Circuit configuration for single-phase or three-phase mains connection with variable input voltage

Abstract

The invention relates to the operation and a circuit arrangement (1) for a variable mains connection (single-phase / three-phase) with respect to the input voltage, which is connected to the neutral conductor (N) of the input AC voltage source via a connecting line (10) by means of a center tap (M) between capacitors (C).

Description

Technical Field

[0001] The invention relates to efficient, network-independent intermediate circuit conditioning with simultaneous reduction of the harmonic content in the input current, ie to achieving usability or suitability in different power supply networks, in particular three-phase and multi-phase networks. Background Art

[0002] Different solutions are known in the prior art for implementing intermediate circuit conditioning for different types of power supply networks.

[0003] For example, EP 0 696 838 B1 discloses a multiphase rectifier bridge for a single-phase input. EP 3 324 535 B1 relates to an electronically commutated fan system.

[0004] A motor drive power conversion system is known from EP 3509212A1, comprising a filter circuit with a single inductor and a capacitor for each input phase, an active rectifier with a silicon carbide rectifier switching device, a DC intermediate circuit with a thin-film DC intermediate circuit capacitor and an inverter, and a controller for operating the rectifier switching device at a PWM rectifier switching frequency of 10 kHz or higher.

[0005] Furthermore, US 2007 004 0516 A1 discloses an AC-DC converter with PFC, which provides a constant output voltage at an arbitrary predetermined value (whether lower or higher than or even equal to the input line peak voltage) with an input line AC voltage over a wide voltage range (typically sinusoidal 110 VAC, 60 Hz or 220 VAC, 50 Hz).

[0006] However, the known systems in the prior art show at least one of the following disadvantages or problems that need to be improved or eliminated:

[0007] a) The harmonic content of the input current is too high;

[0008] b) It is not possible to adjust the intermediate circuit voltage independently of the grid type;

[0009] c) It is not possible to provide the intermediate circuit voltage level according to the load;

[0010] d) Load asymmetry of grid phases;

[0011] e) Inability to reduce electronic component variations (Elektronikvarianz);

[0012] f) The tooling costs for design and manufacture and / or the R&D costs are high;

[0013] g) The large number of variants leads to high storage costs. Summary of the invention

[0014] The object of the present invention is therefore to overcome the above-mentioned disadvantages and to provide a cost-effective solution by means of which an efficient, network-type-independent intermediate circuit conditioning can be achieved while in particular reducing the harmonic content in the input current.

[0015] This object is achieved by the combination of features described below.

[0016] The basic concept of the present invention is a variable grid connection scheme with a three-phase PFC topology structure, and adopts a design that can realize control and adjustment, so that the three-phase current PFC topology structure can also be used for a single-phase grid connection at the same output power.

[0017] To this end, the present invention proposes a circuit configuration for a variable grid connection (single-phase / three-phase) with respect to the input voltage, which has a three-phase PFC stage (PFC-stage), the center tap between the capacitors of which is connected to the neutral line of the input AC voltage source via a connecting line. This circuit topology has the characteristics of single-phase grid operation, that is, the rectified voltage is doubled in order to subsequently adjust it to the voltage level to be controlled.

[0018] In which, three-phase operation on the phases (L1, L2, L3) of the input AC voltage source is carried out in a first circuit topology, and single-phase operation is achieved by connecting the phase connectors (L1, L2, L3) to each other in parallel and preferably by further modifying the circuit (for relevant description, refer to the preferred implementation variant below).

[0019] The circuit arrangement thus has in principle switching or regulating components for normally establishing a topology for three-phase operation and alternatively for single-phase operation.

[0020] The circuit configuration consists of two diodes and two capacitors connected in series. In this case, the voltage source is applied between the two diodes and the center tap of the capacitor. With such a connection, the positive half-wave of the grid charges the upper capacitor and the negative half-wave charges the lower capacitor. In this way, twice the rectified supply voltage is applied via the two capacitors.

[0021] In a preferred technical solution, it is arranged as follows: a switch is provided in the connecting line between the voltage multiplier circuit and the neutral line connection so as to selectively open or close the connection to switch the single-phase operation to the three-phase operation.

[0022] Further, it is advantageously arranged as follows: a voltage evaluation device is provided between the input AC voltage source and the PFC stage, and the switch state (open / closed) of the switch is controlled by the voltage evaluation device.

[0023] In another preferred technical solution of the present invention, it is arranged as follows: during three-phase operation, the three phase connectors (L1, L2, L3) are respectively connected to an input end of the PFC section, while during single-phase operation, the three phase connectors (L1, L2, L3) are connected to each other and connected to the neutral line connector via the connecting line through the center tap of the capacitor so as to be connected to the neutral line of the AC input voltage source.

[0024] The connection mentioned in the previous paragraph can be established manually with the aid of cables, jumpers or connecting wires installed for this purpose, or automatically by evaluating the input voltage, for which purpose, when automatic connection establishment is selected, the input voltage is evaluated and, if a single-phase supply is detected, the center tap of the capacitor is connected to the neutral conductor via an electrical switch / relay. If, on the other hand, a three-phase supply is detected, the switch remains open.

[0025] It is further advantageous that an EMC filter with adjustable filter characteristics is provided upstream of the PFC stage, the filter characteristics of the EMC filter being adjusted, depending on single-phase operation or three-phase operation, preferably by means of several current-compensated inductors.

[0026] In a preferred technical solution of the present invention, the three-phase PFC stage is formed as a Vienna rectifier. However, other PFC stages may also be implemented (as shown in the following description of the embodiment).

[0027] Six diodes and one electrical switch in each case may be provided in each line branch of the PFC stage, as well as series capacitors connected in parallel therewith, the center tap being formed between the capacitors and being connected or connectable to the neutral line of the input AC voltage source.

[0028] In a preferred technical solution of the present invention, it is provided as follows: in order to realize the single-phase operation, a branch connected in parallel with the rectifier diode and each having two other series diodes is provided in each line branch of the PFC stage, and the branch is connected to the neutral line between the diodes, while the aforementioned center taps between the capacitors are not connected to the neutral line via the connecting line, but are connected to the center taps respectively. This measure prevents voltage doubling in a targeted manner, so that commutation can also be achieved for electrical devices with smaller voltage control.

[0029] The features of other advantageous improved solutions of the present invention can be found above, and they are described in detail below with reference to the accompanying drawings and in combination with the preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] in:

[0031] Figure 1 A circuit topology of a Vienna rectifier as a PFC stage to implement a first embodiment of a circuit according to the present invention;

[0032] Figure 2 It is a schematic diagram for explaining the basic principle of the present invention.

[0033] Figure 3 is an alternative embodiment of the circuit according to the present invention;

[0034] Figure 4 is another alternative embodiment of the circuit according to the present invention;

[0035] Figure 5 is yet another alternative embodiment of the circuit according to the present invention;

[0036] Figure 6 is yet another alternative embodiment of the circuit according to the present invention;

[0037] Figure 7 FIG. 2 is another alternative embodiment of the circuit according to the present invention without voltage doubling. DETAILED DESCRIPTION

[0038] The present invention will be explained in detail below with reference to the accompanying drawings, wherein the same reference numerals refer to the same structural features and / or functional features in different embodiments.

[0039] Figure 1 First, an exemplary circuit topology of a Vienna rectifier as a PFC section to realize a first embodiment of the circuit 1 according to the present invention is shown. Therein, the Vienna rectifier consists of three branches 20, 30, 40, that is, one line branch for each phase L1, L2, L3. Each line branch 20, 30, 40 is realized by six diodes D and one electrical switch Sz (for example, MOSFET, IGBT, ...). The center tap M is connected by capacitors C1 and C2 connected in series. By appropriate synchronization of the electrical switches Sz, the capacitors C1 and C2 are symmetrically charged by means of the center tap M so that a synchronous sinusoidal current can be obtained from the power grid.

[0040] Figure 2A schematic diagram for explaining the basic principle of the invention is shown. The left part of the figure shows the phase connections L1, L2, L3 and the neutral connection N. This is followed by a three-phase PFC section (here in the form of a Vienna rectifier), whose output terminals V1, V2, V3 are connected to two capacitors C1, C2, wherein a center tap M is connected to the output terminal V2 of the PFC section, and this center tap M between the capacitors C1, C2 is connected to the neutral connection N of the input AC voltage source via a connecting line 10. Furthermore, the connections of an exemplary load are shown.

[0041] A switch S is provided in the connecting line 10 . Furthermore, a voltage evaluation device 2 is provided between the input AC voltage source or the connections L1 , L2 , L3 and N and the PFC stage. The switching state (open / closed) of the switch S is controlled by the voltage evaluation device 2 .

[0042] An EMC filter (EMC) with adjustable filter characteristics is provided in front of the PFC stage, the filter characteristics of which are preferably implemented by current-compensated chokes. For this purpose, one or more four-phase current-compensated chokes are used, depending on the filter level. In three-phase operation, these current-compensated chokes act like a three-phase Stroko, since the neutral conductor is not connected. In single-phase operation, the three coils are energized in parallel. The total current then returns via the fourth coil in the neutral conductor.

[0043] Figure 3 An embodiment of the circuit according to the invention is shown. The PFC stage shown in the figure is in principle constructed by six diodes D and three electronic switches Sz. In this topology, the switch Sz is directly connected to the center tap M.

[0044] The basic functions of the switch Sz can be realized by different implementations as described below. As an example, Figures 4 to 6 The following topology.

[0045] Figure 7 The embodiment of the embodiment of the present invention illustrates the preferred implementation of single-phase operation. For this purpose, the three phase connectors L1, L2, L3 are connected to three capacitors Ca, Cb, Cc. The center tap is marked with M1. The connecting line 10 is connected to the neutral line N of the AC input voltage source. If you do not want to double the voltage during single-phase operation, you must also use Figure 7 The circuit is adjusted by the additional diodes shown. Two diodes are required for each branch. These diodes are connected in parallel with the existing rectifier diodes. The neutral line N is not adapted to the center tap of the capacitor between capacitors C1 and C2, but to the corresponding common connection Mz.

[0046] The implementation scope of the present invention is not limited to the above-mentioned preferred embodiments. Any technical variation using the illustrated solution, even if implemented in a completely different way, also falls within the scope of the present invention.

Claims

1. A circuit arrangement (1) for a single-phase or three-phase grid connection with a variable input voltage, the circuit arrangement having a three-phase PFC stage and a center tap (M) between capacitors (C), the center tap being connected to a neutral conductor (N) of an input AC voltage source via a connecting line (10), in, In order to realize single-phase operation, a branch having two further series-connected diodes is connected in parallel with a rectifier diode in each line branch (20, 30, 40) of the PFC section, and a central center tap is connected to the neutral line (N), while the center tap (M) between the capacitors (C) is not connected to the neutral line (N) via the connecting line (10).

2. The circuit arrangement (1) according to claim 1, characterized in that A switch (S) is provided in the connecting line (10).

3. The circuit arrangement (1) according to claim 2, characterized in that A voltage evaluation device (2) is provided between the input AC voltage source and the PFC section, and the switching state of the switch (S), i.e., the open or closed state, is controlled by the voltage evaluation device (2).

4. The circuit arrangement (1) according to any one of claims 1 to 3, characterized in that During three-phase operation, three phase connectors (L1, L2, L3) are respectively connected to the PFC section, while during single-phase operation, the three phase connectors (L1, L2, L3) are connected to each other via three capacitors (Ca, Cb, Cc) to form a parallel circuit, and are connected to the neutral line (N) of the input AC voltage source via the connecting line (10) via a center tap (M1) of the parallel circuit.

5. The circuit arrangement (1) according to claim 4, characterized in that The connection is established manually by means of cables, jumpers or connecting wires installed for this purpose or automatically by evaluating the input voltage.

6. The circuit arrangement (1) according to any one of claims 1 to 3, characterized in that An EMC filter (EMC) with adjustable filtering characteristics is arranged before the PFC stage.

7. The circuit arrangement (1) according to any one of claims 1 to 3, characterized in that The three-phase PFC stage is a Vienna rectifier with diodes arranged in parallel.

8. The circuit arrangement (1) according to any one of claims 1 to 3, characterized in that Six diodes (D) and one electrical switch (S) are provided in each line branch (20, 30, 40), as well as series capacitors (C1, C2) connected in parallel therewith, between which a center tap (M) is formed which is connected to the neutral line (N) of the input AC voltage source.

9. The circuit arrangement (1) according to claim 6, characterized in that The filtering characteristics of the EMC filter are realized by means of several current-compensated chokes.

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