PROGRAMMED WAVEFORM POWER INVERTER CONTROL SYSTEM

• US 3,805,139 A
• Filed: 09/29/1971
• Issued: 04/16/1974
• Est. Priority Date: 09/29/1972
• Status: Expired due to Term

• Current Assignee: Harry Swartzlander Jr. Hoffman, Kenton Hugh Knickmeyer
• Original Assignee: Harry Swartzlander Jr. Hoffman, Kenton Hugh Knickmeyer
• Inventors: Hoffman, Harry Swartzlander Jr., Knickmeyer, Kenton Hugh
• Primary Examiner(s): Shoop, Jr., William M.
• Application Number:
  US05/293,751
• Time in Patent Office: 930 Days
• Field of Search: 307/64,66,87 321/9,9A,5
• US Class Current: 307/64
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 5/45 using semiconductor devices only
• CPC Class Codes: H02M 7/529 using digital control

Abstract

A multi-phase programmed pulse waveform generating inverter control system for controlling power switches to provide transient free electric power to a critical load in synchronism with a utility power source.

Claims

1. A method of generating multi-phase waveforms comprising the steps of:

1. generating a sequence of timing pulses;

2. encoding said sequence of timing pulses into a plurality of modulated pulse sequences P1 through PN, the modulation of each sequence P1 through PN defining a different portion of a cycle of a waveform of said multi-phase waveforms;

3. connecting sequences P1 through PN to corresponding switching circuits S1 through SN respectively, each of said switching circuits S1 through SN providing an energy pulse to integrating means whenever a pulse of a connected pulse sequence of said sequences P1 through PN is received, thereby each of said switches in cooperation with its connected modulated pulse sequence generating a different portion of a waveform of said multi-phase waveforms;

4. precessing the relationship of said modulated pulse sequences to said switches by repeating step 1 and step 2 and reconnecting said modulated pulse sequences to said switching circuits so that said sequences P2 through PN, P1 are connected to said switching circuits S1 through SN respectively whereby each switching circuit is controlled by a next sequence of modulated pulses thereby continuing to generate next successive portions of each cycle of each of said multi-phase waveforms.

2. The method of claim 1 comprising the steps of:

changing said energy pulses provided by one switch Si of said switches S1 through SN to be of opposite potential each time said sequence P1 is connected to control said switch Si, thereby generating an alternating potential waveform having negative and positive half cycles.

3. connecting sequences P1 through PN to corresponding switching circuits S1 through SN respectively, each of said switching circuits S1 through SN providing an energy pulse to integrating means whenever a pulse of a connected pulse sequence of said sequences P1 through PN is received, thereby each of said switches in cooperation with its connected modulated pulse sequence generating a different portion of a waveform of said multi-phase waveforms;

4. The method of claim 2 further comprising the step of:

varying within predetermined limits the rate at which said sequence of timing pulses is generated to maintain a generated waveform of said generated multi-phase waveforms in frequency and phase synchronism with a reference waveform as long as said reference waveform remains within a frequency range proportional to said predetermined limits.

5. The method of claim 4 wherein said reference waveform is a power source waveform and further comprising the step of:

switching a load from said waveform of said generated multi-phase waveforms to said power source waveform when said impedance of said load drops to a value which allows more than a predetermined amount of power to flow through said switch if said generated waveform is in synchronism with said power source waveform.

6. A multi-phase waveform generator comprising:

a timing generator for repeatedly generating a sequence of timing pulses;

encoding means connected to said timing generator for encoding said sequence of timing pulses intO a plurality of modulated pulse sequences P1 through PN at a corresponding plurality of outputs, the modulation of each of said sequences P1 through PN defining a different portion of a cycle of a waveform of multi-phase waveforms;

a plurality of switching means S1 through SN, each of said switching means having an input and including integrating means at an output for providing a waveform which is the integral of energy pulses generated within said switching means in response to pulses of a connected one of said modulated pulse sequences from said encoding means;

gating means connected to and actuated by said timing generator for connecting each of said outputs of said encoding means to said input of a corresponding one of said switching means S1 through SN respectively causing each of said switches to generate a different portion of a different waveform of said multi-phase waveforms, said gating means incrementing each time said sequence of timing pulses is repeated so that said input of each of said switches is reconnected to an output of said encoding means corresponding to a next of said modulated pulse sequences so that said switch SN is connected to an output of said encoding means which was just previously connected to said switch S1 whereby said switch SN continues to generate successive portions of a waveform of said multi-phase waveforms.

7. The multi-phase waveform generator of claim 6 wherein each of said switches further comprises means for generating energy pulses of positive potential and energy pulses of negative potential, said means being controlled by said gating means to provide energy pulses of opposite potential each time said output corresponding to said modulated pulse sequence P1 is connected to said switch.

8. The multi-phase waveform generator of claim 7 wherein each of said switches further comprises feedback means for controlling the energy of said energy pulses by varying the width of said energy pulses by an amount inversely proportional to the change in amplitude of said waveform generated by said switch.

9. The multi-phase waveform generator of claim 6 further comprising:

synchronizing means connected to said timing generator and to a reference waveform for varying the rate at which said sequence of timing pulses is generated within predetermined limits, to maintain one waveform of said generated multi-phase waveforms in frequency and phase synchronism with said reference waveform so long as said reference waveform remains within a frequency range proportional to said predetermined limits.

10. The multi-phase waveform generator of claim 9 wherein said reference waveform is a power source waveform of a multi-phase power source, said waveform generator further comprising:

detecting means for providing an output when a condition indicative of failure of at least one of said waveforms being generated by said switches S1 through SN is detected;

bypass switch means connected to said multi-phase power source and to loads being driven by said switches S1 through SN;

bypass control means having inputs connected to said detecting means and to said synchronizing means and having an output connected to said bypass switch for transferring said loads from said switches S1 through SN to said multi-phase power source when an output signal is received from said detecting means while said generated multi-phase waveform is substantially in synchronism with said power source.

11. The multi-phase waveform generator of claim 6 wherein said encoding means further comprises:

memory means having a plurality of storage locations addressable by said timing generator, each of said locations having a bit position for each of said modulated pulse sequences P1 through PN, the presence and absence of bits in said bit positions constituting said modulation of said modulated pulse sequences; and

wherein said gating means further comprises;

sequence counter means for identifying said outputs of said memory means corresponding to each of said modulated pulse sequences P1 through PN in turn, said sequence counter means having a first input connected to a source of advance pulses, said sequence counter generating N counts before repeating said N counts;

phase time counter means for identifying each of said switching means in turn, said phase time counter means being connected to said source of advance pulses for generating N+1 counts before repeating said N+1 counts, a first output of said phase time counter being connected to said timing generator for advancing the addressed location of said memory means and being connected to an inhibit input of said sequence counter for inhibiting one advance pulse at said first input to keep said sequence counter in synchronism with said phase time counter, each of N remaining outputs of said phase time counter being connected to a different one of said switching means S1-SN for gating an identified one of said modulated pulse sequences to an identified one of said switching means in turn for each of said switching means S1-SN, as each of said memory locations is addressed;

said sequence counter having a second input connected to said timing generator for advancing said sequence counter by one count while said first input of said sequence counter is inhibited whenever said timing sequence is repeated to increment the count within said sequence counter with respect to the count within said phase time counter thereby incrementing said gating means.

12. The method of generating a waveform comprising the steps of:

repeatedly generating a plurality of timing pulses;

encoding each plurality of said timing pulses into an integral modulated pulse sequence;

controlling a power switch to generate positive voltage pulses a first time said integral modulated pulse sequence is generated;

controlling said power switch to generate negative voltage pulses a second time said integral modulated pulse sequence is generated;

integrating said positive and negative voltage pulses respectively to provide an electric power waveform.

13. The method of claim 12 further comprising the step of:

controlling the energy of said voltage pulses by varying the width of said voltage pulses by an amount inversely proportional to the change in amplitude of said generated waveform thereby providing amplitude regulation of said electric power waveform to compensate for variations of source potential and variations of the impedance of a load being driven by said electric power waveform.

14. The method of claim 13 further comprising the step of:

varying within predetermined limits, the rate at which said plurality of timing pulses is generated to maintain said electric power waveform in frequency and phase synchronism with an electric utility waveform as long as said utility waveform remains within a frequency range proportional to said predetermined limits.

15. The method of claim 14 further comprising the step of:

switching a load from said electric power waveform to said electric utility waveform if said electric power waveform is in synchronism with said utility waveform.

16. The method of claim 14 further comprising the step of:

switching a load from said utility waveform to said electric power waveform if said electric power waveform has been in synchronism with said utility waveform for a predetermined period of time.

17. The method of claim 14 wherein said varying step further comprises the steps of:

allowing a plurality of oscillator pulses to generate a lesser plurality of timing pulses;

inhibiting an oscillator pulse thereby increasing the time period between two of said timing pulses.

18. The method of claim 17 further comprising the steps of:

calculating the number of oscillator pulses which must be inhibited to reduce the frequency of said electric power waveform being provided to be in frequency and phase synchronism with said utility waveform;

repeating said step of allowing a plurality of oscillator pulses to generate a lesser plurality of timing pulses and said step of inhibiting an oscillator pulse, in sequence for the calculated number of times.

19. The method of claim 4 wherein said varying step further comprises the steps of:

allowing a plurality of oscillator pulses to generate a lesser plurality of timing pulses;

inhibiting at least one oscillator pulse thereby increasing the time period between two of said timing pulses;

calculating the number of oscillator pulses which must be inhibited to reduce the frequency of said multi-phase waveforms so that said generated waveform thereof is in frequency and phase synchronism with said reference waveform, repeating said step of allowing a plurality of oscillator pulses to generate a lesser plurality of timing pulses and said step of inhibiting at least one oscillator pulse in sequence for the calculated number of times.

20. A waveform generator comprising:

a timing generator for repeatedly generating a plurality of timing pulses;

encoding means connected to said timing generator for encoding each of said plurality of timing pulses into an integral pulse modulated pulse sequence;

a switch connected to said encoding means for alternately generating a plurality of positive voltage pulses and a plurality of negative voltage pulses in response to a first integral modulated pulse sequence and a next integral modulated pulse sequence respectively;

means connected to said power switch to integrate each of said pluralities of voltage pulses to provide an electric power waveform.