PART-POWER DC CONVERTER WITH CONTROLLED TOPOLOGY

Description

Technical field of invention

[0001] The present invention relates to the field of electrical power generation, conversion, or distribution; more specifically to the field of converting a DC input into a DC output, and in particular provides a partial power DC-DC converter with controllable topology.Background of the Invention

[0002] Within the field of power conversion, partial power converters have become relevant in recent times. In general, partial power converters are known to have intrinsic advantages, such as reduced power losses, system size and cost. The underlying principle is that power is split between a direct power link between the input and output, and a portion that is processed by a DC-DC converter. This is achieved by connecting one of the inputs of the DC-DC converter to one of the outputs of the same.

[0003] There are two types of partial power DC-DC converters, namely, type I (seen in FIG. 1), where the power splitting is performed on the input side of the partial power DC-DC converter, and type II (seen in FIG. 2), where the power splitting is performed on the output side of the partial power converter (usually referred to as DC-link). Additionally, within each configuration (type I or type II) there is a step-up configuration, in which the output voltage is higher than the input voltage, and a step-down configuration, in which the output voltage is lower than the input voltage.

[0004] One of the advantages of partial power DC-DC converters is that the relation between the input and output voltage depends only on the connection topology, but not on the type of DC-DC converter used.

[0005] In the prior art, applications of partial power DC-DC converters in photovoltaic electric power generation and electromobility are known. For example, document US 9,960,687 B2 describes a type I partial power DC-DC converter that uses a galvanically isolated bidirectional DC-DC converter. Another prior art document is the patent application with publication number US2016285374A1, which discloses a converter system that is designed to efficiently manage and convert electrical power. A further prior art document is the patent application with publication number US2017085090A1, which discloses a solar-powered airship designed to deliver supplies to remote areas where traditional roads and fuel sources are lacking. The airship uses a special power converter that efficiently manages energy from solar panels and batteries, allowing it to operate effectively even with limited resources.

[0006] The inventors of the present invention have discovered, however, that in some applications it is preferable to have a partial power DC-DC converter whose topology is controllable between a type I and a type II. A partial power DC-DC converter with both characteristics, however, is not described in the prior art. Accordingly, a partial power DC-DC converter whose topology is controllable between a type I and type II is required.Summary of the Invention

[0007] The present invention defines a partial power DC-DC converter with controllable topology, defined in the independent apparatus claim 1. The preferred embodiments are defined in the dependent claims 2-6.Brief description of the Figures

[0008] FIG. 1 illustrates a type I partial power converter of the prior art. FIG. 2 illustrates a type II partial power converter of the prior art. FIG. 3 schematically illustrates an embodiment of the partial power converter with controllable topology which is the subject matter of the present invention. FIG. 4 illustrates an application of the partial power converter with controllable topology which is the subject matter of the present invention in a photovoltaic electric power generation system. FIG. 5 illustrates an application of the partial power converter with controllable topology which is the subject matter of the present invention in an electrochemical electrical power generation system. FIG. 6 illustrates an example embodiment of the partial power converter with controllable topology that is the subject matter of the present invention. FIG. 7 illustrates the interconnection of a plurality of partial power DC-DC converters in accordance with the present invention in an input-series, output-series configuration. FIG. 8 illustrates the interconnection of a plurality of partial power DC-DC converters in accordance with the present invention in an input-series, output-parallel configuration. FIG. 9 illustrates the interconnection of a plurality of partial power DC-DC converters in accordance with the present invention in an input-parallel, output-series configuration. FIG. 10 illustrates the interconnection of a plurality of partial power DC-DC converters in accordance with the present invention in an input-parallel, output-parallel configuration. Detailed description of the invention

[0009] The present invention will be described below in detail, referring for this purpose to the figures accompanying the present application.

[0010] In a first subject matter of the present invention, as schematically illustrated in FIG. 3, a partial power DC-DC converter (1) with controllable topology is provided, comprising, essentially: a DC-DC converter (2) having a positive input (3), a negative input (4), a positive output (5), and a negative output (6); a first DC voltage input (7) electrically connected to said positive input (3) of said DC-DC converter (2); an input reference (8); a first DC voltage output (9) electrically connected to said positive output (5) of said DC-DC converter (2); and an output reference (10) electrically connected to said input reference (8). Said partial power DC-DC converter (1) additionally comprises: a first switch (11) arranged to selectively connect said positive input (3) to said negative output (6) of said DC-DC converter (2); a second switch (12) arranged to selectively connect said negative input (4) of said DC-DC converter (2) to said input reference (8); a third switch (13) arranged to selectively connect said negative output (6) of said DC-DC converter (2) to said output reference (10); and a fourth switch (14) arranged to selectively connect said positive output (5) to said negative input (4) of said DC-DC converter (2).

[0011] Hereinafter, for reasons of simplicity and without limiting the scope of the present invention, reference will be made to the partial power DC-DC converter (1) with controllable topology which is the subject of the present invention as a partial power DC-DC converter (1).

[0012] In the context of the present invention, a DC-DC converter will be understood as a set of electrical and electronic components arranged such that, in response to a continuous (DC) input signal, it generates a DC output signal. Normally, the relation between the input voltage and the output voltage of a DC-DC converter is controlled by the ratio between the opening time and the closing time of one or more switches forming part of said DC-DC converter.

[0013] The DC-DC converter (2) forming part of the partial power DC-DC converter (1) which is the subject matter of the present invention features two inputs which, in the context of the present invention and without limiting the scope of the present invention, will be referred to as positive input (3) and negative input (4). Furthermore, the DC-DC converter (2) features two outputs which, in the context of the present invention and without limiting the scope of the same, will be referred to as positive output (5) and negative output (6).

[0014] The DC-DC converter (2) may be any type of DC-DC converter (2) having galvanic isolation, without limiting the scope of the present invention. In a more preferred embodiment, without limiting the scope of the present invention, said DC-DC converter (2) may be a galvanically isolated converter which may be selected, for example and without limiting the scope of the present invention, from the group consisting of forward converters, push-pull converters, H-bridge converters, flyback converters, half bridge converters, and Ćuk converters. Additionally, said DC-DC converter (2) may be unidirectional or bidirectional without limiting the scope of the present invention. The unidirectional or bidirectional nature will depend, for example and without limiting the scope of the present invention, on the specific application given to the partial power DC-DC converter (1) which is the subject matter of the present invention.

[0015] For example, and without limiting the scope of the present invention, when the partial power DC-DC converter (1) which is the subject matter of the present invention is used to connect a solar photovoltaic module to a DC bus, said DC-DC converter (2) may be unidirectional. In another example, without limiting the scope of the present invention, when the partial power DC-DC converter (1) which is the subject matter of the present invention is used to connect a battery to an inverter in an electric vehicle, said DC-DC converter (2) may be a bidirectional converter.

[0016] In a preferred embodiment, without limiting the scope of the present invention, said DC-DC converter (2) may comprise a transformer (21) having a primary and a secondary, an H-bridge (22) connected to the primary of said transformer (21), and a bridge rectifier (23) connected to the secondary of said transformer (21). The relation between the number of turns of the primary and the secondary of said transformer (21) does not limit the scope of the present invention.

[0017] In a more preferred embodiment, without limiting the scope of the present invention, said transformer (21) may have a center-tapped secondary. In this last preferred embodiment, without limiting the scope of the present invention, said bridge rectifier (23) may be replaced by two rectifier diodes, each connected to one end of said secondary.

[0018] The partial power DC-DC converter (1) which is the subject matter of the present invention further comprises a first DC voltage input (7) electrically connected to the positive input (3) of the DC-DC converter (2); and a first DC voltage output (9) electrically connected to the positive output (5) of said DC-DC converter (2). Furthermore, the partial power DC-DC converter (1) which is the subject matter of the present invention comprises an input reference (8) and an output reference (10) electrically connected to said input reference (8). In this way, for example and without limiting the scope of the present invention, the partial power DC-DC converter (1) which is the subject matter of the present invention allows the connection between two DC devices, which are connected, respectively, to said first DC voltage input (7) and to said input reference (8); and to said first DC voltage output (9) and to said output reference (10).

[0019] As previously mentioned, the partial power DC-DC converter (1) which is the subject matter of the present invention additionally comprises a set of switches (11, 12, 13, 14) that allow to control the topology of the partial power DC-DC converter (1) which is the subject matter of the present invention between a type I topology and a type II topology. A first switch (11) is arranged to selectively connect the positive input (3) to the negative output (6) of the DC-DC converter (2). A second switch (12) is arranged to selectively connect said negative input (4) of said DC-DC converter (2) to the input reference (8). A third switch (13) is arranged to selectively connect said negative output (6) of said DC-DC converter (2) to the output reference (10). A fourth switch (14) is arranged to selectively connect said positive output (5) to said negative input (4) of said DC-DC converter (2).

[0020] In the context of the present invention, the term selective connection is to be understood as a connection which is controlled by the switching state of a switch. In this sense, for example and without limiting the scope of the present invention, when the first switch (11) is in the closed position, an electrical connection is provided between the positive input (3) and the negative output (6) of the DC-DC converter (2). In contrast, when the first switch (11) is in the open position, the electrical connection between the positive input (3) and the negative output (6) of said DC-DC converter (2) is interrupted. Similarly, without limiting the scope of the present invention, the electrical connection between the negative input (4) of said DC-DC converter (2) and the input reference (8) is controlled by the switching state of the second switch (12); the electrical connection between the negative output (6) of said DC-DC converter (2) and the output reference (10) is controlled by the switching state of the third switch (13); and the electrical connection between the positive output (5) and the negative input (4) of said DC-DC converter (2) is controlled by the switching state of the fourth switch (14).

[0021] Moreover, the nature of said first switch (11), said second switch (12), said third switch (13), and said fourth switch (14) does not limit the scope of the present invention. Said first switch (11), second switch (12), third switch (13), and fourth switch (14) may or may not be implemented in the same manner without limiting the scope of the present invention.

[0022] In a preferred embodiment, without limiting the scope of the present invention, said first switch (11), said second switch (12), said third switch (13), and said fourth switch (14) may be unidirectional switches. Said configuration may be obtained, for example and without limiting the scope of the present invention, by arranging a transistor in parallel with a rectifier diode. Said transistor may be a bipolar transistor or a field effect transistor without limiting the scope of the present invention. In a preferred embodiment, without limiting the scope of the present invention, said transistor is a field effect transistor and said rectifier diode is connected anti parallel to the source and to the drain of said field effect transistor.

[0023] However, in other preferred embodiments, said first switch (11), second switch (12), third switch (13), said fourth switch (14) may be bidirectional switches. Said configuration may be obtained, for example and without limiting the scope of the present invention, by arranging two unidirectional switches parallel to each other, wherein said unidirectional switches allow current flow in directions opposite to each other. Furthermore, in this preferred embodiment, said two unidirectional switches connected in parallel must be controlled in such a way that their switching state is the same at all times.

[0024] As previously mentioned, the switching state of said first switch (11), second switch (12), third switch (13), and fourth switch (14) make it possible to control the topology of the partial power DC-DC converter which is the subject matter of the present invention between a type I topology and a type II topology. However, advantageously and without limiting the scope of the present invention, the partial power DC-DC converter (1) which is the subject of the present invention has a third mode of operation which will be referred to, without limiting the scope of the present invention, as bypass. In said bypass configuration, the DC device, which is connected to the first voltage input (7) and to the first reference (8), is directly connected to the DC device that is connected to the first voltage output (9) and to the second reference (10), independently of the operation of the DC-DC converter (2).

[0025] In order to bring the partial power DC-DC converter (1) which is the subject matter of the present invention to a type I topology, said first switch (11) and said second switch (12) must be kept closed, while keeping open said third switch (13) and said fourth switch (14). In this way, the partial power DC-DC converter (1), which is schematically illustrated in FIG. 3, will acquire the topology illustrated in FIG. 1.

[0026] In order to bring the partial power DC-DC converter (1) which is the subject matter of the present invention to a type II topology, said first switch (11) and said second switch (12) must be kept open, while keeping closed said third switch (13) and said fourth switch (14). In this way, the partial power DC-DC converter (1), schematically illustrated in FIG. 3, will acquire the topology illustrated in FIG. 2.

[0027] Finally, in order to bring the partial power DC-DC converter (1) which is the subject matter of the present invention into a bypass topology, said first switch (11) must be kept closed, while keeping open said second switch (12), said third switch (13), and said fourth switch (14).

[0028] According to the previous description, it is possible to obtain a partial power DC-DC converter (1) whose topology is controllable between a type I, a type II, and a bypass topology, and which allows the connection of two DC devices.

[0029] Furthermore, in other preferred embodiments and without limiting the scope of the present invention, it is possible to provide other configurations for the interconnection between DC devices. To this end, a plurality of partial power DC-DC converters (1a, 1b, 1c), each according to the present invention, can be arranged and connected according to the desired configuration.

[0030] In a first exemplary embodiment, as illustrated in FIG. 7 and without limiting the scope of the present invention, said plurality of partial power DC-DC converters (1a, 1b, 1c) may be connected in an Input-Series, Output-Series (ISOS) configuration. In this configuration, the positive DC terminal of the first DC device is connected to the first DC voltage input (7a) of the first partial power DC-DC converter (1a) of the plurality. On its part, the negative DC terminal of the first DC device is connected to the input reference (8c) of the last partial power DC-DC converter (1c). Similarly, the positive DC terminal of the second DC device is connected to the first DC voltage output (9a) of the first partial power DC-DC converter (1a) and the negative DC terminal of the second DC device is connected to the output reference (10c) of the last partial power DC-DC converter (1c). In turn, the input reference (8a) of the first partial power DC-DC converter (1a) is connected to the first voltage input (7b) of the second partial power DC-DC converter (1b); the input reference (8b) of the second partial power DC-DC converter (1b) to the first voltage input (7c) of the third partial power DC-DC converter (1c), and so on until all inputs of the plurality of partial power DC-DC converters (1a, 1b, 1c) are connected. Similarly, the output reference (10a) of the first partial power DC-DC converter (1a) is connected to the first voltage output (9b) of the second partial power DC-DC converter (1b); the output reference (8b) of the second partial power DC-DC converter (1b) to the first voltage output (9c) of the third partial power DC-DC converter (1c), and so on until all outputs of the plurality of partial power DC-DC converters (1a, 1b, 1c) are connected.

[0031] In a second exemplary embodiment, as illustrated in FIG. 8 and without limiting the scope of the present invention, said plurality of partial power DC-DC converters (1a, 1b, 1c) may be connected in an Input-Series, Output-Parallel (ISOP) configuration. In this configuration, the positive DC terminal of the first DC device is connected to the first DC voltage input (7a) of the first partial power DC-DC converter (1a) of the plurality. On its part, the negative DC terminal of the first DC device is connected to the input reference (8c) of the last partial power DC-DC converter (1c). On the other hand, the positive DC terminal of the second DC device is connected to each of the first DC voltage outputs (9a, 9b, 9c) of the partial power DC-DC converters (1a, 1b, 1c) forming part of said plurality, and the negative DC terminal of the second DC device is connected to each of the output references (10a, 10b, 10c) of the partial power DC-DC converters (1a, 1b, 1c) forming part of said plurality. In turn, the input reference (8a) of the first partial power DC-DC converter (1a) is connected to the first voltage input (7b) of the second partial power DC-DC converter (1b); the input reference (8b) of the second partial power DC-DC converter (1b) to the first voltage input (7c) of the third partial power DC-DC converter (1c), and so on until all inputs of the plurality of partial power DC-DC converters (1a, 1b, 1c) are connected.

[0032] In a third exemplary embodiment, as illustrated in FIG. 9 and without limiting the scope of the present invention, said plurality of partial power DC-DC converters (1a, 1b, 1c) may be connected in an Input-Parallel, Output-Series (IPOS) configuration. In this configuration, the positive DC terminal of the first DC device is connected to each of the first DC voltage inputs (7a, 7b, 7c) of the partial power DC-DC converters (1a, 1b, 1c) of the plurality. On its part, the negative DC terminal of the first DC device is connected to each of the input references (8a, 8b, 8c) of the partial power DC-DC converters (1a, 1b, 1c) of said plurality. On the other hand, the positive DC terminal of the second DC device is connected to the first DC voltage output (9a) of the first partial power DC-DC converter (1a) and the negative DC terminal of the second DC device is connected to the output reference (10c) of the last partial power DC-DC converter (1c). In turn, the output reference (10a) of the first partial power DC-DC converter (1a) is connected to the first voltage output (9b) of the second partial power DC-DC converter (1b); the output reference (8b) of the second partial power DC-DC converter (1b) to the first voltage output (9c) of the third partial power DC-DC converter (1c), and so on until all outputs of the plurality of partial power DC-DC converters (1a, 1b, 1c) are connected.

[0033] In a fourth exemplary embodiment, as illustrated in FIG. 10 and without limiting the scope of the present invention, said plurality of partial power DC-DC converters (1a, 1b, 1c) may be connected in an Input-Parallel, Output-Parallel (IPOP) configuration. In this configuration, the positive DC terminal of the first DC device is connected to each of the first DC voltage inputs (7a, 7b, 7c) of the partial power DC-DC converters (1a, 1b, 1c) of the plurality. On its part, the negative DC terminal of the first DC device is connected to each of the input references (8a, 8b, 8c) of the partial power DC-DC converters (1a, 1b, 1c). Similarly, the positive DC terminal of the second DC device is connected to each of the first DC voltage outputs (9a, 9b, 9c) of the partial power DC-DC converters (1a, 1b, 1c) of said plurality, and the negative DC terminal of the second DC device is connected to each of the output references (10a, 10b, 10c) of the partial power DC-DC converters (1a, 1b, 1c) of said plurality.

[0034] According to the previously detailed description, it is possible to obtain a partial power DC-DC converter (1) whose topology is controllable by means of the switching state of said first switch (11), second switch (12), third switch (13), and fourth switch (14).

[0035] It should be understood that the various options described for the technical characteristics of the partial power DC-DC converter (1) which is the subject matter of the present invention may be combined with each other, or with others known to a person ordinarily skilled in the art, in any manner envisaged without limiting the scope of the present invention.

[0036] Examples of embodiments of the present invention will be described below. It should be understood that said examples of embodiments are intended to provide a better understanding of the invention and do not limit the scope of the same. Additionally, technical features described in different examples may be combined with each other, or with others previously described, in any manner envisioned by a person ordinarily skilled in the art without limiting the scope of the present invention.Example 1: Use of the partial power DC-DC converter in solar photovoltaic modules

[0037] As schematically illustrated in FIG. 4, the partial power DC-DC converter that is the subject matter of the present invention can be used to connect a solar photovoltaic module (15) to a DC voltage line or bus (16). For this purpose, each of the positive (151) and negative (152) terminals of said solar photovoltaic module are connected to the first voltage input (7) and the input reference (8), respectively, of the partial power DC-DC converter (1). In turn, the positive (161) and negative (162) terminals of the DC voltage bus (16) are connected, respectively, to the first voltage output (9) and the output reference (10) of the partial power DC-DC converter (1). In addition, an input capacitor (17) connecting the first voltage input (7) to the input reference (8) and an output capacitor (18) connecting the first voltage output (9) to the output reference (10) are provided. In this exemplary embodiment, in addition, the DC-DC converter (2) is unidirectional in power.Example 2: Use of the partial power DC-DC converter in battery arrays

[0038] As schematically illustrated in FIG. 5, the partial power DC-DC converter that is the subject matter of the present invention can be used to connect a group of cells or battery array (19) to a DC voltage line or bus (16). For this purpose, each of the positive (191) and negative (192) terminals of said group of cells or battery array are connected to the first voltage input (7) and the input reference (8), respectively, of the partial power DC-DC converter (1). In turn, the positive (161) and negative (162) terminals of the DC voltage bus (16) are connected, respectively, to the first voltage output (9) and the output reference (10) of the partial power DC-DC converter (1). In addition, an input capacitor (17) connecting the first voltage input (7) to the input reference (8) and an output capacitor (18) connecting the first voltage output (9) to the output reference (10) are provided. In this exemplary embodiment, in addition, the DC-DC converter (2) is bidirectional in power, which allows both charging and discharging of the battery (19).Example 3: Implementation of the partial power DC-DC converter in conjunction with a solar photovoltaic module

[0039] FIG. 6 illustrates a schematic diagram of an implementation of the partial power DC-DC converter in conjunction with a solar photovoltaic module. The connections are made as described in Example 1.

[0040] In this example, the DC-DC converter (2) is a galvanically isolated converter and includes a transformer (21) having a primary and a secondary. An H-bridge (22), consisting of four unidirectional switches, is connected to the primary of the transformer (21) and a bridge rectifier (23) is connected to the secondary of the transformer (21). In addition, an input inductor (20) is provided which connects the first voltage input (7) to the positive input (3) of the DC-DC converter (2).

Claims

1. A partial power DC-DC converter (1) with controllable topology, comprising: - a galvanically isolated DC-DC converter (2) having a positive input (3), a negative input (4), a positive output (5), and a negative output (6); - a first DC voltage input (7) electrically connected to the positive input (3) of the galvanically isolated DC-DC converter (2); - an input reference (8); - a first DC voltage output electrically (9) connected to the positive output (5) of the galvanically isolated DC-DC converter (2); and - an output reference (10) electrically connected to the input reference; characterized in that the partial power DC-DC converter (2) further comprises: - a first switch (11) arranged to selectively connect the positive input (3) to the negative output (6) of the galvanically isolated DC-DC converter (2); - a second switch (12) arranged to selectively connect the negative input (4) of the galvanically isolated DC-DC converter (2) to the input reference (8); - a third switch (13) arranged to selectively connect the negative output (6) of the galvanically isolated DC-DC converter (2) to the output reference (10); and, - a fourth switch (14) arranged to selectively connect the positive output (5) to the negative input (4) of the galvanically isolated DC-DC converter (2).

2. The partial power converter of claim 1, wherein the first switch (11), the second switch (12), the third switch (13), and the fourth switch (14) are unidirectional switches.

3. The partial power converter of claim 1, wherein the first switch (11), the second switch (12), the third switch (13), and the fourth switch (14) are bidirectional switches.

4. The partial power converter of claim 1, wherein the galvanically isolated DC-DC converter (2) is a DC-DC converter selected from the group consisting of a forward converter, a push-pull converter, a H-bridge converter, a flyback converter, a half bridge converter, and a Ćuk converter.

5. The partial power converter of claim 1, wherein the galvanically isolated DC-DC converter (2) comprises a transformer (21) having a primary and a secondary, an H-bridge (22) connected to the primary of the transformer, and a bridge rectifier (23) connected to the secondary of the transformer.

6. The partial power converter of claim 5, wherein the transformer (21) has a center-tapped secondary.