Ship electric propulsion system, ship and control method

Abstract

The present invention discloses a ship electric propulsion system, a ship and a control method, and the present invention relates to the technical field of ship electric coordinated control. The ship electric propulsion system includes a propulsion motor, a propeller, a generator circuit breaker, a main transmission shaft, and a load distribution board, wherein the propulsion motor is connected to the propeller through the main transmission shaft, and the propulsion motor drive is connected to a steam turbine generator set, the steam turbine generator set is electrically connected to a steam turbine control system, and the steam turbine generator set module is connected to the distribution board through a generator circuit breaker switch. The propulsion motor power source is realized based on the distribution board, and the steam turbine generator set is incorporated into the ship's power grid. The present invention solves the severe disturbance caused to the steam generator set when the complex working conditions of the electric propulsion ship are switched, and can make the large delay system of the one-circuit run smoothly, ensure the safety of the power source, make the speed fluctuation of the steam generator set under isolated grid operation within the allowable range, and ensure the safe operation of the ship's AC electrical appliances.

Description

Technical Field

[0001] The present invention relates to the technical field of ship electric power coordinated control, and in particular to a ship electric propulsion system, a ship and a control method. Background Art

[0002] Electric propulsion ships are driven entirely by electricity, with the power coming entirely from the ship's turbine generator set, which then propels the propeller through an electric motor. This pure electric drive offers numerous advantages, including high starting torque, fast starting speed, flexible propulsion mechanism layout, high efficiency, and quiet operation. However, a disadvantage is that the ship's turbine generator set cannot be connected to the main power grid. The variable operating conditions of the propulsion motor significantly impact the load torque of the turbine set, making stable frequency operation crucial for smooth operation. The frequency of the turbine set directly affects the frequency of the AC power output by the generator. If the power frequency exceeds the specified limit, all AC-consuming equipment will malfunction or even be damaged.

[0003] In addition, the power level of ship AC loads is low and the load fluctuation is small, which has almost no impact on the ship's power grid; while the propulsion motor is a high-power electrical equipment. With the different working conditions of the ship (rapid acceleration, escape, etc.), the power of the propulsion motor changes dramatically and frequently, bringing huge load fluctuations to the ship's power grid.

[0004] Because the steam turbine generator set is the sole generator on the power grid, and its capacity is comparable to that of the propulsion motor, the kinetic energy and thermal potential energy stored in the turbine's rotational inertia are relatively small. Severe fluctuations in the grid load directly impact the turbine generator set by causing dramatic changes in the unit's speed, or frequency. These frequency fluctuations can cause turbine damage, generator failure, and excitation equipment malfunction, leading to unstable grid voltage and ultimately causing a ship-wide power outage or electrical damage, endangering the safety of all personnel and equipment.

[0005] Existing technology sets the steam turbine generator set to frequency regulation operation mode. In this mode, all load changes in the isolated grid are absorbed by the frequency regulation unit. The frequency setting value is a fixed value (50Hz). As the load fluctuates, the unit frequency will fluctuate around this set value. The advantage of this mode is that the isolated grid frequency can be controlled during small load disturbances, the power supply quality is high, and it is conducive to the healthy operation of the steam turbine generator set.

[0006] However, due to the physical limitations of the mechanical components of the steam distribution mechanism, even when operating in frequency modulation mode, it is impossible to ensure that the speed (frequency) of the frequency-regulated unit remains stable near the rated value during large load fluctuations. Even with DC power distribution (some ship power stations use DC power generation, which has the advantage that changes in unit frequency do not affect the grid frequency), drastic changes in the unit's frequency will affect the unit's health, potentially causing failure and damage to the power generation equipment. The excitation system's voltage regulation capability can only regulate within a limited unit frequency range. Because the steam generator has high inertia, it cannot instantly provide sufficient quality power steam during large load fluctuations, affecting the safe operation of the unit itself and easily causing failure or shutdown of the steam generator. Therefore, the coordinated control of traditional steam turbine generator sets matching loads has unavoidable shortcomings. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides a ship electric propulsion system, a ship and a control method, which solve the problems raised in the above background technology.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions: a ship electric propulsion system, a ship and a control method, wherein the propulsion system includes a propulsion motor, a propeller, a generator circuit breaker, a main drive shaft, and a load distribution board, wherein the propulsion motor is connected to the propeller through the main drive shaft, and the propulsion motor drive is connected to a steam turbine generator set, the steam turbine generator set is electrically connected to a steam turbine control system, and the steam turbine generator set module is connected to the distribution board through a generator circuit breaker switch, the power source of the propulsion motor is realized based on the distribution board, and the steam turbine generator set is incorporated into the ship's power grid.

[0009] A further improvement of the technical solution of the present invention is that: the control mode of the steam turbine generator set adopts a speed PID closed-loop strategy, and the output current I of the steam turbine generator set is determined based on the input signal of the propulsion system.

[0010] A further improvement of the technical solution of the present invention is that the working current I ’ Real-time tracking of the output current of the steam turbine generator set is the feedback signal of the propulsion system.

[0011] A further improvement of the technical solution of the present invention is to provide a control method for a ship electric propulsion system, comprising the following specific steps:

[0012] S1: Introducing the power signal of the steam turbine and connecting the steam turbine generator set to the ship's power grid. The propulsion system quickly generates propulsion power. After balancing the power in the steam turbine, the power model is used to calculate the power in the steam turbine at this time.

[0013] S2: Calculate the steam turbine power according to the instrument measurement to obtain the shaft end output torque of the steam turbine in the steam turbine generator set;

[0014] S3: The output torque at the control shaft end is the same as the electromagnetic torque T, and the available current I generated by the generator in the steam turbine generator set and the working current I required by the propulsion motor in the ship propulsion system are obtained. ’ ; Thus completing the working current I of the propulsion motor ’ Real-time tracking of steam turbine generator output current I and operating current I ’作为 Feedback signals from the propulsion system;

[0015] S4: The speed PID control is mainly used in the end. The speed is 50Hz, that is, the speed of the steam turbine unit is 3000 rpm. The given speed is a fixed value of 3000 rpm. When the actual speed of the steam turbine is greater than 3000 rpm, the steam inlet regulating valve is closed. When the actual speed of the steam turbine is less than 3000 rpm, the steam inlet regulating valve is opened to balance the power of the generator and the propulsion motor.

[0016] Furthermore, because the given speed remains unchanged, the active power generated by the steam turbine generator set is not restricted by the electrical load and is only related to the air intake of the turbine. Therefore, in order to ensure that the steam turbine generator set can better track the given speed of 3000 rpm, it is necessary to balance the power of the generator and the propulsion motor. The generator stator winding current is used as the given value of the second closed-loop PID in the schematic diagram, and the stator current of the propulsion motor is used as the feedback value of the closed loop. In this way, the propulsion motor electric power can be matched with the generator electric power by changing the propulsion motor current in real time. This method can make the marine isolated grid AC generator set always maintain stable operation near 3000 rpm like the grid-connected unit. The speed control loop adjustment process is gentle, and the power adjustment is handed over to the propulsion motor.

[0017] Therefore, this control strategy in which the ship's propulsion system follows the operation of the steam turbine generator set solves the problem of severe disturbances to the steam turbine generator set caused by switching between complex working conditions of electric propulsion ships. It can make the large-delay system of a single circuit run smoothly, ensure the safety of the power source, and make the speed fluctuation of the steam turbine generator set under isolated grid operation within the allowable range, thereby ensuring the safe operation of the ship's AC electrical appliances.

[0018] A further improvement of the technical solution of the present invention is that the power model in S1 is specifically:

[0019] Ne=D×Hs×ηe / 3600=G×Hs×ηe=M×ω=2π×M×ns;

[0020] Where Ne is the turbine effective power, D is the through steam flow rate, Hs is the adiabatic enthalpy drop, G is the through steam flow rate, ηe is the effective efficiency of the turbine, M is the turbine shaft end torque, ω is the turbine rotor angular velocity, and ns is the turbine rotor speed.

[0021] A further improvement of the technical solution of the present invention is that the instrument measurement in S2 includes the following specific values: the instantaneous steam flow entering the turbine, the instantaneous adiabatic enthalpy drop and the turbine efficiency curve, among which the shaft end output torque of the turbine in the steam turbine generator set is completed according to M=Ne / ω.

[0022] A further improvement of the technical solution of the present invention is that: the electromagnetic torque T in S3 is T = k × B × I × A × sin (θ), where T is the electromagnetic torque, K is the proportional coefficient, B is the magnetic field strength, I is the current of the energized coil, A is the cross-sectional area of ​​the coil, and θ is the angle between the coil axis and the magnetic field axis, where the output torque at the control shaft end is the same as the electromagnetic torque T, that is, M = T.

[0023] A further improvement of the technical solution of the present invention is that a ship is also provided, wherein the ship uses the ship electric propulsion system according to any one of claims 1 to 3 to achieve stable frequency operation.

[0024] Compared with the existing technology, the present invention has the following beneficial effects: the ship electric propulsion system, ship and control method solve the severe disturbance to the steam generator set caused by the switching of complex working conditions of the electric propulsion ship, can make the large delay system of one circuit run smoothly, ensure the safety of the power source, make the speed fluctuation of the steam generator set under isolated grid operation within the allowable range, and ensure the safe operation of the ship's AC electrical appliances. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the schematic diagram of the electric propulsion system control of this ship;

[0026] Figure 2 This is a graph showing the speed and adjustment time of the ship's electric propulsion system.

[0027] Figure 3 This is a schematic diagram of the isolated network frequency when the frequency regulating unit in the ship's electric propulsion system is in an isolated network state;

[0028] Figure 4 Schematic diagram of the control method of the ship electric propulsion system. DETAILED DESCRIPTION

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] The present invention provides a ship electric propulsion system, which includes a propulsion motor, a propeller, a generator circuit breaker, a main drive shaft, and a load distribution board, wherein the propulsion motor is connected to the propeller through the main drive shaft, and the propulsion motor is driven and connected to a steam turbine generator set, the steam turbine generator set is electrically connected to a steam turbine control system, and the steam turbine generator set module is connected to the distribution board through a generator circuit breaker switch, the power source of the propulsion motor is realized based on the distribution board, and the steam turbine generator set is incorporated into the ship's power grid.

[0031] The steam turbine generator set control method adopts a speed PID closed-loop strategy, and the output current I of the steam turbine generator set is determined based on the input signal of the propulsion system.

[0032] The operating current I of the propulsion motor ’ Real-time tracking of the output current of the steam turbine generator set is the feedback signal of the propulsion system.

[0033] The present invention also provides a control method for a ship electric propulsion system, comprising: step S1: introducing a power signal in a steam turbine and integrating a steam turbine generator set into a ship power grid, so that the propulsion system quickly generates propulsion power, balances the power in the steam turbine, and calculates the power in the steam turbine at this time using a power model;

[0034] S2: Calculate the steam turbine power according to the instrument measurement to obtain the shaft end output torque of the steam turbine in the steam turbine generator set;

[0035] S3: The output torque at the control shaft end is the same as the electromagnetic torque T, and the available current I generated by the generator in the steam turbine generator set and the working current I required by the propulsion motor in the ship propulsion system are obtained. ’ ; Thus completing the working current I of the propulsion motor ’ Real-time tracking of steam turbine generator output current I and operating current I ’作为 Feedback signals from the propulsion system;

[0036] S4: The speed PID control is mainly used in the end. The speed is 50Hz, that is, the speed of the steam turbine unit is 3000 rpm. The given speed is a fixed value of 3000 rpm. When the actual speed of the steam turbine is greater than 3000 rpm, the steam inlet regulating valve is closed. When the actual speed of the steam turbine is less than 3000 rpm, the steam inlet regulating valve is opened to balance the power of the generator and the propulsion motor.

[0037] Furthermore, because the given speed remains unchanged, the active power generated by the steam turbine generator set is not restricted by the electrical load and is only related to the air intake of the turbine. Therefore, in order to ensure that the steam turbine generator set can better track the given speed of 3000 rpm, it is necessary to balance the power of the generator and the propulsion motor. The generator stator winding current is used as the given value of the second closed-loop PID in the schematic diagram, and the stator current of the propulsion motor is used as the feedback value of the closed loop. In this way, the propulsion motor electric power can be matched with the generator electric power by changing the propulsion motor current in real time. This method can make the marine isolated grid AC generator set always maintain stable operation near 3000 rpm like the grid-connected unit. The speed control loop adjustment process is gentle, and the power adjustment is handed over to the propulsion motor.

[0038] Therefore, this control strategy in which the ship's propulsion system follows the operation of the steam turbine generator set solves the problem of severe disturbances to the steam turbine generator set caused by switching between complex working conditions of electric propulsion ships. It can make the large-delay system of a single circuit run smoothly, ensure the safety of the power source, and make the speed fluctuation of the steam turbine generator set under isolated grid operation within the allowable range, thereby ensuring the safe operation of the ship's AC electrical appliances.

[0039] The power model in S1 is specifically:

[0040] Ne=D×Hs×ηe / 3600=G×Hs×ηe=M×ω=2π×M×ns;

[0041] Where Ne is the turbine effective power, D is the through steam flow rate, Hs is the adiabatic enthalpy drop, G is the through steam flow rate, ηe is the effective efficiency of the turbine, M is the turbine shaft end torque, ω is the turbine rotor angular velocity, and ns is the turbine rotor speed.

[0042] The instrument measurements in S3 include the following specific values: instantaneous steam flow entering the turbine, instantaneous adiabatic enthalpy drop and turbine efficiency curve, wherein the shaft end output torque of the turbine in the steam turbine generator set is completed according to M=Ne / ω.

[0043] In S3, the electromagnetic torque T = k × B × I × A × sin (θ), where T is the electromagnetic torque, K is the proportional coefficient, B is the magnetic field strength, I is the current of the energized coil, A is the cross-sectional area of ​​the coil, and θ is the angle between the coil axis and the magnetic field axis. The output torque at the control shaft end is the same as the electromagnetic torque T, that is, M = T.

[0044] The present invention also provides a ship, which uses the ship electric propulsion system according to any one of claims 1 to 3 to achieve stable frequency operation.

[0045] At the same time, the contents not described in detail in this specification belong to the existing technology known to those skilled in the art, and the model parameters of each electrical appliance are not specifically limited, and conventional equipment can be used.

[0046] During operation, the turbine is primarily controlled by speed PID control. The set speed is fixed at 3000 rpm, using a 50Hz system. When the actual turbine speed exceeds 3000 rpm, the steam inlet control valve is closed; when the actual turbine speed is less than 3000 rpm, the valve is opened. Because the set speed remains constant, the active power generated by the turbine generator set is not constrained by the electrical load but only by the air intake. Therefore, to ensure the turbine generator set can optimally track the set speed of 3000 rpm, it is necessary to balance the generator and propulsion motor power. The generator stator winding current is used as the set value for the second closed-loop PID control in the schematic diagram, and the propulsion motor stator current is used as the feedback value for this closed-loop. This allows the propulsion motor power to be matched to the generator power by varying the propulsion motor current in real time.

[0047] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A control method for a ship electric propulsion system, applied to a ship electric propulsion system, wherein the propulsion system comprises a propulsion motor, a propeller, a generator circuit breaker, a main transmission shaft, a load distribution board, and a steam turbine generator set, wherein the propulsion motor is connected to the propeller via the main transmission shaft, and the steam turbine generator set is electrically connected to a steam turbine control system, characterized in that: The specific steps include: S1: Introducing the power signal of the steam turbine and connecting the steam turbine generator set to the ship's power grid. The propulsion system quickly generates propulsion power. After balancing the power in the steam turbine, the power model is used to calculate the power in the steam turbine at this time. S2: Calculate the steam turbine power according to the instrument measurement to obtain the shaft end output torque of the steam turbine in the steam turbine generator set; S3: The output torque at the control shaft end is the same as the electromagnetic torque T, and the available current I generated by the generator in the steam turbine generator set and the working current I required by the propulsion motor in the ship propulsion system are obtained. ’ ; Thus completing the working current I of the propulsion motor ’ Real-time tracking of steam turbine generator output current I and operating current I ’ As a feedback signal to the propulsion system; S4: The speed PID control is mainly used in the end. The speed is 50Hz, that is, the speed of the steam turbine unit is 3000 rpm. The given speed is a fixed value of 3000 rpm. When the actual speed of the steam turbine is greater than 3000 rpm, the steam inlet regulating valve is closed. When the actual speed of the steam turbine is less than 3000 rpm, the steam inlet regulating valve is opened to balance the power of the generator and the propulsion motor.

2. A control method for a ship electric propulsion system according to claim 1, wherein the steam turbine generator set is connected to a distribution board via a generator circuit breaker switch, the propulsion motor power source is realized based on the distribution board, and the steam turbine generator set is incorporated into the ship power grid.

3. The control method of a ship electric propulsion system according to claim 1, characterized in that: The power model in S1 is specifically: Ne=D×Hs×ηe / 3600=G×Hs×ηe=M×ω=2π×M×ns; in Ne is the turbine effective power, D is the through-flow steam flow rate, Hs is the adiabatic enthalpy drop, G is the through-flow steam flow rate, ηe is the effective efficiency of the turbine, M is the turbine shaft end torque, ω is the turbine rotor angular velocity, and ns is the turbine rotor speed.

4. The control method of a ship electric propulsion system according to claim 3, characterized in that: The instrument measurements in S3 include the following specific values: instantaneous steam flow entering the turbine, instantaneous adiabatic enthalpy drop and turbine efficiency, among which the shaft end output torque of the turbine in the steam turbine generator set is completed according to M=Ne / ω.

5. The control method of a ship electric propulsion system according to claim 1, characterized in that: In S3, the electromagnetic torque T=k×B×I×A×sin(θ), where T is the electromagnetic torque, K is the proportional coefficient, B is the magnetic field strength, I is the current of the energized coil, A is the cross-sectional area of ​​the coil, and θ is the angle between the coil axis and the magnetic field axis. The output torque at the control shaft end is the same as the electromagnetic torque T, that is, M=T.

6. A ship comprising a ship electric propulsion system, characterized in that: The system adopts the control method of the ship electric propulsion system as described in any one of claims 1 to 5 to achieve stable frequency operation.

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