A marine shaft generator grid-connected device

Abstract

The utility model discloses a kind of marine shaft generator grid-connected device, including sequentially connected AC contactor, first transformer, rectifier, inverter, shaft generator, and the first end of AC contactor is connected with AC distribution board;Marine shaft generator grid-connected device further includes pre-charging module, pre-charging module includes sequentially connected second transformer, uncontrolled rectification unit and soft starting unit, and pre-charging module is connected with AC power grid by the primary side of second transformer;The output end of soft starting unit is connected in parallel on the DC bus between the inverter and rectifier.The marine shaft generator grid-connected device provided by the utility model realizes the flexible power-on of DC bus using soft starting unit, and the voltage difference of AC contactor two ends is adjusted using transformer to ensure the smoothness of grid operation, and the device also has good scene adaptability.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to a marine shaft-driven generator grid connection device. Background Technology

[0002] As a major carrier of global trade, shipping's operational economy and energy efficiency are increasingly valued. Ship-driven generator grid connection systems, as an effective energy-saving technology, have been widely applied to various types of vessels. The basic principle of this system is to utilize the surplus power of the ship's main propulsion diesel engine, connecting it to the main shaft and driving a shaft-driven generator to generate electricity. This converts previously wasted mechanical energy into electrical energy, supplying the ship's AC switchboard, thereby reducing the operating time of auxiliary generators. Conversely, the switchboard can also output power to the shaft-driven generator, reducing fuel consumption and operating costs. However, existing marine shaft-driven generator grid connection systems face a series of technical challenges and reliability issues during startup and grid connection. Upon initial power-up, the large-capacity support capacitor at the DC bus downstream momentarily exhibits low impedance characteristics, resulting in a huge surge current from the grid side. This current not only causes electrical stress on the front-end rectifier devices, shortening their lifespan, but may also cause a momentary voltage drop in the grid, interfering with the normal operation of other sensitive equipment on the same grid. Secondly, during the grid connection process between the shaft-driven generator and the ship's electrical grid, precise control of the voltage amplitude, frequency, and phase at the moment of grid connection is essential for achieving a smooth connection. If forced closing occurs when there is a significant voltage difference between the two sides, a huge inrush current will be generated in a very short time due to the presence of filter capacitors and other internal capacitors in the equipment, seriously threatening the stability of the contactor contacts and the entire power system. Furthermore, the existing hardware topology lacks flexibility and is difficult to adapt to the grid voltage levels and shaft generator parameters of different ship models. Therefore, there is an urgent need in this field for a marine shaft generator grid connection device that can effectively suppress inrush currents, achieve smooth and accurate grid connection, and possess good adaptability and reliability. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a marine shaft-driven generator grid connection device to solve the above-mentioned problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This utility model provides a marine shaft-driven generator grid-connected device, comprising an AC contactor, a first transformer, a rectifier, an inverter, and a shaft-driven generator connected in sequence. The first end of the AC contactor is connected to an AC distribution board. The marine shaft-driven generator grid-connected device also includes a pre-charge module, which comprises a second transformer, an uncontrolled rectifier unit, and a soft starter unit connected in sequence. The pre-charge module is connected to the AC power grid through the primary side of the second transformer. The output end of the soft starter unit is connected in parallel to the DC bus between the inverter and the rectifier.

[0006] Furthermore, the soft starter unit is located at the output terminal of the uncontrolled rectifier unit. The soft starter unit includes a first switch, a current-limiting resistor, and a bypass switch. The current-limiting resistor and the first switch are connected in series to form a soft starter branch. The soft starter branch and the bypass switch are connected in parallel and then connected to the same polarity line of the DC bus.

[0007] Furthermore, an LCL filter is provided between the rectifier and the first transformer. The LCL filter includes at least one three-phase filter capacitor, a grid-side three-phase inductor connected in series at one end of the rectifier, and a machine-side three-phase inductor connected in series at the secondary side of the first transformer.

[0008] Furthermore, the three-phase filter capacitor is connected in parallel at the three-phase connection point between the grid-side three-phase inductor and the machine-side three-phase inductor, and the three-phase filter capacitor includes three first capacitors connected in pairs.

[0009] Furthermore, it also includes an inverter controller connected to the inverter and a rectifier controller connected to the rectifier, the rectifier controller being used to detect the first terminal voltage of the AC contactor and the primary voltage of the first transformer.

[0010] Furthermore, the primary side of the first transformer is connected to the second end of the AC contactor.

[0011] Furthermore, it also includes a reactor connected in series between the shaft-driven generator and the inverter.

[0012] Furthermore, both the first transformer and the second transformer are isolated high-voltage power frequency transformers.

[0013] The advantages of this utility model compared with the prior art are:

[0014] A marine shaft-driven generator grid-connected device includes an AC contactor, a first transformer, a rectifier, an inverter, and a shaft-driven generator connected in sequence. The first terminal of the AC contactor is connected to an AC distribution board. The marine shaft-driven generator grid-connected device also includes a pre-charge module, which includes a second transformer, an uncontrolled rectifier unit, and a soft starter unit connected in sequence. The pre-charge module is connected to the AC power grid through the primary side of the second transformer. The output terminal of the soft starter unit is connected in parallel to the DC bus between the inverter and the rectifier.

[0015] This device enables flexible energization of the DC bus, effectively mitigating the risk of surges. By integrating a dedicated soft-start unit and employing a timing control strategy combining current-limiting resistors and bypass switches, the surge current is strictly limited to a safe range when charging the capacitors on the DC bus. This fundamentally avoids instantaneous impacts on the power grid, prevents voltage drops in the distribution circuit caused by current overload, ensures the lifespan of rectifier devices, and significantly improves the reliability and safety of the entire grid connection process.

[0016] It exhibits good adaptability to various scenarios. This device incorporates a second transformer and a first transformer in the pre-charging module and grid-connected circuit, respectively. By flexibly configuring their primary and secondary side transformation ratios, the same device can adapt to the voltage levels of different ship power grids and the output voltage requirements of shaft-driven generators. This design solves the problem of poor versatility caused by fixed parameters in existing solutions, broadens the device's applicability, reduces the need for customized design and equipment replacement due to ship type differences, and lowers overall costs.

[0017] This ensures precise and smooth grid connection, improving system stability. By pre-magnetizing the first transformer with a rectifier and monitoring the secondary voltage of the first transformer and the voltage at the first terminal of the AC contactor in real time, this device achieves instantaneous closing at the synchronization of voltage amplitude and phase. It avoids the huge inrush current generated by grid connection with differential voltage, protecting the AC contactor and other sensitive electrical equipment. This ensures seamless and stable connection of the shaft-driven generator to the ship's power distribution network, thereby improving the power supply quality and operational stability of the entire ship's electrical system.

[0018] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model, it can be implemented according to the contents of the specification. In order to make the above and other objectives, features and advantages of this utility model more obvious and easy to understand, the following are preferred embodiments, which are described in detail below. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A circuit topology diagram of a marine shaft-driven generator grid-connected device provided for a specific embodiment of this utility model;

[0021] Figure 2 A circuit topology diagram of a precharge module provided for a specific embodiment of this utility model;

[0022] Figure 3 This is a circuit topology diagram of a phase-locked grid connection section provided for a specific embodiment of this utility model.

[0023] Figure Labels

[0024] 101. Soft starter unit; 102. Uncontrolled rectifier unit; 103. Inverter controller; 104. Rectifier controller; 105. Inverter; 106. Rectifier; 107. AC distribution board; T1. First transformer;

[0025] T2, Second Transformer; K1, First Switch; K2, Bypass Switch; K3, AC Contactor; C1, Three-phase Filter Capacitor; C2, First Capacitor; L1, Grid-side Three-phase Inductor; L2, Machine-side Three-phase Inductor; L3, Reactor; G1, Shaft-driven Generator; G2, Main Generator; G3, Auxiliary Generator; R1, Current-limiting Resistor. Detailed Implementation

[0026] The technical solution of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0027] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0029] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0030] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0031] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0032] like Figure 1-3 As shown, this utility model embodiment provides a marine shaft-driven generator grid-connected device, including an AC contactor K3, a first transformer T1, a rectifier 106, an inverter 105, and a shaft-driven generator G1 connected in sequence. The first end of the AC contactor K3 is connected to an AC distribution board 107. The marine shaft-driven generator grid-connected device also includes a pre-charge module, which includes a second transformer T2, an uncontrolled rectifier unit 102, and a soft starter unit 101 connected in sequence. The pre-charge module is connected to the AC power grid through the primary side of the second transformer T2. The output end of the soft starter unit 101 is connected in parallel to the DC bus between the inverter 105 and the rectifier 106. The marine shaft-driven generator grid-connected device provided by this utility model utilizes the soft starter unit 101 to achieve flexible energization of the DC bus, and uses the transformer to adjust the voltage difference across the AC contactor K3 to ensure smooth grid-connected operation. This device also has good scene adaptability.

[0033] Specifically, the secondary side of the second transformer T2 is connected to the input terminal of the uncontrolled rectifier unit 102.

[0034] It should be noted that the pre-charge module, as a power supply and pre-processing front end, safely and reliably obtains electrical energy from the AC power grid and provides power to subsequent devices such as the rectifier 106 and inverter 105, thus providing conditions for the normal start-up and operation of subsequent power equipment; the soft start unit 101 is used to suppress the surge current generated when the DC bus is initially powered on. In one operating condition of a ship, the main generator G2 drives the propeller to rotate and is connected to the shaft generator G1 through the main shaft, which can transfer excess power to the shaft generator G1 to drive its power generation.

[0035] like Figure 2 As shown, in one embodiment, the soft starter unit 101 is located at the output terminal of the uncontrolled rectifier unit 102. The soft starter unit 101 includes a first switch K1, a current limiting resistor R1, and a bypass switch K2. The current limiting resistor R1 and the first switch K1 are connected in series to form a soft starter branch. The soft starter branch and the bypass switch K2 are connected in parallel and are connected to the same polarity line of the DC bus to form control of a bus potential point.

[0036] Specifically, when the pre-charge module starts working, the soft-start unit 101 first closes the first switch K1, ensuring that the rectified current must pass through the current-limiting resistor R1 before charging the bus capacitor. The current-limiting resistor R1 effectively suppresses current peaks and fluctuations, achieving flexible power-on of the DC bus. When the inverter controller 103 or rectifier controller 104 detects that the DC bus voltage has reached its rated value, it opens the first switch K1, closes the bypass switch K2, and opens the first switch K1 again, short-circuiting the current-limiting resistor R1. The marine shaft-driven generator grid-connected device then enters a low-loss, full-power operating state. It should be noted that the bus capacitor is located inside the inverter 105 or rectifier 106. The first switch K1, bypass switch K2, and current-limiting resistor R1 are connected to the positive line of the DC bus to control its potential. When the pre-charge module is working, its power flow is from the pre-charge module through the converter and transformer to the AC distribution board 107.

[0037] like Figure 3 As shown, in one embodiment, an LCL filter is further provided between the rectifier 106 and the first transformer T1. The LCL filter includes a three-phase filter capacitor C1, a grid-side three-phase inductor L1 connected in series at one end of the rectifier 106, and a machine-side three-phase inductor L2 connected in series at the secondary side of the first transformer T1. The three-phase filter capacitor C1 is connected in parallel at the three-phase connection point between the grid-side three-phase inductor L1 and the machine-side three-phase inductor L2.

[0038] Specifically, the LCL filter is a third-order filter that has superior high-frequency attenuation characteristics compared to a single-inductor L-type filter. The rectifier 106 uses pulse width modulation (PWM) technology, which generates a large number of high-frequency harmonics during its switching process. The LCL filter can filter out these high-frequency switching harmonics, reducing current THD (Total Harmonic Distortion). Its bidirectional isolation and damping effects improve system stability and grid-connected power quality.

[0039] It should be noted that the three-phase filter capacitor C1 consists of three first capacitors C2 connected in pairs to form a triangular topology; the number of three-phase filter capacitors C1 can be one or more.

[0040] In one embodiment, the marine shaft generator grid-connected device further includes an inverter controller 103 connected to the inverter 105 and a rectifier controller 104 connected to the rectifier 106. The rectifier controller 104 is used to detect the voltage at the first terminal of the AC contactor K3 and the primary voltage of the first transformer T1.

[0041] Specifically, the primary and secondary turns ratio of the first transformer T1 is determined based on the voltage requirements of the AC distribution board 107 and the main bus. When the DC bus voltage reaches its rated value, the rectifier 106 continues to supply power and magnetize the first transformer T1. As the secondary voltage increases, the primary voltage of the first transformer T1 also increases. When the converter controller detects that the primary voltage of the first transformer T1 is equal to the voltage at the first terminal of the AC contactor K3, it closes the AC contactor K3 to complete grid connection, thus avoiding short-term current surges in the circuit due to the voltage difference between the two terminals after the AC contactor K3 is closed.

[0042] It should be noted that when the AC contactor K3 is closed and the bypass switch K2 is opened, there are two operating conditions: the first condition is that the shaft-driven generator G1 supplies power to the AC distribution board 107; the second condition is that the AC distribution board 107 supplies power to the shaft-driven generator G1 and outputs power, and the motor (not shown in the figure) inside the shaft-driven generator G1 converts electrical energy into mechanical energy to power the propeller. The shaft-driven generator can convert mechanical energy into electrical energy in the first operating condition and electrical energy into mechanical energy in the second operating condition.

[0043] The AC distribution board 107 is also connected to the auxiliary generator G3 and the load. The AC distribution board 107 and the auxiliary generator G3 can switch power supply to each other. The AC distribution board 107 can also supply power to the load.

[0044] In one embodiment, the marine shaft generator grid-connected device further includes a reactor L3 connected in series between the shaft generator G1 and the inverter 105. Specifically, the reactor L3 is used to filter high-frequency ripple and smooth the waveform of the current output by the shaft generator G1, and the inverter 105 is used for the conversion of DC and AC power.

[0045] In one embodiment, both the first transformer T1 and the second transformer T2 are isolated high-voltage power frequency transformers.

[0046] A marine shaft-driven generator grid-connected device includes a shaft-driven generator G1, an inverter 105, a rectifier 106, a first transformer T1, and an AC contactor K3 connected in sequence. The first terminal of the AC contactor K3 is connected to an AC distribution board. The marine shaft-driven generator grid-connected device also includes a pre-charge module, which includes a second transformer T2, an uncontrolled rectifier unit 102, and a soft starter unit 101 connected in sequence. The pre-charge module is connected to the AC power grid through the primary side of the second transformer T2. The output terminal of the soft starter unit 101 is connected in parallel to the DC bus between the inverter 105 and the rectifier 106.

[0047] This device enables flexible energization of the DC bus, effectively mitigating the risk of surges. By integrating a dedicated soft-start unit 101 and employing a timing control strategy involving a current-limiting resistor R1 and a bypass switch K2, the device strictly limits the surge current within a safe range when charging the capacitors on the DC bus. This fundamentally avoids instantaneous impacts on the power grid, prevents voltage drops in the distribution circuit caused by current overload, ensures the lifespan of the front-end rectifier devices, and significantly improves the reliability and safety of the entire grid connection process.

[0048] It exhibits good adaptability to various scenarios. This device incorporates a second transformer T2 and a first transformer T1 in the pre-charging module and grid-connected circuit, respectively. By flexibly configuring their primary and secondary side transformation ratios, the same device can adapt to the voltage levels of different ship power grids and the output voltage requirements of the shaft-driven generator G1. This design solves the problem of poor versatility caused by fixed parameters in existing solutions, broadens the device's applicability, reduces the need for customized design and equipment replacement due to ship type differences, and lowers overall costs.

[0049] This ensures precise and smooth grid connection, improving system stability. By pre-magnetizing the first transformer T1 through rectifier 106 and monitoring the secondary voltage of the first transformer T1 and the first terminal voltage of the AC contactor K3 in real time, this device achieves instantaneous closing at the synchronization of voltage amplitude and phase. It avoids the huge inrush current generated by grid connection with differential voltage, protects the AC contactor K3 and other sensitive electrical equipment, and ensures that the shaft-driven generator G1 can be seamlessly and smoothly connected to the ship's switchboard, thereby improving the power supply quality and operational stability of the entire ship's electrical system.

[0050] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A marine shaft-driven generator grid-connected device, characterized in that, It includes an AC contactor, a first transformer, a rectifier, an inverter, and a shaft-driven generator connected in sequence, with the first end of the AC contactor connected to an AC distribution board; The marine shaft generator grid-connected device also includes a pre-charge module, which includes a second transformer, an uncontrolled rectifier unit, and a soft starter unit connected in sequence. The pre-charge module is connected to the AC power grid through the primary side of the second transformer. The output terminal of the soft starter unit is connected in parallel to the DC bus between the inverter and the rectifier.

2. The marine shaft-driven generator grid-connected device according to claim 1, characterized in that, The soft starter unit is located at the output terminal of the uncontrolled rectifier unit. The soft starter unit includes a first switch, a current-limiting resistor, and a bypass switch. The current-limiting resistor and the first switch are connected in series to form a soft starter branch. The soft starter branch and the bypass switch are connected in parallel and then connected to the same polarity line of the DC bus.

3. The marine shaft-driven generator grid-connected device according to claim 1, characterized in that, An LCL filter is also provided between the rectifier and the first transformer. The LCL filter includes at least one three-phase filter capacitor, a grid-side three-phase inductor connected in series at one end of the rectifier, and a machine-side three-phase inductor connected in series at the secondary side of the first transformer.

4. The marine shaft-driven generator grid-connected device according to claim 3, characterized in that, The three-phase filter capacitor is connected in parallel at the three-phase connection point between the grid-side three-phase inductor and the machine-side three-phase inductor. The three-phase filter capacitor includes three first capacitors connected in pairs.

5. A marine shaft-driven generator grid-connected device according to claim 1, characterized in that, It also includes an inverter controller connected to the inverter and a rectifier controller connected to the rectifier, the rectifier controller being used to detect the first terminal voltage of the AC contactor and the primary voltage of the first transformer.

6. A marine shaft-driven generator grid-connected device according to claim 1, characterized in that, The primary side of the first transformer is connected to the second end of the AC contactor.

7. A marine shaft-driven generator grid-connected device according to claim 1, characterized in that, It also includes a reactor connected in series between the shaft-driven generator and the inverter.

8. A marine shaft-driven generator grid-connected device according to claim 1, characterized in that, Both the first transformer and the second transformer are isolated high-voltage power frequency transformers.

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