A method for preventing power failure of a power station with shaft generator by side pushing and capacity reduction

Abstract

A method for preventing the power failure of a power station with shaft generator by side thrust capacity reduction, first receiving the tripping signal of any one generator through the switchboard, and quickly sending the power limiting signal to the side thrust frequency converter to reduce the capacity. After receiving the capacity reduction signal, the side thrust frequency converter quickly reduces the speed. The side thrust frequency converter also monitors the DC voltage of its busbar. If the voltage drop is too large, it will also quickly reduce the speed. The specific speed reduction is triggered by the faster of the two commands. After speed reduction, the capacity is slowly increased to maintain the side thrust function to avoid affecting the safety of ship navigation. During the capacity increase process, the switchboard sends the remaining power signal of the power station. The side thrust receives the signal, gradually increases the capacity of the side thrust, and controls it within the remaining power of the power station. At the same time, the side thrust sends the side thrust power signal to the switchboard, so that the power station can accept the side thrust power in real time and update the remaining capacity of the power station, thereby ensuring the accuracy of the control.

Description

Technical Field

[0001] This invention belongs to the field of marine ship construction and design, and specifically relates to a method for preventing power loss of a shaft-driven power station by reducing the capacity of the side thruster. Background Technology

[0002] This project, building the world's first CO2 carrier for Norway, showcases the shipowner's high level of expertise and stringent requirements outlined in the specifications. Many of these requirements were unprecedented, including the demand to "maintain power to the station by reducing the side thrust capacity when a generator trips," which is a particularly demanding requirement. Because generator tripping usually happens unexpectedly and instantaneously, once a generator trips, the load of the entire power station will instantly be transferred to the remaining operating generators, causing these generators to overload. Their protection switches will quickly trip due to overload, and the entire power station will lose power. Moreover, the project is equipped with a shaft-driven generator whose frequency converter is extremely sensitive to overload and grid voltage drop, and the time from overload to power loss is usually within two or three seconds.

[0003] If one of the generators in this CO2 ship project loses power, and among the remaining operating generators is a shaft-driven generator, the challenge lies in rapidly reducing the thruster capacity while ensuring the power station remains operational and its function is gradually restored without affecting the thruster's use. This is a very difficult task. Furthermore, the shaft-driven generator is powered by the main engine; excessive load on it could overload the main engine, potentially causing it to shut down and compromising navigation safety. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preventing power loss in power plants with shaft generators by side-push derating, the technical solution of which is as follows: A method for preventing power loss in a power station with shaft-driven generators by side-push derating includes multiple generators, including diesel generators, shaft-driven generators, and side-push motors. The multiple generators are connected to the power distribution system signal; the side-push motors are connected to side-push frequency converters.

[0005] When any of the generators trips unexpectedly, a trip signal is sent to the power distribution system. After receiving the signal, the power distribution system immediately sends a power limit signal to the side-push inverter. After receiving the power limit signal, the side-push inverter controls the side-push motor to start decelerating.

[0006] Alternatively, when the side-push inverter detects a 20% voltage drop across the bus, it controls the side-push motor to begin slowing down.

[0007] After the side-push inverter is derated to near 0 RPM, the speed is slowly increased.

[0008] The side-push inverter receives the remaining available power signal from the distribution panel, and based on the remaining available power signal, the side-push inverter increases the power of the side-push motor to the upper limit.

[0009] The above-mentioned method for preventing power loss in a power station with a shaft-driven generator by side-pushing capacity reduction is further improved by connecting the shaft-driven generator to a shaft-driven frequency converter.

[0010] The above-mentioned method of preventing power loss in a power station with shaft generators by side-push capacity reduction can be further improved by connecting multiple generators in parallel.

[0011] The aforementioned method for preventing power loss in a power station with shaft generators by side-push capacity reduction further includes multiple diesel generators.

[0012] The aforementioned method for preventing power loss in a power station with a shaft generator by side-pushing derating is further improved by having a side-pushing frequency converter equipped with a DC bus.

[0013] The above-mentioned method for preventing power loss in a power station with a shaft generator by side-pushing capacity reduction further includes a shaft generator frequency converter with a DC bus.

[0014] The beneficial effects of this invention are: 1. It ensures that even if the generator trips unexpectedly, the power station will not lose power, thus guaranteeing the continuity of power supply.

[0015] 2. The problem of the shaft-driven generator frequency converter being sensitive to overload and power failure has been solved, avoiding the impact on the main unit.

[0016] 3. By controlling the thruster load using the available power of the power station, the normal operation of the thruster is basically guaranteed, avoiding the inability of the thruster to be used under special circumstances, thus ensuring the safety and normal operation of the ship. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the motor and switchboard system of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention; Among them, 1-diesel generator, 2-shaft-driven generator, 3-side-push motor, 4-shaft-driven frequency converter, 5-side-push frequency converter, 6-distribution panel. Detailed Implementation

[0018] The invention will be further described with reference to the accompanying drawings.

[0019] like Figure 1 The method shown is to prevent power loss in a power station with shaft-driven generators by side-push derating. There are multiple generators, including diesel generators, shaft-driven generators and side-push motors. The multiple generators are connected to the power distribution system signal; the side-push motors are connected to side-push frequency converters.

[0020] When any of the generators trips unexpectedly, a trip signal is sent to the power distribution system. After receiving the signal, the power distribution system immediately sends a power limit signal to the side-push inverter. After receiving the power limit signal, the side-push inverter controls the side-push motor to start decelerating.

[0021] Alternatively, when the side-push inverter detects a large voltage drop across the bus, it controls the side-push motor to begin slowing down.

[0022] When any generator trips unexpectedly, the power station is not prepared in advance and has not started the backup generator or performed priority tripping. It takes about ten seconds to start the backup generator or perform priority tripping temporarily. The project is also equipped with shaft-driven generators, whose frequency converters are extremely sensitive and usually trip within two or three seconds. Even if it is impossible to guarantee that the shaft-driven generators will not trip, it is necessary to find a special method to quickly reduce the capacity of the power station so that the remaining on-grid generators can withstand the load and ensure that the power station does not lose power.

[0023] To prevent power plant outages, it is necessary to quickly reduce the power plant load. De-capacity reduction of equipment is the fastest method, and it does not affect the use of the equipment. However, the equipment must have sufficient capacity and be frequency-controlled with stepless speed regulation. After research, side-push is the most suitable equipment.

[0024] The initial approach for the power distribution system to receive the trip signal and execute the process was to use a Power Management System (PMS) to monitor the remaining power in the grid. If the remaining power was zero, power limiting was implemented. This process took approximately five seconds, waiting until the generator had completely tripped and most of the load had been applied to the remaining generator. Additionally, the PMS monitoring signal required approximately 0.5 seconds of signal scanning, and the side-push inverter needed one to two seconds to perform derating of the side-push motor. The entire process took approximately six to eight seconds. Because this project was equipped with a shaft-driven generator, its inverter was exceptionally sensitive to overload and grid voltage drop; the time from overload to power loss was typically within two to three seconds. Therefore, conventional logic could not be used, as this would cause the shaft-driven generator to trip. Actual shipboard testing confirmed that the excessively long derating time did indeed cause the shaft-driven generator to trip, resulting in a power outage for the entire power station.

[0025] To save time, through discussion, research, and practical verification, it was decided not to use PMS to monitor the remaining power of the grid for power limiting. Instead, power limiting was triggered by the tripping signal of any generator switch. This saved approximately 5.5 seconds of time by eliminating the time required for PMS scanning and for the remaining power of the grid to become zero, thus shortening the entire process.

[0026] When the side-push inverter receives the power limit signal, it quickly sends a command to the side-push inverter through the PLC to reduce the speed of the side-push motor, thereby reducing the power of the side-push motor.

[0027] After the side-push inverter is derated to near 0 RPM, the speed is slowly increased.

[0028] To save time, the side-push inverter also monitors the bus voltage. If the voltage drop is significant (exceeding 20% ​​of the rated voltage), it is assumed that a generator has tripped, and derating is initiated. Therefore, derating is triggered by the faster response of this factor and the power limit command from the distribution system, saving valuable time to ensure that the side-push inverter is quickly derated before the shaft-driven generator trips due to overload, thus preventing the shaft-driven generator from tripping and ensuring stable operation of the power station.

[0029] Upon receiving a derating command, the side-push inverter quickly reduces the speed of the side-push motor to near zero RPM without shutting down the generator. This reduces the total load of the power station to a level that the remaining generators can handle. However, to prevent the inverter of the shaft generator from tripping, this derating process must be fast enough. Then, the motor speed is slowly increased (to the rated speed within approximately fifteen seconds). Since the side-push motor does not stop, its speed can be increased again relatively quickly without significantly affecting its operation.

[0030] The side-push inverter receives the remaining available power signal from the distribution panel, and based on the remaining available power signal, the side-push inverter increases the power of the side-push motor to the upper limit (100%).

[0031] While limiting power, the switchboard also sends a signal (analog signal, real-time adjustment) of the remaining available power of the power station to the thruster inverter. Based on the remaining available power, the thruster inverter gradually increases the thruster motor's power until it reaches approximately 95% of the available power limit. If it reaches 100%, the limit is triggered, and the power limiting logic restarts. After multiple tests, 95% was ultimately set as the optimal thruster power limit. When the available power of the power station meets the thruster's operating requirements—that is, the power station's power is sufficient for the thruster's operation—the motor speed command can be fully controlled by the control lever (manual operation), restoring normal operation. This essentially does not affect the normal use of the thruster, ensuring the ship's operational safety and normal use.

Claims

1. A method for preventing power loss in a power station with a shaft generator by side-push derating, characterized in that, There are multiple generators, including diesel generators, shaft-driven generators and side-push motors. The generators are connected to the power distribution system signal; the side-push motors are connected to side-push frequency converters. When any of the generators trips unexpectedly, a trip signal is sent to the power distribution system. After receiving the signal, the power distribution system immediately sends a power limit signal to the side-push inverter. After receiving the power limit signal, the side-push inverter controls the side-push motor to start decelerating. Alternatively, when the side-push inverter detects that the voltage drop of the inverter bus exceeds 20% of the rated voltage, the side-push inverter controls the side-push motor to start slowing down. After the side-push inverter is derated to near 0 RPM, the speed is slowly increased. The side-push inverter receives the remaining available power signal from the distribution panel, and based on the remaining available power signal, the side-push inverter increases the power of the side-push motor to the upper limit.

2. The method for preventing power loss in a power station with a shaft generator by side-push capacity reduction according to claim 1, characterized in that, The shaft-driven generator is connected to a shaft-driven frequency converter.

3. The method for preventing power loss in a power station with a shaft generator by side-push derating according to claim 1, characterized in that, Multiple generators are connected in parallel.

4. A method for preventing power loss in a power station with a shaft generator by side-push derating according to claim 1, characterized in that, There are multiple diesel generators.

5. A method for preventing power loss in a power station with a shaft generator by side-push derating according to claim 1, characterized in that, The side-push inverter has a DC busbar.

6. A method for preventing power loss in a power station with a shaft generator by side-push capacity reduction according to claim 2, characterized in that, The shaft-driven frequency converter has a DC busbar.

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