Feedback controlling method understand

[thannara123]

In sinewave  inverter like products ,How the feedback control Works ?

The feedback sinewave signal properly shaped and connected to the ADC of the controller .

Is the ADC reads, the first Half cyle and calculate the RMS of the signal . Then correct the PWM switching to maintain the voltage stable?
 
                                           Or
is the instantenious value of the ADC reads is correct the PWM to maintain the voltage stable ?

The first one takes more time in 50 Hz system it takes 10 milli second .

what is the normal type is there any other logic ?

how the settiling time / Response time ?

[Andy Chee]

You need to analyse the inverter in two stages:

1) boost 12V DC to 340V DC
2) convert 340V DC to 240V AC 50Hz

The main feedback loop occurs in stage 1) and usually operates a high frequency PWM push-pull transformer, maybe 30-50kHz.  The ADC will read the DC voltage and regulate the 340V DC output.  This stage also contains current limiting.

A second, H-bridge PWM controller in stage 2) then converts the 340V DC to 240V 50Hz AC.  This second H-bridge PWM also works at high frequency.  There is no feedback in this stage, this stage is only for sinewave shape generation.

[thannara123]

Sir , Its not a two stage one ,it is low frequency transformer based

[Johnny B Good]

 I'm pretty sure these inverters use a similar technique to that employed by inverter genset designs where a 3 phase permanent magnet alternator is directly driven by a small ICE whose speed can be varied according to the load.

 For European / UK service, the alternator typically outputs a three phase 350 to 380 peak amplitude sine (or possibly even trapezoidal) voltage around a frequency ranging from a low of 300 to a maximum of 450Hz or so which is fullwave rectified and smoothed to a 350 to 380 vdc level.

 The controller simply adjusts the ICE's rpm to maintain the voltage level within this range which feeds what is essentially a high voltage "digital" bridged output amplifier being driven by a fixed low level (a volt or two?) xtal controlled 50Hz sine wave reference. Being an amplifier it simply raises that sine wave reference voltage by a fixed gain to the required 230vac 50 Hz output voltage.

 I should think that the inverter uses the same process. The only difference being that it generates the required 350 to 380 vdc HT supply from a battery using a relatively simple high efficiency 12 (or 24 or 48) volt input to 350 volt output DC-DC boost converter.