Re: [PIC] Problem With Three Phase - Controlled Half Wave Rectifier
Edit:
The explanation of the working of Three Phase - Half Wave Rectifier in this video is wrong in the sense that it doesn't show the condition when two SCRs are On in the half wave rectifier.
https://www.youtube.com/watch?v=mi26LHNmXj0
If firing angle alpha is 0 then,
SCR1 will conduct from 0 to 180 degrees
SCR1 and SCR2 will both conduct from 120 degrees to 180 degrees
SCR2 will conduct from 120 to 240 degrees
SCR2 and SCR3 will both conduct from 180 degrees to 240 degrees
SCR3 will conduct from 240 to 360 degrees
SCR3 and SCR1 will both conduct from 240 degrees to 300 degrees
All Angles are w.r.t SCR1
Am I right ?
From the graph I see that magnitude (width) of ZCD R is not correct because magnitude of Phase R is not correct.
Also the ZCD B signal and Load signals are strange.
What is the problem ?
In the previous post I attached monochrome schematic and in that it is difficult to analyze graph data.
Here I am attaching color schematic. It will be easier to analyze the graph. Also schematic is changed. For ZCD circuits I used opto-couplers.
- - - Updated - - -
Edit:
mikroC PRO PIC project attached.
I see problem in ISR code.
I am considering three conditions for analyzing the ISR code and only considering SCR1 and SCR2 for analysis but it also applies for SCR2,SCR3 pair and SCR3,SCR1 pair
Condition 1
If firing angle is 0 degrees then at INT0 ZCD the Timer is started and it immediately without delay interrupts and fires the SCR1 and then there is 120 degree (6.67ms) for INT1 to occur. This condition has no problem with the code and also the 300us delay inside the ISR doesn't cause problem.
Condition 2
If firing angle is 120 degrees then INT0 occurs at 0 degrees and then timer runs for 6.67 (120 degrees) and then it interrupts to fire SCR1 but at the same time it is ZC for SCR2 and INT1 triggers and when INT1 triggers Timer is reset and restarted. So, what happenes here ? Timer ISR has 300us delay.
Condition 3
If firing angle is > 120 and <= 180 degrees then at 0 degree INT0 triggers for SCR as it is ZC for SCR1 circuit and a timer interrupt of more than 6.67ms (120 degrees) and <= 10ms (180 degrees) will be running but at 120 degrees that is 6.67ms INT1 (ZC for SCR2 Circuit) triggers and this resets and restarts the timer and so the SCR1 never triggers. Also same when INT2 triggers, timer is cleared and SCR1 never triggers and this repeats and so none of the SCRs fire. In INTx ISR there is a variable to select SCR for firing and it is scr_select_counter.
How to solve these problems ?
| Code C - [expand] |
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| /*
* Project name:
Three Phase - Controlled Half Wave Rectifier
* Revision History:
20170406:
- initial release (A);
* Description:
Three Phase - Controlled Half Wave Rectifier Using SCRs
* Test configuration:
MCU: PIC18F46K22
**broken link removed**
Dev.board: Custom Board
Oscillator: XT, 4.0000 MHz Crystal
Ext. Modules: None.
SW: mikroC PRO for PIC
[url]https://www.mikroe.com/mikroc/pic/[/url]
* Author(s): Okada
* Project Start Date: 04/04/2017
* Project Completion Date:
* NOTES:
- Three Phase - Controlled Half Wave Rectifier
*/
// LCD module connections
sbit LCD_RS at LATE0_bit;
sbit LCD_EN at LATD0_bit;
sbit LCD_D4 at LATC3_bit;
sbit LCD_D5 at LATC2_bit;
sbit LCD_D6 at LATC1_bit;
sbit LCD_D7 at LATC0_bit;
sbit LCD_RS_Direction at TRISE0_bit;
sbit LCD_EN_Direction at TRISD0_bit;
sbit LCD_D4_Direction at TRISC3_bit;
sbit LCD_D5_Direction at TRISC2_bit;
sbit LCD_D6_Direction at TRISC1_bit;
sbit LCD_D7_Direction at TRISC0_bit;
// End LCD module connections
sbit R_Phase_SCR_Gate_Trigger at LATD5_bit;
sbit Y_Phase_SCR_Gate_Trigger at LATD6_bit;
sbit B_Phase_SCR_Gate_Trigger at LATD7_bit;
#define PHASE_R 0
#define PHASE_Y 1
#define PHASE_B 2
const code char txt1[] = "F Angle: ";
const code char txt2[] = "C Angle: ";
const char character[] = {6,9,9,6,0,0,0,0};
char txt[32], i = 0;
unsigned char scr_select_counter = 0;
unsigned int timer_reload_value = 0x0000;
unsigned int raw_adc_value = 0, previous_raw_adc_value = 2048;
double scr_firing_delay_in_seconds = 0.0;
double previous_scr_firing_delay_in_seconds = 20.0;
double fosc = 4000000.0, timer_prescalar = 1.0;
double mains_frequency = 50.0;
double period = 0.0;
double duration_for_half_wave_of_ac = 0.0;
double duration_for_120_degrees = 0.006467;
double minimum_gate_trigger_delay = 0.0003;
double adc_factor = 0.0;
double timer_resolution = 65536.0;
double timer_tick_period = 0.0;
double scr_firing_angle = 0.0;
double scr_conduction_angle = 0.0;
//Timer1
//Prescaler 1:1; TMR1
void InitTimer1() {
T1CON = 0x01;
TMR1IF_bit = 0;
TMR1H = timer_reload_value >> 8;
TMR1L = timer_reload_value;
TMR1IE_bit = 1;
}
void Interrupt() {
if((INT0IE_bit) && (INT0IF_bit)) {
INT0IF_bit = 0;
//INT0IE_bit = 0;
scr_select_counter = 0;
InitTimer1();
}
else if((INT1IE_bit) && (INT1IF_bit)) {
INT1IF_bit = 0;
//INT1IE_bit = 0;
scr_select_counter = 1;
InitTimer1();
}
else if((INT2IE_bit) && (INT2IF_bit)) {
INT2IF_bit = 0;
//INT2IE_bit = 0;
scr_select_counter = 2;
InitTimer1();
}
if((TMR1IE_bit) && (TMR1IF_bit)) {
TMR1IE_bit = 0;
TMR1IF_bit = 0;
//Enter your code here
switch(scr_select_counter) {
case PHASE_R:
R_Phase_SCR_Gate_Trigger = 1;
Delay_us(100);
R_Phase_SCR_Gate_Trigger = 0;
//INT1IE_bit = 1;
break;
case PHASE_Y:
Y_Phase_SCR_Gate_Trigger = 1;
Delay_us(100);
Y_Phase_SCR_Gate_Trigger = 0;
//INT2IE_bit = 1;
break;
case PHASE_B:
B_Phase_SCR_Gate_Trigger = 1;
Delay_us(100);
B_Phase_SCR_Gate_Trigger = 0;
//INT0IE_bit = 1;
break;
};
}
}
void CustomChar(char pos_row, char pos_char) {
char i;
Lcd_Cmd(64);
for(i = 0; i <= 7; i++)
Lcd_Chr_CP(character[i]);
Lcd_Chr(pos_row, pos_char, 0);
}
char *CopyConst2Ram(char * dest, const code char *src) {
char *d;
d = dest;
for(;*dest++ = *src++;);
return d;
}
void main() {
CM1CON0 = 0x00;
CM2CON0 = 0x00;
SLRCON = 0x00;
ADCON1 = 0x80;
ADCON2 = 0b10110101;
ANSELA = 0x01;
ANSELB = 0x00;
ANSELC = 0x00;
ANSELD = 0x00;
ANSELE = 0x00;
TRISA = 0x01;
TRISB = 0x07;
TRISC = 0x00;
TRISD = 0x00;
TRISE = 0x00;
PORTA = 0x00;
PORTB = 0x00;
PORTC = 0x00;
PORTD = 0x00;
PORTE = 0x00;
LATA = 0x00;
LATB = 0x00;
LATC = 0x00;
LATD = 0x00;
LATE = 0x00;
Delay_ms(200);
LCD_Init();
LCD_Cmd(_LCD_CURSOR_OFF);
LCD_Cmd(_LCD_CLEAR);
LCD_Out(1,1,CopyConst2Ram(txt, txt1));
LCD_Out(2,1,CopyConst2Ram(txt, txt2));
timer_tick_period = 1.0 / (fosc / 4.0 / timer_prescalar);
//mains ac period
period = 1.0 / mains_frequency;
//duration for 180 degrees
duration_for_half_wave_of_ac = period / 2.0;
//**** duration_for_120_degrees = period / 3.0;
//for raw adc value = 0 we have to get scr firing delay = 0 sec and
//for raw adc value 1023 we have to get scr firing delay of 9.7ms
//we don't take 10ms because there is a 200us delay after zero cross
//and before the INT pin goes low and another 100us delay after INT pin
//goes low and SCR fires for scr firing delay = 0
//so, we subtract 300us from 10ms to get 0.0097 sec
//if raw adc value is 1023 then we have to get scr firing delay of 0.0097
//sec and so we have to use equation,
//scr_firing_delay_in_seconds = raw_adc_value * 0.0097 / 1023.0
//so, the factor for multiplying with raw adc value is 0.0097 /1023.0
// which is (duration_for_half_wave_of_ac - minimum_gate_trigger_delay) / 1023.0
//adc_factor = (duration_for_half_wave_of_ac - minimum_gate_trigger_delay) / 1023.0;
////adc_factor = (duration_for_120_degrees - minimum_gate_trigger_delay) / 1023.0;
adc_factor = (duration_for_half_wave_of_ac - minimum_gate_trigger_delay) / 1023.0;
INTEDG0_bit = 0;
INT0IF_bit = 0;
INT0IE_bit = 1;
INTEDG1_bit = 0;
INT1IF_bit = 0;
INT1IE_bit = 1;
INTEDG2_bit = 0;
INT2IF_bit = 0;
INT2IE_bit = 1;
PEIE_bit = 1;
GIE_bit = 1;
while(1) {
raw_adc_value = (unsigned int)ADC_Read(0);
Delay_ms(1);
if(previous_raw_adc_value != raw_adc_value) {
//to get scr firing delay of 0 to 9.97ms (10ms - 300us, 180 degree) for 0 to
//1023 raw adc //value
//**** to get scr firing delay of 0 to 6.6467ms (6.67ms - 300us, 120 degrees)
//1023 raw adc //value
scr_firing_delay_in_seconds = (double)raw_adc_value * adc_factor;
//only if adc value is greater than 0 then calculate the timer
//reload value which is used in ISR to get the required scr
//firing delay
////if(raw_adc_value > 0) {
timer_reload_value = (unsigned int)(timer_resolution -
(scr_firing_delay_in_seconds
/ timer_tick_period));
////}
//as mentioned above there is 300us delay and for half of AC
//period that is for 10ms, angle is 180 degrees, so for 300us
//it is 5.4 degrees
//so, to get scr firing angle between 5.4 degrees and (180 - 5.4)
//degrees we use below equation
//eg: if scr_firing_delay_in_seconds = 0 we get scr_firing_angle
//= 5.4 degrees
//if scr_firing_angle_in_seconds = 0.0097 then we get
//scr_firing_angle = 174.6 degrees
//due to initial 300us delay the scr can only conduct for max
//174.6 degrees
scr_firing_angle = 18000 * scr_firing_delay_in_seconds + 5.4;
//finally scr conduction angle is calculated from below equation
//eg: if scr firing angle is 5.4 degrees then scr conduction angle
//is 180 - 5.4 = 174.6 degrees
scr_conduction_angle = 180.0 - scr_firing_angle;
//the scr firing angle floating point value is converted to
//fixed length string with fixed lenght = 5
FloatToStr_FixLen(scr_firing_angle, txt, 5);
//the string is printed on LCD line 1
LCD_Out(1,10,txt);
//the degree symbol is printed on LCD at required position
CustomChar(1,15);
//the scr conduction angle floating point value is converted to
//fixed length string with fixed lenght = 5
FloatToStr_FixLen(scr_conduction_angle, txt, 5);
//the string is printed on LCD line 2
LCD_Out(2,10,txt);
//the degree symbol is printed on LCD at required position
CustomChar(2,15);
//this is to make sure that this block of code is executed only
//if adc value has changed
previous_raw_adc_value = raw_adc_value;
}
}
} |