Power supply apparatus with controllable multiple input rectification

Abstract

A power supply apparatus for providing electrical power to a power consuming device or a power conversion device from at least one of a first AC power source and a second AC power source. The power supply apparatus comprises controllable rectifier devices associated with each of the first and second AC power sources. The controllable rectifier devices are controllable to simultaneously rectify and control the power provided by the first and second AC power sources.

Claims

1. A power supply apparatus for providing electrical power to a power consuming device or a power conversion device from at least one of a first AC power source and a second AC power source, said power supply apparatus comprising: first and second input terminals for connection of said first AC power source between said first and second input terminals; third and fourth input terminals for connection of said second AC power source between said third and fourth input terminals; first and second output terminals for connection of said power consuming device or said power conversion device between said first and second output terminals; a plurality of rectifier devices arranged to receive AC power from said first AC power source or said second AC power source, said plurality of rectifier devices comprising: at least one rectifier device electrically connecting each of said input terminals and said first output terminal in such a way that current is prevented from flowing from said first output terminal to each of said input terminals; and at least one rectifier device electrically connecting each of said input terminals and said second output terminal in such a way that current is prevented from flowing from said input terminals to said second output terminal, wherein each of: a first rectifier device, of said plurality of rectifier devices, electrically connecting said first input terminal and said first output terminal; a second rectifier device, of said plurality of rectifier devices, electrically connecting said first input terminal and said second output terminal; a third rectifier device, of said plurality of rectifier devices, electrically connecting said fourth input terminal and said first output terminal; a fourth rectifier device, of said plurality of rectifier devices, electrically connecting said fourth input terminal and said second output terminal, is a controllable rectifier device being controllable to allow or prevent flow of current through said controllable rectifier device, wherein said power supply apparatus further comprises: a controller connected to each of said controllable rectifier devices for controlling flow of current through said controllable rectifier devices, wherein said controller further comprises: first sensing circuitry arranged to sense at least one of a first voltage, a first frequency, and a first current provided by said first AC power source; and second sensing circuitry arranged to sense at least one of a second voltage, a second frequency, and a second current provided by said second AC power source, and wherein said controller is configured to: control said first rectifier device and said second rectifier device to decrease a time during which flow of current through each of said first rectifier device and said second rectifier device is allowed in response to reduction of at least one of said first voltage and said first frequency; and/or control said third rectifier device and said fourth rectifier device to decrease a time during which flow of current through each of said third rectifier device and said fourth rectifier device is allowed in response to reduction of at least one of said second voltage and said second frequency.

2. The power supply apparatus according to claim 1, wherein said controller is configured to: control said first rectifier device and said second rectifier device to allow flow of current through at least one of said first rectifier device and said second rectifier device only during a portion of each half period for said first AC power source; and/or control said third rectifier device and said fourth rectifier device to allow flow of current through at least one of said third rectifier device and said fourth rectifier device only during a portion of each half period for said second AC power source.

3. The power supply apparatus according to claim 2, wherein said controller is configured to: control said first rectifier device to allow flow of current through said first rectifier device only during a portion of each positive half period for said first AC power source, and said second rectifier device to allow flow of current through said second rectifier device only during a portion of each negative half period for said first AC power source; and/or control said third rectifier device to allow flow of current through said third rectifier device only during a portion of each positive half period for said second AC power source, and said fourth rectifier device to allow flow of current through said fourth rectifier device only during a portion of each negative half period for said second AC power source.

4. The power supply apparatus according to claim 2, wherein said controller is configured to: control said first rectifier device and said second rectifier device to gradually increase a time during which flow of current through each of said first rectifier device and said second rectifier device is allowed; and/or control said third rectifier device and said fourth rectifier device to gradually increase a time during which flow of current through each of said third rectifier device and said fourth rectifier device is allowed.

5. The power supply apparatus according to claim 1, wherein said controller is configured to: control said first rectifier device and said second rectifier device based on said first voltage; and control said third rectifier device and said fourth rectifier device based on said second voltage.

6. The power supply apparatus according to claim 1, wherein said controller is configured to: determine a measure indicative of a period for said first AC power source based on said first voltage; and determine a measure indicative of a period for said second AC power source based on said second voltage.

7. The power supply apparatus according to claim 1, wherein said controller is configured to: compare said first current with a first reference current; and control, if said first current is larger than said first reference current, said first rectifier device and said second rectifier device to decrease a time during which flow of current through each of said first rectifier device and said second rectifier device is allowed; and/or compare said second current with a second reference current; and control, if said second current is larger than said second reference current, said third rectifier device and said fourth rectifier device to decrease a time during which flow of current through each of said third rectifier device and said fourth rectifier device is allowed.

8. The power supply apparatus according to claim 1, wherein said power supply apparatus further comprises the power conversion device connected between said first and second output terminals, said power conversion device being configured to shape an output current between said first and second output terminals to follow an output voltage between said first and second output terminals.

9. A power supply system comprising: the power supply apparatus according to claim 1; the first AC power source connected between said first and second input terminals of said power supply apparatus; and the second AC power source connected between said third and fourth input terminals of said power supply apparatus.

10. The power supply system according to claim 9, wherein: said first AC power source is a single phase source with neutral connected to said second input terminal; and said second AC power source is a single phase source with neutral connected to said third input terminal, said second and third input terminals being electrically connected to each other.

11. A method of switching supply of DC power to a power consuming device from a first AC power source to a second AC power source using a power supply apparatus comprising: first and second input terminals, said first AC power source being connected between said first and second input terminals; third and fourth input terminals, said second AC power source being connected between said third and fourth input terminals; first and second output terminals, said power consuming device being connected between said first and second output terminals; a plurality of rectifier devices comprising: at least one rectifier device electrically connecting each of said input terminals and said first output terminal in such a way that current is prevented from flowing from said first output terminal to each of said input terminals; and at least one rectifier device electrically connecting each of said input terminals and said second output terminal in such a way that current is prevented from flowing from said input terminals to said second output terminal, wherein each of: a first rectifier device, of said plurality of rectifier devices, electrically connecting said first input terminal and said first output terminal; a second rectifier device, of said plurality of rectifier devices, electrically connecting said first input terminal and said second output terminal; a third rectifier device, of said plurality of rectifier devices, electrically connecting said fourth input terminal and said first output terminal; a fourth rectifier device, of said plurality of rectifier devices, electrically connecting said fourth input terminal and said second output terminal, is a controllable rectifier device being controllable to allow or prevent flow of current through said controllable rectifier device, the method comprising the steps of: sensing at least one of a first voltage, a first frequency, and a first current provided by said first AC power source; sensing at least one of a second voltage, a second frequency, and a second current provided by said second AC power source; and controlling said first rectifier device and said second rectifier device to decrease a time during which flow of current through each of said first rectifier device and said second rectifier device is allowed in response to reduction of at least one of said first voltage and said first frequency and/or controlling said third rectifier device and said fourth rectifier device to decrease a time during which flow of current through each of said third rectifier device and said fourth rectifier device is allowed in response to reduction of at least one of said second voltage and said second frequency.

12. The method according to claim 11, wherein: said time during which power from said second AC power source is rectified is gradually increased.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:

(2) FIG. 1 schematically illustrates an application for a power supply system according to an example embodiment of the present invention;

(3) FIG. 2 is a block diagram schematically illustrating the power supply apparatus comprised in the power supply system in FIG. 2;

(4) FIG. 3 is a flow-chart schematically illustrating an example of a method according to an embodiment of the present invention;

(5) FIG. 4 is a timing diagram schematically illustrating an exemplary control sequence; and

(6) FIGS. 5a-b are timing diagrams schematically illustrating conduction angle control for the soft start functionality used in FIG. 4.

DETAILED DESCRIPTION OF AN EXAMPLE EMBODIMENT

(7) In the present detailed description, various embodiments of the power supply apparatus and method according to the present invention are mainly discussed with reference to a power supply system comprising two single phase AC power sources and supplying electrical power to a DC power consumer.

(8) It should be noted that this by no means limits the scope of the present invention, which equally well includes, for example, a power supply system comprising additional single phase AC power sources as well as three phase AC power sources. The power supply system may, moreover, be designed for supplying power to an AC power consumer.

(9) FIG. 1 schematically illustrates an application for a power supply system according to an example embodiment of the present invention. The power supply system 1 comprises a power supply apparatus 2, a first AC power source 3 and a second AC power source 4, and supplies electrical power to a power consuming device 5.

(10) The power consuming device 5 may, for example, be telecom equipment. It should, however, be noted that the power supply system may be used for providing electrical power to practically any power consumer.

(11) An embodiment of the power supply apparatus 2 comprised in the power supply system in FIG. 1 will now be described in more detail with reference to FIG. 2.

(12) Referring to FIG. 2, the power supply apparatus 2 comprises first 10 and second 11 input terminals for connection of the first AC power source 3, third 11 and fourth 13 input terminals for connection of the second AC power source 4, and first 15 and second 16 output terminals for connection of the power conversion unit 33, which in turn has output terminals 20 and 21 for supplying the power consuming device 5, as is illustrated in FIG. 2. In the preferred embodiment shown in FIG. 2, the second and third input terminals are provided as a common input terminal or node 11. This requires that the neutral line of the first AC power source 3 and the neutral line of the second AC power source 4 are both connected to the common input terminal 11.

(13) As is shown in FIG. 2, the power supply apparatus 2 further comprises a first set of rectifier devices 18a-c and a second set of rectifier devices 19a-c.

(14) The first set of rectifier devices comprises a first rectifier device 18a arranged between the first input terminal 10 and the first output terminal 15, a second rectifier device 18b arranged between the common input terminal 11 and the first output terminal 15, and a third rectifier device 18c arranged between the fourth output terminal 13 and the first output terminal 15. Each of the rectifier devices 18a-c of the first set of rectifier devices is, as is indicated in FIG. 2, arranged in such a way that current is prevented from flowing through the rectifying devices 18a-c towards the respective input terminals 10 to 13, at least under normal operating conditions.

(15) Analogously, the second set of rectifier devices comprises a first rectifier device 19a arranged between the first input terminal 10 and the second output terminal 16, a second rectifier device 19b arranged between the common input terminal 11 and the second output terminal 16, and a third rectifier device 19c arranged between the fourth output terminal 13 and the second output terminal 16. Each of the rectifier devices 19a-c of the second set of rectifier devices is, as is indicated in FIG. 2, arranged in such a way that current is prevented from flowing through the rectifying devices 19a-c from the respective input terminals 10 to 13, at least under normal operating conditions.

(16) As is indicated in FIG. 2 using the thyristor symbol, the first 18a and third 18c rectifier devices of the first set of rectifier devices, and the first 19a and third 19c rectifier devices of the second set of rectifier devices are controllable rectifiers.

(17) In this context it should be noted that the thyristor (sometimes also referred to as a silicon controlled rectifier (SCR)) is only one example of a suitable controllable rectifier device. Other examples include a triac, and a thyratron etc.

(18) As shown in FIG. 2, the power supply apparatus additionally comprises a controller for controlling operation of the power supply apparatus 2. In the example embodiment of FIG. 2, the controller comprises a control unit 24, first 25 and second 26 voltage sensors, and first 27 and second 28 current sensors. As is schematically illustrated in FIG. 2, the controller further comprises galvanically isolated drivers 35a-d.

(19) The first voltage sensor 25 is arranged to sense the voltage between the first 10 and second 11 input terminals (across the first AC power source 3), and the second voltage sensor 26 is arranged to sense the voltage between the third 12 and fourth 13 input terminals (across the second AC power source 4). Signals indicative of the sensed voltages are provided from the first 25 and second 26 voltage sensors to the control unit 24.

(20) The first current sensor 27 is arranged to sense the current provided by the first AC power source 3 and the second current sensor 28 is arranged to sense the current provided by the second AC power source 4. Signals indicative of the sensed currents are provided from the first 27 and second 28 current sensors to the control unit 24.

(21) Based on the signals from the first 25 and second 26 voltage sensors and/or the first 27 and second 28 current sensors, the control unit 24 determines control parameters for the controllable rectifiers 18a, 19a, 18c and 19c. To control the controllable rectifiers 18a, 19a, 18c and 19c in accordance with the determined control parameters, the control unit 24 provides control signals to the controllable rectifying devices 18a,c and 19a,c via the galvanically isolated drivers 35a-d.

(22) Even though not specifically indicated in FIG. 2, the control unit may additionally receive further input, such as an input signal indicative of the instantaneous electrical power required by the power consuming device 5. In such embodiments, the control parameters for the controllable rectifiers 18a, 19a, 18c and 19c may additionally or alternatively be determined based on such further input.

(23) Although not shown in FIG. 1 or FIG. 2, the power supply system 1 may further comprise at least one DC power source, such as a battery.

(24) An exemplary method according to embodiments of the present invention will now be described with reference to the flow-chart in FIG. 3.

(25) In a first step 100, it is determined if power conversion is requested. Such a request may, for example, be provided as long as the power consuming device 5 in FIG. 1 is activated.

(26) If it is determined that power conversion is requested, the method proceeds to determine if the first AC power source 3 is presently controlled to provide power in step 101.

(27) If it is determined in step 101 that the first AC power source 3 is not controlled to provide power (is off) then the method proceeds to step 102 and ramps up the conduction angle for the first AC power source 3 from 0% to 100% over a period of at least one AC mains period. Thereafter, in step 103, it is determined if the first AC power source 3 is OK.

(28) If it is instead determined in step 101 that the first AC power source 3 is presently controlled to provide power (is on), then the method directly proceeds to step 103 and determines if the first AC power source 3 is OK.

(29) The determination in step 103 of whether or not the first AC power source 3 is OK may, for example, involve sensing at least one of a voltage, a frequency and a current of the first AC power source 3 and to compare the sensed parameter(s) with one or several corresponding threshold values or ranges.

(30) If it is determined in step 103 that the first AC power source 3 is not OK, then the method proceeds to step 104 to turn off the first AC power source 3 by rapidly decreasing the conduction angle for the first AC power source from 100% to 0%. For instance, the conduction angle may be decreased from 100% to 0% in a matter of microseconds. Thereafter, the method returns to step 100 to check if power conversion is presently requested.

(31) If it is instead determined in step 103 that the first AC power source is OK, then the method directly returns to step 100 to check if power conversion is presently requested.

(32) Regarding the second AC power source 4, steps 105 to 108, corresponding to the above described steps 101 to 104, respectively, are carried out.

(33) If the determination in step 100 is that power conversion is presently not requested (whether or not power conversion has previously been requested), then the method proceeds to step 109 to determine if the first AC power source 3 is presently controlled to provide power. If it is determined in step 109 that the first AC power source 3 is presently controlled to provide power (is on), then the method proceeds to step 110 where the first AC power source is turned off as was described above in connection with the description of step 104. Thereafter, the method returns to step 100 to check if power conversion is presently requested.

(34) If it is instead determined in step 109 that the first AC power source is off, then the method directly returns to step 100 to check if power conversion is presently requested.

(35) Regarding the second AC power source 4, steps 111 and 112, corresponding to the above described steps 109 and 110, respectively, are carried out.

(36) An exemplary control sequence that may result from controlling the power supply apparatus in FIG. 2 using the method in FIG. 3 will now be described with reference to the timing diagram in FIG. 4.

(37) The timing diagram in FIG. 4 includes from top to bottom graphs illustrating the power in the power conversion unit 33 (the total power through the power conversion unit 33), the power conversion request status, the conduction angle control of the first AC power source 3, the conduction angle control of the second AC power source 4, the status of the first power source 3 (OK or NOT OK), and the status of the second power source 4 (OK or NOT OK).

(38) At the time t.sub.0, a command to start power conversion is received. Since both the first AC power source 3 and the second AC power source 4 are off and OK, the power supply apparatus 4 is controlled to soft start the first AC power source 3 and the second AC power source 4.

(39) This soft start according to embodiments of the present invention will now be described with reference to FIG. 2 and to the timing diagrams in FIGS. 5a-b.

(40) FIG. 5a illustrates the voltage across the first AC power source 3 as a function of time, and FIG. 5b illustrates the voltage provided from the first AC power source 3 to the power conversion unit 33 as a function of time during a part of a soft start sequence using conduction angle control.

(41) At the end of the first half period, controllable rectifier device 18a, referring to FIG. 2, is controlled to allow passage of current during the time period t.sub.a indicated in FIGS. 5a-b. At the end of the second half period, controllable rectifier device 19a is controlled to allow passage of current during the time period t.sub.b indicated in FIGS. 5a-b. At the end of the third half period, controllable rectifier device 18a is again controlled to allow passage of current during the time period t.sub.c indicated in FIGS. 5a-b. Since t.sub.c>t.sub.b>t.sub.a, the power provided by the first AC power source 3 to the power conversion unit 33 is gradually increasedthe first AC power source 3 is soft started or ramped up.

(42) Returning now to FIG. 4, both the first AC power source 3 and the second AC power source 4 are soft started as described above starting from the time t.sub.0. This means that power is provided to the power conversion unit 33 as is schematically indicated in the top graph in FIG. 4.

(43) At the time t.sub.1, it is determined that the first AC power source 3 is NOT OK. As a result of this determination, controllable rectifier devices 18a and 19a will immediately be controlled to prevent passage of current through the controllable rectifier devices 18a and 19a, which means that the power provided by the first AC power source 3 to the power conversion unit 33 will more or less instantaneously be reduced to zero.

(44) At the time t.sub.2, it is determined that the first AC power source 3 is again OK, and it will be soft started again as described above.

(45) At the time t.sub.3, it is determined that the second AC power source 4 is NOT OK. As a result of this determination, controllable rectifier devices 18c and 19c will immediately be controlled to prevent passage of current through the controllable rectifier devices 18c and 19c, which means that the power provided by the second AC power source 4 to the power conversion unit 33 will more or less instantaneously be reduced to zero.

(46) At the time t.sub.4, it is determined that the second AC power source 4 is again OK, and it will be soft started again as described above.

(47) At the time t.sub.5, both the first AC power source 3 and the second AC power source 4 are determined to be NOT OK. As a result of this determination, both the first AC power source 3 and the second AC power source 4 will be shut off as described above, and the power through the power conversion unit 33 will drop to zero.

(48) At the time t.sub.6, the second AC power source 4 is again determined to be OK and is soft started again. The power conversion unit 33 is restarted when the power is sufficiently high.

(49) Finally, at the time t.sub.7, a logical request to stop power conversion is received, and the second AC power source 4 is turned off.