A frequency converter control system for a water chiller

Abstract

This invention discloses a frequency converter control system for a chiller, relating to the field of frequency converter control technology for chillers. It aims to solve the problem of mismatch between speed regulation accuracy and cooling load in general-purpose systems. The system includes a frequency converter drive unit and a control signal unit. The frequency converter drive unit is electrically connected to a power input unit and an execution load unit, providing the execution load unit with variable frequency speed regulation power output. The power input unit is connected to three-phase AC power. The control signal unit is electrically connected to a sensing detection unit. The frequency converter drive unit includes a first frequency converter module and a second frequency converter module. The control signal unit provides start-up and speed regulation control signals to the first and second frequency converter modules. This frequency converter control system for a chiller enables precise frequency regulation of a deep-cooling chiller at -20℃, improving operational stability and cooling efficiency.

Description

Technical Field

[0001] This invention relates to the field of frequency converter control technology for water chillers, and more specifically to a frequency converter control system for water chillers. Background Technology

[0002] Deep-cooling chillers are widely used in the electronics, chemical, and precision manufacturing industries. Operating at -20℃ requires stringent stability and speed control accuracy for their refrigeration systems. Traditional chillers are mostly fixed-frequency controlled, resulting in high energy consumption and an inability to adjust cooling capacity according to load, leading to large temperature fluctuations and frequent start-ups and shutdowns. Some simplified variable-frequency chillers suffer from chaotic circuit topologies, significant signal interference, and inadequate protection mechanisms, making them prone to inverter module damage and motor overload failures under deep-cooling conditions, exhibiting poor adaptability and reliability. Furthermore, existing chiller variable-frequency control systems have low modularity, complex wiring, and are difficult to install, debug, and maintain. Dedicated variable-frequency control systems for 3600W deep-cooling chillers are scarce, and general-purpose systems suffer from speed control accuracy mismatch with cooling load, severely impacting chiller efficiency and lifespan.

[0003] Chinese patent CN121916615A discloses an industrial chiller and its control method. The main return water line is connected to a water distribution line via a three-way regulating valve. When the heat power input to the return water exceeds the maximum heat dissipation power of the compressor at its rated power, a portion of the return water can be diverted to a first water tank via the water distribution line. The refrigerant lines of the refrigeration equipment are connected to a refrigerant distribution line via a three-way regulating valve. When the minimum heat dissipation power of the compressor at its rated power exceeds the heat power input to the return water, a portion of the refrigerant can be diverted to the first water tank via the refrigerant distribution line. While this method can solve the problem of repeated power adjustments in the chiller, it cannot address the mismatch between speed regulation accuracy and refrigeration load in general-purpose systems. Summary of the Invention

[0004] This invention solves the problem of mismatch between speed regulation accuracy and cooling load in general-purpose systems. It proposes a frequency converter control system for chillers to achieve precise frequency conversion regulation of deep-cooling chillers under -20℃ conditions, thereby improving operational stability and cooling efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A variable frequency drive control system for a chiller includes a variable frequency drive unit and a control signal unit. The variable frequency drive unit is electrically connected to a power input unit and an execution load unit, respectively. The variable frequency drive unit provides variable frequency speed regulation power output to the execution load unit. The power input unit is connected to three-phase AC power. The control signal unit is electrically connected to a sensing and detection unit. The variable frequency drive unit includes a first variable frequency module and a second variable frequency module. The control signal unit provides start-up and speed regulation control signals to the first and second variable frequency modules.

[0007] This technical solution discloses a frequency converter control system for a chiller, applicable to a 3600W deep-cooling chiller (-20℃ operating condition). It includes a power input unit, a frequency converter drive unit, a control signal unit, a sensing and detection unit, and an execution load unit. The power input unit is connected to three-phase AC power, providing tiered power supply for the entire system. The frequency converter drive unit is electrically connected to the power input unit and the execution load unit, providing variable frequency speed control power output to the execution load unit. The control signal unit is electrically connected to the frequency converter drive unit and the sensing and detection unit, realizing signal acquisition, transmission, and the issuance of frequency converter drive commands.

[0008] The present invention is further configured such that: the input terminal of the first frequency converter module and the input terminal of the second frequency converter module are both connected to the power input unit, and the output terminal of the first frequency converter module and the output terminal of the second frequency converter module are both connected to the execution load unit.

[0009] In this technical solution, the first frequency converter module U1 and the second frequency converter module U2 are both dedicated chiller frequency converter modules. Their input terminals are connected to the branch terminals of the power input unit, and their output terminals output adjustable three-phase AC power through the U, V, and W three-phase interfaces.

[0010] The present invention is further configured such that: the execution load unit includes a plurality of three-phase motors, the three-phase motors are respectively connected to the frequency conversion drive unit, and the three-phase motors are equipped with PE grounding protection.

[0011] In this technical solution, the three-phase motor includes a first three-phase motor M1, a second three-phase motor M2, and a third three-phase motor M3. The three-phase motor serves as the power source for the chiller compressor and circulating pump. The speed is infinitely adjustable through a variable frequency drive unit to adapt to the needs of different cooling loads.

[0012] The present invention is further configured such that: the control signal unit includes a PCB control board and a signal interface module, the PCB control board integrates a +24V power supply terminal, a +10V reference voltage terminal and a GND ground terminal, and the signal interface module includes a digital interface and an analog interface.

[0013] In this technical solution, the PCB control board is the control core of the system, integrating a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal, providing stable power supply and signal reference for the sensing and detection unit and contactor.

[0014] The present invention is further configured such that the frequency conversion drive unit further includes a first contactor Q3 and a second contactor Q4, wherein the first contactor Q3 and the second contactor Q4 are connected together.

[0015] In this technical solution, the first contactor Q3 and the second contactor Q4 are electric heating drive modules, which have the functions of over-temperature protection and DC frequency regulation.

[0016] The present invention is further configured to include an electrical protection unit, which includes a circuit breaker F1, a residual current protection device ELB1, and a plurality of fuses. The circuit breaker F1 and the residual current protection device ELB1 are disposed in the main power supply circuit; the plurality of fuses are connected to each circuit of the frequency converter drive unit.

[0017] In this technical solution, the circuit breaker F1 and the residual current protection device ELB1 are installed in the main power supply circuit to realize the overload, short circuit and leakage protection of the main circuit, and quickly disconnect the main power supply in case of fault; the fuse can play the role of branch circuit overcurrent protection.

[0018] The present invention is further configured such that: the power input unit includes a three-phase power interface and a protective grounding terminal; the three-phase power interface is connected to a three-phase power supply; two phases of the three-phase power supply are used as L and N poles to supply power to the control signal unit and the contactor.

[0019] The present invention is further configured such that: the power input unit further includes a single-phase power interface, and the single-phase power interface is connected to a plurality of single-phase fans and transformers.

[0020] The present invention is further configured such that: the electrical protection unit further includes a system emergency stop switch, which is connected in series in the power supply circuit of the control signal unit.

[0021] In this technical solution, the emergency stop switch is connected in series in the power supply circuit of the control signal unit. In an emergency, the control circuit can be manually cut off to achieve emergency stop of the system.

[0022] The present invention is further configured such that: the sensing and detection unit includes a temperature sensor, the temperature sensor is disposed in the refrigeration chamber of the chiller, and the temperature sensor is connected to the PCB control board.

[0023] In this technical solution, the temperature sensor is installed in the refrigeration chamber of the chiller. The temperature sensor transmits the low temperature signal to the PCB control board, and the PCB control board adjusts the output frequency of the frequency converter drive unit according to the temperature deviation.

[0024] In addition, the status detection terminal collects the operating status of the three-phase motor M1 and transmits it to the PCB control board through the digital input interface DI1 to realize real-time status monitoring.

[0025] The frequency converter control system for a chiller of the present invention can bring the following beneficial effects: 1. The setting of the first and second frequency conversion modules realizes stepless speed regulation of the three-phase load of the chiller and linkage start and stop of the single-phase load. It can adjust the speed of the compressor and pump in real time according to the changes in the cooling load. Compared with the traditional fixed frequency control method, energy consumption is reduced by more than 20%, and the cooling temperature fluctuation is controlled within ±0.1℃, which greatly improves the cooling accuracy and energy saving of the deep cooling chiller under the condition of -20℃. 2. It is equipped with a complete sensing and detection unit, which realizes real-time detection of cooling temperature through temperature sensor, and collects the system operation status with digital status detection terminal to realize closed-loop control of cooling process. The control signal unit realizes efficient transmission of multiple types of signals through analog, digital and communication interfaces. The signal anti-interference ability is strong, the speed adjustment command response time is less than 0.5s, and the control accuracy is high. 3. Equipped with multi-level electrical protection units, the main circuit is equipped with circuit breakers and branch circuits are equipped with fuses. It is also equipped with emergency stop switches and grounding protection, which realizes rapid protection against various faults such as overcurrent, short circuit and leakage, and effectively avoids equipment failure under deep cooling conditions. 4. The system of the present invention integrates +24V and +10V graded power supply and multiple types of signal interfaces, which can flexibly adapt to different types of sensing and detection elements and execution loads, and has good expandability. Parameters can be adjusted and functions expanded according to actual cooling needs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the first part of the power supply of the inverter control system for a chiller according to the present invention.

[0027] Figure 2 This is a schematic diagram of the second part of the inverter control system of a chiller according to the present invention.

[0028] Figure 3 This is a schematic diagram of the third part of the inverter control system of a chiller according to the present invention.

[0029] Figure 4 This is an electrical system diagram of the frequency converter control system for a chiller according to the present invention. Detailed Implementation

[0030] Example 1

[0031] To address the mismatch between speed regulation accuracy and cooling load in general-purpose systems, this embodiment proposes a frequency converter control system for a chiller, referencing... Figure 1 , Figure 2 , Figure 3 and Figure 4 The system includes a frequency converter drive unit and a control signal unit. The frequency converter drive unit is connected to the power input unit and the load execution unit respectively. The frequency converter drive unit provides the load execution unit with variable frequency speed regulation power output. The power input unit is connected to three-phase AC power to provide tiered power supply for the entire system. The control signal unit is electrically connected to the sensing and detection unit. The frequency converter drive unit includes a first frequency converter module and a second frequency converter module. The control signal unit provides start-up and speed regulation control signals to the first frequency converter module and the second frequency converter module.

[0032] This technical solution discloses a frequency converter control system for a chiller, applicable to a 3600W deep-cooling chiller (-20℃ operating condition). It includes a power input unit, a frequency converter drive unit, a control signal unit, a sensing and detection unit, and an execution load unit. The power input unit is connected to three-phase AC power, providing tiered power supply for the entire system. The frequency converter drive unit is electrically connected to the power input unit and the execution load unit, providing variable frequency speed control power output to the execution load unit. The control signal unit is electrically connected to the frequency converter drive unit and the sensing and detection unit, realizing signal acquisition, transmission, and the issuance of frequency converter drive commands.

[0033] The input terminals of both the first and second frequency converter modules are connected to the power input unit, and the output terminals of both the first and second frequency converter modules are connected to the load unit.

[0034] The first frequency converter module U1 and the second frequency converter module U2 are both dedicated chiller frequency converter modules. Their input terminals are connected to the branch terminals of the power input unit, and their output terminals output adjustable three-phase AC power through the U, V, and W three-phase interfaces.

[0035] The load unit includes several three-phase motors, which are connected to the frequency converter drive unit. The three-phase motors are equipped with PE grounding protection.

[0036] The three-phase motors include a first three-phase motor M1, a second three-phase motor M2, and a third three-phase motor M3. These motors serve as the power source for the chiller compressor and circulating pump, and their speed is infinitely adjustable via a variable frequency drive unit to adapt to different cooling load requirements. All three-phase motors are equipped with PE grounding protection to prevent motor leakage faults.

[0037] In this embodiment, the first three-phase motor M1 drives the chiller compressor and achieves stepless speed regulation of 70-210Hz through the frequency conversion drive unit. The second three-phase motor M2 drives the refrigeration circulation pump and achieves stepless speed regulation of 40-60Hz through the frequency conversion drive unit. The speed is increased when the refrigeration load is large and decreased when the refrigeration load is small.

[0038] The control signal unit includes a PCB control board, a signal interface module, and a power supply module. The PCB control board integrates a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal. The signal interface module includes digital interfaces (DI1, DCOM) and analog interfaces (AI1, GND). The digital interfaces can acquire switch signals indicating the operating status of the chiller, while the analog interfaces can acquire continuous detection signals to achieve real-time adjustment of frequency converter parameters and feedback of operating status.

[0039] In this technical solution, the PCB control board is the control core of the system, integrating a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal, providing stable power supply and signal reference for the sensing and detection unit and contactor.

[0040] The frequency converter drive unit also includes a first contactor Q3 and a second contactor Q4, which are connected together.

[0041] The first contactor Q3 and the second contactor Q4 are the electric heating drive modules, which have the functions of over-temperature protection and DC frequency regulation.

[0042] The power input unit includes a three-phase power interface and a protective grounding terminal. The three-phase power interface is connected to a three-phase power supply, and two of the three phases of the power supply are used as L and N poles to supply power to the control signal unit and contactor.

[0043] In this technical solution, the three-phase power supply can provide power to the frequency converter module and the three-phase motor, and two of the phases are used as L and N poles to supply power to the control signal unit and contactor. The protective ground terminal (PE) is connected to the ground terminal of all electrical modules and motors to realize the overall grounding protection of the system and avoid static electricity and leakage faults.

[0044] In this embodiment, the three-phase power interface (3~M) is connected to 208V three-phase AC power to supply power to the first frequency converter module U1, the second frequency converter module U2, and the three-phase motors M1-M3.

[0045] The power input unit also includes a single-phase power interface, which is connected to several single-phase fans and transformers.

[0046] In this embodiment, the single-phase power interface (1~M) is connected to 208V single-phase AC power (N, L poles) to supply power to the single-phase fans M4-M6 and transformer T1; the protective grounding terminal (PE) is connected to the grounding terminals of all frequency converter modules, motors, and PCB control boards to realize system grounding protection.

[0047] The sensing and detection unit includes a temperature sensor, which is installed inside the refrigeration chamber of the chiller and connected to the PCB control board.

[0048] In this technical solution, the temperature sensor is installed in the refrigeration chamber of the chiller. The temperature sensor transmits the low temperature signal to the PCB control board, and the PCB control board adjusts the output frequency of the frequency converter drive unit according to the temperature deviation.

[0049] In addition, the status detection terminal collects the operating status of the three-phase motor M1 and transmits it to the PCB control board through the digital input interface DI1 to realize real-time status monitoring.

[0050] For the sensing and detection unit, the temperature sensor can transmit the low temperature signal to the PCB control board PCB1. The PCB control board PCB1 adjusts the output frequency of the frequency converter module according to the temperature deviation. The status detection end collects the operating status of the first three-phase motor M1 and transmits it to the PCB control board PCB1 through the digital interface DI1 to realize real-time status monitoring. Example 2

[0051] This embodiment proposes a frequency converter control system for a chiller, including a frequency converter drive unit and a control signal unit. The frequency converter drive unit is connected to a power input unit and an execution load unit, respectively. The frequency converter drive unit provides variable frequency speed regulation power output to the execution load unit. The power input unit is connected to three-phase AC power to provide tiered power supply for the entire system. The control signal unit is electrically connected to a sensing and detection unit. The frequency converter drive unit includes a first frequency converter module and a second frequency converter module. The control signal unit provides start-up and speed regulation control signals to the first frequency converter module and the second frequency converter module.

[0052] This technical solution discloses a frequency converter control system for a chiller, applicable to a 3600W deep-cooling chiller (-20℃ operating condition). It includes a power input unit, a frequency converter drive unit, a control signal unit, a sensing and detection unit, and an execution load unit. The power input unit is connected to three-phase AC power, providing tiered power supply for the entire system. The frequency converter drive unit is electrically connected to the power input unit and the execution load unit, providing variable frequency speed control power output to the execution load unit. The control signal unit is electrically connected to the frequency converter drive unit and the sensing and detection unit, realizing signal acquisition, transmission, and the issuance of frequency converter drive commands.

[0053] The input terminals of both the first and second frequency converter modules are connected to the power input unit, and the output terminals of both the first and second frequency converter modules are connected to the load unit.

[0054] The first frequency converter module U1 and the second frequency converter module U2 are both dedicated chiller frequency converter modules. Their input terminals are connected to the branch terminals of the power input unit, and their output terminals output adjustable three-phase AC power through the U, V, and W three-phase interfaces.

[0055] The load unit includes several three-phase motors, which are connected to the frequency converter drive unit. The three-phase motors are equipped with PE grounding protection.

[0056] The three-phase motors include a first three-phase motor M1, a second three-phase motor M2, and a third three-phase motor M3. These motors serve as the power source for the chiller compressor and circulating pump, and their speed is infinitely adjustable via a variable frequency drive unit to adapt to different cooling load requirements. All three-phase motors are equipped with PE grounding protection to prevent motor leakage faults.

[0057] The control signal unit includes a PCB control board, a signal interface module, and a power supply module. The PCB control board integrates a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal. The signal interface module includes digital interfaces (DI1, DCOM) and analog interfaces (AI1, GND). The digital interfaces can acquire switch signals indicating the operating status of the chiller, while the analog interfaces can acquire continuous detection signals to achieve real-time adjustment of frequency converter parameters and feedback of operating status.

[0058] In this technical solution, the PCB control board is the control core of the system, integrating a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal, providing stable power supply and signal reference for the sensing and detection unit and contactor.

[0059] The frequency converter drive unit also includes a first contactor Q3 and a second contactor Q4, which are connected together.

[0060] The first contactor Q3 and the second contactor Q4 are the electric heating drive modules, which have the functions of over-temperature protection and DC frequency regulation.

[0061] The power input unit includes a three-phase power interface and a protective grounding terminal. The three-phase power interface is connected to a three-phase power supply, and two of the three phases of the power supply are used as L and N poles to supply power to the control signal unit and contactor.

[0062] In this technical solution, the three-phase power supply can provide power to the frequency converter module and the three-phase motor, and two of the phases are used as L and N poles to supply power to the control signal unit and contactor. The protective ground terminal (PE) is connected to the ground terminal of all electrical modules and motors to realize the overall grounding protection of the system and avoid static electricity and leakage faults.

[0063] In this embodiment, the three-phase power interface (3~M) is connected to 208V three-phase AC power to supply power to the first frequency converter module U1, the second frequency converter module U2, and the three-phase motors M1-M3.

[0064] The power input unit also includes a single-phase power interface, which is connected to several single-phase fans and transformers.

[0065] In this embodiment, the single-phase power interface (1~M) is connected to 208V single-phase AC power (N, L poles) to supply power to the single-phase fans M4-M6 and transformer T1; the protective grounding terminal (PE) is connected to the grounding terminals of all frequency converter modules, motors, and PCB control boards to realize system grounding protection.

[0066] The sensing and detection unit includes a temperature sensor, which is installed inside the refrigeration chamber of the chiller and connected to the PCB control board.

[0067] In this technical solution, the temperature sensor is installed in the refrigeration chamber of the chiller. The temperature sensor transmits the low temperature signal to the PCB control board, and the PCB control board adjusts the output frequency of the frequency converter drive unit according to the temperature deviation.

[0068] In addition, the status detection terminal collects the operating status of the three-phase motor M1 and transmits it to the PCB control board through the digital input interface DI1 to realize real-time status monitoring.

[0069] Based on Embodiment 1, an electrical protection unit is also included. The electrical protection unit includes a circuit breaker F1, a residual current protection device ELB1, and several fuses. The circuit breaker F1 and the residual current protection device ELB1 are installed in the main power supply circuit; the several fuses are connected to each circuit of the frequency converter drive unit.

[0070] The electrical protection unit also includes a system emergency stop switch. The system emergency stop switch S1 is connected in series with the power supply circuit of the control signal unit. In an emergency, the control circuit can be manually cut off to achieve system emergency stop.

[0071] In this technical solution, circuit breaker F1 and residual current protection device ELB1 are installed in the main power supply circuit to realize overload, short circuit and leakage protection of the main circuit, and quickly disconnect the main power supply in case of fault; the fuse can play the role of branch circuit overcurrent protection. The emergency stop switch is connected in series in the power supply circuit of the control signal unit, and the control circuit can be manually cut off in an emergency to realize the emergency stop of the system.

[0072] More specifically, the electrical protection unit includes circuit breaker F1, residual current protection device ELB1, fuses F2-F4, and emergency stop switch S1; circuit breaker F1 and residual current protection device ELB1 can realize overload, short circuit and leakage protection of the main circuit, and quickly disconnect the main power supply in case of fault; fuses F2-F4 are connected in series in the power supply circuits of the first frequency converter module U1, the second frequency converter U2 and the contactor respectively to realize branch overcurrent protection and prevent single-circuit faults from spreading to the entire system.

[0073] refer to Figure 1 , Figure 2 as well as Figure 3 For the first frequency converter module U1, its input terminals R, S, and T are connected to the fuse F2, and its output terminals U, V, and W are connected to the input terminals of the first three-phase motor M1. For the second frequency converter module U2, its input terminals R, S, and T are connected to the fuse F3, and its output terminals U, V, and W are connected to the input terminals of the second three-phase motor M2. The second, third, fourth, and sixth pins of the first frequency converter module U1 can be connected to the PCB control board PCB1. The PCB control board PCB1 provides speed control signals to the first frequency converter module U1 and the second frequency converter module U2 to realize the frequency conversion speed regulation of the motor.

[0074] In this embodiment, the PCB control board PCB1 can provide power to the temperature sensor and contactor group of the sensing and detection unit.

[0075] For the sensing and detection unit, the temperature sensor is installed in the refrigeration chamber of the chiller. The temperature sensor transmits the low temperature signal to the PCB control board PCB1. The PCB control board PCB1 adjusts the output frequency of the frequency converter module according to the temperature deviation. The status detection end collects the operating status of the first three-phase motor M1 and transmits it to the PCB control board PCB1 through the digital input interface DI1 to realize real-time status monitoring.

[0076] The first three-phase motor, M1, drives the chiller compressor, achieving stepless speed regulation from 70-210Hz via a variable frequency drive unit, responsible for significantly adjusting the cooling capacity. The second three-phase motor, M2, drives the refrigeration circulation pump, achieving stepless speed regulation from 40-60Hz via a variable frequency drive unit, responsible for matching water flow and load changes; increasing the speed when the cooling load is high and decreasing the speed when the cooling load is low. Through the stepless speed regulation of the variable frequency drive unit, the motor power can match the load demand in real time, avoiding the energy waste of "overpowered motors" or frequent start-stop operations under traditional power frequency operation, significantly improving the overall energy efficiency ratio. At the same time, smooth speed regulation also makes water temperature control more stable, and the system operation quieter and more reliable.

[0077] In this embodiment, circuit breaker ELB1 is installed in the main three-phase power supply circuit and automatically disconnects when the circuit current exceeds the rated value; fuses F2 and F3 are connected in series in the power supply circuits of the first frequency converter module U1 and the second frequency converter module U2, respectively, and fuse F4 is connected in series in the power supply circuit of the contactor group to realize branch overcurrent protection; switch S1 is an emergency stop switch, which cuts off the +24V power supply to the PCB control board when pressed, and the system shuts down in an emergency.

[0078] The above-described solution in this embodiment relates to a frequency converter control system that is adapted to deep-cooling chillers, features a modular layout, precise control, and comprehensive protection. This system can solve the problems of high energy consumption, poor adaptability, complex circuitry, and inadequate protection in traditional chillers with fixed-frequency control. It enables precise frequency conversion regulation of deep-cooling chillers under -20℃ operating conditions, thereby improving operational stability and cooling efficiency.

[0079] In this embodiment, the frequency converter control system is applied to a 3600W deep-cooling chiller. The chiller's cooling temperature fluctuation at -20℃ is controlled within ±0.8℃. The compressor's energy consumption is reduced by 25% compared to traditional fixed-frequency control. The system runs continuously for 3000 hours without failure, and its operational stability and cooling efficiency are greatly improved.

[0080] The technical solution of this embodiment can bring about the following technical effects.

[0081] 1. This embodiment uses the first frequency conversion module U1 and the second frequency conversion module U2 for frequency conversion drive, realizing stepless speed regulation of the three-phase load of the chiller and linkage start and stop of the single-phase load. It can adjust the speed of the compressor and pump in real time according to the changes in the cooling load. Compared with the traditional fixed frequency control method, energy consumption is reduced by more than 20%, and the cooling temperature fluctuation is controlled within ±0.1℃, which greatly improves the cooling accuracy and energy saving of the deep cooling chiller under the condition of -20℃.

[0082] 2. This embodiment is equipped with a complete sensing and detection unit. The temperature sensor realizes real-time detection of the cooling temperature. In conjunction with the digital status detection terminal to collect the system operation status, the closed-loop control of the cooling process is realized. The control signal unit realizes efficient transmission of multiple types of signals through analog, digital and communication interfaces. The signal anti-interference capability is strong, the speed regulation command response time is less than 0.5s, and the control accuracy is high.

[0083] 3. This embodiment is equipped with a multi-level electrical protection unit, with a circuit breaker in the main circuit and fuses in the branch circuits. It is also equipped with an emergency stop switch and grounding protection, which realizes rapid protection against various faults such as overcurrent, short circuit and leakage, effectively avoiding equipment failure under deep cooling conditions, and improving the system's operational stability and service life.

[0084] 4. The control system in this embodiment integrates +24V and +10V graded power supply and multiple types of signal interfaces, which can flexibly adapt to different types of sensing and detection elements and execution loads. It has good expandability and can adjust parameters and expand functions according to actual cooling needs. It is suitable for various specifications of deep-cooling chillers.

Claims

1. A frequency converter control system for a chiller, characterized in that, The system includes a variable frequency drive unit and a control signal unit. The variable frequency drive unit is electrically connected to a power input unit and an execution load unit, respectively. The variable frequency drive unit provides variable frequency speed regulation power output to the execution load unit. The power input unit is connected to three-phase AC power. The control signal unit is electrically connected to a sensing and detection unit. The variable frequency drive unit includes a first variable frequency module and a second variable frequency module. The control signal unit provides start-up and speed regulation control signals to the first variable frequency module and the second variable frequency module.

2. The inverter control system of a water chiller according to claim 1, wherein, The input terminals of the first frequency converter module and the second frequency converter module are both connected to the power input unit, and the output terminals of the first frequency converter module and the second frequency converter module are both connected to the execution load unit.

3. A variable frequency drive control system for a water chiller as defined in claim 1 or 2, wherein, The execution load unit includes several three-phase motors, each of which is connected to a frequency converter drive unit and is equipped with PE grounding protection.

4. The inverter control system for a chiller according to claim 1 or 2, characterized in that, The control signal unit includes a PCB control board and a signal interface module. The PCB control board integrates a +24V power supply terminal, a +10V reference voltage terminal, and a GND ground terminal. The signal interface module includes a digital interface and an analog interface.

5. A variable frequency drive control system for a water chiller as defined in Claim 1 or 2, wherein The frequency conversion drive unit also includes a first contactor Q3 and a second contactor Q4, which are connected together.

6. The inverter control system of a water chiller according to claim 1, wherein, It also includes an electrical protection unit, which includes a circuit breaker F1, a residual current protection device ELB1, and several fuses. The circuit breaker F1 and the residual current protection device ELB1 are installed in the main power supply circuit; the several fuses are connected to each circuit of the frequency converter drive unit.

7. A variable frequency drive control system for a water chiller as set forth in claim 5, wherein, The power input unit includes a three-phase power interface and a protective grounding terminal. The three-phase power interface is connected to a three-phase power supply, and two phases of the three-phase power supply are used as L and N poles to supply power to the control signal unit and contactor.

8. A variable frequency drive control system for a water chiller as set forth in claim 7, wherein, The power input unit also includes a single-phase power interface, which is connected to several single-phase fans and transformers.

9. The inverter control system of a water chiller according to claim 6, wherein, The electrical protection unit also includes a system emergency stop switch, which is connected in series in the power supply circuit of the control signal unit.

10. The inverter control system of a water chiller according to claim 4, wherein, The sensing and detection unit includes a temperature sensor, which is installed inside the refrigeration chamber of the chiller and connected to the PCB control board.

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