Power system for supplying electrical energy to vessel

Abstract

An electrical power system for supplying a ship (120) with a DC voltage from the shore side, the electrical power system comprising: a transformer (101), the primary side of which is connectable to a shore-side AC voltage network (130); a diode or thyristor rectifier (102), the AC voltage terminals of which are connected to the secondary side of the transformer; the electric connector (103) is used for being connected to the ship; and a DC voltage link (104) for transmitting a DC voltage from the DC voltage terminals of the rectifier to the electrical connector. The transformer comprises an on-load tap changer (105) for changing the transformation ratio. The power system includes a controller (106) for controlling the on-load tap changer to control a DC voltage supplied to the vessel. Natural switching of rectifier diodes or thyristors does not cause potentially detrimental high frequency common mode voltages and currents. In addition, the number of power conversions is minimized, which provides energy efficient power transfer.

Description

Technical Field

[0001] This disclosure relates to an electrical system for supplying electricity to a vessel from the shore. Furthermore, this disclosure relates to vessels, which may be, for example, (but not necessarily) ships, small boats, or ferries. Background Technology

[0002] In many cases, it is necessary to supply electricity to the vessel from the shore while it is in berth. The vessel may be, for example, a vessel comprising a rechargeable battery system and an electric propulsion system powered by the rechargeable battery system. Alternatively, the vessel may be a conventional internal combustion engine vessel, and while in berth, it may connect to a shore-side AC voltage network instead of using its auxiliary generator to produce the required electricity.

[0003] It is not always possible to connect shore-side AC voltage networks to a ship's onboard AC voltage network, as the ship may use a different frequency and / or voltage level. For example, a 50Hz frequency may be used in Europe, while a 60Hz frequency is used in North America. Even when the aforementioned AC voltage networks can be interconnected, berthing times may be relatively long due to the synchronization and phase sequence checks required between the AC voltage networks.

[0004] Patent publication WO2007060189 describes a known solution for connecting a shore-side AC voltage network to a ship. In this solution, a converter is installed on the ship. The shipboard converter is connected to the shore-side AC voltage network via a cable. The shipboard converter is typically a frequency converter used to convert the AC voltage received from the shore-side AC voltage network into an AC voltage with a voltage level and frequency suitable for the ship's AC voltage network. Alternatively, the shipboard converter may be a rectifier used to convert the AC voltage received from the shore-side AC voltage network into a DC voltage with a voltage level suitable for the ship, for example, for charging the ship's batteries. There may also be shore-side converters that replace or are not equivalent to the aforementioned shipboard converters. In many cases, the shore-side converter and / or the shipboard converter are active converters that generate a high-frequency common-mode voltage between the hull and ground, thereby generating a common-mode current between the hull and ground, and thus increasing the likelihood of corrosion of ship components. Summary of the Invention

[0005] The following is a simplified overview to provide a basic understanding of some aspects of various embodiments of the invention. This overview is not a broad overview of the invention. It is neither intended to identify key or essential elements of the invention nor to elucidate the scope of the invention. The following overview presents only some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplary embodiments.

[0006] According to the present invention, a novel power system is provided for supplying DC voltage from the shore to a vessel, which may be, for example, a ship, a small boat, or a ferry. The power system according to the present invention includes: - A transformer, comprising a primary side and a secondary side, the primary side being connectable to a shore-side AC voltage network. - A diode or thyristor rectifier having an AC voltage terminal and a DC voltage terminal, the AC voltage terminal being connected to the secondary side of the transformer, and - An electrical connector capable of connecting to the ship's electrical circuitry, and - A DC voltage link configured to transmit DC voltage from the DC voltage terminal of the diode or thyristor rectifier to the electrical connector.

[0007] The aforementioned transformer includes an on-load tap changer configured to change the transformer's transformation ratio, and the power system includes a controller configured to control the on-load tap changer to control the DC voltage supplied to the vessel, for example, to ramp up the DC voltage during the initial phase of supplying DC voltage to the vessel.

[0008] The natural switching of rectifier diodes or thyristors does not induce potentially harmful high-frequency common-mode voltage (CMV), thus avoiding high-frequency common-mode current (CMC). Therefore, potential corrosion problems to ship components can be eliminated or at least reduced. Furthermore, the amount of power conversion can be minimized for energy-efficient power transmission, as the level of the DC voltage supplied to the ship can be controlled using an on-load tap changer, and in the case of a thyristor rectifier, by controlling the thyristor firing angle. Therefore, a DC-DC converter is typically not required to control the level of the DC voltage supplied to the ship.

[0009] According to the present invention, a new type of vessel is also provided, the vessel comprising: - An electrical connector capable of receiving DC voltage from the shore-side power system. - One or more controllable DC-DC converters. - A control system for controlling the one or more controllable DC voltage converters to convert DC voltage received via the electrical connector into one or more DC voltages suitable for the vessel. - One or more diodes configured to prevent current representing electricity from being transmitted from the vessel via the electrical connector.

[0010] When the DC voltage on the shore side is lower than the DC voltage of the ship's capacitor energy storage device, the one or more diodes prevent unwanted power flow from the ship's capacitor energy storage device to the shore side.

[0011] The ship according to the exemplary and non-limiting embodiments includes a rechargeable battery system for receiving charging energy via the ship's electrical connectors and for supplying power to the ship's propulsion system.

[0012] Exemplary and non-limiting embodiments are described in the appended dependent claims.

[0013] When read in conjunction with the accompanying drawings, the various exemplary and non-limiting embodiments of the construction and operation methods, as well as their additional objects and advantages, will be best understood from the following description of particular exemplary and non-limiting embodiments.

[0014] The verbs “include” and “contain” are used in this document as open-ended restrictions, meaning that they neither exclude nor require the existence of undescribed features.

[0015] Unless otherwise expressly stated, the features described in the dependent claims may be freely combined with each other.

[0016] Furthermore, it should be understood that the use of “one” or “a” throughout this document, i.e., the singular form, does not exclude multiples. Attached Figure Description

[0017] The exemplary and non-limiting embodiments and their advantages are explained in more detail below by way of example and with reference to the accompanying drawings, wherein:

[0018] Figure 1 An electric power system and a ship according to illustrative and non-limiting embodiments are shown, and

[0019] Figure 2a , Figure 2b and Figure 2c Some portions of an electric system according to an illustrative and non-limiting embodiment are shown. Detailed Implementation

[0020] The specific examples provided in the description below should not be construed as limiting the scope and / or applicability of the appended claims. Unless otherwise expressly stated, the list and groups of examples provided in the description below are not exhaustive.

[0021] Figure 1 A schematic diagram of a power system according to an illustrative and non-limiting embodiment is shown. Furthermore, Figure 1A schematic diagram of a vessel 120 according to an illustrative and non-limiting embodiment is shown. The vessel 120 may be, for example, a ship, a small boat, or a ferry. An electrical system is located on the shore side and is arranged to supply power to the vessel 120. The electrical system includes a transformer 101, which includes a primary side and a secondary side. The primary side of the transformer 101 can be connected to a shore-side AC voltage network 130. The electrical system includes a rectifier 102, which has AC voltage terminals and DC voltage terminals. In this illustrative case, the AC voltage terminals of the rectifier 102 are connected to the secondary side of the transformer 101 via an AC series reactor 112. The series reactor 112 suppresses high-frequency current components on the secondary current of the transformer 101 (i.e., on the input current of the rectifier). However, an inductor-capacitor "LC" filter or an inductor-capacitor-inductor "LCL" filter may also be used between the transformer 101 and the rectifier 102. If the stray inductance of the transformer provides sufficient filtering effect, the rectifier can also be directly connected to the secondary side of transformer 101.

[0022] The power system includes an electrical connector 103 and a DC voltage link 104. The electrical connector 103 is connectable to the circuitry of the vessel 120, and the DC voltage link 104 is configured to transfer DC voltage from the DC voltage terminals of the rectifier 102 to the electrical connector 103. The transformer 101 includes an on-load tap changer 105 for changing the transformation ratio of the transformer 101. The power system includes a controller 106 configured to control the on-load tap changer 105 to control the DC voltage supplied to the vessel 120 according to a desired value (i.e., a reference value), for example, to ramp up the DC voltage according to an increasing reference value during the initial phase of supplying DC voltage to the vessel 120. Figure 1 In the exemplary power system shown, transformer 101 includes a star-connected three-phase primary winding 107 and a star-connected three-phase secondary winding 108, and rectifier 102 is a six-pulse thyristor rectifier. The rectifier may also be a six-pulse diode rectifier.

[0023] The advantage of the combination of the on-load tap changer 105 and the thyristor rectifier 102 in transformer 101 is that voltage control can be continuous even if the on-load tap changer 105 changes the voltage in a discrete, step manner. This is because the voltage value between the two positions of the on-load tap changer can be adjusted by regulating the firing angle of the thyristor rectifier 102. On the other hand, the firing angle of the thyristor rectifier 102 can be very small because coarse voltage selection can be performed using the on-load tap changer 105, and therefore only fine-tuning of the voltage is required by adjusting the firing angle. An inherent disadvantage of a large firing angle for the thyristor rectifier 102 is the large amount of reactive power drawn from the shore-side AC voltage network 130 supplied to the thyristor rectifier 102 via transformer 101. Therefore, it is advantageous that a large firing angle is not required due to the on-load tap changer 105.

[0024] The controlled triggering and natural turn-off switching of the rectifier thyristors do not cause potentially harmful high-frequency common-mode voltage "CMV", thus avoiding high-frequency common-mode current "CMC". Therefore, potential corrosion problems to the components of the vessel 120 can be eliminated or at least reduced. Furthermore, the amount of power conversion is minimized to achieve energy-efficient power transmission, as the level of the DC voltage supplied to the vessel 120 can be controlled using an on-load tap changer, and in this exemplary case, by controlling the firing angle of the rectifier thyristors. The power system includes a controller 131 configured to control the firing angle of the rectifier thyristors such that the DC voltage of the DC voltage link 104 has a desired value.

[0025] exist Figure 1 In the illustrated power system, rectifier 102 is connected to DC voltage link 104 via DC series reactor 114. Furthermore, the power system includes capacitor 115 between the terminals of DC voltage link 104. Therefore, in this illustrated case, an inductor-capacitor "LC" filter exists between rectifier 102 and DC voltage link 104.

[0026] In the system according to the exemplary and non-limiting embodiments, the DC voltage terminal of rectifier 102 is connected to ground via overvoltage protector 116. Overvoltage protector 116 may be, for example, a spark gap or metal oxide overvoltage protector. The system according to the exemplary and non-limiting embodiments includes an insulation monitoring device 117 between the DC voltage terminal of rectifier 102 and ground. Insulation monitoring device 117 may be configured to activate an alarm, for example, upon detecting an excessive leakage current between the DC voltage terminal of rectifier 102 and ground.

[0027] Vessel 120 includes an electrical connector 121 for receiving the DC voltage from the aforementioned DC voltage link 104. In this exemplary case, vessel 120 is an electric vessel including a rechargeable battery system 125 for receiving charging energy via the electrical connector 121 and for supplying power to the propulsion system 126. The vessel may also be, for example, a rechargeable hybrid vessel, including a rechargeable battery system and a drivetrain including at least one electric motor and an internal combustion engine. Vessel 120 may also include an inverter 127, or two or more inverters, for converting the DC voltage VDC of the DC voltage link 133 into one or more AC voltages suitable for the AC voltage system 128 of vessel 120. Vessel 120 includes a diode 124 configured to prevent power from being transferred from vessel 120 to the shore side via the electrical connector 121. Figure 1 In the exemplary vessel 120 shown, when the shore-side DC voltage is lower than the DC voltage of the filter capacitor 132, the diode 124 prevents unwanted current from the filter capacitor 132 of the DC voltage link 133.

[0028] The vessel 120 includes a DC voltage converter 122 and a controller 123 for controlling the DC voltage converter 122 to convert the DC voltage received via electrical connector 121 into a DC voltage suitable for the rechargeable battery system 125 during charging. Furthermore, the DC voltage converter 122 is configured to supply electrical energy from the battery system 125 to the DC voltage link 133 when the vessel 120 is not connected to the DC voltage link 104. Advantageously, the DC voltage converter 122 is controlled such that the DC voltage VDC of the DC voltage link 133 remains substantially constant even if the voltage of the rechargeable battery system 125 changes. The vessel 120 may also include one or more other DC voltage converters configured to convert the DC voltage received via electrical connector 121 into one or more DC voltages suitable for various devices and / or systems of the vessel 120.

[0029] Each of the controllers 106, 123, and 131 described above can be implemented using one or more processor circuits. Each processor circuit can be a programmable processor circuit equipped with appropriate software, a dedicated hardware processor (e.g., an application-specific integrated circuit "ASIC"), or a configurable hardware processor (e.g., a field-programmable gate array "FPGA"). Furthermore, each of the controllers described above can include one or more memory circuits, such as random access memory "RAM" circuits.

[0030] Each capacitor 115 and 132 may include one or more capacitor elements, each of which may be, for example, an electric double-layer capacitor element “EDLC”, which may also be referred to as a “supercapacitor”.

[0031] exist Figure 1 In the exemplary power system shown, DC voltage link 104 includes an overcurrent protector 134, and correspondingly, vessel 120 includes an overcurrent protector. Each overcurrent protector may be, for example, a fuse, an overcurrent protection relay, or another protector circuit breaker.

[0032] Figure 1 The illustrated power system includes a power supply circuit breaker 135 for interrupting the power supply from the shore-side AC voltage network 130 to the transformer 101, and a circuit breaker 136 for interrupting the power supply from the power system to the vessel 120. The power supply circuit breakers 135 and 136 can be controlled, for example, by a controller 106, such that these circuit breakers are set to a non-conducting state in response to a fault in the transformer 101, rectifier 102, and / or another part of the power system supplying power from the shore to the vessel.

[0033] Figure 2a A portion of an electrical system for supplying power from shore to a ship, according to an illustrative and non-limiting embodiment, is shown. The transformer 201a of the electrical system includes a three-phase primary winding 207a and two three-phase secondary windings 208a and 208b, whose three-phase voltages have a phase shift relative to each other. In this illustrative electrical system, the first three-phase secondary winding 208a is a star-connected three-phase winding, and the second three-phase secondary winding 209a is a delta-connected three-phase winding. The electrical system includes an inductor-capacitor-inductor “LCL” filter 213 between the rectifier 202a and the secondary windings 208a and 209a of the transformer 201a. In this illustrative case, the rectifier 202a of the electrical system is a twelve-pulse diode rectifier. The rectifier 202a could also be a twelve-pulse thyristor rectifier.

[0034] Figure 2bA portion of an electrical system for supplying power from shore to a ship, according to an illustrative and non-limiting embodiment, is shown. The transformer 201b of the electrical system includes a three-phase primary winding 207b and three three-phase secondary windings 208b, 209b, and 210b, whose three-phase voltages have phase shifts relative to each other. In this illustrative electrical system, the first three-phase secondary winding 208b is a sawtooth-connected three-phase winding, the second three-phase secondary winding 209b is a star-connected three-phase winding, and the third three-phase secondary winding 210b is a sawtooth-connected three-phase winding with opposite handingness to the first three-phase secondary winding 208b. The electrical system includes an inductor-capacitor-inductor (LCL) filter between the rectifier 202b and the secondary windings 208b, 209b, and 210b of the transformer 201b. In this exemplary case, the rectifier 202b of the power system is an eighteen-pulse diode rectifier. The rectifier 202b could also be an eighteen-pulse thyristor rectifier.

[0035] Figure 2c A portion of an electrical system for supplying power from shore to a ship, according to an illustrative and non-limiting embodiment, is shown. The transformer 201c of the electrical system includes a three-phase primary winding 207c and four three-phase secondary windings 208c, 209c, 210c, and 211c, whose three-phase voltages have phase shifts relative to each other. In this illustrative electrical system, the first three-phase secondary winding 208c is a sawtooth-connected three-phase winding, the second three-phase secondary winding 209c is a star-connected three-phase winding, the third three-phase secondary winding 210c is a sawtooth-connected three-phase winding with the opposite rotation direction to the first three-phase secondary winding 208c, and the fourth three-phase secondary winding 211c is a delta-connected three-phase winding. The power system includes an inductor-capacitor-inductor "LCL" filter between the secondary windings 208c, 209c, 210c, and 210c of the rectifier 202c and the transformer 201c. In this exemplary case, the rectifier 202c of the power system is a 24-pulse thyristor rectifier. The rectifier 202c could also be a 24-pulse diode rectifier.

[0036] The specific examples provided in the above specification should not be construed as limiting the applicability and / or interpretation of the appended claims. Unless otherwise expressly stated, the list and groups of examples provided in the above description are not exhaustive.

Claims

1. A power system for supplying DC voltage to a ship from the shore, the power system comprising: - Transformers (101, 201a-201c), wherein the transformers (101, 201a-201c) include a primary side and a secondary side, the primary side being capable of being connected to a shore-side AC voltage network. - A diode or thyristor rectifier (102, 202a-202c), said diode or thyristor rectifier (102, 202a-202c) having an AC voltage terminal and a DC voltage terminal, said AC voltage terminal being connected to the secondary side of said transformer, and - An electrical connector (103), which is capable of being connected to the ship's electrical circuitry, and - A DC voltage link (104), configured to transmit DC voltage from the DC voltage terminal of the diode or thyristor rectifier to the electrical connector. The transformer is characterized in that it includes an on-load tap changer (105) configured to change the transformer's turns ratio, and the power system includes a controller (106) configured to control the on-load tap changer to control the DC voltage supplied to the ship.

2. The power system according to claim 1, wherein, The transformer (101) includes a three-phase primary winding (107) and a three-phase secondary winding (108), and the diode or thyristor rectifier (102) is a six-pulse rectifier.

3. The power system according to claim 1, wherein, The transformer (201a) includes a three-phase primary winding (207a) and two three-phase secondary windings (208a, 209a), whose three-phase voltages have phase shifts relative to each other, and the diode or thyristor rectifier (202a) is a twelve-pulse rectifier.

4. The power system according to claim 3, wherein, The first three-phase secondary winding (208a) in the three-phase secondary winding is a star-connected three-phase winding, and The second three-phase secondary winding (209a) in the three-phase secondary winding is a delta-connected three-phase winding.

5. The power system according to claim 1, wherein, The transformer (210b) includes a three-phase primary winding (207b) and three three-phase secondary windings (208b-210b), whose three-phase voltages have phase shifts relative to each other, and the diode or thyristor rectifier is an eighteen-pulse rectifier.

6. The power system according to claim 5, wherein, The first three-phase secondary winding (208b) of the three-phase secondary winding is a sawtooth-connected three-phase winding, the second three-phase secondary winding (209b) of the three-phase secondary winding is a star-connected three-phase winding, and the third three-phase secondary winding (210b) of the three-phase secondary winding is a sawtooth-connected three-phase winding, and the third three-phase secondary winding (210b) has the opposite rotation direction to the first three-phase secondary winding (208b) of the three-phase secondary winding.

7. The power system according to claim 1, wherein, The transformer (210c) includes a three-phase primary winding (207c) and four three-phase secondary windings (208c-211c), whose three-phase voltages have phase shifts relative to each other, and the diode or thyristor rectifier is a twenty-four pulse rectifier.

8. The power system according to claim 7, wherein, The first three-phase secondary winding (208c) in the three-phase secondary winding is a sawtooth-connected three-phase winding, the second three-phase secondary winding (209c) in the three-phase secondary winding is a star-connected three-phase winding, the third three-phase secondary winding (210c) in the three-phase secondary winding is a sawtooth-connected three-phase winding, the third three-phase secondary winding (210c) has the opposite rotation direction to the first three-phase secondary winding in the three-phase secondary winding, and the fourth three-phase secondary winding (211c) in the three-phase secondary winding is a delta-connected three-phase winding.

9. The power system according to any one of claims 1-8, wherein, The secondary side of the transformer is connected to the AC voltage terminal of the diode or thyristor rectifier via an AC series reactor (112).

10. The power system according to any one of claims 1-9, wherein, The DC voltage terminal of the diode or thyristor rectifier is connected to the DC voltage link via at least one DC series reactor (114).

11. The power system according to any one of claims 1-10, wherein, The power system includes one or more capacitors (115) between the poles of the DC voltage link (104).

12. The power system according to any one of claims 1-11, wherein, The DC voltage terminal of the diode or thyristor rectifier is connected to ground via an overvoltage protector (116).

13. The power system according to any one of claims 1-12, wherein, The power system includes an insulation monitoring device (117) between each of the DC voltage terminals of the diode or thyristor rectifier and ground.

14. A vessel (120), comprising: - Electrical connector (121), which is capable of receiving DC voltage from the shore-side power system. - One or more controllable DC-DC voltage converters (122), and - A controller (123) for controlling the one or more controllable DC voltage converters to convert the DC voltage received via the electrical connector into one or more DC voltages suitable for the vessel. The feature is that the vessel includes one or more diodes (124) configured to prevent current representing electricity from being transmitted from the vessel via the electrical connector.

15. The vessel according to claim 14, wherein, The vessel includes a rechargeable battery system (125), and the one or more controllable DC-DC voltage converters are configured to supply charging energy to the rechargeable battery system.

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