The present disclosure relates to a power module, a multi-port power converter and an energy system comprising the same.

In distributed energy systems, especially those based on renewable energy, there is a growing demand for multi-port DC-DC converters for both off-grid and on-grid applications. Typically, distributed energy systems require interconnecting a plurality of power elements, more in particular sources, storages and/or loads, in a way that enables power flow between said power elements.

Figure 1 illustrates a system 100 known in the art. System 100 comprises a plurality of power elements lOla-lOle that are interconnected by a multi-port power converter 110. Multi-port power converter 110 comprises a transformer 102 having a plurality of transformer ports 103, each transformer port 102 being electrically connected to one or more respective windings among a plurality of windings of transformer 102, wherein the windings corresponding to different transformer ports 103 have a mutual inductance associated therewith. Multi-port power converter 110 further comprises a plurality of power modules 104 through which power elements lOla-lOle can be connected to transformer 102. Transformer 102 provides galvanic isolation between power elements lOla-lOle, which may be beneficial in various applications for safety reasons.

Each power module 104 has a respective first module port 105a that is configured to be electrically connected to a respective power element, and a second module port 105b that is configured to be electrically connected to a respective transformer port 103 of transformer 102. Each power module 104 comprises a converting unit (not shown) that enables power conversion from DC at a side of a corresponding power element to AC at a side of transformer 102 using a switching circuit (not shown), such as an active bridge circuit, as will be appreciated by a person skilled in the art. The converting unit of power module 104 may be bidirectional, i.e., additionally enabling power conversion from AC at a side of transformer 102 to DC at a side of the corresponding power element, for example using a rectifying circuit.

Power can be transferred between power elements lOla-lOle via power modules 104 and transformer 102. For example, DC power from power element 101a can be converted to AC power by the corresponding power module 104, which AC power can be transferred via corresponding transformer port 103 to another transformer port corresponding to another power module and power element. In particular, the cycle-to-cycle average power transferred between a power element i and a power element j in system 100 can be modelled as [Eqn. 1]: wherein V and V- are DC voltages at corresponding first module ports 105a, is an equivalent inductance between ports i and j, f _s is a switching frequency of the switching circuit, and (pj is a phase difference between AC voltages at corresponding transformer ports 103. Thus, the power flow between power elements can be controlled by changing the DC voltage amplitudes and the sign and magnitude of the phase shift.

To that end, multi-port power converter 110 further comprises a central control unit 106 configured to control power modules 104 based on information about power elements lOla-lOle that are connected to multi-port power converter 110. For example, central control unit 106 is configured to control the switching circuits of certain power modules 104 based on known or configurable information about power elements lOla-lOle and power modules 104. For example, the information may comprise one of a voltage or current rating, a (typical) power required by or available from the power elements, or the like.

A problem that is associated with the known system is that, generally, the central control unit as described above requires complex control algorithms based on system data from all power modules and power elements to ensure smooth and stable operation. As a result, the control unit in the known system is relatively expensive to implement, and limits the scalability of the system, which reduces its practicality in applications requiring scalable solutions.

It is an object of the present disclosure to provide a power module, multi-port power converter comprising the same and energy system comprising the same, for which the abovementioned problem does not occur or hardly so.

According to an aspect of the present disclosure, a power module is provided comprising first module port configured to be electrically connected to a power element, the power element being a storage, source and/or load, and a second module port configured to be electrically connected to a transformer port of a multi-port transformer. The power module further comprises a converting unit comprising a switching unit electrically connected between the first module port and the second module port, wherein the converting unit is configured to, using the switching unit, convert DC power received at the first module port to AC power at the second module port or convert AC power received at the second module port to DC power at the first module port. The power module further comprises a control unit configured to detect an AC voltage signal received from the multi-port transformer at the second module port, generate a control signal based on a frequency and phase of the detected AC voltage signal, and control the switching unit using said control signal.

By performing control based on the AC voltage signal received at the transformer port to which the power module is connected, power flow control can be performed in a decentralized manner, reducing the total system cost and increasing the scalability of the system. The power module need not be permanently electrically connected to the transformer port of the multi-port transformer and may for example be connected or disconnected therefrom.

The addition, removal or replacement of power modules and/or power elements from a system while it is live, referred to as hot-swapping, can cause excessively high in-rush currents which could affect or even damage components of the system, such as to the power module. For example, without limiting such an in-rush current, other power modules of the system may be reset, or connectors by which a power module or power element is connected may suffer damage due to the high initial current.

To that end, when the second module port is electrically connected to the transformer port, the control unit may be configured to control the switching unit using a first control signal having a frequency and phase corresponding to the frequency and phase of the detected AC voltage signal, and, after a predetermined time period, control the switching unit using a second control signal having a frequency corresponding to the frequency of the detected AC voltage signal and being phase-shifted with respect to the AC voltage signal. In such embodiments, the control unit may be configured to start controlling the switching unit using the first control signal at a zero-crossing of the AC voltage signal.

Additionally or alternatively to the above, prior to electrically disconnecting the second module port from the transformer port, the control unit may be configured to control the switching unit using a third control signal having a frequency and phase corresponding to the frequency and phase of the detected AC voltage signal, and, after a predetermined time period, stop controlling the switching unit. In such embodiments, the control unit may be configured to stop controlling the switching unit at a zero-crossing of the AC voltage signal.

In doing the above, the power module is provided with a hot-swap capability that can substantially limit or even prevent excessive in-rush currents from occurring. Moreover, with the power module in accordance with the present disclosure, a hot-swap capability is achieved without the need for a centralized control unit.

According to an embodiment, the control unit may comprise a zero-crossing detector configured to detect zero-crossings in the AC voltage signal and to generate a synchronization signal based on the detected zero-crossings, the zero-crossings in the AC voltage signal being indicative of the frequency and phase of the AC voltage signal, and a control signal generator configured to generate the control signal based on the synchronization signal. In a further embodiment, the control unit may further comprise a signal conditioning unit configured to condition the AC voltage signal by attenuating, amplifying and/or filtering the AC voltage signal, and to provide the conditioned AC voltage signal to the zero-crossing detector for detecting zerocrossings in the conditioned AC voltage signal. At least one of the zero-crossing detector, the control signal generator and, if applicable, the signal conditioning unit may be realized using a digital signal processor, for example a microprocessor.

The switching unit may comprise an active bridge circuit comprising a plurality of switching elements, such as field-effect transistors, FETs. The switching elements may be configured to, upon being controlled by the control signal from the control unit, alternately couple and cross-couple a first and second terminal of the first module port to a first and second terminal of the second module port.

The converting unit may further comprise a rectifying unit comprising a plurality of rectifying elements, such as diodes, and a rectifying capacitor coupled between terminals of the first module port. The rectifying elements may be comprised in or formed by the switching elements. For example, the switching elements may comprise Silicon Carbide, SiC, based metal- oxide-semiconductor FETs, MOSFETs, which have an internal body diode that can act as a respective rectifying element.

The power module may further comprise an impedance comprising an inductor electrically connected in between the second module port and the converting unit.

The power module may further comprise a decoupling capacitor electrically connected between the second module port and the converting unit. In so far as the power module comprises the above-described impedance, the decoupling capacitor may be comprised in the impedance and may be connected in series with the corresponding inductor.

The power module may at least partially be realized on a printed circuit board, PCB. For example, the converting unit may be realized on a PCB, and the control unit may be realized on a separate PCB and/or may be mounted on the PCB comprising the converting unit.

The power element may be comprised in the power module and may be electrically connected to the first module port.

According to another aspect of the present disclosure, a multi-port power converter is provided comprising a multi-port transformer comprising a plurality of windings and a plurality of transformer ports, each transformer port being electrically connected to one or more respective windings among the plurality of windings. The one or more windings of respective transformer ports have a mutual inductance with respect to one another. Furthermore, the plurality of transformer ports comprise a primary transformer port and a plurality of secondary transformer ports. The multi-port power converter further comprises a plurality of power modules as defined above, the second module ports thereof being electrically connected to respective secondary transformer ports, and a primary power module comprising a first module port configured to be electrically connected to a primary power element, and a second module port that is electrically connected to the primary transformer port, wherein the primary power module is configured to generate an AC voltage signal and to provide said AC voltage signal to the primary transformer port to thereby impose a corresponding AC voltage signal on each of the secondary transformer ports used by the power modules to generate the control signal. Furthermore, a first effective inductance between the primary power module and each of the plurality of power modules is less than a second effective inductance between any two power modules.

The first effective inductance may be at least 5 times less than the second effective inductance. In a preferred embodiment, the first effective inductance may be at least 10 times lower than the second effective inductance.

To at least partially realize the first effective inductance and the second effective inductance, the plurality of windings may be arranged such that a leakage inductance associated with the primary transformer port, corresponding to at least part of the first effective inductance, is less than a leakage inductance associated with each of the secondary transformer ports corresponding to at least part of respective second effective inductances. Alternatively or additionally, to at least partially realize the first effective inductance and the second effective inductance, the multi-port converter may further comprise one or more inductors, each inductor being electrically connected between a respective secondary transformer port and a corresponding power module.

The multi-port transformer may be realized on a printed circuit board, PCB.

According to another aspect of the present disclosure, a method of operating the multi-port power converter is provided, comprising: generating, by the primary power module, an AC voltage signal and providing said AC voltage signal to the primary transformer port to thereby impose a corresponding AC voltage signal on each of the secondary transformer ports; detecting, by the plurality of power modules, said corresponding AC voltage signal received from the multi-port transformer at the second module port; generating, by respective control units of the plurality of power modules, a control signal based on a frequency and phase of the detected AC voltage signal; and controlling, by said respective control units, respective switching units of the plurality of power modules using said control signal.

According to yet another aspect of the present disclosure, an energy system is provided. The energy system comprises a multi-port power converter as defined above, a primary power element connected to the first module port of the primary power module, the second module port thereof being electrically connected to the primary transformer port, the primary power element being a source, and a plurality of secondary power elements, each secondary power element being a storage, source and/or load, and being electrically connected to the first module port of a respective power module.

Next, exemplifying embodiments will be described with reference to the appended drawings, wherein:

Figure 1 illustrates a distributed energy system known in the art; Figure 2A illustrates an energy system according to an embodiment of the present invention;

Figure 2B illustrates a simplified electrical model of the energy system of Figure 2A;

Figure 2C shows exemplary signal diagrams of port voltages and port currents in the energy system of Figure 2A;

Figure 3 illustrates a power module according to an embodiment of the present invention;

Figure 4 illustrates a multi-port power converter according to an embodiment of the present invention; and

Figure 5 illustrates a schematic side view of a plurality of windings of a multi-port transformer according to an embodiment of the present invention.

Hereinafter, reference will be made to the appended drawings. It should be noted that identical reference signs may be used to refer to identical or similar components.

In Figure 2A, an energy system 20 is shown, comprising a multi-port power converter 10, a primary power element 21, and a plurality of secondary power elements 22a-22c.

Primary power element 21 is a source-type power element and is preferably a stable source. For example, primary power element 21 may be obtained using a power grid, e.g., by rectifying and converting power from an outlet into DC power. As another example, primary power element 21 may be a battery.

Secondary power elements 22a-22c may be a source-type power element, such as a solar panel, a load-type power element, such as an appliance having a resistive load, or a storage-type power element, such as a battery.

Multi-port power converter 10 comprises a multi-port transformer 11, a primary power module 1 ’ and a plurality of power modules 1. Multi-port transformer 11 comprises a plurality of windings (not shown) and a plurality of transformer ports 12, 13a-13c comprising a primary transformer port 12 and a plurality of secondary transformer ports 13a-13c. Each transformer port 12, 13a-13c is electrically connected to one or more respective windings among the plurality of windings of multi-port transformer 11. In multi-port transformer 11, the winding(s) corresponding to respective transformer ports 12, 13a-13c have a mutual inductance with the winding(s) from other transformer ports 12, 13a-13c, which enables power transfer between transformer ports 12, 13a-13c and, ultimately, between power elements 21, 22a-22c.

Primary power module 1’ comprises a first module port 2a’ electrically connected to primary power element 21, and a second module port 2b’ electrically connected to a primary transformer port 12. Similarly, power modules 1 each comprise a first module port 2a electrically connected to a respective secondary power element 22a-22c, and a second module port 2b electrically connected to a respective secondary transformer port 13a-13c. Power modules 1 each comprise a converting unit (not shown) configured to, using a switching unit comprised therein, convert DC power received at first module port 2a to AC power at second module port 2b or convert AC power received at second module port 2b to DC power at first module port 2a. Power modules 1 will be described in more detail further below with reference to Figure 3.

In Figure 2B, a simplified electrical model of energy system 20 is shown. Primary power element 21 and primary power module 1’ are modelled as a square-wave voltage source VI, and secondary power elements 22a-22c and power modules 1 are modelled as respective square-wave voltage sources V2-V4 that provide an AC port voltage to multi-port transformer 11. Furthermore, multi-port transformer 11 is modelled using a star equivalent circuit comprising a magnetising inductance Lm and a plurality of leakage inductances L1-L4, each leakage inductance being associated with a transformer port 12, 13a-13c of multi-port transformer 11. As will be appreciated by a person skilled in the art, leakage inductances L1-L4 are modelled inductances that are indicative of a degree of magnetic coupling (i.e., the mutual inductance) between windings corresponding to transformer ports 12, 13a-13c. Furthermore, the voltage across magnetising inductance Lm is hereinafter referred to as a star-point voltage Vm.

In the electrical model of Figure 2B, power flow occurs partially based on a difference in phase between voltages from voltage sources V1-V4. However, since transformer ports 12, 13a- 13c are all mutually magnetically coupled through their corresponding windings, the effective starpoint voltage Vm of a conventional multi-port transformer is dependent on all port voltages provided by voltage sources V1-V4. Because of this, the power flow between, for example, the ports corresponding to voltage sources V2, V3 would not only depend on the magnitude and phase of said voltage sources V2, V3, but also depends on the port voltages from remaining voltage sources VI, V4. This effect is hereinafter referred to as power flow coupling.

To mitigate the power flow coupling, multi-port power converter 10 is arranged such that a first effective inductance between primary power module 1’ and each of power modules 1 is less than a second effective inductance between any two power modules 1. For example, an effective leakage inductance distribution of multi-port transformer 11 according to the present disclosure can be altered such that leakage inductance LI associated with primary transformer port 12 is lower than a leakage inductance L2-L4 associated with each of secondary transformer ports 13a-13c. For example, the physical structure of multi-port transformer 11, i.e., the windings corresponding to each transformer port 12, 13a-13c, can be arranged such that primary transformer port 12 has a strong magnetic coupling with each of secondary transformer ports 13a- 13c with respect to a magnetic coupling between any two secondary transformer ports 13a-13c. In other words, multiport transformer 11 may have a leakage inductance distribution where leakage inductance LI is less than each of leakage inductances L2-L4. As such, star-point voltage Vm is predominantly determined by the voltage of voltage source VI, and is made substantially independent from voltage sources V2-V4. The leakage inductance distribution of multi-port transformer 11 may be realized using various arrangements of the windings, such as using interleaving, as will be described in further detail with reference to Figure 5.

Preferably, the first effective inductance is at least five times less than the second effective inductance, more preferably at least ten times greater. For example, leakage inductance LI is five or more times less than each of leakage inductances L2-L4.

Additionally or alternatively, as shown in Figure 2A, multi-port power converter 10 according to the present disclosure comprises one or more impedances Z comprising an inductor coupled between respective secondary transformer ports 12a-12c and corresponding power modules 1. For example, the impedance is formed by an inductor external to the transformer to emulate a ‘leakage’ inductance and increase the effective inductance at secondary transformer ports 12a-12c with respect to the inductance at primary transformer port 12. Here, it is noted that impedances Z corresponding to respective secondary transformer ports 13a-13c need not be identical. The inductance of the inductor in each impedance Z could be different, and/or some of secondary transformer ports 13a-13c may not have an associated impedance connected thereto. For example, the inductor may in some embodiments only be included for secondary transformer ports 13a- 13c for which the associated leakage inductance is not sufficiently high with respect to the effective inductance at primary transformer port 12.

In Figure 2C, a simplified signal timing diagram corresponding to the electrical model of Figure 2B is shown when an impedance between voltage source V 1 and the star-point node is substantially less than an impedance between each of voltage sources V2-V4 and the star-point node for power flow decoupling. In particular, Figure 2C shows voltage waveforms of each of voltage sources VI -V4, a voltage waveform of star-point voltage Vm, and current waveforms of a current through each of voltage sources V1-V4.

As can be seen from Figure 2C, star-point voltage Vm is predominantly regulated by the voltage of voltage source VI, thus decoupling the power flow between voltage sources V2-V4. In other words, primary power module 1’ generates, based on primary power module 21, an AC voltage signal and provides said AC voltage signal to primary transformer port 12 to thereby impose a corresponding AC voltage signal on each of secondary transformer ports 13a- 13c.

In Figure 3, an exemplary embodiment of power module 1 according to the present disclosure is shown.

Power module 1 comprises first module port 2a, second module port 2b, and a converting unit 3 electrically connected between first module port 2a and second module port 2b. Converting unit 3 comprises a switching unit, and is configured to, using the switching unit, convert DC power received at first module port 2a to AC power at second module port 2b or convert AC power received at second module port 2b to DC power at first module port 2a.

Power module 1 further comprises a control unit 4 configured to control the switching unit. In particular, by decoupling the power flow as discussed with reference to Figures 2B and 2C, primary power element 21 and corresponding primary power module 1 ’ impose an AC voltage on each of secondary transformer ports 13a-13c. To control a direction and magnitude of power flow, control unit 4 is configured to detect the AC voltage signal received from multi-port transformer 11 at second module port 2b, generate a control signal based on a frequency and phase of the detected AC voltage signal, and control the switching unit using said control signal. In doing so, power module 1 is controlled to regulate power flow to and from a corresponding power element in a decentralized manner and without requiring information about coupling between ports or power flow from other power elements and corresponding power modules in energy system 20. In particular, since the AC voltage signal is imposed on each of secondary transformer ports 13a- 13c, a magnitude and direction of power flow can be controlled by regulating a phase of the control signal with respect to the phase of the AC voltage signal.

In some embodiments, the switching unit is formed by a plurality of switching elements T1-T4. For example, switching elements T1-T4 comprise bipolar junction transistors (BJTs), fieldeffect transistors (FETs), such as metal -oxide-semiconductor FETs (MOSFETs) or junction FETs (JFETs), or the like. In these embodiments, switching elements T1-T4 can be actuated by control unit 4 such that switching elements T1-T4 alternately couple and cross-couple a first and second terminal of first module port 2a to a first and second terminal of second module port 2b. For example, for FETs, a gate terminal can be controlled using respective control signals from control unit 4.

For example, during a first portion of a switching period, switching elements T1 and T4 are actuated such that switching element T1 forms an electrical connection between a first terminal of first module port 2a and a first terminal of second module port 2b, and such that switching element T4 forms an electrical connection between a second terminal of first module port 2a and a second terminal of second module port 2b. Similarly, during a second portion of the switching period different from the first portion, switching elements T2 and T3 are actuated such that switching element T2 forms an electrical connection between the first terminal of first module port 2a and the second terminal of second module port 2b, and such that switching element T3 forms an electrical connection between the second terminal of first module port 2a and the first terminal of second module port 2b. By alternately coupling and cross-coupling first module port 2a and second module port 2b, a DC voltage at first module port 2a can be converted in to a square-wave (AC) voltage at second module port 2b by switching elements T1-T4. In this embodiment, control unit 4 generates a control signal for each of switching elements T1-T4, and the control signals for switching elements T1 and T4 have an opposite phase (180 degrees) with respect to the control signals for switching elements T2 and T3.

Converting unit 3 further comprises a rectifying unit formed by a rectifying capacitor Cl and a plurality of rectifying elements D1-D4, such as diodes, arranged in a bridge circuit. In some embodiments, rectifying elements D1-D4 are formed by or comprised in switching elements Tl- T4. For example, switching elements T1-T4 such as silicon carbide based MOSFETs may have an internal body diode.

It may occur that power module 1 is damaged during operation of energy system 20, for example due to an exceedingly high current, mechanical stress, thermal stress, switching element degradation or end-of-life, or the like. To that end, it is desirable that power module 1 can be connected to and/or disconnected from multi-port transformer in a safe and reliable manner even when energy system 20 is live.

To that end, control unit 4 is further configured to, when second module port 2b is electrically connected to a secondary transformer port, control the switching unit using a first control signal having a frequency and phase corresponding to the frequency and phase of the detected AC voltage signal, and, after a predetermined time period, control the switching unit using a second control signal having a frequency corresponding to the frequency of the detected AC voltage signal and being phase-shifted with respect to the AC voltage signal. For example, prior to altering the phase of the control signal provided to the switching unit for controlling the magnitude and direction of power flow, the switching unit is first synchronously controlled with the AC voltage signal for a predetermined amount of time, such as in a range between 50 ms - 10 s. In doing so, in-rush currents are minimized or even prevented during ‘start-up’ of power module 1. Preferably, control unit 4 is configured to start controlling the switching unit using the first control signal at a zero-crossing of the AC voltage signal, to even further minimize in-rush currents.

Similarly, power module 1 may need to be removed while energy system 20 is live. To that end, prior to electrically disconnecting second module port 2b from a corresponding secondary transformer port, control unit 4 is configured to control the switching unit using a third control signal having a frequency and phase corresponding to the frequency and phase of the detected AC voltage signal, and, after a predetermined time period, such as in a range between 50 ms - 10 s, stop controlling the switching unit. Again, preferably, control unit 4 is configured to stop controlling the switching unit at a zero-crossing of the AC voltage signal.

It is noted that the exemplary predetermined time periods described above are not limiting to the present invention. The optimal predetermined time period during start-up and during shutdown need not be identical and may depend on the application. It will be appreciated by a person skilled in the art that the predetermined time periods can be suitably selected based on application requirements. In the embodiment shown in Figure 3, control unit 4 comprises a zero-crossing detector 5b configured to detect zero-crossings in the AC voltage signal, and to generate a synchronization signal based on the detected zero-crossings. The zero-crossings in the AC voltage signal are indicative of the frequency and phase of the AC voltage signal. Control unit 4 further comprises a control signal generator 5c configured to generate the control signal(s) based on the synchronization signal, which control signal(s) is/are provided to switching elements T1-T4.

Control unit 4 optionally further comprises a signal conditioning unit 5a configured to condition the AC voltage signal by attenuating, amplifying and/or filtering the AC voltage signal, and to provide the conditioned AC voltage signal to zero-crossing detector 5b for detecting zerocrossings in the conditioned AC voltage signal. For example, signal conditioning unit 5a may comprise a filter configured to filter the AC voltage signal to remove ringing noise from the AC voltage signal, and/or a differential amplifier to isolate a part of control unit 4 from a remainder of power module 1.

Signal conditioning unit 5a, zero-crossing detector 5b and control signal generator 5c may be each be implemented using analog circuits or may partially or even fully be implemented using a digital signal processing (DSP) unit, such as a microprocessor.

Optionally, impedance Z, which was described with reference to Figures 2A-2C, is additionally or alternatively comprised in power module 1. When impedance Z is comprised in power module 1, the power flow in energy system 20 can be decoupled without the leakage inductance distribution of multi-port transformer 11. Power module 1 may further comprise a DC blocking capacitor (not shown) coupled between converting unit 3 and second module port 2, which may be comprised in impedance Z.

Here, it is noted that primary power module 1’ described with reference to Figures 2A-2C may be similar to power module 1. In particular, primary power module 1 ’ may also comprise a switching unit, a rectifying unit and a control unit configured to control the switching unit. However, since primary power module 1 ’ is configured to generate the AC voltage signal and to impose said AC voltage signal on secondary transformer ports 13a-13c, the control unit of primary power module 1 ’ does not generate a control signal for its switching unit based on a detected voltage. Instead, a switching frequency employed by the control unit of primary power module 1’ determines the frequency of the AC voltage signal imposed on multi-port transformer 11, and may thus also determine a switching frequency of switching units in power module 1. The switching frequency employed by the control unit of primary power module 1 ’ may be pre-stored in a memory and/or may be configurable by a user.

In Figure 4, an exemplary embodiment of multi-port power converter 10 is shown. In this embodiment, multi-port transformer 11 is arranged on a PCB 14, and PCB 14 further comprises metal tracks 15 that provide an electrical connection between windings of multi-port transformer 11 and corresponding transformer ports 12, 13a-13e. Primary power module 1’ and power modules 1 can be coupled to primary transformer port 12 and secondary transformer ports 13a-13e, respectively. In an example, secondary transformer ports 13a-13e comprise a female connector, and the first module port (not shown) of power module 1 comprises a male connector for connecting to the female connector.

Furthermore, primary power module 1’ is arranged on PCB 14, for example by means of mounting primary power module 1’ on PCB 14. PCB 14 further comprises primary connectors 16 by which a primary power element (not shown) can be coupled to the first module port (not shown) of primary power module 1 ’ . Alternatively, the primary power element may be comprised in primary power module 1 ’ . In this embodiment, multi-port transformer 11 is shown as a transformer having planar windings, although the present disclosure is not limited thereto.

Although power modules 1 are shown as being separated from PCB 14, the present disclosure also envisages embodiments in which one or more power modules 1 are mounted on PCB 14. For example, one or more of power modules 1 may be comprised in an electronic package which can be mounted on PCB 14 in such a way as to connect the second module port (not shown) to a respective one of secondary transformer ports 13a-13e.

In Figure 5, an exemplary arrangement of windings of multi-port transformer 11 is shown. In particular, multi-port transformer 11 may comprise a plurality of primary windings 12-1, 12-2 corresponding to a primary transformer port, a plurality of first secondary windings 13a-l, 13a-2 corresponding to a first secondary transformer port, a plurality of second secondary windings 13b- 1, 13b-2 corresponding to a second secondary transformer port and a plurality of third secondary windings 13c-l, 13c-2 corresponding to a third secondary transformer port. In Figure 5, the windings may be considered to be wound around an axis perpendicular to the viewing direction.

In this embodiment, first secondary windings 13a-l, 13a-2, second secondary windings 13b- 1 , 13b-2 and third secondary windings 13c-l, 13c-2 are each arranged in an interleaved manner with respect to primary windings 12-1, 12-2. Furthermore, an area of the secondary windings may each partially overlap with a different portion of an area of the primary windings, as shown in Figure 5.

The coupling between primary windings 12-1, 12-2 and secondary windings 13a-l, 13a-2, 13b-l, 13b-2, 13c-l, 13c-2, is relatively large with respect to the coupling between any two secondary windings corresponding to different secondary transformer ports. As a result, the leakage inductance associated with the primary transformer port may be relatively low with respect to the leakage inductances associated with each of the secondary transformer ports.

Here, it is noted that Figure 5 is only an example of a winding arrangement leading to an asymmetrical leakage inductance distribution, and various other winding arrangements that provide an asymmetric leakage inductance distribution are envisaged. For example, the windings corresponding to a same transformer port need not be interleaved and may instead be arranged adjacent to one another. Furthermore, primary windings 12-1, 12-2 and secondary windings 13a-l, 13a-2, 13b- 1 , 13b-2, 13c-l, 13c-2 need not have same dimensions or a same number of windings.

In the above, the present disclosure has been explained using detailed embodiments thereof. However, it should be appreciated that the disclosure is not limited to these embodiments and that various modifications are possible without deviating from the scope of the present disclosure as defined by the appended claims.