Current detection method for DC to three-phase converters using a single DC sensor
First Claim
1. A current detection method for a direct-current to three-phase alternating-current converter wherein said converter includes a direct current power supply, a direct-current sensor for detecting direct-current on the direct current side of the converter, three pairs of transistors for converting the direct current power supply to a three phase alternating current power supply, and a control means to control a sequenced switching of the transistors and the resulting three-phase alternating-currents, said method comprising the steps of:
- (a) controlling the switching of said three pairs of transistors;
(b) detecting direct current values in the direct current side of the converter corresponding to the phase current of a first phase and a second phase by means of said direct-current sensor; and
(c) calculating a phase current value for a third phase by means of said detected current values of the first and second phases.
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Abstract
A current detection method for a direct-current (DC) to three-phase alternating-current (AC) converter can utilize only a single DC sensor to detect and calculate the three-phase alternating currents. The method can detect a direct current value of one phase at each of six different gate states of three pairs of transistors in the DC to three-phase AC converter by means of the DC sensor. In the two-level pulsewidth modulation control, the control signal includes a plurality of carrier periods each being subdivided into three intervals. The three pairs of transistors are switched to the zero state in one interval of each carrier period, and to two different gate states respectively in the two other intervals. The method can detect two current values of different phases respectively in the two other intervals of each carrier period, and then calculate the current value of the other phase in accordance with the principle that the sum of the three-phase currents is always equal to zero.
65 Citations
12 Claims
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1. A current detection method for a direct-current to three-phase alternating-current converter wherein said converter includes a direct current power supply, a direct-current sensor for detecting direct-current on the direct current side of the converter, three pairs of transistors for converting the direct current power supply to a three phase alternating current power supply, and a control means to control a sequenced switching of the transistors and the resulting three-phase alternating-currents, said method comprising the steps of:
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(a) controlling the switching of said three pairs of transistors; (b) detecting direct current values in the direct current side of the converter corresponding to the phase current of a first phase and a second phase by means of said direct-current sensor; and (c) calculating a phase current value for a third phase by means of said detected current values of the first and second phases. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A current detection method for a direct current to three-phase alternating current converter wherein said converter includes a direct current power supply, a direct current sensor for detecting current on the direct current side of the converter, three pairs of transistors for converting the direct current power supply to a three phase alternating current power supply, a driver to control a sequenced switching of the transistors to generate the three-phase alternating currents, and a detecting device for determining and monitoring the direct current and the three phase currents in the converter, said method comprising the steps of:
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(a) generating a pulsewidth modulation control signal with a pluarlity of space vector designations to control the switching of said three pairs of transistors and produce a three phase alternating current output; (b) detecting a first direct current value (I1) in the direct current side of the converter corresponding to the phase current of a first phase of said three pairs of transistors; (c) monitoring the state of the three pair of transistors to distinguish the first phase, and storing the first direct current value in the detecting device; (d) detecting a second direct current value (I2) in the direct current side of the converter corresponding to the phase current of a second phase of said three pairs of transistors; (e) monitoring the state of the three pair of transistors to distinguish the second phase, and storing the second direct current value in the detecting device; (f) calculating a third phase current value (I3) by solving the equation I1 +I2 +I3 =0 for the third phase current value. - View Dependent Claims (8, 9)
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10. An apparatus for determining currents in a six transistor DC to AC converter, including measurement of the direct current in a DC circuit of the converter, measurement of two alternating current phases, and calculation of a third alternating current phase in an AC circuit of the converter, said apparatus comprising:
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(a) a DC current sensor mounted on the DC circuit of the converter for measuring the direct current in the DC circuit of the converter and for generating an output signal; (b) driver means electrically connected to six transistors in the converter for controlling the on-off switching of the six transistors in the converter by the generation of a pulsewidth modulated signal; (c) control means for processing and transmitting control signals, said control means being connected to said driver means to control the sequencing of the transistors to generate a desired AC output, and including an over current protection circuit to protect the converter; and (d) a detecting device electrically connected to said DC current sensor and said control means, said detecting device including a processing means for processing signals from the DC current sensor and for processing signals from said control means, whereby said control means sequences the switching of the transistors in the converter to permit indirect current measurement of a first and a second alternating current phase by said DC current sensor, and calculation of a third alternating current phase by the processing means in said detecting device. - View Dependent Claims (11, 12)
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Specification