Current detection method for DC to three-phase converters using a single DC sensor

Claim 2

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.

Claim 3

A current detection method as claimed in claim 1, wherein said controlling of the switching of the three pairs of transistors includes generating a two-level pulsewidth modulation control signal to control the switching of each pair of transistors.

Claim 4

A current detection method as claimed in claim 2, wherein said controlling the switching of the three pairs of transistors includes the steps of: producing a two-level pulsewidth modulation control signal including a plurality of carrier periods, each carrier period having three switching intervals; controlling the switching of each pair of transistors at a zero state in a first interval of each carrier period; and controlling the switching of each pair of transistors at two different operating states in second and third intervals of each carrier period.

Claim 5

A current detection method as claimed in claim 3, wherein said detecting two direct current values in the direct current side of the converter corresponding to the phase current of a first phase and a second phase includes the step of: monitoring the operating and zero states of the three pairs of transistors during the three intervals of each carrier period; detecting said direct current values of the two operating states during each carrier period by means of said direct current sensor.

Claim 6

The current detection method as claimed in claim 3 wherein the step of controlling the switching of each pair of transistors includes transmitting a zero state and two operating states of a space vector control system by utilizing the pulsewidth modulated signals generated by the control means.

Claim 7

The current detection method as claimed in claim 1 wherein calculating a phase current value for a third phase (I 3 ) by means of said detected current values of the first and second phases (I 1 +I 2 ) includes inserting the detected current values for the two known phases into the equation I 1 +I 2 +I 3 =0 and solving the equation for the value of the third phase.

Claim 8

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: (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 (I 1 ) 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 (I 2 ) 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 (I 3 ) by solving the equation I 1 +I 2 +I 3 =0 for the third phase current value.

Claim 9

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: (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 (I 1 ) 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 (I 2 ) 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 (I 3 ) by solving the equation I 1 +I 2 +I 3 =0 for the third phase current value.

Claim 10

A current detection method as claimed in claim 7, wherein the step of generating a pulsewidth modulated control signal includes generating a signal having a plurality of carrier periods for controlling the switching of the pairs of transistors, each carrier period including two variable-length operating intervals and one variable zero state intervals, whereby the state of the transistors is monitored and the value of the current is detected for the first phase and the second phase during the two operating intervals of the carrier period.

Claim 11

A current detection method as claimed in claim 8, wherein the method includes the additional steps of repeating the process for determining all three phase currents for each carrier period.

Claim 14

The apparatus defined in claim 10 wherein the processing means in said detecting device includes a microprocessor with appropriate software for storing information about two of the alternating current phases, and calculating the third alternating current phase.

Claim 15

The apparatus defined in claim 10 wherein the processing means in said detecting device includes an integrated circuit.