Sine wave power inverter

[babalola]

Hi Das,

The e(k+1) is the present error
e(k) > past error
u(k+1)> present output of the pi controller
u(k) > past output of the controller
the above are digital parameters of the pi controller and in the course of getting these parameter there is alway need for sampling time (T), the propotional gain of the controller Kp and the zero placement of the controller which is WI
INTERGRAL GAIN KI=Kp*WI
therefore A=Kp(WI*T -1)
while B=Kp

Example if kp=0.04 and WI =3140rad/sec SAMPLING TIME OF 10us

KI=188.4
A=0.04(3140*10US-1)
B=0.04

Remember in PI controller proportional looks at present error while intergral looks at past errors

Regards,
babalola.

[samrulezzz]

hi Sougata


Actly my guide provided me with the circuits....

Ive attached few interfacing circuits....
hope this is wot u requested....

[sougata]

Dear Sam,

These are the interfacing circuit to do the following in order of your doc.

1. Mains Sense Circuit: Comes from a small step down transformer. The rectified DC voltage is an average representation of the Mains Input Voltage. AN0 is used to sample this pin and decide the status of the mains input. That is within range or outside range. If out of range switches to inverter mode. While in inverter mode used to sense mains restore condition. So this is part of a periodic ADC routine.

2. Battery Sensing Circuit: Used to sense the battery voltage for deep discharge cut-off and charging state change (Boost/Trickle/Equalize). So this is also used in both the inverter/mains-standby mode. Used AN1

3. Charger Circuit: An inverting amplifier. Note that the same shunt (generally in the low side negative battery terminal) is used to measure battery charge and discharge current. The ADC onbaord 16F72 is 8 bit. If a signed AD was performed by offsetting the signal then you loose one more bit and have 7 bit AD for the current sense. So to channels are used with two amplifiers. This is negative battery dischargei.e., current is being put into the battery, thus the inverting amplifier. Phew......

This goes to AN4 and is used only when charging the battery.

4. Load Sensing Circuit : Same as above but for discharge. So a non-inverting amplifier. connected to AN2. Used for overload protection.

5. Output Voltage Sensing: This either comes from a sense winding on the inverter transformer or a small step down transformer (better) connected to the filtered output of the inverter output. This is the voltage feedback for correcting voltage under different load/battery condition. Average DC represents the average output voltage. No in cycle distortion correction possible. (Not within the scope of 16F @ 20MHz, Needs a 18F @ 40MHz)

6. Power Supply Circuit : Your PIC runs on 5 Volts.

7. Sync Pulse Circuit: PORTB.0 INT based zero cross over sensing. Can measure line frequency. Can detect abrupt mains failure (UPS mode). Can do phase angle control on charge circuit. Can detect mains restore. Important for grid connected inverter, where you need to sync your timebase to the mains.


Assuming the above circuits have been ripped from common inverter design prevalent in India. I don't know why people are still stuck with the 16F72 when there are newer introduction like PIC18F1330. I could upgrade my design. Who would buy it ??

This design is far from complete. You need to design the driver stages. Then decide on the software. In India most designs run on software PWM using the compare module. I don't know why ? But they are commercially successful. .... Well I am not.


P.S. - Sorry Sam, I cannot make the code public. (People will come to know about my bad programming skill). I only dream of making an open source sinewave inverter, in PBP. Can't find time. Cause I need to come up with a fresh new design to avoid any legal obligations on my old design.

[samrulezzz]

HI Sougata

Thanking u for takin time of your busy shchedule to explain each of the circuits........

i ve also got the mosfet drive circuits designs......but could not attach as i dont have a soft copy of the designs.....

the design is all but complete for the software code....which i was wanting help on....
actly was hopin u wud help me out on the code.....


but I fully understand ur situation regarding leagal issues......so if u cud help me in some other way like

if u knw any1 among ur frenz who can help me write the code.....

or u have any bits n pieces of codes u found on net or something dat mite help me


plz let me knw if u can direct me to some other person who can help me with the code.....i don mind paying him his fees for the help in the code....

hopin u can help me out in some way

sam
[email protected]

[sougata]

plz let me knw if u can direct me to some other person who can help me with the code.....i don mind paying him his fees for the help in the code....

hopin u can help me out in some way

sam
[email protected]

If you surf on the net or follow EFY magazine you will find that there are people who are distributing .HEX files for as less as Rs.20,000.00 (USD$ 400) but you will get zero support as far as an academic project report is concerned. I have no idea whether anybody will give you source code. Most of them don't have it. So asking for paid support may be well exceed the scope of your project.

I personally feel that you should start writing your own code and the forum would help. A student project need not be perfect, but should be a proof of concept. So better start with the sine generation. Open loop-no feedback and then achieve other milestones as per time frame of the project.

Where are you located by the way.

[samrulezzz]

hi sougata

ya wot u tell is true....no1 gives the source code normally....

i ve got bits n pieces of codes wen i surfed....
now trying to write a code on my own....
hoping it turns out gud



me located in mangalore karnataka state

[sougata]

Hi,

One suggestion. Do not rely on PBP while doing multiplication inside your sine lookup code. It takes many MCU cycles. Google for fixed latency multiply on PIC16. It takes more code space but timing is within control.

Good Luck