Sine wave power inverter

[pramodsinha]

hi saugata
i need three phase sine wave generation circuit i have the full knowledge of how to drive msosfet and igbt in three phase configuration.
pramod

Hi Suded,

If I have understood right then you are suggesting that I build a hf oscillator around the SG3524 then use the PIC18F452 to supply the closed loop control voltage to the SG3524 (the PIC HWPWM acts as a DAC).

Now the issues are,

1. I already have two HWPWMs built into the PIC

2. The SG3524 allows dead-time programming through a simple resistor but while switching phases I again need a few logic chips to get it done.

3. I have designed the software around interrupts. I am doing an AD-Oversampling which bruce, tim and melanie suggested in the MELAB forum.For a pulse by pulse current limiting (so that the MOSFETs don't blow up) I am using a comparator to sense the current and generating an INT to turn off the MOSFET drives.(Heh! Heh! a digital copy of the SG3524 current limit scheme).
So why use the SG3524 as the ad-sample and dac conversion will add up to the loop error.

The only thing that concerns me is the THD introduced while driving inductive loads as my routines are not so fast to correct that in realtime. I tried but the results are erratic (thats because of lack of knowledge from my side). The PIC is running at 40MHz (10MIPS,10MHz@HSPLL). Now I am concentrating on reducing noise on the AD line, using interrupt based AD (PBP tends to waste time while doing AD).

BTW can anybody shed some light on the time consumed by LCDroutines. Because while processing interrupts with PBP I found glitches while the LCD was being updated.

Thanks to psdayama and doctor for the links. As far as PSPICE goes I am not sure whether my knowledge is sufficient to handle them (I don't have an engineering background)

Regards
Sougata

[pramodsinha]

i went through all options to make a sine wave inverter but it was defficult to make it in basic language.

[peterdeco1]

Attached is a sinewave generator from PIC outputs going high 1 at a time. Hope this helps.

[sougata]

Hi Pramod,

Microchip has a very comprehensive appnote AN843 that demonstrates how to use a PIC18Fxxx to generate three phase PWM signals. Since the basic 18F series has onto two hardware PWMs inbuilt you have to rely on software PWM for the third. Definitely not through the Pbasic PWM function. As you are aware that designing a sine wave inverter entirely in PIC Basic is difficult (due to limited interrupt capabilities and latency issues) you have to structure your software around assembly. I am attaching a pbp source code alongwith the sinetable and firing concept. It may help. I have heavily commented the code to facilitate understanding.Let me know if it helps you out.I am sorry due professional restriction I cannot give you the entire code. But we can communicate through this forum so that other users of this forum may also benefit.

Microchip makes some special PICs in the PIC18F2331/4331 series which have an enhanced PWM hardware that supports programmable dead time. It also includes 3 or more PWMs. Coupled to that are ADCs which have a much lower conversion time. This would give you the lowest THD (tighter and faster correction loop) and still have enough room left for some housekeeping such as pulse by pulse overload limiting, overtemperature protection, line monitor, battery monitor, serial com, etc.



By the way you mentioned that you are well familier with MOSFET drive techniques.Could you enlighten me on that. May be this forum is not the right place (off topic). You can drop me a private message so that I can give you my email id.

I have desingned the MOSFET driver on a totem-pole circuitry. However I am not satisfied with the slope.I believe a steeper slope would effectively reduce switching losses. I tried MOSFET drivers from Microchip too but they blew up. Possibly due to latch up or improper grounding of the PCB traces. They are costly too here in Kolkata. Photovoltaic drivers with active discharge is not available here in Kolkata. Also I need to understand why my MOSFETs blew up during initial testing phase while the inverter was unloaded.

regards

Sougata

[MKA341]

hi

can you tell me about pic basic?

Manish

[T.Jackson]

hi

can you tell me about pic basic?

Manish

In a nut shell - PIC Basic is a true compiled, mature, robust, quick & easy no fuss solution for all your PIC-based embedded system needs.

In fact, so easy-to-use, if you can't write a program in it, programming
just isn't for you. It just couldn't get any simpler.

Trent Jackson

[MKA341]

where can i get pic basic software?

[wire042]

Please am having problem with my inverter that is posted on this forum on page 5.

[iw2fvo]

No chance to have something working on this forum expecially for the inverters or MPPT .
It should be an homebrewers or do it youself forum... but it is not.
Ambrogio