A vibration suppression method for a ship parallel hybrid power system

Abstract

The present invention relates to a vibration suppression method for a ship parallel hybrid power system, including: 1) analyzing and determining the system vibration source; 2) analyzing the excitation source; 3) vibration criterion; 4) shaft alignment and flexible alignment of the elastic coupling; 5) flexible matching of the shaft-driven motor variable frequency system. The present invention aims at vibration suppression of the ship parallel hybrid power system, masters the key technologies of excitation and response matching between the mechanical and electrical systems, improves the matching and operation reliability of the parallel hybrid power system; meanwhile, this achievement can be widely applied to ships with other power propulsion types.

Description

Technical Field

[0001] The present invention relates to a method for suppressing vibration of a parallel hybrid power system for ships. Background Art

[0002] With the demand for green energy conservation in ships, the propulsion system has gradually evolved from a single-power-output propulsion of conventional propulsion to the application of complex systems such as electro-mechanical parallel hybrid and multi-output shafts in hybrid power. Different characteristics exist among the branches in a multi-branch system, which will cause mutual excitation, and this will correspondingly increase the risk of system or local vibration. If vibration control is ignored, it is very easy to cause harmful vibration, affecting the normal operation of the system and equipment, and seriously, it will lead to fatigue damage of the system and equipment.

[0003] The hybrid power system is divided into two types: series hybrid and parallel hybrid. The series hybrid type is a single-power-output of motor + propeller, with simple excitation and power branches and low vibration risk. The parallel hybrid is a combination of diesel and electricity, where the motor can generate electricity and also be used for electric propulsion. The system excitation and power branches are complex, and poor matching will cause abnormal vibration.

[0004] In recent years, with the wide application of diesel-electric hybrid power, especially shaft-driven variable-frequency technology, some abnormal vibration problems have occurred during system operation, which are beyond the original understanding. These vibrations generally seem to maintain a constant vibration frequency when the motor shaft speed changes and can be monitored through the waveform of the frequency converter. It seems to be generally torsional vibration. Once the amplitude increases, especially the high-elastic coupling on the motor side is extremely easy to be damaged.

[0005] One way of vibration control is the setting of damping. After the ship type is designed, the propulsion type / power level is relatively fixed, so the setting and adjustment of damping in the system are relatively simplified. Therefore, it is necessary to analyze the damping characteristics, study simple and effective adjustment methods, and effectively suppress harmful vibration through the flexible matching of "machinery" and "electricity". Summary of the Invention

[0006] The purpose of the present invention is to provide a method for suppressing vibration of a parallel hybrid power system for ships to solve the vibration problem of the parallel hybrid power system. This method provides a new design idea for suppressing vibration of a parallel hybrid power system for ships by checking and eliminating the selection, setting, and installation of mechanical damping, combining the damping characteristics of the shaft-driven motor variable-frequency system, and performing damping parameter matching for the DC power transmission system, and proposing a vibration adjustment method applicable to the shaft-driven motor variable-frequency system.

[0007] To achieve the above purpose, the technical solution of the present invention is: a method for suppressing vibration of a parallel hybrid power system for ships, including:

[0008] 1) Analyze and determine the vibration source of the system

[0009] Calculate and analyze various exciting forces that may cause vibrations in a parallel hybrid power system, compare them with the natural frequencies of the vibrating body, and gradually eliminate the possibility of resonance;

[0010] 2) Analyze the excitation source

[0011] Change the natural frequency of the vibrating body, change the excitation source, and increase the damping;

[0012] 3) Vibration criterion

[0013] Within the operating speed range of the system, analyze and determine the main exciting forces and their frequencies, and the exciting forces should not exceed the specified values; within the maximum operating speed range of the system, analyze and determine the main vibration frequencies of the vibrating body, and the ratio of the main vibration frequency to the main exciting frequency should meet the requirements of the specification, and the results of the shafting calculation should meet the requirements of the specification and standards;

[0014] 4) Shafting alignment and alignment of elastic couplings

[0015] Perform alignment according to the alignment calculation book approved by the classification society and the compensation for ambient temperature and hot conditions. After the shafting, gearbox, and main engine alignment are inspected and approved, perform the alignment of the shaft generator. After the alignment result is inspected and approved, the installation method of the motor base meets the installation requirements of the equipment, and the torque of the foundation bolts meets the requirements;

[0016] 5) Flexible matching of the variable-frequency system of the shaft generator

[0017] When the power generation load changes, if the current loop control is not well matched, it will cause oscillations between the speed fluctuations of the shaft generator and the torsional energy storage of the high-elasticity, and if the oscillation is amplified, it is easy to cause damage to the high-elasticity due to heat. When the unbalanced torque of the main engine is large and the control accuracy and response speed of its speed control system are not high, adjust the damping parameters of the shaft generator frequency converter to suppress the instability of the system through flexible matching.

[0018] Furthermore, the changing of the natural frequency of the vibrating body includes changing the shaft diameter, bearing spacing, propeller size, and number of propeller blades.

[0019] Furthermore, the changing of the excitation source includes changing the clearance between the propeller and the hull and shafting alignment;

[0020] Furthermore, the increasing of the damping includes the stiffness adjustment of the elastic coupling and the size and performance of the shock absorber.

[0021] Furthermore, the method also includes vibration monitoring: when the shaft generator starts to operate initially, closely monitor the states of the motor, motor coupling, and main engine. First, run it without load and then gradually and slowly load it. During this period, measure the temperature of the rubber parts of the coupling and the vibration displacement. In case of any abnormality, stop the machine immediately. Under each working condition, check the temperature of the frequency converter, the temperature of the motor bearings and windings, the current / voltage / frequency, vibration, and abnormal noise of the motor and frequency converter.

[0022] Furthermore, the flexible matching of the shaft-driven motor variable-frequency system also includes the adjustment and matching of the inverter damping: Any mode of the inverter uses a current loop to control the current / torque while the system controls the speed and position, so as to achieve the corresponding control of the speed and position. Among them, a required speed signal is given, subtracted from the feedback speed signal, and this difference is sent to the speed loop of the speed governor. The difference between the output of the speed loop and the current detection feedback signal is then sent to the current loop. The output of the current loop controls the thyristor to control the motor. The difference after comparing the feedback value of the current loop is adjusted by PID within the current loop and output to the motor. The output of the current loop is the phase current of each phase of the motor. The feedback of the current loop is not the feedback of the encoder but the feedback of the Hall element installed in each phase inside the driver to the current loop.

[0023] The beneficial effects of the present invention are as follows:

[0024] Combined with the application requirements of ship engineering, the present invention conducts research and analysis on the vibration of the parallel hybrid power system, masters the key technologies of mutual excitation and response matching between the mechanical and electrical systems, and improves the vibration suppression ability of the parallel hybrid power system. The results of this invention can be directly applied to the treatment of the vibration of the parallel hybrid power system during the commissioning process, shortening the troubleshooting time and improving the matching and operation reliability of the mechanical and electrical systems; at the same time, these results can be widely applied to ships with other power propulsion types. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the flowchart of the method for suppressing the vibration of the ship parallel hybrid power system;

[0026] Figure 2 is the schematic diagram of the current loop control of the shaft-driven variable-frequency system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described below in conjunction with the drawings and embodiments.

[0028] As Figure 1 shown, the method for suppressing the vibration of the ship parallel hybrid power system of the present invention includes:

[0029] 1. Formulate an effective vibration control plan

[0030] According to the determined layout diagram, system diagram, shafting layout diagram, propeller diagram, main engine, gearbox, shaft-driven motor system, etc. of the parallel hybrid power system, calculate and study the shafting alignment, shafting rotation, shafting torsional vibration, shafting longitudinal vibration, and flexible matching of the variable-frequency system. Among them:

[0031] 1) Shafting calculation

[0032] Torsional vibration, whirling, longitudinal vibration, and alignment calculation are applicable to various ship types and propulsion types, and are classic theoretical analyses recognized and verified by the industry and classification societies. According to the layout and operating conditions of specific projects, more detailed calculations and studies should be carried out. If the requirements are not met, improvement measures should be taken to ensure that harmful vibrations are avoided within the common rotational speed range and operating conditions.

[0033] 2) The alignment, whirling, torsional vibration, and longitudinal vibration of the shafting are all classic calculation methods that have been maturely applied and recognized by classification societies.

[0034] Shafting alignment is the design and installation process of laying the propeller shaft, tailshaft (if any), intermediate shaft, thrust shaft, and engine shaft (diesel engine or gearbox) into a certain state according to certain requirements and methods, so that the bearing load, or / and additional bending stress of the shaft, or / and the angle of the propeller shaft, etc., are within the allowable range, thus ensuring the safe use of the ship's shafting. Currently, reasonable alignment adopts the transfer matrix method, the three-moment method, and the finite element method. When calculating the shafting alignment, the actual possible different installation ambient temperatures should be taken into account. The shafting alignment calculation report should include: engine type, rated power, rated speed, shafting layout diagram, each concentrated load and its acting position, the position and length of the bearings, the allowable bending moment and shear force at the output flange of the diesel engine, the allowable load of each bearing, bearing clearance, the relative inclination angle between the propeller shaft and the rear bearing of the tailshaft, relevant data of the gearbox, and the allowable load difference between the front and rear bearings of the large gear.

[0035] Shafting whirling is a vibration phenomenon in which the rotating shaft precesses around its static balance curve under the action of a lateral moment rotating on the propeller or rotating shaft of the propulsion shafting. The transfer matrix is used to calculate the shafting whirling vibration. Generally, a simplified model combining lumped elements and distributed parameter elements is used to establish the model to obtain the natural frequency and resonance speed.

[0036] Shafting torsional vibration is a phenomenon in which the ship's shafting undergoes torsional deformation around its longitudinal axis under the excitation of periodic torques such as diesel engines and propeller bearing forces. Currently, the transfer matrix and magnification factor method are mainly used for response calculation. The torsional vibration calculation report should include: engine type, rated power, rated speed, shafting layout diagram, tensile strength of the shaft material, torsional vibration equivalent parameters of the system and necessary explanations, the Holzer table of each section of vibration required, the corresponding relative amplitude vector sum, the vibration response calculation of the main harmonics and the corresponding allowable values. Vibration conditions. Generally, 0.8n min ~1.2ne (n minis the lowest stable speed, r / min) until 12 harmonic vibrations are applied to the diesel engine propulsion shafting. If there are different operating conditions during the use of the device, such as with a clutch, multiple engines in parallel, shaft generator, etc., torsional vibration calculations need to be carried out separately for different operating conditions. In addition to the torsional vibration calculation under normal operating conditions, torsional vibration calculations should also be carried out for the case of cylinder No. 1 misfiring. For a controllable pitch propeller shafting, torsional vibration calculations should be carried out for zero and maximum pitch. When calculating the allowable stress of the shafting torsional vibration, it is based on the basic diameter of the shaft, without considering the influence of stress concentration. That is, for the crankshaft, it is based on the diameter of the crankpin; for the intermediate shaft, it is based on the minimum diameter of the shaft; for the propeller shaft, it is based on the minimum diameter between its rear bearing and the stuffing box of the bulkhead seal.

[0037] Longitudinal vibration of the shafting refers to the periodic motion phenomenon that occurs along the axis direction of the ship's shafting under the excitation of the periodic axial forces of the diesel engine and propeller bearings. The longitudinal vibration response is calculated by the energy method or the dynamic amplification factor method. The longitudinal vibration calculation report should include: engine type, rated power, rated speed, shafting layout diagram, longitudinal vibration equivalent parameters of the system and necessary explanations, Holzer tables for 0-node and 1-node vibrations, as well as the corresponding relative amplitude vectors and, vibration responses of the main harmonics and the corresponding allowable values. Mainly, the longitudinal vibration characteristics of the propulsion shafting of large low-speed two-stroke diesel engines and turbine propulsion shafting need to be calculated for longitudinal vibration.

[0038] 2. Analyze the excitation sources

[0039] 1) Change the natural frequency of the vibrating body. Such as: shaft diameter, bearing spacing, propeller size, number of propeller blades, etc.; 2) Change the excitation source. Such as: change the clearance between the propeller and the hull, shaft alignment, etc.; 3) Increase the damping. Such as: adjust the stiffness of the elastic coupling, design of vibration dampers, etc.

[0040] 3. Vibration criteria

[0041] Main evaluation contents:

[0042] 1) Within the operating speed range of the system, analyze and determine the main excitation forces and their frequencies, and the excitation forces should not exceed the specified values; within the maximum operating speed range of the system, analyze and determine the main vibration frequencies of the vibrating body, and the ratio to the main excitation frequencies should meet the requirements of the specifications.

[0043] 2) The results of the shafting calculation meet the requirements of the specifications and standards.

[0044] Specification requirements for shaft alignment criteria: Under static conditions, all bearings should be under positive load, that is, there should be no bearing lifting-off phenomenon. The bearing load should generally be not less than 20% of the total weight between two adjacent spans. The bearing load should generally not exceed the following specified values or the values specified by the manufacturer: forward bearing of the stern tube: 0.8 N / mm2; stern tube bearing made of non-metallic material: 0.3 N / mm2; intermediate shaft bearing: 0.8 N / mm2; gear shaft bearing: 1 N / mm2; main bearing of the diesel engine: the value specified by the diesel engine manufacturer.

[0045] The additional bending stress of each shaft should generally not exceed the following values: propeller shaft and stern tube shaft: 20 N / mm2; intermediate shaft: 20 N / mm2; thrust shaft: 15 N / mm2; large gear shaft: 10 N / mm2 or the value specified by the gearbox manufacturer.

[0046] The difference in bearing loads between the front and rear bearings of the large gear of the gearbox should meet the relevant regulations of the manufacturer. Generally, it should not exceed 20% of the sum of the weight of the shaft section between the two bearings and the large gear. However, if the calculation results of the shaft alignment under operating conditions are provided and it is confirmed that the bearing structure is determined according to the resultant force action angle under operating conditions, then the difference in the front and rear bearing loads is not limited by 20%, but should meet the relevant requirements of the specification. At the support point of the rear bearing of the stern tube, the relative inclination angle between the propeller shaft and the rear bearing of the stern tube should not exceed 3.0×10-4 rad under static conditions.

[0047] Specification requirements for shaft torsional vibration criteria: For shaft systems with a kingpost or a universal shaft, the sub-critical positive torsional resonance speed should not occur in the range of r=(0.85 - 1.0), and the 1st positive torsional resonance speed should be more than 20% higher than the rated speed.

[0048] Specification requirements for torsional vibration criteria: The vibration torque at the gear meshing point in the gear transmission device should generally not exceed 1 / 3 of the full-load average torque within the rotational speed range of r = 0.9 - 1.05, and no tooth impact phenomenon should occur. For the elastic element of the elastic coupling, the vibration torque during continuous operation should not exceed its allowable alternating torque value; during instantaneous operation, it should not exceed its allowable alternating torque value for instantaneous operation. For the power branch without output load, the vibration torque at the gear meshing point should generally not exceed 20% of the full-load average torque. Within the normal operating speed range of the diesel engine or the special operating speed range, no dangerous resonance speed should occur. Under normal operating conditions, no rotational speed forbidden zone is generally set within the normal operating speed range (r = 0.8 - 1.0). Under the condition of single-engine, single-propeller, and one-cylinder shutdown, the setting principle of the rotational speed forbidden zone should be to ensure the safe navigation of the ship. At r = 0.8, the torsional vibration stress generated by the resonance upper wave slope should not exceed the allowable stress for continuous operation. The allowable torsional vibration stress of the thrust shaft, intermediate shaft, propeller shaft, and stern tube shaft should not exceed the allowable torsional vibration stress for continuous operation. Under rated conditions, the combined amplitude at the rotor of the alternator should not be greater than 3.5° (electrical angle). The vibration inertia torque applied to the rotor of the generator should not exceed ±2Me (Me is the average torque at the rated speed) within the rotational speed range of r = 0.95 - 1.10, and should not exceed ±6Me within the range of r < 0.95. When one main engine drives two or more generators, the rated torque of each generator itself should be considered separately.

[0049] Specification requirements for longitudinal vibration criteria: For the diesel engine propulsion shafting, within the rotational speed range of r = 0 - 1.0, the longitudinal vibration amplitude of the free end of the crankshaft generated by the longitudinal vibration of the shafting should not exceed the specified value: If it exceeds the allowable value for continuous operation, a rotational speed forbidden zone should be set. Generally, at r = 0.85, the longitudinal vibration amplitude generated by resonance or the upper wave slope should not exceed the allowable value for continuous operation, and at r = 1.0, the longitudinal vibration amplitude generated by resonance or the lower wave slope should also not exceed the allowable value for continuous operation.

[0050] 4. Shaft alignment and alignment of elastic couplings

[0051] Alignment should be carried out in accordance with the alignment calculation book approved by the classification society and the compensation for environmental temperature and hot conditions. Generally, after the shafting, gearbox, and main engine alignment inspections are reported, the alignment of the shaft-driven generator is carried out. Note: (When checking the alignment, the axial and radial offsets at the generator end and power output end caused by temperature rise need to be considered, and the offsets should be within the tolerance range of the coupling). After the alignment result is reported, the installation method of the motor base meets the installation requirements of the equipment, and the torque of the foundation bolts meets the requirements.

[0052] 5. Flexible matching of the variable-frequency system of shaft-driven generators

[0053] The main engine governor and the shaft generator frequency converter are the dampers of the "mechanical" and "electrical" systems. When the shaft generator is in the power generation mode, the frequency converter uses torque control, which is also current loop control. Pulse Width Modulation (PWM) is used for speed regulation. When the power generation load changes, if the current loop control is not well matched, it will cause oscillations between the speed fluctuations of the shaft generator and the torsional energy storage of the high-elasticity. If the oscillation is amplified, it is easy to cause overheating and damage of the high-elasticity. The unbalanced torque of the main engine is large, and the control accuracy and response speed of its speed control system are average. Therefore, adjusting the damping parameters (PID) of the shaft generator frequency converter and suppressing system instability through flexible matching is an effective means.

[0054] As Figure 2 shown, the PID constants of the current loop are generally set inside the frequency converter drive. The speed loop mainly performs PI (Proportional and Integral). The proportion is the gain. Appropriate adjustment of the speed gain and the speed integral time constant is required to achieve the ideal effect. When the external load fluctuates greatly, the original stable DC system undergoes resonant oscillation and becomes unstable, and the DC voltage and DC current oscillate and diverge. After the damping control is put into operation, the unstable DC system gradually returns to stable operation. The presetting of the P, I, and D parameters complements each other. The following fine-tuning should be carried out according to the actual situation at the operation site: If the controlled physical quantity oscillates near the target value, first increase the integral time I. If there is still oscillation, the proportional gain P can be appropriately reduced. If the controlled physical quantity is difficult to recover after a change, first increase the proportional gain P. If the recovery is still slow, the integral time I can be appropriately reduced, and the derivative time D can also be increased.

Claims

1. A vibration suppression method for a ship parallel hybrid power system, characterized in that, it includes: 1) Analyze and determine the system vibration source Calculate and analyze various excitation forces that may cause vibration of the parallel hybrid power system, compare them with the natural frequency of the vibrating body, and gradually eliminate the possibility of resonance; 2) Analyze the excitation source Change the natural frequency of the vibrating body, change the excitation source, and increase the damping; 3) Vibration criterion Within the operating speed range of the system, analyze and determine the main excitation forces and their frequencies, and the excitation forces should not exceed the specified values; within the maximum operating speed range of the system, analyze and determine the main vibration frequencies of the vibrating body, and the ratio to the main excitation frequency should meet the requirements of the specification, and the results of the shafting calculation meet the requirements of the specification and standards; 4) Shafting alignment and elastic coupling alignment Perform alignment according to the alignment calculation book approved by the classification society and the compensation for ambient temperature and hot conditions. After the shafting, gearbox, and main engine alignment are inspected and approved, perform the alignment of the shaft generator. After the alignment result is inspected and approved, the installation method of the motor base meets the installation requirements of the equipment, and the torque of the foundation bolts meets the requirements; 5) Flexible matching of the shaft generator variable frequency system When the power generation load changes, if the current loop control is not well matched, it will cause oscillations between the speed fluctuations of the shaft generator and the torsional energy storage of the high-elasticity, and if the oscillation is amplified, it is easy to cause the high-elasticity to heat and damage; when the unbalanced torque of the main engine is large and the control accuracy and response speed of its speed control system are not high, adjust the damping parameters of the shaft generator frequency converter to suppress the instability of the system through flexible matching; The flexible matching of the shaft generator variable frequency system also includes the adjustment and matching of the frequency converter damping: Any mode of the frequency converter uses the current loop, and while the system performs speed and position control, it performs current / torque control to achieve the corresponding control of speed and position. Among them, a required speed signal is given, and the feedback speed signal is subtracted, and this difference is sent to the speed loop of the speed governor. The difference between the output of the speed loop and the current detection feedback signal is sent to the current loop again. The output of the current loop controls the thyristor to control the motor. The difference after the comparison of the feedback value of the current loop is subjected to PID adjustment in the current loop and output to the motor. The output of the current loop is the phase current of each phase of the motor. The feedback of the current loop is not the feedback of the encoder but the feedback of the Hall element installed in each phase inside the driver to the current loop.

2. The vibration suppression method for a ship parallel hybrid power system according to claim 1, characterized in that: Changing the natural frequency of the vibrating body includes changing the shaft diameter, bearing spacing, propeller size, and number of propeller blades.

3. The vibration suppression method for a ship parallel hybrid power system according to claim 1, characterized in that: Changing the excitation source includes changing the clearance between the propeller and the hull and shafting alignment.

4. The vibration suppression method for a ship parallel hybrid power system according to claim 1, characterized in that: Increasing the damping includes adjusting the stiffness of the elastic coupling and the size and performance of the shock absorber.

5. The vibration suppression method for a ship parallel hybrid power system according to claim 1, characterized in that: The method also includes vibration monitoring: When the shaft generator starts to operate initially, closely monitor the motor, the motor coupling and the main engine status. First, run it without load and then gradually and slowly load it. During this period, measure the temperature of the coupling rubber parts and the vibration displacement. In case of any abnormality, stop the machine immediately. Under each working condition, check the temperature of the frequency converter, the temperature of the motor bearings and windings, the current / voltage / frequency of the motor and the frequency converter, the vibration and abnormal noises.

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