Modular multilevel converter and power system using the same

Abstract

The present invention relates to a modular multilevel converter and a power system using the same, the modular multilevel converter having legs corresponding to preset phases, the legs having upper arms and lower arms, the upper arms and the lower arms each having a plurality of sub-modules connected in series, and including a first converter unit that converts DC power input to an input terminal into AC power having the phases and outputs the AC power through a first output terminal; and a second converter unit that converts the DC power input to the input terminal into AC power having a voltage level lower than that of the AC power output from the first converter unit and outputs the AC power through a second output terminal.

Description

[Technical Field]

[0001] The embodiments disclosed in this document relate to a modular multilevel converter and a power system using the same. [Background technology]

[0002] Generally, a modular multilevel converter (MMC) achieves high voltage output through the cascade connection of several converter valve submodule units. The modular multilevel converter does not require direct cascade connection of switching elements, has low requirements for the consistency of element triggers, and has the advantages of excellent scalability, low switching frequency, low operating loss, and high quality output voltage waveform.

[0003] This has created a need for modular multilevel converters in shipboard power systems. Summary of the Invention [Problem to be solved by the invention]

[0004] The embodiments disclosed herein seek to provide a power grid system using modular multilevel converters.

[0005] The embodiments disclosed herein seek to provide an electrical power system for reducing the costs required to operate large electric propulsion vessels.

[0006] The embodiments disclosed herein seek to provide a power grid system that is easy to link with multiple energy sources when operating a large electric propulsion vessel.

[0007] The embodiments disclosed herein seek to provide an electrical power system for efficiently utilizing the limited space on a ship.

[0008] The technical problems of the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] A modular multilevel converter according to an embodiment disclosed herein may include legs corresponding to preset phases, each of the legs having an upper arm and a lower arm, and the upper arm and the lower arm each having a plurality of sub-modules connected in series. The modular multilevel converter may include a first converter unit that converts DC power input to an input terminal into AC power having the phase and outputs the AC power through a first output terminal; and a second converter unit that converts the DC power input to the input terminal into AC power having a voltage level lower than that of the AC power output from the first converter unit and outputs the AC power through a second output terminal.

[0010] In one embodiment, the second converter unit may include at least one of a first low-voltage converter unit configured to convert DC power at the input terminal into AC power having a voltage level lower than that of AC power output from the first converter unit, the second low-voltage converter unit including a plurality of full-bridge additional sub-modules connected in series with the upper arms of the legs of the first converter unit, the plurality of adjacent additional sub-modules being connected in parallel with each other, the second low-voltage converter unit including a plurality of full-bridge additional sub-modules connected in series with the lower arms of the legs of the first converter unit, the plurality of adjacent additional sub-modules being connected in parallel with each other, the second low-voltage converter unit including at least one second low-voltage converter unit configured to convert DC power at the input terminal into AC power having a voltage level lower than that of AC power output from the first converter unit.

[0011] In one embodiment, the power converter may further include a controller that controls power conversion of the first low-voltage converter unit and the second low-voltage converter unit.

[0012] In an embodiment, the first converter unit may be a bidirectional converter that, when AC power is input to the first output terminal, converts the AC power input to the first output terminal into a predetermined DC power and outputs the DC power to the input terminal.

[0013] In an embodiment, the first converter unit and the second converter unit may convert the DC power of the input terminal into three-phase AC power having different voltage levels and output the three-phase AC power.

[0014] According to one embodiment disclosed herein, the power grid system may include a first modular multilevel converter having multiple outputs; a traction motor receiving AC power from a first output of the multiple outputs; a first low-voltage alternating current (ALC) distribution system receiving AC power from a second output of the multiple outputs; and a medium-voltage direct current (MDC) distribution system for supplying DC power to the first modular multilevel converter.

[0015] In one embodiment, a voltage level of the AC power output through the second output terminal may be lower than a voltage level of the AC power output through the first output terminal.

[0016] In one embodiment, the DC power supplied to the first modular multilevel converter via the high voltage DC power distribution may be generated directly or indirectly by at least one of an energy storage system, a fuel cell system, and a generator.

[0017] In one embodiment, the power supply system may further include a second modular multilevel converter electrically connected to the generator and the high voltage DC power distribution and having at least one output.

[0018] In one embodiment, the second modular multilevel converter may have a third output terminal for outputting DC power to the high voltage DC distribution and a fourth output terminal for outputting AC power to a service load distribution.

[0019] In one embodiment, the second modular multilevel converter may have a fifth output terminal for outputting DC power to the high voltage DC distribution and a sixth output terminal for outputting DC power to a service load distribution.

[0020] In an embodiment, the voltage level of the DC power output through the sixth output port may be lower than the voltage level of the DC power output through the fifth output port.

[0021] In one embodiment, the second output terminal and the low voltage AC power distribution may be electrically connected via an isolation transformer.

[0022] In one embodiment, the isolation transformer may be one of a two-winding transformer and a three-winding transformer.

[0023] In one embodiment, the power distribution system may further include a bus tie connected to the high voltage DC power distribution line for exchanging DC power with another power system. [Effects of the Invention]

[0024] The embodiments disclosed herein can provide a power grid system using a modular multilevel converter.

[0025] The embodiments disclosed herein may provide a power grid system to reduce the costs required to operate large electric propulsion vessels.

[0026] The embodiments disclosed herein can provide a power grid system that can easily work with multiple energy sources when operating a large electric propulsion vessel.

[0027] The embodiments disclosed herein may provide an electrical power system for efficiently utilizing the limited space on a vessel.

[0028] In addition, various other effects may be provided that can be grasped directly or indirectly through this document. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram that schematically illustrates a modular multilevel converter according to one embodiment disclosed herein. [Figure 2] FIG. 1 is a schematic circuit diagram of a sub-module of a modular multilevel converter according to one embodiment disclosed herein. [Figure 3] FIG. 1 is a diagram that schematically illustrates a modular multilevel converter according to one embodiment disclosed herein. [Figure 4a] 1 is a schematic configuration diagram of a modular multilevel converter according to an embodiment disclosed in this document and a power system using the same; [Figure 4b] 1 is a schematic configuration diagram of a modular multilevel converter according to an embodiment disclosed in this document and a power system using the same; [Figure 4c] 1 is a schematic configuration diagram of a modular multilevel converter according to an embodiment disclosed in this document and a power system using the same; [Figure 5a] 1 is a schematic diagram of a power system in which a modular multilevel converter having a single output according to an embodiment disclosed herein is disposed between a high-voltage DC power distribution system and a traction motor; [Figure 5b] 1 is a schematic diagram of a power system in which a modular multilevel converter having a single output according to an embodiment disclosed herein is disposed between a high-voltage DC power distribution system and a traction motor; [Figure 6a]1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 6b] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 6c] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 7a] 1 is a schematic diagram of a power system in which a modular multilevel converter having multiple outputs according to an embodiment disclosed herein is arranged between a high-voltage DC power distribution system and a traction motor. [Figure 7b] 1 is a schematic diagram of a power system in which a modular multilevel converter having multiple outputs according to an embodiment disclosed herein is arranged between a high-voltage DC power distribution system and a traction motor. [Figure 8a] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 8b] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 8c] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 9a] 1 is a schematic diagram of a power system in which a modular multilevel converter having multiple outputs according to an embodiment disclosed herein is arranged between a high-voltage DC power distribution system and a traction motor. [Figure 9b]1 is a schematic diagram of a power system in which a modular multilevel converter having multiple outputs according to an embodiment disclosed herein is arranged between a high-voltage DC power distribution system and a traction motor. [Figure 10a] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 10b] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 10c] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC distribution line and a generator. [Figure 11a] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to one embodiment disclosed herein is disposed between a high voltage AC power distribution and a traction motor. [Figure 11b] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to one embodiment disclosed herein is disposed between a high voltage AC power distribution and a traction motor. [Figure 11c] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to one embodiment disclosed herein is disposed between a high voltage AC power distribution and a traction motor. [Figure 11d] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to one embodiment disclosed herein is disposed between a high voltage AC power distribution and a traction motor. [Figure 11e] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to one embodiment disclosed herein is disposed between a high voltage AC power distribution and a traction motor. [Figure 12] 1 is a schematic diagram illustrating a modular multilevel converter and rectification terminal according to one embodiment disclosed herein; [Figure 13a] 1 is a schematic diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is disposed between a high voltage DC distribution line and a generator. [Figure 13b] 1 is a schematic diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is disposed between a high voltage DC distribution line and a generator. [Figure 13c] 1 is a schematic diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is disposed between a high voltage DC distribution line and a generator. [Figure 14a] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14b] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14c] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14d] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14e] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14f] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14g]1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14h] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14i] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 14j] 1 is a schematic block diagram of a power system in which a modular multilevel converter according to an embodiment disclosed herein is additionally disposed between a high voltage DC power distribution and a traction motor. [Figure 15a] 1 illustrates a schematic diagram of a power grid system with grid separation for essential loads and service loads according to one embodiment disclosed herein; [Figure 15b] 1 illustrates a schematic diagram of a power grid system with grid separation for essential loads and service loads according to one embodiment disclosed herein; [Figure 15c] 1 illustrates a schematic diagram of a power grid system with grid separation for essential loads and service loads according to one embodiment disclosed herein; [Figure 15d] 1 illustrates a schematic diagram of a power grid system with grid separation for essential loads and service loads according to one embodiment disclosed herein;

[0030] With regard to the description of the drawings, the same or similar reference numerals may be used for the same or similar components. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. When assigning reference numerals to components in each drawing, it should be noted that identical components are assigned the same numerals whenever possible, even if they are displayed in different drawings. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related known structures or functions is deemed to hinder understanding of the embodiments of the present invention, such detailed description will be omitted.

[0032] In describing components of the embodiments disclosed herein, terms such as "first," "second," "A," "B," "(a)," and "(b)" may be used. These terms are intended merely to distinguish a component from other components and do not limit the nature, order, or sequence of the components. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments disclosed herein pertain. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted as idealized or overly formal unless expressly defined in this application.

[0033] Hereinafter, the embodiments disclosed in this document will be described in detail with reference to the drawings.

[0034] FIG. 1 is a diagram illustrating a modular multilevel converter having a single output.

[0035] Referring to FIG. 1, a modular multilevel converter having a single output terminal includes a plurality of submodules (SM; CELL), and converts input DC power (e.g., medium-voltage direct current (MVDC)) into AC power having phases (e.g., low-voltage alternating current (LVAC)) and outputs it through a single output terminal to drive a load (e.g., a traction motor, etc.).

[0036] FIG. 2 is a schematic circuit diagram of a sub-module of a modular multilevel converter.

[0037] 2, the sub-module (SM) may be configured in a half-bridge or full-bridge configuration, or may be configured in other circuits. The sub-module (SM) can perform a switching operation according to the control of the control unit.

[0038] For reference, the sub-module illustrated in FIG. 2 may be included in the modular multilevel converter having a single output terminal of FIG. 1, but is not limited thereto, and may also be included in the modular multilevel converter having multiple output terminals described later with reference to FIGS. 3, 4a, and 4b, etc.

[0039] 3 is a diagram schematically illustrating a modular multilevel converter 100 having multiple outputs according to an embodiment disclosed herein. That is, it can be seen that the modular multilevel converter illustrated in FIG. 1 has a single output, while the modular multilevel converter illustrated in FIG. 3 has multiple outputs.

[0040] Referring to FIG. 3, the modular multi-level converter 100 may include a first converter unit 110 and second converter units 121 and 122.

[0041] For example, the first converter unit 110 may convert DC power input to the input terminal into AC power having phases and output the AC power to the output terminal. For example, the first converter unit 110 may have a plurality of legs corresponding to preset phases. In this case, each of the plurality of legs may have an upper arm and a lower arm, and each of the upper arm and the lower arm may include a plurality of sub-modules (SM). This will be described in more detail below in the description of FIG. 4a.

[0042] For reference, in FIG. 3, for convenience, a motor is illustrated as an example of a load, but the type of load that receives power from the modular multilevel converter is not limited to a motor, and other types of loads excluding motors can also receive power from the modular multilevel converter.

[0043] Meanwhile, the second converter units 121 and 122 can convert the DC power input to the input terminals, separately from the AC power from each leg of the first converter unit 110, into power (AC power or DC power) having a voltage level lower than the voltage level of the AC power output from the first converter unit 110.

[0044] For example, the second converter unit may include at least one of a first low-voltage converter unit 121 and a second low-voltage converter unit 122. For reference, although both the first low-voltage converter unit 121 and the second low-voltage converter unit 122 are illustrated in FIG. 3 for convenience of understanding, this does not exclude the second converter unit being located at only one of the upper end and the lower end of the first converter unit 110. That is, the first low-voltage converter unit 121 may be located only at the upper end of the first converter unit 110, or the second low-voltage converter unit 122 may be located only at the lower end of the first converter unit 110.

[0045] For example, the first low-voltage converter unit 121 may convert the DC power from the input terminal into power having a voltage level lower than the voltage level of the AC power output from the first converter unit 110 and output the converted power.

[0046] For example, the second low-voltage converter unit 122 may convert the DC power from the input terminal into AC power having a voltage level lower than that of the AC power output from the first converter unit 110 and output the converted AC power.

[0047] That is, the modular multilevel converter 100 according to one embodiment disclosed in this document may have multiple output terminals (a first output terminal corresponding to the first converter unit and a second output terminal corresponding to the second converter unit), through which low voltage power and high voltage power can be supplied simultaneously.

[0048] For reference, the type of power output from the output terminal (i.e., auxiliary output terminal) of the second converter unit may vary depending on the structure of the second converter unit. Among them, a modular multilevel converter having an auxiliary output terminal that outputs AC power will be described below with reference to FIG. 4a.

[0049] FIG. 4a is a diagram that schematically illustrates a modular multilevel converter 100 with multiple outputs according to one embodiment disclosed herein.

[0050] 4a, the modular multi-level converter 100 may include a first converter unit 110 and a second converter unit 120. In this case, the modular multi-level converter 100 may further include a control unit 130.

[0051] As an example, the first converter unit 110 has legs L1, L2, and L3 corresponding to pre-set phases, and each of the legs L1, L2, and L3 has an upper arm UA1, UA2, and UA3 and a lower arm LA1, LA2, and LA3, and the upper arms UA1, UA2, and UA3 and the lower arms LA1, LA2, and LA3 each have a plurality of submodules (SM) connected in series to convert the input DC power into AC power having phases.

[0052] For example, the DC power input to the first converter unit 110 may be medium-voltage direct current (MVDC), and the first converter unit 110 may convert the DC power into AC power to drive a load. In this case, the converted AC power may be three-phase AC power.

[0053] For reference, in FIG. 4a, for convenience, a motor is illustrated as an example of a load, but the type of load supplied with power from the modular multilevel converter is not limited to a motor, and other types of loads excluding motors can also receive power from the modular multilevel converter.

[0054] In this case, the first to third legs L1, L2, and L3 may have upper arms UA1, UA2, and UA3 and lower arms LA1, LA2, and LA3, respectively, and each of the upper arms UA1, UA2, and UA3 and lower arms LA1, LA2, and LA3 of the first to third legs L1, L2, and L3 may include N submodules (SM) (where N is a natural number) connected in series. The voltage of the upper or lower arm of one leg may be the voltage (Vmvdc) of the medium voltage direct current (MVDC) power input to the input terminal, and the voltage between each of the upper and lower terminals of the DC power supply terminal and ground (gnd) may be expressed as 0.5 Vmvdc.

[0055] For example, the first converter unit 110 may convert DC power input to the input terminal into AC power having phases and output the AC power to the output terminal.

[0056] For reference, the sub-modules have been described with reference to FIG. 2, so a duplicated description will be omitted.

[0057] Meanwhile, the second converter unit 120 can convert the DC power input to the input terminal into AC power having a voltage level lower than the voltage level of the AC power output from the first converter unit 110, separately from the AC power from each leg L1, L2, L3 of the first converter unit 110.

[0058] For example, the second converter unit 120 may include a first low-voltage converter unit 121 and a second low-voltage converter unit 122 .

[0059] For example, the first low-voltage converter unit 121 may be configured with a plurality of additional sub-modules configured in a full-bridge configuration, and each additional sub-module may be connected in series with each upper arm UA1, UA2, and UA3 of each leg L1, L2, and L3 of the first converter unit 110. Also, each additional sub-module connected in series with each upper arm UA1, UA2, and UA3 may be connected in parallel with each other. In this case, the first low-voltage converter unit 121 may convert the DC power from the input terminal into AC power having a voltage level lower than that of the AC power output from the first converter unit 110 and output the converted AC power.

[0060] For example, the second low-voltage converter unit 122 may be configured with a plurality of additional sub-modules configured in a full-bridge configuration, and each additional sub-module may be connected in series with each lower arm LA1, LA2, LA3 of each leg L1, L2, L3 of the first converter unit 110. The additional sub-modules connected in series with each lower arm LA1, LA2, LA3 may be connected in parallel with each other. The second low-voltage converter unit 122 may convert the DC power from the input terminal into AC power having a voltage level lower than that of the AC power output from the first converter unit 110 and output the converted AC power.

[0061] As a result, the modular multilevel converter 100 according to an embodiment disclosed herein can simultaneously supply low-voltage AC power and high-voltage AC power. That is, the modular multilevel converter 100 according to an embodiment disclosed herein can have multiple output terminals (first output terminal and second output terminal).

[0062] The modular multi-level converter 100 according to an embodiment disclosed herein may further include a control unit 130, which may control the power conversion operations of the first and second converter units 110 and 120.

[0063] As an example, the control unit 130 may control the switching operation of the first low-voltage converter unit and the second low-voltage converter unit 121, 122 of the second converter unit 120, and the switching circuits of the first low-voltage converter unit and the second low-voltage converter unit 121, 122 may perform switching operations under the control of the control unit 130 to convert the power of the corresponding upper arm or lower arm into AC power having a voltage level lower than the AC power of the first converter unit 110 and output it.

[0064] In this case, the control unit 130 may be configured with at least one processing unit and memory. Here, the processing unit may include, for example, a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc., and may have multiple cores. The memory may be volatile memory (e.g., RAM), non-volatile memory (e.g., ROM, flash memory), or a combination thereof.

[0065] FIG. 4b is a schematic block diagram of a modular multilevel converter according to another embodiment disclosed herein.

[0066] Referring to FIG. 4 b , a modular multi-level converter 200 according to another embodiment disclosed herein may include a first converter unit 210 , a second converter unit 220 , and a control unit 230 .

[0067] As an example, the first converter unit 210 shown in Fig. 4b may have the same configuration as the first converter unit 110 shown in Fig. 4a. For example, the first converter unit 210 may be a bidirectional converter. When the first converter unit 210 is a bidirectional converter, when high-voltage AC power from a generator is input to the output terminal shown in Fig. 4a, the first converter unit 210 may output high-voltage DC power to the input terminal shown in Fig. 4a. Low-voltage DC power may refer to DC power that is less than 1500 V, and high-voltage DC power may refer to DC power that is 1500 V or higher and less than 100 kV.

[0068] That is, the modular multilevel converter 100 in FIG. 4a can receive DC power input, output AC power through the first output terminal, and output AC power through the second output terminal, and the modular multilevel converter 200 in FIG. 4b can receive AC power input, output DC power through the first output terminal (a position corresponding to the input terminal in FIG. 4a), and output AC power through the second output terminal (a position corresponding to the second output terminal in FIG. 4a).

[0069] The rest of the configurations and operations of the first converter unit 210, the second converter unit 220 and the control unit 230 are the same as those described in FIG. 4a, and therefore will not be described here.

[0070] FIG. 4c is a schematic diagram of a power system in which a modular multilevel converter having multiple outputs according to an embodiment disclosed herein is used.

[0071] For example, a power system using a modular multilevel converter having multiple outputs according to an embodiment disclosed herein can supply low-voltage AC power corresponding to a low-voltage load that requires low-voltage AC power through an auxiliary output without using a conventional transformer, as shown in FIG. 4c.

[0072] In this way, low voltage AC power can be supplied to low voltage loads without installing an additional transformer, which reduces costs and reduces the weight and volume of the equipment.

[0073] 5a and 5b are schematic diagrams of a power system in which a modular multilevel converter (MMC) according to an embodiment disclosed herein is used.

[0074] For reference, the modular multilevel converter 10 illustrated in FIGS. 5a and 5b may be a modular multilevel converter having a single output terminal, like the modular multilevel converter illustrated in FIG.

[0075] For reference, a modular multilevel converter 10 having a single output may be used between the high voltage DC distribution 20 and the traction motor 30 shown in Figures 5a and 5b, while a general inverter / converter or a modular multilevel converter may be used between the high voltage DC distribution 20 and the remaining devices (e.g., generator, large motor, etc.).

[0076] 5a and 5b, a power grid system using a modular multilevel converter 10 having a single output according to an embodiment disclosed herein may include a medium-voltage direct current (MVDC) power distribution system 20, the modular multilevel converter 10, and a propulsion motor 30. In this case, the modular multilevel converter 10 may be disposed between the high-voltage DC power distribution system 20 and the propulsion motor 30.

[0077] If a general converter other than the modular multilevel converter 10 is used between the high voltage DC power distribution 20 and the propulsion motor 30, the power capacity that the converter must handle will be too large, and high specification elements will be required to handle this, which will inevitably result in problems with parts supply and demand and costs.

[0078] On the other hand, a modular multilevel converter includes multiple sub-modules, which reduces the capacity that each sub-module must bear even when the modular multilevel converter is connected to a high-capacity power (power distribution).

[0079] Therefore, by using a modular multilevel converter in an electric propulsion vessel such as a large vessel having a propulsion motor that requires a large amount of power, it becomes possible to use elements with universal specifications, thereby ensuring competitiveness in terms of parts supply and demand and price.

[0080] In addition, the modular multilevel converter can be used by adding or removing sub-modules flexibly depending on the situation, which is advantageous in terms of scalability.

[0081] In addition, applying high-voltage DC power distribution to large, electrically propelled ships will facilitate linkage with other energy sources (power supply sources), potentially improving the integrity of the system.

[0082] On the other hand, as shown in Figures 5a and 5b, if the modular multilevel converter 10 disposed between the high-voltage DC distribution 20 and the traction motor 30 has a single output terminal, a separate inverter may be additionally required to supply power to the service load or the corresponding low-voltage AC distribution (LVAC).

[0083] As an example, power can be transferred from a high voltage direct current distribution 20 to a low voltage alternating current distribution (LVAC) via a DC / AC power converter 40 as shown in FIG. 5a.

[0084] As another example, as shown in FIG. 5b, power can be transferred primarily from a high voltage direct current distribution 20 to a low voltage direct current distribution (LVDC) via a DC / DC power converter 40, and secondarily from the low voltage direct current distribution (LVDC) to a low voltage alternating current distribution (LVAC) via a DC / AC power converter.

[0085] Additionally, a power supply source for supplying electric power may be included, and as an example, as shown in Figures 5a and 5b, at least some of an energy storage system (ESS), a fuel cell system (SOFC), a diesel generator (DG), and a shaft generator may be included.

[0086] For example, the capacity of a large motor (e.g., several hundred kW to several MW) may be smaller than the capacity of a propulsion motor (e.g., 10 MW or more). In this case, the large motor may be connected differently depending on the type of ship. If the large motor is connected to an MVDC, the step of boosting the voltage separately when sending power from the aft to the forward can be omitted. Therefore, considering that the size of a large-capacity high-voltage motor is smaller than that of a large-capacity low-voltage motor, a high-voltage motor can be used, thereby reducing the size of the motor.

[0087] As an example, a power conversion device may be used to transmit power supplied from a power supply source to the high voltage DC power distribution system 20. In this case, the power conversion device may be a general inverter or converter as shown in Figures 5a and 5b, but is not limited thereto, and a modular multilevel converter having a single output terminal or multiple output terminals may also be used.

[0088] 6a to 6c illustrate an embodiment in which, in a power system in which the modular multilevel converter 10 having a single output end described in connection with FIGS. 5a and 5b is arranged between the high-voltage DC distribution 20 and the traction motor 30, a modular multilevel converter 50 having a single output end or multiple output ends is additionally arranged between the high-voltage DC distribution 20 and a generator (DG) 60.

[0089] For reference, a modular multilevel converter 10 having a single output end may be used between the high-voltage DC distribution line 20 and the traction motor 30 shown in Figures 6a to 6c, while a general inverter / converter or a modular multilevel converter may be used between the remaining devices (e.g., energy storage system, large motor, etc.) excluding the generator 60 and the high-voltage DC distribution line 20.

[0090] 6a, it can be seen that a modular multilevel converter 50 having a single output end is additionally disposed between a high voltage DC power distribution line 20 and a generator 60. As described above, the modular multilevel converter includes a plurality of sub-modules, which has the effect of reducing the capacity that each sub-module must bear even when the modular multilevel converter is connected to a high-capacity power source (generator).

[0091] 6b, it can be seen that a modular multilevel converter 50 having multiple outputs is additionally disposed between the high-voltage DC distribution system 20 and the generator 60. In this case, it can be seen that the main output (high-voltage DC power output) of the modular multilevel converter 50 having multiple outputs transmits power to the high-voltage DC distribution system 20, and the auxiliary output (low-voltage AC power output) transmits power to the service load (LVAC). As an example, the modular multilevel converter 50 having multiple outputs shown in FIG. 6b may be identical / similar in structure and operation to the modular multilevel converter 200 shown in FIG. 4b.

[0092] In this case, to prevent accidents, the modular multilevel converter 50 having multiple outputs and the service load (LVAC) may be electrically connected via an isolation transformer. In this case, the isolation transformer may be either a two-winding transformer or a three-winding transformer. For reference, two two-winding transformers may be required, and one three-winding transformer may be required.

[0093] 6c, it can be seen that a modular multilevel converter 50 having multiple output terminals is additionally disposed between the high voltage DC distribution line 20 and the generator 60. In this case, it can be seen that the main output terminal (high voltage DC power output) of the modular multilevel converter 50 having multiple output terminals transmits power to the high voltage DC distribution line 20, and the auxiliary output terminal (low voltage DC power output) transmits power to the service load (LVDC).

[0094] Additionally, the power grid system according to an embodiment disclosed herein may additionally include a bus tie for exchanging power with other power grid systems.

[0095] For example, a bus tie may be located between the first power system and the second power system, and the bus tie may include a bus tie breaker for controlling connection and disconnection of the first power system and the second power system. In this case, the breaker may be a solid state circuit breaker (SSCB) as shown in FIG. 5a, but is not limited thereto and may be a mechanical breaker.

[0096] For reference, among the contents described below, those that overlap with the contents described with reference to Figures 1 to 6c, etc. will not be described because they can be easily understood by ordinary engineers.

[0097] 7a and 7b are schematic configuration diagrams of a power system using a modular multilevel converter 10 having multiple outputs according to an embodiment disclosed herein. The modular multilevel converter 10 shown in FIGS. 7a and 7b may be a modular multilevel converter having multiple outputs, such as the modular multilevel converter 100 shown in FIG. 4a. A first output of the multiple outputs may output high-voltage AC power for driving the traction motor 30, and a second output may output low-voltage AC power.

[0098] For reference, a modular multilevel converter 10 having multiple outputs may be used between the high voltage DC distribution 20 and the traction motor 30 shown in Figures 7a and 7b, while a general inverter / converter or a modular multilevel converter may be used between the remaining devices (e.g., energy storage system, large motor, etc.) and the high voltage DC distribution 20.

[0099] 7a and 7b, a power system using a modular multilevel converter 10 having multiple outputs may include a medium-voltage direct current (MVDC) power distribution system 20, a low-voltage alternating current (LVAC) power distribution system 70, the modular multilevel converter 10, and a propulsion motor 30. In this case, the modular multilevel converter 10 may be disposed between the high-voltage DC power distribution system 20 and the propulsion motor 30.

[0100] Unlike the power system using the modular multilevel converter having a single output terminal shown in Figures 5a and 5b, the modular multilevel converter 10 of the power system shown in Figures 7a and 7b has multiple outputs, so no separate inverter is required to supply power to the service load or the corresponding low-voltage AC distribution line 70. This allows the power system to be implemented more compactly and simply, reduces the number of required parts, improves productivity, and makes management, maintenance, and repair easier.

[0101] As an example, at least some of an energy storage system (ESS), a fuel cell system (SOFC), a diesel generator (DG), and a shaft generator may be used as a power supply source for supplying power to the high voltage DC power distribution 20.

[0102] For example, an energy storage system (ESS) and a solid oxide fuel cell (SOFC) system may directly generate DC power to be supplied to the high voltage DC power distribution system 20. That is, a separate AC / DC conversion process may not be required.

[0103] As another example, a diesel generator (DG) and a shaft generator (Shaft Generator) may indirectly generate DC power to be supplied to the high voltage DC distribution system 20. That is, a separate process may be required to convert the AC power generated by the diesel generator (DG) and the shaft generator (Shaft Generator) into DC power.

[0104] In addition, to prevent accidents, the modular multilevel converter 10 having multiple outputs and the service load 70 may be electrically connected via an isolation transformer. In this case, the isolation transformer may be either a two-winding transformer or a three-winding transformer.

[0105] 8a to 8c illustrate an embodiment in which, in a power system in which the modular multilevel converter 10 having multiple output terminals described in connection with FIGS. 7a and 7b is arranged between the high-voltage DC distribution 20 and the traction motor 30, a modular multilevel converter 50 having a single output terminal or multiple output terminals is additionally arranged between the high-voltage DC distribution 20 and the generator 60.

[0106] For reference, a modular multilevel converter 10 having multiple output terminals may be used between the high-voltage DC power distribution 20 and the traction motor 30 shown in Figures 8a to 8c, while a general inverter / converter or a modular multilevel converter may be used between the remaining devices (e.g., energy storage system, large motor, etc.) excluding the generator and the high-voltage DC power distribution 20.

[0107] 8a, it can be seen that a modular multilevel converter 50 having a single output end is additionally disposed between the high voltage DC power distribution line 20 and the generator 60. As described above, the modular multilevel converter 50 includes a plurality of sub-modules, which has the effect of reducing the capacity that each sub-module must bear even when the modular multilevel converter 50 is connected to a high-capacity power source (generator).

[0108] 8b, it can be seen that a modular multilevel converter 50 having multiple outputs is additionally disposed between the high voltage DC distribution line 20 and the generator 60. In this case, it can be seen that the main output (high voltage DC power output) of the modular multilevel converter 50 having multiple outputs transmits power to the high voltage DC distribution line 20, and the auxiliary output (low voltage AC power output) transmits power to the service load (LVAC). As an example, the modular multilevel converter 50 having multiple outputs disposed between the high voltage DC distribution line 20 and the generator 60 shown in FIG. 8b may have the same / similar structure as the structure shown in FIG. 4b.

[0109] In this case, to prevent accidents, the modular multilevel converter 50 having multiple outputs and the service load (LVAC) may be electrically connected via an isolation transformer, which may be either a two-winding transformer or a three-winding transformer.

[0110] 8c, it can be seen that a modular multilevel converter 50 having multiple outputs is additionally disposed between the high voltage DC distribution system 20 and the generator 60. In this case, it can be seen that the main output (high voltage DC power output) of the modular multilevel converter 50 having multiple outputs transmits power to the high voltage DC distribution system 20, and the auxiliary output (low voltage DC power output) transmits power to the service load (LVDC). For example, power can be primarily transmitted from the modular multilevel converter 50 having multiple outputs disposed between the high voltage DC distribution system 20 and the generator 60 to the LVDC, and secondarily transmitted from the LVDC to the LVAC via a DC / AC power converter.

[0111] 9a and 9b are schematic diagrams of a power system in which a modular multilevel converter 10 having multiple outputs according to an embodiment disclosed herein is used.

[0112] For reference, the modular multilevel converter with multiple outputs shown in FIGS. 7a and 7b outputs high-voltage AC power for driving the propulsion motor 30 through a first output and low-voltage AC power (LVAC) through a second output, while the modular multilevel converter 10 with multiple outputs shown in FIGS. 9a and 9b outputs high-voltage AC power for driving the propulsion motor 30 through a first output and low-voltage DC power (LVDC) through a second output. This allows LVDC to be provided to onboard loads (e.g., LED lamps) without the need for a separate power conversion device, thereby enabling a more compact and simplified power system, reducing the number of required parts, improving productivity, and facilitating management, maintenance, and repair. Low-voltage AC power may refer to AC power below 1000V, and high-voltage AC power may refer to AC power above 1000V but below 35kV.

[0113] For reference, a modular multilevel converter 10 having multiple outputs may be used between the high voltage DC distribution 20 and the traction motor 30 shown in Figures 9a and 9b, while a general inverter / converter or a modular multilevel converter may be used between the remaining devices (e.g., energy storage system, large motor, etc.) and the high voltage DC distribution 20.

[0114] 9a and 9b, a power system using a modular multilevel converter 10 having multiple outputs may include a medium-voltage direct current (MVDC) power distribution system 20, a low-voltage alternating current (LVDC) power distribution system 80, the modular multilevel converter 10, and a propulsion motor 30. In this case, the modular multilevel converter 10 may be disposed between the high-voltage direct current (MVDC) power distribution system 20 and the propulsion motor 30.

[0115] Similar to the power system shown in Figures 7a and 7b, the modular multilevel converter 10 of the power system shown in Figures 9a and 9b has multiple outputs, so no additional inverter / converter is required to supply power to the service load or the corresponding low-voltage DC distribution line 80.

[0116] As an example, at least some of an energy storage system (ESS), a fuel cell system (SOFC), a diesel generator (DG), and a shaft generator may be used as a power supply source for supplying power to the high voltage DC power distribution 20.

[0117] For example, an energy storage system (ESS) and a solid oxide fuel cell (SOFC) system may directly generate DC power to be supplied to the high voltage DC power distribution system 20. That is, a separate AC / DC conversion process may not be required.

[0118] As another example, a diesel generator (DG) and a shaft generator (Shaft Generator) may indirectly generate DC power to be supplied to the high voltage DC distribution system 20. That is, a separate process may be required to convert the AC power generated by the diesel generator (DG) and the shaft generator (Shaft Generator) into DC power.

[0119] 10a to 10c illustrate an embodiment in which, in a power system in which the modular multilevel converter 10 having multiple output terminals described in connection with FIGS. 9a and 9b is arranged between the high-voltage DC distribution 20 and the traction motor 30, a modular multilevel converter 50 having a single output terminal or multiple output terminals is additionally arranged between the high-voltage DC distribution 20 and the diesel generator (DG).

[0120] For reference, a modular multilevel converter 10 having multiple output terminals may be used between the high-voltage DC power distribution 20 and the traction motor 30 shown in Figures 10a to 10c, while a general inverter / converter or a modular multilevel converter may be used between the remaining devices (e.g., energy storage system, large motor, etc.) excluding the generator and the high-voltage DC power distribution 20.

[0121] 10a, it can be seen that a modular multilevel converter 50 having a single output end is additionally disposed between the high voltage DC power distribution line 20 and the generator. As described above, the modular multilevel converter 50 includes a plurality of sub-modules, which has the effect of reducing the capacity that each sub-module must bear even when the modular multilevel converter 50 is connected to a high-capacity power source (generator).

[0122] 10b, it can be seen that a modular multilevel converter 50 having multiple outputs is additionally disposed between the high-voltage DC distribution line 20 and the generator. In this case, it can be seen that the main output (high-voltage DC power output) of the modular multilevel converter 50 having multiple outputs transmits power to the high-voltage DC distribution line 20, and the auxiliary output (low-voltage AC power output) transmits power to the service load (LVAC). As an example, the modular multilevel converter 50 having multiple outputs disposed between the high-voltage DC distribution line 20 and the generator shown in FIG. 10b may have the same / similar structure as the structure shown in FIG. 4b.

[0123] In this case, to prevent accidents, the modular multilevel converter 50 having multiple outputs and the service load (LVAC) may be electrically connected via an isolation transformer, which may be either a two-winding transformer or a three-winding transformer.

[0124] 10c, it can be seen that a modular multilevel converter 50 having multiple outputs is additionally disposed between the high voltage DC distribution system 20 and the generator. In this case, it can be seen that the main output (high voltage DC power output) of the modular multilevel converter 50 having multiple outputs transmits power to the high voltage DC distribution system 20, and the auxiliary output (low voltage DC power output) transmits power to the service load (LVDC). For example, power can be primarily transmitted from the modular multilevel converter 50 having multiple outputs disposed between the high voltage DC distribution system 20 and the generator to the LVDC, and secondarily transmitted from the LVDC to the LVAC via a DC / AC power converter.

[0125] FIG. 11a is a schematic diagram of a power system including a modular multilevel converter 10 having a single output terminal and a medium-voltage alternating current (MVAC) power distribution system 90 according to one embodiment disclosed in this document.

[0126] For reference, the modular multilevel converter 10 having a single output terminal shown in FIG. 11a receives input of high voltage direct current (MVDC) power and outputs high voltage AC power for driving a load (e.g., a traction motor 30) as described with reference to FIG. 1. Therefore, when a high voltage AC power distribution 90 other than a high voltage DC power distribution is included in the power system, a rectifier terminal 10_1 can be additionally disposed at the front end of the modular multilevel converter 10 having a single output terminal to convert the AC power into DC power and transmit the DC power to the modular multilevel converter.

[0127] For reference, a modular multilevel converter 10 having a single output terminal and a rectifier terminal 10_1 are used between the high voltage AC distribution 90 and the propulsion motor 30 shown in FIG. 11a, while a general inverter / converter or a modular multilevel converter may be used between the high voltage AC distribution 90 and the remaining devices (e.g., an energy storage system (ESS), a fuel cell system (SOFC), a large motor, etc.).

[0128] 11b and 11c are schematic diagrams of a power system including a modular multilevel converter 10 with multiple outputs and a high voltage AC power distribution system 90 according to an embodiment disclosed herein.

[0129] For reference, the power system shown in Figures 11b and 11c is similar to the power system shown in Figure 11a overall, but differs in that it includes a modular multilevel converter having multiple outputs rather than a modular multilevel converter having a single output. That is, since it additionally includes an auxiliary output port that outputs low-voltage AC power, it is possible to supply low-voltage AC power corresponding to a low-voltage load that requires low-voltage AC power without the power conversion device 91 of the power system shown in Figure 11a.

[0130] For reference, a modular multilevel converter 10 having multiple output terminals and a rectifier terminal 10_1 are used between the high voltage AC distribution 90 and the traction motor 30 shown in Figures 11b and 11c, while a general inverter / converter or a modular multilevel converter may be used between the high voltage AC distribution 90 and the remaining devices (e.g., energy storage system, large motor, etc.).

[0131] Similar to what has been described in FIG. 11a, the modular multilevel converter 10 having multiple output terminals in the power system illustrated in FIGS. 11b and 11c receives input of high voltage direct current (MVDC) power and outputs high voltage AC power for driving the traction motor 30. Therefore, if the power system includes a high voltage AC distribution line 90, a rectification terminal 10_1 may be additionally disposed at the front end of the modular multilevel converter 10 having multiple output terminals.

[0132] In this case, to prevent accidents, the modular multilevel converter 10 having multiple outputs and the service load 70 may be electrically connected via an isolation transformer, which may be either a two-winding transformer or a three-winding transformer.

[0133] 11d and 11e are schematic diagrams of a power system including a modular multilevel converter 10 with multiple outputs according to an embodiment disclosed herein and a medium-voltage alternating current (MVAC) power distribution system.

[0134] For reference, the power system shown in Figures 11d and 11e is similar to the power system shown in Figure 11a overall, but differs in that it includes a modular multilevel converter having multiple outputs rather than a modular multilevel converter having a single output. That is, it additionally includes an auxiliary output port that outputs low-voltage DC power, so that low-voltage DC power corresponding to a low-voltage load that requires low-voltage DC power can be supplied without the power conversion device 91 of the power system shown in Figure 11a. Also, the power system shown in Figures 11d and 11e is similar to the power system shown in Figures 11b and 11c overall, but differs in that it outputs DC power rather than AC power from the auxiliary output port.

[0135] For reference, a modular multilevel converter 10 with multiple output terminals and a rectifier terminal 10_1 are used between the high voltage AC distribution 90 and the propulsion motor 30 shown in Figures 11d and 11e, while a general inverter / converter or a modular multilevel converter may be used between the high voltage AC distribution 90 and the remaining devices (e.g., energy storage system, large motor, etc.).

[0136] Similar to what has been described in FIG. 11a, the modular multilevel converter 10 having multiple output terminals in the power system illustrated in FIG. 11d and FIG. 11e receives input of high voltage direct current (MVDC) power and outputs high voltage AC power for driving the traction motor 30. Therefore, when the power system includes a high voltage AC distribution line 90, a rectification terminal 10_1 may be additionally disposed at the front end of the modular multilevel converter 10 having multiple output terminals.

[0137] In addition, low voltage DC power can be sent to low voltage DC distribution (LVDC) as shown in Figure 11d, but power can also be transmitted primarily to low voltage DC distribution (LVDC) as shown in Figure 11e, and then secondarily transmitted from low voltage DC distribution (LVDC) to low voltage AC distribution (LVAC) via an inverter.

[0138] Meanwhile, the rectification terminal 10_1 shown in FIGS. 11a to 11e may have the same / similar structure as a modular multilevel converter having a single output terminal, which will also be described with reference to 12.

[0139] FIG. 12 is a diagram schematically illustrating a modular multilevel converter 10 and a rectification terminal 10_1 disposed at the front end thereof.

[0140] 12, it can be seen that the rectifier terminal 10_1 has the same / similar structure as the modular multilevel converter having a single output terminal described with reference to Fig. 1. That is, the rectifier terminal receives high voltage AC power input from a high voltage AC distribution system (MVAC) through an input terminal, converts it into high voltage direct current (MVDC), and outputs it, and the modular multilevel converter 10 receives high voltage direct current (MVDC) input from the rectifier terminal 10_1 through an input terminal, converts it into AC power, and outputs it to a load terminal (e.g., a motor).

[0141] For reference, in FIG. 12, for convenience, a traction motor is illustrated as an example of a load, but the load of the power system according to one embodiment disclosed in this document is not limited to a traction motor.

[0142] Furthermore, the modular multilevel converter 10 shown in FIG. 12 may be a modular multilevel converter having a single output terminal as shown in FIG. 11a, but is not limited thereto and may be a modular multilevel converter having multiple output terminals as shown in FIGS. 11b and 11c.

[0143] 13a to 13c are schematic diagrams of a power system in which a modular multilevel converter 50 according to an embodiment disclosed herein is disposed between a high voltage DC power distribution system 20 and a generator 60. FIG.

[0144] 13a, for example, a power grid system may include a medium-voltage direct current (MVDC) power distribution system 20, a modular multilevel converter 50 having a single output end, and a generator 60. In this case, the modular multilevel converter 50 having a single output end may be disposed between the medium-voltage direct current (MVDC) power distribution system 20 and the generator 60.

[0145] 13b and 13c, a power grid system may include a high voltage DC distribution system 20, a modular multilevel converter with multiple outputs 50, and a generator 60. In this case, the modular multilevel converter with multiple outputs 50 may be disposed between the high voltage DC distribution system 20 and the generator 60.

[0146] Unlike the power system using the modular multilevel converter 50 having a single output terminal shown in Fig. 13a, the modular multilevel converter 50 of the power system shown in Fig. 13b and Fig. 13c has multiple outputs, so a separate inverter for supplying power to the service load is not required, which allows for effective use of the limited space on the ship and simplifies maintenance and repair.

[0147] For reference, the modular multilevel converter 50 disposed between the high voltage DC distribution system 20 and the generator 60 in FIG. 13b receives AC power input from the generator 60, outputs DC power to the high voltage DC distribution system 20, and outputs low voltage AC power (LVAC) to the low voltage AC distribution system 70 for supplying AC power to the service load, while the modular multilevel converter 50 disposed between the high voltage DC distribution system 20 and the generator 60 in FIG. 13c receives AC power input from the generator 60, outputs DC power to the high voltage DC distribution system 20, and outputs low voltage DC power (LVDC) to the low voltage DC distribution system 80 for supplying AC power to the service load.

[0148] Conventional circuit breakers for high voltage DC power distribution have problems such as high cost, large size, and few commercial products. However, as shown in FIGS. 13a to 13c, when a modular multilevel converter 50 is disposed between a high voltage DC power distribution 20 and a generator 60, a power system without a circuit breaker can be realized, thereby overcoming the above problems.

[0149] 14a to 14j illustrate an embodiment in which a modular multilevel converter 10 having a single output terminal or multiple output terminals is additionally arranged between the high-voltage DC distribution 20 and a propulsion motor (Prop. Motor) 30 in the power system in which the modular multilevel converter 50 is arranged between the high-voltage DC distribution 20 and the generator 60 described in connection with FIGS. 13a and 13c.

[0150] First, referring to FIG. 14a, it can be seen that in a power system in which a modular multilevel converter 50 having a single output end is arranged between a high voltage DC distribution line 20 and a generator 60, an additional modular multilevel converter 10 having a single output end is arranged between the high voltage DC distribution line 20 and a traction motor 30.

[0151] 14b, it can be seen that in a power system in which a modular multilevel converter 50 having a single output port is arranged between a high-voltage DC distribution line 20 and a generator 60, a modular multilevel converter 10 having multiple output ports is additionally arranged between the high-voltage DC distribution line 20 and a traction motor 30. For reference, FIG. 14b illustrates a case in which the modular multilevel converter 10 having multiple output ports transmits low-voltage DC power to the low-voltage DC distribution line 80 via an auxiliary output port (e.g., a second output port), but the present invention is not limited thereto. For example, the modular multilevel converter 10 having multiple output ports may transmit low-voltage AC power to the low-voltage AC distribution line via an auxiliary output port (e.g., a second output port).

[0152] Also, referring to Figures 14c to 14e, it can be seen that in a power system in which a modular multilevel converter 50 having multiple output terminals is arranged between a high-voltage DC distribution line 20 and a generator 60, a modular multilevel converter 10 having a single output terminal or multiple output terminals is additionally arranged between the high-voltage DC distribution line 20 and a traction motor 30.

[0153] For reference, in FIG. 14c, a modular multilevel converter 10 having a single output end is additionally arranged between a high-voltage DC power distribution line 20 and a traction motor 30, and it can be seen that a separate power conversion device 40 is additionally required to supply power to the service load.

[0154] Meanwhile, the modular multilevel converter 10 additionally disposed between the high voltage DC distribution line 20 and the traction motor 30 shown in Figures 14d and 14e has multiple output terminals, so it can be seen that no separate power conversion device is required to supply power to the service load.

[0155] For reference, Figure 14d illustrates a case where a modular multilevel converter 10 having multiple output terminals transmits low-voltage AC power to a low-voltage AC distribution system 70 via an auxiliary output terminal (e.g., a second output terminal), while Figure 14e illustrates a case where a modular multilevel converter 10 having multiple output terminals transmits low-voltage DC power to a low-voltage DC distribution system 80 via an auxiliary output terminal (e.g., a second output terminal).

[0156] Also, referring to Figures 14f to 14j, it can be seen that in a power system in which a modular multilevel converter 50 having multiple output terminals is arranged between a high-voltage DC distribution line 20 and a generator 60, a modular multilevel converter 10 having a single output terminal or multiple output terminals is additionally arranged between the high-voltage DC distribution line 20 and a traction motor 30.

[0157] For reference, in the power system illustrated in Figures 14c to 14e described above, the modular multilevel converter 50 having multiple output terminals arranged between the high-voltage DC distribution line 20 and the generator 60 receives high-voltage AC power input from the generator and outputs high-voltage DC power and low-voltage AC power, while in the power system illustrated in Figures 14f to 14j, the modular multilevel converter 50 having multiple output terminals arranged between the high-voltage DC distribution line 20 and the generator 60 receives high-voltage AC power input from the generator and outputs high-voltage DC power and low-voltage DC power.

[0158] 14f and 14g, it can be seen that in a power system in which a modular multilevel converter 50 having multiple output ports is arranged between a high-voltage DC distribution line 20 and a generator 60, an additional modular multilevel converter 10 having multiple output ports is arranged between the high-voltage DC distribution line 20 and a traction motor 30. For reference, FIG. 14f illustrates a case in which the additional modular multilevel converter 10 transmits low-voltage AC power to a low-voltage AC distribution line 70 via an auxiliary output port (e.g., a second output port), while FIG. 14g illustrates a case in which the additional modular multilevel converter 10 transmits low-voltage DC power to a low-voltage DC distribution line 80 via an auxiliary output port (e.g., a second output port).

[0159] 14h, when compared with the power system shown in FIG. 14f, the power system is the same in that power is converted and transmitted from a modular multilevel converter 50 disposed between a high-voltage DC distribution line 20 and a generator 60 to a low-voltage DC distribution line 80, but differs in that power is additionally transmitted from the low-voltage DC distribution line 80 to a low-voltage AC distribution line 70 via a separate inverter. Also, the power system shown in FIG. 14f differs in that a modular multilevel converter 10 having multiple outputs is additionally disposed between the high-voltage DC distribution line 20 and the traction motor 30, while the power system shown in FIG. 14h differs in that a modular multilevel converter 10 having a single output is additionally disposed between the high-voltage DC distribution line 20 and the traction motor 30.

[0160] Also, referring to Figure 14i, when compared with the power system shown in Figure 14f, it is common that power is converted and transmitted from a modular multilevel converter 50 arranged between a high-voltage DC distribution line 20 and a generator 60 to a low-voltage DC distribution line 80, but in Figure 14i, there is a difference in that power is additionally transmitted from the low-voltage DC distribution line 80 to a low-voltage AC distribution line 70 via a separate inverter.

[0161] Also, referring to FIG. 14j, when compared with the power system shown in FIG. 14i, there is a difference in that a modular multilevel converter 10 additionally arranged between the high-voltage DC distribution line 20 and the traction motor 30 transmits DC power to the low-voltage DC distribution line 80.

[0162] In addition, the traction motor 30 requires a large amount of power, and if a modular multilevel converter 10 is additionally disposed between the high-voltage DC power distribution system 20 and the traction motor 30 according to one embodiment disclosed herein, power can be stably supplied to the traction motor 30.

[0163] Meanwhile, Figures 15a to 15d schematically illustrate a power system in which the grids of essential loads and service loads are separated according to one embodiment disclosed herein.

[0164] For reference, the essential load terminal refers to a load that is essential for operating a ship, and the service load terminal refers to a load that can be varied to suit the situation. The essential load terminal supplies constant power, while the service load terminal can variably supply power.

[0165] Conventionally, since the essential load end and the service load end are included in the same grid, there has been a problem in that it is not easy to control the service load end.

[0166] On the other hand, as shown in Figures 15a to 15d, if the grid 1600 at the essential load end and the grid 1700 at the service load end are separated, the service load end can be easily controlled, thereby enabling efficient power management.

[0167] First, referring to FIGS. 15a and 15b, it can be seen that the first grid 1600 corresponding to the essential load end and the second grid 1700 corresponding to the service load end are electrically isolated.

[0168] The first grid 1600 may include a high-voltage DC power distribution unit 1620, a traction motor 1630, and a modular multilevel converter 1610. The first grid 1600 may additionally include a power supply source for supplying power, such as an energy storage system (ESS), a solid oxide fuel cell (SOFC), a diesel generator (DG), and a shaft generator (large motor). A power conversion device may be used to transfer power supplied from the power supply source to the high-voltage DC power distribution unit 1620. The power conversion device may be a general inverter, converter, or the like, but is not limited thereto, and may be a modular multilevel converter having a single output or multiple outputs. The modular multilevel converter 1610 of the first grid 1600 may be a modular multilevel converter having a single output as shown in FIG. 15b, but is not limited thereto, and may be a modular multilevel converter having multiple outputs as shown in FIG. 15a. As shown in FIG. 15a, when the modular multilevel converter 1610 has multiple output terminals, it is possible to transmit power not only to the traction motor 30 but also to the lower load terminal 1670 at the same time.

[0169] The second grid 1700 may also include low voltage AC distribution 1710 , a service load end 1720 , and a variable speed generator 1730 .

[0170] On the other hand, if a problem occurs in the variable speed generator 1730 included in the second grid 1700, a situation may occur in which power is not supplied to the service load end 1720. Therefore, basically, the first grid 1600 and the second grid 1700 are electrically isolated as shown in Figures 15a and 15b, but depending on the situation, power from the first grid 1600 can be additionally transmitted to the second grid 1700 through a switching operation as shown in Figures 15c and 15d.

[0171] As an example, as shown in FIG. 15c, a switch 1640 is disposed between the auxiliary output (second output) of a modular multilevel converter 1610 having multiple outputs of a first grid 1600 and the second grid 1700, so that power from the first grid 1600 can be shared with the second grid 1700 in an emergency. Compared to the power system of FIG. 15a, it can be seen that a switch 1640 is added to the auxiliary output of the modular multilevel converter 1610 having multiple outputs of the first grid 1600 in FIG. 15c. For reference, FIG. 15c illustrates the modular multilevel converter 1610 of the first grid 1600 transmitting low-voltage AC power to the second grid 1700, but this is not limiting. For example, the modular multilevel converter 1610 of the first grid can also transmit low-voltage DC power to the second grid.

[0172] 15d, a switch 1640 is arranged between a modular multilevel converter 1650 having a single output terminal of a first grid 1600 and a high voltage DC distribution line 1620, so that in an emergency, the power of the first grid 1600 can be shared with a second grid 1700. When compared with the power system of FIG. 15b, it can be seen that a switch 1640 is additionally connected to the high voltage DC distribution line 1620 of the first grid 1600 in FIG. 15d, and a modular multilevel converter 1650 having a single output terminal is additionally arranged between the switch 1640 and the second grid 1700.

[0173] The above description is merely an illustrative example of the technical concept of the present invention, and various modifications and variations are possible by those skilled in the art without departing from the essential characteristics of the present invention.

[0174] Therefore, the embodiments disclosed in the present invention are for illustrative purposes only and are not intended to limit the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted according to the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims

1. a first converter unit having legs corresponding to preset phases, each of the legs having an upper arm and a lower arm, the upper arm and the lower arm each having a plurality of sub-modules connected in series, converting DC power input to an input terminal into AC power having the phases and outputting the AC power through a first output terminal; and a second converter unit that converts the DC power input to the input terminal into AC power having a voltage level lower than a voltage level of the AC power output from the first converter unit and outputs the AC power through a second output terminal.

2. The second converter unit is a first low-voltage converter unit including a plurality of additional sub-modules connected in series to the upper arms of the legs of the first converter unit in a full-bridge configuration, wherein adjacent additional sub-modules are connected in parallel to each other, and the plurality of additional sub-modules convert the DC power at the input end into AC power having a voltage level lower than that of the AC power output from the first converter unit; and 2. The modular multilevel converter of claim 1, comprising a plurality of additional sub-modules in a full-bridge configuration connected in series with the lower arms of the legs of the first converter unit, adjacent plurality of additional sub-modules connected in parallel with each other, and the plurality of additional sub-modules including at least one second low-voltage converter unit that converts DC power at the input end into AC power having a voltage level lower than a voltage level of AC power output from the first converter unit.

3. The modular multilevel converter according to claim 2 , further comprising a control unit that controls power conversion of the first low-voltage converter unit and the second low-voltage converter unit.

4. 2. The modular multilevel converter according to claim 1, wherein the first converter unit is a bidirectional converter that, when AC power is input to the first output terminal, converts the AC power input to the first output terminal into a predetermined DC power and outputs the DC power to the input terminal.

5. 2. The modular multilevel converter according to claim 1, wherein the first converter unit and the second converter unit convert the DC power of the input terminal into three-phase AC power having different voltage levels and output the converted power.

6. a first modular multilevel converter having multiple outputs; a propulsion motor receiving AC power from a first output terminal of the multiple output terminals; a low-voltage alternating current (ALC) power distribution unit receiving AC power from a second output terminal of the multiple output terminals; and A power grid system including a medium-voltage direct current (MDC) distribution system for supplying DC power to the first modular multilevel converter.

7. The power system according to claim 6, wherein a voltage level of the AC power output through the second output terminal is lower than a voltage level of the AC power output through the first output terminal.

8. 7. The power grid system according to claim 6, wherein the DC power supplied to the first modular multilevel converter through the high-voltage DC distribution line is generated directly or indirectly by at least one of an energy storage system, a fuel cell system, and a generator.

9. The power grid system according to claim 8, further comprising a second modular multilevel converter electrically connected to the generator and the high voltage DC distribution line, the second modular multilevel converter having at least one output terminal.

10. 10. The power grid system according to claim 9, wherein the second modular multilevel converter has a third output terminal for outputting DC power to the high-voltage DC distribution system and a fourth output terminal for outputting AC power to a service load distribution system.

11. 10. The power grid system according to claim 9, wherein the second modular multilevel converter has a fifth output terminal for outputting DC power to the high-voltage DC distribution system and a sixth output terminal for outputting DC power to a service load distribution system.

12. The power system according to claim 11, wherein a voltage level of the DC power output through the sixth output port is lower than a voltage level of the DC power output through the fifth output port.

13. The power system according to claim 6, wherein the second output terminal and the low voltage AC power distribution are electrically connected via an isolation transformer.

14. The power system according to claim 13, wherein the isolation transformer is one of a two-winding transformer and a three-winding transformer.

15. The power system according to claim 6, further comprising a bus tie connected to the high voltage DC distribution line for exchanging DC power with another power system.

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