Control method of once-through cooling unit and terminal

Abstract

The invention discloses a direct current cooling unit control method and a terminal, the direct current cooling unit is carried on a direct current bus of an energy storage system, and the on-grid and off-grid states and the electricity price time period of the energy storage system and the electric quantity state of an energy storage battery are detected; and the power utilization cost is judged based on the grid-connected and off-grid states of the energy storage system and the electricity price time period, and when the electricity price time period is a peak or at ordinary times and the energy storage system is in the grid-connected state, the energy storage battery is preferentially used for supplying power to the direct-current cooling unit. According to the invention, an extra AC-DC conversion process is not needed, loss in an energy conversion process is reduced, and influences of three-phase imbalance, harmonic waves and pulse current caused by direct power supply at an AC side are avoided; at the electricity price peak or at ordinary times, the energy storage battery is preferentially used for supplying power to the direct-current cooling unit, the situation that the cooling unit continuously uses the mains supply, and consequently the electricity utilization cost is increased is avoided, and the electricity utilization cost at the peak and valley is improved from the time dimension.

Description

Technical Field

[0001] The present invention relates to the field of energy storage cooling, and in particular to a control method and a terminal for a direct current cooling unit. Background Art

[0002] With the popularization of renewable energy and the increasing demand for grid stability, the role of energy storage systems in the power system is becoming increasingly important. At the same time, with the continuous increase in the penetration rate of new energy vehicles, the demand in the public charging field is also continuing to rise. Photovoltaic storage and charging integration and industrial and commercial energy storage are important concepts that have emerged against the backdrop of global energy transformation and power market reform. They represent the innovative application of clean energy utilization and energy storage technology in different fields. For example, industrial and commercial parks can establish charging stations that integrate photovoltaic storage and charging, use solar energy to generate electricity and store it during the day, and use it to charge electric vehicles at night or during peak hours. At the same time, the remaining energy can also be used for other loads in the park, or sold to the power grid when electricity prices are high, to achieve optimal energy allocation and maximize economic benefits.

[0003] Battery energy storage systems, especially lithium-ion battery energy storage systems, are sensitive to temperature. Too high or too low temperatures will affect the performance and life of the battery. The battery generates heat during the charging and discharging process. If it is not controlled, it will cause the battery temperature to rise, which will affect the efficiency, safety and life of the battery. Therefore, an efficient thermal management system has become an indispensable part of the design of energy storage systems. Compared with traditional air cooling technology, liquid cooling technology has higher heat exchange efficiency and more stable temperature control capabilities.

[0004] However, in the existing energy storage system, the AC cooling unit, as part of the thermal management system, is mainly used to adjust the temperature of the battery pack to ensure that the battery operates within the optimal operating temperature range. Although the cooling system has significant advantages in thermal management efficiency and battery life protection, as an AC-driven cooling unit, it also has some disadvantages, mainly including: 1. Energy conversion efficiency: The compressor, water pump, fan and other components of the AC cooling unit are usually driven by an AC motor. If the power supply side is AC, the inverter needs to complete the rectification first and then invert it into the AC power supply of the required control frequency. This energy conversion process will be accompanied by a certain efficiency loss, which reduces the overall energy efficiency of the system. 2. Poor power quality: The power supply path of the cooling unit is provided by the power grid to the AC unit. The power supply on the AC side is often accompanied by three-phase imbalance, harmonics, pulse current and other effects, which directly damages the compressor, water pump and fan in the AC unit. At the same time, the power cost of the AC unit is greatly affected by the fluctuation of electricity prices. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a control method and terminal for a DC cooling unit, so as to solve the problem that the power quality received by the original cooling unit is poor and the electricity cost is high.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A control method for a DC cooling unit, wherein the DC cooling unit is mounted on a DC bus of an energy storage system, the method comprising the steps of: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. The electricity cost is determined based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is preferentially used to power the DC cooling unit.

[0007] In order to solve the above technical problems, another technical solution adopted by the present invention is: A control terminal for a DC cooling unit includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor completes the following steps when executing the computer program: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. The electricity cost is determined based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is preferentially used to power the DC cooling unit.

[0008] The beneficial effects of the present invention are: providing a control method and terminal for a DC cooling unit, by mounting the cooling unit on the DC bus of an energy storage system instead of on an AC bus outside the energy storage system, using the DC power supply of the energy storage system to directly power the electrical facilities (compressor, water pump, fan, etc.) in the water cooling unit, without the need for an additional AC to DC conversion process, reducing the loss in the energy conversion process, and avoiding the influence of three-phase imbalance, harmonics, and pulse current caused by direct power supply on the AC side; At the same time, since there is no need for an inverter or frequency converter to convert DC power into AC power, the system structure of the DC cooling unit is simpler, reducing the number and complexity of equipment, reducing system costs and failure rates, and also reducing the unit system size; In addition, when electricity prices are at peak or normal times, energy storage batteries are used to power the DC cooling units first to avoid the cooling units continuously using mains electricity, which leads to increased electricity costs, and improves electricity costs during peak and valley periods from a time dimension. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a flow chart of a control method of a direct cooling unit in an embodiment of the present invention; Figure 2 It is a schematic diagram of the installation of a DC cooling unit and an energy storage system in an embodiment of the present invention; Figure 3 Schematic diagram of the power path of the DC cooling unit in an embodiment of the present invention; Figure 4 is a schematic diagram of a control terminal of a DC cooling unit in an embodiment of the present invention; Description of labels: 1. A control terminal for a DC cooling unit; 2. A memory; 3. A processor. DETAILED DESCRIPTION

[0010] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0011] Please refer to Figures 1 to 3 , a control method for a DC cooling unit, wherein the DC cooling unit is mounted on a DC bus of an energy storage system, the method comprising the steps of: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. The electricity cost is determined based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is preferentially used to power the DC cooling unit.

[0012] It is understandable that the electricity cost of the water-cooling unit is based on the direct energy consumption of the water-cooling unit, energy utilization efficiency and real-time electricity price. For example: the electricity cost of the water-cooling unit = direct energy consumption of the water-cooling unit / energy efficiency utilization rate of the water-cooling unit × real-time electricity price, where the energy efficiency utilization rate of the water-cooling unit refers to the energy utilization efficiency between the grid side and the unit side; the real-time electricity price is based on the pricing of the grid at each time, and the difference between the peak and valley values ​​of electricity prices in some areas can be up to twice. In order to control the cost of electricity, the energy storage battery in the DC source of the energy storage system is charged during the valley period of electricity prices, and energy is stored during the peak period of electricity prices, and then the low-priced electricity stored in the early stage is released to the outside world, which can maximize the benefits. When the DC cooling unit is mounted on the DC bus of the energy storage system, the DC cooling unit has three electricity consumption paths: (1) External grid → energy storage converter (PCS) → DC unit; (2) Energy storage battery → DC unit; (3) Energy storage battery + (external grid → PCS) → DC unit.

[0013] Among them, the AC power from the external power grid in paths (1) and (3) has been rectified by the energy storage converter, avoiding the impact of three-phase imbalance, harmonics, pulse current, etc. caused by the AC side power supply. Path (2) does not have the above impact due to DC power supply. At the same time, since there is no need for an inverter or frequency converter to convert DC power into AC power, the system structure of the DC cooling unit is simpler, reducing the number and complexity of equipment, reducing system costs and failure rates, and also reducing the size of the unit system; in addition, when the electricity price is at peak or normal times, the energy storage battery is used to power the DC cooling unit first, avoiding the cooling unit from continuously using the mains electricity, which leads to an increase in electricity costs, and improving the electricity costs during peak and valley times from a time dimension.

[0014] In an embodiment of the present invention, step S2 specifically includes the steps of: S21, based on the energy storage system's on-grid and off-grid status and electricity price period to determine the electricity cost, when the electricity price period is peak or normal and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is high and proceeds to step S22; when the electricity price period is valley time and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is low and proceeds to step S23; S22, preferentially using the energy storage battery to power the DC cooling unit, and when the energy storage battery is in or about to be in a feeding state, using the energy storage converter to rectify the power of the external power grid and provide it to the DC cooling unit for power supplement; S23, using the energy storage battery to supply power to the DC cooling unit; And / or, utilizing an energy storage converter to rectify the power of an external power grid and provide power to the DC cooling unit.

[0015] As can be seen from the above description, in this method, the judgment of electricity cost based on electricity price period and grid-connected and off-grid status is further refined. By giving priority to using energy storage batteries for power supply during peak or normal periods of electricity price, and using energy storage converters to supplement power from the external power grid when the energy storage batteries are fed, the stable operation of the DC cooling unit can be ensured, while effectively controlling the electricity cost, improving the operating efficiency and economy of the system, and avoiding the risk of excessive discharge of the battery; at the same time, when the electricity cost is low, the DC cooling unit can be powered by the energy storage battery or the external power grid alone, or the energy storage battery and the external power grid can be jointly powered. Preferably, when the electricity cost is low, if the energy storage battery enters the charging state, it is powered by the external power grid, and if the energy storage battery maintains the discharging state, it is jointly powered by the energy storage battery and the external power grid.

[0016] In an embodiment of the present invention, the step S23 further includes a step S24: Detect the electricity cost of the current stage. If the electricity cost of the current stage is high, control the DC cooling unit to raise the refrigeration start point and the refrigeration stop point; if the electricity cost of the current stage is low, control the DC cooling unit to lower the refrigeration start point and the refrigeration stop point.

[0017] From the above description, it can be seen that this method adds real-time monitoring of electricity costs on the basis of the above, and adjusts the refrigeration start point and stop point based on the cost. When the electricity cost is high, the refrigeration start point and stop point are raised, the operation time of the refrigeration unit is reduced, the cooling effect is relatively reduced, and the electricity cost is reduced. For example, the original refrigeration start point is 35°C and the refrigeration stop point is 30°C. In the stage of high electricity cost, the refrigeration start point is raised to 40°C and the refrigeration stop point is raised to 35°C, with an increase of 5°C; when the electricity cost is low, the refrigeration start point and stop point are lowered, and the refrigeration working time of the unit is appropriately extended. However, the electricity cost at this stage is lower than the economic cost of other stages. First, the "coldness" of the battery cell can be maintained, and the battery cell can be stored under relatively low temperature conditions, thereby reducing the refrigeration demand of the battery cell when the electricity cost is high in the next stage; second, the average temperature of the battery cell is reduced, the battery life is increased, and the SOH decay is delayed.

[0018] In this way, the operating parameters of the cooling unit can be dynamically adjusted according to the fluctuation of electricity prices, reducing energy consumption when electricity prices are high and making full use of cheap electricity for refrigeration when electricity prices are low, further optimizing the operating cost and efficiency of the system.

[0019] In an embodiment of the present invention, the step S24 specifically includes the steps of: Detect the electricity cost of the current stage. If the electricity cost of the current stage is high, control the DC cooling unit to raise the refrigeration start point and the refrigeration stop point by a preset level every time a preset period of time passes; if the electricity cost of the current stage is low, control the DC cooling unit to lower the refrigeration start point and the refrigeration stop point by a preset level every time a preset period of time passes.

[0020] From the above description, it can be seen that this method further optimizes the adjustment mechanism of the refrigeration start point and stop point, and by setting the preset duration and magnitude, the temperature control strategy can gradually adapt to changes in electricity prices. This gradual adjustment avoids control lags or frequent adjustments caused by too fast or too slow fluctuations in electricity prices, improves the response speed and control accuracy of the system, and ensures that the DC cooling unit can operate efficiently under different electricity price conditions. Specifically, the preset duration is 8-15 minutes, and the preset magnitude is 1-2°C; preferably, the original refrigeration start point and refrigeration stop point are adjusted by 1°C every 10 minutes until the limit value is reached.

[0021] In an embodiment of the present invention, the step S2 further comprises the steps of: When the energy storage system is off-grid, the energy storage battery is controlled to supply power to the DC cooling unit. This ensures that the system can still operate normally in the event of a grid outage or special circumstances. This method enhances the reliability and independence of the system, especially when operating off-grid, it can maintain the continuous operation of the cooling system and avoid the problem of overheating of the battery cells caused by power outages. At the same time, it ensures that the cooling unit can still operate synchronously with the energy storage battery when off-grid. When the energy storage battery is feeding power, the cooling unit and the energy storage battery enter a shutdown state together.

[0022] Please refer to Figure 4 A control terminal for a direct current cooling unit comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor completes the steps in a control method for a direct current cooling unit when executing the computer program.

[0023] The present invention provides a control method and terminal for a DC cooling unit, which are mainly used in an energy storage system to solve the problem that the cooling unit is easily affected by the AC side power conditions and has high electricity costs. The following is a specific description in conjunction with an embodiment: Please refer to Figures 1 to 3 , Embodiment 1 of the present invention is: A control method for a DC cooling unit, wherein the DC cooling unit is mounted on a DC bus of an energy storage system, the method comprising the steps of: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. Determine the electricity cost based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is used to power the DC cooling unit first; When the energy storage system is off-grid, the energy storage battery is controlled to supply power to the DC cooling unit.

[0024] Specifically, when the DC cooling unit is mounted on the DC bus of the energy storage system, the DC cooling unit has three power consumption paths: (1) External grid → energy storage converter (PCS) → DC unit; (2) Energy storage battery → DC unit; (3) Energy storage battery + (external grid → PCS) → DC unit.

[0025] Among them, the AC power from the external power grid in paths (1) and (3) has been rectified by the energy storage converter, avoiding the impact of three-phase imbalance, harmonics, pulse current, etc. caused by the AC side power supply. Path (2) does not have the above impact due to DC power supply. At the same time, since there is no need for an inverter or frequency converter to convert DC power into AC power, the system structure of the DC cooling unit is simpler, reducing the number and complexity of equipment, reducing system costs and failure rates, and also reducing the size of the unit system; in addition, when the electricity price is at peak or normal times, the energy storage battery is used to power the DC cooling unit first, avoiding the cooling unit from continuously using the mains electricity, which leads to an increase in electricity costs, and improving the electricity costs during peak and valley times from a time dimension.

[0026] Step S2 specifically includes the following steps: S21, based on the energy storage system's on-grid and off-grid status and electricity price period to determine the electricity cost, when the electricity price period is peak or normal and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is high and proceeds to step S22; when the electricity price period is valley time and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is low and proceeds to step S23; S22, using energy storage batteries to supply power to the DC cooling unit first, and when the energy storage batteries are in or about to be in a feeding state, using energy storage converters to rectify the power of the external power grid and supply it to the DC cooling unit for power supplement; S23, using energy storage batteries to supply power to the DC cooling unit; And / or, an energy storage converter is used to rectify the power of an external power grid and provide power to the DC cooling unit.

[0027] That is, in this embodiment, the judgment of electricity cost based on electricity price period and grid-connected and off-grid status is further refined. By giving priority to using energy storage batteries for power supply during peak or normal periods of electricity price, and using energy storage converters to supplement power from the external power grid when the energy storage batteries are fed, the stable operation of the DC cooling unit can be ensured, while effectively controlling the electricity cost, improving the operating efficiency and economy of the system, and avoiding the risk of excessive discharge of the battery; at the same time, when the electricity cost is low, the DC cooling unit can be powered by the energy storage battery or the external power grid alone, or the energy storage battery and the external power grid can be jointly powered. Preferably, when the electricity cost is low, if the energy storage battery enters the charging state, it is powered by the external power grid, and if the energy storage battery maintains the discharging state, it is jointly powered by the energy storage battery and the external power grid.

[0028] Embodiment 2 of the present invention is: Based on the first embodiment, step S23 further includes step S24: Detect the electricity cost of the current stage. If the electricity cost of the current stage is high, control the DC cooling unit to raise the refrigeration start point and the refrigeration stop point by a preset level every preset time until the refrigeration start point and the refrigeration stop point reach the preset upper limit of the increase; if the electricity cost of the current stage is low, control the DC cooling unit to lower the refrigeration start point and the refrigeration stop point by a preset level every preset time until the refrigeration start point and the refrigeration stop point reach the preset lower limit of the decrease.

[0029] Specifically, the original refrigeration start point is 35°C, the refrigeration stop point is 30°C, the preset duration is 10 minutes, the preset magnitude is 1°C, the preset upper limit is 5°C, and the preset lower limit is 5°C. The control process is specifically: if the electricity cost is high at the current stage, the DC cooling unit is controlled to increase the start point and stop point temperature by 1°C every 10 minutes; similarly, if the electricity cost is low at the current stage, the DC cooling unit is controlled to reduce the start point and stop point temperature by 1°C every 10 minutes; the gradual adjustment avoids control lag or frequent adjustments caused by too fast or too slow fluctuations in electricity prices, improves the response speed and control accuracy of the system, and ensures that the DC cooling unit can operate efficiently under different electricity price conditions.

[0030] Please refer to Figure 4 , Embodiment 3 of the present invention is: A control terminal 1 of a DC cooling unit includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, steps in a control method of a DC cooling unit are completed.

[0031] In summary, the control method and terminal of a DC cooling unit provided by the present invention mounts the cooling unit on the DC bus of the energy storage system instead of on the AC bus outside the energy storage system, and uses the DC power supply of the energy storage system to directly power the electrical facilities (compressor, water pump, fan, etc.) in the water cooling unit, without the need for an additional AC to DC conversion process, thereby reducing the loss in the energy conversion process and avoiding the influence of three-phase imbalance, harmonics, and pulse current caused by direct power supply on the AC side. At the same time, since there is no need for an inverter or frequency converter to convert DC power into AC power, the system structure of the DC cooling unit is simpler, reducing the number and complexity of equipment, reducing system costs and failure rates, and also reducing the unit system size; In addition, when electricity prices are at peak or normal times, energy storage batteries are used to power the DC cooling units first to avoid the cooling units continuously using mains electricity, which leads to increased electricity costs, and improves electricity costs during peak and valley periods from a time dimension.

[0032] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A control method for a direct cooling unit, characterized in that: The DC cooling unit is mounted on a DC bus of an energy storage system, and the method comprises the steps of: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. The electricity cost is determined based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is preferentially used to power the DC cooling unit.

2. The control method of a direct cooling unit according to claim 1, characterized in that: The step S2 specifically includes the following steps: S21, based on the energy storage system's on-grid and off-grid status and electricity price period to determine the electricity cost, when the electricity price period is peak or normal and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is high and proceeds to step S22; when the electricity price period is valley time and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is low and proceeds to step S23; S22, preferentially using the energy storage battery to power the DC cooling unit, and when the energy storage battery is in or about to be in a feeding state, using the energy storage converter to rectify the power of the external power grid and provide it to the DC cooling unit for power supplement; S23, using the energy storage battery to supply power to the DC cooling unit; And / or, utilizing an energy storage converter to rectify the power of an external power grid and provide power to the DC cooling unit.

3. The control method of a direct cooling unit according to claim 2, characterized in that: The step S23 further includes a step S24: Detect the electricity cost of the current stage. If the electricity cost of the current stage is high, control the DC cooling unit to raise the refrigeration start point and the refrigeration stop point; if the electricity cost of the current stage is low, control the DC cooling unit to lower the refrigeration start point and the refrigeration stop point.

4. The control method of a direct cooling unit according to claim 3, characterized in that: The step S24 specifically includes the following steps: Detecting the electricity cost of the current stage, if the electricity cost of the current stage is high, controlling the DC cooling unit to raise the refrigeration start point and refrigeration stop point by a preset level every preset time; If the electricity cost is low at the current stage, the DC cooling unit is controlled to reduce the refrigeration start point and the refrigeration stop point by a preset level every preset time.

5. The control method of a direct cooling unit according to claim 2, characterized in that: The step S2 further comprises the steps of: When the energy storage system is in an off-grid state, the energy storage battery is controlled to supply power to the DC cooling unit.

6. A control terminal for a DC cooling unit, characterized in that: The invention comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following steps are performed: S1. Detect the on-grid and off-grid status of the energy storage system, the electricity price period and the power status of the energy storage battery; S2. The electricity cost is determined based on the grid-connected and off-grid status of the energy storage system and the electricity price period. When the electricity price period is peak or normal and the energy storage system is grid-connected, the energy storage battery is preferentially used to power the DC cooling unit.

7. The control terminal of a DC cooling unit according to claim 6, characterized in that: The step S2 specifically includes the following steps: S21, based on the energy storage system's on-grid and off-grid status and electricity price period to determine the electricity cost, when the electricity price period is peak or normal and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is high and proceeds to step S22; when the electricity price period is valley time and the energy storage system is in the grid-connected state, it is determined that the electricity cost at this stage is low and proceeds to step S23; S22, preferentially using the energy storage battery to power the DC cooling unit, and when the energy storage battery is in or about to be in a feeding state, using the energy storage converter to rectify the power of the external power grid and provide it to the DC cooling unit for power supplement; S23, using the energy storage battery to supply power to the DC cooling unit; And / or, utilizing an energy storage converter to rectify the power of an external power grid and provide power to the DC cooling unit.

8. The control terminal of a DC cooling unit according to claim 7, characterized in that: The step S23 further includes a step S24: Detect the electricity cost of the current stage. If the electricity cost of the current stage is high, control the DC cooling unit to raise the refrigeration start point and the refrigeration stop point; if the electricity cost of the current stage is low, control the DC cooling unit to lower the refrigeration start point and the refrigeration stop point.

9. The control terminal of a DC cooling unit according to claim 8, characterized in that: The step S24 specifically includes the following steps: Detecting the electricity cost of the current stage, if the electricity cost of the current stage is high, controlling the DC cooling unit to raise the refrigeration start point and refrigeration stop point by a preset level every preset time; If the electricity cost is low at the current stage, the DC cooling unit is controlled to reduce the refrigeration start point and the refrigeration stop point by a preset level every preset time.

10. The control terminal of a DC cooling unit according to claim 7, characterized in that: The step S2 further comprises the steps of: When the energy storage system is in an off-grid state, the energy storage battery is controlled to supply power to the DC cooling unit.

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