An electric ship thermal management system and its control method

Abstract

The present invention provides an electric ship thermal management system and its control method. The thermal management system includes a central cooler, an internal circulation pipeline, and an external circulation pipeline. One side of the external circulation pipeline is connected to the river water outside the ship, and the other side is connected to the central cooler. One side of the internal circulation pipeline is connected to the heat load equipment, and the other side is connected to the central cooler. In addition, a return water bypass and a heating bypass are connected in parallel on the internal circulation pipeline. The above thermal management system can heat up or cool down heat load equipment such as power batteries to keep the temperature constant. In addition, the present invention also provides a control method for the above thermal management system, mainly aiming at the cooling mode, by controlling the operating frequency of the water pump motor to accurately and effectively maintain the temperature of the heat load equipment and ensure the energy-saving and safe operation of the water pump motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal management, and particularly relates to a thermal management system for an electric ship and a control method thereof. Background Art

[0002] With the successive release of a series of policies on ship environmental protection and sustainable development, China has gradually promoted the transformation and upgrading of the shipbuilding industry and focused on "ship electrification". A pure electric ship is a ship whose driving energy is entirely supplied by electric energy. Ocean shipping is mostly used for the transportation of goods or personnel between countries, with a long voyage and a complex and changeable driving environment. There are extremely high standards for the tonnage and endurance of ships, which is not suitable for the development of pure electric ships. Compared with ocean shipping, inland waterway transportation has a smaller scope and shorter route mileage. Therefore, the requirement for the endurance of ships is not high, which is suitable for the development of inland waterway ships. The power battery is the power source of an electric ship and has a certain operating temperature range. At high temperatures, the cycle life of the power battery decreases, the charge and discharge power is limited, and the charging time is prolonged; at low temperatures, the active substances inside the power battery significantly decrease, the internal resistance of the battery increases, and the charge and discharge power and capacity are significantly reduced. In extreme cases, the power battery may not be able to charge or discharge, etc. In order to ensure the high and low temperature performance of the battery, it is necessary to cool the battery at high temperatures and heat the battery at low temperatures. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the present invention provides a thermal management system for an electric ship and a control method thereof to solve the thermal management problem of heat load equipment in an electric ship.

[0004] The present invention achieves the above technical objectives through the following technical means.

[0005] A ship thermal management system, characterized in that: it includes a central cooler, an internal circulation pipeline and an external circulation pipeline. One side of the external circulation pipeline is connected to the river water outside the ship, and the other side is connected to the central cooler. An external circulation pump group is connected in series on the external circulation pipeline; the internal circulation pipeline includes a main pipeline and two bypass pipelines. One side of the main pipeline is connected to the heat load equipment, and the other side is connected to the central cooler. An internal circulation pump group is connected in series on the main pipeline. The bypass pipelines include a return water bypass and a heating bypass. The return water bypass and the heating bypass are both connected in parallel with the central cooler. Among them, a heating device is connected in series in the heating bypass, and both ends of the heating bypass are respectively connected to the main pipeline through a three-way valve. The return water bypass is arranged between the central cooler and the heating bypass, and a temperature control three-way valve is connected between the outlet end of the return water bypass and the main pipeline.

[0006] Furthermore, a filter is provided on the external circulation pipeline, and the filter is arranged between the water intake of the external circulation pipeline and the external circulation pump group.

[0007] Further, three water pumps are respectively provided in the external circulation pump group and the internal circulation pump group, and each water pump is respectively equipped with a water pump motor. The water pump motor is a variable-frequency motor, and the water pump motor is connected to the intelligent motor control module and monitored and controlled by it.

[0008] Further, an external circulation pressure sensor, an external circulation flowmeter, and an external circulation inlet temperature sensor are provided at the inlet of the external circulation side of the central cooler, and an external circulation outlet temperature sensor is provided at the outlet of the external circulation side of the central cooler; an internal circulation pressure sensor, an internal circulation flowmeter, and an internal circulation inlet temperature sensor are provided at the inlet of the heat load device, and an internal circulation outlet temperature sensor and an internal circulation outlet pressure sensor are provided at the outlet of the heat load device.

[0009] Further, a PLC is further included. The intelligent motor control module, the external circulation pressure sensor, the external circulation flowmeter, the external circulation inlet temperature sensor, the external circulation outlet temperature sensor, the internal circulation pressure sensor, the internal circulation flowmeter, the internal circulation inlet temperature sensor, the internal circulation outlet temperature sensor, the internal circulation outlet pressure sensor, and the temperature control three-way valve (27) are all connected to the PLC and controlled by it.

[0010] A control method based on the above ship thermal management system: The thermal management system includes a heating mode and a cooling mode. In the cooling mode, the central cooler is connected to the internal circulation pipeline, and the heating device is disconnected. The external circulation pump group and the internal circulation pump group work simultaneously;

[0011] On the external circulation side, the external circulation pump group works and performs PID automatic adjustment on the water pump motor. The control target is that the water temperature t27 in the temperature control three-way valve = T27, where T27 is the threshold temperature of the temperature control three-way valve. At the same time, when t27 < T27, the temperature control three-way valve opens the return water bypass and adjusts the valve opening size until t27 = T27. When t27 > T27, the temperature control three-way valve keeps the valve of the return water bypass closed;

[0012] On the internal circulation side, the internal circulation pump group works and performs PID automatic adjustment on the water pump motor. The control target is the pressure difference △p between the inlet and outlet of the heat load device = P1, where P1 is set manually.

[0013] Further, one or two water pumps work simultaneously in the external circulation pump group. When one water pump works, when t27 > T27 and the water pump motor runs continuously at the SF1 frequency for the ST1 time, the second water pump is started. The water pump motors of the two water pumps first run at the SF1 frequency for the ST2 time, and then switch to PID automatic adjustment; when two water pumps work, when the water pump motors of the two water pumps both run continuously below the SF2 frequency for the ST2 time, one of the water pumps is stopped; the SF1, SF2, ST1, and ST2 are all set manually.

[0014] Further, when the temperature rise amplitude Δt at the outlet of the heat load device per unit time is greater than T2, the water pump motor in the external circulation pump group runs at an increased frequency of F1 for a time of ST3, and then switches to PID automatic regulation; T2, F1, and ST3 are all set manually.

[0015] Further, a single water pump in the internal circulation pump group operates and its water pump motor is subjected to PID automatic regulation; when the return water bypass valve on the temperature control three-way valve is in the open state and the pressure p26 at the outlet of the internal circulation is less than P26, the water pump motor runs at an increased frequency of F2; when the return water bypass valve on the temperature control three-way valve is in the closed state and the temperature t24 at the inlet of the heat load device is greater than T241 or the temperature t14 at the inlet of the external circulation side of the central cooler is greater than T141, the second water pump is started, where:

[0016] State 1, when t24 is greater than T242 or t14 is greater than T142, the water pump motors of the two water pumps run at a frequency of SF3 until t24 is less than or equal to T242 and t14 is less than or equal to T142, and after continuing for a time of ST4, it switches to State 2;

[0017] State 2, when t24 is less than or equal to T242 and t14 is less than or equal to T142, the water pump motors of the two water pumps run at a frequency of SF1 until t24 is less than or equal to T241 and t14 is less than or equal to T141, and after continuing for a time of ST4, one of the water pumps is stopped and the water pump motor of the other water pump switches back to PID automatic regulation;

[0018] P26, F2, T241, T242, T141, T142, and ST4 are all set manually, where T241 is less than T242 and T141 is less than T142.

[0019] Further, when the external circulation pressure p12 or the external circulation flow rate f13 is lower than the specified value, it is judged whether there is a water pump failure in the external circulation pump group; when the pressure p22 at the inlet of the heat load device or the internal circulation flow rate f23 is lower than the specified value, it is judged whether there is a water pump failure in the internal circulation pump group; when the faulty water pump is identified, the remaining non-operating water pumps are used to replace the faulty water pump.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention provides an electric ship thermal management system, which can heat up or cool down heat load devices such as power batteries to keep the temperature constant. In the cooling mode, the heat load devices such as power batteries are cooled and dissipated through the internal circulation pipeline, and then through the central cooler, and the coolant on the internal circulation side is cooled by using the river water inhaled in the external circulation pipeline to improve the heat dissipation effect. In addition, by introducing a return water bypass in the internal circulation pipeline, a temperature control three-way valve is used to assist in adjusting the water temperature at the inlet of the heat load device to ensure stable cooling effect.

[0022] (2) The present invention also provides a control method for the above thermal management system, mainly aiming at the cooling mode, by controlling the operating frequency of the water pump motor, so as to accurately and effectively maintain the temperature of the heat load device and ensure the energy-saving and safe operation of the water pump motor.

[0023] (3) The present invention sets a plurality of sensors in the internal circulation pipeline and the external circulation pipeline, and formulates corresponding control strategies to dynamically adjust the operating state of the water pump motor, so as to achieve high thermal management performance on the one hand and save the energy consumption of the water pump motor on the other hand.

[0024] (4) Conventional water pump motors only use devices such as thermal relays, and the protection method is relatively single. The present invention comprehensively evaluates and judges the fault situation of the water pump by combining the intelligent motor control module and the monitoring data of various types of sensors on the pipeline, so as to realize diversified protection for the water pump. Description of the Drawings

[0025] Figure 1 is the external circulation pipeline diagram of the present invention;

[0026] Figure 2 is the internal circulation pipeline diagram of the present invention.

[0027] Reference Signs:

[0028] 11 - external circulation pump group; 12 - external circulation pressure sensor; 13 - external circulation flowmeter;

[0029] 14 - external circulation inlet temperature sensor; 15 - external circulation outlet temperature sensor;

[0030] 21 - internal circulation pump group; 22 - internal circulation inlet pressure sensor; 23 - internal circulation flowmeter;

[0031] 24 - internal circulation inlet temperature sensor; 25 - internal circulation outlet temperature sensor; 26 - internal circulation outlet pressure sensor;

[0032] 27 - temperature control three-way valve. Detailed Embodiments

[0033] Embodiments of the present invention will be described in detail below. Examples of the illustrated embodiments are shown in the accompanying drawings, where like or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] I. Hardware Structure

[0035] As Figure 1 and Figure 2 shown, the thermal management system includes a central cooler, an internal circulation pipeline, and an external circulation pipeline. The central cooler is a heat exchange device. One side (external circulation side) of the central cooler is connected to the external circulation pipeline, and the other side (internal circulation side) is connected to the internal circulation pipeline.

[0036] One side of the external circulation pipeline is connected to the river water outside the ship, and the other side is connected to the central cooler. The specific pipeline arrangement is as follows: First, at the water intake of the bottom door of the ship, it is sequentially connected to the inlet of the external circulation side of the central cooler via a filter and an external circulation pump group 11, and then the outlet of the external circulation side of the central cooler is connected to the drainage outlet outside the ship's side.

[0037] The internal circulation pipeline includes a main pipeline and two bypass pipelines. One side of the main pipeline is connected to heat load equipment (such as power batteries), and the other side is connected to the central cooler. The specific pipeline arrangement is as follows: First, from the outlet of the internal circulation side of the central cooler, it is connected to the inlet of the heat load equipment via an internal circulation pump group 21, and then the outlet of the heat load equipment is connected to the inlet of the internal circulation side of the central cooler. The two bypass pipelines are respectively a return water bypass and a heating bypass. The heating bypass is connected in parallel with the central cooler, and both ends of the heating bypass are respectively connected to the main pipeline through a three-way valve; a heating device is connected in series in the heating bypass; by selecting the switch position of the above three-way valve, it is possible to select and switch whether the coolant flows through the central cooler or through the heating device. The return water bypass is connected in parallel between the central cooler and the heating bypass, and a temperature control three-way valve 27 is connected between the outlet end of the return water bypass and the main pipeline; the temperature control three-way valve 27 is a confluence valve that autonomously adjusts the water flow rate to keep the water temperature constant at a set value; the temperature control three-way valve 27 has a main input port, a side input port, and an output port. The main input port is in a fully open state, and the side input port is provided with a valve, and the valve can automatically adjust the opening degree according to the temperature situation; for example, when working, the main input port is connected to hot water and the side input port is connected to cold water, and the temperature control three-way valve 27 automatically adjusts the opening degree of the valve at the side input port according to the water temperature inside it to ensure that the output water temperature is constant; specifically in the present invention, the main input port is connected to the outlet of the internal circulation side of the central cooler, and the side input port is connected to the return water bypass.

[0038] The working modes of the above thermal management system include a heating mode, a cooling mode, and a standby mode, where the standby mode means that all devices are in a standby state without performing any actions. In the heating mode, only the internal circulation pump group 21 works. At the same time, through the three-way valves at both ends of the heating bypass, the heating device is connected to the internal circulation pipeline, and the central cooler is disconnected from the internal circulation pipeline. In this mode, the coolant flows into the heat load device after being heated by the heating device, thereby heating and raising the temperature of the heat load device.

[0039] In the cooling mode, the external circulation pump group 11 and the internal circulation pump group 21 work simultaneously. Through the three-way valves at both ends of the heating bypass, the central cooler is connected to the internal circulation pipeline, and at the same time, the heating device is disconnected from the internal circulation pipeline. In this mode, on the external circulation side, river water is pumped into the external circulation pipeline from outside the ship, and after being filtered by the filter, it is pumped into the central cooler. The river water exchanges heat with the coolant on the internal circulation side in the central cooler to help the coolant on the internal circulation side dissipate heat and cool down. Finally, the river water after heat exchange is discharged back into the river through the external circulation pipeline again. On the internal circulation side, the coolant is pumped from the central cooler into the heat load device and cools down the heat load device by heat exchange during the flow process. Then, the heated coolant flows back to the central cooler again and exchanges heat with the river water in the central cooler to achieve its own heat dissipation and cooling.

[0040] Both the above external circulation pump group 11 and internal circulation pump group 21 are pump groups composed of multiple pumps used in parallel. In this embodiment, there are specifically three pumps in the pump group, which are divided into two main pumps and one standby pump according to the functional purpose. Each of the above pumps is equipped with a pump motor and is driven by the pump motor to work. The pump motor is a variable-frequency motor, that is, the motor speed is adjusted by a variable-frequency method, and finally the purpose of adjusting the operating power of the pump is achieved. Each of the above pump motors is electrically connected to the intelligent motor control module. The intelligent motor control module can real-time monitor the operating parameters such as the voltage, current, and frequency of the pump motor, and directly control the start and stop of the pump motor and adjust the input frequency of the motor.

[0041] To achieve intelligent control of the above thermal management system and its pump group:

[0042] An external circulation pressure sensor 12, an external circulation flowmeter 13, an external circulation inlet temperature sensor 14, and an external circulation outlet temperature sensor 15 are provided on the external circulation pipeline. Among them, the external circulation pressure sensor 12, the external circulation flowmeter 13, and the external circulation inlet temperature sensor 14 are located at the inlet of the external circulation side of the central cooler, and the external circulation outlet temperature sensor 15 is located at the outlet of the external circulation side of the central cooler.

[0043] An internal circulation inlet pressure sensor 22, an internal circulation flowmeter 23, an internal circulation inlet temperature sensor 24, an internal circulation outlet temperature sensor 25, and an internal circulation outlet pressure sensor 26 are provided on the internal circulation pipeline; among them, the internal circulation pressure sensor 22, the internal circulation flowmeter 23, and the internal circulation inlet temperature sensor 24 are located at the inlet of the heat load device, and the internal circulation outlet temperature sensor 25 and the internal circulation outlet pressure sensor 26 are located at the outlet of the heat load device.

[0044] The above intelligent motor control module, external circulation pressure sensor 12, external circulation flowmeter 13, external circulation inlet temperature sensor 14, external circulation outlet temperature sensor 15, internal circulation inlet pressure sensor 22, internal circulation flowmeter 23, internal circulation inlet temperature sensor 24, internal circulation outlet temperature sensor 25, internal circulation outlet pressure sensor 26, and temperature control three-way valve 27 are all electrically connected to the PLC. Among them, the external circulation pressure sensor 12 is used to monitor the external circulation pressure p12, the external circulation flowmeter 13 is used to monitor the external circulation flow f13, the external circulation inlet temperature sensor 14 is used to monitor the inlet temperature t14 of the external circulation side of the central cooler, the external circulation outlet temperature sensor 15 is used to monitor the outlet temperature t15 of the external circulation side of the central cooler, the internal circulation inlet pressure sensor 22 is used to monitor the inlet pressure p22 of the heat load device, the internal circulation flowmeter 23 is used to monitor the internal circulation flow f23, the internal circulation inlet temperature sensor 24 is used to monitor the inlet temperature t24 of the heat load device, the internal circulation outlet temperature sensor 25 is used to monitor the outlet temperature t25 of the heat load device, the internal circulation outlet pressure sensor 26 is used to monitor the outlet pressure p26 of the heat load device, and at the same time, the temperature control three-way valve 27 can also monitor the water temperature t27 inside it.

[0045] II. Control Method

[0046] In the cooling mode, since the river water temperature and the heat generation situation of the heat load device change greatly, in order to more accurately and effectively maintain the temperature situation of the heat load device, and at the same time ensure the energy-saving and safe operation of the water pump motor, corresponding control strategies are formulated. The specific control method is as follows:

[0047] External circulation side:

[0048] Strategy 1.1, one or two water pumps in the external circulation pump group work and perform PID automatic adjustment on their water pump motors; the control target of the PID automatic adjustment is that the water temperature t27 in the temperature control three-way valve 27 = the threshold temperature T27, where the threshold temperature T27 is set manually and is set to 34 °C in this embodiment. At the same time, the temperature control three-way valve 27 will also automatically adjust the valve opening of the return water bypass according to the water temperature t27 inside it; when t27 < T27, the temperature control three-way valve 27 opens the return water bypass and adjusts the valve opening size until t27 = T27; when t27 > T27, the valve of the return water bypass is kept closed.

[0049] Since there is an upper limit frequency SF1 for PID automatic regulation, and SF1 is specifically set manually according to the pump model used. For example, it is set to 45Hz, that is, through PID automatic regulation, the maximum operating frequency of the pump motor can only reach 45Hz. Therefore, when the working performance of a single pump in the external circulation pump group does not meet the requirements, two pumps are enabled to work; conversely, if the working performance of two pumps is excessive, one of them is shut down. The specific rules for the single / double pump switching are as follows:

[0050] 1) When a single pump in the external circulation pump group 11 is working, when t27>T27 and the pump motor of the pump runs continuously at the frequency of SF1 (45Hz) for the ST1 time (ST1 is set manually, and in this embodiment, it is set to 1min), the second pump is started. After the second pump enters the working state, the pump motors of the two pumps first run at the SF1 frequency. After continuously running for the ST2 time (ST2 is set manually, and in this embodiment, it is set to 5min), the pump motors of the two pumps switch to PID automatic regulation.

[0051] 2) When two pumps in the external circulation pump group 11 are working, when the operating frequencies of the pump motors of the two pumps are both lower than the SF2 frequency (SF2 is specifically set manually according to the pump model used, for example, it is set to 40Hz), and continuously run below the SF2 frequency for the ST2 (5min) time, then one of the pumps is stopped, and it switches to single pump operation and the pump motor is automatically regulated by PID.

[0052] Strategy 1.2, on the basis of Strategy 1.1, the PLC calculates the temperature rise amplitude △t per unit time at the outlet of the heat load device according to the real-time collected outlet temperature t25 of the heat load device (if the temperature is decreasing, then △t is negative). When △t>T2 (T2 is set manually), it is determined that the ship's heat load has suddenly increased, and thus the operating frequency of the pump motor in the current external circulation pump group 11 is increased by the F1 frequency (F1 is set manually, and in this embodiment, it is set to 5Hz). However, the increased operating frequency cannot exceed the maximum operating frequency SF3 of the pump motor (SF3 is specifically set manually according to the pump model used, for example, it is set to 50Hz); after the pump motor runs continuously at the increased frequency for the ST3 (ST3 is set manually, and in this embodiment, it is set to 5min) time, it returns to Strategy 1.1 and switches to PID automatic regulation.

[0053] Strategy 1.3, on the basis of Strategies 1.1 to 1.2, when the external circulation pressure p12 or the external circulation flow f13 is lower than the specified value, combined with the operating parameters monitored by the intelligent motor control module, it is judged whether the external circulation pump has a fault. When the PLC determines that a certain pump has a fault, that pump is stopped, and the remaining non-working pumps are enabled for replacement.

[0054] Inner loop side:

[0055] Strategy 2.1: One single pump in the inner loop pump group 21 operates and its pump motor is automatically adjusted by PID. The control target of the PID automatic adjustment is the pressure difference △p = P1 between the inlet and outlet of the heat load equipment, where △p = p22 - p26. In this embodiment, P1 is set to 0.3 MPa.

[0056] Strategy 2.2: On the basis of Strategy 2.1, when the return water bypass valve on the temperature control three-way valve 27 is in the open state and the inner loop outlet pressure p26 < P26 (P26 is set manually), the operating frequency of the pump motor is increased by F2 frequency (F2 is set manually, and in this embodiment, it is set to 5 Hz).

[0057] Strategy 2.3: On the basis of Strategy 2.1, when the return water bypass valve on the temperature control three-way valve 27 is in the closed state and at the same time t24 > T241 or t14 > T141, the second pump in the inner loop pump group 21 is enabled, which is divided into:

[0058] State 1: When t24 > T242 or t14 > T142, the pump motors of the two pumps operate at the SF3 (50 Hz) frequency; until t24 ≤ T242 and t14 ≤ T142, and after continuing for ST4 (ST4 is set manually, and in this embodiment, it is set to 2 min), it then transfers to State 2.

[0059] State 2: When t24 ≤ T242 and t14 ≤ T142, the pump motors of the two pumps operate at the SF1 (45 Hz) frequency; until t24 ≤ T241 and t14 ≤ T141, and after continuing for ST4 (2 min), then one of the pumps stops and returns to Strategy 2.1.

[0060] The above T241, T242, T141, and T242 are all set manually, where T241 < T242, T141 < T142. Specifically, in this embodiment, T241 = 44 °C, T242 = 46 °C, T141 = 38 °C, and T142 = 40 °C.

[0061] Strategy 2.4: On the basis of Strategies 2.1 to 2.3, when the inlet pressure p22 of the heat load equipment or the inner loop flow rate f23 is lower than the specified value, and at the same time combined with the operating parameters monitored by the intelligent motor control module, it is judged whether there is a fault in the pumps in the inner loop pump group 21. When the PLC determines that a certain pump has a fault, then stop this pump and enable the remaining non-operating pumps for replacement.

[0062] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0063] The present invention is not limited to the above embodiments. Without departing from the essence of the present invention, any obvious improvements, substitutions or modifications that those skilled in the art can make shall fall within the protection scope of the present invention.

Claims

1. A ship thermal management system, characterized in that: It includes a central cooler, an internal circulation pipeline and an external circulation pipeline. One side of the external circulation pipeline is connected to the river water outside the ship, and the other side is connected to the central cooler. An external circulation pump group (11) is connected in series on the external circulation pipeline; the internal circulation pipeline includes a main pipeline and two bypass pipelines. One side of the main pipeline is connected to the heat load equipment, and the other side is connected to the central cooler. An internal circulation pump group (21) is connected in series on the main pipeline. The bypass pipelines include a return water bypass and a heating bypass. The return water bypass and the heating bypass are both connected in parallel with the central cooler. A heating device is connected in series in the heating bypass. The two ends of the heating bypass are respectively connected to the main pipeline through three-way valves. The return water bypass is arranged between the central cooler and the heating bypass. A temperature control three-way valve (27) is connected between the outlet end of the return water bypass and the main pipeline; Three water pumps are respectively provided in the external circulation pump group (11) and the internal circulation pump group (21). Each water pump is respectively equipped with a water pump motor. The water pump motor is a variable frequency motor. The water pump motor is connected to the intelligent motor control module and is monitored and controlled by it; On the external circulation side, the external circulation pump group (11) works and performs PID automatic adjustment on the water pump motor. The control target is that the water temperature t27 in the temperature control three-way valve (27) = T27, where T27 is the threshold temperature of the temperature control three-way valve (27); In the external circulation pump group (11), one single water pump or two water pumps work simultaneously. When a single water pump works, when t27 > T27 and the water pump motor runs continuously at the SF1 frequency for the ST1 time, then the second water pump is started. The water pump motors of the two water pumps first run at the SF1 frequency for the ST2 time, and then switch to PID automatic adjustment; when two water pumps work, when the water pump motors of the two water pumps both run continuously below the SF2 frequency for the ST2 time, then one of the water pumps is stopped.

2. The ship thermal management system according to claim 1, characterized in that: A filter is provided on the external circulation pipeline. The filter is arranged between the water intake of the external circulation pipeline and the external circulation pump group (11).

3. The ship thermal management system according to claim 1, characterized in that: An external circulation pressure sensor (12), an external circulation flowmeter (13) and an external circulation inlet temperature sensor (14) are provided at the external circulation side inlet of the central cooler. An external circulation outlet temperature sensor (15) is provided at the external circulation outlet of the central cooler; an internal circulation pressure sensor (22), an internal circulation flowmeter (23) and an internal circulation inlet temperature sensor (24) are provided at the inlet of the heat load equipment. An internal circulation outlet temperature sensor (25) and an internal circulation outlet pressure sensor (26) are provided at the outlet of the heat load equipment.

4. The ship thermal management system according to claim 3, characterized in that: It also includes a PLC. The intelligent motor control module, the external circulation pressure sensor (12), the external circulation flowmeter (13), the external circulation inlet temperature sensor (14), the external circulation outlet temperature sensor (15), the internal circulation pressure sensor (22), the internal circulation flowmeter (23), the internal circulation inlet temperature sensor (24), the internal circulation outlet temperature sensor (25), the internal circulation outlet pressure sensor (26) and the temperature control three-way valve (27) are all connected to the PLC and are controlled by it.

5. A control method for a ship thermal management system according to any one of claims 1 to 4, characterized in that: The heat management system includes a heating mode and a cooling mode. In the cooling mode, the central cooler is connected to the internal circulation pipeline, and the heating device is disconnected. The external circulation pump group (11) and the internal circulation pump group (21) work simultaneously. On the external circulation side, when t27 < T27, the temperature control three-way valve (27) opens the return water bypass and adjusts the valve opening until t27 = T27. When t27 > T27, the temperature control three-way valve (27) keeps the valve of the return water bypass closed. On the internal circulation side, the internal circulation pump group (21) works and performs PID automatic adjustment on the water pump motor, with the control target being the pressure difference △p = P1 between the inlet and outlet of the heat load equipment.

6. The control method of the ship thermal management system according to claim 5, characterized in that: When the temperature rise amplitude △t at the outlet of the heat load equipment per unit time > T2, the water pump motor in the external circulation pump group (11) runs at an increased frequency of F1 for a time of ST3, and then switches to PID automatic adjustment.

7. The control method of the ship thermal management system according to claim 5, characterized in that: In the internal circulation pump group (21), a single water pump works and performs PID automatic adjustment on its water pump motor. When the return water bypass valve on the temperature control three-way valve (27) is in the open state and the internal circulation outlet pressure p26 < P26, the water pump motor runs at an increased frequency of F2. When the return water bypass valve on the temperature control three-way valve (27) is in the closed state, and the inlet temperature t24 of the heat load equipment > T241 or the inlet temperature t14 of the external circulation side of the central cooler > T141, the second water pump is started. Among them: State 1, when t24 > T242 or t14 > T142, the water pump motors of the two water pumps run at a frequency of SF3 until t24 ≤ T242 and t14 ≤ T142. After continuing for a time of ST4, it switches to State 2. State 2, when t24 ≤ T242 and t14 ≤ T142, the water pump motors of the two water pumps run at a frequency of SF1 until t24 ≤ T241 and t14 ≤ T141. After continuing for a time of ST4, one of the water pumps is stopped, and the water pump motor of the other water pump resumes PID automatic adjustment. Among them, T241 < T242, T141 < T142.

8. The control method of the ship thermal management system according to claim 5, characterized in that: When the external circulation pressure p12 or the external circulation flow rate f13 is lower than the specified value, it is judged whether there is a water pump failure in the external circulation pump group (11). When the inlet pressure p22 of the heat load equipment or the internal circulation flow rate f23 is lower than the specified value, it is judged whether there is a water pump failure in the internal circulation pump group (21). After the faulty water pump is identified, the remaining non-working water pumps are enabled to replace the faulty water pump.

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