Inverter having center switch and uninterruptible power supply implementing same
First Claim
1. An inverter, comprising:
- an input for receiving electric power from an external source of electric power;
a return line to which the external source of electric power is referenced;
an output for supplying electric power to a connected load;
a first and a second bus coupled to the input;
a pair of output switching elements operable to selectively couple the first and the second bus to the output;
a pair of energy storage devices coupled between each of the first and the second bus and the return line;
a center switch circuit interposed between the pair of energy storage devices and the return line; and
a controller operatively coupled to the pair of output switching elements and the center switch circuit for controlling a state thereof; and
wherein the center switch circuit is operable to selectively enable and disable power flow from the energy storage devices to the first and the second bus.
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Accused Products
Abstract
Presented is a center switching circuit and an inverter and an uninterruptible power supply (UPS) utilizing same. The center switching circuit selectively enables and disables power flow to and from the bus capacitors of an inverter or UPS. As such, the center switching circuitry effectively removes the bus capacitors from the circuit. This allows operation of the inverter or UPS in a high efficiency mode whereby input line voltage may be passed essentially without compensation to the output when the center switching circuit is open. Modulation of the center switching circuit during this mode provides soft charging of the bus capacitors so that they are available to source current in a double-conversion or DC boost mode upon degradation or loss of the line voltage. To supply output power from the bus capacitors, the center switching circuit is closed to associate these capacitors with the neutral. Fault isolation is provided during operation by opening the center switching circuit to prevent power flow from the bus capacitors.
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Citations
35 Claims
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1. An inverter, comprising:
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an input for receiving electric power from an external source of electric power;
a return line to which the external source of electric power is referenced;
an output for supplying electric power to a connected load;
a first and a second bus coupled to the input;
a pair of output switching elements operable to selectively couple the first and the second bus to the output;
a pair of energy storage devices coupled between each of the first and the second bus and the return line;
a center switch circuit interposed between the pair of energy storage devices and the return line; and
a controller operatively coupled to the pair of output switching elements and the center switch circuit for controlling a state thereof; and
wherein the center switch circuit is operable to selectively enable and disable power flow from the energy storage devices to the first and the second bus. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
a pair of input switches controllable by the controller and coupled between the first and second bus and the return line;
an input inductor interposed between the input and the first and second bus; and
wherein the controller opens the center switch circuit and selectively closes one of the pair of input switches to charge the input inductor; and
wherein thereafter the controller closes the center switch circuit and opens the one of the pair of input switches to charge one of the pair of energy storage devices.
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8. The inverter of claim 7, wherein the controller opens the center switch circuit and selectively closes the other of the pair of input switches to charge the input inductor, and wherein thereafter the controller closes the center switch circuit and opens the closed input switch to charge the other of the pair of energy storage devices.
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9. The inverter of claim 7 wherein the external source of electric power includes a source of DC power and a source of AC power, the inverter further comprising an input select circuit operable to selectively couple one of the source of DC power and the source of AC power to the input.
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10. The inverter of claim 9, further comprising a third input switch coupled to the source of DC power and a second input inductor coupled between the third input switch and the return line, and wherein the controller opens the center switch circuit and closes the third input switch to charge the second input inductor, and wherein thereafter the controller closes the center switch circuit and opens the third input switch to charge the other of the pair of energy storage devices.
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11. The inverter of claim 1, wherein the input comprises a plurality of input lines for receiving electric power from a multiphase external source of electric power.
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12. The inverter of claim 1, wherein the pair of output switching elements comprises a plurality of output switching elements, wherein the output comprises a plurality of output lines for supplying a plurality of phases of electric power to the connected load, and wherein the plurality of pairs of output switching elements are operable to selectively couple the first and second bus to the plurality of output lines.
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13. The inverter of claim 1, further comprising:
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a third and fourth bus coupled to the input;
a second pair of energy storage devices coupled between each of the third and fourth bus and the return line;
a second output;
a second pair of output switching elements operable to selectively couple the third and fourth bus to the second output; and
wherein the center switch circuit is interposed between the second pair of energy storage devices and the return line.
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14. The inverter of claim 1, wherein the center switch circuit comprises a first and a second center switch circuit coupled to one of the pair of energy storage devices to individually selectively enable and disable power flow.
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15. The inverter of claim 1, wherein the center switch circuit comprises:
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a switching element having a first and a second connection and a control input coupled to the controller;
a first series coupled pair of diodes coupled across the first and second connection of the switching element, the first series coupled pair of diodes having a first node therebetween coupled to the return line;
a second series coupled pair of diodes coupled across the first and second connection of the switching element, the second series coupled pair of diodes having a second node therebetween coupled to one of the pair of energy storage devices; and
a third series coupled pair of diodes coupled across the first and second connection of the switching element, the third series coupled pair of diodes having a third node therebetween coupled to the other of the pair of energy storage devices.
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16. The inverter of claim 15, wherein the center switch further comprises a bi-directional clamping device coupled between the second and the third nodes.
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17. The inverter of claim 15, wherein the center switch further comprises a first resistor coupled between the second node and the first bus, and a second resistor coupled between the third node and the second bus.
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18. The inverter of claim 15, wherein the center switch further comprises:
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a bi-directional clamping device coupled between the second and the third nodes;
a first resistor coupled between the second node and the first bus; and
a second resistor coupled between the third node and the second bus.
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19. The inverter of claim 1, wherein the center switch circuit comprises:
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a series coupled pair of diodes having a first end coupled to one of the pair of energy storage devices, and a second end coupled to the other of the pair of energy storage devices, the series coupled pair of diodes having a node therebetween coupled to the return line; and
a switching element having a first terminal coupled to one of the pair of energy storage devices and a second terminal coupled to the other of the pair of energy storage devices.
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20. The inverter of claim 19, further comprising a resistor coupled across the series coupled pair of diodes.
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21. The inverter of claim 20, further comprising a bi-directional clamping device coupled across the series coupled pair of diodes.
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22. The inverter of claim 1, wherein the center switching circuit comprises a switching element interposed between the pair of energy storage devices and the return line.
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23. In an inverter having an input for receiving electric power from an external source of electric power, a return line to which the source of electric power is referenced, an output for supplying electric power to a connected load, a positive and a negative bus coupled to the input, a pair of output switches operable to selectively provide power from the positive and the negative bus to the output, a pair of bus capacitors coupled between the buses and the return line, a controller operatively coupled to the output switches for controlling a state thereof, a center switch circuit interposed between the bus capacitors and the return line and operable to selectively enable and disable power flow from the capacitors to the positive and negative buses, the center switch circuit comprising:
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a switching element having a first and a second connection and a control input coupled to the controller;
a first series coupled pair of diodes coupled across the first and second connection of the switching element, the first series coupled pair of diodes having a first node therebetween coupled to the return line;
a second series coupled pair of diodes coupled across the first and second connection of the switching element, the second series coupled pair of diodes having a second node therebetween coupled to one of the bus capacitors; and
a third series coupled pair of diodes coupled across the first and second connection of the switching element, the third series coupled pair of diodes having a third node therebetween coupled to the other bus capacitor. - View Dependent Claims (24, 25, 26)
a bidirectional clamping device coupled between the second and the third nodes;
a first resistor coupled between the second node and the positive bus; and
a second resistor coupled between the third node and the negative bus.
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27. An uninterruptible power supply (UPS) for supplying AC power to a connected load from an external source of utility line voltage, the UPS providing power to the connected load during periods of normal utility line voltage, periods of abnormal utility line voltage, and periods of loss of utility line voltage in a high efficiency mode, a double-conversion mode, and a DC boost mode, respectively, comprising:
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an input adapted to receive utility line voltage;
an inverter having a positive and a negative bus and a pair of output switches, the inverter selectively coupling the positive and negative bus to the connected load by controlling a state of the pair of output switches, the inverter further having a pair of bus capacitors coupled to the positive and the negative bus and a center switch circuit, the center switch circuit selectively enabling and disabling power flow from the bus capacitors to the positive and negative bus;
a battery; and
an input select circuit operable to selectively couple the external utility line voltage and the battery to the inverter. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35)
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Specification