Ship shaft generator system and method

Abstract

The present invention relates to the technical field of ship shaft power generation, and in particular to a ship shaft generator system and method. The ship shaft generator system comprises a power module, a shaft-driven motor, a frequency conversion control cabinet, an isolation transformer, a ship power station, an alternating-current distribution board, a daily load, a direct current bar, a chopper, and a lithium battery. The power module comprises a main unit controlled by a handheld remote controller; a rotating shaft is fixed to an output end of the main unit; and a propeller is fixed to an end of the rotating shaft. The main unit is controlled to operate by means of the handheld remote controller in a cabin, and the main unit operates to drive the rotating shaft and the propeller to rotate to propel a ship to sail. The shaft-driven motor is mounted on the rotating shaft and used for switching between a generator and a motor under different sailing conditions of the ship. The present invention implements balance of charging and discharging of the lithium battery, thereby prolonging the service life of the lithium battery, enabling the shaft generator system to stably operate under various conditions, and improving the economic value of ship operation.

Description

Ship shaft power generation system and method

[0001] This invention claims priority to Chinese patent application number 202410303977.4, filed with the Patent Office of China on March 18, 2024, entitled “Ship Shaft Power Generation System and Method”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention belongs to the technical field of ship shaft-driven power generation, and in particular relates to a ship shaft-driven power generation system and method. Background Art

[0003] Traditional ship propulsion systems generally require two different types of diesel engines: the main propulsion diesel engine and the generator set diesel engine. The main propulsion diesel engine, also known as the "main engine" (hereinafter referred to as the "main engine"), is connected to the propeller and propels the ship. Due to different operating conditions, the propeller speed is constantly changing, so the main engine generally operates at a variable speed. The main engine speed responds to the setting value of the propulsion handle on the console. The generator set diesel engine is connected to a generator to form a "generator set", which supplies power to all loads in the ship's power station. Generally speaking, for reasons such as reliability, a ship's power station will consist of three or more generator sets. Since the output voltage and frequency of the generator set are almost fixed, the diesel engine used in the generator set generally operates at a constant speed, as shown in Figure 1.

[0004] In practice, when selecting main engine capacity, to ensure vessel performance, the main engine capacity is generally selected to be not only higher than the propeller characteristic curve, but also to retain a certain margin, resulting in the so-called "large engine, small propeller" feature. As shown in Figure 2, the main engine surplus capacity curve can be obtained by subtracting the propeller mechanical characteristic curve (the power required to ensure propeller rotation at different speeds, or the mechanical power that the propeller can absorb at different speeds) from the main engine capacity curve (referring to the energy output of the main engine at different speeds).

[0005] Currently, to reduce the use of generators, the surplus capacity of the main engine is used to provide a power station for the ship. That is, a generator is installed on the main shaft between the main engine and the propeller. This generator is called a "shaft generator", as shown in Figure 3. The output frequency of the shaft generator is proportional to the speed of the shaft motor. Since the speed of the shaft motor, the main shaft and the main engine are exactly the same, it can be considered that the output frequency of the shaft generator is proportional to the speed of the main engine. In order to obtain a stable frequency, a frequency conversion control cabinet is usually installed. The AC power output by the shaft generator is first converted into a fixed DC power through a rectifier (AC / DC). The fixed DC voltage is then converted into an AC voltage with a fixed voltage and frequency through an inverter (DC / AC). The fixed DC voltage is then supplied to the ship's power station for power. This frequency conversion control cabinet is generally also called a "shaft inverter", as shown in Figure 3.

[0006] When a ship is sailing, the generator set is usually shut down. Since the output voltage of a high-power shaft generator is usually 640V, while the ship's power station generally accepts 400V, an isolation transformer is usually installed to convert 640V to 400V. The shaft generator, shaft inverter, and isolation transformer are considered as a whole, which is called a "shaft power generation system", as shown in Figure 3. The use of a shaft power generation system can reduce the use of the generator set, save fuel consumption, and extend the life and maintenance cycle of the generator set.

[0007] However, during the use of ship shaft power generation systems, they are subject to the following two limitations:

[0008] 1. Output capacity limitation between the propeller and the propeller: As shown in Figure 4, the mechanical characteristic curve of the propeller is generally shown as curve A in Figure 4. In this case, the main engine capacity has sufficient margin to supply power to the shaft generator system. However, it should be noted that the mechanical characteristic curve of the propeller is not static, but changes with the resistance characteristics of the hull. Specifically, it is usually affected by the following conditions:

[0009] The influence of sea conditions (wind, waves, currents) can significantly affect the resistance characteristics of a ship. Usually, severe sea conditions will cause the mechanical characteristic curve of the propeller to rise, which is the so-called "propeller weighting";

[0010] The impact of cargo capacity: the heavier the cargo, the deeper the draft, the greater the resistance of the ship, and the heavier the propeller;

[0011] The impact of hull attachments: As a ship gradually becomes operational, the underwater part of the hull is prone to attachments like barnacles, which can increase the resistance of the ship and make the propeller heavier.

[0012] Therefore, when the ship encounters a heavy load and severe sea conditions, the mechanical characteristic curve of the propeller will move up from curve A in Figure 4 to curves B, C, and D. When the propeller works on curve B, the surplus capacity between the engine and propeller decreases, and as the speed decreases, the surplus capacity of the main engine decreases sharply. At the highest speed, the capacity curve of the main engine and the mechanical characteristic curve of the propeller intersect at b. At this time, the main engine has no margin to provide shaft-belt system power generation. When the propeller works on curves C or D, the capacity curve of the main engine and the mechanical characteristic curve of the propeller intersect at c or d respectively. At this time, the main engine cannot even make the propeller work at the highest speed and must reduce the speed. Considering that the speed of the ship is basically proportional to the speed of the propeller, not only can the shaft-belt power generation system not be used at this time, but the ship speed is also greatly reduced, resulting in a significant decline in the economy of the ship. At this time, the so-called "small engine and large propeller" situation has been entered.

[0013] 2. Limitations of unstable sea conditions: When a ship operates in unstable sea conditions, the mechanical characteristic curve of the propeller fluctuates; especially when the ship is running without load, the ship's draft is shallow, and under unstable sea conditions, the ship's propeller may occasionally be partially above the sea level (also known as "propeller out of water"), that is, it may occasionally fail to achieve full immersion; when the propeller is out of water, the propeller's mechanical characteristic curve becomes lighter; when the propeller enters the water, the propeller's mechanical characteristic curve becomes heavier; the propeller characteristic curve repeatedly changes between becoming heavier and becoming lighter. Please refer to Figure 5 for the power diagram; when the propeller's mechanical characteristic curve is unstable, it will eventually manifest as frequent changes in the main engine load, Even if the main engine control handle does not move at this time, when the load becomes lighter, the main engine speed will increase, and the main engine speed governor will reduce the throttle; when the load becomes heavier, the main engine speed will decrease, and the main engine speed governor will increase the throttle. Although it is unrealistic to determine a stable propeller load, by adjusting the throttle, under stable sea conditions, the main engine speed can be controlled within a stable range through the main engine speed governor. A typical main engine speed operation curve is shown in Figure 6. It can be seen that the main engine speed fluctuates between 83rpm and 86rpm, with a fluctuation range of only 3rpm. At this time, the main engine speed control is stable and effective;

[0014] However, in contrast, when unstable sea conditions occur, the main engine load experiences drastic fluctuations, and the main engine throttle adjustment speed is unable to adapt to the rapid load changes. Therefore, even with repeated adjustments, the speed cannot reach a balanced state. A typical main engine speed waveform for unstable sea conditions is shown in Figure 7. It can be seen that within approximately 1 minute, the main engine speed fluctuates from 76 rpm to 94 rpm, with approximately 10 peaks. Such drastic fluctuations not only affect the stability of the shaft generator system, but also increase emissions and fuel consumption due to incomplete combustion caused by repeated throttle adjustments.

[0015] Therefore, it is necessary to design a ship shaft-driven power generation system and method to overcome the above limitations, so that the shaft-driven power generation system can be used stably, and balance the main engine throttle changes caused by the propeller load, thereby increasing the economy of ship operation. Summary of the Invention

[0016] In order to solve the above technical problems, the present invention provides a ship shaft-driven power generation system and method to solve the problem raised in the above background technology that the shaft-driven power generation system on the existing market cannot be used normally and stably when it is limited by the output capacity between the engine and propeller and the unstable sea conditions.

[0017] To achieve the above object, the technical solution of the present invention is as follows:

[0018] The ship's shaft-driven power generation system includes a power module, a shaft-driven motor, a frequency conversion control cabinet, an isolation transformer, a ship power station, an AC distribution board, a daily load, a DC bus, a chopper, and a lithium battery. The power module includes a main engine controlled by a remote control handle. The main engine output end is fixed with a rotating shaft, and the end of the rotating shaft is fixed with a propeller. The main engine is controlled by a remote control handle in the cabin, and the main engine drives the rotating shaft and propeller to propel the ship.

[0019] The shaft belt motor is installed on the shaft and is used to switch between the generator and the motor under different navigation conditions of the ship. This allows the excess mechanical energy generated by the shaft rotation to be converted into electrical energy for storage. When the shaft rotates slowly, the previously stored electrical energy can be used to power the shaft belt motor, thereby increasing the speed of the shaft rotation.

[0020] The frequency conversion control cabinet includes a PLC controller and a frequency converter. The PLC controller is connected to the remote control handle signal to obtain the set speed of the main engine. The frequency converter is connected to the shaft belt motor via a cable to provide AC voltage with a fixed voltage and frequency. The isolation transformer is connected to the frequency converter via a cable to convert the AC voltage output by the frequency converter into an operating voltage acceptable to the ship's daily loads. The ship's power station and the isolation transformer are connected in parallel to the AC distribution board via a cable to supply power to the ship's daily loads while using excess power to provide pre-charge voltage for the DC bus.

[0021] The DC bus is connected to the DC section of the inverter via a cable; the chopper is connected to the DC bus via a cable; the lithium battery with an internal battery management system is connected to the chopper via a cable; the PLC controller is connected to the lithium battery via a bus CAN, which is used to control the lithium battery power to maintain 90% for a long time while obtaining the actual lithium battery power, making it easier to compare the set power level with the actual power level of the lithium battery.

[0022] The photoelectric encoder is installed on the shaft to detect the actual rotation speed of the shaft and the host and send the signal to the PLC controller. The PLC controller is connected to the photoelectric encoder through a cable signal to receive the signal sent by the photoelectric encoder, and then obtain the actual rotation speed of the host, which is convenient for comparing the set speed of the host with the actual speed.

[0023] The PLC controller is also provided with a first proportional-integral controller and a second proportional-integral controller. The first proportional-integral controller is used to obtain an output value after inputting the difference between the set speed and the actual speed of the main engine as the first current setting value of the chopper. When the propeller becomes lighter, it indicates that the set speed of the main engine is less than the actual speed. At this time, the PLC controller controls the charging of the lithium battery, which is equivalent to adding a virtual main engine load in disguise to reduce and stabilize the main engine's speed; when the propeller becomes heavier, it indicates that the set speed of the main engine is greater than the actual speed. At this time, the PLC controller controls the discharge of the lithium battery, which is equivalent to adding a virtual main engine power in disguise to increase and stabilize the main engine's speed; therefore, the charging and discharging of the lithium battery is controlled by the PLC controller to ensure that when the main engine capacity is insufficient, the propeller is provided with additional power, and when the main engine capacity is excessive, the main engine is provided with an additional load, so as to ultimately smooth out the fluctuations of the main engine and the throttle;

[0024] The second proportional-integral controller is used to input the difference between the set battery capacity and the actual battery capacity, and obtain the output value as the second current setting value of the chopper. That is, when the set battery capacity of the lithium battery is less than the actual battery capacity, the discharge current of the chopper is increased or the charging current is reduced; when the set battery capacity of the lithium battery is greater than the actual battery capacity, the charging current of the battery chopper is increased or the discharge current is reduced. The PLC controller uses this to control the fine adjustment of the chopper current to achieve a balance between the charging and discharging of the lithium battery, so that the shaft-driven generator system can operate stably and improve the economic efficiency of ship operation.

[0025] The sum of the first current setting value of the chopper and the second current setting value of the chopper is the final current setting value of the chopper.

[0026] Preferably, the PLC controller and the remote control handle are connected by a cable. The PLC controller is used to receive a 4mA-20mA signal sent by the remote control handle to realize signal transmission between the PLC controller and the remote control handle, so that the set speed of the host can be obtained normally.

[0027] Preferably, the power of the shaft motor is 600KW, the speed of the shaft motor is 64rpm-89rpm, the capacity of the isolation transformer is 750KVA, the 600V of the shaft motor is converted into 640V through the inverter, and then the 640V output of the inverter is converted into 400V through the isolation transformer, so that the current and voltage generated by the shaft power generation system can be normally used for the daily load of the ship.

[0028] Preferably, the frequency converter includes a rectifier and an inverter; the rectifier and the shaft belt motor are connected by a cable, and the inverter and the rectifier are connected by a cable; the isolation transformer and the inverter are connected by a cable to realize the conversion of the current generated by the shaft belt motor and finally obtain a fixed alternating current.

[0029] Preferably, a Dvdt filter is provided between the shaft motor and the rectifier, which can limit the rising rate of the output voltage of the inverter and protect the winding insulation of the generator; a PWM filter is provided between the inverter and the isolation transformer, which is mainly composed of a reactor, a capacitor and a resistor, and is used for harmonic suppression in the daily branch; a reactor is provided between the chopper and the lithium battery, which is a necessary passive device for the chopper circuit (Buck-Boost circuit). The switching requires the reactor to cooperate with energy storage in a short period of time, and also controls the current ripple in the chopper branch.

[0030] Preferably, circuit breakers are provided between the shaft belt motor and the Dvdt filter, the isolation transformer and the AC distribution board, the ship power station and the AC distribution board, the AC distribution board and the daily load, and the reactor and the lithium battery.

[0031] Preferably, the control bandwidth of the host speed by the PLC controller is set to 1Hz, so as to realize fast control of the actual speed of the host; the control bandwidth of the lithium battery power by the PLC controller is set to 0.01Hz, so as to realize low-speed control of the charging current and discharging current of the lithium battery.

[0032] A ship shaft power generation method comprises the following steps:

[0033] S1. First, insert a shaft-belt motor into the shaft connecting the main engine to the propeller, and install a photoelectric encoder on the shaft to detect the actual speed of the main engine;

[0034] S2. Next, a frequency conversion control cabinet is installed. The frequency conversion control cabinet includes a PLC controller and a frequency converter. The PLC controller and the frequency converter are connected by a cable. The shaft belt motor is then connected to the frequency converter through a cable to output an AC voltage with a fixed voltage frequency.

[0035] The frequency converter includes a rectifier and an inverter, the shaft motor is connected to the rectifier through a cable, and the inverter is connected to the rectifier through a cable;

[0036] S3. Then, connect the isolation transformer to the inverter through a cable to convert the AC voltage output by the inverter to be suitable for daily load use on ships;

[0037] S4. Then, the isolation transformer and the ship power station are connected in parallel to the AC distribution board through cables to supply power to the ship's daily loads;

[0038] S5. Then, a cable is used to connect the DC busbar to the DC section between the rectifier and the inverter. Part of the ship's power station is used to power the ship's daily loads. When there is excess power, the current of the ship's power station will be connected to the DC busbar through the isolation transformer and inverter in sequence to provide pre-charge voltage for the DC busbar.

[0039] The DC bus is connected to a chopper via a cable, which is then connected to a lithium battery via a cable. A battery management system (BMS) is installed on the circuit board inside the lithium battery.

[0040] S6. Finally, the PLC controller that controls the operation of the frequency converter is connected to the remote control handle signal that controls the operation of the host through a dual cable to receive the signal from the remote control handle, thereby obtaining the set speed of the host; then, the PLC controller is connected to the photoelectric encoder signal through a cable to receive the signal from the photoelectric encoder, thereby obtaining the actual speed of the host; then, the PLC controller is connected to the lithium battery through the bus CAN to control and set the charging capacity of the lithium battery to 90%, and at the same time receive the signal from the battery management system (BMS) inside the lithium battery to obtain the actual capacity of the lithium battery; finally, a first proportional integral controller and a second proportional integral controller are set inside the PLC controller;

[0041] By inputting the difference between the host's set speed and actual speed into the first proportional-integral controller and then outputting the value as the first current setting value of the chopper, when the propeller becomes lighter, it indicates that the host's set speed is less than the actual speed. At this time, the PLC controls the charging of the lithium battery; when the propeller becomes heavier, it indicates that the host's set speed is greater than the actual speed. At this time, the PLC controller controls the discharge of the lithium battery and sets the control bandwidth of the PLC controller for controlling the host 1 speed to 1Hz to achieve fast control;

[0042] By inputting the difference between the set value of the lithium battery's power and the actual power value into the second proportional-integral controller and then outputting the value as the second current setting value of the chopper, when the set power of the lithium battery is lower than the actual power, the PLC controller will control to increase the discharge current of the chopper or reduce the charging current; when the set power of the lithium battery is higher than the actual power, the PLC controller will control to increase the charging current of the chopper or reduce the discharge current, and the control bandwidth of the PLC controller for controlling the charging and discharging of the lithium battery 14 is set to 0.01Hz, so as to achieve low-speed and slow control;

[0043] The sum of the first current setting value and the second current setting value is the final current setting value of the chopper.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention determines whether the propeller is becoming lighter or heavier by judging the difference between the set speed and the actual speed of the main engine. It then controls the charging and discharging of the lithium battery in a targeted manner. This ensures that when the main engine capacity is insufficient, the propeller is provided with additional power. When the main engine capacity is excessive, the main engine is provided with an additional load, ultimately smoothing out fluctuations in the main engine and throttle.

[0046] At the same time, by controlling the lithium battery power and setting it at 90%, and then comparing it with the actual power of the lithium battery, the chopper current is fine-tuned to achieve a balance between the charge and discharge of the lithium battery, thereby improving the service life of the lithium battery and enabling the shaft-driven power generation system to operate stably under various conditions, thereby increasing the economic efficiency of ship operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 is a schematic diagram of an existing ship power system;

[0049] FIG2 is a schematic diagram of a curve reflecting the surplus capacity of the main engine in an existing ship power system;

[0050] FIG3 is a schematic diagram of a shaft-driven power generation system in an existing ship power system;

[0051] FIG4 is a schematic diagram of a mechanical characteristic curve of a propeller of an existing ship shaft-driven power generation system when the output capacity between the engine and the propeller is limited;

[0052] FIG5 is a schematic diagram of the power of an existing ship shaft generator system when it is restricted by unstable sea conditions;

[0053] FIG6 is a schematic diagram of a typical main engine speed operating curve in an existing ship shaft generator system;

[0054] FIG7 is a schematic diagram of a typical main engine speed waveform in an existing ship shaft generator system under unstable sea conditions;

[0055] FIG8 is a schematic diagram of shaft-belt power generation according to the present invention;

[0056] FIG9 is a schematic diagram showing the calculation principle of the final set value of the current of the chopper in the present invention;

[0057] FIG10 is a schematic diagram of the control flow of the present invention;

[0058] FIG11 is a schematic circuit diagram of a lithium battery pack, a chopper, and a DC bus in the present invention;

[0059] FIG12 is a circuit diagram of the shaft belt motor, rectifier and DC busbar of the present invention;

[0060] FIG13 is a circuit diagram of a DC bus, an inverter, an isolation transformer, an AC distribution board, and daily loads in the present invention.

[0061] The reference numerals in the above drawings represent the following parts:

[0062] 1. Main engine; 2. Rotating shaft; 3. Propeller; 4. Photoelectric encoder; 5. Shaft-belt motor; 6. Rectifier; 7. DC bus; 8. Inverter; 9. Isolation transformer; 10. AC distribution board; 11. Ship power station; 12. Daily load; 13. Chopper; 14. Lithium battery. DETAILED DESCRIPTION

[0063] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0064] The present invention provides the following embodiments:

[0065] 1-13 , the ship shaft-driven power generation system includes a power module, a shaft-driven motor 5 , a frequency converter, an isolation transformer 9 , an AC distribution board 10 , a ship power station 11 , and a daily load 12 ;

[0066] With reference to Figures 1, 3, 5, 8, and 10, it can be seen that the power module includes a main engine 1, a rotating shaft 2, and a propeller 3. The main engine 1 is controlled by a crew member in the cabin using a remote control handle. The remote control handle is connected to the main engine 1 via a cable. When the main engine 1 is working, it drives the rotating shaft 2 and the propeller 3 to rotate, thereby generating thrust to propel the ship to sail.

[0067] With reference to Figures 3, 5, 8, and 10, it can be seen that a shaft belt motor 5 is mounted on the rotating shaft 2. The shaft belt motor 5 is connected to a circuit breaker via a cable. The circuit breaker is connected to a DVDT filter via a cable. The DVDT filter is connected to a rectifier 6 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 to a ship power station 11 in parallel with an AC distribution board 10 via a cable to supply power to the ship's daily loads 12. 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 power station 11 and the AC distribution board 10; and a circuit breaker is also provided between the AC distribution board 10 and the daily loads 12.

[0068] The shaft motor 5 consists of two parts: a rotating part and a fixed part. The rotating part is called the "rotor" and the fixed 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 drives the "rotor" to rotate through the rotation of the rotating shaft 2, thereby converting mechanical energy into electrical energy. The output current flows to the rectifier 6 after passing through the circuit breaker and the DVDT filter, and is converted into direct current. The DVDT filter can limit the rise rate of the inverter output voltage and protect the winding insulation of the generator.

[0069] The DC current converted by the rectifier 6 is sent to the inverter 8, which converts the DC power into AC power. At this time, the AC power passes through the PWM filter and flows to the isolation transformer 9, which converts the AC voltage output by the inverter into an operating voltage acceptable to the ship's daily load 12. The power of the shaft belt motor 5 is 600KW, and the speed of the shaft belt motor 5 is 64rpm-89rpm; the capacity of the isolation transformer 9 is 750KVA. That is, the output voltage of the shaft belt motor 5 of 600V is converted to 640V by the inverter, and then the isolation transformer 9 converts the output voltage of the inverter to 400V suitable for the ship's daily load 12, so that the current and voltage generated by the shaft belt power generation system can be normally used for the ship's daily load 12. The PWM filter is mainly composed of a reactor, a capacitor and a resistor, and is used to suppress harmonics in the daily branch.

[0070] The AC current converted by the isolation transformer 9 is fed into the AC distribution board 10 through the circuit breaker and supplied to the daily load 12;

[0071] The ship power station 11 includes a first generator set and a second generator set. The currents of the two generator sets are both connected to the AC distribution board 10 through the circuit breaker and are also used by the daily load 12.

[0072] Referring to FIG. 10 , it can be seen that the rectifier 6 and the inverter 8 are both installed in a frequency conversion control cabinet, which is also provided with a plc controller. The plc controller is connected to the rectifier 6 and the inverter 8 through cables to control the operation of the rectifier 6 and the inverter 8.

[0073] The PLC controller is also connected to the remote control handle signal that controls the operation of the host 1 through a cable. When the remote control handle is used, it will control the operation of the host 1 and at the same time transmit a 4mA-20mA signal to the PLC controller, thereby obtaining the rotation speed of the host 1 at this time. At this time, the rotation speed of the host 1 is the set speed; a photoelectric encoder 4 is also installed on the shaft 2. The photoelectric encoder 4 is connected to the PLC controller through a cable signal. When the host 1 is working, it drives the shaft 2 and the propeller 3 to rotate. At this time, the photoelectric encoder 4 will detect the rotation speed of the shaft 2 and transmit the rotation speed to the PLC controller. At this time, the rotation speed of the shaft 2 is the actual rotation speed of the host 1;

[0074] Referring to Figures 8 and 10 , it can be seen that a DC bus 7 is connected to the DC section cable between the rectifier 6 and the inverter 8 , the DC bus 7 is connected to the chopper 13 via a cable, the chopper 13 is connected to a reactor via a cable, the reactor is connected to the lithium battery 14 via a cable, a circuit breaker is provided on the cable between the reactor and the lithium battery 14 , and a battery management system (BMS) is installed on the circuit board inside the lithium battery 14 , the lithium battery 14 is connected to the PLC controller via the bus CAN, and the battery management system (BMS) transmits the detected power level of the lithium battery 14 to the PLC controller, at which point the actual power level of the lithium battery 14 is obtained;

[0075] During operation, as shown in FIG12 , the current generated by the shaft belt motor 5 is converted into direct current by the rectifier 6 and then converged onto the DC bus 7. Part of the direct current flows through the DC bus 7 to the inverter 8, and then continues to flow until it converges onto the AC distribution board 10 to power the daily load 12. Another part of the direct current flows through the DC bus 7 to the chopper 13, and then flows through the reactor and circuit breaker to the lithium battery 14 for charging and discharging of the lithium battery 14.

[0076] Referring to Figures 11 and 13 , it can be seen that when the power used by the daily loads 12 in the ship is less than the power of the ship power station 11, the ship power station 11 can use the excess power to direct the current through the AC distribution board 10 to the isolation transformer 9, then through the PWM filter to the inverter 8, and then to the DC bus 7 to provide a pre-charge voltage for the DC bus 7;

[0077] At the same time, the algorithm is input into the PLC controller, as shown in Figure 9:

[0078] The PLC controller is also provided with a first proportional integral controller and a second proportional integral controller;

[0079] First, the difference between the set speed and the actual speed of the host 1 received by the PLC controller is input into the first proportional-integral controller, and the value output by the first proportional-integral controller is used as the first current setting value of the chopper 13. When the propeller 3 becomes lighter, it indicates that the set speed of the host 1 is less than the actual speed. At this time, the PLC controller controls the charging of the lithium battery 14, which is equivalent to adding a virtual host load in disguise to reduce and stabilize the actual speed of the host 1; when the propeller 3 becomes heavier, it indicates that the set speed of the host 1 is greater than the actual speed. At this time, the PLC controller controls the discharge of the lithium battery 14, which is equivalent to adding a virtual host power in disguise to increase and stabilize the actual speed of the host 1;

[0080] The charge and discharge of the lithium battery 14 is controlled by the PLC controller to ensure that when the capacity of the main engine 1 is insufficient, the propeller 3 is provided with additional power, and when the capacity of the main engine 1 is excessive, an additional load is provided to the main engine 1, thereby ultimately smoothing out the fluctuations of the main engine 1 and the throttle.

[0081] Among them, referring to Figures 6 and 7, it can be seen that under unstable sea conditions, the speed waveform of the main engine 1 fluctuates from 76 rpm to 94 rpm in about 1 minute, with about 10 peaks. In this case, the frequency bandwidth of the main engine 1 speed is about 0.16 Hz, so it is necessary to control the speed of the main engine 1. The control bandwidth of the PLC controller needs to be greater than the frequency bandwidth of the main engine 1 speed to achieve control of the main engine 1 speed. However, since this situation is under unstable sea conditions, the actual situation fluctuates and changes rapidly, so the control of the main engine 1 speed also needs to be fast. Therefore, the present invention preferably sets the control bandwidth of the PLC controller to 1 Hz to achieve rapid control of the main engine 1 speed.

[0082] At the same time, the charge and discharge capacity of the lithium battery 14 is controlled and set to 90%. At this time, the set capacity value of the lithium battery 14 is compared with the actual capacity of the lithium battery 14 transmitted to the PLC controller via the battery management system (BMS). The difference between the two is input into the second proportional integral controller, and the output value is used as the second current setting value of the chopper 13. When the set capacity of the lithium battery 14 is less than the actual capacity, the PLC controller controls to increase the discharge current of the chopper 13 or reduce the charging current; when the set capacity of the lithium battery 14 is greater than the actual capacity, the PLC controller controls to increase the charging current of the battery chopper or reduce the discharge current;

[0083] Thus, the PLC controller controls the fine adjustment of the current of the chopper 13 to achieve a balance between the charge and discharge of the lithium battery 14, thereby increasing the service life of the lithium battery 14 and ensuring the stable operation of the shaft-driven power generation system, thereby increasing the economic efficiency of the ship operation.

[0084] Since the charging and discharging process of the lithium battery 14 is relatively slower than the speed change of the host 1, the charging and discharging process of the lithium battery 14 can be controlled at a low speed. The present invention sets the control bandwidth of the PLC controller for controlling the charging and discharging of the lithium battery 14 to 0.01HZ to achieve low-speed control;

[0085] The sum of the first current setting value and the second current setting value is the final current setting value of the chopper 13 .

[0086] Referring to Figures 1-13 , the ship shaft power generation method includes the following steps:

[0087] S1. First, insert a shaft-belt motor 5 into the rotating shaft 2 connecting the main engine 1 to the propeller 3. At the same time, install a photoelectric encoder 4 on the rotating shaft 2 to detect the actual speed of the main engine 1;

[0088] S2. Next, a frequency conversion control cabinet is installed. The frequency conversion control cabinet includes a PLC controller and a frequency converter. The PLC controller and the frequency converter are connected by a cable. Then, the shaft belt motor 5 is connected to the frequency converter through a cable to output an AC voltage with a fixed voltage frequency.

[0089] The frequency converter includes a rectifier 6 and an inverter 8. The shaft motor 5 is connected to the rectifier 6 via a cable, and the inverter 8 is connected to the rectifier 6 via a cable. A Dvdt 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. A reactor is provided between the chopper 13 and the lithium battery 14.

[0090] S3. Then, the isolation transformer 9 is connected to the inverter 8 via a cable to convert the AC voltage output by the inverter to be suitable for use by the daily load 12 of the ship;

[0091] S4, then connect the isolation transformer 9 and the ship power station 11 in parallel to the AC distribution board 10 through cables to supply power to the ship's daily loads 12;

[0092] S5. Then, the DC section between the rectifier 6 and the inverter 8 is connected to the DC bus 7 via a cable. Part of the ship power station 11 is used to power the ship's daily loads 12. When there is excess power, the current of the ship power station 11 will be connected to the DC bus 7 through the isolation transformer 9 and the inverter 8 in sequence to provide pre-charge voltage for the DC bus 7.

[0093] The DC bus 7 is connected to a chopper 13 via a cable, and the chopper 13 is then connected to a lithium battery 14 via a cable. A battery management system (BMS) is installed on a circuit board inside the lithium battery 14.

[0094] S6. Finally, the PLC controller that controls the frequency converter is connected to the remote control handle signal that controls the host 1 through a dual cable, so as to receive the 4mA-20mA signal sent by the remote control handle, thereby obtaining the set speed of the host 1; then, the PLC controller is connected to the photoelectric encoder 4 signal through a cable, so as to receive the signal of the photoelectric encoder 4, thereby obtaining the actual speed of the host 1; then, the PLC controller is connected to the lithium battery 14 through the bus CAN, so as to control and set the charging capacity of the lithium battery 14 to 90%, and at the same time receive the signal sent by the battery management system BMS inside the lithium battery 14 to obtain the actual capacity of the lithium battery 14; finally, a first proportional integral controller and a second proportional integral controller are set inside the PLC controller;

[0095] By inputting the difference between the set speed and the actual speed of the main engine 1 into the first proportional-integral controller, the output value is used as the first current setting value of the chopper 13. At this time, when the propeller 3 becomes lighter, it indicates that the set speed of the main engine 1 is less than the actual speed. At this time, the PLC controls the charging of the lithium battery 14; when the propeller 3 becomes heavier, it indicates that the set speed of the main engine 1 is greater than the actual speed. At this time, the PLC controller controls the discharge of the lithium battery 14 and sets the control bandwidth of the PLC controller for controlling the speed of the main engine 1 to 1Hz.

[0096] The difference between the set value of the power of the lithium battery 14 and the actual power value is input into the second proportional-integral controller, and the output value is used as the second current setting value of the chopper 13. At this time, when the set power of the lithium battery 14 is lower than the actual power, the PLC controller will control to increase the discharge current of the chopper 13 or reduce the charging current; when the set power of the lithium battery 14 is higher than the actual power, the PLC controller will control to increase the charging current of the chopper 13 or reduce the discharge current, and the control bandwidth of the PLC controller for controlling the charging and discharging of the lithium battery 14 is set to 0.01Hz;

[0097] The sum of the first current setting value and the second current setting value is the final current setting value of the chopper 13 .

[0098] Finally, it can be seen that circuit breakers are installed between the shaft belt motor 5 and the DVDT filter, the isolation transformer 9 and the AC distribution board 10, the ship power station 11 and the AC distribution board 10, the AC distribution board 10 and the daily load 12, and the reactor and the lithium battery 14 for circuit protection.

[0099] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ship shaft power generation system, characterized in that: include: A power module includes a main unit (1) controlled by a remote control handle, a rotating shaft (2) being fixed to an output end of the main unit (1), and a propeller (3) being fixed to an end of the rotating shaft (2); A shaft motor (5) is mounted on the rotating shaft (2) and is used to switch between the generator and the motor under different navigation conditions of the ship; A frequency conversion control cabinet includes a PLC controller and a frequency converter, wherein the PLC controller is connected to a remote control handle signal to obtain a set speed of the host (1); the frequency converter is connected to the shaft belt motor (5) via a cable to provide an AC voltage with a fixed voltage frequency; An isolation transformer (9), connected to the frequency converter via a cable, for converting the AC voltage output by the frequency converter into an operating voltage acceptable to the ship's daily load (12); The ship power station (11) is connected in parallel with the isolation transformer (9) via a cable to the AC distribution board (10), and is used to supply power to the ship's daily load (12) while using excess power to provide pre-charge voltage for the DC bus; A DC busbar (7) is connected to the DC section of the inverter via a cable; A chopper (13) is connected to the DC bus (7) via a cable; A lithium battery (14) with a battery management system installed inside is connected to the chopper (13) via a cable; a PLC controller is connected to the lithium battery via a bus CAN, and is used to control the lithium battery power to be maintained at 90% for a long time while obtaining the actual power of the lithium battery; A photoelectric encoder (4) is mounted on the rotating shaft (2) and is used to detect the actual rotation speed of the rotating shaft (2) and the host (1) and send a signal to the PLC controller. The PLC controller is connected to the photoelectric encoder via a cable signal and is used to receive the signal sent by the photoelectric encoder (4) to obtain the actual rotation speed of the host (1); The PLC controller is further provided with a first proportional integral controller and a second proportional integral controller, wherein the first proportional integral controller is used to input the difference between the set speed and the actual speed of the host (1) and obtain an output value as a first current setting value of the chopper (13), and the PLC controller controls the charging or discharging of the lithium battery (14) based on this. The second proportional integral controller is used to input the difference between the set battery capacity and the actual battery capacity, and obtain an output value as the second current setting value of the chopper (13), so that the PLC controller can control the fine adjustment of the current of the chopper (13); The sum of the first current setting value of the chopper (13) 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: The PLC controller and the remote control handle are connected by a cable. The PLC controller is used to receive a 4mA-20mA signal from the remote control handle to obtain the speed of the remote control handle to control the host (1).

3. The ship shaft power generation system according to claim 2, characterized in that: The power of the shaft-belt motor (5) is 600KW, and the speed of the shaft-belt motor (5) is 64rpm-89rpm; the capacity of the isolation transformer (9) is 750KVA.

4. The ship 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 belt motor (5) are connected via a cable, and 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 shaft power generation system according to claim 4, characterized in that: A Dvdt filter is provided between the shaft-belt motor (5) and the rectifier (6); a PWM filter is provided between the inverter (8) and the isolation transformer (9); and a reactor is 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 belt motor (5) and the DVDT filter, the isolation transformer (9) and the AC distribution board (10), the ship power station (11) and the AC distribution board (10), the AC distribution board (10) and the daily load (12), and the reactor and the lithium battery (14).

7. The ship shaft power generation system according to claim 6, characterized in that: The control bandwidth of the PLC controller for the rotation speed of the host (1) is set to 1 Hz; the control bandwidth of the PLC controller for the power of the lithium battery (14) is set to 0.01 Hz.

8. The shaft power generation method of a ship shaft power generation system according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. First, a shaft-belt motor (5) is inserted into the rotating shaft (2) connecting the main engine (1) to the propeller (3), and a photoelectric encoder (4) is installed on the rotating shaft (2) to detect the actual speed of the main engine (1); S2. Next, a frequency conversion control cabinet is installed. The frequency conversion control cabinet includes a PLC controller and a frequency converter. The PLC controller and the frequency converter are connected via a cable. The shaft belt motor (5) is then connected to the frequency converter via a cable to output an AC voltage with a fixed voltage frequency. The frequency converter includes a rectifier (6) and an inverter (8), the shaft motor (5) is connected to the rectifier (6) via a cable, and the inverter (8) is connected to the rectifier (6) via a cable; S3, then connecting the isolation transformer (9) to the inverter (8) through a cable, converting the AC voltage output by the inverter to be suitable for use with the ship's daily load (12); S4, then connect the isolation transformer (9) and the ship power station (11) in parallel to the AC distribution board (10) through cables to supply power to the ship's daily load (12); S5, then the DC section between the rectifier (6) and the inverter (8) is connected to a DC bus (7) through a cable, and a portion of the ship power station (11) is used to power the ship's daily load (12). When there is excess power, the current of the ship power station (11) will be connected to the DC bus (7) through the isolation transformer (9) and the inverter (8) in sequence to provide pre-charge voltage for the DC bus (7); A chopper (13) is connected to the DC bus (7) via a cable, and the chopper (13) is then connected to a lithium battery (14) via a cable, wherein a battery management system (BMS) is installed on a circuit board inside the lithium battery (14); S6. Finally, the PLC controller that controls the operation of the frequency converter is connected to the remote control handle signal that controls the operation of the host (1) through a double cable, so as to receive the 4mA-20mA signal sent by the remote control handle, thereby obtaining the set speed of the host (1); then, the PLC controller is connected to the photoelectric encoder (4) signal through a cable, so as to receive the signal of the photoelectric encoder (4), thereby obtaining the actual speed of the host (1); then, the PLC controller is connected to the lithium battery (14) through the bus CAN, so as to control and set the charging power of the lithium battery (14) to 90%, and at the same time receive the signal sent by the battery management system (BMS) inside the lithium battery (14), thereby obtaining the actual power of the lithium battery (14); finally, a first proportional integral controller and a second proportional integral controller are set inside the PLC controller; By inputting the difference between the set speed of the host (1) and the actual speed into the first proportional integral controller, the output value is used as the first current setting value of the chopper (13). At this time, when the propeller (3) becomes lighter, it indicates that the set speed of the host (1) is less than the actual speed. At this time, the PLC controls the lithium battery (14) to charge; when the propeller (3) becomes heavier, it indicates that the set speed of the host (1) is greater than the actual speed. At this time, the PLC controller controls the lithium battery (14) to discharge, and the control bandwidth of the PLC controller for controlling the speed of the host 1 is set to 1 Hz; The difference between the set value of the power of the lithium battery (14) and the actual power value is input into the second proportional integral controller, and the output value is used as the second current setting value of the chopper (13). At this time, when the set power of the lithium battery (14) is lower than the actual power, the PLC controller will control to increase the discharge current of the chopper (13) or reduce the charging current; when the set power of the lithium battery (14) is higher than the actual power, the PLC controller will control to increase the charging current of the chopper (13) or reduce the discharge current, and the control bandwidth of the PLC controller for controlling the charging and discharging of the lithium battery 14 is set to 0.01 Hz; The sum of the first current setting value and the second current setting value is the final current setting value of the chopper (13).

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