Dual power supply transfer switch based on solid-state switch
A dual power supply transfer switch (SSATS) for switching between a first power supply (S 1 ) and a second power supply (S 2 ) to supply power to a load is provided, includes: a solid-state switch (SS); a mechanical switch (CTR); and a compensation power module (AUX). In the case that the S 1 fails in supplying power to the load, the AUX uses the S 2 to supply power to the load, and the output current of the S 1 is reduced. After satisfying the turn off condition for the SS, the SS turns off the S 1 , the CTR turns off the S 1 and turns on the S 2 . After the S 2 is adjusted to synchronize with the phase of the output current of the S 1 , the SS turns on the S 2 and the AUX stops outputting current. The SSATS provides advantages such as fast transfer, zero interruption, and short voltage sag time.
1 . A dual power transfer switch for supplying uninterrupted power to a load, comprising:
a first solid-state switch configured to selectively connect the load to a first AC power supply providing AC electrical power of a first phase;
a second solid-state switch configured to selectively connect the load to a second AC power supply providing AC electrical power of a second phase;
a first mechanical switch in series with the first solid-state switch;
a second mechanical switch in series with the second solid-state switch; and
a power supply unit configured to selectively receive AC electrical power from a selected one of the first and second power supplies, and to provide AC electrical power of a controlled phase to the load, wherein, during normal operation, the second solid-state switch is open and the first solid-state switch is closed, thereby connecting the load to the first power supply;
a controller configured to:
cause the power supply unit to receive AC electrical power of the second phase from the second power supply and to convert the AC electrical power of the second phase received therefrom to AC electrical power of the first phase;
monitor the first power supply to detect a failure of the first power supply; and
in response to detecting the failure of the first power supply:
cause the first solid-state switch to open, thereby isolating the load from the first power supply;
cause the power supply unit to provide the AC electrical power of the first phase to the load;
cause the first mechanical switch to open and the second mechanical switch to close after causing the first solid-state switch to open;
cause the power supply unit to transition the controlled phase of the AC electrical power provided to the load from the first phase to the second phase; and
cause the second solid-state switch to close in response to the controlled phase of the AC electrical power provided by the power supply unit being synchronized with the second phase of the AC electrical power received from the second power supply, thereby connecting the load to the second power supply.
2 . The dual power transfer switch of claim 1 , wherein the controller causes the first solid-state switch to open in response to AC electrical current provided by the first power supply falling below a first current threshold.
3 . The dual power transfer switch of claim 1 , wherein the controller causes the first solid-state switch to open in response to AC electrical voltage provided by the power supply unit exceeding a predetermined voltage threshold.
4 . The dual power transfer switch of claim 1 , wherein the controller causes the first solid-state switch to open in response to AC electrical current provided by the power supply unit exceeding a predetermined current threshold.
5 . The dual power transfer switch of claim 1 , wherein the controller is further configured, in response to detecting the failure of the first power supply, to:
cause the power supply unit to receive AC electrical power of the first phase from the first power supply and to convert the AC electrical power of the first phase received therefrom to AC electrical power of the second phase.
6 . The dual power transfer switch of claim 1 , wherein the controller is further configured to cause the second mechanical switch to close before causing the second solid-state switch to close.
7 . The dual power transfer switch of claim 1 , wherein the first and second mechanical switches are configured as a single-pole double-throw switch.
8 . The dual power transfer switch of claim 7 , wherein the second solid-state switch is closed after the first solid-state switch is opened.
9 . The dual power transfer switch of claim 1 , further comprising:
a third mechanical switch configured to selectively connect the first power supply to an input of the power supply unit; and
a fourth mechanical switch configured to selectively connect the second power supply to the input of the power supply unit.
10 . The dual power transfer switch of claim 9 , wherein the third and fourth mechanical switches are configured as a single-pole double-throw switch.
11 . The dual power transfer switch of claim 1 , wherein the power supply unit comprises:
a first AC to DC converter configured to convert the AC electrical power selectively received from the first power supply to DC electrical power;
a second AC to DC converter configured to convert the AC electrical power selectively received from the second power supply to DC electrical power; and
a three-phase inverter unit configured to receive the DC electrical power from the first and second AC to DC converters and to generate therefrom the AC electrical power of the controlled phase.
12 . The dual power transfer switch of claim 1 , wherein the first solid-state switch has three bridge arms, each configured to receive a corresponding phase of three-phase AC electrical power of the first phase provided by the first power supply, the second solid-state switch has three bridge arms, each configured to receive a corresponding phase of three-phase AC electrical power of the second phase provided by the second power supply, and the power supply unit is a three-phase power supply unit configured to generate three-phase AC electrical power of the controlled phase.
13 . The dual power transfer switch of claim 12 , wherein the power supply unit comprises:
an AC to DC converter configured to convert the AC electrical power selectively received from the first or second power supplies to DC electrical power; and
a three-phase inverter unit configured to receive the DC electrical power from the AC to DC converter and to generate therefrom the AC electrical power of the controlled phase.
14 . The dual power transfer switch of claim 13 , wherein the AC to DC converter comprises a high-frequency transformer.
15 . The dual power transfer switch of claim 13 , wherein the AC to DC converter comprises a power frequency transformer.
16 . The dual power transfer switch of claim 1 , wherein each of the first and second solid-state switches comprises a bidirectional switch array, wherein the bidirectional switch array is formed through a thyristor, a metal oxide semiconductor field effect transistor (MOSFET), or an insulated gate bipolar transistor (IGBT).
17 . The dual power transfer switch of claim 16 , wherein the bidirectional switch array comprises a reverse parallel pair of thyristors, or MOSFETs, or IGBT transistors.
18 . The dual power transfer switch of claim 1 , wherein the controller is further configured, in response to detecting the failure of the first power supply, to:
cause the power supply unit to provide the AC electrical power of the first phase to the load before causing the first solid-state switch to open, thereby temporarily providing the AC electrical power of the first phase to the load from both the first power supply and the power supply unit.