Power converter device and modulation method thereof

Abstract

The present invention provides a power converter device for converting an alternating current (AC) power input into a direct current (DC) power output. The device comprises n single-phase power conversion circuits arranged in parallel, wherein n is equal to or greater than 2, wherein one of the n single-phase power conversion circuits comprises a single-stage AC / DC converter module having an AC / DC converter in operation; and each of the remaining n-1 single-phase power conversion circuits comprises a two-stage converter module having an AC / DC converter as an input stage and a DC / DC transformer as an output stage.

Description

Technical Field

[0001] The present invention relates to the field of power conversion and in particular, but not exclusively, to a power converter apparatus for converting an alternating current (AC) input to a direct current (DC) output with improved efficiency. Background Art

[0002] Various electronic components including power converters for converting alternating current (AC) power input into direct current (DC) power output are known in the art. Specifically, because the driving power of other electronic components such as digital control, integrated circuits (ICs), magnetic cores, and capacitor losses are independent of the load power, the power consumption of these components will cause low conversion efficiency for AC to DC (AC / DC) power conversion under light power loads. For example, conventional power converters are usually configured with isolated converters connected in parallel, but the power efficiency of such a configuration is relatively low, especially under light power loads. On the other hand, providing non-isolated converters in parallel can provide higher conversion efficiency, but such an arrangement is affected by undesirable circulating currents.

[0003] For example, PCT patent application publication No. WO 2017 / 191245 A1 discloses a converter system for converting a three-phase or single-phase AC voltage into a DC voltage. The converter system includes three converter branches, each branch including a first input and a second input to be supplied with a single-phase AC voltage and a first output and a second output providing a DC voltage; wherein each converter branch includes an AC to DC stage and a DC to DC stage connected between the first and second inputs and the first and second outputs.

[0004] Chinese Patent No. CN 105827120B discloses a single-phase interleaved power factor correction (PFC) circuit used in an air conditioner. The circuit includes three branches arranged in parallel, each branch including an inductor, a switch tube and a diode. The circuit obtains the input current of the air conditioner outdoor unit or the phase current of the air conditioner compressor; and controls the switch tube in each branch according to the input current of the outdoor unit or the phase current of the compressor, so that the interleaved PFC circuit switches between three working states, and the three working states include three branches working in an interleaved mode with a 120-degree phase shift, any two of the three branches working in an interleaved mode with a 180-degree phase shift, and any one of the three branches working in a boost PFC mode, so as to effectively improve the operating efficiency of light load or no load.

[0005] US Patent No. US 8476879 B2 discloses a method of controlling a power factor correction (PFC) converter having a single-phase system, the system comprising a first PFC subcircuit and a second PFC subcircuit to determine when to switch the PFC converter between an interleaved mode and a power saving mode (SEM). The method comprises generating an amplified error signal based on a monitored output voltage of the PFC converter. The second PFC subcircuit is disabled in response to the amplified error signal being less than a first threshold, and is enabled in response to the amplified error signal exceeding a second threshold.

[0006] US Patent No. US11011992 B2 discloses a method and system for reducing circulating current between a plurality of non-isolated modules operating in parallel, wherein the input terminals and output terminals of the plurality of non-isolated modules are respectively connected in parallel, and each non-isolated module comprises a first-stage converter, a bus capacitor and a second-stage converter which are electrically connected in sequence.

[0007] U.S. Patent No. US 7948222 B2 discloses a method of operating an asymmetrical phase circuit topology including a power converter circuit, wherein when the power converter circuit is configured to a first operating mode, the power converter circuit uses a first number of switching devices to operate a first phase switching circuit portion, wherein the first number is greater than zero; and when the power converter circuit is configured to a second operating mode, the power converter circuit uses a second number of switching devices to operate a second phase switching circuit portion, wherein the second number is greater than the first number.

[0008] US Patent No. US11043891 B1 discloses a controller for an AC to DC or DC to AC multiphase power converter of the type having N power converter phases arranged in parallel, wherein N is greater than or equal to 2. The controller includes a control module configured to change or transform a phase shift angle of an input current or an output current of each of the N power converter phases so that an average phase shift value of each of the N power converter phases within a control module AC line cycle is approximately, close to, or substantially the same value.

[0009] Therefore, there is a need for a power converter that can provide improved power efficiency. Summary of the invention

[0010] An object of the present invention is to provide a novel power converter which is able to provide improved power efficiency, especially at light power loads.

[0011] It is another object of the present invention to alleviate or avoid to some extent one or more problems associated with known power converters, or at least provide a useful alternative.

[0012] Other objects of the present invention will be apparent to those skilled in the art from the following description. Therefore, the foregoing object statements are not exhaustive and are intended only to illustrate some of the many objects of the present invention.

[0013] In a first main aspect, the present invention provides a power converter device for converting an alternating current (AC) power input into a direct current (DC) power output. The device comprises n single-phase power conversion circuits arranged in parallel, wherein n is equal to or greater than 2, wherein one first single-phase power conversion circuit among the n single-phase power conversion circuits comprises a single-stage AC / DC converter module having an operating AC / DC converter; and each of the remaining n-1 second single-phase power conversion circuits comprises a two-stage converter module having an AC / DC converter as an input stage and a DC / DC transformer as an output stage.

[0014] In a second main aspect, the present invention provides a method for modulating a power converter device. The device includes n power conversion circuits connected in parallel, where n is equal to or greater than 2. The method includes: providing a first single-phase power conversion circuit including a single-stage AC / DC converter having an AC / DC converter; and providing n-1 second single-phase power conversion circuits, each second single-phase power conversion circuit including a two-stage converter module having an AC / DC converter as an input stage and a DC / DC transformer as an output stage; when the load power of the device is less than or equal to a predetermined, selected or calculated power threshold, automatically bypassing one or more of the output stage DC / DC transformers of the n-1 second single-phase power conversion circuits.

[0015] In a third main aspect, the present invention provides a controller for use with the power converter apparatus of the first aspect. The controller is adapted to automatically bypass one or more of the output stage DC / DC transformers of the second single-phase power conversion circuit when the load power of the apparatus is less than or equal to a predetermined, selected or calculated power threshold.

[0016] The summary of the invention does not necessarily disclose all features necessary to define the invention; the invention may lie in a sub-combination of the disclosed features. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing and other features of the present invention will be apparent from the following description of preferred embodiments provided by way of example only, taken in conjunction with the accompanying drawings, in which:

[0018] Figure 1 is a circuit diagram showing a general structure of a power converter device according to an embodiment of the present invention;

[0019] Figure 2is a circuit diagram showing a power converter device having a two-phase topology according to an embodiment of the present invention;

[0020] Figure 3 is a circuit diagram showing a power converter device having a three-phase topology according to an embodiment of the present invention;

[0021] Figure 4 It is shown Figure 3 A flow chart of the operation of a power converter device;

[0022] Figure 5 Shown by Figure 3 A waveform generated by a power converter device; and

[0023] Figure 6 shows the performance of conventional power converter devices compared to Figure 3 The power efficiency of the power converter device. DETAILED DESCRIPTION

[0024] The following description is of preferred embodiments only as examples and is not limited to the combination of features necessary to implement the invention.

[0025] References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in this specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. In addition, various features are described that some embodiments may exhibit and other embodiments do not. Similarly, various requirements are described that may be requirements of some embodiments but not others.

[0026] The present invention relates to a power converter device, and in particular, but not exclusively, to a power converter device for converting an alternating current (AC) power input into a direct current (DC) power output. The power converter device can be configured to automatically adjust and / or reduce the number of operating phases of the device, such as by converting a multi-phase operation such as a three-phase operation to a single-phase operation under a light power load, thereby improving the power conversion efficiency of the device.

[0027] refer to Figure 1 , a power converter device 10 for converting an alternating current (AC) power input into a direct current (DC) power output is shown. The power converter device 10 may be connected to a single-phase or multi-phase power grid, such as an AC mains grid. The power converter device 10 may include n single-phase power conversion phases or circuits 20 arranged in parallel, where n is a natural number equal to or greater than 2. Preferably, the power converter device 10 includes an asymmetric circuit topology, which will be further described below.

[0028] In one embodiment, the n single-phase power conversion circuits 20 include a first single-phase power conversion circuit 20a having a single-stage AC / DC converter module 22. Preferably, the single-stage AC / DC converter module 22 includes an AC / DC converter 24 connected between the power input 12 and the power output 16. Preferably, the single-stage AC / DC converter module 22 includes only the AC / DC converter 24 as a single input / output stage. The n single-phase power conversion circuits 20 also include the remaining n-1 second single-phase power conversion circuits 20b, each of which has a two-stage converter module 26 connected between its corresponding power input 13, 14 and the power output 16. Preferably, the two-stage converter module 26 includes an AC / DC converter 24 as an input stage connected to a DC / DC transformer 30 as an output stage. Each AC / DC converter 24 is adapted to convert a single-phase AC voltage into an intermediate DC voltage, and each DC / DC transformer 30 is adapted to convert the intermediate DC voltage into a preferably different DC voltage provided to the power output 16. In one embodiment, the AC / DC converter 24 may include a rectifier, a power factor corrector, etc.; and the DC / DC transformer 30 may include an inverter, a transformer, a rectifier, etc.

[0029] For example, Figure 2 As shown in FIG. 1 , the power converter device 10 may include a two-phase circuit having two (n=2) single-phase power conversion circuits 20, wherein one single-phase power conversion circuit 20a has a single-stage AC / DC converter module 22, and the other second single-phase power conversion circuit 20b has a two-stage converter module 26. Figure 2 The device 10 shown in is connectable to a 2-phase grid which may comprise two power inputs 12, 13 supplied with respective single-phase AC voltages. Preferably, the power converter device 10 has one power output 16 providing a DC voltage.

[0030] In such Figure 3 In another embodiment shown in , the power converter device 10 may include a three-phase circuit having three (n=3) single-phase power conversion circuits 20, wherein one single-phase power conversion circuit 20a has a single-stage AC / DC converter module 22, and the other two (n-1=2) second single-phase power conversion circuits 20b each have a two-stage converter module 26. In this embodiment, the device 10 can be connected to a 3-phase grid that may include one power input 15 supplied with AC voltage. Preferably, the power converter device 10 has one power output 16 providing DC voltage.

[0031] Preferably, the power converter device 10 may also include a controller or control module 40 for adaptive modulation of AC to DC power conversion. More preferably, the controller 40 is adapted to automatically adjust or modulate the number of operating power conversion circuits 20 by deactivating or bypassing one or more of the second single-phase power conversion circuits 20b when the load power (P) of the power converter device 10 is less than or equal to a predetermined, selected or calculated power threshold. In a specific embodiment, the power threshold may be determined by dividing the maximum load power (Pmax) of the device 10 by the number n (i.e., the total number of single-phase power conversion circuits 20 in the device 10). The controller 40 is adapted to continuously monitor the load power (P), thereby adaptively controlling the number of power conversion circuits 20, more specifically, the number of operating second single-phase power conversion circuits 20b, thereby minimizing power losses under light loads.

[0032] For example, one or more of the second single-phase power conversion circuits 20b may be configured with a switch 32 that can be actuated to bypass the output stage DC / DC transformer 30 of the two-stage converter module 26, thereby converting the two-stage converter module 26 into a single-stage AC / DC converter module. This is advantageous because it avoids or mitigates the power loss associated with the output stage DC / DC transformer 30. The switch 32 can be activated when the power converter device 10 is connected to a single-phase power grid. The switch 32 may include any conventional electronic switch or circuit switch that can be operated to bypass the output stage DC / DC transformer 30 of the two-stage converter module 26. In one embodiment, the switch 32 may be provided in the form of a relay that can be actuated to bypass one or more of the DC / DC transformers 30 of the corresponding two-stage converter module 26 in the second single-phase power conversion circuit 20b to convert the two-stage converter module 26 into a single-stage AC / DC converter module. The number of second single-phase power conversion circuits 20b converted in this manner may be determined by the load power of the device 10, that is, because the number of second single-phase power conversion circuits 20b in operation depends on the load power of the device 10. For example, when a power load reduction is detected, the controller 40 may switch one or more of the two second single-phase power conversion circuits 20 b in the 3-phase power conversion circuit 20 .

[0033] In one embodiment, the first single-phase power conversion circuit 20a may include a plurality of single-stage converter modules 22 connected in parallel, and each of the second single-phase power conversion circuits 20b may include a plurality of two-stage converter modules 26 connected in parallel. The number of the plurality of single-stage converter modules 22 and the two-stage converter modules 26 in the corresponding circuits may be the same or different. For example, the first single-phase power conversion circuit 20a may include any number N of single-stage AC / DC converter modules 22, where N is any natural number equal to or greater than 2; and each second single-phase power conversion circuit 20b may include any number N of two-stage converter modules 26. However, in another embodiment, the corresponding numbers of the single-stage converter modules 22 at the first single-phase power conversion circuit 20a and the two-stage converter modules 26 at the second single-phase power conversion circuit 20b may be different. In addition, the number of two-stage converter modules 26 at each of the plurality of second single-phase power conversion circuits 20b may also be the same or different. For example, one second single-phase power conversion circuit 20b may include a number N i The second single-phase power conversion circuit 20b may include a number N of two-stage conversion modules 26. ii Two-stage converter modules 26. Without being limited by any specific embodiment described and / or shown herein, those skilled in the art will appreciate that the present invention will cover any variation in the number of converter modules 22, 26 at the power circuit 20 and / or the number of second single-phase power conversion circuits 20b, as long as the device includes an asymmetric topology in which a first single-phase power conversion circuit 20a has a single-stage power converter module 22 and at least one second single-phase power conversion circuit 20b has a two-stage power converter module 26.

[0034] Preferably, a plurality of switches 32, such as relays, may be respectively arranged at the plurality of two-stage converter modules 26 in each of the second single-phase power conversion circuits 20b. The controller 40 may then selectively actuate one or more of the relays at the plurality of modules 26 of the same or different second single-phase power conversion circuits 20b to bypass one or more of the corresponding DC / DC transformers 30, thereby converting one or more modules 26 and / or one or more second single-phase power conversion circuits 20b into single-stage AC / DC converter modules.

[0035] More preferably, the controller 40 is adapted to detect the reference current (I ref ) adjusts or modulates the number of single-stage AC / DC converter modules 22 of the first single-phase power conversion circuit 20a. For example, for a first single-phase power conversion circuit 20a having N single-stage AC / DC converter modules 22, where N can be any natural number equal to or greater than 2, the controller 40 is adapted to detect the reference current (I ref) is less than or equal to N-1 and the maximum current (I max ) when the number of single-stage AC / DC converter modules 22 in operation is reduced from N to N-1. Therefore, the controller 40 is adapted to continuously monitor the reference current (I ref ), thereby adaptively controlling the number of single-stage converter modules 22 in operation to minimize power losses under light loads.

[0036] Figure 4 It is further shown that there are Figure 3 10. Initially, the device 10 may be provided with a user-defined and / or system-detected or recorded power load profile and, optionally, preset delay time information (e.g., preset response time) of the controller 40, depending on the application requirements of the device 10. For example, based on the detected or user-defined load power of the device 10, the controller 40 may decide whether to perform 3-phase operation or single-phase operation. If the load power (P) is greater than the maximum load power (P) of the device 10, for example, by max ) divided by the total number of single-phase power conversion circuits 20 (i.e., n=3), the device 10 will operate in all three phases and the controller 40 will enable all N modules in the single-stage converter module 22 of the one first single-phase power conversion circuit 20a and the two-stage converter modules 26 of the two second single-phase power conversion circuits 20b. On the other hand, if the load power (P) is detected to be less than the threshold power, the controller 40 will preferably deactivate the two second single-phase power conversion circuits 20b of the power conversion circuit 20, thereby effectively converting the 3-phase operation to single-phase operation to minimize power loss or actuate the switch 32 to bypass one or more of the corresponding DC / DC transformers 30, thereby converting one or more modules 26 and therefore one or more second single-phase power conversion circuits 20b into single-stage AC / DC converter modules.

[0037] Preferably, a time delay module 42 may be provided, which may be part of the controller 40 or a separate component of the device 10. The time delay module 42 will determine a delay time for the controller 40 to respond after detecting a load power less than a threshold power and before the action of deactivating or switching the second single-phase power conversion circuit 20b. If the detected power load power (P) is sufficiently low and / or the detected reference current (I ref) is low enough, the controller 40 will deactivate one or more of the modules 22, 26 after the delay time has elapsed. If the delay time is determined to be greater than or equal to a predetermined, selected or calculated delay time threshold, the controller 40 will preferably automatically deactivate one or more of the two (i.e., n-1) second single-phase power conversion circuits 20b. This is to ensure that the controller 40 has a slow response time to respond to any load reduction detected to prevent deactivation of one or more of the two (i.e., n-1) second single-phase power conversion circuits 20b in response to a momentary reduction in load (i.e., a low load reverse power spike). Alternatively, if the delay time is less than the delay time threshold, the controller 40 will allow continued operation of the second single-phase power conversion circuit 20b until a delay time that meets or exceeds the delay time threshold is subsequently detected. The determination of the delay time is important because it effectively slows down the response of the controller 40 to the load reduction to obtain more stable operating control and power conversion performed by the device 10.

[0038] In one embodiment, it is preferred that all n-1 second single-phase power circuits 20b may be bypassed or deactivated, thereby leaving only one first single-phase power conversion circuit 20a under light power load, thereby improving the conversion efficiency of the device 10. However, it is also possible to deactivate or bypass only one or more of the n-1 second single-phase power circuits 20 instead of all, depending on the detected load reduction.

[0039] After a light power load is detected and the device is effectively converted to single-phase operation, the controller 40 will then modulate the number of multiple single-stage converter modules 22 based on adaptive modulation control (AMC), such as Figure 4 For example, for a first single-phase power conversion circuit 20a having N single-stage converter modules 22 and each module having one AC / DC converter 24, where N is any natural number equal to or greater than 2, the controller 40 is adapted to detect that the maximum current (I max ) multiplied by the reference current (I ref ), that is, (N-1)*I max ≥I ref When, and more preferably, when the reference current (I ref ) may be greater than N-2 and the maximum current (I max ), that is, the reference current is in the range (N-1)*I max ≥I ref >(N-2)*I max When the reference current (I ref) and adjusts the number of single-stage converter modules 22 in operation by successively decreasing the number, i.e., decreasing it one at a time during iterations, until the minimum operable number of single-stage converter modules 22 is reached. On the other hand, if a value greater than (N-1)*I is detected max The reference current (I ref ), the controller 40 will continue to enable all N number of single-stage converter modules 22.

[0040] Preferably, before reducing the number of the plurality of single-stage modules 22, the time delay module 42 will be arranged to determine a delay time, and if the delay time is greater than or equal to a predetermined, selected or calculated delay time threshold, the controller 40 performs a deactivation or bypass of one / each of the single-stage modules 22. Likewise, the determination of the delay time slows down the response of the controller 40 to the load reduction, so that a more stable operation can be achieved. Optionally, an adjustment of the phase angle will also be performed before performing the deactivation of one / each of the single-stage modules 22. Preferably, the converter modules are interleaved in operation so that each conversion module has a corresponding phase angle in the switching signal that is different from the other converter modules. The phase angle difference depends on the pulse wave modulation (PWM) signal of the converter device 10. The phase angle difference depends on the result of 360o / N, where N is the number of converter modules. If the phase angle is adjusted appropriately, the ripple on the input AC current can be mitigated or minimized.

[0041] Preferably, the AC / DC converter 24 of the single-stage converter module 22 of the first single-phase power conversion circuit 20a is non-isolated; and the DC / DC transformer 30 of the two-stage converter module 26 of the n-1 second single-phase power conversion circuit 20b is preferably isolated in the form of, for example, an electrically separated transformer.

[0042] In another not shown embodiment of the power converter device 10, the first single-phase power conversion circuit 20a may include a two-stage converter module including an AC / DC converter 24 as an input stage connected to a DC / DC transformer 30 as an output stage, but wherein the DC / DC transformer 30 is preferably permanently bypassed, for example, by permanent actuation of one or more bypass switches, or at least temporarily bypassed by actuation of the one or more bypass switches. In this embodiment, the concept of the invention may be implemented without the need for two different converter module configurations, i.e., all converter modules have the same two-stage configuration, but the first of the modules is configured to operate only as a single-stage converter module.

[0043] In another aspect of the present invention, a method of modulating a power converter device 10 is provided. Preferably, the device 10 includes n power conversion circuits 20 connected in parallel, where n is a natural number equal to or greater than 2. The method includes providing a first single-phase power conversion circuit 20a having a single-stage AC / DC converter module 22 preferably with only an AC / DC converter 24, and n-1 second single-phase power conversion circuits 20b each including a two-stage converter module 26, the two-stage converter module having an AC / DC converter 24 as an input stage and a DC / DC transformer 30 as an output stage. The method also includes automatically bypassing one or more of the output-stage DC / DC transformers of the n-1 second single-phase power conversion circuits 20b when the load power of the device 10 is less than or equal to a predetermined, selected or calculated power threshold.

[0044] Preferably, the first single-phase power conversion circuit 20a includes N single-stage AC / DC converter modules 22, where N is equal to or greater than 2. The method further includes determining a reference current (I ref ) operating current, and in determining the reference current (I ref ) is less than or equal to N-1 and the maximum current of the device (I max ), that is, (N-1)*I max ≥I ref When, and more preferably, when determining the reference current (I ref ) may also be greater than N-2 and the maximum current (I max ), that is, in the range (N-1)*I max ≥I ref >(N-2)*I max When the number of single-stage AC / DC converter modules 22 is adjusted from N to N-1.

[0045] In one embodiment, the method further comprises a step of determining a delay time before the bypassing and / or adjusting step, and performing the bypassing and / or adjusting step if the determined delay time is greater than or equal to a predetermined, selected or calculated delay time threshold.

[0046] In yet another aspect of the present invention, a controller or control module 40 is provided for use with the power converter device 10 described above. The controller 40 is adapted to automatically bypass one or more of the output stage DC / DC transformers of the second single-phase power conversion circuit 20b when the load power of the device 10 is less than or equal to a predetermined, selected or calculated power threshold. Preferably, when the first single-phase power conversion circuit 20a includes N single-stage AC / DC converter modules 22, where N is equal to or greater than 2, the controller is adapted to automatically bypass ...ref ) is less than or equal to N-1 and the maximum current of the device (I max ), and more preferably, in determining the reference current (I ref ) may also be greater than N-2 and the maximum current (I max ), that is, in the range (N-1)*I max ≥I ref >(N-2)*I max When the number of the plurality of single-stage AC / DC converter modules 22 is adjusted from N to N-1.

[0047] In a further embodiment, the controller 40 is further provided with a time delay module 42 for determining a delay time. Preferably, the controller 40 is adapted to bypass one or more of the second single-phase power conversion circuits 20b and / or adjust the number of the plurality of single-stage AC / DC converter modules 22 of the first single-phase power conversion circuit 20a from N to N-1 based on the operating conditions described above only when the determined delay time is greater than or equal to a predetermined, selected or calculated delay time threshold.

[0048] Figure 5 A plurality of waveforms according to an embodiment of the present invention are shown, showing the phase voltage, phase current, output voltage and output current under the power conversion process performed by a 3-phase power converter. Specifically, in response to the power load changing from 6kW to 400W, that is, changing from a high power load to a light power load, the phase current is correspondingly converted from a 3-phase current to a single-phase current; and when the power load changes from 400W to 6kW, that is, changing from a light power load to a high power load, the phase current is correspondingly converted from a single-phase current to a 3-phase current. This indicates that under light loads with only single-phase operation, a power conversion efficiency higher than 98% can be achieved. Further in Figure 6 It is shown in FIG. 1 that, compared to the prior art, an efficiency increase of about 5% to about 13% can be achieved at light loads below 1000 W by converting 3-phase operation to single-phase operation as described in the present invention.

[0049] The invention is therefore advantageous in that it provides a power converter device for converting an alternating current (AC) power input into a direct current (DC) power output. The power converter device is configured with an asymmetric topology, preferably having a first single-phase power conversion circuit having preferably only one single-stage AC / DC converter module and at least one second single-phase power conversion circuit having two-stage AC / DC and DC / DC converter modules. Preferably, the device is adapted to operate at light power load, i.e., when it is determined that the power of the device is less than or equal to P max / n, where P maxWhen is the maximum power operable at the device and n is any number greater than or equal to 2, one or more of the second single-phase power conversion circuits are disabled or bypassed, thereby reducing power losses and thus improving the power efficiency of the device under light power loads. More preferably, the first single-phase power conversion circuit may include N single-stage AC / DC converter modules, where N is any number greater than or equal to 2. Based on I ref In condition (N-1)*I max ≥I ref >(N-2)*I max The reference current (I ref ), where I max Being the maximum current operable at the device, the number of single-stage AC / DC converter modules can be scaled by continuously reducing the number of single-stage modules in operation, N. The scalability or adjustable performance of the number of single-stage AC / DC converter modules in operation enables further reduction of the phase current when the device is in single-phase operation, thereby minimizing power losses and thus enhancing the power conversion efficiency of the device.

[0050] This description illustrates the principles of the invention. It will therefore be appreciated that those skilled in the art will be able to devise various arrangements that embody the principles of the invention and are included within the spirit and scope of the invention but are not explicitly described or shown herein.

[0051] In addition, all statements describing the principles, aspects and embodiments of the present invention and its specific examples herein are intended to cover both its structural equivalents and its functional equivalents. In addition, such equivalents are intended to include currently known equivalents and equivalents to be developed in the future, that is, any elements that are developed to perform the same function, regardless of structure.

[0052] Although the present invention has been shown and described in detail in the drawings and in the foregoing description, it should be considered illustrative and non-restrictive in nature, and it should be understood that only exemplary embodiments are shown and described, and the scope of the present invention is not limited in any way. It can be understood that any feature described herein can be used together with any embodiment. The illustrative embodiments do not exclude each other or exclude other embodiments not described herein. Therefore, the present invention also provides an embodiment comprising a combination of one or more illustrative embodiments described above. Modifications and changes of the present invention set forth herein can be made without departing from the spirit and scope of the present invention.

[0053] It will be appreciated that if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms part of the common general knowledge in the art.

Claims

1. A power converter device for converting alternating current (AC) power input into direct current (DC) power output, characterized in that: The device comprises: n single-phase power conversion circuits arranged in parallel, wherein n is equal to or greater than 2; and Controller; Wherein: one of the n single-phase power conversion circuits includes a single-stage AC / DC converter module having an AC / DC converter; Each of the remaining n-1 single-phase power conversion circuits includes a two-stage converter module having an AC / DC converter as an input stage and a DC / DC transformer as an output stage; The one of the n single-phase power conversion circuits comprises a first single-phase power conversion circuit, the single-stage AC / DC converter module of the first single-phase power conversion circuit comprises N single-stage AC / DC converter modules arranged in parallel, each of the N single-stage AC / DC converter modules comprising an AC / DC converter, wherein N is equal to or greater than 2; and The controller is adapted to: automatically deactivating or bypassing one or more of the output stage DC / DC transformers of the n-1 single-phase power conversion circuits when the load power of the power converter device is less than or equal to a predetermined, selected, or calculated power threshold; adjusting the number of the N single-stage AC / DC converter modules of the first single-phase power conversion circuit based on a reference current Iref; and When the reference current Iref is less than or equal to the product of N-1 and the maximum current Imax of the single-stage AC / DC converter module, the number of the single-stage AC / DC converter modules is reduced from N to N-1.

2. The power converter device according to claim 1, characterized in that One or more of the n-1 single-phase power conversion circuits include a second single-phase power conversion circuit, wherein one or more of the two-stage converter modules of the second single-phase power conversion circuit each include a plurality of two-stage converter modules arranged in parallel, and each of the plurality of two-stage converter modules includes an AC / DC converter as an input stage and a DC / DC transformer as an output stage.

3. The power converter device according to claim 2, characterized in that The second single-phase power conversion circuit includes a switch actuatable to bypass one or more of the output stage DC / DC transformers of the second single-phase power conversion circuit.

4. The power converter device according to claim 3, characterized in that The switch includes a plurality of relays, one of which is disposed at each of the second single-phase power conversion circuits, each of which is actuatable to bypass one or more of the DC / DC transformers of the corresponding two-stage converter module.

5. The power converter device according to claim 1, characterized in that The predetermined, selected or calculated power threshold is determined by dividing the maximum load power Pmax of the power converter arrangement by n.

6. The power converter device according to claim 1, characterized in that Also included is a time delay module, where: The time delay module is adapted to determine a delay time for deactivating or bypassing one or more of the converter modules.

7. The power converter device according to claim 6, characterized in that The controller is adapted to automatically deactivate or bypass one or more of the output stage DC / DC transformers of the n-1 single-phase power conversion circuits when a delay time is greater than or equal to a predetermined, selected or calculated delay time threshold and when the load power of the device is less than or equal to a predetermined, selected or calculated power threshold.

8. The power converter device according to claim 6, characterized in that The controller is adapted to reduce the number of single-stage AC / DC converter modules from N to N-1 when the delay time is greater than or equal to a predetermined, selected or calculated delay time threshold and when the reference current Iref is less than or equal to the product of N-1 and the maximum current Imax of the single-stage AC / DC converter module.

9. The power converter device according to claim 1, characterized in that The power converter device is connected to an n-phase grid having n AC inputs and one DC output or having only one AC input and one DC output.

10. The power converter device according to claim 1, characterized in that The AC / DC converter of the single-stage AC / DC converter module of the first single-phase power conversion circuit is non-isolated; and the DC / DC transformers of the two-stage converter modules of the n-1 single-phase power conversion circuits are isolated.

11. A method of modulating a power converter device, characterized in that: The device comprises n power conversion circuits connected in parallel, wherein n is equal to or greater than 2, and the method comprises: providing a first single-phase power conversion circuit including a single-stage AC / DC converter module, the single-stage AC / DC converter module of the first single-phase power conversion circuit including N single-stage AC / DC converter modules arranged in parallel, each of the N single-stage AC / DC converter modules including an AC / DC converter, wherein N is equal to or greater than 2; and providing n-1 second single-phase power conversion circuits each including a two-stage converter module having an AC / DC converter as an input stage and a DC / DC transformer as an output stage; automatically deactivating or bypassing one or more of the output stage DC / DC transformers of the n-1 second single-phase power conversion circuits when the load power of the device is less than or equal to a predetermined, selected, or calculated power threshold; determining an operating current as a reference current Iref of the first single-phase power conversion circuit; and When it is determined that the reference current Iref is less than or equal to the product of N-1 and the maximum current Imax of the single-stage AC / DC converter module, the number of the single-stage AC / DC converter modules is adjusted from N to N-1.

12. The method according to claim 11, characterized in that The method further includes determining a delay time before the deactivating or bypassing step, and performing the deactivating or bypassing step if the determined delay time is greater than or equal to a predetermined, selected or calculated delay time threshold.

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