A multi-mode coordinated control method and device for a liquid cooling system

Abstract

This invention relates to the field of liquid cooling system control technology, and discloses a multi-mode coordinated control method and device for liquid cooling systems. The liquid cooling system includes a primary side liquid circuit, a secondary side liquid circuit, a primary side regulating valve, a secondary side circulating pump, sensors, a controller, and a human-machine interface module. The method collects the operating parameters of the liquid cooling system, determines the current control mode based on the mode selection command input by the human-machine interface module, adjusts the primary side regulating valve in temperature control mode, and adjusts the secondary side circulating pump in differential pressure control mode and flow control mode. When switching control modes, the actuator output value before the switch is read as the initial output value of the target control mode, and the controller state of the target control mode is initialized. The actuator output is updated according to a preset rate of change within a preset transition time. This invention can realize multi-mode coordinated control of liquid cooling systems and reduce abrupt changes in actuator output and system fluctuations during mode switching.

Description

Technical Field

[0001] This invention relates to the field of liquid cooling system control technology, and in particular to a multi-mode coordinated control method and device for liquid cooling systems, applicable to temperature control, differential pressure control, flow control, and mode coordinated switching of liquid cooling circulation systems under different operating conditions. Background Technology

[0002] Liquid cooling systems are widely used in energy storage systems, power electronic equipment, data centers, industrial equipment cooling, and other thermal management scenarios. With the expanding application scope of liquid cooling systems, higher requirements are being placed on the stability of supply water temperature, supply and return water pressure difference, and circulation flow rate during actual operation.

[0003] Existing liquid cooling systems typically achieve basic operational control through circulating pumps, regulating valves, and temperature, pressure, and flow sensors. In some applications, the liquid cooling system primarily uses the supply water temperature as the control objective; in others, the focus is more on the supply and return water pressure difference or the stability of the circulating flow rate. However, existing liquid cooling system control schemes are usually designed for a single control objective, making it difficult to simultaneously address different operational needs such as temperature control, pressure difference control, and flow control.

[0004] In addition, liquid cooling systems typically exhibit thermal inertia and dynamic hysteresis. When load conditions change, the supply water temperature is prone to slow response, long adjustment time, and delayed recovery. When the system needs to switch between different control modes, a lack of a reasonable mode switching coordination mechanism can easily lead to sudden changes in actuator output, causing system fluctuations and affecting the stable operation of the liquid cooling system.

[0005] Therefore, it is necessary to propose a multi-mode coordinated control method and device for liquid cooling systems to achieve stable operation of liquid cooling systems under different operating conditions and load conditions, and to reduce the impact on the system during the switching of different control modes. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-mode coordinated control method and device for a liquid cooling system, so as to realize the switching between temperature control, differential pressure control and flow control of the liquid cooling system, and reduce the sudden changes in actuator output and system fluctuations caused by mode switching and load changes.

[0007] The technical solution of the present invention: The liquid cooling system includes a primary side liquid circuit (1), a liquid cooling plate (2), a secondary side liquid circuit (6), a primary side regulating valve (3), a secondary side circulating pump (5), a secondary side water supply temperature sensor (8), a secondary side water supply pressure sensor (7), a secondary side return water pressure sensor (9), a flow sensor (10), a controller (4), and an MCGS touch screen (11).

[0008] The primary side regulating valve (3) is used to regulate the heat exchange capacity of the primary side liquid circuit (1); the liquid cooling plate (2) is used to realize heat exchange between the primary side liquid circuit (1) and the secondary side liquid circuit (6); the secondary side circulating pump (5) is used to regulate the secondary side circulation state; the secondary side water supply pressure sensor (7), the secondary side water supply temperature sensor (8), the secondary side water return pressure sensor (9), and the flow sensor (10) are used to collect the operating parameters of the liquid cooling system; the controller (4) is used to receive the collected parameters and perform multi-mode coordinated control; the MCGS touch screen (11) is used to input mode selection instructions, set control targets, and display the system operating status.

[0009] The main control modes of the liquid cooling system described in this invention include temperature control mode, differential pressure control mode, and flow control mode;

[0010] In the temperature control mode, the secondary side water supply temperature is used as the controlled variable, and temperature control is achieved by adjusting the opening of the primary side regulating valve (3); in the differential pressure control mode, the difference between the secondary side water supply pressure and the secondary side return water pressure is used as the controlled variable, and differential pressure control is achieved by adjusting the speed of the secondary side circulating pump (5); in the flow control mode, the secondary side flow rate is used as the controlled variable, and flow rate control is achieved by adjusting the speed of the secondary side circulating pump (5).

[0011] In some implementations, the system can also be set to a manual mode as a debugging mode, which is used to manually set the opening of the primary regulating valve and the speed of the secondary circulating pump.

[0012] The multi-mode coordinated control method for liquid cooling systems described in this invention includes the following steps:

[0013] Step 1: Collect the operating parameters of the liquid cooling system. The operating parameters include at least the secondary side supply water temperature, secondary side supply water pressure, secondary side return water pressure, secondary side flow rate, primary side regulating valve opening, and secondary side circulating pump speed.

[0014] Step 2: Determine the current control mode according to the mode selection command input by the MCGS touch screen (11). The current control mode includes temperature control mode, differential pressure control mode and flow control mode.

[0015] Step 3: When the current control mode is temperature control mode, the secondary side water supply temperature is used as the control target, and the opening of the primary side regulating valve (3) is adjusted according to the deviation between the secondary side water supply temperature and the target temperature.

[0016] Step 4: When the current control mode is differential pressure control mode, the difference between the secondary side supply water pressure and the secondary side return water pressure is used as the control target, and the speed of the secondary side circulation pump (5) is adjusted according to the deviation between the actual differential pressure and the target differential pressure.

[0017] Step 5: When the current control mode is flow control mode, the secondary side flow rate is used as the control target, and the speed of the secondary side circulation pump (5) is adjusted according to the deviation between the actual flow rate and the target flow rate.

[0018] Step 6: When the control mode is switched, read the current output value of the actuator corresponding to the target control mode before the switch, and use the current output value as the initial output value of the target control mode; when the actuator corresponding to the control mode before the switch is different from the actuator corresponding to the target control mode, keep the current output of the actuator corresponding to the control mode before the switch unchanged, or adjust it to the preset standby value according to the preset release change rate.

[0019] Step 7: Initialize the controller state of the target control mode, so that the initial output of the controller of the target control mode matches the initial output value, and update the actuator output of the target control mode according to the preset change rate within a preset transition time until the controlled variable corresponding to the target control mode enters the target range.

[0020] like Figure 2 As shown, the multi-mode coordinated control method for liquid cooling systems of the present invention includes steps such as parameter acquisition, mode determination, corresponding mode control, mode switching coordination processing, and cyclic execution.

[0021] The present invention also provides a multi-mode coordinated control device for a liquid cooling system, including a parameter acquisition module, a mode selection module, a temperature control module, a differential pressure control module, a flow control module, a mode switching coordination module, an actuator drive module, and a human-machine interaction module.

[0022] The parameter acquisition module is used to acquire the operating parameters of the liquid cooling system; the mode selection module is used to determine the current control mode according to the mode selection command input by the human-machine interaction module; the temperature control module, differential pressure control module, and flow control module are used to generate control signals in their respective control modes; the mode switching coordination module is used to read the current output value of the actuator corresponding to the target control mode before the switch when the control mode is switched, and use the current output value as the initial output value of the target control mode; when the actuator corresponding to the control mode before the switch is different from the actuator corresponding to the target control mode, the current output of the actuator corresponding to the control mode before the switch remains unchanged, or it is adjusted to a preset standby value according to a preset release change rate; the mode switching coordination module is also used to initialize the controller state of the target control mode, and update the actuator output in the target control mode according to a preset change rate within a preset transition time; the actuator drive module is used to drive the primary side regulating valve and the secondary side circulating pump; the human-machine interaction module is used for mode selection, target setting, and system status display.

[0023] like Figure 3As shown, the multi-mode coordinated control device for the liquid cooling system of the present invention includes a parameter acquisition module, a mode selection module, a temperature control module, a differential pressure control module, a flow control module, a mode switching coordination module, an actuator drive module, and a human-machine interaction module.

[0024] The present invention has the following beneficial effects:

[0025] 1. It can achieve secondary side water supply temperature control, secondary side supply and return water pressure difference control, and secondary side flow control in the same liquid cooling system.

[0026] 2. By using a primary-side regulating valve and a secondary-side circulating pump for separate regulation, mutual interference between different control objectives is reduced.

[0027] 3. During the control mode switching process, the actuator output abrupt changes and system fluctuations are reduced by inheriting the current output and updating the preset change rate.

[0028] 4. Under varying secondary load conditions, it can dynamically adjust based on key operating parameters, thereby improving the operational stability of the liquid cooling system. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the liquid cooling system structure of the present invention;

[0030] Figure 2 This is a flowchart of the multi-mode coordinated control method for the liquid cooling system of the present invention;

[0031] Figure 3 This is a block diagram of the multi-mode coordinated control device for the liquid cooling system of the present invention;

[0032] Figure 4 Here is a flowchart of the temperature control mode;

[0033] Figure 5 Here is a flowchart of the differential pressure control mode;

[0034] Figure 6 Flowchart of flow control mode;

[0035] Figure 7 Here is a flowchart for the mode switching coordination process; Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] like Figure 1As shown, a liquid cooling system includes a primary side liquid circuit (1), a liquid cooling plate (2), a primary side regulating valve (3), a controller (4), a secondary side circulating pump (5), a secondary side liquid circuit (6), a secondary side water supply pressure sensor (7), a secondary side water supply temperature sensor (8), a secondary side return water pressure sensor (9), a flow sensor (10), and an MCGS touch screen (11).

[0038] The primary side liquid path (1) is used to connect to the external cold source side or heat exchange side. The primary side regulating valve (3) is set in the primary side liquid path (1) to regulate the heat exchange capacity of the primary side liquid path (1). The liquid cooling plate (2) is set between the primary side liquid path (1) and the secondary side liquid path (6) to realize heat exchange between the primary side and the secondary side.

[0039] The secondary side liquid circuit (6) is used to supply circulating coolant to the load side. The secondary side circulation pump (5) is installed in the secondary side liquid circuit (6) to regulate the secondary side circulation flow rate and the secondary side circulation status. The secondary side liquid circuit (6) is equipped with a secondary side water supply pressure sensor (7), a secondary side water supply temperature sensor (8), a secondary side return water pressure sensor (9), and a flow sensor (10). Among them, the secondary side water supply pressure sensor (7) is used to collect the secondary side water supply pressure parameter, the secondary side water supply temperature sensor (8) is used to collect the secondary side water supply temperature parameter, the secondary side return water pressure sensor (9) is used to collect the secondary side return water pressure parameter, and the flow sensor (10) is used to collect the liquid cooling system flow rate parameter.

[0040] The controller (4) is connected to the primary regulating valve (3), the secondary circulating pump (5), the secondary water supply pressure sensor (7), the secondary water supply temperature sensor (8), the secondary return water pressure sensor (9), the flow sensor (10), and the MCGS touch screen (11) respectively, and is used to receive the operating parameters of the liquid cooling system and perform multi-mode coordinated control. The MCGS touch screen (11) is used to input mode selection commands, set control targets, and display the operating status of the liquid cooling system.

[0041] like Figure 4 As shown, in temperature control mode, the user sets the target temperature of the secondary water supply through the MCGS touch screen (11). The controller (4) collects the secondary water supply temperature and compares the actual temperature with the target temperature to obtain the temperature deviation.

[0042] The controller (4) generates a control signal for the primary side regulating valve (3) based on the temperature deviation, drives the primary side regulating valve (3) to change its opening, thereby adjusting the heat exchange capacity of the primary side and making the secondary side water supply temperature closer to the set value.

[0043] In this embodiment, when the secondary side load increases, the secondary side water supply temperature deviates from the target value, and the controller (4) increases the opening of the primary side regulating valve (3) according to the water supply temperature deviation; when the secondary side load decreases, the controller (4) decreases the opening of the primary side regulating valve (3).

[0044] like Figure 5 As shown, in differential pressure control mode, the user sets the target differential pressure between the secondary side supply and return water. The controller (4) collects the secondary side supply water pressure and the secondary side return water pressure respectively, and calculates the difference between the secondary side supply water pressure and the secondary side return water pressure as the actual differential pressure.

[0045] The controller (4) compares the actual pressure difference with the target pressure difference to obtain the pressure difference deviation, and adjusts the speed of the secondary side circulation pump 5 according to the pressure difference deviation so that the actual pressure difference is maintained within the target range.

[0046] like Figure 6 As shown, in flow control mode, the user sets the target flow rate on the secondary side. The controller (4) collects the actual flow rate on the secondary side and compares the actual flow rate with the target flow rate to obtain the flow deviation.

[0047] The controller (4) adjusts the speed of the secondary circulation pump (5) according to the flow deviation to stabilize the secondary flow within the target range.

[0048] like Figure 7 As shown, when the liquid cooling system receives a mode switching command input by the MCGS touch screen (11), the controller (4) first reads the current control mode and the current output value of the actuator corresponding to the target control mode before the switch. The current output value of the actuator corresponding to the target control mode includes the current opening degree of the primary side regulating valve (3) and / or the current speed of the secondary side circulating pump (5). After determining the target control mode, the controller (4) uses the current output value as the initial output value of the target control mode and initializes the controller state of the target control mode.

[0049] During mode switching, there are two scenarios: the control mode corresponds to the same actuator before and after the switch, and the control mode corresponds to a different actuator.

[0050] When switching between differential pressure control mode and flow control mode, since both use the secondary side circulation pump (5) as the actuator, the controller (4) reads the current speed of the secondary side circulation pump (5) before the switch as the initial output value of the target control mode.

[0051] When switching between temperature control mode and differential pressure control mode or flow control mode, since the primary side regulating valve (3) corresponding to temperature control mode and the secondary side circulating pump (5) corresponding to differential pressure control mode / flow control mode are different actuators, the controller (4) reads the current output value of the actuator corresponding to the target control mode before switching as the initial output value of the target control mode; at the same time, the output of the actuator corresponding to the exit mode is kept unchanged before switching, or gradually adjusted to the preset standby value according to the preset release change rate, so as to reduce the system fluctuation caused by the simultaneous large changes of the two actuators.

[0052] Similarly, when the system switches from differential pressure control mode or flow control mode to temperature control mode, the controller (4) reads the current opening degree of the primary side regulating valve (3) before the switch as the initial output value of the temperature control mode, and maintains the current output of the secondary side circulating pump (5) or adjusts it to the preset standby speed according to the preset release change rate.

[0053] The initialization includes at least one of the following: suppressing the integral term of the target control mode controller; resetting the integral term of the target control mode controller; and limiting the output range of the target control mode controller.

[0054] The purpose of initializing the controller state of the target control mode is to match the internal state of the controller when the target control mode is switched on with the inherited initial output value, thereby reducing the actuator output jump caused by sudden changes in the internal state of the controller.

[0055] Among them, when the operating points of the two control modes before and after switching are close and the deviation of the target control mode is small, the integral term of the target control mode controller can be suppressed, so that the target control mode first takes over by proportional adjustment or the previous state.

[0056] When the control objectives of the two control modes before and after switching are significantly different, or when the integral state before switching is no longer applicable to the target control mode, the integral term of the target control mode controller can be reset to zero, or reset to the initial integral value corresponding to the initial output value.

[0057] When the actuator approaches its upper or lower output limits, or when the system is sensitive to sudden changes in the actuator output, the output range of the target control mode controller can be limited, and a smooth transition can be achieved by combining the rate of change limit.

[0058] After completing the initial value inheritance and controller state initialization, the controller (4) gradually updates the actuator output in the target control mode according to the preset change rate within the preset transition time, so as to reduce the sudden change in valve opening or pump speed during the switching process.

[0059] The preset transition time and preset change rate can be fixed parameters that are pre-calibrated and stored in the controller (4) during the system debugging phase, or they can be determined online according to the operating status at the moment of switching.

[0060] In one embodiment, the controller (4) calculates the target output reference value u based on the target control mode and the current acquisition parameters and target setpoint. ref Based on the output difference Δu between the initial output value u0 and the target output reference value, and the maximum allowable rate of change of the corresponding actuator, the preset transition time T is determined. tr And the preset rate of change R.

[0061] The output difference Δu is calculated using the following formula: ;

[0062] For example, the transition time can be calculated using the following formula: ;

[0063] Among them, R set The pre-calibrated actuator change rate; when the calculated T tr When the transition time is less than the minimum transition time, the minimum transition time is used; when it is greater than the maximum transition time, the maximum transition time is used. The actual update rate R is then determined using the following formula: ;

[0064] For the primary-side regulating valve (3), the preset rate of change can be calibrated based on the valve's full stroke action time; for the secondary-side circulating pump (5), the preset rate of change can be calibrated based on the allowable slope of the circulating pump's rotational speed. For temperature control modes with high thermal inertia, the preset transition time can be set to be greater than that of differential pressure control modes and flow control modes to achieve a smoother transition effect.

[0065] Using the above method, the preset transition time and preset change rate can be adjusted according to the actuator specifications, liquid circuit volume, and dynamic response characteristics of liquid cooling systems of different scales.

[0066] When the controlled variable corresponding to the target control mode enters the target range, the system enters the normal control state under the target control mode.

[0067] For example, when the system switches from temperature control mode to differential pressure control mode, the controller (4) reads the current speed of the secondary side circulation pump (5) before the switch and uses the current speed as the initial output value of the differential pressure control mode. Then, the speed of the secondary side circulation pump (5) is gradually updated according to the deviation between the actual differential pressure and the target differential pressure until the difference between the secondary side supply water pressure and the secondary side return water pressure enters the target differential pressure range.

[0068] For example, when the system switches from differential pressure control mode to flow control mode, the controller (4) reads the current speed of the secondary side circulation pump (5) before the switch and uses the current speed as the initial output value of the flow control mode. Then, the speed of the secondary side circulation pump (5) is gradually updated according to the deviation between the actual flow and the target flow until the secondary side flow enters the target flow range.

[0069] During the operation of the liquid cooling system, changes in the secondary side load will cause variations in the secondary side supply water temperature, secondary side return water temperature, secondary side supply and return water pressure difference, or secondary side flow rate. Based on the current control mode and the deviation of the corresponding controlled variable, the controller dynamically adjusts the opening of the primary side regulating valve and / or the speed of the secondary side circulating pump 5 to improve the operational stability of the liquid cooling system under load disturbance conditions.

[0070] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A multi-mode coordinated control method for a liquid cooling system, characterized in that, Includes the following steps: Collect operating parameters of the liquid cooling system, including at least the secondary side supply water temperature, secondary side supply water pressure, secondary side return water pressure, secondary side flow rate, primary side regulating valve opening, and secondary side circulating pump speed. The current control mode is determined based on the mode selection command input by the human-machine interaction module. The current control mode includes temperature control mode, differential pressure control mode, and flow control mode. When the current control mode is temperature control mode, the secondary side water supply temperature is used as the control target, and the opening of the primary side regulating valve is adjusted according to the deviation between the secondary side water supply temperature and the target temperature. When the current control mode is differential pressure control mode, the difference between the secondary side supply water pressure and the secondary side return water pressure is used as the control target, and the speed of the secondary side circulation pump is adjusted according to the deviation between the actual differential pressure and the target differential pressure. When the current control mode is flow control mode, the secondary side flow rate is used as the control target, and the speed of the secondary side circulation pump is adjusted according to the deviation between the actual flow rate and the target flow rate. When the control mode is switched, the current output value of the actuator corresponding to the target control mode before the switch is read, and the current output value is used as the initial output value of the target control mode; When the actuator corresponding to the control mode before switching is different from the actuator corresponding to the target control mode, keep the current output of the actuator corresponding to the control mode before switching unchanged, or adjust it to the preset standby value according to the preset release change rate; The controller state of the target control mode is initialized so that the initial output of the controller of the target control mode matches the initial output value, and the actuator output of the target control mode is updated according to the preset rate of change within a preset transition time until the controlled variable corresponding to the target control mode enters the target range.

2. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, The operating parameters also include at least one of the following: primary side supply water temperature, primary side return water temperature, secondary side return water temperature, primary side supply water pressure, primary side return water pressure, and primary side flow rate.

3. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, In the temperature control mode, a control signal for the primary side regulating valve is generated based on the deviation between the secondary side supply water temperature and the target temperature, so as to change the heat exchange capacity of the primary side liquid circuit.

4. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, In the differential pressure control mode, the actual differential pressure is the difference between the secondary side supply water pressure and the secondary side return water pressure.

5. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, In the flow control mode, a secondary circulation pump control signal is generated based on the deviation between the secondary flow rate and the target flow rate.

6. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, The initialization of the controller state for the target control mode includes matching the initial output of the controller for the target control mode with the initial output value. The initialization specifically includes at least one of the following: Suppress the integral term of the target control mode controller; Reset the integral term of the target control mode controller; Limit the output range of the target control mode controller.

7. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, The step of updating the actuator output in the target control mode according to a preset rate of change within a preset transition time includes limiting the rate of change of the opening of the primary regulating valve and / or the rate of change of the rotational speed of the secondary circulating pump.

8. The multi-mode coordinated control method for a liquid cooling system according to claim 1, characterized in that, The controlled variable corresponding to the target control mode enters the target range, including: In temperature control mode, the secondary side water supply temperature enters the target temperature range; In differential pressure control mode, the difference between the secondary side supply water pressure and the secondary side return water pressure falls within the target differential pressure range; In flow control mode, secondary flow enters the target flow range.

9. A multi-mode coordinated control device for a liquid cooling system, characterized in that, include: The parameter acquisition module is used to acquire the operating parameters of the liquid cooling system. The operating parameters include at least the secondary side supply water temperature, secondary side supply water pressure, secondary side return water pressure, secondary side flow rate, primary side regulating valve opening, and secondary side circulating pump speed. The mode selection module is used to determine the current control mode according to the mode selection command input by the human-machine interaction module. The current control mode includes temperature control mode, differential pressure control mode and flow control mode. The temperature control module is used to generate a control signal for the primary side regulating valve based on the deviation between the secondary side supply water temperature and the target temperature in the temperature control mode. The differential pressure control module is used to generate a secondary circulation pump control signal in differential pressure control mode based on the deviation between the difference between the secondary side supply water pressure and the secondary side return water pressure and the target differential pressure. The flow control module is used to generate a secondary circulation pump control signal based on the deviation between the secondary flow rate and the target flow rate in flow control mode. The mode switching coordination module is used to read the current output value of the actuator corresponding to the target control mode before the switch when the control mode is switched, and use the current output value as the initial output value of the target control mode; When the actuator corresponding to the control mode before switching is different from the actuator corresponding to the target control mode, the current output of the actuator corresponding to the control mode before switching remains unchanged, or it is adjusted to the preset standby value according to the preset release change rate; the mode switching coordination module is also used to initialize the controller state of the target control mode, so that the initial output of the controller of the target control mode matches the initial output value, and update the actuator output in the target control mode according to the preset change rate within the preset transition time. An actuator drive module is used to drive the primary-side regulating valve and the secondary-side circulating pump according to the primary-side regulating valve control signal and the secondary-side circulating pump control signal. The human-machine interface module is used to input at least one of the following: mode selection command, target temperature, target pressure difference, and target flow rate, and to display the operating status of the liquid cooling system.

10. The multi-mode coordinated control device for a liquid cooling system according to claim 9, characterized in that, The operating parameters collected by the parameter acquisition module also include at least one of the following: primary side supply water temperature, primary side return water temperature, secondary side return water temperature, primary side supply water pressure, primary side return water pressure, and primary side flow rate. The mode switching coordination module is used to perform at least one of the following when switching control modes: suppressing the integral term of the target control mode controller; resetting the integral term of the target control mode controller; and limiting the output range of the target control mode controller. The mode switching coordination module is used to limit the rate of change of the opening of the primary side regulating valve and / or the rate of change of the speed of the secondary side circulating pump, so as to reduce the sudden change of the actuator output during the control mode switching process.

Images