Simulation test system and method for control unit of cold box frequency conversion unit

Abstract

The invention discloses a simulation test system and method for a control unit of a cold box frequency conversion unit. The simulation test system comprises a test board panel, a programmable logic controller, a mode switching relay and a simulation load circuit, an adjustable potentiometer knob is mounted on the test bench panel; the programmable logic controller is used for outputting a corresponding direct-current voltage signal according to a received set value in a PC setting mode; the mode switching relay is controlled by the programmable logic controller and is used for switching between a signal output by the adjustable potentiometer knob and a direct-current voltage signal output by the programmable logic controller and outputting a selected signal to an external control unit to be tested; the analog load circuit comprises a star-connected three-phase resistor and a star-connected capacitor bank. According to the invention, a virtual test environment which can be separated from a real machine and is safe and flexible is constructed for a real control unit, and efficient and low-cost maintenance test and function verification are realized.

Description

Technical Field

[0001] This invention relates to the field of simulation testing technology for cold box inverter units, and in particular to a simulation testing system and method for the control unit of a cold box inverter unit. Background Technology

[0002] In the cold chain logistics industry, refrigerated containers are the core equipment for ensuring the quality of goods such as fresh produce and pharmaceuticals. The core variable frequency refrigeration unit (Daikin variable frequency unit) is precisely regulated through a complex control system consisting of multiple control units such as EC1 (CPU board), EC2 (I / O board), EC7 (PT / CT board), and EC8 (inverter main circuit board). Its reliability is directly related to transportation safety.

[0003] When a unit malfunctions, the core task is to quickly locate and replace the damaged control unit. Currently, the main maintenance and testing method is to reinstall the control unit under test back onto the actual refrigerated container unit, connect it to the actual compressor, condenser fan, evaporator fan, refrigerant piping and a full set of sensors, and conduct a full-unit power-on operation test. Although this can ultimately verify the function of the control unit, it relies on a complete, running physical unit as the test platform.

[0004] However, existing maintenance and testing technologies have significant bottlenecks. Current testing relies on relatively expensive complete refrigerated container units, resulting in high equipment occupancy, low testing efficiency, and time-consuming processes. Each test requires complex mechanical and piping connections, leading to cumbersome preparation. Furthermore, existing testing methods have poor safety performance and high risks. Testing must be conducted in real high-pressure, high-current, and complex refrigeration systems containing refrigerant, posing risks such as electric shock, mechanical injury, and refrigerant leakage, and demanding extremely high levels of expertise from maintenance personnel. Therefore, there is an urgent need for a low-cost, safe, and highly efficient simulation testing system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a simulation testing system and method for the control unit of a cold box inverter unit. By using an adjustable potentiometer and a programmable logic controller to simulate sensor signals, and in conjunction with a star-connected resistor / capacitor to simulate the load, a safe and flexible virtual testing environment is constructed for the real control unit, which can be separated from the actual machine, thus achieving efficient and low-cost maintenance testing and functional verification.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a simulation test system for a control unit of a cold box inverter unit, which is connected to an external control unit under test via a connection interface, and includes: a test bench panel, a programmable logic controller, a mode switching relay, and a simulated load circuit; The test bench panel is equipped with an adjustable potentiometer knob for simulating sensor parameters. The programmable logic controller is used to output a corresponding DC voltage signal according to the received set value in PC setting mode; The mode switching relay is controlled by a programmable logic controller (PLC) and is used to switch between the signal output by the adjustable potentiometer knob and the DC voltage signal output by the PLC, and output the selected signal to the external control unit to be tested. The simulated load circuit includes a star-connected three-phase resistor for connecting to the output of the frequency converter to simulate the compressor load, and a star-connected capacitor bank for connecting to a contactor to simulate the fan motor windings.

[0007] As a further technical solution, a status indicator array is also included; the status indicator array includes a fan status indicator and a stepper valve status indicator, the status indicator array is installed on the test bench panel, and the status indicator array is controlled by the programmable logic controller to display according to the system status.

[0008] As a further technical solution, the fan status indicator light consists of multiple sets of fan blade-shaped LEDs arranged symmetrically around the circumference. The driving end of each set of fan blade-shaped LEDs is connected to different output ports of the programmable logic controller, and the programmable logic controller lights them up sequentially through program control to form a rotating visual effect.

[0009] As a further technical solution, the stepper valve status indicator uses multiple LEDs to simulate the windings of each phase of the stepper motor; the LEDs adopt a common anode connection, with their cathode side directly connected to the stepper valve negative pulse output interface of the external control unit EC1 board through a connection interface, and their anode side connected in series with a current-limiting resistor and connected to the EC1 board through a connection interface.

[0010] As a further technical solution, the common terminal of the mode switching relay is connected to the interface for connecting the sensor input of the external control unit to be tested, its normally closed contact is connected to the output of the adjustable potentiometer knob, and its normally open contact is connected to the corresponding output terminal of the programmable logic controller.

[0011] As a further technical solution, the simulated load circuit also includes a current sensor, which is connected in series in the power supply circuit of the star-connected three-phase resistor to detect the operating current of the simulated compressor, and its signal output terminal is connected to the programmable logic controller.

[0012] As a further technical solution, a contactor controlled by an external control unit is connected in series in the power supply circuit of the star-connected capacitor bank, and the auxiliary contact status signal of the contactor is input to the programmable logic controller.

[0013] As a further technical solution, the external control unit under test includes the EC8 inverter main circuit board, and the three independent terminals of the star-connected three-phase resistor are connected to the three-phase output terminals of the EC8 inverter main circuit board through a connection interface.

[0014] Secondly, the present invention provides a simulation testing method for a control unit of a cold box inverter unit, based on a simulation testing system for a control unit of a cold box inverter unit as described in any one of the first aspects, comprising: Connect the external control unit under test to the simulation test system; The DC voltage signal representing the sensor parameters is generated by adjusting the adjustable potentiometer knob or setting it through the PC setting mode of the programmable logic controller, and then input to the external control unit to be measured. Observe the response status of the external control unit under test to the DC voltage signal using the status indicator array on the test bench panel. Also, read the operating parameters and status information output by the external control unit under test. Based on the response status and operating parameters and status information, determine whether the function of the external control unit under test is normal.

[0015] As a further technical solution, the setting via the PC setting mode of the programmable logic controller is specifically as follows: Input the sensor parameter settings to be simulated and transmit them to the programmable logic controller (PLC). The PLC performs range transformation calculations on the sensor parameter settings based on the pre-stored sensor characteristic model and outputs a DC voltage signal corresponding to the sensor parameter settings. The mode switching relay driven by the programmable logic controller (PLC) is controlled to switch the DC voltage signal output by the PLC and connect it to the corresponding sensor input interface of the external control unit under test.

[0016] One or more technical solutions of the present invention have the following beneficial effects: This invention achieves virtualization and independence of the testing environment, fundamentally solving the dependence on real units. It abandons the traditional testing mode that relies on real compressors, fans, and refrigerant piping. By simulating load circuits (composed of star-connected three-phase resistors and star-connected capacitor banks), it simulates compressor and fan loads respectively. This allows it to safely receive and consume the drive power output from the control unit, ensuring its normal operation. Combined with the simulated sensor signals provided by the adjustable potentiometer knob and programmable logic controller, it constructs a complete "virtual machine" environment that can operate independently in a repair shop for externally connected real control units. This directly solves core problems such as high testing costs, equipment occupation, and poor security, enabling testing to be conducted at any time under safe, quiet, and low-energy conditions. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the framework of a simulation test system for a cold box inverter unit control unit according to the present invention; Figure 2 This invention relates to the control circuit for the fan status indicator light; Figure 3 This invention relates to the control circuit for the stepper valve status indicator light. Figure 4 This is a schematic diagram of the simulated load circuit of the present invention. Detailed Implementation

[0019] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] Example 1 like Figure 1 As shown, this embodiment provides a simulation test system for the control unit of a refrigerated container inverter unit. It is an independent test bench, whose core function is to build a virtual operating environment for the actual refrigerated container unit control unit. It is connected to the external control unit under test through a connection interface. Specifically, the simulation test system of this embodiment includes: a test bench panel, a programmable logic controller, a mode switching relay, a simulated load circuit, and a status indicator array.

[0021] In this embodiment, the test bench panel is equipped with a simulation operation area, which contains multiple sets of adjustable potentiometer knobs for simulating sensor parameters, such as SS, RS, LPT, HPT, HUS, and FAS sensors for temperature, pressure, humidity, and vent opening. Specifically, 100KΩ adjustable potentiometer knobs are used to simulate the temperature sensors DCHS1 and DCHS2, while 50KΩ adjustable potentiometer knobs are used for the other temperature sensors; 10KΩ adjustable potentiometer knobs are used to simulate the pressure, humidity, and vent opening sensors. The test bench panel also includes a simulation display area for mounting an array of status indicator lights.

[0022] In this embodiment, the status indicator array is controlled by a programmable logic controller (PLC) according to the system status. The status indicator array includes a fan status indicator and a stepper valve status indicator. The fan status indicator consists of multiple sets of fan blade-shaped LEDs arranged symmetrically around the circumference. The driving end of each set of fan blade-shaped LEDs is connected to different output ports of the PLC, and the PLC controls them to light up sequentially to form a rotating visual effect.

[0023] like Figure 2 As shown, taking the EF indicator light as an example, it consists of nine fan-shaped LEDs arranged symmetrically along the circumference, in groups of three, for a total of three groups. The driver terminals of the three groups of fan-shaped LEDs are connected to three output points Q0.0, Q0.1, and Q0.2 of the programmable logic controller (PLC). The PLC controls these three outputs to be sequentially high-level through program control, creating the visual effect of fan blades rotating. The switching is fast at high speeds and slow at low speeds.

[0024] The stepper valve status indicator uses multiple LEDs to simulate the windings of each phase of the stepper motor. The LEDs are connected in a common anode configuration. Their cathode side is directly connected to the stepper valve negative pulse output interface of the external control unit EC1 board through a connection interface. Their anode side is connected in series with a current-limiting resistor and connected to the EC1 board through a connection interface.

[0025] like Figure 3 As shown, taking the EEV valve as an example, four LEDs (LED1-LED4) are used to simulate its four-phase winding. The anodes of the four LEDs are connected together, and after being connected in series with a 4.7KΩ current-limiting resistor R, they are connected to the +V power supply provided by the external EC1 board. The cathodes of the four LEDs are directly connected to the four-phase negative pulse output interface (A-, B-, C-, D-) of the EEV valve on the EC1 board through the connection interface. When the EC1 board drives the EEV switch, its output pulse sequence will light up LED1-LED4 in sequence, forming a clockwise or counterclockwise rotation effect.

[0026] In this embodiment, the programmable logic controller (PLC) is a single PLC (e.g., Siemens S7-1200 series), installed inside the test bench enclosure. This PLC is connected to a touchscreen computer (equipped with an HMI interface such as Sensor & Parameter SET) to receive sensor parameter settings from the PC setting mode and perform signal conversion.

[0027] The mode switching relay is controlled by a programmable logic controller (PLC) to switch between the signal output by the adjustable potentiometer knob and the DC voltage signal output by the PLC. The selected signal is output to an external control unit under test. The common terminal of the mode switching relay is connected to an interface for connecting the sensor input of the external control unit under test. Its normally closed contact is connected to the output of the adjustable potentiometer knob, and its normally open contact is connected to the corresponding output terminal of the PLC.

[0028] In this embodiment, multiple general-purpose relays are used and mounted on a circuit board inside the enclosure. Taking the DRS sensor circuit as an example, the common terminal of the relay is connected to terminal XC1 of the X16A interface used to connect to the external EC1 board; its normally closed contact is connected to the sliding terminal output of the 50KΩ adjustable potentiometer on the panel; and its normally open contact is connected to the corresponding channel of the PLC analog output module. The HPT sensor circuit is similar. All sensor mode switching relays are uniformly controlled by the PLC's digital output points.

[0029] In this embodiment, the external control unit to be tested includes the EC8 inverter main circuit board, and the three independent terminals of the star-connected three-phase resistor are connected to the three-phase output terminals of the EC8 inverter main circuit board through the connection interface.

[0030] The simulated load circuit includes a star-connected three-phase resistor for connecting to the inverter output to simulate a compressor load, a star-connected capacitor bank for connecting a contactor to simulate a fan motor winding, and a current sensor. The power supply circuit of the star-connected capacitor bank contains a contactor controlled by an external control unit under test, and the auxiliary contact status signal of the contactor is input to the programmable logic controller.

[0031] In this embodiment, a current sensor is connected in series in the power supply circuit of the star-connected three-phase resistor to detect the operating current of the simulated compressor, and its signal output terminal is connected to the programmable logic controller.

[0032] In other words, the simulated load circuit in this embodiment includes a compressor simulated load and a fan simulated load; wherein, the compressor simulated load: It consists of three 200Ω high-power resistors of the same resistance connected in a star configuration. Their three independent terminals are connected to the three-phase output terminals (U, V, W) of the external EC8 inverter main circuit board via a test bench interface (such as a three-phase terminal block). A current sensor (such as CT1) is connected in series in this circuit to detect the simulated operating current; its signal output is connected to the analog input channel of the PLC.

[0033] Simulated load on the wind turbine: Multiple sets of capacitors are used in a star connection. Taking the evaporator fan as an example, its high-speed winding is simulated by three 20μF capacitors (C11, C12, C13) connected in a star connection, and its low-speed winding is simulated by three 10μF capacitors connected in a star connection. The three independent terminals of each set of capacitors are connected to the three-phase power supply through the main contacts of contactor EFH (high speed) or EFL (low speed). The coils of contactors EFH and EFL are controlled by an external EC2I / O board. The normally open auxiliary contacts of contactors EFH and EFL are connected to the PLC's digital input channel for status feedback.

[0034] Example 2 This embodiment provides a simulation test method for the control unit of a cold box inverter unit, which is based on the simulation test system for the control unit of a cold box inverter unit provided in Embodiment 1. Taking the test of the EC2I / O board as an example, the specific steps include the following: S1: Connect the external control unit under test to the simulation test system; S2: Adjustable via the adjustable potentiometer knob or set via the PC setting mode of the programmable logic controller to generate a DC voltage signal representing the sensor parameters and input the DC voltage signal to the external control unit to be measured; S3: Observe the response status of the external control unit under test to the DC voltage signal through the status indicator array on the test bench panel. Also, read the operating parameters and status information output by the external control unit under test. S4: Based on the response status and operating parameters and status information, determine whether the function of the external control unit under test is normal.

[0035] In step S1, the EC2 board to be tested, the EC1 board, the EC7 board, and the EC8 board in normal condition are connected to the corresponding interfaces of the test system through connecting cables, and the controller operation display unit fixed on the right side of the test bench panel is used as the human-machine interface.

[0036] In step S2, a signal is injected. There are two types of injected signals: one is manual knob adjustment, and the other is PC setting mode. Manual knob adjustment is as follows: after the system is powered on, it is in the panel knob mode by default. The maintenance personnel manually rotate the 50KΩ knob simulating RS (return air temperature) clockwise, which is equivalent to inputting a simulated signal of increased return air temperature into the EC1 board. To switch to PC setup mode, click the PC SET button on the touchscreen interface. In the HPT (High Voltage Sensor) input box, enter 3000 (in kPa) using the soft keyboard and press ENTER. This value 3000 is transmitted to the PLC. The PLC has a pre-stored transformation model for the HPT sensor (e.g., a range of 0~3500 kPa corresponds to an output voltage of 0.5~4.5V). After calculation, the PLC outputs a DC voltage of approximately 3.86V from the corresponding analog output channel. This 3.86V voltage signal (not the panel knob signal) is connected to the X7A interface of the EC1 board, simulating a high voltage over-limit fault condition.

[0037] In other words, it is set through the PC setting mode of the programmable logic controller, specifically as follows: Input the sensor parameter settings to be simulated and transmit them to the programmable logic controller (PLC). The PLC performs range transformation calculations on the sensor parameter settings based on the pre-stored sensor characteristic model and outputs a DC voltage signal corresponding to the sensor parameter settings. The mode switching relay driven by the programmable logic controller (PLC) is controlled to switch the DC voltage signal output by the PLC and connect it to the corresponding sensor input interface of the external control unit under test.

[0038] In step S3, observe the status indicator array on the test panel. Due to the injected RS rise signal, the controller may enter cooling mode. Observe that the CP (compressor) indicator light should be on, and the EF and CF fan rotation LEDs should start rotating. Due to the injected HPT over-limit fault signal, observe that after a short delay, the CP, EF, CF, and other load indicator lights should turn off, indicating a protective shutdown.

[0039] Read controller information: Simultaneously, observe the LCD screen of the fixed operation display unit on the right. After injecting the HPT over-limit signal, the screen should display a corresponding "High Voltage Sensor Fault" or similar alarm code. Detailed fault records and system status parameters can also be viewed on the monitoring interface of the DCCS software launched via the touchscreen.

[0040] In step S4, based on the response status and operating parameters and status information, it is determined whether the function of the external control unit under test is normal, specifically: If the EC2 board drives loads such as CP, EF, and CF (manifested by the corresponding indicator lights), and correctly disconnects these loads after receiving the HPT fault signal (manifested by the indicator lights going out), and the controller display correctly reports the fault code, then it can be determined that the output drive channel of the EC2 board, the logic linkage with the EC1 board, and the fault protection function of the system are basically normal.

[0041] If the load indicator light does not operate as expected, or fails to disconnect the load during a fault, or the display screen does not provide a correct alarm, it can be preliminarily determined that there is a fault in the corresponding function of the EC2 board, and further inspection is required.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A simulation test system for the control unit of a cold box inverter unit, which connects to an external control unit under test via a connection interface, characterized in that, include: Test bench panel, programmable logic controller, mode switching relay and analog load circuit; The test bench panel is equipped with an adjustable potentiometer knob for simulating sensor parameters. The programmable logic controller is used to output a corresponding DC voltage signal according to the received set value in PC setting mode; The mode switching relay is controlled by a programmable logic controller (PLC) and is used to switch between the signal output by the adjustable potentiometer knob and the DC voltage signal output by the PLC, and output the selected signal to the external control unit to be tested. The simulated load circuit includes a star-connected three-phase resistor for connecting to the output of the frequency converter to simulate the compressor load, and a star-connected capacitor bank for connecting to a contactor to simulate the fan motor windings.

2. The simulation test system for the control unit of a cold box inverter unit as described in claim 1, characterized in that, It also includes a status indicator array; the status indicator array includes a fan status indicator and a stepper valve status indicator. The status indicator array is mounted on the test bench panel, and the status indicator array is controlled by the programmable logic controller to display according to the system status.

3. The simulation test system for the control unit of a cold box inverter unit as described in claim 2, characterized in that, The fan status indicator consists of multiple sets of fan blade-shaped LEDs arranged symmetrically around the circumference. The driving end of each set of fan blade-shaped LEDs is connected to different output ports of the programmable logic controller (PLC), and the PLC controls them to light up sequentially to create a rotating visual effect.

4. The simulation test system for the control unit of a cold box inverter unit as described in claim 2, characterized in that, The stepper valve status indicator uses multiple LEDs to simulate the windings of each phase of the stepper motor. The LEDs are connected in a common anode configuration. Their cathode side is directly connected to the stepper valve negative pulse output interface of the external control unit EC1 board through a connection interface, and their anode side is connected in series with a current-limiting resistor and connected to the EC1 board through a connection interface.

5. The simulation test system for the control unit of a cold box inverter unit as described in claim 1, characterized in that, The common terminal of the mode switching relay is connected to the interface for connecting the sensor input of the external control unit to be tested. Its normally closed contact is connected to the output of the adjustable potentiometer knob, and its normally open contact is connected to the corresponding output terminal of the programmable logic controller.

6. The simulation test system for the control unit of a cold box inverter unit as described in claim 1, characterized in that, The analog load circuit also includes a current sensor, which is connected in series in the power supply circuit of the star-connected three-phase resistor to detect the operating current of the analog compressor. Its signal output terminal is connected to the programmable logic controller.

7. The simulation test system for the control unit of a cold box inverter unit as described in claim 1, characterized in that, A contactor controlled by an external control unit under test is connected in series in the power supply circuit of the star-connected capacitor bank, and the auxiliary contact status signal of the contactor is input to the programmable logic controller.

8. The simulation test system for the control unit of a cold box inverter unit as described in claim 1, characterized in that, The external control unit under test includes the EC8 inverter main circuit board, and the three independent terminals of the star-connected three-phase resistor are connected to the three-phase output terminals of the EC8 inverter main circuit board through a connection interface.

9. A simulation test method for a control unit of a cold box inverter unit, based on the simulation test system for a control unit of a cold box inverter unit as described in any one of claims 1-8, characterized in that, include: Connect the external control unit under test to the simulation test system; The DC voltage signal representing the sensor parameters is generated by adjusting the adjustable potentiometer knob or setting it through the PC setting mode of the programmable logic controller, and then input to the external control unit to be measured. Observe the response status of the external control unit under test to the DC voltage signal using the status indicator array on the test bench panel. Also, read the operating parameters and status information output by the external control unit under test. Based on the response status and operating parameters and status information, determine whether the function of the external control unit under test is normal.

10. The simulation test method for the control unit of a cold box inverter unit as described in claim 9, characterized in that, The PC setting mode setting via the programmable logic controller is specifically as follows: Input the sensor parameter settings to be simulated and transmit them to the programmable logic controller (PLC). The PLC performs range transformation calculations on the sensor parameter settings based on the pre-stored sensor characteristic model and outputs a DC voltage signal corresponding to the sensor parameter settings. The mode switching relay driven by the programmable logic controller (PLC) is controlled to switch the DC voltage signal output by the PLC and connect it to the corresponding sensor input interface of the external control unit under test.

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