Apparatus, power supply, method and recording medium to determine a state of a three-phase AC power supply using instantaneous voltages of three phases of the AC voltage

Patent metadata

Field	Value
Publication number	US-11424610-B2
Application number	US-201916589102-A
Country	US
Kind code	B2
Filing date	Sep 30, 2019
Priority date	Nov 21, 2018
Publication date	Aug 23, 2022
Grant date	Aug 23, 2022

Abstract

A conventional technique makes a configuration complicated. Provided is an apparatus including: a voltage measuring unit configured to measure each of instantaneous voltages of three-phase AC voltage; and a determination unit configured to determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value.

First claim

What is claimed is:

1. An apparatus comprising:
a voltage measuring unit configured to measure each of instantaneous voltages of three-phase AC voltage;
a determination unit configured to determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value; and
a switching unit to switch out the power supply source for an alternative power supply source regardless of the determined state in response to a frequency of the switch out exceeding a reference frequency, the switching unit being configured to switch a to-be-used power supply source between a first power supply source of the three-phase AC voltage and a second power supply source of the three-phase AC voltage based on a determination result of the determination unit of the apparatus,
wherein the determination unit includes:
a first determination unit configured to determine that the power supply source is in an abnormal state in response to the comparison target value intermittently falling below a first reference value for a first reference time, and

a second determination unit configured to determine that the power supply source is in an abnormal state in response to the comparison target value falling below a second reference value smaller than the first reference value.

2. The apparatus according to claim 1 , wherein the first determination unit sequentially shifts a time window having a time duration of the first reference time and determines that the power supply source is in an abnormal state in response to the comparison target value intermittently falling below the first reference value at each of a plurality of time points within the time window.

3. The apparatus according to claim 2 , wherein the first determination unit, after determining that the power supply source is in a normal state, does not determine that the power supply source has become an abnormal state in a case that the time window includes a period during which the comparison target value is continuously equal to or higher than the first reference value for a second reference time that is shorter than the first reference time.

4. The apparatus according to claim 1 , wherein the first determination unit determines that the power supply source is abnormal in response to the comparison target value falling below the first reference value a larger number of times than a reference number within the first reference time.

5. The apparatus according to claim 1 , wherein the determination unit calculates the comparison target value at a period equal to an integral submultiple of a period of the three-phase AC voltage to perform determination.

6. The power supply according to claim 1 , wherein
the determination unit determines a state of the first power supply source, and
the switching unit switches the to-be-used power supply source to the first power supply source in a case that the determination unit determines that the first power supply source is in a normal state and switches the to-be-used power supply source to the second power supply source in a case that the determination unit determines that the first power supply source is in an abnormal state.

7. The power supply according to claim 6 , wherein the determination unit, after determining that the first power supply source is in an abnormal state, determines that the first power supply source has become a normal state in response to the comparison target value for the first power supply source being continuously equal to or higher than the first reference value for the first reference time.

8. The power supply according to claim 6 , wherein the determination unit sets the first reference value to be higher for determining that the first power supply source has become a normal state from an abnormal state than for determining that the first power supply source has become an abnormal state from a normal state.

9. The power supply according to claim 1 , further comprising:
a positive side capacitor and a negative side capacitor connected in order between a positive side output terminal and a negative side output terminal;
a positive side semiconductor switch and a negative side semiconductor switch for each phase of the three-phase AC voltage, the positive side semiconductor switch and the negative side semiconductor switch being connected in order in parallel to the positive side capacitor and the negative side capacitor between the positive side output terminal and the negative side output terminal; and
a plurality of rectifier circuits, each including an AC input terminal and being configured to rectify current flowing between the AC input terminal and the positive side output terminal and between the AC input terminal and the negative side output terminal, wherein
each of the plurality of rectifier circuits is provided for each phase of the three-phase AC voltage and each of the first power supply source and the second power supply source, and includes:
a positive side rectifier connected between the AC input terminal and the positive side output terminal, capable of controlling a conduction state in a forward direction from the AC input terminal to the positive side output terminal, and configured to interrupt current in a reverse direction; and
a negative side rectifier connected between the AC input terminal and the negative side output terminal, capable of controlling a conduction state in a forward direction from the negative side output terminal to the AC input terminal, and configured to interrupt current in a reverse direction.

10. The power supply according to claim 9 , wherein the positive side rectifier and the negative side rectifier of each of the plurality of rectifier circuits are thyristors.

11. A method comprising:
measuring each of instantaneous voltages of three-phase AC voltage;
determining a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value; and
switching out the power supply source for an alternative power supply source regardless of the determined state in response to a frequency of the switching out exceeding a reference frequency, the switching out causing switching between a to-be-used power supply source between a first power supply source of the three-phase AC voltage and a second power supply source of the three-phase AC voltage based on the determined state,
wherein the determining includes:
determining that the power supply source is in an abnormal state in response to the comparison target value intermittently falling below a first reference value for a first reference time, and

determining that the power supply source is in an abnormal state in response to the comparison target value falling below a second reference value smaller than the first reference value.

12. A recording medium having recorded thereon a program that causes a computer to:
measure each of instantaneous voltages of three-phase AC voltage;
determine a state of a power supply source of the three-phase AC voltage based on a result of comparison between a comparison target value corresponding to a sum of n-th powers (n is a positive even number) of the instantaneous voltages of the three-phase AC voltage and a reference value; and
switch out the power supply source for an alternative power supply source regardless of the determined state i

Assignees

• Fuji Electric Co Ltd

Inventors

• Wang Qichen
• Tawada Nobuyuki

Classifications

• G01R31/42

  AC power supplies · CPC title

• H02M1/4216

  operating from a three-phase input voltage (H02M1/4233 takes precedence) · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title

• H02H3/253

  for multiphase applications, e.g. phase interruption · CPC title

• H02M1/4225

  using a non-isolated boost converter · CPC title