CONTROLLABLE TOPOLOGY DC-DC PARTIAL POWER CONVERTER

Abstract

The invention provides a controllable topology DC-DC partial power converter comprising: a galvanically isolated DC-DC converter having a positive input, a negative input, a positive output, and a negative output; a first DC voltage input electrically connected to said negative output of the DC-DC converter; an input reference; a first DC voltage output electrically connected to said positive output of the DC-DC converter; and an output reference electrically connected to said input reference and said negative input of the DC-DC converter; wherein said DC-DC partial power converter further comprises: a first switch arranged to selectively connect the first DC voltage input with said positive input of the DC-DC converter; and a second switch arranged to selectively connect said positive output of the DC-DC converter with said positive input of the DC-DC converter.

Description

CONTROLLABLE TOPOLOGY DC-DC PARTIAL POWER CONVERTER TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of the generation, conversion or distribution of electrical energy; more specifically to the field of the conversion of a DC input into a DC output and in particular provides a controllable topology DC-DC partial power converter. BACKGROUND OF THE INVENTION Within the field of energy conversion, partial power converters have recently gained prominence. It is generally known that partial power converters offer inherent advantages, such as reduced power losses, system size, and cost. The underlying principle is that power is divided 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 DC-DC converter's inputs to one of its outputs. There are two types of DC-DC partial power converters: Type I (shown in Fig. 1), where power division occurs on the input side of the converter, and Type II (shown in Fig. 2), where power division occurs on the output side (usually called the DC-link). Additionally, within each configuration (Type I or Type II), there is a boost configuration, in which the output voltage is higher than the input voltage, and a buck configuration, in which the output voltage is lower than the input voltage. Furthermore, for each configuration (Type I or Type II), there is a boost-buck configuration in which the output voltage can be either higher or lower than the input voltage. One of the characteristics of DC-DC partial power converters is that the relationship between the input and output voltage, and the power of the converter, depends only on the connection topology, but not on the type of DC-DC converter used. In the prior art, applications of DC-DC partial power converters are known for photovoltaic power generation and electromobility. For example, US patent 9,960,687 describes a Type I DC-DC partial power converter that uses a bidirectional DC-DC converter with galvanic isolation. The inventors of the present invention have discovered, however, that in some applications it is preferable to have a DC-DC partial power converter whose topology is controllable between Type I and Type II. A DC-DC partial power converter with both characteristics, however, is not described in the prior art. Consequently, a DC-DC partial power converter with a topology controllable between Type I and Type II is required. BRIEF DESCRIPTION OF THE INVENTION The present invention provides a controllable topology DC-DC partial power converter, characterized in that it comprises: a galvanically isolated DC-DC converter having a positive input, a negative input, a positive output, and a negative output; a first DC voltage input electrically connected to said negative output of said DC-DC converter; an input reference; a first DC voltage output electrically connected to said positive output of said DC-DC converter; and an output reference electrically connected to said input reference and said negative input of said DC-DC converter; wherein said DC-DC partial power converter further comprises: a first switch arranged to selectively connect the first DC voltage input with said positive input of said DC-DC converter;and a second switch arranged to selectively connect said positive output of said DC-DC converter with said positive input of said DC-DC converter; and wherein said DC-DC converter is bidirectional in power and bipolar in voltage. In a preferred embodiment, the partial power converter is characterized in that the first switch and the second switch are unidirectional switches. In a more preferred embodiment, the partial power converter is characterized in that each of the unidirectional switches consists of a field-effect transistor in antiparallel with a rectifier diode. In another preferred embodiment, the partial power converter is characterized in that said first switch and said second switch are bidirectional switches. In a further preferred embodiment, the partial power converter is characterized in that said DC-DC converter connected in partial configuration is selected from the group consisting of forward converters, push-pull converters, H-bridge converters, flyback converters, half-bridge converters, and Cuk converters. In another preferred embodiment, the partial power converter is characterized in that said DC-DC converter comprises a transformer having a primary and a secondary, a first H-bridge connected to the primary of said transformer, and a second H-bridge connected to the secondary of said transformer. OQQ / ηη / O7Γ>7 / Β / YILI BRIEF DESCRIPTION OF THE FIGURES Fig. 1 illustrates a prior art type I partial power converter. Fig. 2 illustrates a prior art type II partial power converter. Fig. 3 schematically illustrates an embodiment of the controllable topology partial power converter that is the subject of the present invention. Fig. 4 illustrates an example of an embodiment of the controllable topology partial power converter that is the subject of the present invention. Fig. 5 illustrates the interconnection of a plurality of DC-DC partial power converters according to the present invention in a series-input, series-output configuration. Fig. 6 illustrates the interconnection of a plurality of DC-DC partial power converters according to the present invention in a series configuration at the input, parallel at the output. Fig. 7 illustrates the interconnection of a plurality of DC-DC partial power converters according to the present invention in a configuration parallel to the input, series to the output. Fig. 8 illustrates the interconnection of a plurality of DC-DC partial power converters according to the present invention in a parallel-to-input, parallel-to-output configuration. DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail, with reference to the figures accompanying the present invention. In a first object of the present invention, as illustrated schematically in Figure 3, a controllable topology DC-DC partial power converter (1) is provided comprising, essentially: 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 said negative output (6) 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) and said negative input (4) of said DC-DC converter (2), wherein said DC-DC partial power converter (1) further comprises: a first switch (11) arranged to selectively connect first DC voltage input (7) with said positive input (3) of said DC-DC converter (2); and a second switch (12) arranged to selectively connect said positive output (5) of said DC-DC converter (2) with said positive input (3) of said DC-DC converter (2). Henceforth, for simplicity and without limiting the scope of the present invention, it shall be OQQ / ηη / Ω7Γ>7 / Β / YILI will refer to the controllable topology part-power DC-DC converter (1) that is the subject of the present invention as a part-power DC-DC converter (1). In the context of the present invention, a DC-DC converter shall be understood to mean a set of electrical and electronic components arranged in such a way that, in response to a continuous (DC) input signal, it generates a DC output signal. Typically, the relationship between the input voltage and the output voltage of a DC-DC converter is controlled by the ratio between the on-time and off-time of one or more switches that are part of said DC-DC converter. The DC-DC converter (2), which is part of the partial DC-DC power converter (1) that is the subject of the present invention, has two inputs which, in the context of the present invention and without limiting its scope, shall be referred to as the positive input (3) and the negative input (4). Furthermore, the DC-DC converter (2) has two outputs which, in the context of the present invention and without limiting its scope, shall be referred to as the positive output (5) and the negative output (6). The DC-DC converter (2) can be any type of DC-DC converter (2) possessing 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) can be a converter with galvanic isolation, which can 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 Cuk converters. Additionally, said DC-DC converter (2) is a bidirectional power converter and bipolar voltage converter. For example, and without limiting the scope of the present invention, the partial DC-DC power converter (1) that is the subject of the present invention can be used to connect a photovoltaic solar module to a DC bus. In another example, also without limiting the scope of the present invention, the partial DC-DC power converter (1) that is the subject of the present invention can be used to connect a battery to an inverter in an electric vehicle. In both cases, the DC-DC converter (2) is a bidirectional power converter. In the context of the present invention, without limiting its scope, a component with inputs and outputs, where power can flow from input to output or from output to input, shall be considered bidirectional in potential, or simply bidirectional. Furthermore, without limiting the scope of the present invention, a component shall be considered bipolar in voltage, or simply bipolar, when the voltage measured between a first and a second output of said component can be either positive or negative. 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 winding, a first H-bridge (22) connected to the primary winding of said transformer (21), and a second H-bridge (23) connected to the secondary winding of said transformer (21). Furthermore, said second H-bridge (23) is bidirectional and bipolar. The ratio of the number of turns in the primary and secondary windings of said transformer (21) does not limit the scope of the present invention. The partial DC-DC power converter (1) that is the subject of the present invention further comprises a first DC voltage input (7) electrically connected to the negative output (6) 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). In addition, the partial DC-DC power converter (1) that is the subject of the present invention comprises an input reference (8) and an output reference (10) electrically connected to said input reference (8) and to the negative input (4) of the DC-DC converter (2).Thus, for example and without limiting the scope of the present invention, the DC-DC partial power converter (1) that is the subject of the present invention allows the connection between two direct current devices, which are connected, respectively, to said first DC voltage input (7) and said input reference (8); and said first DC voltage output (9) and said output reference (10). As previously mentioned, the DC-DC partial power converter (1) of the present invention further comprises a set of switches (11, 12) that allow the topology of the DC-DC partial power converter (1) to be controlled between a Type I topology and a Type II topology. A first switch (11) is arranged to selectively connect the first DC voltage input (7) to the positive input (3) of the DC-DC converter (2). A second switch (12) is arranged to selectively connect the positive output (5) of said DC-DC converter (2) to the positive input (3) of said DC-DC converter. In the context of the present invention, the term "selective connection" refers to a connection controlled by the switching state of a switch. 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 established between the first DC voltage input (7) and the positive input (3) of the DC-DC converter (2). Conversely, when the first switch (11) is in the open position, the electrical connection between the first DC voltage input (7) and the positive input (3) of the DC-DC converter (2) is interrupted. Similarly, and without limiting the scope of the present invention, the electrical connection between the positive output (5) of the DC-DC converter (2) and the positive input (3) of the DC-DC converter is controlled by the switching state of the second switch (12). OQQ / ηη / Ω7Γ>7 / R / YIAI Furthermore, the nature of the first switch (11) and the second switch (12) does not limit the scope of the present invention. The first switch (11) and the second switch (12) may or may not be implemented in the same manner without limiting the scope of the present invention. In a preferred embodiment, without limiting the scope of the present invention, the first switch (11) and the second switch (12) may be unidirectional switches. This configuration is obtained, for example, without limiting the scope of the present invention, by placing a transistor in parallel with a rectifier diode. The 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, the transistor is a field-effect transistor, and the rectifier diode is connected in antiparallel to the source and drain of the field-effect transistor. However, in other preferred embodiments, the first switch (11) and second switch (12) may be bidirectional switches. This configuration can be achieved, for example, without limiting the scope of the present invention, by arranging two unidirectional switches in parallel, wherein these unidirectional switches allow current to flow in opposite directions. Furthermore, in this preferred embodiment, the two parallel-connected unidirectional switches must be controlled so that their switching state is the same at all times. As previously mentioned, the switching state of the first switch (11) and second switch (12) allows the topology of the DC-DC partial power converter of the present invention to be controlled between a Type I topology and a Type II topology. However, advantageously and without limiting the scope of the present invention, the DC-DC partial power converter (1) of the present invention has a third mode of operation, which shall be referred to, without limiting the scope of the present invention, as bypass. In this bypass configuration, the DC device connected to the first voltage input (7) and the first reference (8) is directly connected to the DC device connected to the first voltage output (9) and the second reference (10), regardless of the operation of the DC-DC converter (2). To bring the DC-DC partial power converter (1) that is the subject of the present invention into a type I topology, the first switch (11) must be kept closed and the second switch (12) open. In this way, the DC-DC partial power converter (1), which is schematically illustrated in Figure 3, will acquire the topology illustrated in Figure 1. To bring the DC-DC partial power converter (1) that is the subject of the present invention to a type II topology, the first switch (11) must be kept open and the second switch (12) closed. In this way, the DC-DC partial power converter (1), which is schematically illustrated in Figure 3, will acquire the topology illustrated in Figure 2. Finally, to bring the DC-DC partial power converter (1) that is the subject of the present invention to a bypass topology, said first switch (11) and said second switch (12) must be kept closed. According to the previous description, it is possible to obtain a DCDC partial power converter (1) whose topology is controllable between a type I, a type II and a bypass and which allows the connection of two direct current devices. Furthermore, in other preferred embodiments, without limiting the scope of the present invention, it is possible to provide other configurations for the interconnection between the DC devices. For this purpose, a plurality of DC-DC partial power converters (Ia, Ib, Ie), each according to the present invention, can be provided and connected according to the desired configuration. In a first embodiment, as illustrated in Figure 7 and without limiting the scope of the present invention, the plurality of DC-DC partial power converters (la, Ib, le) can be connected in an input-to-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 DC-DC partial power converter (la) of the plurality. The negative DC terminal of the first DC device is connected to the input reference (8c) of the last DC-DC partial power converter (le).Similarly, the positive DC terminal of the second DC device is connected to the first DC voltage output (9a) of the first DC-DC partial power converter (la), and the negative DC terminal of the second DC device is connected to the output reference (10c) of the last DC-DC partial power converter (le). In turn, the input reference (8a) of the first DC-DC partial power converter (la) is connected to the first voltage input (7b) of the second DC-DC partial power converter (Ib); the input reference (8b) of the second DC-DC partial power converter (Ib) to the first voltage input (7c) of the third DC-DC partial power converter (le), and so on until all the inputs of the plurality of DC-DC partial power converters (la, Ib, 1c) are connected.Similarly, the output reference (10a) of the first DC-DC partial power converter (la) is connected to the first voltage output (9b) of the second DC-DC partial power converter (Ib); the output reference (8b) of the second DC-DC partial power converter (Ib) to the first voltage output (9c) of the third DC-DC partial power converter (le) and so on until all the outputs of the plurality of DC-DC partial power converters (la, Ib, le) are connected. In a second example of implementation, as illustrated in Figure 8 and without this limiting Within the scope of the present invention, said plurality of DC-DC partial power converters (la, Ib, le) can be connected in a series configuration at the input and in parallel at the output (ISOP, Input Series, Output Parallel). In this configuration, the positive DC terminal of the first DC device is connected to the first DC voltage input (7a) of the first DC-DC partial power converter (la) of the plurality. The negative DC terminal of the first DC device is connected to the input reference (8c) of the last DC-DC partial power converter (le).The positive DC terminal of the second DC device is connected to each of the first DC voltage outputs (9a, 9b, 9c) of the DC-DC partial power converters (la, Ib, le) that are part of this plurality, and the negative DC terminal of the second DC device is connected to each of the output references (10a, 10b, 10c) of the DC-DC partial power converters (la, Ib, le) that are part of this plurality. In turn, the input reference (8a) of the first DC-DC partial power converter (la) is connected to the first voltage input (7b) of the second DC-DC partial power converter (Ib). the input reference (8b) of the second DC-DC partial power converter (Ib) to the first voltage input (7c) of the third DC-DC partial power converter (le) and so on until all the inputs of the plurality of DC-DC partial power converters (la, Ib, le) are connected.In a third embodiment, as illustrated in Figure 9 and without limiting the scope of the present invention, the plurality of DC-DC partial power converters (Ia, Ib, Ie) can be connected in a parallel configuration at the input and in series at the output (IPOS, Input Parallel, Output Series). 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 DC-DC partial power converters (Ia, Ib, Ie) of the plurality. The negative DC terminal of the first DC device is connected to each of the input references (8a, 8b, 8c) of the DC-DC partial power converters (Ia, Ib, Ie) of the plurality.Furthermore, the positive DC terminal of the second DC device is connected to the first DC voltage output (9a) of the first DC-DC partial power converter (la), and the negative DC terminal of the second DC device is connected to the output reference (10c) of the last DC-DC partial power converter (le). In turn, the output reference (10a) of the first DC-DC partial power converter (la) is connected to the first voltage output (9b) of the second DC-DC partial power converter (Ib); the output reference (8b) of the second DC-DC partial power converter (Ib) to the first voltage output (9c) of the third DC-DC partial power converter (le), and so on until all the outputs of the plurality of DC-DC partial power converters (la, Ib, 1c) are connected. In a fourth embodiment, as illustrated in Figure 10 and without limiting the scope of the present invention, the plurality of DC-DC partial power converters (la, Ib, le) can 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 DC-DC partial power converters (la, Ib, le) of the plurality. The negative DC terminal of the first DC device is connected to each of the input references (8a, 8b, 8c) of the DC-DC partial power converters (la, Ib, le).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 DC-DC partial power converters (la, Ib, le) 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 DC-DC partial power converters (la, Ib, le) of said plurality. According to the description detailed above, it is possible to obtain a partial DC-DC power converter (1) whose topology is controllable by the switching state of said first switch (11) and second switch (12). It should be understood that the different options described for the technical characteristics of the DC-DC partial power converter (1) that is the subject of the present invention can be combined with each other, or with others known to a person normally versed in the subject, in any way provided without this limiting the scope of the present invention. The following are examples of embodiments of the present invention. It should be understood that these examples are intended to provide a better understanding of the invention but do not limit its scope. Furthermore, technical features described in different examples may be combined with each other, or with other features previously described, in any manner foreseen by a person skilled in the art, without limiting the scope of the present invention. Example 1: Use of the DC-DC partial power converter in battery arrays As illustrated schematically in Figure 4, the DC-DC partial power converter that is the subject of the present invention can be used to connect a group of cells or battery array (13) to a DC voltage line or bus (14). For this purpose, the positive (131) and negative (132) 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 DC-DC partial power converter (1). The positive (141) and negative (142) terminals of the DC voltage bus (14) are connected, respectively, to the first voltage output (9) and the output reference (10) of the DC-DC partial power converter (1). In addition, a capacitor is provided QQO I níllP7í\7 / B / YILI input (15) connecting the first voltage input (7) to the input reference (8) and an output capacitor (16) connecting the first voltage output (9) to the output reference (10). An output inductor (17) is also provided, connecting the positive output (5) of the DC-DC converter (2) to the first voltage output (9). In this embodiment, the DC-DC converter (2) is also bidirectional in power, allowing both charging and discharging of the battery (15). Example 2: Implementation of the partial DC-DC power converter in conjunction with a battery array Figure 4 further illustrates a schematic diagram of an implementation of the DC-DC partial power converter in conjunction with a battery array (13). The connections are made as described in Example 1. In this example, the DC-DC converter (2) is a galvanically isolated converter and includes a transformer (21) with a primary and a secondary winding. A first H-bridge (22), consisting of four unidirectional switches, is connected to the primary winding of the transformer (21), and a second H-bridge (23), consisting of four bidirectional switches, is connected to the secondary winding of the transformer (21). Additionally, an output inductor (17) is provided, connecting the positive output (5) of the DC-DC converter (2) to the first voltage output (9).

Claims

1. A controllable topology DC-DC partial power converter (1), CHARACTERIZED in that it comprises: 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 said negative output (6) 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) and said negative input (4) of said DC-DC converter (2); wherein said DC-DC partial power converter (1) further comprises: a first switch (11) arranged to selectively connect the first DC voltage input (7) with said positive input (3) of said DC-DC converter (2);and a second switch (12) arranged to selectively connect said positive output (5) of said DC-DC converter (2) with said positive input (3) of said DC-DC converter (2); and wherein said DC-DC converter (2) is bidirectional in power and bipolar in voltage.; 2. The partial power converter of claim 1, characterized in that said first switch (11) and said second switch (12) are unidirectional switches.

3. The partial power converter of claim 2, characterized in that each of said unidirectional switches is formed by a field-effect transistor in parallel with a rectifier diode.

4. The partial power converter of claim 1, characterized in that said first switch (11) and said second switch (12) are bidirectional switches.

5. The partial power converter of claim 1, characterized in that said part-power interconnected DC-DC converter (2) is selected from the group consisting of forward converters, push-pull converters, H-bridge converters, flyback converters, half-bridge converters, and Cuk converters.

6. The partial power converter of claim 1, characterized in that said DC-DC converter (2) comprises a transformer (21) having a primary and a secondary, a first H-bridge (22) connected to the primary of said transformer and a second H-bridge (23) connected to the secondary of said transformer (21).

Images