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Voltage Adder And Subtractor

  1. Jan 18, 2009 #1
    Hello Every1
    I'm doin a project on Closed Loop inverter and There are 2 eqns which i would like to realize using electrical circuits. They are as follows:

    B=2/M(V1/V2)
    V0=0.1666(B-1/B)

    where B,M,V1,V2,V0 are voltages.

    Is it possible for to realize the above equations using a combination of Adder and Divider circuits?
    Are ther any IC's for performing such operations?

    Any help will b appreciated

    Thanks in advance
     
  2. jcsd
  3. Jan 19, 2009 #2

    berkeman

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    Staff: Mentor

    Why don't you tell us a little bit about adder and divider circuits first? Are you adding currents, or do you want to add voltages?
     
  4. Jan 19, 2009 #3
    Thanks for the reply.Ok here it goes.Basically i'm doin a closed loop Impedance source inverter.
    Wat i'm really doin is--V2 is Input DC voltage of the Order of 30V, it varies between 25 to 30. My aim is to keep the AC output voltage(V1) at constant of 45V(Peak Voltage).M is the modulation index which is constant at 0.5. Now depending on the Changes in Input DC voltage(Which is V2), the Value of B changes which in turn changes value V0 and there by increasing the shoot through time period(Which Boosts the inverter bridge voltage and keeping my output AC voltage as constant).
    Now since V2 is the only variable in the equation, on substitution of values for V1,M i get the value for B=180/V2.
    Where V2=Input DC Voltage. Now this value of B which is voltage must b given to the next circuit to get the value of V0, where V0 is also voltage.
    Hope I'm clear.
     
  5. Jan 19, 2009 #4

    berkeman

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    I'm not sure I know what a "closed loop Impedance source inverter" is. When I think of a power inverter, I think of DC in and AC power voltage out at some frequency and amplitude. The output is generally supposed to be pretty sinusoidal in character, to emulate the 60Hz AC Mains, for example.

    What is the "modulation index"? What are you modulating, and why? You don't want a sine wave output from your inverter?

    What are you using for your AC oscillator? If you are aiming for an output sine wave, how much distortion is withing your specs? How much output switching noise is allowed? How fast can your input DC voltage vary, and what kind of droop/overshoot/recovery specs are you trying to meet?
     
  6. Jan 20, 2009 #5
    Wel My input is DC and Output is AC, Fine. But the inverter bridge of a normal VSI consists of Switching devices rite(MOSFETS,IGBTs etc), Now Mine is a single phase inverter, so the inverter topology is H-bridge type, Which means i'm havin four switching devices. Now in order to Operate my inverter i have to provide Gating pulses to these switching devices at appropriate time intervals. For this I'm using PWM technique,Thats comparing a carrier wave(Triangle wave) with a modulating signal( Sine or Square or DC wave). In my case i'm using Triangle for carrier and DC for modulating wave. Depending on the conditions (Using the comparator) pulses are generated which is given to the switching devices. Now the ratio of Amplitude of Modulating signal to the Amplitude of carrier(Peak value) gives the modulating index which is M.
    In normal VSI u cannot boost the voltage(O/p always < I/P). But in impedance source inverter ther is a Impedance network (Consisting of Inductors and Capacitors) placed between the DC source and the inverter bridge which allow a boost operation( O/P can be > I/P). The normal VSI consist of 2 states namely Active and Zero states, But in Impedance source inverter another state called Shoot Through is Possible( The Switching devices in a single arm are switched on simultaneously which is prohibited in normal VSI) the boost operation takes place in this shoot through state and in the next active state u get the boosted voltage.
    In a closed loop Impedance source inverter, if suppose I/P is reduced then with the help of closed loop operation the shoot through time interval is increased there by makin the O/P constant. The equations in my first post are the relations between this Input voltage and the boost Factor(B) which determines the shoot through time interval.
    Hope I'm clear

    I don need any AC oscillator. All the other factors like distortion, switchin losses etc are secondary considerations only. It doesn't matter much.
     
  7. Jan 20, 2009 #6

    berkeman

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  8. Jan 20, 2009 #7
    Hey thanks for providing the results. One of the links says somethin bout constant O/P voltage for variable I/P voltage which is my Aim... Would definitely give it a try..
    Thank u very much
     
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