Method for optimally distributing power load of each generator of electric propulsion ship

Abstract

The invention belongs to the technical field of ship oil consumption rate optimization, and particularly relates to a method for optimally distributing power loads of all generators of an electric propulsion ship. The method comprises the steps that setting is conducted according to various working conditions of the electric propulsion ship, loads under the various working conditions are calculated, and the power and the number of main generator sets of a power station corresponding to the electric propulsion ship are designed according to the calculated loads; designing a multi-stage auxiliary generator set according to the ship power station power value and the rated power value of the main generator set; a storage battery pack is installed on the electric propulsion ship corresponding to the ship power station; and obtaining an optimal solution of economic load distribution of the power grid by adopting an enumeration method based on the optimal working condition that the ratio of the active power load to the rated power of each generator set in the grid generator set is the same. According to the method provided by the invention, the difference value between each gear of each optimal working condition is not large due to the difference of the input number of generator sets of the ship power station, and the operation efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship fuel consumption rate optimization, and in particular relates to a method for optimizing the power load distribution of each generator of an electric propulsion ship. Background Art

[0002] Electric propulsion ships use multiple generators to power the main propulsion motors and other electrical loads. This arrangement allows for high system efficiency by increasing or decreasing the number of generators when external loads fluctuate significantly. Optimizing energy allocation in electric propulsion ships typically requires consideration of the following key aspects: First, on the power supply side, the load distribution among the generator sets should be optimized for a given power output to achieve optimal system efficiency. This is the problem of economic load dispatching (ELD). On the power consumption side, optimizing the energy distribution of the electric propulsion system is crucial. Electric propulsion systems typically include the main propulsion system, auxiliary equipment, and power management systems. Precisely controlling the power distribution among these components can ensure that navigation requirements are met while reducing unnecessary energy consumption. For example, adjusting the power output of the main propulsion system based on navigation speed and load can keep the generator sets operating at their optimal efficiency point. Secondly, optimizing the energy distribution of auxiliary equipment is also crucial. Auxiliary equipment includes lighting, air conditioning, and navigation equipment. Although these equipment consume relatively little energy, proper distribution can still help improve overall energy efficiency. For example, when sailing at night, the brightness of lighting equipment can be appropriately lowered to reduce energy consumption; when the temperature is suitable, the settings of the air-conditioning system can be adjusted to avoid excessive cooling or heating.

[0003] Intelligent and automated power management systems are also crucial for optimizing energy consumption. By incorporating advanced power management systems and algorithms, a ship's energy consumption can be monitored in real time, with automatic adjustments and optimizations tailored to actual conditions. For example, based on the ship's navigation status and energy needs, the power management system can automatically adjust power distribution to various devices and systems to achieve optimal energy efficiency.

[0004] While much research has been conducted on optimizing power supply management, most efforts focus on batteries as the primary power source, supplemented by solar power and other sources. This differs from the situation for electric-powered ships, which rely on generators. The large number of batteries in these power sources creates difficulties in optimizing the power supply. These studies have all been implemented using various intelligent optimization algorithms.

[0005] Currently, all research on power plant economic load allocation utilizes intelligent optimization algorithms. These algorithms are essential for large land power grids and power sources composed of a large number of batteries, but are not necessary for marine power plants consisting of several generator sets with identical main generators. Intelligent algorithms are statistically based numerical solutions, which require significant computing power and are computationally complex. Their results are sensitive to input conditions and may result in localized extreme solutions, making them inferior to analytical solutions. In existing marine electric propulsion systems, if these solutions are used, the optimal solution under different conditions will frequently change, making it difficult for engineers to continuously adjust generator operation accordingly. In new marine electric propulsion systems, if only the capacity of each generator set in the power plant is considered under different conditions, without considering optimization analysis for different scenarios at the outset of the design, subsequent management and operation will often result in actual operating conditions not being optimal for the system. Summary of the Invention

[0006] The present invention solves the problem that the engines of existing electric propulsion ships cannot operate under optimal working conditions under actual working conditions, and provides a method for optimizing the power load distribution of each generator of an electric propulsion ship. When the generator sets on the grid are determined, the distribution of active power of each generator set should make the ratio of the load of each generator set to the rated power of the generator set the same as the optimal working condition.

[0007] The technical solutions claimed in the present invention are as follows:

[0008] A method for optimizing the power load distribution of each generator of an electric propulsion ship comprises the following steps:

[0009] S1: setting various operating conditions of the electric propulsion ship, calculating the load of the electric propulsion ship under various operating conditions, and designing the power and number of main generator sets of the ship power station corresponding to the electric propulsion ship according to the calculated load;

[0010] S2: Design multiple auxiliary generator sets based on the power plant power value and the rated power value of the main generator set; the rated power of the first-level auxiliary generator set is half of the rated power of the main generator set, the rated power of the second-level auxiliary generator set is half of the rated power of the first-level auxiliary generator set, and so on;

[0011] S3: Install battery packs in the ship power station corresponding to the electric propulsion ship;

[0012] S4: Based on the fact that the ratio of the active power load of each generator set on the grid to its rated power is the optimal working condition, and then according to the characteristic that the number of generators in the ship power station is small, the enumeration method is used to obtain the optimal solution for the economic load distribution of the power grid, and the main engine, auxiliary engines at all levels and batteries are opened according to the optimal solution.

[0013] In a specific embodiment of the present invention, the load in S1 includes continuous load and intermittent load.

[0014] Preferably, the multi-stage auxiliary generator set in S2 is connected to the main engine in parallel; the ship power station is provided with an emergency generator set; the multi-stage auxiliary generator set and the emergency generator set are of the same model; the auxiliary generator set does not exceed two levels.

[0015] Preferably, the charging and discharging power of the battery pack in S3 is half or more of the power of the auxiliary generator set with the smallest rated power, and the charging and discharging can be adjusted according to the power grid.

[0016] In some embodiments of the present invention, the battery pack capacity described in S3 is the difference between the maximum and minimum power of the power grid during navigation multiplied by the interval time; in other embodiments of the present invention, the battery pack capacity described in S3 is determined based on the optimized operation of the intermittent working equipment under various working conditions.

[0017] Specifically, when the electric propulsion ship is operating at sea, in order to achieve the optimal operating condition in S4, the operation and load distribution of each generator set are as follows:

[0018] (1) Record the minimum and maximum power values within one hour;

[0019] (2) Each generator set shall not operate at over-rated load. If the maximum power value exceeds the total rated load of the generator sets on the grid, the total rated power value of the grid shall be increased. The method of increasing the power is as follows: if the auxiliary generator set is not running, an additional auxiliary generator set shall be started; if the auxiliary generator set is running, a main generator set shall be started and the auxiliary generator set shall be stopped. If the maximum power value exceeds the total rated power of the grid, an alarm shall be issued and the ship shall be advised to slow down.

[0020] (3) All generator sets are not overloaded; if the maximum power is less than the total rated power of the generator sets on the grid minus half the power of a single main generator set, the total rated power of the generators on the grid is reduced; the reduction method is: if the auxiliary generator set is on the grid, the auxiliary generator set is de-energized; if the auxiliary generator set is not on the grid, an additional auxiliary generator set is added and then one main generator set is de-energized;

[0021] (4) When the power grid is at its minimum power, the battery pack is charged to increase the power grid load and reduce the engine fuel consumption rate; when the power grid is at its maximum power, the battery charging is stopped.

[0022] Preferably, the minimum and maximum power values in step (1) do not include the power required for charging the battery.

[0023] Preferably, the battery is used to directly power communication and navigation equipment and other weak-current equipment; the order of power supply of the battery is: weak-current equipment, electric compass, and navigation aids.

[0024] Preferably, the allocation method is applicable to the design of economic load distribution of ship power stations of electric propulsion ships, and is also applicable to the design of all ship power stations, and is also applicable to the economic load distribution design of small land power stations.

[0025] Beneficial effects:

[0026] The present invention provides a method for optimizing the power load distribution of each generator of an electric propulsion ship. The method is based on the fact that the ratio of the active power load of each generator set on the grid to its rated power is the same as its optimal working condition. Then, based on the characteristic that the number of generators in the ship power station is small, an enumeration method is adopted to obtain the optimal solution for the economic load distribution of the power grid. The ship power station corresponding to the electric propulsion ship is composed of multiple generator sets. Due to the different numbers of generator sets put into use in the ship power station, the optimal working conditions are arranged in a hierarchical manner, not a continuously distributed value. The power of the main generator set is very large, resulting in an excessively large difference between the optimal values of each gear. Some working conditions prevent the ship power station from operating under the most economical condition. By setting up an auxiliary generator set, the difference between the optimal values of each gear can be reduced by half. The number of auxiliary generator sets can be selected according to the design power value of the power grid and the power value of the main generator sets. When the power grid load is between the optimal working conditions of different combinations of the number of main generator sets, the working conditions of each generator set can be optimized by opening multiple auxiliary generator sets. In this way, the difference between each gear of the optimal working conditions will not be so large due to the different number of generator sets put into use in the ship power station, so as to adapt to these working conditions, improve operational efficiency, and solve the problem that the engines of existing electric propulsion ships cannot work under the optimal working conditions under actual working conditions.

[0027] The multi-stage auxiliary generator set and the emergency generator set are of the same model, reducing the number of spare parts on board. The battery pack's charge and discharge power is half or more of the power of the auxiliary generator set with the lowest rated power. By charging and discharging the energy storage battery, the grid power can be matched with the most economical load of the ship's power station.

[0028] By installing batteries and scheduling the working hours of intermittent working equipment, the grid load can be kept at the most economical load of the on-grid generator sets for a long time, further improving operational efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a flow chart of a method for optimizing power load distribution of each generator of an electric propulsion ship according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings.

[0031] The present invention provides a method for optimizing the power load distribution of each generator of an electric propulsion ship, such as Figure 1 As shown, the following steps are included:

[0032] S1: Setting various working conditions of the electric propulsion ship, calculating the load of the electric propulsion ship under various working conditions, and designing the power and number of main generator sets of the ship power station corresponding to the electric propulsion ship according to the calculated load; the load can be continuous load or intermittent load.

[0033] S2: Based on the power value of the ship's power station and the rated power value of the main generator set, a multi-stage auxiliary generator set is designed; the rated power of the first-stage auxiliary generator set is half of the rated power of the main generator set, the rated power of the second-stage auxiliary generator set is half of the first-stage auxiliary generator set, and so on; in a specific embodiment of the present invention, the number of stages is determined according to the power size of the main generator set. The ship's power station is equipped with an emergency generator set; if possible, the engine of the auxiliary generator set is preferably the same model as the ship's emergency generator set, which can reduce the number of spare parts on the ship; the emergency generator is a small generator with a power far less than the main engine, and serves an emergency function similar to the emergency power supply. The application scenario of this generator is extreme. When all conventional generators on the ship fail, the main engine is activated by the emergency generator.

[0034] In a specific embodiment of the present invention, it is recommended that the number of auxiliary generator sets does not exceed two.

[0035] In a specific embodiment of the present invention, the ship power station corresponding to an electric propulsion vessel is composed of multiple generator sets. Each combination of generator sets connected to the grid has an output power value with an optimal fuel consumption ratio. When operating at this power, the fuel consumption ratio per unit output power of the grid is minimized. Because this power value corresponds to a specific combination, the system's optimal output power is a stepped distribution value, not a continuous distribution. This means that the system's optimal output power cannot be designed to be smaller under various operating conditions, with smaller differences between each stage. However, the smaller the power of a single generator set, the more generator sets are required. The optimal output power value for fuel consumption must be determined based on the ship size and grid load. When the grid load is between the optimal operating conditions for different combinations of main generator sets, the operating conditions of each generator set can be optimized by adding additional generator sets. If the power of the main generator set is too high, it is possible to install a second stage of auxiliary generator sets in addition to the first stage, and so on. Multiple stages of auxiliary generator sets can be designed based on the power value of the ship power station and the rated power of the main generator sets. In this way, the difference between each gear of the optimal operating conditions will not be so large due to the different number of generator sets put into use in the ship power station, so as to adapt to these operating conditions.

[0036] S3: A battery pack with a charge and discharge power of half or more than the rated power of the auxiliary generator set with the lowest power is installed in the corresponding ship power station of the electric propulsion ship; the charge and discharge power of the battery pack can be adjusted according to the power grid; in some embodiments of the present invention, the capacity of the battery pack is the difference between the maximum and minimum power of the power grid during navigation multiplied by the interval time; in other embodiments of the present invention, the capacity of the battery is determined based on the optimized operation of intermittent working equipment under various working conditions; for example, the ship's air compressor and ship's auxiliary boiler are intermittently operated, and their operating range is adjustable. Taking the air compressor as an example, the operating range of the air compressor can be set between 20-30 bar, or between 25-30 bar. The capacity of the energy storage battery is determined based on the general operating time of the intermittent working equipment (taking the air compressor as an example, its operating time depends on the use of the ship's air system and the system leakage).

[0037] In a specific embodiment of the present invention, the battery directly powers the communication and navigation equipment and other weak-current equipment. Depending on the capacity of the battery, if the battery capacity is large, while meeting the power supply needs of the weak-current equipment, it can also power the gyrocompass through an inverter or directly use a gyrocompass with a DC motor. If there is any capacity left, it can also power the navigation aids.

[0038] S4: Based on the fact that the ratio of active power load to rated power of each generator set on the grid is the same as its optimal working condition, and taking into account the small number of generators in the ship power station, an enumeration method is used to obtain the optimal solution for the economic load distribution of the power grid. The main engine, auxiliary engines at all levels and batteries are then installed according to the optimal solution.

[0039] In a specific embodiment of the present invention, when the ship power station management system provides the operating conditions of the sea voyage, in order to achieve the optimal operating conditions, the power grid management system controls the operation and load distribution of each generator set according to the following algorithm:

[0040] (1) Record the minimum and maximum power values within one hour. Note: This power value does not include the power required for battery charging.

[0041] (2) Each generator set must not operate at over-rated load. If the maximum power value exceeds the total rated load of the generator sets on the grid, the total rated power value of the grid shall be increased; the method of increasing the power is as follows: if the auxiliary generator set is not running, add an auxiliary generator set. If the auxiliary generator set is running, start a main generator set and stop the auxiliary generator set. If the maximum power value exceeds the total rated power of the grid, an alarm shall be issued and the ship shall be advised to slow down.

[0042] (3) Each generator set is not overloaded; if the maximum power is less than the total rated power of the generator sets on the grid minus half the power of a single main generator set, the total rated power of the generator sets on the grid should be reduced. The method of reduction is to de-energize the auxiliary generator sets if they are on the grid; if the auxiliary generator sets are not on the grid, add an auxiliary generator set and then de-energize one main generator set.

[0043] (4) When the power grid is at its minimum, the battery pack is charged to increase the grid load and reduce the engine fuel consumption rate. When the power grid is at its maximum, the battery charging is stopped.

[0044] In a specific embodiment of the present invention, the method provided by the present invention is not only applicable to the design of economic load distribution of ship power stations of electric propulsion ships, but also to the design of all ship power stations. At the same time, it is also applicable to the economic load distribution design of small land power stations.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for optimizing the power load distribution of each generator of an electric propulsion ship, characterized in that: The steps include: S1: setting various operating conditions of the electric propulsion ship, calculating the load of the electric propulsion ship under various operating conditions, and designing the power and number of main generator sets of the ship power station corresponding to the electric propulsion ship according to the calculated load; S2: Design multiple auxiliary generator sets based on the power plant power value and the rated power value of the main generator set; the rated power of the first-level auxiliary generator set is half of the rated power of the main generator set, the rated power of the second-level auxiliary generator set is half of the rated power of the first-level auxiliary generator set, and so on; S3: Install battery packs in the ship power station corresponding to the electric propulsion ship; S4: Based on the fact that the ratio of the active power load of each generator set on the grid to its rated power is the optimal working condition, and then according to the characteristic that the number of generators in the ship power station is small, the enumeration method is used to obtain the optimal solution for the economic load distribution of the power grid, and the main engine, auxiliary engines at all levels and batteries are opened according to the optimal solution.

2. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 1, characterized in that: The load mentioned in S1 includes continuous load and intermittent load.

3. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 1 or 2, characterized in that: In S2, the multi-stage auxiliary generator set is connected to the main engine in parallel; the ship power station is provided with an emergency generator set; the multi-stage auxiliary generator set and the emergency generator set are of the same model; the auxiliary generator set does not exceed two levels.

4. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 3, characterized in that: The charging and discharging power of the battery pack in S3 is half or more of the power of the auxiliary generator set with the smallest rated power, and the charging and discharging can be adjusted according to the power grid.

5. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 4, characterized in that: The battery capacity in S3 is the difference between the maximum and minimum power of the grid during navigation multiplied by the interval time.

6. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 4, characterized in that: The capacity of the battery pack in S3 is determined based on the optimized operation of the intermittent working equipment under various working conditions.

7. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 3, characterized in that: When the electric propulsion ship is operating at sea, in order to achieve the optimal operating condition in S4, the operation and load distribution of each generator set are as follows: (1) Record the minimum and maximum power values within one hour; (2) Each generator set shall not operate at over-rated load. If the maximum power value exceeds the total rated load of the generator sets on the grid, the total rated power value of the grid shall be increased. The method of increasing the power is as follows: if the auxiliary generator set is not running, add an auxiliary generator set; If the auxiliary generator set is running, start a main generator set and stop the auxiliary generator set; If the maximum power value exceeds the total rated power of the grid, an alarm should be issued and the ship should be advised to slow down; (3) All generator sets are not overloaded; if the maximum power is less than the total rated power of the generator sets on the grid minus half the power of a single main generator set, the total rated power of the generators on the grid is reduced; the reduction method is: if the auxiliary generator set is on the grid, the auxiliary generator set is de-energized; if the auxiliary generator set is not on the grid, an additional auxiliary generator set is added and then one main generator set is de-energized; (4) When the power grid is at its minimum power, the battery pack is charged to increase the power grid load and reduce the engine fuel consumption rate; when the power grid is at its maximum power, the battery charging is stopped.

8. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 7, characterized in that: The minimum and maximum power values described in step (1) do not include the power required for charging the battery.

9. The method for optimizing power load distribution of each generator of an electric propulsion ship according to claim 4, characterized in that: The battery is used to directly supply power to communication and navigation equipment and other weak-current equipment; the order of power supply of the battery is: weak-current equipment, electric compass, and navigation aids.

10. The method for optimizing power load distribution of each generator of an electric propulsion ship according to any one of claims 4 to 9, characterized in that: The distribution method is applicable to the design of economic load distribution of ship power stations of electric propulsion ships, and is also applicable to the design of all ship power stations. At the same time, it is also applicable to the economic load distribution design of small land power stations.

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