Multi-voltage level output device and power system

Abstract

The application discloses a multi-voltage grade output device and a power system, and belongs to the technical field of power electronics. The multi-voltage grade output device comprises an output line, a multi-winding transformer having a plurality of secondary winding groups, a plurality of power conversion units, an input side of the power conversion unit being connected with the secondary winding group in correspondence, and a switching unit connected between the output side of each power conversion unit and the output line and configured to switch the output side of the power conversion unit between at least two of partial cascade connection, full cascade connection or full parallel connection after cascade connection. By parallel connection, parallel connection after cascade connection or full cascade connection of the power conversion unit, different voltage grades can be provided, compatibility is improved, and the total output power is almost the same under various connection forms.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a multi-voltage level output device and power system. Background Technology

[0002] Adaptability testing of power generation equipment typically requires products such as grid simulators and high-voltage frequency converters. These products usually cascade power units to output the required test voltage, such as 10kV. However, since different power generation equipment requires different voltage levels for testing, additional transformers are needed when applying to other voltage levels, which increases size and cost. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a multi-voltage level output device and power system that is compatible with different voltage levels and maintains almost the same total output power under various connection methods.

[0004] In a first aspect, this application provides a multi-voltage level output device, comprising:

[0005] Output lines;

[0006] A multi-winding transformer has multiple secondary windings;

[0007] Multiple power conversion units, with the input side of each power conversion unit connected to the secondary winding.

[0008] A switching unit is connected between the output side and the output line of each power conversion unit, and is configured to switch the output side of the power conversion unit between at least two cases: partially cascaded and then connected in parallel, fully cascaded, or fully connected in parallel.

[0009] According to one embodiment of this application, the switching unit includes:

[0010] Multiple first lines are provided, each first line is configured to correspond to each power conversion unit, and the second end of each first line is connected to the output line.

[0011] A switching circuit is connected to the output side of each power conversion unit and the first end of each first line, and is configured to connect the output side of the power conversion unit to the first end of the corresponding first line, or to cascade the output side of the power conversion unit with the output side of another power conversion unit.

[0012] According to one embodiment of this application, the output side of the power conversion unit is provided with an extension node, which is arranged correspondingly to the output side of another power conversion unit, and the switching circuit includes:

[0013] Multiple first switches are provided, each first switch being disposed between the output side of the power conversion unit and the corresponding first line. The first switches are configured to connect the output side of the power conversion unit and the first line, connect the output side of the power conversion unit and the extension node, or connect each output node of the output side of the power conversion unit.

[0014] According to one embodiment of this application, the switching unit further includes a plurality of bridge arm inductors, each bridge arm inductor being connected between the second end of each first line and the output line.

[0015] According to one embodiment of this application, the switching unit further includes:

[0016] Multiple second lines are arranged between two adjacent bridge arm inductors;

[0017] Multiple second switches are connected to the first end of the bridge arm inductor. The second switches are configured to switchably connect the first end of the bridge arm inductor to the second end of the first line, or connect the first end of the bridge arm inductor to the first end of the second line.

[0018] Multiple third switches are connected to the second end of the bridge arm inductor. The third switches are configured to switchably connect the second end of the bridge arm inductor to the output line, or connect the second end of the bridge arm inductor to the second end of the second line.

[0019] According to one embodiment of this application, the multi-voltage level output device further includes:

[0020] The controller is connected to each power conversion unit, the first switch, the second switch, and the third switch, respectively.

[0021] According to one embodiment of this application, the multi-voltage level output device further includes:

[0022] Multiple fourth switches, with the first terminal of each fourth switch connected to the output line;

[0023] Multiple capacitor banks are connected, with the first terminal of each capacitor bank connected to the second terminal of the fourth switch, and the second terminal of each capacitor bank connected to the neutral point.

[0024] According to one embodiment of this application, the plurality of capacitor banks include a first capacitor bank and a second capacitor bank. The withstand voltage rating of the first capacitor bank is lower than that of the second capacitor bank. The fourth switch connected to the first capacitor bank is a high-voltage circuit breaker or an electric disconnect switch.

[0025] According to one embodiment of this application, the power conversion unit includes a three-phase full-bridge circuit, a bus capacitor, and an H-bridge circuit connected in sequence. The input side of the three-phase full-bridge circuit serves as the input side of the power conversion unit, and the output side of the H-bridge circuit serves as the output side of the power conversion unit.

[0026] According to one embodiment of this application, multiple power conversion units are configured as single-phase or three-phase output units, and the switching unit is configured to cascade the output side portions of the single-phase or three-phase output units and then connect them in parallel, cascade all of them, or connect all of them in parallel.

[0027] Secondly, this application provides a power system including the multi-voltage level output device according to the foregoing.

[0028] According to the multi-voltage level output device and power system of this application, by connecting the power conversion units in parallel, cascaded and then parallel, or all of them in cascade, different voltage levels can be provided, improving compatibility, and the total output power is almost the same under various connection methods.

[0029] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0030] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0031] Figure 1 This is a circuit structure block diagram of the multi-voltage level output device provided in the embodiments of this application;

[0032] Figure 2 This is a circuit topology diagram of the power conversion unit provided in the embodiments of this application;

[0033] Figure 3 This is one of the circuit topologies of the multi-voltage level output device provided in the embodiments of this application;

[0034] Figure 4 This is the second circuit topology of the multi-voltage level output device provided in the embodiments of this application;

[0035] Figure 5 This is the third circuit topology of the multi-voltage level output device provided in the embodiments of this application;

[0036] Figure 6 This is the fourth circuit topology of the multi-voltage level output device provided in the embodiments of this application;

[0037] Figure 7 This is the fifth circuit topology of the multi-voltage level output device provided in the embodiments of this application;

[0038] Figure 8 This is the sixth circuit topology of the multi-voltage level output device provided in the embodiments of this application.

[0039] Figure label:

[0040] Multi-winding transformer 100, power conversion unit 200, three-phase full-bridge circuit 210, H-bridge circuit 220, switching unit 300, output line 400, capacitor bank 500, first to fourth switches K1 to K4. Detailed Implementation

[0041] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0042] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0043] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0044] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] In related technologies, based on cascaded power conversion units, two stages of transformers are added at both the input and output. By switching on these transformers, the equipment can achieve different voltage levels of input and output capability. This leads to an increase in size and cost. Alternatively, a bypass unit can be added to the cascaded power conversion units to achieve different voltage levels by reducing the number of cascaded units. However, this method is limited by the rated current of a single unit and cannot provide constant power output.

[0046] This application proposes a multi-voltage level output device and power system. By connecting power conversion units in parallel, cascaded and then parallel, or all of them in cascade, different voltage levels can be provided, improving compatibility. Under various connection methods, the total output power is almost the same.

[0047] Reference Figure 1 , Figure 1 A circuit structure for a multi-voltage level output device is shown. One embodiment of this application proposes a multi-voltage level output device. In this embodiment, the multi-voltage level output device includes a multi-winding transformer 100, multiple power conversion units 200, a switching unit 300, and an output line 400. The multi-winding transformer 100 has multiple secondary windings, and the input side of the power conversion unit 200 is connected to the corresponding secondary winding. The switching unit 300 is connected between the output side of each power conversion unit 200 and the output line, and is configured to switch the output side of the power conversion unit 200 between at least two cases: partially cascaded and then paralleled, fully cascaded, or fully paralleled.

[0048] The primary winding of the multi-winding transformer 100 is connected to a power source, which can be a power grid or other power generation equipment. Each secondary winding is magnetically coupled to the primary winding and generates an induced current in response to the current in the primary winding. The turns ratio of each secondary winding can be the same as that of the primary winding, meaning that each secondary winding generates the same induced current. Of course, the turns ratio of each secondary winding can also be different from that of the primary winding, depending on the specific requirements; this embodiment does not impose any limitations on this.

[0049] Each power conversion unit 200 is connected to each secondary winding in a one-to-one correspondence. The output of each secondary winding is converted by the power conversion unit 200 before being output. The power conversion unit 200 can boost or buck the output voltage of the secondary winding, and adjust the output frequency, etc.

[0050] An input inductor L1 can be provided between each secondary winding and the corresponding power conversion unit 200. The first end of the input inductor L1 is connected to the secondary winding, and the second end of the input inductor L1 is connected to the input side of the power conversion unit 200. The input inductor L1 can play a role in filtering and smoothing current and reducing electromagnetic interference.

[0051] Reference Figure 2 , Figure 2A circuit topology for a power conversion unit 200 is shown. In some embodiments, the power conversion unit 200 may include a three-phase full-bridge circuit 210, a bus capacitor C0, and an H-bridge circuit 220 connected in sequence. The input side of the three-phase full-bridge circuit 210 serves as the input side of the power conversion unit 200, and the output side of the H-bridge circuit 210 serves as the output side of the power conversion unit 200.

[0052] The input side of the three-phase full-bridge circuit 210 is connected to the secondary winding to receive the three-phase AC output of the secondary winding, which can serve as a rectifier. The three-phase full-bridge circuit 210 can use PWM (Pulse Width Modulation) control to achieve sinusoidal current input, reducing grid harmonic interference. The output side of the H-bridge circuit 220 is connected to the switching unit 300, which can serve as an inverter. The H-bridge circuit 220 can generate a near-sinusoidal stepped voltage through multi-level modulation, with extremely low harmonic content. The power conversion unit 200 can also adopt other types of circuit topologies; this embodiment does not impose any limitations on this.

[0053] The output side of the H-bridge circuit 220 can be cascaded to directly output high voltage, eliminating the need for an output step-up transformer. For example, if the output voltage of a single H-bridge circuit 220 is 1KV, then the output sides of 10 H-bridge circuits 220 can be cascaded to output a voltage of 10KV.

[0054] The switching unit 300 may include a switching circuit equipped with a switching device. The switching circuit is connected to the output side of each power conversion unit 200, and the on / off state of the switching circuit can adjust the connection between the output sides of each power conversion unit 200. The switching device may be a relay or a disconnecting switch, etc.

[0055] Taking the output side of the power conversion unit 200 as the output side of the H-bridge circuit 220 as an example, the output side of the H-bridge circuit 220 includes a first output node A1 and a second output node A2. A switching line can connect the first output nodes A1 of both H-bridge circuits 220 and the second output nodes A2 of both H-bridge circuits 220, thus connecting the two H-bridge circuits 220 in parallel. Alternatively, the switching line can cascade the first output node A1 of one H-bridge circuit 220 and the second output node A2 of another H-bridge circuit 220.

[0056] It should be noted that partial cascading followed by parallel connection refers to the power conversion units 200 being cascaded in groups, with each group of power conversion units 200 connected in parallel. For example, assuming there are 10 power conversion units 200, and the output voltage of each power conversion unit 200 is 1kV, the switching unit 300 can cascade the output sides of two power conversion units 200, and then connect the cascaded outputs in parallel. In this case, the total output voltage is 2kV. Alternatively, the switching unit 300 can cascade the output sides of five power conversion units 200, and then connect the cascaded outputs in parallel. In this case, the total output voltage is 5kV. The number of units cascaded in partial cascading followed by parallel connection can be selected according to requirements.

[0057] As an example, the number of power conversion units 200 is n, and the number of cascaded power conversion units 200 can be greater than or equal to 2, 3, ..., n / 2. In some cases, at least one stage may be unable to be connected. For example, if the number of power conversion units 200 is 9 and the number of cascaded power conversion units 200 is 4, one stage may be unable to be connected. Or, if the number of power conversion units 200 is 10 and the number of cascaded power conversion units 200 is 4, two stages may be unable to be connected.

[0058] It should be noted that the output side of each power conversion unit can be configured as three-phase output or single-phase output after partial cascading and parallel connection, full cascading, or full parallel connection.

[0059] The output of each power conversion unit 200 can be used as a single-phase output. In three-phase output mode, the three power conversion units 200 function as a single three-phase output unit, and the switching unit 300 controls the cascading or parallel connection of the three-phase output units. In single-phase output mode, each power conversion unit 200 functions as a single-phase output unit, and the switching unit 300 controls the cascading or parallel connection of the single-phase output units.

[0060] As an example, if the switching unit 300 controls two cascaded three-phase output units, then the output side of the H-bridge circuit 220 that outputs the U phase in one three-phase output unit is cascaded with the output side of the H-bridge circuit 220 that outputs the U phase in another three-phase output unit; the output side of the H-bridge circuit 220 that outputs the V phase in one three-phase output unit is cascaded with the output side of the H-bridge circuit 220 that outputs the V phase in another three-phase output unit; and the output side of the H-bridge circuit 220 that outputs the W phase in one three-phase output unit is cascaded with the output side of the H-bridge circuit 220 that outputs the W phase in another three-phase output unit. When the switching unit 300 controls two three-phase output units to be connected in parallel, the output sides of the H-bridge circuits 220 that output the same phase in both three-phase output units are connected in parallel.

[0061] The cascading or parallel control of a single-phase output unit is the same as the cascading or parallel control of a single power conversion unit 200, as detailed in the aforementioned embodiments.

[0062] In this embodiment, the multi-voltage level output device also includes a controller (not shown in the figure), which is connected to the power conversion unit 200 and the switching unit 300 to control the power conversion unit 200 to adjust the output voltage and frequency, and to control the connection mode of the switching unit 300 to the output of the power conversion unit 200.

[0063] The controller can be implemented using an MCU (Microcontroller Unit) chip; it can also be implemented based on a DSP (Digital Signal Processor) chip, an FPGA (Field-Programmable Gate Array), or a custom controller chip; the embodiments of this application do not limit the specific hardware implementation of the controller.

[0064] Output line 400 is used to collect the outputs of each power conversion unit 200, and may include busbars, such as copper busbars or aluminum busbars. Output line 400 may include three busbars to serve as U-phase output, V-phase output, and W-phase output respectively, realizing three-phase output. Output line 400 may also include one busbar to realize single-phase output. The specific number of busbars can be set according to requirements, and this embodiment does not limit this.

[0065] The multi-voltage output device can also be equipped with multiple neutral (N) lines. One side of each N line converges and connects to the U, V, and W phase busbars, while the other side of each N line is used to connect to the lower bridge transistor in each power conversion unit 200. By using multiple N lines, it is easier to set up neutral nodes when the connection between the power conversion units 200 changes.

[0066] According to the multi-voltage level output device of this application, different voltage levels can be provided by connecting power conversion units in parallel, cascading and then paralleling, or cascading all of them, thereby improving compatibility, and the total output power is almost the same under various connection methods.

[0067] Reference Figure 3 , Figure 3 A circuit topology for a multi-voltage level output device is illustrated. As an example, the primary winding of a multi-winding transformer 100 is connected to the power grid, and each secondary winding is connected to a power conversion unit 200 via an input inductor L1. The output line 400 includes buses for providing three-phase output, including a U-phase bus, a V-phase bus, and a W-phase bus.

[0068] In this example, the multi-voltage output device includes a bridge arm inductor L2, which can be connected to the output stage of each power conversion unit 200 to filter and smooth the output. The number of bridge arm inductors L2 can be the same as the number of power conversion units 200, with one bridge arm inductor L2 corresponding to each power conversion unit 200.

[0069] In some embodiments, the bridge arm inductor L2 can be disposed within the switching unit 300, and its connection method changes depending on the connection method between the power conversion units 200. For example, when two power conversion units 200 are cascaded, the output circuit has two power conversion units 200, and correspondingly two bridge arm inductors L2 connected in series. When the power conversion units 200 are connected in parallel, the output circuit has one power conversion unit 200, and correspondingly one bridge arm inductor L2 connected in series.

[0070] Output line 400 is also connected to capacitor bank 500. In a three-phase output architecture, capacitor bank 500 includes at least one capacitor connected between the U-phase bus and the grounding node, one capacitor connected between the V-phase bus and the grounding node, and one capacitor connected between the W-phase bus and the grounding node. The capacitors and busbars can be directly connected via cables or switches.

[0071] Reference Figure 4 , Figure 4 A circuit topology for a multi-voltage level output device is illustrated. As an example, the switching unit 300 includes a plurality of first lines M1 and a switching circuit. Each first line M1 is correspondingly configured with a power conversion unit 200. The second terminal of each first line M1 is connected to the output line 400. The switching circuit is connected to the output side of each power conversion unit 200 and the first terminal of each first line M1, and is configured to connect the output side of the power conversion unit 200 to the first terminal of the corresponding first line M1, or to cascade the output side of the power conversion unit 200 with the output side of another power conversion unit 200.

[0072] The switching circuit may include multiple switches, each connected between the output side of each power conversion unit 200 and the first terminal of each first line M1. The connection between the output side of each power conversion unit 200 and the first terminal of each first line M1 can be adjusted by changing the on / off state of each switch. The second terminal of the first line M1 can be indirectly connected to the output line 400 via the bridge arm inductor L2.

[0073] The number of first lines M1 can be the same as that of power conversion units 200, and they are used to provide an output line for each power conversion unit 200. When the first line M1 and the output side of the power conversion unit 200 are connected, the output current of the power conversion unit 200 flows to the output line through the first line M1 to be connected in parallel with the output of other lines.

[0074] In the case where the output side of power conversion unit 200 is cascaded with the output side of another power conversion unit 200, the first output node A1 of power conversion unit 200 can be connected to the second output node A2 of another power conversion unit 200, thereby cascading the two power conversion units 200. The last stage power conversion unit 200 is connected to its corresponding first line M1 for output.

[0075] As an example, the output side of the power conversion unit 200 is provided with an extension node A3, which is arranged correspondingly to the output side of another power conversion unit 200. The switching circuit includes a plurality of first switches K1, each of which is disposed between the output side of the power conversion unit 200 and the corresponding first line M1. The first switches K1 are configured to connect the output side of the power conversion unit 200 and the first line M1, connect the output side of the power conversion unit 200 and the extension node A3, or connect each output node of the output side of the power conversion unit.

[0076] Extension node A3 is formed by extending one of the output nodes of power conversion unit 200 through a line. For example, the output side of power conversion unit 200 is provided with a copper busbar or aluminum busbar, the first end of the copper busbar or aluminum busbar is connected to the second output node A2 of power conversion unit 200, and the second end of the copper busbar or aluminum busbar is extension node A3.

[0077] For example, in some embodiments, the first switch K1 can be a three-position switch. The first end of the first switch K1 can be connected to the first output node A1, and the second end of the first switch K1 can be connected to the extension node A3 of the upper-level power unit 200 to form a cascade structure, or connected to the first line M1 on the right to form a parallel structure, or connected to its own second output node A2 to short-circuit its own output, bypassing its own compatibility and fault-tolerant control.

[0078] In this example, the number of bridge arm inductors L2 can be the same as the number of first lines M. The bridge arm inductors L2 can be connected between the second end of each first line M and the output line 400 to filter and smooth the output of each output line.

[0079] In some embodiments, the switching unit 300 further includes a plurality of second lines M2, a plurality of second switches K2, and a plurality of third switches K3. The second lines M2 are arranged between two adjacent bridge arm inductors L2. The second switches K2 are connected to the first end of the bridge arm inductor L2 and are configured to switchably connect the first end of the bridge arm inductor L2 to the second end of the first line M1, or connect the first end of the bridge arm inductor L2 to the first end of the second line M2. The third switches K3 are connected to the second end of the bridge arm inductor L2 and are configured to switchably connect the second end of the bridge arm inductor L2 to the output line 400, or connect the second end of the bridge arm inductor L2 to the second end of the second line M2.

[0080] The second switch K2 and the third switch K3 can be relays or disconnect switches. The two ends of the second line M2 are connected to different bridge arm inductors L2 via the second switch K2 and the third switch K3, achieving series connection between two bridge arm inductors L2. The number of bridge arm inductors L2 connected in series can be the same as the number of power conversion units 200 cascaded. For example, when two power conversion units 200 are cascaded, their corresponding two bridge arm inductors L2 are connected in series.

[0081] The controller can be connected to the first switch K1, the second switch K2 and the third switch K3 in the switching unit 300. By controlling the on and off of the first switch K1, the second switch K2 and the third switch K3, the connection mode of the output side of the power conversion unit 200 can be adjusted.

[0082] In some embodiments, the multi-voltage level output device may further include a plurality of fourth switches K4 and a plurality of capacitor banks 500, wherein the first terminal of the fourth switch K4 is connected to the output line; the first terminal of the capacitor bank 500 is connected to the second terminal of the fourth switch K4, and the second terminal of the capacitor bank 500 is connected to a grounding node. The switching on and off of the fourth switch K4 may also be controlled by the aforementioned controller.

[0083] Understandably, when the bridge arm inductors L2 are connected in parallel, the inductance value decreases, and the cutoff frequency formed by the inductor and capacitor increases. When changing from a traditional cascaded structure to a parallel structure, capacitors need to be added to maintain a consistent cutoff frequency. Therefore, to adapt to different cascaded or parallel architectures, each capacitor group 500 is connected to the output line 400 through the fourth switch K4, allowing each capacitor group 500 to be switched on or off.

[0084] For example, when all power conversion units 200 are cascaded, the fourth switch K4 corresponding to each capacitor bank 500 is in the ON state. When the power conversion units 200 are generally cascaded, the fourth switch K4 corresponding to half of the capacitor banks 500 is in the ON state. When all power conversion units 200 are connected in parallel, the fourth switch K4 corresponding to one group of capacitor banks 500 is in the ON state.

[0085] In other examples, since at least one set of capacitor banks 500 is connected, one set of capacitor banks 500 can be directly connected to the output line 400 via a cable, and the remaining capacitors 500 are connected to the output line 400 via the fourth switch K4.

[0086] In some embodiments, the plurality of capacitor banks include a first capacitor bank and a second capacitor bank, wherein the withstand voltage rating of the first capacitor bank is lower than that of the second capacitor bank, and the fourth switch connected to the first capacitor bank is a high-voltage circuit breaker or an electric disconnect switch.

[0087] Understandably, by setting capacitor banks with different voltage ratings, the appropriate capacitor bank can be switched in according to requirements. Using low-voltage capacitors can reduce costs. If low-voltage capacitors are added, high-voltage circuit breakers or electrically operated disconnect switches can be added. The program can then limit the switch connection based on the output voltage level. The number of high-voltage circuit breakers and disconnect switches is determined by the required output voltage level. Capacitors with the highest voltage level do not require high-voltage circuit breakers or disconnect switches.

[0088] based on Figure 4 The circuit topology shown is illustrated below, and different connection configurations are explained. Three power conversion units 200 form a single-phase three-phase to single-phase power unit. The capacitor bank 500 includes C1 to Cn, where n is the number of three-phase to single-phase power units. Each capacitor bank 500 includes capacitors connected to the U, V, and W phase output buses, respectively. Since all capacitors in each example are already in operation, the connections between the capacitors and the UVW output lines are represented by cables.

[0089] Reference Figure 5 , Figure 5 A circuit topology for a single-stage parallel connection of multiple voltage level output devices is shown. For example... Figure 5 As shown, the output side of each three-phase-to-single-phase power unit is directly connected to the corresponding first line M1 and bridge arm inductor L2. The three-phase outputs of each stage are connected in parallel and then fed into the three-phase output bus. All C1 to Cn are connected to the three-phase output bus. Each three-phase-to-single-phase power unit is connected to the neutral (N) line.

[0090] Reference Figure 6 , Figure 6 A circuit topology for a multi-voltage output device with two stages connected in parallel is shown. For example... Figure 6 As shown, every two stages of three-phase to single-phase power units are cascaded together, and the bridge arm inductance L2 between the original two stages is connected in series and then in parallel to be fed into the three-phase output busbar. Capacitors C1-Cn / 2 are connected.

[0091] Reference Figure 7 , Figure 7 A circuit topology for n / 2 stages of multi-voltage output devices connected in parallel is shown. For example... Figure 7As shown, the n / 2-stage three-phase to single-phase power units are cascaded together, and the bridge arm inductors L2 of the original n / 2 stages are connected in series and then in parallel to the three-phase output busbar. Capacitors C1-Cn / 2 are connected.

[0092] Reference Figure 8 , Figure 8 A circuit topology in which all multi-voltage level output devices are cascaded is shown. For example... Figure 8 As shown, each stage of the three-phase-to-single-phase power unit is cascaded with the next stage of the three-phase-to-single-phase power unit, forming a cascaded relationship. The inductors L2 of each bridge arm are connected in series and then fed into the three-phase output busbar. Capacitor C1 is connected.

[0093] One embodiment of this application also provides a power system including the multi-voltage level output device as described above. The specific structure and principle of the multi-voltage level output device can be referred to in the foregoing embodiments, which also have corresponding technical effects; therefore, this embodiment will not elaborate further.

[0094] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A multi-voltage level output device, characterized in that, include: Output lines; A multi-winding transformer has multiple secondary windings; Multiple power conversion units, wherein the input side of each power conversion unit is connected to the secondary winding respectively; A switching unit is connected between the output side of each power conversion unit and the output line, and is configured to switch the output side of the power conversion unit between at least two cases: partially cascaded and then connected in parallel, fully cascaded, or fully connected in parallel.

2. The multi-voltage level output apparatus according to claim 1, characterized by, The switching unit includes: Multiple first lines are provided, each first line is configured to correspond to each power conversion unit, and the second end of each first line is connected to the output line. A switching circuit is connected to the output side of each power conversion unit and the first end of each of the first lines, and is configured to connect the output side of the power conversion unit to the first end of the corresponding first line, or cascade the output side of the power conversion unit to the output side of another power conversion unit.

3. The multi-voltage level output apparatus according to claim 2, characterized by The output side of the power conversion unit is provided with an extension node, which is arranged correspondingly to the output side of another power conversion unit. The switching circuit includes: Multiple first switches are provided, each first switch being disposed between the output side of the power conversion unit and the corresponding first line. The first switch is configured to connect the output side of the power conversion unit and the first line, connect the output side of the power conversion unit and the extension node, or connect each output node of the output side of the power conversion unit.

4. The multiple voltage level output apparatus according to claim 3, wherein The switching unit also includes multiple bridge arm inductors, each of which is connected between the second end of each of the first lines and the output lines.

5. The multiple voltage level output apparatus according to claim 4, wherein The switching unit further includes: Multiple second lines are arranged between two adjacent bridge arm inductors; Multiple second switches are connected to the first end of the bridge arm inductor. The second switches are configured to switchably connect the first end of the bridge arm inductor to the second end of the first line, or connect the first end of the bridge arm inductor to the first end of the second line. Multiple third switches are connected to the second end of the bridge arm inductor. The third switches are configured to switchably connect the second end of the bridge arm inductor to the output line, or connect the second end of the bridge arm inductor to the second end of the second line.

6. The multiple voltage level output apparatus according to claim 5, wherein The multi-voltage level output device also includes: The controller is connected to each of the power conversion units, the first switch, the second switch, and the third switch, respectively.

7. The multi-voltage level output device according to any one of claims 1-6, characterized in that, The multi-voltage level output device also includes: Multiple fourth switches, the first end of which is connected to the output line; Multiple capacitor banks, wherein the first end of the capacitor bank is connected to the second end of the fourth switch, and the second end of the capacitor bank is connected to the neutral point.

8. The multi-voltage level output device according to claim 7, characterized in that, The plurality of capacitor banks includes a first capacitor bank and a second capacitor bank. The withstand voltage rating of the first capacitor bank is lower than that of the second capacitor bank. The fourth switch connected to the first capacitor bank is a high-voltage circuit breaker or an electric disconnect switch.

9. The multi-voltage level output device according to any one of claims 1-6, characterized in that, The power conversion unit includes a three-phase full-bridge circuit, a bus capacitor, and an H-bridge circuit connected in sequence. The input side of the three-phase full-bridge circuit serves as the input side of the power conversion unit, and the output side of the H-bridge circuit serves as the output side of the power conversion unit.

10. The multi-voltage level output device according to any one of claims 1-6, characterized in that, The plurality of power conversion units are configured as single-phase or three-phase output units, and the switching unit is configured to cascade the output side portions of the single-phase or three-phase output units and then connect them in parallel, or to cascade all of them or connect them in parallel.

11. An electric power system, characterized in that, The power system includes a multi-voltage level output device according to any one of claims 1-10.

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