• GP Timer Period Registers (TxPR) – User Specified Value Addresses 7403h (T1PR), 7407h (T2PR), 7503h (T3PR), 7507h (T4PR)

• The period register determines the rate at which the timer resets itself or changes direction (the period of the timer).

• This register in combination with the input clock frequency (and clock pre-scale factor) determines the frequency of a PWM signal created by the compare output pin.

• The corresponding timer either resets to “0”, or starts counting downward (depending on the operating mode) when a match occurs between the period register and the timer counter (TxCNT).

Hardware Pictures With DSP

DSO Result Using With DSP

For single phase open loop control of Inverter and output wave form with Resistive loadResistive Load = 50 ohmInput DC Supply = 5 volts.Output Voltage = 3.076 volts.

SPWM Technique with Analog Circuit based

Complete Control Circuit for open loop Single Phase Inverter with Sinusoidal PWM Technique

Hardware Pictures With Analog Circuit

SPWM Signal

Output of the Inverter with Resistive Load

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