US3603867A
Expired / Lapsed
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Method of controlling a polyphase inverter
Assignee: Battelle Memorial Institute Inc
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Filing: 1970-06-09
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Granted: 1971-09-07
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Expires: 1990-06-09
Abstract
Abstract A method of controlling a polyphase inverter intended to supply a polyphase voltage whose frequency and amplitude must be variable independently. A sine wave of fixed frequency is generated and is sampled at a succession of instants at a frequency close to that of the sine wave. From this sampling is obtained a train of width-modulated pulses whose width corresponds to the amplitude of the sine wave at the successive sampling instants. Any variation in frequency of the sampling results in a corresponding variation in frequency of the pulse train and any variation in amplitude of the sine wave correspondingly affects the width of the pulses. As many such pulse trains as there are phases are produced and the leading and trailing edges of the pulses, which are independently variable by virtue of the sampling frequency and the amplitude of the sine wave being independent, are used to control the firing and extinction of rectifier elements in the inverter.
Inventors
- 👤 Gerard Cuenoud
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:41
CPC Classifications
H; H02; H02M; H02M5/00; H02M5/02; H02M5/04; H02M5/22; H02M5/25; H02M5/27; H02M5/271
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
421 words
A method of controlling a polyphase inverter intended to supply a polyphase voltage whose frequency and amplitude are adjustable independently of one another, said inverter comprising a number of switching groups equal to the number of phases of said polyphase voltage, and said switching groups comprising rectifier elements whose firing and extinction are cyclically triggered by external control signals, the method comprising a. generating at least one sinusoidal voltage wave whose frequency (fo) is fixed and whose amplitude (Ao) can vary between zero and a maximum value, b. sampling this sinusoidal wave by measuring its momentary value at sampling instants which succeed one another within at least one train whose frequency can vary about a value close to the fixed frequency of said sinusoidal wave, this measurement being made in relation to a first fixed reference level which is so chosen that the momentary value of this sinusoidal wave measured in relation to the said level is always different from zero, c. converting this momentary value into a pulse duration by generating a succession of asymmetrical triangular signals whose steep edges precede the oblique edges and coincide with these sampling values, the height of these steep edges being proportional to said momentary value of the said sinusoidal voltage and the slope of these oblique edges having a predetermined value, and by generating rectangular pulses whose height is fixed and whose width is equal to the period elapsing between the appearance of the said steep edge and the instant when the said oblique edge reaches a second reference level, the succession of these pulses constituting a set of rectangular waves which are equAL in number to the switching groups of said inverter, which have the same frequency as said sampling train and which are width-modulated, the variation of this width being proportional to the momentary value of the said sinusoidal voltage, and d. allocating one of said rectangular waves to each of the switching groups of the said inverter, the leading and trailing edges of the pulses of said rectangular waves being utiliZed to form said control signals, so that the voltage across the terminals of each of said switching groups is a pulsating voltage whose mean value oscillates in accordance with a sinusoidal law, whose frequency is equal to the absolute value of the difference between the fixed frequency of said sinusoidal voltage wave and the variable frequency of the said succession of sampling instants, and the amplitude of which is proportional to the variable amplitude of said sinusoidal voltage wave.
Claim 2
Independent Claim
421 words
A method of controlling a polyphase inverter intended to supply a polyphase voltage whose frequency and amplitude are adjustable independently of one another, said inverter comprising a number of switching groups equal to the number of phases of said polyphase voltage, and said switching groups comprising rectifier elements whose firing and extinction are cyclically triggered by external control signals, the method comprising a. generating at least one sinusoidal voltage wave whose frequency (fo) is fixed and whose amplitude (Ao) can vary between zero and a maximum value, b. sampling this sinusoidal wave by measuring its momentary value at sampling instants which succeed one another within at least one train whose frequency can vary about a value close to the fixed frequency of said sinusoidal wave, this measurement being made in relation to a first fixed reference level which is so chosen that the momentary value of this sinusoidal wave measured in relation to the said level is always different from zero, c. converting this momentary value into a pulse duration by generating a succession of asymmetrical triangular signals whose steep edges precede the oblique edges and coincide with these sampling values, the height of these steep edges being proportional to said momentary value of the said sinusoidal voltage and the slope of these oblique edges having a predetermined value, and by generating rectangular pulses whose height is fixed and whose width is equal to the period elapsing between the appearance of the said steep edge and the instant when the said oblique edge reaches a second reference level, the succession of these pulses constituting a set of rectangular waves which are equAL in number to the switching groups of said inverter, which have the same frequency as said sampling train and which are width-modulated, the variation of this width being proportional to the momentary value of the said sinusoidal voltage, and d. allocating one of said rectangular waves to each of the switching groups of the said inverter, the leading and trailing edges of the pulses of said rectangular waves being utiliZed to form said control signals, so that the voltage across the terminals of each of said switching groups is a pulsating voltage whose mean value oscillates in accordance with a sinusoidal law, whose frequency is equal to the absolute value of the difference between the fixed frequency of said sinusoidal voltage wave and the variable frequency of the said succession of sampling instants, and the amplitude of which is proportional to the variable amplitude of said sinusoidal voltage wave.
Claim 3
Dependent Claim
79 words
A method according to claim 1, wherein a single sinusoidal wave of fixed frequency is generated and is sampled at instants included in a number of separate trains of sampling instants equal in number to the switching groups contained in said inverter, said trains being out of phase in relation to one another by a period equal to the quotient of the interval between two sampling instants of one of these trains by the number of said switching groups.
Claim 4
Dependent Claim
81 words
A method according to claim 1, wherein there are generated a number of separate sinusoidal waves equal in number to the switching groups contained in said inverter, said sinusoidal waves all having a common fixed frequency and being out of phase in relation to one another by a duration equal to the quotient of their common period by the number of said switching groups, and wherein these sinusoidal waves are sampled at instants included in a single train of sampling instants.
Claim 5
Dependent Claim
46 words
A method according to claim 1, wherein the slope of said oblique edges is given a value such that, when the amplitude of said sinusoidal wave is zero, the width of said rectangular pulses is substantially equal to the half-period of said train of sampling instants.
Claim 6
Dependent Claim
28 words
A method according to claim 4, wherein the slope of said oblique edges is given a value proportional to the frequency of the said train of sampling instants.
Claim 7
Dependent Claim
48 words
A method according to claim 1, wherein the second reference level is varied in accordance with a sinusoidal law whose frequency and phase are equal to the frequency and phase, respectively, of said sinusoidal wave and whose amplitude is proportional to the amplitude of the said sinusoidal wave.
Claim 8
Dependent Claim
382 words
Apparatus for carrying out the method according to claim 1, the apparatus comprising a set of driving circuits equal in number to the phases of said inverter and each of which is allocated to one of the switching groups of said inverter, each of these driving circuits comprising: a sampling circuit provided with a main input for connection to a first external generator capable of supplying at least one sinusoidal voltage wave whose frequency is fixed and whose amplitude can vary between zero and a maximum value, with a control input for connection to a second external generator capable of supplying at least one train of periodic pulses whose amplitude is fixed and whose frequency can vary about a value equal to the frequency of said sinusoidal voltage wave, and with an output, said sampling circuit comprising a chopper-amplifier whose input is connected at least indirectly to the said main input and, in use, is brought to a fixed voltage constituting said first reference level, whose output is connected through a unidirectional rectifier element to said output, and whose triggering member is connected at least indirectly to the said control input, a measuring capacitor connected between the output of said sampling circuit and a first fixed reference voltage, a constant-rate discharge circuit connected to the terminals of said capacitor, and a comparator circuit provided with two inputs and one output, one of said inputs being connected to the output of the said sampling circuit, and the other input being, in use, brought to a second voltage, having the same polarity as the first and constituting the said second reference value, and this output, which constitutes the output of the said driving circuit, being for connection to a grid control circuit attached to the corresponding switching group of said inverter, thE whole arrangement being such that each of the said driving circuits supplies control signals formed of a succession of rectangular pulses, each of which has its positive-going edge coinciding with one of the pulses of the train of pulses supplied by said second generator and a width which, at constant frequency, depends linearly upon the momentary value possessed, at the instant when the pulse corresponding to the said positive-going edge is set up, by the sinusoidal wave supplied by said first generator.
Claim 9
Dependent Claim
132 words
Apparatus according to claim 7, wherein, with said first external generator provided with a plurality of independent outputs equal in number to the driving circuits, and supplying at each of them a sinusoidal wave, said sinusoidal waves all having common fixed frequency, and a common variable amplitude, and being out of phase in relation to one another by a quantity equal to their period divided by the number of these waves, the main inputs of each of said driving circuits are individually connected to the outputs of the said first generator and the control inputs of each of said driving circuits are connected to a common control input which is connected to the output of the said second generator, the latter supplying a single train of periodic pulses having a variable frequency.
Claim 10
Dependent Claim
130 words
Apparatus according to claim 7, wherein, with said second generator being provided with a plurality of independent outputs, equal in number to said driving circuits, and supplying at each of them a train of periodic pulses, these trains having a common variable frequency and being out of phase in relation to one another by a quantity equal to their period divided by the number of said trains, the main inputs of each of the said driving circuits are connected to a common main input, which is connected to the output of said first generator, the latter supplying a single sinusoidal wave having a fixed frequency and a variable amplitude, and said control inputs of each of said driving circuits are individually connected to the separate outputs of said second generator.
Claim 11
Dependent Claim
109 words
Apparatus according to claim 7, wherein each of the said driving circuits comprises a first correcting circuit which is connected between said sampling circuit and said comparator circuit and which is so arranged as to extract a portion of the signal applied to the main input of the said sampling circuit and to apply it to that one of the inputs of the said comparator circuit which is connected to said second voltage, so as to impart to the voltage applied to the said input an oscillation having the same frequency and the same phase as the said sinusoidal wave, and an amplitude proportional to that of the latter.
Claim 12
Dependent Claim
98 words
Apparatus according to claim 7, wherein each of the said driving circuits comprises a second correcting circuit which is connected between said control input and said constant-rate discharge circuit and which is so arranged as to produce from the signal applied to said control input a voltage representing the frequency of said train of periodic pulses, and to modify, with the aid of said voltage, the impedance of said discharge circuit, so that, with constant amplitude of said sinusoidal wave, the width of said rectangular pulses is inversely proportional to the frequency of said train of periodic pulses.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-06 | 1975-03-08 | 1975-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-06 | 1979-03-08 | 1979-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-06 | 1983-03-08 | 1983-09-07 | $7700.00 | Window Closed / Lapsed |