phase angle contoller

I am new to this forum but someone told me that I may be able to achieve what I want to do using a arduino. what I want to do is control a phase angle controller http://www.crydom.com/en/Products/Catalog/m_cpc.pdf with the software on the arduino. the controller operates with 0-5v ie 1v = 20% power and 5v = 100% power. can anyone tell me if this is possible using software coding and the output on the arduino.

What would this software be doing, or how would you be controlling the Arduino exactly?

An arduino Nano with a MAX5468 digital pot would do the job IMHO

The software will be using 2 inputs from current transformers one will be connected to my meter tails and the other from the output from my solar pv, this will then calc the unused power and use it to power my immersion heater. so if there is no load demand on the house there is high power going through the controller and if the demand on the house power goes up the power through the controller drops.Hope that is a bit clearer to what I want do achieve.

This sounds quite complex and I don't fully understand how it's intended to work. I rather imagined that these systems simply produced mains voltage AC correctly phased with the incoming mains AC, and connected directly to the mains. So any current provided by the solar array reduce the current drawn from the mains; if the solar output actually exceeded your total power consumption then this would result in 'negative current' at the meter i.e. your solar array is feeding the mains. In this simplistic view, there's no need to explicitly measure any of the current flows; simply connect everything together and the net supply/return goes through the meter. Does it need to be any more complex than that?

That is correct in the uk you get the feed in tarriff which is 43p for what you generate even if you use the power during the day you still get the tarriff for what you generate. You also get 3.5p on 50% of what you generate from your electricity provider, even if you use all of the electricity you generate during the day you still get 50% of what you generate. so if i use the surplus power that I am not using to heat my water it will save me on my gas bill which i currently use to heat my water. doing it this way will give me free hot water.

madmurg: That is correct in the uk you get the feed in tarriff which is 43p

Now 21p for new signups.

madmurg: so if i use the surplus power that I am not using to heat my water it will save me on my gas bill which i currently use to heat my water. doing it this way will give me free hot water.

Are you sure? How much gas would you use to heat a tank of water? There's a fair chance it would be cheaper to heat the water with gas and sell the electric from the PV back to the grid for more than the gas would cost. Also what happens when you don;t want a tank of water, you're not really saving gas, you're just wasting the electricity produced by the PV for no reason. Suppose you could factor this in with timers and stats in the right places.

Also, as above, are you sure you want a phase angle sensor? What meters have you got on the PV? Some of them have inputs and outputs for just this sort of thing.

Lurch:

madmurg: That is correct in the uk you get the feed in tarriff which is 43p

Now 21p for new signups.

madmurg: so if i use the surplus power that I am not using to heat my water it will save me on my gas bill which i currently use to heat my water. doing it this way will give me free hot water.

Are you sure? How much gas would you use to heat a tank of water? There's a fair chance it would be cheaper to heat the water with gas and sell the electric from the PV back to the grid for more than the gas would cost. Also what happens when you don;t want a tank of water, you're not really saving gas, you're just wasting the electricity produced by the PV for no reason. Suppose you could factor this in with timers and stats in the right places.

Also, as above, are you sure you want a phase angle sensor? What meters have you got on the PV? Some of them have inputs and outputs for just this sort of thing.

I cant sell the power back to the electricity company as I said before I get 3.5p per kwh on 50% of what I generate even if I use the power or not. so not using all of the power I generate does not make sense.

Well I'm suitably lost in this regeneration scheme then.

Am I correct in thinking you produce electricity using the PV and then sell it back to the grid for 43p per unit?

If so, why would you have anything 'spare'? Surely you just sell them what you produce, what goes to waste?

Lurch: Well I'm suitably lost in this regeneration scheme then.

Am I correct in thinking you produce electricity using the PV and then sell it back to the grid for 43p per unit?

If so, why would you have anything 'spare'? Surely you just sell them what you produce, what goes to waste?

The 43p is from the government fit payment on all the power you generate, even if you use all the power you generate you still get 43p on the total. The 3.5p is from the electricity company and you get 50% on what you generate, so if I generate 2000 kwh per year and I use 2000 kwh I still get paid 1000 kwh at 3.5p pluse I get 2000 kwh at 43p. Hope that is clearer for you.

So basically you get paid for what comes out of the inverter regardless of where it goes?

I see what you're doing now if the above is true. If so, back to the original query, is there any pulse output on the meter of any variety? If not, is the phase angle reading what you need, don't you just need some sort of comparator? What inverter do you have? Some have quite a few bolt on options and\or built in outputs. Might be able to save quite a bit of external hardware and data processing if you have the right kit in already.

Lurch: So basically you get paid for what comes out of the inverter regardless of where it goes?

I see what you're doing now if the above is true. If so, back to the original query, is there any pulse output on the meter of any variety? If not, is the phase angle reading what you need, don't you just need some sort of comparator? What inverter do you have? Some have quite a few bolt on options and\or built in outputs. Might be able to save quite a bit of external hardware and data processing if you have the right kit in already.

There are no other terminals on the inverter. It is a sunny boy 3400 but this would not help anyway as I need to monitor the load the house is taking and also the output the inverter is producing. For example load of house=400w and pv is producing 2kw I then have 1.6 kw surplus I want to then use this 1.6 kw to power my immersion heater.

I'm familiar with the stupid UK feed in tariff system that pays you to consume power that your own system generates, and I guess you may as well exploit it. What you suggest sounds feasible. Here are a few observations:

1. The controller needs a permanent 8v to 32v supply. I guess you will use a 9v wall wart and power the Arduino from that too.

2. The enable input on that controller is just about OK fed from 5v from an Arduino pin.

3. The phase control needs 0.8v to 5v and has 20k input resistance. You can drive that from an Arduino PWM pin using a resistor (say 220 ohms) and smoothing capacitor. Increase the PWM frequency to allow you to use a smaller capacitor.

4. The phase angle control will mean that the current waveform in the current transformers is quite complicated. You will have to sample both the current and the voltage many times per mains cycle and do some maths to work out the power being passed.

5. An Arduino Uno consumes around 40mA and the wall wart will consume some power too. Maybe a few watts in total, even at night and on dull days when there is no surplus power. But I guess this won't reduce your profit very much.

dc42:
I’m familiar with the stupid UK feed in tariff system that pays you to consume power that your own system generates, and I guess you may as well exploit it. What you suggest sounds feasible. Here are a few observations:

1. The controller needs a permanent 8v to 32v supply. I guess you will use a 9v wall wart and power the Arduino from that too.

2. The enable input on that controller is just about OK fed from 5v from an Arduino pin.

3. The phase control needs 0.8v to 5v and has 20k input resistance. You can drive that from an Arduino PWM pin using a resistor (say 220 ohms) and smoothing capacitor. Increase the PWM frequency to allow you to use a smaller capacitor.

4. The phase angle control will mean that the current waveform in the current transformers is quite complicated. You will have to sample both the current and the voltage many times per mains cycle and do some maths to work out the power being passed.

5. An Arduino Uno consumes around 40mA and the wall wart will consume some power too. Maybe a few watts in total, even at night and on dull days when there is no surplus power. But I guess this won’t reduce your profit very much.

Thanks that sound good to me I know how to do the calcs for the ct comparisons and put it to code but I am not sure on the code to control the phase control, any help here would be apreciated.

madmurg: Thanks that sound good to me I know how to do the calcs for the ct comparisons and put it to code but I am not sure on the code to control the phase control, any help here would be apreciated.

If you use the smoothed output from a pwm pin as I suggested, you just need to use analogWrite to write a value between 41 (to get the minimum 0.8v input to the controller, i.e. minimum power) to 255 (to get very nearly 5v, i.e. full power). To determine what value you need to equalise the generated and consumed power, I suggest a PID controller algorithm.

dc42:

madmurg: Thanks that sound good to me I know how to do the calcs for the ct comparisons and put it to code but I am not sure on the code to control the phase control, any help here would be apreciated.

If you use the smoothed output from a pwm pin as I suggested, you just need to use analogWrite to write a value between 41 (to get the minimum 0.8v input to the controller, i.e. minimum power) to 255 (to get very nearly 5v, i.e. full power). To determine what value you need to equalise the generated and consumed power, I suggest a PID controller algorithm.

Thanks for you help. I will now order the kit now I am sure it will work ok.

I knew the UK subsidy situation was absurd, but I didn't realise it was that absurd. So if you rig up a solar array and just dump the power through a resister, you get PAID to do that? And there is no financial incentive to you, to returning that power back to the grid? Wow, that sounds extraordinary!

Setting that aside, surely this scheme must already incorporate some scheme for measuring power (a) produced and (b) consumed? So, surely you just connect the solar array in to the appropriate meter (s) and wait for the cash to roll in? I'm still not seeing where you need to do anything clever.

PeterH: I knew the UK subsidy situation was absurd, but I didn't realise it was that absurd. So if you rig up a solar array and just dump the power through a resister, you get PAID to do that? And there is no financial incentive to you, to returning that power back to the grid? Wow, that sounds extraordinary!

Setting that aside, surely this scheme must already incorporate some scheme for measuring power (a) produced and (b) consumed? So, surely you just connect the solar array in to the appropriate meter (s) and wait for the cash to roll in? I'm still not seeing where you need to do anything clever.

When you have the solar array installed you can have the option to fit an export meter. You will then get paid 3.5 p for every kwh you put back into the grid. This makes sense to have fitted if there is no one at home during the day. But as we work from home we are better off to use as much of the solar power we can and claim 50% of the yearly power we generate.

As to you second question the inverter only gives a reading of the power produced. There is also no connectivity to my inverter so the easiest option for me is to use ct's on the house load and the pv supply. Maybe using one ct will work by passing the load and supply through but in separate directions thus giving me the result of surplus power. I'll have to look into that to see if ct's work that way.

Have you had any success with this project?

Andy.