Bridge Circuit and Energy Conversion System
The bridge circuit addresses the challenge of high current handling by using magnetically coupled filter chokes and phase-shifted potentials to reduce relay weight and cost, achieving efficient current distribution and compliance with safety regulations.
Patent Information
- Application Number
- JP2025501310
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-07-22
- Filing Date
- 2023-07-12
- Publication Date
- 2025-07-17
AI Technical Summary
Existing bridge circuits face challenges in reducing material costs and weight due to the need for large, heavy relays to handle high currents, which are required by safety regulations, especially when converting large outputs.
A bridge circuit design with magnetically coupled filter chokes and independently operable relay contacts, allowing for phase-shifted potentials and reduced current load on relays, enabling the use of lighter and more cost-effective relays.
The design reduces relay weight and cost by evenly distributing current load, allowing for lighter and more cost-effective relay implementation while meeting safety standards.
Smart Images
Figure 2025523001000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a bridge circuit for supplying an alternating current to a phase terminal and an energy conversion system including such a bridge circuit.
Background Art
[0002] When converting direct current to alternating current or alternating current to direct current, a bridge module is used in which the potential present at the direct current terminals of the bridge module is provided in a manner that is clocked by semiconductor switches at the phase terminals of the bridge module. In this case, in addition to the positive and negative potentials of the DC connection, it is desirable to be able to provide an additional intermediate potential that can be formed, for example, by a split intermediate circuit of the DC voltage connection. However, it is also known to generate an intermediate potential within the bridge module, for example, by means of a so-called flying capacitor topology. The higher the intermediate potential that can be provided at the output terminals of the bridge module, the smaller and lighter the filter connected downstream of the bridge module can be, and thus the cost efficiency can be improved.
[0003] Document DE102012107122A1 also discloses a bridge circuit for supplying an alternating current to a phase terminal, which can generate an additional intermediate potential via a filter connected downstream of the bridge module. The bridge module includes two bridge outputs that are clocked with an offset from each other. The filter includes two magnetically coupled filter chokes in each connection path, and the two bridge outputs are connected to a common phase terminal via these filter chokes. In this way, an inverter can be produced that realizes a high power density and weight reduction that are greatly influenced by the weight of the filter. Similar topologies with filter chokes in the individual connection paths between the plurality of bridge outputs and the common phase output are also disclosed in documents DE102016222001A1 and EP2136465A1, where the filter chokes are not magnetically coupled to each other.
[0004] The problem here is that when the output of the inverter or rectifier is large, the current supplied by the bridge module is high, and it is necessary to design a circuit breaker that shuts off the current from the bridge module through two relay contacts that can operate independently, which is required by safety regulations, according to the maximum current. Since large relays are disproportionately heavy compared to small relays, this leads to a significant cost and a large additional weight.
[0005] Therefore, an object of the present invention is to provide a bridge circuit for supplying or receiving an alternating current in a phase terminal or an energy conversion system while reducing material costs. SUMMARY OF THE INVENTION
[0006] This object is achieved by a bridge circuit having the configuration of independent claim 1. Further embodiments are described in conjunction with the configuration of the subclaims. Claim 11 relates to an energy conversion system provided with such a bridge circuit.
[0007] The bridge circuit according to the present invention functions to supply an alternating current to a phase terminal, a first DC terminal and a second DC terminal for connecting a DC power supply or a DC load, an intermediate circuit, a bridge having a bridge switch, the bridge being configured to provide the potentials of the first DC terminal and the second DC terminal to a first bridge output and a second bridge output that are clocked independently of each other, and a first connection path extends between the first bridge output and the phase terminal, and a second connection path extends between the second bridge output and the phase terminal, each of the connection paths is provided with a filter choke on the bridge output side, and the filter chokes of the connection paths are magnetically coupled to each other, A circuit breaker with a plurality of relay contacts is arranged between the bridge output and the phase terminal, and at least one of the relay contacts is arranged in each separated part of the connection path.
[0008] The clocking of the bridge circuit is offset by the phase shift of the carriers of the two bridge outputs, usually a phase shift of half or a quarter of the switching period. Thereby, in addition to the potential of the bridge output, it is possible to provide a further potential at the phase terminal whose value is located between the actual values of the bridge output potential. As a result, the bridge circuit can operate with lower losses and / or the line filter of the bridge circuit can be designed more cost-effectively.
[0009] In a preferred embodiment, the bridge is arranged and designed to provide, at each of the bridge outputs, in addition to the potential present at the first DC terminal and the potential present at the second DC terminal, a third potential level formed from the potential of the DC terminals. The potential is formed by a divided intermediate circuit and can be taken at the center point of this divided intermediate circuit. However, it is also conceivable to use a capacitor, a so-called flying capacitor, arranged between the bridge switches of the bridge, and the flying capacitor can be used to shift the voltage of the potential present at one of the bridge outputs with respect to one of the potentials of the DC terminals. Similarly, additional potential levels can also be formed by a combination of a bridge with flying capacitors formed and provided at the bridge output by a multi-divided intermediate circuit or by appropriate clocking of the bridge switches and the divided intermediate circuit. For example, in one embodiment, the bridge can be arranged and designed to provide five potential levels formed from the potential of the DC terminals at each of the bridge outputs.
[0010] During the operation of the bridge circuit, by using known balance control of the bridge current, the current is distributed approximately evenly between the connection paths, so that the current load on the relay contacts of the circuit breaker is halved, and a more cost-effective and lightweight relay type can be used as the circuit breaker. Preferably, the distributed relay contacts of the circuit breaker are arranged in different relay housings, enabling better cooling of each relay contact, thereby further reducing the required installation space. Compared with this, the additional cost and additional weight due to additional voltage measurements at capacitors 16a and 16b, and in some cases 46a and 46b, are negligibly small.
[0011] If there is a galvanic insulation plane, for example formed by a transformer, on the DC side or the AC side of the bridge circuit, no further relay contacts are required. Otherwise, safety regulations require that two independently operable relay contacts of the circuit breaker be arranged in series between each of the bridge outputs and the phase terminals. In a preferred embodiment, in this case, the two relay contacts are arranged at separated parts of the connection path. That is, each relay contact needs to be designed considering only the maximum current flowing through its respective connection path. An application example of a bridge circuit without two series relay contacts is a DC charging device for electric vehicles where such a galvanic insulation plane usually exists.
[0012] In a further embodiment, the common relay contact of the circuit breaker is arranged at the common part of the first connection path and the second connection path. This means that the full phase current is loaded on this common relay contact, but even if both connection paths are disconnected from the phase terminal by open relay contacts, it is also possible to measure electrical variables such as voltage or current at the point between the series relay contacts of the two connection paths using a common measuring device at the common part of the first connection path and the second connection path.
[0013] Alternatively or additionally, it is also possible to arrange a further filter having a further filter choke and a further filter capacitor in the common portion of the first connection path and the second connection path, in which case the relay contacts of the circuit breaker are arranged between the further filter and the phase terminal.
[0014] In order to effectively suppress the non-main power supply frequency components of the supplied alternating current, it is preferable to connect a filter capacitor to each of the connection paths between the filter choke and the circuit breaker, and this filter capacitor is connected to the first DC terminal, the second DC terminal, or the center point by a further terminal. Connecting to the center point has the advantage of reducing the voltage load on the filter capacitor.
[0015] Further suppression of the non-main power supply frequency components of the supplied or received alternating current can be achieved by arranging a second filter having a second filter choke and a second filter capacitor in at least one, preferably both, of the first and second connection paths between the filter choke and the circuit breaker. This generates a so-called LCLC filter.
[0016] The DC power supply or the DC load can also be connected via an additional power electronic converter, for example, for increasing or decreasing the DC voltage.
[0017] In a further aspect of the present invention, the energy conversion system comprises a bridge circuit according to the present invention. The energy conversion system can be connected to an AC voltage grid in a single-phase or polyphase manner. In the case of a polyphase connection, a bridge circuit according to the present invention can be provided for each of the phases. The energy conversion system preferably comprises a photovoltaic power generation device or a battery as a DC power supply for supplying the converted alternating current. However, the energy conversion system can also have a DC load in addition to or instead of the DC power supply, or can be designed to connect such a load. For example, the energy conversion system can be a DC charging device for an electric vehicle.
Brief Description of the Drawings
[0018] The present invention will be described with reference to the following drawings.
[0019]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Modes for Carrying Out the Invention
[0020] FIG. 1 shows an embodiment of a bridge circuit 10 according to the present invention having DC terminals DC + and DC - to which a DC power supply or a DC load can be connected. An intermediate circuit in which two intermediate circuit capacitors 17 are connected in series is arranged between the DC terminals DC + and DC -, and a center point M provides the DC voltage of the bridge 11 together with the DC terminals DC + and DC -. The bridge 11 has two bridge outputs 18a and 18b, and at these outputs, the bridge 11 provides voltages that are formed from the DC voltage and are clocked independently of each other.
[0021] A connection path 15a extends from the first bridge output 18a to the phase terminal AC of the bridge circuit 10. A first filter choke 12a is arranged on the bridge output side, and a relay contact 14a of a circuit breaker 13 is arranged on the phase terminal side. A first filter capacitor 16a branches between the first filter choke 12a and the circuit breaker 13 and is connected to the center point M. The second connection path 15b is similarly configured and extends from the bridge output 18b to the phase terminal AC of the bridge circuit 10. A second filter choke 12b is arranged on the bridge output side, and a further relay contact 14b of the circuit breaker 13 is arranged on the phase terminal side. A second filter capacitor 16b branches between the second filter choke 12b and the circuit breaker 13 and is also connected to the center point M. The filter capacitors 16a and 16b can alternatively be connected to one of the DC terminals DC + and DC -.
[0022] The first filter choke 12a and the second filter choke 12b are magnetically coupled to each other and in particular have a common core. Since relay contacts 14a, 14b are arranged in each of the connection paths 15a, 15b, the circuit breaker 13 can design its energization capacity in consideration of only the maximum current that can flow in the respective connection paths 15a, 15b. Thereby, the circuit breaker 13 can be designed cost-effectively. However, for safety reasons, it is also conceivable to form each of the relay contacts 14a, 14b by two series contacts that can be operated separately from each other, for example, by assigning them to different relays. However, as already described above, for example, when a galvanic insulation plane is connected upstream or downstream of the bridge circuit, a single relay contact in each connection path can also meet the applicable safety standards. This also applies to the embodiments described below.
[0023] Unlike the circuit shown in FIG. 1, the bridge circuit 10 shown in FIG. 2 has a circuit breaker 13 here that consists merely of three relay contacts 14, one of which is arranged in the common part of the connection paths 15a, 15b, and the other relay contacts 14 are arranged in the parts of the connection paths 15a, 15b that run separately from each other. As a result, the relay contact 14 arranged in the common part of the connection paths 15a, 15b needs to be designed in accordance with the maximum current of the phase terminals AC, which can only compensate for some of the drawbacks. However, at the same time, this arrangement of the relay contacts 14 enables the electrical variables (for example, voltage) between the series arrangements of the relay contacts 14 to be detected using the same measuring device, so that the measuring device can be omitted if necessary. This detection may be required during the function test of the relay contacts, during the synchronization process of the alternating voltage provided by the bridge circuit before connecting to the AC voltage grid connected to the phase terminals, or during the normal power supply operation of the bridge circuit.
[0024] The bridge circuit 10 in FIG. 3 has the same arrangement of relay contacts 14 as shown in FIG. 2, and further, an additional filter is arranged at the common portion of the connection paths 15a, 15b between the series relay contacts 14. The additional filter includes another filter choke 32 and another filter capacitor 36, which are also connected to the center point M.
[0025] The bridge circuit 10 in FIG. 4 again adopts the arrangement of relay contacts 14 as shown in FIG. 1, and further, in each of the connection paths 15a, 15b, a second filter is arranged between the magnetically coupled filter chokes 12a, 12b and the circuit breaker 13. In the first connection path 15a, the second filter is formed by a second filter choke 42a and a second filter capacitor 46a. In the second connection path 15b, the second filter is formed by a second filter choke 42b and a second filter capacitor 46b. The second filter chokes 42a, 42b of the first connection path 15a and the second connection path 15b are shown here as not being magnetically coupled, but they can also be magnetically coupled to each other. The additional filter suppresses the non-main power frequency components of the alternating current supplied by the bridge circuit 10 particularly effectively. In particular, when using the bridge circuit in a three-phase inverter or rectifier, the connection of the filter capacitors 46a and 46b to the center point M can be omitted.
[0026] As shown in FIG. 5, starting from the design of the bridge circuit 10 in FIG. 3, a second filter with second filter chokes 42a, 42b and second filter capacitors 46a, 46b in each of the connection paths 15a, 15b can be easily combined with an additional filter having an additional filter choke 32 and an additional filter capacitor 36 to further enhance the filtering effect of the non-main power frequency components of the supplied alternating current.
[0027] Also, FIG. 5 shows a galvanic insulation plane 50, which is, for example here, a transformer arranged at the common part of the first connection path and the second connection path. Thereby, without the need to provide two series-connected independently operable relay contacts of the circuit breaker 13 in each of the connection paths, all safety requirements regarding separation from the connected network can be satisfied. Instead, it is sufficient to have one relay contact 14 in each of the connection paths 15a, 15b. Instead of the AC-side arrangement of the galvanic insulation plane 50, a DC-side arrangement, for example by a galvanic insulation DC / DC converter (not shown) connected upstream of the bridge circuit 10, can also satisfy the safety requirements without series relay contacts. Similarly, other embodiments can also be designed to comply with safety by providing a galvanic insulation plane 50 having one relay contact in each of the connection paths 15a, 15b. As an example where galvanic insulation between the main power supply and the DC terminals is usually required even when the circuit breaker is closed, a DC charging device such as an electric vehicle can be mentioned. In this case, to satisfy the safety requirements, it is sufficient to have one relay contact 14 in each of the connection paths 15a, 15b.
[0028] FIG. 6 shows an energy conversion system based on the bridge circuit 10 according to the present invention for supplying single-phase alternating current to an AC voltage grid 61 connected to the energy conversion system. The structure of the bridge circuit 10 corresponds to the embodiment shown in FIG. 1, but it can also be designed according to other embodiments of the bridge circuit according to the present invention. The power generation device 60 (particularly, a solar power generation device) of the energy conversion system is connected to the DC terminals DC +, DC - of the bridge circuit 10. The phase terminals of the bridge circuit 10 are connected to the phase conductor L of the AC voltage grid 61. The neutral conductor N of the AC voltage grid is also connected to the center point M of the bridge circuit 10 via two series relay contacts of the circuit breaker 13.
[0029] The polyphase supply of alternating current to an AC voltage grid can also be easily implemented with the aid of a bridge circuit. In this case, the bridge circuit 10 according to the invention is assigned to each phase of the AC voltage grid and is connected to the respective phase conductors of the AC voltage grid by its phase terminals. The DC terminals DC+ and DC- are usually connected in parallel, but it is also possible to connect separate power generation devices to each bridge circuit.
[0030] Figures 7a to 7k show in a non-exhaustive list and in no particular order of preference the possible switch arrangements of the bridge that can be used in the bridge circuit according to the invention.
[0031] The switch arrangement of Figure 7a shows a half-bridge of two so-called flying capacitors connected in parallel. In this half-bridge, in addition to the potentials of the DC terminals DC+ and DC-, a third potential shifted by the capacitor voltage can be provided independently of each other to the bridge outputs 18a and 18b via the capacitors arranged in the bridge.
[0032] However, as shown in Figure 7b, it is also conceivable to arrange two simple half-bridges, each with two switches, in parallel between the DC terminals DC+ and DC- and to connect the bridge outputs 18a and 18b of the two half-bridges to the phase terminals via one of the connection paths. In the switch arrangements of Figures 7a and 7b, a split intermediate circuit is not required and thus no connection to its center point is necessary.
[0033] In contrast, in the switch arrangements of Figures 7c to 7k, since there are terminals at the center point M of the intermediate circuit designed as a split intermediate circuit, at the bridge outputs 18a and 18b it is possible to provide at least three different potentials in a clocked manner using the potentials of the DC voltage terminals DC+ and DC- and the center point M.
[0034] Figure 7c shows two so-called BSNPC (bipolar switch neutral point clamp) bridges connected in parallel, and this bridge can also be used, and it also requires connection to the center point of the divided intermediate circuit. As shown in Figure 7d, even when the switches connected to the DC terminals DC+ and DC- are replaced with diodes, the bridge circuit can be used as a rectifier to supply power to the DC load.
[0035] Figure 7e shows two so-called NPC bridges (neutral point clamp bridges) connected in parallel, and this bridge can also be used, and it also requires connection to the center point of the divided intermediate circuit.
[0036] Figure 7f shows two so-called ANPC bridges (active neutral point clamp bridges) connected in parallel, and this bridge can also be used, and it also requires connection to the center point of the divided intermediate circuit. Capacitor 17 is optional and can be omitted when the clocking method is changed.
[0037] Figure 7g shows another bridge circuit, and this bridge circuit can also be used, and it also requires connection to the center point of the divided intermediate circuit. As shown in Figure 7h, even when the switches connected to the DC terminals DC+ and DC- are replaced with diodes, the bridge circuit can be used as a rectifier to supply power to the DC load. Here too, capacitor 17 is optional and can be omitted when an appropriate clocking method is used.
[0038] Figures 7i, 7j, and 7k show three further bridge circuits, and these bridge circuits can also be used, and they also require connection to the center point of the divided intermediate circuit. In contrast to the circuits of Figures 7a - 7h, here five potentials can be provided at the bridge outputs 18a and 18b.
[0039] Regardless of the type of switch shown in FIGS. 7a - 7k, any of an IGBT, MOSFET (both preferably as silicon or silicon carbide switches), HEMT, or GIT switch (both preferably as gallium nitride switches) can generally be used at any position in a bridge circuit. Other self - commuting switches are also conceivable for use within the bridge.
Description of Symbols
[0040] 10 Bridge circuit 11 Bridge 12a, 12b Filter choke 13 Circuit breaker 14, 14a, 14b Relay contact 15a, 15b Connection path 16a, 16b, 16c Filter capacitor 17 Intermediate circuit capacitor 18a, 18b Bridge output 32 Filter choke 36 Filter capacitor 42a, 42b Filter choke 46a, 46b Filter capacitor 50 Galvanic insulation plane 60 Power generation device 61 AC voltage grid DC +, DC - DC terminals M Center point AC Phase terminal L Phase conductor N Neutral conductor
Claims
1. A bridge circuit (10) for supplying an alternating current to a phase terminal (AC), comprising: a first DC terminal (DC+) and a second DC terminal (DC−) for connecting a DC power source or a DC load; an intermediate circuit (17); a bridge (11) having bridge switches, the bridge (11) being configured to provide the potentials of the first DC terminal (DC+) and the second DC terminal (DC−) to a first bridge output (18a) and a second bridge output (18b) that are clocked independently of each other; and a first connection path (15a) extends between the first bridge output (18a) and the phase terminal (AC), and a second connection path (15b) extends between the second bridge output (18b) and the phase terminal (AC); each of the connection paths (15a, 15b) includes filter chokes (12a, 12b) on the bridge output side, and the filter chokes (12a, 12b) of the connection paths (15a, 15b) are magnetically coupled to each other, in the bridge circuit (10); a circuit breaker (13) having a plurality of relay contacts (14, 14a, 14b) is disposed between the bridge outputs (18a, 18b) and the phase terminal (AC), and at least one of the relay contacts (14, 14a, 14b) is disposed in a separate portion of each of the connection paths (15a, 15b), characterized by the bridge circuit (10).
2. The bridge circuit (10) according to claim 1, wherein the bridge (11) is arranged and designed to provide three potential levels formed from the potentials of the DC terminals (DC+, DC−) to each of the bridge outputs (18a, 18b).
3. The bridge circuit (10) according to claim 1, wherein the bridge (11) is arranged and designed to provide five potential levels formed from the potentials of the DC terminals (DC+, DC−) to each of the bridge outputs (18a, 18b).
4. The bridge circuit (10) according to any one of claims 1 to 3, wherein two independently operable relay contacts (14, 14a, 14b) of the circuit breaker (13) are arranged in series between each of the bridge outputs (18a, 18b) and the phase terminal (AC).
5. In a separated portion of the connection path, two series relay contacts (14) of the circuit breaker (13) are arranged in each of the connection paths (15a, 15b), the bridge circuit (10) according to any one of claims 1 to 4.
6. The intermediate circuit (17) is a divided intermediate circuit having a center point (M), and the bridge (11) is configured to provide the potential existing at the first DC terminal (DC+), the second DC terminal (DC-), and the center point (M) to the first bridge output (18a) and the second bridge output (18b) in a manner that is clocked independently of each other. The bridge circuit (10) according to any one of claims 1 to 5.
7. In each of the connection paths (15a, 15b), filter capacitors (16a, 16b) are connected between the filter chokes (12a, 12b) and the circuit breaker (13), and the filter capacitors (16a, 16b) are connected to the first DC terminal (DC+), the second DC terminal (DC-), or the center point (M) by additional terminals. The bridge circuit (10) according to any one of claims 1 to 6.
8. Furthermore, in at least one of the first and second connection paths (15a, 15b), a second filter including a second filter choke (32, 42a, 42b) and a second filter capacitor (36, 46a, 46b) is arranged between the filter choke (12a, 12b) and the circuit breaker (13). The bridge circuit (10) according to any one of claims 1 to 7.
9. A common relay contact (14) of the circuit breaker (13) is arranged in a common portion of the first connection path (15a) and the second connection path (15b). The bridge circuit (10) according to any one of claims 1 to 8.
10. In the common portion of the first connection path (15a) and the second connection path (15b), an additional filter including an additional filter choke (32) and an additional filter capacitor (36) is arranged, and the common relay contact (14) of the circuit breaker (13) is arranged between the additional filter and the phase terminal (AC). The bridge circuit (10) according to claim 9.
11. An energy conversion system comprising the bridge circuit (10) according to any one of claims 1 to 10.