Uninterruptible power conversion system and method

Abstract

An uninterruptible power switching system according to one embodiment of the present invention comprises a ship power supply unit that supplies ship power to an onboard load, a shore power supply unit that supplies shore power to the onboard load, a ship power circuit breaker that connects or disconnects between the onboard load and the ship power supply unit, a shore power circuit breaker that connects or disconnects between the onboard load and the shore power supply unit, and a static frequency converter (SFC) that measures the magnitude and phase of a shore voltage supplied to the onboard load and supplies ship voltage to the onboard load by synchronizing with the magnitude and phase of the measured shore voltage.

Description

Technology Field

[0001] The present invention relates to an uninterruptible power switching system and an uninterruptible power switching method for switching from shore power to ship power without power outage when a ship departs. Background Technology

[0002] When a vessel is anchored at the coast, shore power can be connected to supply power to onboard loads, such as hotel loads, or to charge onboard batteries. When the vessel departs, the shore power can be disconnected, and the vessel's power can be supplied to the onboard loads using onboard batteries or onboard generators.

[0003] According to the existing system, momentary power outages may occur when a vessel departs due to a lack of synchronization between the shore power and the ship's power supply. This is because the shore power system lacks a synchronization control function to align the two, requiring the ship's power to be supplied only after the shore power is cut off.

[0004] Furthermore, under the existing system, ship power cannot be connected simultaneously with shore power; therefore, ship power must be supplied only after the shore power is disconnected. Consequently, momentary power outages may occur in the existing system, which can lead to issues such as complaints on passenger ships where customer convenience is paramount.

[0005] With the global adoption of battery systems on ships and the increasing demand for using shore power while anchored, there is a growing need for control systems and methods capable of switching from shore power to ship power without power outages during departure or anchoring.

[0006] (Patent Document 1) Republic of Korea Published Patent Application No. 10-2022-0055592

[0007] (Patent Document 2) Republic of Korea Published Patent Application No. 10-2012-0070551

[0008] (Patent Document 3) Republic of Korea Published Patent Application No. 10-2013-0070855 The problem to be solved

[0009] One objective of the present invention is to synchronize land power and ship power when a ship departs, thereby switching from land power to ship power without a power outage.

[0010] In addition, the present invention has the purpose of supplying power without interruption by operating the onshore power and the ship power in parallel and allowing the transition to be made gradually when switching from onshore power to ship power.

[0011] The objectives of the present invention are not limited to the problems mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0012] To achieve the above objectives, the present invention provides the following uninterruptible power switching system.

[0013] An uninterruptible power switching system according to one embodiment of the present invention may include a ship power supply unit that supplies ship power to an onboard load, a shore power supply unit that supplies shore power to the onboard load, a ship power circuit breaker that connects or disconnects between the onboard load and the ship power supply unit, a shore power circuit breaker that connects or disconnects between the onboard load and the shore power supply unit, and a static frequency converter (SFC) that measures the magnitude and phase of a shore voltage supplied to the onboard load and supplies ship voltage to the onboard load by synchronizing with the magnitude and phase of the measured shore voltage.

[0014] An uninterruptible power switching method according to one embodiment of the present invention includes a shore power supply step for supplying shore power to an onboard load, a parallel supply step for measuring the magnitude and phase of a shore voltage supplied to the onboard load and supplying a ship voltage to the onboard load in synchronization with the magnitude and phase of the measured shore voltage, and a shore power cutoff step for cutting off the shore power supplied to the onboard load. Effects of the invention

[0015] According to one embodiment of the present invention, by enabling a transition from shore power to ship power without power outage upon departure, passenger satisfaction can be increased and the stability of ship operations can be enhanced. Brief explanation of the drawing

[0016] FIG. 1 shows an uninterruptible power switching system according to one embodiment of the present invention. FIG. 2 is a drawing for explaining the configuration of an SFC converter according to one embodiment of the present invention in more detail. FIGS. 3a and 3b are graphs illustrating a droop control method of an uninterruptible power switching system according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating an uninterruptible power conversion method according to one embodiment of the present invention. Specific details for implementing the invention

[0017] Hereinafter, preferred embodiments are described in detail with reference to the attached drawings so that those skilled in the art can easily practice the present invention. However, in describing the preferred embodiments of the present invention in detail, if it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Additionally, the same reference numerals are used throughout the drawings for parts having similar functions and operations.

[0018] Additionally, throughout the specification, when a part is described as being 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between. Furthermore, the description of a component as 'including' means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0019] The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0021] FIG. 1 shows an uninterruptible power switching system according to one embodiment of the present invention.

[0022] Referring to FIG. 1, an uninterruptible power switching system according to one embodiment of the present invention includes a ship power supply unit (10), a land power supply unit (20), a static frequency converter (SFC) (30), a ship power circuit breaker (50), a land power circuit breaker (60), and a system control unit (70).

[0023] The ship power supply unit (10) may include a generator or battery installed inside the ship, and may further include an inverter, a converter, and a DC switchboard, etc. The ship power supply unit (10) can supply power required for onboard loads (L), such as hotel loads, during the operation of the ship using the ship's own independent power source.

[0024] The shore power supply unit (20) may be a facility that supplies power at a port or dock while the ship is anchored. While the ship is sailing, it supplies power using the ship power supply unit (10), but when anchored, it can use the shore power supply unit (20) to charge batteries or supply shore power to onboard loads.

[0025] SFC (30) is a type of converter that is placed on a DC switchboard and can convert the DC signal of the ship's power into an AC signal when supplying power to the ship, and can supply power to onboard loads (L) including hotel loads, which are onboard constant frequency and constant voltage loads.

[0026] More specifically, when the shore power mode is off, the SFC (30) can convert the ship's power from a DC signal to an AC signal and supply it to the onboard load. And when the shore power mode is on, the SFC (30) can convert the shore power from an AC signal to a DC signal and supply it to the DC switchboard. In this specification, the case where the SFC (30) is in shore power mode off may be described.

[0027] And when the uninterruptible power switching system is activated while the ship is anchored, the SFC (30) can sense the magnitude and phase of the onshore voltage supplied to the onboard load when onshore power is supplied and control the SFC (30) output voltage to be synchronized with the onshore voltage.

[0028] And the SFC (30) can enable parallel operation of onshore power and ship power, and can play a role in shifting from onshore power to ship power without power outage by gradually increasing the load rate of ship power. This will be described in more detail below in the description of FIGS. 3a and FIGS. 3b.

[0029] The shore voltage may refer to the voltage supplied from the shore power supply unit (20) to the input terminal of the onboard load. The ship voltage may refer to the voltage supplied by the ship power supply unit (10) to the input terminal of the onboard load when the ship power breaker (50) is closed.

[0030] And the ship power circuit breaker (50) and the shore power circuit breaker (60) are composed of circuit breakers (CB) and can be opened or closed according to preset standards. In addition, the ship power circuit breaker (50) can be controlled to open or close by the SFC (30), and the shore power circuit breaker (60) can be controlled to open or close by the system control unit (70).

[0031] The ship power breaker (50) is connected to the onboard load input terminal and can connect or disconnect the onboard load and the ship power unit (10). Connecting the onboard load and the ship power unit (10) may include direct connection or indirect connection. For example, the ship power breaker (50) can indirectly connect the onboard load and the ship power unit (10) through the SFC (30).

[0032] When only shore power is supplied to the onboard load, the ship power circuit breaker (50) is turned off and the shore power circuit breaker (60) can be turned on. The SFC (30) can sense the shore voltage supplied to the onboard load and control the SFC output voltage to be synchronized with the shore voltage. More specifically, the SFC measures the voltage magnitude difference or phase difference between the two ends of the turned-off ship power circuit breaker (50), and when the voltage difference or phase difference is below a certain value, it controls the ship power circuit breaker (50) to be turned on so that ship power can be supplied to the onboard load.

[0033] The onshore power circuit breaker (60) can be controlled by the system control unit (70) and connected to the onshore load input terminal to connect or disconnect the onshore load and the onshore power unit (20). Connecting the onshore load and the onshore power unit (20) may include direct or indirect connection. When the onshore power circuit breaker (60) is turned off, the onshore power generated by the onshore power unit (20) may not be delivered to the onshore load. When the onshore power circuit breaker (60) is turned on, the onshore power generated by the onshore power unit (20) may be delivered to the onshore load.

[0034] The onboard load (L) is the basic load required to operate the vessel and may include loads required for hotel loads, facilities for crew or passengers, or various driving assistance equipment.

[0035] And the system control unit (70) can be configured to convert power supplied to the onboard load from land power to ship power based on droop control.

[0036] Droop control is a method in which the speed of the prime mover is adjusted to match the system frequency when a generator is connected to the grid and operating. It controls the turbine connected to the grid to maintain the system frequency under a constant output by changing the reference signal in proportion to the difference between the actual turbine speed and the speed reference signal.

[0037] The system control unit (70) can transmit a control signal to the SFC (30) based on droop control. The system control unit (70) can generate a control signal that instructs the y-intercept of the droop curve to rise by sending a y-intercept up-down signal of the droop curve so that the output power is set to a value higher than the current SFC (30) output, and transmit it to the SFC control unit (32).

[0038] More specifically, the system control unit (70) can transmit a control signal to the SFC (30) indicating a frequency increase of the active power droop curve and a voltage increase of the reactive power droop curve. The SFC (30) can increase the output of active power at the same frequency based on the frequency increase control signal of the active power droop curve, and can increase the output of reactive power at the same voltage based on the voltage increase control signal of the reactive power droop curve.

[0039] The SFC control unit (32) can control the output active power and reactive power of the SFC (30) based on a control signal so that the load rate of the ship power supplied by the ship power unit (10) gradually increases. For example, the SFC control unit (32) can control the output of the SFC (30) so that the load rate of the ship power increases from 0% to 100%.

[0040] And the system control unit (70) measures the current of the land power circuit breaker (60) to measure the load rate of the land power, and can control the land power circuit breaker (60) to be cut off when the load rate of the land power is lower than a preset value.

[0042] FIG. 2 is a drawing for explaining the operation of an SFC according to one embodiment of the present invention in more detail.

[0043] Referring to FIG. 2, an SFC (30) according to one embodiment of the present invention may include a converter (31), an SFC control unit (32), a first connection unit (33), a second connection unit (34), and a transformer (35).

[0044] The converter (31) can convert the DC signal of the power supplied from the ship's power supply unit (10) into an AC signal. The output terminal of the converter (31) can be connected to a transformer (35), and the output terminal of the transformer (35) can be connected to one end of the ship's power circuit breaker (50).

[0045] The ship power generated from the ship power supply unit (10) can be transmitted to the SFC (30) via a DC switchboard. The SFC (30) can convert the ship power from a DC signal to an AC signal.

[0046] And the transformer (35) can convert the output voltage of the converter (31) to a preset voltage ratio. In one embodiment, the transformer (35) can convert an AC voltage of 660V to an AC voltage of 450V.

[0047] Additionally, the SFC (30) can be controlled by the system control unit (70) or the SFC control unit (32), which is the control unit of the SFC (30).

[0048] The SFC control unit (32) can perform SFC output control of a constant frequency and a constant voltage. The SFC control unit (32) can measure the magnitude and phase of the voltage at both ends of the ship power breaker (50) at the start and synchronize them to close the ship power breaker (50). Additionally, the SFC control unit (32) can control the magnitude and phase of the ship voltage to match the magnitude and phase of the shore voltage, and the SFC control unit (32) can sense the voltage at both ends of the ship power breaker (50) and control the ship power breaker (50) to close when the magnitude and phase of the ship voltage supplied to the onboard load match the magnitude and phase of the shore voltage supplied to the onboard load.

[0049] And the SFC (30) may include a first connection part (33) connecting one end of the SFC control part (32) and the ship power breaker (50), and a second connection part (34) connecting the other end of the SFC control part (32) and the ship power breaker (50). At this time, one end of the ship power breaker (50) may be connected to the output terminal of the SFC (30), and the other end of the ship power breaker (50) may be connected to an onboard load (L).

[0050] The SFC control unit (32) can measure the voltage difference or phase difference between both ends of the ship power circuit breaker (50) using the first connection unit (33) and the second connection unit (34), and control the ship power circuit breaker (50) to be closed when the voltage difference or phase difference is below a certain value.

[0051] The SFC (30) can receive feedback of the AC voltage of the onshore power supplied to the onboard load through the second connection part (34), and can use this to synchronize the output of the SFC (30) with the AC distribution panel.

[0052] The uninterruptible power switching system of the present invention aims for uninterrupted power, and to this end, it can perform parallel operation between the Shore power and the SFC (30) output by utilizing an SFC (30) having a synchronous function. The SFC (30) uses a Droop Function to switch the load supplied by the Shore power to the onboard power source, and can complete the uninterruptible sequence by opening the Shore power circuit breaker (60) (Shore CB) at a certain load (within 10% of the breaking capacity).

[0054] FIGS. 3a and 3b are graphs illustrating a droop control method of an uninterruptible power switching system according to an embodiment of the present invention.

[0055] The system control unit (70) operates the onshore power and the ship power in parallel and generates a control signal that indicates the frequency and voltage of the droop control curve when switching from the onshore power to the ship power. When the y-intercept of the droop control curve rises, the output active power increases at the frequency of the SFC output voltage (e.g., 60Hz) and the output reactive power can increase at the magnitude of the SFC output voltage (e.g., 450V).

[0056] Referring to Fig. 3a, when the system control unit instructs a frequency increase of the active power droop control curve, the operating point rises from line (a) to line (b). Accordingly, at the SFC output frequency (w*), the SFC output active power P (a) P in * (b) It rises to *.

[0057] Referring to FIG. 3b, when the system control unit directs a voltage rise in the reactive power droop control curve, the operating point rises from line (a) to line (b). Accordingly, at the SFC output voltage (V*), the SFC output reactive power is Q (a) Q from * (b) It rises to *.

[0058] And as the power supplied to the onboard load from the ship power supply unit (10) increases (0%->100%), the onshore power supply unit (20) can reduce the supply power (100%->0%). And the system control unit (70) can measure the current on the side of the onshore power circuit breaker (60) and if the supply power of the onshore power is lower than the reference power (e.g., 20% of the rating), it can cut off the onshore power circuit breaker to cut off the onshore power supply.

[0060] FIG. 4 is a flowchart illustrating an uninterruptible power conversion method according to one embodiment of the present invention.

[0061] Referring to FIG. 4 together with FIG. 1, an uninterruptible power conversion method according to one embodiment of the present invention includes a land power supply step (S410), a ship power supply step (S420), a load transfer step (S430), and a land power cutoff step (S440).

[0062] In step S410, the onshore power supply unit (20) can supply onshore power to the onboard load. At this time, the onshore power supply unit (20) can supply 100% of the onboard load.

[0063] In step S420, the SFC (30) can measure the magnitude and phase of the shore voltage supplied to the onboard load and supply the ship voltage to the onboard load by synchronizing with the magnitude and phase of the measured shore voltage. More specifically, the SFC (30) can measure the magnitude and phase of the voltage at both ends of the ship power breaker (50) while the shore power breaker (60) is closed and the ship power breaker (50) is closed. At this time, one end of the ship power breaker (50) may be connected to the output terminal of the SFC (30), and the other end may be connected to the onboard load (L), and the ship load (L) may be in a state where only shore power is supplied. Then, the SFC (30) can control the output so that the magnitude and phase of the ship voltage are synchronized or matched with the magnitude and phase of the measured shore voltage. And the SFC (30) can control the ship power breaker (50) to be closed when the magnitude and phase of the ship voltage match the magnitude and phase of the shore voltage supplied to the onboard load. Alternatively, the ship power breaker (50) can be closed when the voltage difference or phase difference between the two ends of the ship power breaker (50) is less than or equal to a certain value, by determining that the magnitude and phase of the ship voltage match the magnitude and phase of the shore voltage.

[0064] And in step S430, the load rate of the onshore power supplied by the onshore power supply unit (20) can be gradually lowered from 100%, and the load rate of the ship power supplied by the ship power supply unit (10) can be gradually increased from 0%. More specifically, the system control unit (70) transmits a control signal to the SFC control unit that instructs the frequency of the active power droop curve and the voltage of the reactive power droop curve to rise based on droop control, and the SFC control unit can control the active power and reactive power output by the SFC to rise based on the control signal.

[0065] And in step S440, the system control unit (70) can cut off the onshore power supplied to the onshore load by controlling the onshore power circuit breaker (60) to be cut off when the onshore power supplied to the onshore load is lower than a preset value.

[0066] The system control unit (70) can control the onshore power circuit breaker (60) to open so that the onshore power supply is cut off when the onshore power supplied to the onshore load is lower than a preset value, for example, when the load rate of the onshore power is 20% or 10% or less.

[0068] AC land power and DC land power are applied worldwide, and in the case of DC land power, this function can be implemented based on the DC Voltage Droop of the power in the DC electric propulsion system.

[0069] Although the above description of the present invention has focused on DC distribution vessels, it can be used in the same way on AC distribution vessels.

[0070] In DC distribution vessels, the PEMS controls the output voltage magnitude of the DC / DC converter, but in AC distribution vessels, the output voltage frequency of the DC / AC inverter can be controlled in the same way.

[0072] In describing the present invention, the '~ part' may be implemented in various ways, for example, by a processor, program instructions executed by the processor, a software module, microcode, a computer program product, a logic circuit, an application-specific integrated circuit, firmware, etc.

[0073] The content of the method disclosed in the embodiments of the present application may be directly implemented by a hardware processor, or it may be implemented and completed by a combination of hardware and software modules within the processor. The software module may be stored in a conventional storage medium such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in memory, and the processor reads the information stored in memory and combines it with the hardware to complete the content of the method described above. To avoid duplication, a detailed description is omitted herein.

[0074] The present invention is not limited by the embodiments described above and the attached drawings. The scope of rights is intended to be limited by the attached claims, and it will be obvious to those skilled in the art that various substitutions, modifications, and changes can be made within the scope of the technical concept of the present invention as described in the claims. Explanation of the symbols

[0075] 10: Ship power supply 20: Land Power Supply 30: SFC 31: Converter 32: SFC Control Unit 33: First connection 34: Second connection 35: Transformer 50: Ship power breaker 60: Land power breaker 70: System Control Unit

Claims

Claim 1 A ship power supply unit that supplies ship power to onboard loads; a shore power supply unit that supplies shore power to said onboard loads; a ship power breaker that connects or disconnects between said onboard loads and said ship power supply unit; a shore power breaker that connects or disconnects between said onboard loads and said shore power supply unit; a static frequency converter (SFC) that receives direct current power from said ship power supply unit and converts it into alternating current power, measures the magnitude and phase of the shore voltage supplied to said onboard loads at the onboard load side of said ship power breaker, supplies ship voltage to said onboard loads by synchronizing with the magnitude and phase of said measured shore voltage, and controls said ship power breaker to be closed when the magnitude and phase of said ship voltage match the magnitude and phase of said measured shore voltage; An uninterruptible power switching system comprising a system control unit that, after the ship power breaker is switched on, increases the output power of the SFC to gradually switch the power supplied to the onboard load from the shore power to the ship power, and controls the shore power breaker to be switched off when the shore power supplied to the onboard load is lower than a preset value. Claim 2 An uninterruptible power switching system according to claim 1, wherein the SFC comprises: a converter that converts a DC signal of the ship's power into an AC signal; and an SFC control unit that controls the output of the converter and the ship's power breaker. Claim 3 delete Claim 4 An uninterruptible power switching system according to paragraph 2, wherein the SFC further comprises: a first connection part connecting one end of the SFC control part and the ship power breaker; and a second connection part connecting the other end of the SFC control part and the ship power breaker. Claim 5 In paragraph 4, an uninterruptible power switching system, wherein one end of the ship power breaker is connected to the output terminal of the SFC and the other end of the ship power breaker is connected to the onboard load. Claim 6 In paragraph 5, the SFC control unit measures the voltage difference or phase difference between one end and the other end of the ship power breaker when the ship power breaker is turned off and the shore power breaker is turned on, and controls the ship power breaker to be turned on when the voltage difference or phase difference is less than or equal to a certain value, in an uninterruptible power switching system. Claim 7 delete Claim 8 An uninterruptible power switching system according to claim 1, wherein the system control unit transmits a control signal to the SFC indicating a frequency increase of the active power droop curve and a voltage increase of the reactive power droop curve based on droop control, thereby controlling the active power and reactive power output by the SFC to increase. Claim 9 delete Claim 10 A method for uninterruptible power switching comprising: a shore power supply step for supplying shore power to an onboard load; a ship power supply step for receiving direct current power from a ship power unit and converting it into alternating current power by means of a static frequency converter (SFC), measuring the magnitude and phase of the shore voltage supplied to the onboard load at the onboard load side of a ship power circuit breaker, supplying ship voltage to the onboard load by synchronizing with the magnitude and phase of the measured shore voltage, and controlling the ship power circuit breaker to be closed when the magnitude and phase of the ship voltage match the magnitude and phase of the measured shore voltage; and a shore power cutoff step for gradually switching the power supplied to the onboard load from the shore power to the ship power by means of a system control unit after the ship power circuit breaker is closed by increasing the output power of the SFC, and cutting off the shore power when the shore power supplied to the onboard load is lower than a preset value. Claim 11 delete Claim 12 In claim 10, the uninterruptible power switching method further comprises a load shifting step of shifting a load from land power to ship power, wherein the load shifting step comprises: a step of transmitting a control signal to the SFC that instructs a frequency increase of the active power droop curve and a voltage increase of the reactive power droop curve based on droop control by the system control unit; and a step of increasing the active power and reactive power output by the SFC based on the control signal by the SFC.

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