build your own Grid Tie inverter limiter - using a Ted MTU

sash

Member
Hi there,
 
if anynone wants to build a GTI LIMITER or need to shift   load around - - the  accuracy with 1000 watt inverter should be   about =/-4 watt  as itt is 256 steps .  use it to shift load around  say when one GTI inverter  is  over producing it shifts load to another  GTI   as for most GTI  the max might be  listed as one number  but it is better to run them at 80% of max output... or if you live in an area that  does not allow roll back of power meters. this will adjust the power out put of your GTI to out put to match your meter..   the code might be still a little buggy  but is working well for my purpose. I will post updates to sketch as I improve it  - if you use this --- please post back any modification you  made  for other people  to benifit -- Thank you
 
there are a couple ways of building it you could use  3 -SCT-013-000, but i choose to use  1  and 1  ted MTU.  as it is much easier to build that way.. as 3 SCT-013-000 had a significant delay
 
 
parts:
1 TED MTU                            $20 and up on ebay
1 - Arduino                             $5 on ebay
1 - I2C LCD                           $5 on ebay
1- ad5206 digital pot  (100k)  $8 digikey
1-SCT-013-000  (100amp)     $8 on ebay
6 - 20 amp DC10-60v PVM     $7 on ebay  ( or bigger ones thes on are the right voltage at the pot 5v- other ones ar 7 volt
                                                   - but you  can step  down with an led or a resistors)
1-33ohm resistors
2-10k resisters
1- 10uf cap
 
reference:
http://www.homautomation.org/2013/09/17/current-monitoring-with-non-invasive-sensor-and-arduino/
https://www.arduino.cc/en/Tutorial/DigitalPotControl
http://cocoontech.com/forums/topic/25589-very-cheap-ted-1001-house-power-monitors-and-possible-hacking/page-6
 
modify the mtu - one wire to ground and one wire to pin one  on TDA5051A rx out - i used the  a trace from pin one and used a open spot near the chip  scatch it clean and attached it there  as it is also  the ground for digital RX/TX for the chip
 
here is my sketch based on one  1 - SCT-013-000 and 1 - ted MTU   basically   connect the ted as normal  to your fuse panel and put the  SCT-013-000 on the lin in from your  solar equipment  GTI  if yo have more then  one GTI going to multiple fuses  then  hopefully it is on a sub panel then you just hook it one to one of the lines  coming from subpanel to the main fuse box..

#include <stdio.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <EmonLib.h>
// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

const byte numBytes = 32;
const int slaveSelectPin = 10;
EnergyMonitor emon1;

byte receivedBytes[numBytes];
byte numReceived = 0;
int cnt = 0;
float kw = 0;
float volts = 124;
float stp = 255;
float levelper = 100; // percentage of step for pot
float invpb = 100; // inverter probable max output
float inv2 = 100; // inverter calulation value
float inv3 = 100; // inverter calculation value
float diff = 100; // pot comparison diff
float level1 = 100; // post level calculation
float inverter = 1;
float kw1 =0;
float le=127; // level saved condition
int rl1=127; // rlevel saved condtion

int level=127; // main pot control for PWM
int rlevel=127; // if you need reverse pot direction of PWM

boolean newData = false;

void setup() {
Serial.begin(1200);
Serial.println("<Arduino is ready>");
Serial.println(level);
// Serial.begin(1200);
lcd.begin();
pinMode(slaveSelectPin, OUTPUT);
SPI.begin();

//emon1.voltage(2, 234.26, 1.7);
// Voltage:input pin, calibration,phase_shift
emon1.current(1, 111.1);
// Current: input pin, calibration.


}

void loop() {
recvBytesWithStartEndMarkers();
showNewData();
// output();
// potset();
}

void recvBytesWithStartEndMarkers() {
static boolean recvInProgress = false;
static byte ndx = 0;
byte startMarker = 0xAA;
byte endMarker = 0xAA;
byte rb;


while (Serial.available() > 0 && newData == false) {
rb = Serial.read();

if (recvInProgress == true) {

if (rb != endMarker) {
receivedBytes[ndx] = rb;
ndx++;
cnt = ndx;
if (ndx >= numBytes) {
ndx = numBytes - 1;


}
}
else {
receivedBytes[ndx] = '\0'; // terminate the string
recvInProgress = false;
numReceived = ndx; // save the number for use when printing
ndx = 0;
newData = true;
}
}

else if (rb == startMarker) {
recvInProgress = true;

}
}
}

void showNewData() {
if (newData == true) {
Serial.print("This just in ... ");
for (byte n = 0; n < numReceived; n++) {
Serial.print(receivedBytes[n], HEX);
Serial.print(' ');
}
Serial.println();
showGroupsOfBytes();
newData = false;

}
}

void showGroupsOfBytes() {
if ( receivedBytes[0]==0x4E ) { // change this to match your MTU it - it will display in serial print
if (cnt == 10) {
byte j = ~receivedBytes[6];
byte k = ~receivedBytes[7];
byte m = ~receivedBytes[3];
byte r = ~receivedBytes[4];


double voltage = 0;
double power = 0;

voltage = ( k<< 8) | j;
voltage= (123.6 + (voltage - 27620) / 85 * 0.4);

volts=voltage;

power = (r<<8) + m;
power = 1.19 + 0.84 * ((power - 288) / 204);
kw = power;

lcd.clear();
lcd.setCursor(0,0);
lcd.print("volts ");
lcd.print(voltage);
lcd.setCursor(1,1);
lcd.print("kw ");
lcd.print(power);



}
}

cnt = 0;
double Irms = emon1.calcIrms(1480); // Calculate Irms only
/* emon1.calcVI(20,2000);
// Calculate all. No.of half wavelengths (crossings), time-out
emon1.serialprint();
// Print out all variables (realpower, apparent power,
// Vrms,Irms, power factor)

//float realPower = emon1.realPower;
//extract Real Power into variable
// float apparentPower = emon1.apparentPower;
//extract Apparent Power into variable
//float powerFActor = emon1.powerFactor;
//extract Power Factor into Variable
float supplyVoltage = emon1.Vrms;
//extract Vrms into Variable
float Irms = emon1.Irms;
*/ //extract Irms into Variable

inverter = ((Irms*volts)/1000); // calculates GTI output
Serial.println("kw");
Serial.println(kw);
Serial.print(level);

if(kw > 0){
if(level == 255){
level = (level-2);
}
Serial.println("Inverter - positive value");
Serial.println(inverter);
Serial.println( "data output");
levelper=(level+1);
Serial.println(levelper);
levelper=(levelper/256);
Serial.println(levelper);
invpb = (inverter/levelper);
Serial.println(invpb);
inv2 = (invpb+kw);
Serial.println(inv2);
inv3 = (inv2/invpb);
Serial.println(inv3);
diff = (1-inv3);
Serial.println(diff);
diff = abs(diff);
Serial.println(diff);
level1 = (level + 1);
Serial.println(level1);

diff= (256*diff);
Serial.println(diff);

level1 = (level1 + diff);
Serial.println(level1);
kw1= (1 - kw);
Serial.println(" ");
Serial.println(kw1);



if (level1 >= 255) {
level= 0;
rlevel = 255;
}else{
level = (level1 - 2);
rlevel = (255 - level);

}
}

if(kw < 0){
Serial.print(rlevel);
if(rlevel == 255){
rlevel= (rlevel-1);
}
Serial.println("Inverter negative value");
Serial.println(inverter);
Serial.print(rlevel);
Serial.println( "data output");
levelper=(rlevel+1);
Serial.println(levelper);
levelper=(levelper/256);
Serial.println(levelper);
invpb = (inverter/levelper);
Serial.println(invpb);
inv2 = (invpb+kw);
Serial.println(inv2);
inv3 = (inv2/invpb);
Serial.println(inv3);
diff = (1-inv3);
Serial.println(diff);
// diff = abs(diff);
Serial.println(diff);
level1 = (rlevel + 1);
Serial.println(level1);

diff= (256*diff);
Serial.println(diff);

level1 = (level1 + diff);
Serial.println(level1);
kw1= (1 - kw);
Serial.println(" ");
Serial.println(kw1);



if (level1 >= 255) {
rlevel= 0;
level = 255;
}else{
rlevel = (level1 - 1);
level = (255 - rlevel);

}
}


if(kw < 0){

for (int scan = 0; scan < 1 ; scan++) {
digitalPotWrite(1, level);
Serial.print("Hchannel ");
Serial.println(level);

// delay(10);
digitalPotWrite(2, level);
// Serial.println("Hchanne2");
// Serial.println(level);
// Serial.println(2);
//delay(10);
digitalPotWrite(3, level);
// Serial.println("Hchanne3");
// Serial.println(level);
// Serial.println(3);
//delay(10);
digitalPotWrite(4, rlevel);
// Serial.println("Hchanne4");
// Serial.println(rlevel);
//Serial.println(4);
//delay(10);
digitalPotWrite(5, rlevel);
// Serial.println("Hchanne5");
// Serial.println(rlevel);
// Serial.println(5);
//delay(10);
digitalPotWrite(6, rlevel);
Serial.print("Hchannel6 ");
Serial.println(rlevel);

// Serial.println(Irms);
//level=level+1;


//delay(10);

}
}
if(kw>0)
{
//if(level>=0)
for (int scan = 0; scan < 1; scan++) {
{
digitalPotWrite(1, level);
Serial.print("lchannel ");
Serial.println(level);

// delay(10);
digitalPotWrite(2, level);
// Serial.println("lchanne2");
// Serial.println(level);
// Serial.println(2);
//delay(10);
digitalPotWrite(3, level);
// Serial.println("lchanne3");
// Serial.println(level);
// Serial.println(3);
//delay(10);
digitalPotWrite(4, rlevel);
// Serial.println("lchanne4");
// Serial.println(rlevel);
// Serial.println(4);
// delay(10);
digitalPotWrite(5, rlevel);
// Serial.println("lchanne5");
// Serial.println(rlevel);
// Serial.println(5);
// delay(10);
digitalPotWrite(6, rlevel);
Serial.print("lchannel6 ");
Serial.println(rlevel);

//Serial.println(Irms);
// level=level-1;

}

}


}

Serial.print("level ");
Serial.println(level);
Serial.print("rlevel ");
Serial.println(rlevel);
Serial.println(" ");
}


void digitalPotWrite(int address, int value) {
// take the SS pin low to select the chip:
digitalWrite(slaveSelectPin, LOW);
// send in the address and value via SPI:
SPI.transfer(address);
SPI.transfer(value);
// take the SS pin high to de-select the chip:
digitalWrite(slaveSelectPin, HIGH);



}

good luck
have fun :)
 
 

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your welcome and my pleasure... 
 
but i see i forgot to mention, you place the the PWM on the dc side of the  GTI either at  the solar panels or right before the inverters .  this one can control  up to 6 pwm  or  6 1000w GTI  ... if you pair in parallel or series   a PWM  2 or 3 PWM to one digital pot channel  you can go much much  bigger.. or  just buy the 90v 60 amp pWM off ebay.  but these particular  PWM.. work the best as  they are  run exactly in the sweet spot of the AD2506 (100k) the other ones run a bit hot   and   most did not zero out..   if you need more control you can add in another ad2506 chip and handle 12 channels or more
 
here a basic image of what it looks like and how things  hook up,  I connected  the digital pots to Rj45 ports  then use regular solid wire cat5e cable and higher to control the pots, each port handles 2 pots with 2 spare wires for future use.. it  work fine over 50 feet of  cat5 cable as that what i tested so far.. still waiting for a couple more  PWM and a I2C lcd 4 line to come in. as i did not want to cut the box until I make sure it fits..   they be here sometimes in early feb..
 
also i noticed that my code above has an error  i list digital channels 1-6  when it should be  0-5  just edit above and you should have all channels working properly.
 
 
 

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This is great good job and I want to do this but the cheapest I can find a TED for is $220 on eBay at the moment , any chance you could change the code a bit to exclude the TED mtu this would make it cheaper I think to build and less dependent on TED
 
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