Ship shaft power generation system and method

Abstract

The present invention relates to the technical field of ship shaft power generation, and more specifically to a ship shaft power generation system and method, comprising a power module, a shaft motor, a frequency conversion control cabinet, an isolation transformer, a ship power plant, an AC switchboard, a daily load, a DC train, a chopper, and a lithium battery. The power module includes a main engine controlled by a remote control handle, with a rotating shaft fixed to the output terminal of the main engine. The operation of the main engine rotates the rotating shaft and propeller to propel the ship. The shaft motor is mounted on the rotating shaft and is used to switch between the generator and motor under different ship navigation conditions. The present invention balances the charging and discharging of the lithium battery to improve its lifespan, while simultaneously enabling stable operation of the shaft power generation system under various conditions and increasing the economic efficiency of ship operation.

Description

Technical Field

[0001] The present invention relates to the technical field of ship shaft power generation, and specifically to a ship shaft power generation system and method.

Background Art

[0002] Conventional ship power systems generally require two different diesel engines, namely a main propulsion diesel engine and a diesel engine for the power generation unit. Among them, the main propulsion diesel engine is also called the "main engine" (hereinafter collectively referred to as the "main engine"). The main engine is connected to the propeller and provides a propulsion effect on the ship. Due to different operating conditions, the rotational speed of the propeller is constantly changing, so the main engine generally operates in a variable speed situation. The rotational speed of the main engine responds based on the set value of the propulsion handle in the steering room. Among them, the power generation unit connects a diesel engine to a generator to form a "power generation unit" and supplies power to all loads of the ship power plant. Generally, considering reasons such as reliability, the ship power plant is composed of three or more power generation units. Since the output voltage and frequency of the power generation units are approximately fixed, the diesel engines for the power generation units usually operate at a constant rotational speed as shown in Figure 1.

[0003] In actual work, generally when selecting the capacity of the main engine, in order to ensure the performance of the ship, not only is the capacity of the main engine selected higher than the propeller characteristic curve, but a certain margin is also left, showing the characteristic of "a large engine with a small propeller". As shown in Figure 2, by subtracting the propeller mechanical characteristic curve (indicating the power required to ensure propeller rotation at different rotational speeds, or the mechanical power that the propeller can absorb at different rotational speeds) from the main engine capacity curve (indicating the energy of the main engine output power at different rotational speeds), the main engine margin capacity curve can be obtained.

[0004] Currently, in order to reduce the use of generators, the ship is choosing to provide a power plant by utilizing the surplus capacity of the main engine. Specifically, a generator is installed on the main shaft between the main engine and the propeller. This generator is called a "shaft generator," and as shown in Figure 3, the output frequency of the shaft generator is proportional to the rotational speed of the shaft generator. Since the rotational speed of the shaft generator perfectly matches that of the main shaft and main engine, it can be considered that the output frequency of the shaft generator is proportional to the rotational speed of the main engine. In this case, in order to obtain a stable frequency, a frequency conversion control cabinet is usually added. The AC power output from the shaft generator is first converted from an AC voltage with a variable voltage frequency to a fixed DC power via a rectifier (AC / DC), and then the fixed DC voltage is converted to an AC voltage with a fixed voltage frequency via an inverter (DC / AC), supplying power to the ship's power plant. As shown in Figure 3, this frequency conversion control cabinet is also commonly called a "shaft frequency converter."

[0005] When a ship is sailing, the power generation unit is normally shut down. The output voltage of a high-power shaft generator is typically 640V, and ship power plants generally accept 400V. Therefore, it is usually necessary to equip the ship with an isolation transformer to convert 640V to 400V. The shaft generator, shaft inverter, and isolation transformer are considered as a single unit, and this entire unit is called the "shaft power generation system." As shown in Figure 3, the use of the shaft power generation system reduces the use of the power generation unit, saves oil consumption, and extends the lifespan and maintenance cycle of the power generation unit.

[0006] However, ship shaft power generation systems are limited to the following two situations during use: First, it is limited by the power output between the engine and the paddle. As shown in Figure 4, generally the mechanical characteristic curve of the propeller is as curve A in Figure 4, and at this time the main engine capacity has enough margin to supply power to the shaft generator system, but the mechanical characteristic curve of the propeller does not remain constant, but changes according to the resistance characteristics of the hull, and specifically, is usually affected by the following conditions, The influence of sea conditions (wind, waves, currents) significantly affects the resistance characteristics of a ship. Generally, adverse sea conditions increase the propeller's mechanical characteristics curve, resulting in what is known as "the propeller becoming heavier." The effect of cargo load: The heavier the load, the deeper the draft, increasing the ship's resistance, and consequently, the heavier the propeller becomes. The effects of hull deposits: As a ship gradually operates, barnacle-like deposits tend to accumulate on the underwater portion of the hull. These deposits also increase the ship's resistance, making the propeller heavier. Therefore, when a ship encounters adverse sea conditions with heavy loads, the propeller's mechanical characteristic curve shifts upward, moving from curve A to curves B, C, and D in Figure 4. When the propeller operates on curve B, the margin capacity between the engine and paddle decreases, and as the rotational speed decreases, the main engine's margin capacity decreases sharply. At the maximum rotational speed, the main engine's capacity curve and the propeller's mechanical characteristic curve intersect at b, at which point the main engine has no margin to provide power generation for the shaft system. When the propeller operates on curve C or D, the main engine's capacity curve and the propeller's mechanical characteristic curve intersect at c or d, respectively. At this point, the main engine cannot operate the propeller at its maximum rotational speed and must operate at a reduced speed. Considering that the ship's cruising speed is almost proportional to the propeller's rotational speed, not only is the shaft power generation system unusable, but the ship's speed also decreases significantly, drastically reducing the ship's economic efficiency. This is what is known as a "small engine, big oars" situation. Secondly, it is limited by unstable sea conditions. When a ship is operating in unstable sea conditions, the propeller's mechanical characteristic curve fluctuates. In particular, when a ship is unloaded, the ship's draft is shallow, and under unstable sea conditions, the ship's propeller may occasionally be partially above the sea surface (also called "propeller underwater exposure"), meaning that it may occasionally not be fully submerged. When the propeller is exposed underwater, the propeller's mechanical characteristic curve becomes lighter, and when the propeller is submerged, the propeller's mechanical characteristic curve becomes heavier. The propeller characteristic curve repeatedly fluctuates between heavy and light. Refer to Figure 5 for a schematic diagram of the power. When the propeller's mechanical characteristic curve is unstable, ultimately the load on the main engine changes frequently. At this time, even if the control handle of the main engine is not moved, when the load is lighter, the engine speed increases, and the engine's governor decreases the throttle. When the load increases, the engine speed decreases, and the engine's governor increases the throttle. While it is not practical to determine a stable propeller load, under conditions of stable sea conditions, the main engine's governor can control the engine speed within a stable range by adjusting the throttle. A typical curve for main engine speed operation is shown in Figure 6, where the engine speed fluctuates between 83 rpm and 86 rpm, with a fluctuation range of only 3 rpm. This indicates that the engine speed is being controlled stably and efficiently.

[0007] In contrast, after unstable sea conditions occurred, the load on the main engine fluctuated drastically. Because the throttle adjustment speed of the main engine was not well able to adapt to the rapid changes in load, repeated adjustments failed to bring the rotational speed to equilibrium. As shown in Figure 7, a typical main engine rotational speed waveform under unstable sea conditions shows that within approximately 1 minute, the rotational speed fluctuated from 76 rpm to 94 rpm, with about 10 peaks. Such drastic fluctuations not only affected the stability of the shaft generator system, but the insufficient combustion caused by repeated throttle adjustments increased emissions and fuel consumption.

[0008] Therefore, it is necessary to design a ship's shaft power generation system and its power generation method that can overcome the above constraints, enable stable use of the shaft power generation system, balance the changes in the main engine throttle due to the propeller load, and improve the economic efficiency of ship operation. [Overview of the Initiative] [Means for solving the problem]

[0009] To solve the above technical problems, the present invention provides a ship shaft power generation system and a power generation method thereof to solve the problem that conventional shaft power generation systems on the market proposed in the above background art cannot be used normally and stably when limited by the output capacity between the engine and paddle and by unstable sea conditions.

[0010] To achieve the above objectives, the present invention is realized by the following technical solution: A ship's shaft power generation system comprising a power module, a shaft motor, a frequency conversion control cabinet, an isolation transformer, a ship's power plant, an AC switchboard, a daily load, a DC train, a chopper, and a lithium battery, wherein the power module includes a main engine controlled by a remote control handle, a rotating shaft fixed to the output end of the main engine, and a propeller (3) fixed to the end of the rotating shaft, the operation of the main engine controlled by a remote control handle in the ship's cabin, and the operation of the main engine rotates the rotating shaft and propeller to propel the ship's navigation.

[0011] The shaft motor is mounted on the rotating shaft and is used to switch between the generator and motor under different navigation conditions of the ship. This allows excess mechanical energy generated when the rotating shaft rotates to be converted into electrical energy and stored, while when the rotation of the rotating shaft is slow, the previously stored electrical energy can be used to power the shaft motor and increase the rotational speed of the rotating shaft.

[0012] The system includes a frequency converter control cabinet containing a PLC controller and a frequency converter. The PLC controller is signal-connected to a remote control handle to obtain a set rotational speed for the main engine. The frequency converter is connected to the shaft motor via a cable to provide an AC voltage with a fixed voltage frequency. An isolation transformer is connected to the frequency converter via a cable, converting the AC voltage output from the frequency converter to supply power to the ship's daily load and using surplus power to provide a precharge voltage to the DC train.

[0013] The DC train is connected to the DC stage of the frequency converter via a cable, the chopper is connected to the DC train via a cable, the lithium battery with an internal battery management system is connected to the frequency converter via a cable, the PLC controller and lithium battery are connected via bus CAN, and are used to obtain the actual power of the lithium battery while maintaining the lithium battery's power at 90% over the long term, facilitating a later comparison between the lithium battery's set power and actual power.

[0014] An optical encoder is mounted on the rotating shaft to detect the actual rotational speed of the rotating shaft and the main engine and transmit the signal to the PLC controller. The PLC controller and the optical encoder are connected via a cable to receive the signal from the optical encoder and to obtain the actual rotational speed of the main engine, facilitating the comparison between the set rotational speed and the actual rotational speed of the main engine.

[0015] The PLC controller further includes a first proportional-integral controller and a second proportional-integral controller. The first proportional-integral controller takes the difference between the main engine's set rotational speed and its actual rotational speed as input and sets the output value obtained as the chopper's first current setting value. When the propeller becomes lighter, it indicates that the main engine's set rotational speed is lower than the actual rotational speed. At this time, the PLC controller controls the lithium battery to charge, which is equivalent to increasing a virtual main engine load and lowering and stabilizing the main engine's rotational speed. When the propeller becomes heavier, it indicates that the main engine's set rotational speed is higher than the actual rotational speed. At this time, the PLC controller controls the lithium battery to discharge, which is equivalent to increasing a virtual main engine power and raising and stabilizing the main engine's rotational speed. Therefore, by controlling the charging and discharging of the lithium battery with the PLC controller, additional power is provided to the propeller when the main engine's capacity is insufficient, and additional load is provided to the main engine when the main engine's capacity is excessive, ultimately suppressing fluctuations in the main engine and throttle.

[0016] The second proportional-integral controller takes the difference between the set energy level and the actual energy level of the lithium battery as input and uses the resulting output value as the second current setting value for the chopper. In other words, if the set energy level of the lithium battery is less than the actual energy level, it is used to control whether to increase the discharge current or decrease the charging current of the chopper. If the set energy level of the lithium battery is greater than the actual energy level, the PLC controller can increase the charging current or decrease the discharge current of the battery chopper. This fine-tunes the chopper current, balances the charging and discharging of the lithium battery, ensures stable operation of the shaft power generation system, and improves the economics of ship operation.

[0017] The sum of the chopper's first current setting and the chopper's second current setting is the chopper's final current setting.

[0018] Preferably, a signal connection is established between the PLC controller and the remote control handle via a cable, and the PLC controller receives a 4mA to 20mA signal transmitted from the remote control handle, thereby enabling signal transmission between the PLC controller and the remote control handle, and furthermore, the set rotational speed of the main engine can be obtained normally.

[0019] Preferably, the shaft motor has a power of 600KW, a rotational speed of 64rpm to 89rpm, and an isolation transformer capacity of 750KVA. After converting the 600V from the shaft motor to 640V using a frequency converter, the 640V output from the frequency converter is converted to 400V using an isolation transformer, so that the current and voltage generated by the shaft power generation system can be used normally for the ship's daily load.

[0020] Preferably, the frequency converter includes a rectifier and an inverter, with the rectifier and the shaft motor connected via a cable, the inverter and the rectifier connected via a cable, and the isolation transformer and the inverter connected via a cable, thereby enabling the conversion of current by the shaft motor and ultimately obtaining a fixed alternating current.

[0021] Preferably, a Dvdt filter is further provided between the shaft motor and the rectifier to limit the rate of rise of the output voltage of the frequency converter and protect the winding insulator of the generator. A PWM filter is provided between the inverter and the isolation transformer, mainly consisting of a reactor, capacitor, and resistor, and is used for harmonic suppression in the daily bypass circuit. An inductor is further provided between the chopper and the lithium battery, and is a passive device necessary to constitute the chopper circuit (Buck-Boost circuit). Power storage of the reactor is necessary for short-time switching of the switch, and it also controls the current ripple in the chopper bypass circuit.

[0022] Preferably, circuit breakers are provided between the shaft motor and the Dvdt filter, between the isolation transformer and the AC distribution panel, between the ship's power plant and the AC distribution panel, between the AC distribution panel and the load, and between the inductor and the lithium battery.

[0023] Preferably, by setting the control bandwidth of the rotational speed of the main engine by the plc controller to 1 Hz, low-speed control of the actual rotational speed of the main engine is achieved. By setting the control bandwidth of the power amount of the lithium battery by the plc controller to 0.01 Hz, low-speed control of the charging current and discharging current of the lithium battery is achieved.

[0024] An axial power generation method, First, while inserting one axial motor through the rotating shaft of the propeller connected to the main engine, an optical encoder is attached to the rotating shaft to detect the actual rotational speed of the main engine S1, Subsequently, a frequency conversion control cabinet including a plc controller and a frequency converter is installed. After the plc controller is signal-connected to the frequency converter via a cable, the axial motor and the frequency converter are connected via a cable, and it is used to output an AC voltage with a fixed voltage frequency. Here, the frequency converter includes a rectifier and an inverter. The axial motor and the rectifier are connected via a cable, and the inverter and the rectifier are connected via a cable S2, To convert the AC voltage output from the frequency converter to be suitable for the daily load use of the ship, an insulating transformer and an inverter are connected via a cable S3, Subsequently, the insulating transformer and the ship power plant are connected in parallel to the AC switchboard via a cable to supply power to the daily load of the ship S4, A DC series is connected via a cable to the DC stage between the rectifier and the inverter. A part of the ship power plant is used to supply power to the daily load of the ship. When there is surplus power, the current of the ship power plant sequentially communicates with the DC series through the insulating transformer and the inverter, and provides a pre-charge voltage to the DC series. After connecting a chopper to the DC series via a cable, the chopper is connected to the lithium battery via a cable. A battery management system is implemented on the circuit board inside the lithium battery S5, Finally, the PLC controller that controls the operation of the inverter is signal-connected to the remote control handle that controls the operation of the main engine via a dual cable, receives a 4 mA - 20 mA signal from the remote control handle, and further obtains the set rotational speed of the main engine. Next, the PLC controller is signal-connected to the optical encoder via a cable, receives the signal of the optical encoder, and further obtains the actual rotational speed of the main engine. Also, the PLC controller and the lithium battery are connected via a bus CAN. The charging power of the lithium battery (14) is controlled and set to 90%, and at the same time, a signal from the battery management system (BMS) inside the lithium battery (14) is received to obtain the actual power of the lithium battery. Finally, a first proportional integral controller and a second proportional integral controller are installed inside the PLC controller. The difference between the set rotational speed and the actual rotational speed of the main engine is input into the first proportional integral controller, and the obtained output value is used as the first current set value of the chopper. At this time, when the propeller becomes lighter, it indicates that the set rotational speed of the main engine is smaller than the actual rotational speed. At this time, the PLC controller controls to charge the lithium battery. When the propeller becomes heavier, it indicates that the set rotational speed of the main engine is larger than the actual rotational speed. At this time, while the PLC controller controls to discharge the lithium battery, the control bandwidth of the rotational speed of the main engine by the PLC controller is set to 1 Hz to achieve fast control. The difference between the set power and the actual power of the lithium battery is input into the second proportional integral controller, and the obtained output value is used as the second current set value of the chopper. At this time, when the set power of the lithium battery is lower than the actual power, the PLC controller controls to increase the discharge current of the chopper or decrease the charging current. When the set power of the lithium battery is higher than the actual power, the PLC controller controls to increase the charging current of the chopper or decrease the discharge current. While the control bandwidth of the charge and discharge of the lithium battery by the PLC controller is set to 0.01 Hz to achieve low-speed control. S6 including that the sum of the first current set value and the second current set value is the final current set value of the chopper.

Advantages of the Invention

[0025] This invention determines the difference between the set rotational speed and the actual rotational speed of the main engine, thereby confirming whether the propeller is lighter or heavier. Furthermore, it precisely controls the charging and discharging of the lithium battery, thereby ensuring that additional power is supplied to the propeller when the main engine capacity is insufficient, and additional load is supplied to the main engine when the main engine capacity is excessive, ultimately suppressing fluctuations in the main engine and throttle. Simultaneously, by controlling the lithium battery's power output to 90% and comparing it to the actual power output of the lithium battery, the chopper current is finely adjusted to balance the charging and discharging of the lithium battery, thereby increasing the battery's lifespan and ensuring stable operation of the shaft power generation system under various conditions, thus improving the economic efficiency of ship operations. [Brief explanation of the drawing]

[0026] To more clearly illustrate embodiments of the present invention or technical aspects of the prior art, the drawings that may be used in the description of embodiments or prior art are briefly described below. Clearly, the drawings in the following description are some embodiments of the present invention, and a general person of the art can obtain other drawings based on these without expending any creative effort. [Figure 1] This is a schematic diagram of an existing ship power system according to the present invention. [Figure 2] This graph reflects the excess capacity of the main engine in existing ship propulsion systems. [Figure 3] This is a schematic diagram of a shaft power generation system in an existing ship's propulsion system. [Figure 4] This is a schematic diagram of the propeller mechanical characteristics curve when an existing ship's shaft generator system is limited by the output capacity between the engine and the paddle. [Figure 5] This is a schematic diagram illustrating the power output of an existing shipboard shaft power generation system when subjected to unstable sea conditions. [Figure 6] This is a schematic diagram of a typical main engine rotation speed operating curve in an existing ship shaft power generation system. [Figure 7]This is a schematic diagram of a typical main engine rotational speed waveform in an existing ship's shaft power generation system when subjected to unstable sea conditions. [Figure 8] This is a schematic diagram of the shaft power generation system of the present invention. [Figure 9] This is a schematic diagram illustrating the calculation principle for the final current setting value of the chopper in the present invention. [Figure 10] This is a schematic diagram of the control flow of the present invention. [Figure 11] This is a schematic circuit diagram of the lithium battery pack, chopper, and DC train according to the present invention. [Figure 12] This is a schematic circuit diagram of the shaft motor, rectifier, and DC train according to the present invention. [Figure 13] This is a schematic circuit diagram of the DC train, inverter, isolation transformer, AC distribution board, and daily load according to the present invention. [Modes for carrying out the invention]

[0027] Hereinafter, the technical aspects of embodiments of the present invention will be clearly and completely described in relation to embodiments of the present invention. Clearly, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative work based on the embodiments of the present invention are within the scope of the protection of the present invention.

[0028] The present invention provides the following embodiments, Referring to Figures 1-13, a ship's shaft power generation system includes a power module, a shaft motor, a frequency conversion control cabinet, an isolation transformer 9, an AC distribution board 10, a ship's power plant 11, and a daily load 12. As can be seen by referring to Figures 1, 3, 5, 8, and 10, the power module includes a main engine 1, a rotary shaft 2, and a propeller 3. The operation of the main engine 1 is controlled by a crew member in the cabin using a remote control handle, and the remote control handle is connected to the main engine 1 via a cable. When the main engine 1 is operating, the rotary shaft 2 and propeller 3 rotate, generating thrust and propelling the ship forward.

[0029] As can be seen by referring to Figures 3, 5, 8, and 10, a shaft motor 5 is attached to the rotating shaft 2, a circuit breaker is connected to the shaft motor 5 via a cable, the circuit breaker is connected to a Dvdt filter via a cable, the Dvdt filter and rectifier 6 are connected via a cable, the rectifier 6 is connected to an inverter 8 via a cable, the inverter 8 is connected to a PWM filter via a cable, the PWM filter is connected to an isolation transformer 9 via a cable, the isolation transformer 9 is connected in parallel to the ship's power plant 11 and the AC distribution board 10 via a cable, and supplies power to the ship's daily load 12. Here, a circuit breaker is provided between the isolation transformer 9 and the AC distribution board 10, a circuit breaker is also provided between the ship's power plant 11 and the AC distribution board 10, and a circuit breaker is also provided between the AC distribution board 10 and the daily load 12.

[0030] Here, the shaft motor 5 consists of two parts: a rotating part and a stationary part. The rotating part is called the "rotor," and the stationary part is called the "stator." The rotor of the shaft motor 5 is fixed to the rotating shaft 2, and the stator of the shaft motor 5 is fixed to the hull. The shaft motor 5 rotates the rotor through the rotation of the rotating shaft 2, thereby converting mechanical energy into electrical energy and outputting a current. This current flows through a circuit breaker and a Dvdt filter to a rectifier 6, where it is converted to direct current. The Dvdt filter limits the rate at which the output voltage of the frequency converter rises, protecting the winding insulator of the generator.

[0031] The DC current converted by the rectifier 6 reaches the inverter 8, where it is converted back to AC current. At this time, the AC current flows through the PWM filter to the isolation transformer 9, converting the AC voltage output from the frequency converter into an acceptable operating voltage for the ship's daily load 12. Here, the power of the shaft motor 5 is 600KW, and the rotational speed of the shaft motor 5 is 64rpm to 89rpm. The capacity of the isolation transformer 9 is 750KVA, which means that the output voltage of the shaft motor 5, 600V, is converted to 640V via the frequency converter, and further the voltage of 640V output from the frequency converter is converted to a usable 400V voltage for the ship's daily load 12 via the isolation transformer 9, so that the current and voltage generated by the shaft power generation system can be used normally for the ship's daily load 12. Here, the PWM filter mainly consists of a reactor, capacitor, and resistor, and is used for harmonic suppression in the daily bypass circuit.

[0032] The alternating current converted by the isolation transformer 9 is then combined into the AC distribution panel 10 via the circuit breaker and used for the daily load 12.

[0033] The ship's power plant 11 includes a first power generation unit and a second power generation unit. The current from both sets of power generation units is combined into the AC distribution panel 10 via a circuit breaker and similarly used for the daily load 12.

[0034] As can be seen by referring to Figure 10, both the rectifier 6 and the inverter 8 are installed in a frequency conversion control cabinet. A PLC controller is further installed in the frequency conversion control cabinet, and the PLC controller is connected to the rectifier 6 and the inverter 8 via cables, respectively, to control the operation of the rectifier 6 and the inverter 8.

[0035] The PLC controller is signal-connected via a cable to a remote control handle that controls the operation of the main engine 1. When the remote control handle is used, it controls the operation of the main engine 1 and transmits a 4mA to 20mA signal to the PLC controller to obtain the rotational speed of the main engine 1 at that moment. At this time, the rotational speed of the main engine 1 is set to the rotational speed, and an optical encoder 4 is further attached to the rotating shaft 2. The optical encoder 4 and the PLC controller are signal-connected via a cable. When the rotating shaft 2 and propeller 3 are rotated while the main engine 1 is operating, the optical encoder 4 detects the rotational speed of the rotating shaft 2 and transmits that rotational speed to the PLC controller, which is the rotational speed of the rotating shaft 2 at that moment, i.e., the actual rotational speed of the main engine 1.

[0036] As can be seen by referring to Figures 8 and 10, the DC stage between the rectifier 6 and the inverter 8 is connected to a DC train 7 via a cable, the DC train 7 is connected to a chopper 13 via a cable, an inductor is connected to the chopper 13 via a cable, a lithium battery 14 is connected to the inductor via a cable, a circuit breaker is installed in the cable between the inductor and the lithium battery 14, a battery management system (BMS) is installed on the circuit board inside the lithium battery 14, the lithium battery 14 is connected to a PLC controller via bus CAN, the battery management system (BMS) transmits the detected power amount of the lithium battery 14 to the PLC controller, and obtains the actual power amount of the lithium battery 14 at that time.

[0037] During operation, as shown in Figure 12, the current generated by the shaft motor 5 is converted to a rectifier 6, and the DC current merges into the DC train 7. Some of the DC current flows through the DC train 7 to the inverter 8, and continues to flow until it merges with the AC distribution panel 10, where it is used to supply power to the daily load 12. In addition, some of the DC current flows through the DC train 7 to the chopper 13, and then through the inductor and circuit breaker to the lithium battery 14, where it is used for charging and discharging the lithium battery 14.

[0038] As can be seen by referring to Figures 11 and 13, if the power used for the daily load 12 on the ship is less than the power of the ship's power plant 11, the ship's power plant 11 can use the surplus power to supply current to the isolation transformer 9 via the AC distribution panel 10, which then flows through the PWM filter to the inverter 8, and then to the DC train 7, supplying a precharge voltage to the DC train 7.

[0039] Simultaneously, inputting the algorithm into the PLC controller and referring to Figure 9, results in the following: Within the PLC controller, a first proportional-integral controller and a second proportional-integral controller are further provided. First, the PLC controller receives the difference between the set rotational speed of the main engine 1 and its actual rotational speed, which is then input to the first proportional-integral controller. The value output from the first proportional-integral controller is then set as the first current setting value for the chopper 13. When the propeller 3 becomes lighter, it indicates that the set rotational speed of the main engine 1 is lower than its actual rotational speed. At this time, the PLC controller controls the lithium battery 14 to charge, which is equivalent to increasing the virtual main engine load and lowering and stabilizing the rotational speed of the main engine 1. When the propeller 3 becomes heavier, it indicates that the set rotational speed of the main engine 1 is higher than its actual rotational speed. At this time, the PLC controller controls the lithium battery 14 to discharge, which is equivalent to increasing the virtual main engine power and raising and stabilizing the rotational speed of the main engine 1.

[0040] Therefore, by controlling the charging and discharging of the lithium battery 14 with a PLC controller, additional power is provided to the propeller 3 when the capacity of the main engine 1 is insufficient, and additional load is provided to the main engine 1 when the capacity of the main engine 1 is excessive, ultimately suppressing fluctuations in the main engine 1 and throttle.

[0041] As can be seen by referring to Figures 6 and 7, in unstable sea conditions, the rotational speed waveform of the main engine 1 fluctuates from 76 rpm to 94 rpm in about 1 minute, generating about 10 peaks. In this case, the frequency bandwidth of the rotational speed of the main engine 1 is about 0.16 Hz, so it is necessary to control the rotational speed of the main engine 1. The control bandwidth of the PLC controller is larger than the frequency bandwidth of the rotational speed of the main engine 1, so it is possible to control the rotational speed of the main engine 1. However, in unstable sea conditions, the rotational speed actually fluctuates and changes rapidly, so it is necessary to control the rotational speed of the main engine 1 at high speed. Therefore, in the present invention, it is preferable to set the control bandwidth of the PLC controller to 1 Hz so that the rotational speed of the main engine computer 1 can be rapidly controlled.

[0042] When simultaneously setting and controlling the charge / discharge power of the lithium battery 14 to 90%, the set power value of the lithium battery 14 is compared with the actual power of the lithium battery 14 transmitted to the plc controller by the battery management system (BMS). The difference between the two is input to the second proportional-integral controller, and the output value is set as the second current setting value of the chopper 13. If the set power value of the lithium battery 14 is less than the actual power, the plc controller controls the discharge current of the chopper 13 to increase or decrease the charge current. If the set power value of the lithium battery 14 is greater than the actual power, the plc controller controls the charging current of the battery chopper to increase or decrease the discharge current.

[0043] This allows the PLC controller to fine-tune the current of the chopper 13, balancing the charging and discharging of the lithium battery 14, thereby increasing the lifespan of the lithium battery 14, ensuring stable operation of the shaft power generation system, and improving the economic efficiency of ship operation.

[0044] Since the charging and discharging process of the lithium battery 14 is relatively slow compared to the change in rotational speed of the main engine 1, low-speed control can be performed on the charging and discharging process of the lithium battery 14. In this invention, the control bandwidth for controlling the charging and discharging of the lithium battery 14 by the PLC controller is set to 0.01 Hz, thereby achieving low-speed control.

[0045] The sum of the first current setting value and the second current setting value will be the final current setting value for chopper 13.

[0046] As can be seen by referring to Figures 1 to 13, this is a shaft power generation method, First, a shaft motor 5 is inserted through the rotating shaft 2 of the propeller 3 connected to the main engine 1, and at the same time, an optical encoder 4 is attached to the rotating shaft 2 to detect the actual rotational speed of the main engine 1 (S1). Next, a frequency conversion control cabinet containing a PLC controller and frequency converter is installed. The PLC controller is then signaled to the frequency converter via a cable, and then connected to the shaft motor 5 via a cable and used to output an AC voltage with a fixed voltage frequency. Here, the frequency converter includes a rectifier 6 and an inverter 8, the shaft motor 5 and the rectifier 6 are connected via a cable, the inverter 8 and the rectifier 6 are connected via a cable, a Dvdt filter is further provided between the shaft motor 5 and the rectifier 6, a PWM filter is provided between the inverter 8 and the isolation transformer 9, and an inductor is further provided between the chopper 13 and the lithium battery 14 in S2, S3 connects an isolation transformer 9 and an inverter 8 via a cable to convert the AC voltage output from the frequency converter and make it suitable for use with a ship's daily load 12. Next, the isolation transformer 9 and the ship's power plant 11 are connected in parallel to the AC distribution panel 10 via a cable, supplying power to the ship's daily load 12, S4. A DC train 7 is connected to the DC stage between the rectifier 6 and the inverter 8 via a cable, and a portion of the ship's power plant 11 is used to supply power to the ship's daily load 12. When there is surplus power, the current from the ship's power plant 11 is sequentially connected to the DC train 7 through the isolation transformer 9 and inverter 8, providing a precharge voltage to the DC train 7. After connecting the chopper 13 to the DC train 7 via a cable, the chopper 13 is connected to the lithium battery 14 via a cable, and the circuit board inside the lithium battery 14 has a battery management system (BMS) implemented on it (S5). Finally, the PLC controller that controls the operation of the inverter is signal-connected via a dual cable to a remote control handle that controls the operation of the main engine 1, receiving a signal of 4mA to 20mA from the remote control handle and obtaining the set rotational speed of the main engine 1. Next, the PLC controller is signal-connected via a cable to an optical encoder 4, receiving a signal from the optical encoder 4 and obtaining the actual rotational speed of the main engine 1. In addition, the PLC controller and the lithium battery 14 are connected via a bus CAN, controlling and setting the charge level of the lithium battery 14 to 90%, and receiving a signal from the battery management system (BMS) inside the lithium battery 14 to obtain the actual power level of the lithium battery 14. Finally, a first proportional-integral controller and a second proportional-integral controller are installed inside the PLC controller. The difference between the set rotational speed and the actual rotational speed of the main engine 1 is input to the first proportional-integral controller, and the output value obtained is set as the first current setting value of the chopper 13. When the propeller 3 becomes lighter, it indicates that the set rotational speed of the main engine 1 is lower than the actual rotational speed, and in this case the PLC controller controls the lithium battery 14 to charge. When the propeller 3 becomes heavier, it indicates that the set rotational speed of the main engine 1 is higher than the actual rotational speed, and in this case the PLC controller controls the lithium battery 14 to discharge, while setting the control bandwidth of the rotational speed of the main engine 1 by the PLC controller to 1 Hz. The difference between the set power of the lithium battery 14 and the actual power is input to the second proportional-integral controller, and the output value obtained is set as the second current setting value of the chopper 13. When the set power of the lithium battery 14 is lower than the actual power, the PLC controller controls whether to increase the discharge current or decrease the charge current of the chopper 13. When the set power of the lithium battery 14 is higher than the actual power, the PLC controller controls whether to increase the charge current or decrease the discharge current of the chopper 13, while setting the control bandwidth for charging and discharging the lithium battery 14 by the PLC controller to 0.01 Hz to achieve low-speed control. S6 includes the setting where the sum of the first current setting value and the second current setting value is the final current setting value for chopper 13.

[0047] Finally, it can be seen that circuit breakers are installed between the shaft motor 5 and the Dvdt filter, the isolation transformer 9 and the AC distribution panel 10, the ship's power plant 11 and the AC distribution panel 10, the AC distribution panel 10 and the daily load 12, and the inductor and lithium battery 14 to provide circuit protection.

[0048] The above description of the disclosed embodiments will enable those skilled in the art to implement or use the present invention. Various modifications of these embodiments will be apparent to those skilled in the art that the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the invention. Accordingly, the present invention is not limited to these embodiments shown herein and will conform to the broadest scope consistent with the principles and novel features disclosed herein. [Explanation of Symbols]

[0049] 1. Main engine; 2. Rotating shaft; 3. Propeller; 4. Optical encoder; 5. Shaft motor; 6. Rectifier; 7. DC train; 8. Inverter; 9. Isolation transformer; 10. AC switchboard; 11. Marine power plant; 12. Daily load; 13. Chopper; 14. Lithium battery.

Claims

1. A ship's shaft power generation system, The power module includes a main engine (1) controlled by a remote control handle, a rotating shaft (2) fixed to the output end of the main engine (1), and a propeller (3) fixed to the end of the rotating shaft (2). It is attached to the rotating shaft (2) and has a shaft motor (5) for switching between the generator and motor under different navigation conditions of the ship, The system has a frequency conversion control cabinet including a PLC controller and a frequency converter, the PLC controller is signal-connected to a remote control handle to obtain a set rotational speed of the main engine (1), and the frequency converter is connected to the shaft motor (5) via a cable to provide an AC voltage with a fixed voltage frequency. To convert the AC voltage output from the frequency converter into an acceptable operating voltage for the ship's daily load (12), an isolation transformer (9) is connected to the frequency converter via a cable. The ship has a ship power plant (11) connected in parallel to an isolation transformer (9) and an AC switchboard (10) via a cable, in order to supply power to the ship's daily load (12) and to provide a precharge voltage to the DC train using surplus power. It has a DC train (7) connected to the DC stage of the frequency converter via a cable, It has a chopper (13) connected to a DC train (7) via a cable, It has an internal battery management system and a lithium battery (14) connected to a chopper (13) via a cable. In order to obtain the actual power of the lithium battery while maintaining the lithium battery's power at 90% over the long term, the PLC controller and the lithium battery are connected via a bus CAN. The system has an optical encoder (4) attached to the rotating shaft (2) to detect the actual rotational speed of the rotating shaft (2) and the main engine (1) and to transmit the signal to the PLC controller. The PLC controller and the optical encoder are signal-connected via a cable to receive the signal from the optical encoder (4) and to obtain the actual rotational speed of the main engine (1). The PLC controller is further provided with a first proportional-integral controller and a second proportional-integral controller. The first proportional-integral controller takes the difference between the set rotational speed and the actual rotational speed of the main engine (1) as input and uses the output value obtained as the first current setting value of the chopper (13). The PLC controller is used to control the charging or discharging of the lithium battery (14). The second proportional-integral controller takes the difference between the set energy of the battery and the actual energy as input and uses the output value obtained as the second current setting value of the chopper (13). The PLC controller is used to control the fine adjustment of the chopper (13) current. A ship shaft power generation system characterized in that the sum of the first current setting value and the second current setting value of the chopper (13) is the final current setting value of the chopper (13).

2. The ship shaft power generation system according to claim 1, characterized in that a signal connection is made between the PLC controller and the remote control handle via a cable, the PLC controller receives a signal of 4mA to 20mA transmitted from the remote control handle and is used to obtain the rotational speed of the operation of the main engine (1) controlled by the remote control handle.

3. The ship shaft power generation system according to claim 2, characterized in that the shaft motor (5) has a power of 600 kW, a rotational speed of 64 rpm to 89 rpm, and an isolation transformer (9) has a capacity of 750 kVA.

4. The ship's shaft power generation system according to claim 3, characterized in that the frequency converter includes a rectifier (6) and an inverter (8), the rectifier (6) and the shaft motor (5) are connected via a cable, the inverter (8) and the rectifier (6) are connected via a cable, and the isolation transformer (9) and the inverter (8) are connected via a cable.

5. The ship's shaft power generation system according to claim 4, further characterized in that a Ddvdt filter is provided between the shaft motor (5) and the rectifier (6), a PWM filter is provided between the inverter (8) and the isolation transformer (9), and an inductor is further provided between the chopper (13) and the lithium battery (14).

6. The ship shaft power generation system according to claim 5, characterized in that circuit breakers are provided between the shaft motor (5) and the Ddvdt filter, the isolation transformer (9) and the AC distribution board (10), the ship power plant (11) and the AC distribution board (10), the AC distribution board (10) and the daily load (12), and the inductor and lithium battery (14).

7. The ship shaft power generation system according to claim 6, characterized in that the control bandwidth for the rotational speed of the main engine (1) by the PLC controller is 1 Hz, and the control bandwidth for the energy amount of the lithium battery (14) by the PLC controller is 0.01 Hz.

8. A shaft power generation method according to any one of claims 1 to 7, First, a shaft motor (5) is inserted into the rotating shaft (2) of the propeller (3) connected to the main engine (1), and at the same time, an optical encoder (4) is attached to the rotating shaft (2) to detect the actual rotational speed of the main engine (1) S1, Next, a frequency conversion control cabinet containing a PLC controller and a frequency converter is installed. The PLC controller is then signaled to the frequency converter via a cable, and then connected to the shaft motor (5) via a cable and used to output an AC voltage with a fixed voltage frequency. Here, the frequency converter includes a rectifier (6) and an inverter (8), and the shaft motor (5) and the rectifier (6) are connected via a cable, and the inverter (8) and the rectifier (6) are connected via a cable, S2 S3 connects an isolation transformer (9) and an inverter (8) via a cable to convert the AC voltage output from the frequency converter and make it suitable for use with the ship's daily load (12), Next, S4 connects the isolation transformer (9) and the ship's power plant (11) in parallel to the AC distribution panel (10) via a cable to supply power to the ship's daily load (12), A DC train (7) is connected to the DC stage between the rectifier (6) and the inverter (8) via a cable, and a portion of the ship's power plant (11) is used to supply power to the ship's daily load (12). When there is surplus power, the current from the ship's power plant (11) is sequentially connected to the DC train (7) through the isolation transformer (9) and the inverter (8), providing a precharge voltage to the DC train (7). A chopper (13) is connected to the DC train (7) via a cable, and then the chopper (13) is connected to the lithium battery (14) via a cable. A battery management system (BMS) is mounted on the circuit board inside the lithium battery (14) in S5. Finally, the PLC controller that controls the operation of the inverter is signal-connected via a dual cable to a remote control handle that controls the operation of the main engine (1), and receives a signal of 4 mA to 20 mA from the remote control handle, and further obtains the set rotational speed of the main engine (1). Next, the PLC controller is signal-connected via a cable to an optical encoder (4), and receives a signal from the optical encoder (4), and further obtains the actual rotational speed of the main engine (1). In addition, the PLC controller and the lithium battery (14) are connected via a bus CAN, and the charge amount of the lithium battery (14) is controlled and set to 90%, and a signal from the battery management system (BMS) inside the lithium battery (14) is received to obtain the actual power amount of the lithium battery (14). Finally, a first proportional-integral controller and a second proportional-integral controller are installed inside the PLC controller. The difference between the set rotational speed and the actual rotational speed of the main engine (1) is input to the first proportional-integral controller, and the output value obtained is set as the first current setting value of the chopper (13). When the propeller (3) becomes lighter, it indicates that the set rotational speed of the main engine (1) is lower than the actual rotational speed, and in this case the PLC controller controls the lithium battery (14) to charge. When the propeller (3) becomes heavier, it indicates that the set rotational speed of the main engine (1) is higher than the actual rotational speed, and in this case the PLC controller controls the lithium battery (14) to discharge while setting the control bandwidth of the rotational speed of the main engine (1) by the PLC controller to 1 Hz. The difference between the set energy amount and the actual energy amount of the lithium battery (14) is input to the second proportional-integral controller, and the output value obtained is set as the second current setting value of the chopper (13). At this time, if the set energy amount of the lithium battery (14) is lower than the actual energy amount, the PLC controller controls whether to increase the discharge current or decrease the charge current of the chopper (13). If the set energy amount of the lithium battery (14) is higher than the actual energy amount, the PLC controller controls whether to increase the charge current or decrease the discharge current of the chopper (13), while setting the control bandwidth of the charge and discharge of the lithium battery (14) by the PLC controller to 0.01 Hz. A shaft power generation method characterized by including S6, in which the sum of a first current setting value and a second current setting value is set to the final current setting value of the chopper (13).

Images