Control method and control system of frequency conversion device and air conditioner

Abstract

According to the control method and control system of the frequency conversion device and the air conditioner, under the condition that the temperature data exceeds the first temperature threshold value, the dead zone time and / or the minimum opening time of the frequency conversion device are / is dynamically adjusted, effective control over the temperature of the frequency conversion device is achieved, and the service life of the frequency conversion device is prolonged. The problem that the temperature of the frequency conversion device is not properly controlled in the prior art is solved. Specifically, the method can effectively reduce the switching frequency and continuous turn-on duration of switching devices such as an IGBT (Insulated Gate Bipolar Transistor) and the like in a mode of timely increasing the dead time and the minimum turn-on time, thereby reducing the calorific value of the switching devices, reducing the turn-on and turn-off loss, and avoiding performance reduction or device damage caused by overhigh temperature. Meanwhile, the control mode does not change the carrier frequency, so that the response speed and the control precision of the system are not influenced, the stable output power of the frequency conversion device is ensured under severe working conditions, and the reliability and the service life of equipment are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a control method of a frequency conversion device, a control system and an air conditioner. Background Art

[0002] A frequency converter is a device that controls the operation of a motor by changing the frequency and voltage of alternating current. It can be used to adjust the speed and output torque of the motor to meet the performance requirements under different working conditions. The frequency converter can be composed of a rectifier, a DC bus, and an inverter. In addition, the frequency converter can also be equipped with protection modules, such as overcurrent protection, overtemperature protection, and short-circuit protection, to ensure the safe operation of the equipment under various working conditions. The frequency converter can be used in industrial automation, household appliances, electric vehicles and other fields to achieve precise motor control and improve the efficiency and flexibility of the system.

[0003] In the prior art, in the field of motor control, there is an inadequate technical problem in the temperature control of the frequency conversion device. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies and provide a control method, a control system and an air conditioner for a frequency converter to solve the technical problem of inadequate temperature control of the frequency converter in the field of motor control.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a control method for a frequency conversion device, the method is applied to a control device, the control device is used to control the frequency conversion device, the frequency conversion device is used to drive a motor; the method comprises:

[0007] Collecting the operating data of the current frequency conversion device; wherein the operating data at least includes temperature data;

[0008] Determining whether the temperature data is greater than a preset first temperature threshold;

[0009] When the temperature data is greater than a preset first temperature threshold, the dead time and / or the minimum on time of the frequency conversion device is increased.

[0010] In a second aspect, the present invention provides a control system, the control system comprising:

[0011] Motor;

[0012] A frequency conversion device, which is used to drive the motor;

[0013] A control device, which is used to collect operating data of the current frequency conversion device; wherein the operating data at least includes temperature data; then determine whether the temperature data is greater than a preset first temperature threshold; and when the temperature data is greater than the preset first temperature threshold, increase the dead time and / or minimum opening time of the frequency conversion device.

[0014] In a third aspect, the present invention provides an air conditioner, comprising: a control device, a frequency conversion device and a motor driven by the frequency conversion device, wherein the control device executes the above method.

[0015] Beneficial effects:

[0016] The present invention realizes effective control of the temperature of the frequency converter by dynamically adjusting the dead time and / or the minimum on time of the frequency converter when the temperature data exceeds the first temperature threshold, thereby solving the problem of inadequate temperature control of the frequency converter in the related art. Specifically, by timely increasing the dead time and the minimum on time, the method can effectively reduce the switching frequency and continuous on time of switching devices such as IGBTs, thereby reducing their heat generation and reducing the on-off loss, avoiding performance degradation or device damage caused by excessive temperature. At the same time, this control method does not change the carrier frequency, so it will not affect the response speed and control accuracy of the system, thereby ensuring the stability of the output power of the frequency converter under harsh working conditions and improving the reliability and life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of a control method of a frequency conversion device provided by an embodiment of the present invention;

[0018] Figure 2 is a flow chart of a control method of a frequency conversion device provided by an embodiment of the present invention;

[0019] Figure 3 is a flow chart of a control method of a frequency conversion device provided by an embodiment of the present invention;

[0020] Figure 4 is a flow chart of a control method of a frequency conversion device provided by an embodiment of the present invention;

[0021] Figure 5 It is a block diagram of an electronic device used in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0023] In the related art, in the field of motor control, frequency converters are widely used to drive motors. Their working principle is to control the speed and torque of the motor by adjusting the frequency and voltage. However, with the increasing application of frequency converters under high loads and complex working conditions, temperature control has become a key factor affecting equipment performance and life. The core components of frequency converters, such as IGBTs, will generate significant heat during high-frequency switching. If the heat is not dissipated in time, the equipment temperature will be too high, causing safety hazards, and may even cause the inverter to be forced to reduce power or stop running, affecting system stability. Therefore, temperature control design is particularly important in motor control systems.

[0024] In the related art, in order to alleviate the heating problem of power devices, two strategies are usually adopted: one is to rely on external heat dissipation devices such as air cooling or liquid cooling, and the other is to reduce the switching frequency through control means to reduce the number of switching times. However, these methods have certain limitations in practical applications. For example, in extreme environments, the external heat dissipation effect is limited, and although reducing the switching frequency can effectively reduce the heat generation, it affects the response speed of the motor, resulting in a decrease in the dynamic performance of the system. In addition, current distortion may also occur during the frequency switching process, further increasing the instability of the system. It can be seen that the existing temperature control strategy is difficult to strike a balance between efficient motor operation and temperature control, resulting in less than ideal adaptability and stability of temperature control.

[0025] Specifically, the related technology can reduce the number of switching times of power devices such as IGBT by reducing the carrier frequency, so as to achieve the purpose of reducing switching loss and reducing heat. Although reducing the carrier frequency can reduce the switching loss of power devices, the carrier frequency will directly affect the response speed of the system, making the motor slow down in dynamic control and difficult to meet the requirements of high-performance applications. Due to different requirements for control parameters under different carrier frequencies, the system needs to set multiple sets of control parameters in advance. However, in the actual operation process, when the carrier frequency is switched, it is easy to cause current distortion due to inaccurate parameter switching, increase the instability of the system, and increase the complexity of the control system. Moreover, external heat dissipation measures (for example, air cooling or liquid cooling) have limited effects in extreme environments, and the effect of reducing the carrier frequency on temperature control depends on the degree of change in working conditions, so it is difficult to achieve dynamic temperature control with strong adaptability. Furthermore, under different temperature and load conditions, frequent adjustment of the carrier frequency often affects the output performance and stability of the motor, especially when the load changes greatly or the ambient temperature is high, and it is impossible to achieve a good balance between temperature control and motor performance.

[0026] Therefore, there are many inappropriate aspects in temperature control in the related art. In applications with high performance requirements, the decrease in response speed caused by reducing the carrier frequency and the instability in frequency switching limit the applicability of the frequency converter, and it is difficult to achieve effective temperature control under high load or extreme environment. Therefore, in the related art, in the field of motor control, there are technical problems of inadequate temperature control of the frequency converter.

[0027] like Figure 1 As shown, a control method of a frequency conversion device is applied to a control device, the control device is used to control the frequency conversion device, and the frequency conversion device is used to drive a motor; the method may include:

[0028] Step S12: Collecting the operating data of the current frequency conversion device; wherein the operating data at least includes temperature data.

[0029] In this embodiment, the collection action can be represented as the control device reading corresponding data from the corresponding preset detection device to realize the collection of operation data.

[0030] The detection device may be a temperature sensor. It is understood that a temperature sensor may be installed inside the frequency converter, and the temperature sensor may measure the temperature data of the frequency converter (e.g., IGBT module) in real time. The control device may read data from the temperature sensor periodically or continuously. It is understood that the output signal of the temperature sensor may be an analog signal or a digital signal. If it is an analog signal, the control device will first convert it into a digital signal through an ADC (analog-to-digital converter) to facilitate subsequent processing and analysis.

[0031] After acquiring these data, the control device can perform further filtering and processing to eliminate noise and interference and ensure the accuracy of the data.

[0032] It is understood that after the control device collects and processes the temperature data, it can store it in an internal cache or storage unit. These real-time data will be continuously updated over time to reflect the temperature change trend and provide a basis for subsequent temperature judgment and control.

[0033] In this embodiment, the temperature data, as the key information in the operation data, directly reflects the working environment and state of the frequency converter. The temperature rise may be due to excessive load, high ambient temperature or poor heat dissipation, which will affect the stability and efficiency of the frequency converter. By collecting temperature data, the control device can timely determine whether it is necessary to start the temperature control strategy (for example, increase the dead time or the minimum opening time), so as to perform corresponding adjustments when the temperature exceeds the threshold, thereby reducing the heat generation and switching loss of the device.

[0034] In this implementation manner, the operation data may further include: operation frequency data and bus voltage data.

[0035] Therefore, the detection device may further include: a frequency detection module and a voltage detection module.

[0036] Specifically, the operating frequency data is an important parameter that reflects the motor speed and load status. By monitoring the operating frequency of the frequency converter, the control device can determine the real-time status of the motor. For example, at low frequencies, the motor load is usually light and the power demand is small. At this time, the control strategy can be more flexible to avoid unnecessary high-frequency switching. In the high-frequency operating state, the motor load is heavy, and the control device can optimize the control strategy according to this situation to ensure stable output.

[0037] The frequency detection module may be a detection module for detecting the output frequency of the frequency converter. The module may directly read the frequency data from the frequency control signal of the frequency converter. The frequency detection module may also be a detection module for indirectly obtaining the frequency data by measuring the operating characteristics of the motor.

[0038] More specifically, the frequency detection module may be: a frequency detection module based on a current sensor. It is understandable that the output of the frequency converter is usually connected to the motor, and the fluctuation frequency of the current signal can reflect the operating frequency of the motor, thereby indirectly reflecting the output frequency of the frequency converter. A current sensor can be used to detect changes in the output current, and the collected current signal is subjected to signal processing and frequency analysis to obtain frequency information. For example, the control device performs a fast Fourier transform (FFT) or other frequency analysis algorithm on the sampled value of the current signal to obtain the operating frequency data.

[0039] The frequency detection module may also be a frequency detection module based on the output voltage. It is understandable that the frequency of the inverter output voltage is also directly related to the operating frequency, so the operating frequency of the motor can be determined by monitoring the frequency of the output voltage.

[0040] The frequency detection module may also be a frequency detection module based on a speed sensor. It is understandable that some motors are equipped with speed sensors (e.g., encoders or speed generators) to directly obtain the motor speed. Through the known relationship between speed and frequency, the operating frequency data of the frequency converter is indirectly obtained.

[0041] The frequency detection module can also obtain the current output frequency by detecting the PWM signal frequency in the driving circuit.

[0042] Specifically, bus voltage data is a key power parameter of the frequency converter, which can directly affect the drive voltage level of the motor. By monitoring the bus voltage, the control device can evaluate the quality and stability of the current power supply and determine whether there are abnormal fluctuations. The bus voltage is closely related to the back electromotive force of the motor. Under high load or low voltage conditions, the back electromotive force will be closer to the bus voltage value, thereby affecting the output control ability of the frequency converter. Therefore, the collection of bus voltage data can assist the control device in adjusting the control strategy under extreme working conditions, such as appropriately increasing the dead time or minimum on time to prevent system instability or excessive switching losses.

[0043] The voltage detection module may be a voltage detection module based on a voltage divider resistor. It is understood that a high voltage signal may be reduced to a low voltage range suitable for ADC (analog-to-digital converter) input through a voltage divider resistor circuit.

[0044] The voltage detection module may also be a voltage detection module based on an isolation amplifier module.

[0045] The voltage detection module may also be a Hall voltage sensor.

[0046] In this implementation manner, the action of collecting the operating data of the current frequency conversion device may be to collect the operating data of the current frequency conversion device in real time or at intervals according to a set collection frequency.

[0047] In this implementation manner, the action of collecting the current operating data of the frequency conversion device may also be an action triggered by a preset event to perform the collection.

[0048] In this embodiment, the control device may be a digital signal processor (DSP).

[0049] In this embodiment, the control device may also be a microcontroller unit (MCU).

[0050] In this embodiment, the control device may also be a field programmable gate array (FPGA).

[0051] In this embodiment, the control device may also be an embedded control panel.

[0052] In this embodiment, the control device may also be an industrial computer (IPC).

[0053] In this embodiment, the frequency conversion device is used to adjust the input voltage and frequency of the motor to change the running speed and torque of the motor.

[0054] In this embodiment, the frequency conversion device may be a voltage type inverter.

[0055] In this embodiment, the frequency conversion device may also be a current source inverter.

[0056] In this embodiment, the frequency conversion device may be a high-voltage frequency converter.

[0057] In this implementation, the frequency conversion device may be a multi-level frequency converter.

[0058] In this implementation, the frequency conversion device may also be a DC bus frequency converter.

[0059] In this embodiment, the motor may be a three-phase induction motor.

[0060] In this embodiment, the motor may also be a permanent magnet synchronous motor.

[0061] In this embodiment, the motor may also be a brushless DC motor.

[0062] In this embodiment, the motor may also be a synchronous motor.

[0063] In this embodiment, the motor may also be a servo motor.

[0064] Step S14: determining whether the temperature data is greater than a preset first temperature threshold.

[0065] In this embodiment, the judgment action may be that the control device compares the currently detected temperature data with a preset first temperature threshold.

[0066] In this embodiment, the first temperature threshold may be represented as a warning value of the safe operating temperature of the frequency converter. For example, if the safe operating temperature limit of the IGBT is 100°C, the first temperature threshold may be set to 90°C to trigger control measures before the temperature approaches the limit.

[0067] It is understandable that different environments and application scenarios have different sensitivities to temperature, and the first temperature threshold can also be set according to specific usage conditions. For example, in a high-temperature working environment, the first temperature threshold can be relatively high, while in a low-temperature or indoor application, the first temperature threshold can be set lower to adapt to different cooling conditions and safety requirements.

[0068] Step S16: when the temperature data is greater than a first temperature threshold, increase the dead time and / or the minimum on time of the frequency conversion device.

[0069] In this embodiment, the dead time can be expressed as the time interval during which one IGBT is completely turned off before another IGBT is turned on when controlling the upper and lower bridge arms IGBTs (or other switching devices). This time period is used to ensure that the upper and lower bridge arms IGBTs are not turned on at the same time to avoid the shoot-through phenomenon.

[0070] In this embodiment, the control device may increase the dead time of the frequency converter, or increase the minimum on time of the frequency converter, or increase the dead time and the minimum on time of the frequency converter at the same time.

[0071] It is understandable that in the inverter circuit, two IGBTs are connected to the high voltage and low voltage ends respectively. When the IGBTs of the upper and lower bridge arms are turned on at the same time, the high voltage and low voltage ends will be directly short-circuited, causing failures or device damage. Setting the dead time ensures that the turn-on operation of the other IGBT is started only after one IGBT is completely turned off, avoiding the risk of short circuit.

[0072] In this embodiment, the minimum on-time can be expressed as the shortest duration of each on-time of the IGBT. If the on-time of the IGBT is shorter than the minimum on-time, the control system will not send an on-signal to avoid unnecessary switching loss and heating caused by extremely short on-time and off-time operations.

[0073] It is understandable that the IGBT is not turned on and off instantaneously, and usually takes a certain amount of time to respond to the drive signal. If the turn-on time is too short, the IGBT may be turned off before it is fully turned on, which will result in incomplete switching operation and increase switching losses. Moreover, frequently turning the IGBT on and off in a very short time will significantly increase switching losses and generate additional heat, affecting the overall efficiency and stability of the system. Setting the minimum turn-on time can effectively reduce frequent and ineffective switching operations and reduce switching losses. In a specific scenario example, assuming that the response time of an IGBT (turn-on delay time + turn-off delay time) is 2s, the minimum turn-on time can be set to 3s to ensure that each turn-on operation can be fully executed. If the turn-on time is shorter than 3s, the control device will filter out the turn-on signal to avoid losses caused by frequent switching.

[0074] In a specific embodiment, the control device may increase the dead time and / or the minimum on time of the frequency conversion device by the following method.

[0075] First, the current dead time and minimum on time gear can be determined. The control device can read the current dead time and minimum on time setting values ​​of the frequency converter to determine which preset gear it is currently in. Each gear corresponds to a specific dead time or minimum on time value. Assume that there are five gears for dead time and minimum on time, and the time of each gear gradually increases. For example, the dead time may range from 1s to 5s, and the minimum on time from 3s to 15s, and the specific increments can be pre-defined by the user.

[0076] Then, adjust to the time value of the next gear. The control device can adjust it to the next higher gear value based on the dead time and minimum opening time of the current gear to increase the dead time and / or the minimum opening time. For example, you can find the next gear value of the current gear. Then calculate the increment to update the setting of the dead time and the minimum opening time. If the current dead time is 2s (corresponding to gear 2), the control device will adjust the dead time to 3s (corresponding to gear 3). Similarly, if the minimum opening time is 6s (gear 2), adjust it to 9s (gear 3).

[0077] Finally, a new PWM control signal is generated. The control device generates a new PWM control signal and embeds the updated dead time and minimum on time in the signal. This operation ensures that the frequency converter applies the new setting value when performing PWM signal modulation. Specifically, first, in the PWM control module of the control device, the control device writes the new dead time (for example, 3s) into the time parameter register. This setting will ensure that the new dead time is applied when the upper and lower bridge arms IGBT switch. The control device writes the minimum on time into the minimum on time register of the PWM control module. The register will filter out the on signal shorter than the set time to ensure that the IGBT does not perform a short-time switching operation shorter than the minimum time. Then, the control device generates a set of PWM pulse waveforms according to the updated dead time and minimum on time. There will be a new dead time interval between the upper bridge arm and the lower bridge arm of the new waveform, and at the same time ensure that each on pulse meets the minimum on time requirement. In the process of generating the PWM signal, the control device applies the set dead time to ensure that each pulse waveform has a suitable delay when the upper bridge arm and the lower bridge arm switch. The minimum on-time filtering mechanism is implemented in the PWM control module, and pulses shorter than the minimum on-time are filtered and automatically discarded.

[0078] It is understandable that the new PWM control signal will be output to the drive circuit of the frequency converter, so that the drive circuit performs switching operations according to the new parameters. The new PWM control signal is transmitted to the drive circuit through the output interface of the control device, and the drive circuit performs specific switching operations according to the pulse width, frequency, dead time and minimum switching time of the PWM signal to ensure that the IGBT works in accordance with the adjusted set value.

[0079] It is understandable that after adjusting the dead time and the minimum on time, the control device will continue to monitor the temperature data of the frequency converter to determine whether the temperature is effectively controlled. If the temperature continues to rise, the control device can further increase the dead time and the minimum on time to gradually achieve the control effect.

[0080] It is also understandable that, in order to ensure the stability of the system, the control device will set a threshold value of the maximum allowable dead time and the minimum on time to prevent regulation beyond the safety range. Accordingly, if the dead time and the minimum on time have reached the maximum allowable value and the temperature continues to rise, the control device can take further measures, such as reducing the carrier frequency or limiting the output power.

[0081] In this implementation scheme, the method of gradually increasing the dead time and the minimum on time not only effectively reduces the switching frequency and switching loss of the IGBT without changing the carrier frequency, but also controls the temperature of the frequency converter, thereby improving the reliability and stability of the frequency converter.

[0082] In a specific implementation, the control device may also use the following method to increase the dead time and / or minimum on time of the frequency conversion device.

[0083] First, the control device calculates the rate of temperature rise. If the temperature rise rate is high, it means that the temperature rises quickly and needs to be controlled more quickly; if the temperature rise rate is low, smaller increments can be used to gradually adjust.

[0084] Then, the adjustment increment size is determined according to the temperature rise rate. For example, if the temperature rise rate is greater than the set critical value (such as a rise of more than 2°C per second), the control device can increase the dead time and the minimum opening time by a larger step size at one time (such as an increase of 2s or more); if the temperature rise rate is low (such as less than 1°C per second), the control device can use a smaller step size (such as 1s) to gradually increase the dead time and the minimum opening time.

[0085] Finally, the control device applies the increment to the dead time and the minimum on time to generate a new PWM control signal to ensure that the inverter executes the updated set value in the next cycle. At the same time, the control device continues to monitor the temperature. If the temperature rise rate continues to change, the corresponding increment step size is adjusted to form an adaptive temperature control process.

[0086] In a specific implementation, the control device may also use the following method to increase the dead time and / or minimum on time of the frequency conversion device.

[0087] The control device pre-divides the temperature range into multiple sections, for example, a low temperature section (temperature less than T1), a medium temperature section (temperature between T1 and T2), and a high temperature section (temperature greater than T2). Each temperature section is pre-configured with a specific dead time and minimum opening time gear value, for example: the low temperature section corresponds to a dead time of 1s and a minimum opening time of 3s; the medium temperature section corresponds to a dead time of 3s and a minimum opening time of 9s; the high temperature section corresponds to a dead time of 5s and a minimum opening time of 15s.

[0088] The control device determines the temperature range based on the current temperature data. For example, if the temperature data is between T1 and T2, the control device will directly select the dead time and minimum opening time value of the medium temperature range, skipping the gradual increase process to quickly enter the appropriate temperature control state.

[0089] Finally, the control device applies the dead time and minimum on time settings of the corresponding interval to the PWM control signal to ensure that the frequency converter automatically switches to the appropriate control parameters in different temperature intervals. If the temperature changes and the interval changes, the control device will reselect the corresponding gear value to ensure the real-time and response speed of temperature control.

[0090] In a possible and specific implementation, the effects of increasing the dead zone and the minimum on-time limit of the IGBT can be shown in the following table.

[0091] Table 1: Schematic diagram of the effect of increasing the dead zone.

[0092]

[0093]

[0094] In Table 1, 0 indicates off and 1 indicates on. After the dead time increases, the buffer time between two adjacent PWM waves with the largest duty cycle increases, which reduces the power density and alleviates the heat accumulation phenomenon.

[0095] In the control process of the frequency conversion device, the IGBT needs to continuously perform switching operations to achieve the modulation of the PWM signal. However, each switching on and off of the IGBT will generate switching losses, which mainly come from two aspects: switching losses and switching losses.

[0096] Increase the dead time, that is, insert a small time interval during the switching process of the upper and lower arm IGBTs to ensure that one IGBT will start to turn on only after it is completely turned off, thereby avoiding the direct short circuit phenomenon and reducing the energy loss during the switching process.

[0097] Table 2: Schematic diagram of the effect of increasing the minimum opening time limit.

[0098]

[0099] It can be seen from Table 2 that after the control instruction with an on-time of less than 3 milliseconds is removed, the number of on-off times in the continuous cycle is reduced by 30%, that is, the on-off loss is reduced by 30%, but the equivalent on-time is the same, that is, the output voltage is basically the same.

[0100] In a control system, if the IGBT's on-time is too short, the on-command and off-command may reach the IGBT successively, causing it to frequently perform switching actions. This frequent short-time switching operation will lead to more switching losses and increase the heat generated by the IGBT. By increasing the minimum on-time, the on-command signal with a duration of too short can be filtered out, allowing the IGBT to remain in the on state for a longer time and reducing unnecessary switching times.

[0101] This embodiment achieves effective control of the temperature of the frequency converter by dynamically adjusting the dead time and / or the minimum on time of the frequency converter when the temperature data exceeds the first temperature threshold, and solves the problem of inadequate temperature control of the frequency converter in the related art. Specifically, by timely increasing the dead time and the minimum on time, this method can effectively reduce the switching frequency and continuous on time of switching devices such as IGBTs, thereby reducing their heat generation and reducing the on-off loss, and avoiding performance degradation or device damage caused by excessive temperature. At the same time, this control method does not change the carrier frequency, so it will not affect the response speed and control accuracy of the system, thereby ensuring the stability of the output power of the frequency converter under harsh working conditions and improving the reliability and life of the equipment. Without increasing additional heat dissipation costs, this embodiment provides an effective temperature management control strategy.

[0102] like Figure 2 As shown, in some embodiments, the step of increasing the dead time and / or the minimum on time of the frequency conversion device includes:

[0103] Step S162: Determine that the current dead time and / or minimum opening time is in the current gear position among the preset gear positions; wherein the dead time and / or minimum opening time are pre-configured with multiple gear positions, and each gear position corresponds to a specific gear position value.

[0104] In this embodiment, the determined action may mean that the control device reads and analyzes the currently set dead time and minimum opening time parameters, identifies their positions in the preset gears, and finds the current gear corresponding to these parameter values.

[0105] It can be understood that each gear position is pre-configured with a specific time value, and the control device matches the corresponding gear position according to the read time value.

[0106] Specifically, the control device first reads the specific values ​​of the dead time and the minimum opening time currently set inside the frequency conversion device. These values ​​are stored in the parameter storage unit or register of the control device, and the control device obtains these current setting values ​​by calling the corresponding interface. Then, the control device compares the read current setting value with the pre-configured gear table (which can also be a gear mapping relationship table) to determine the gear corresponding to these time values. For example, the preset gear table contains multiple gears, and each gear has a specific time value (for example, gear 1 corresponds to 1μs, gear 2 corresponds to 2μs, etc.). Finally, after determining the current gear, the control device records the gear as the current state. This record will be stored in the memory or register of the control device for subsequent steps (for example, increasing to the target gear) to call.

[0107] Step S164: adjusting the dead time and / or the minimum opening time from the current gear to the target gear; wherein the gear value of the target gear is greater than the gear value of the current gear.

[0108] In this embodiment, the control device can search the preset gear table and select the next gear that is greater than the current gear. For example, if the current gear is gear 2 (corresponding to a dead time of 2s), the control device will select gear 3 (corresponding to 3s) as the target gear. After determining the target gear, the control device extracts the specific time value (dead time and / or minimum opening time) corresponding to the gear from the gear table.

[0109] In this embodiment, multiple gears are preconfigured, each gear corresponds to a specific dead time and minimum on time value, and when the temperature or operating state changes, the current gear is adjusted to the target gear. This method can gradually increase the dead time and minimum on time according to actual needs without a one-time excessive adjustment. This gear adjustment can effectively reduce the switching frequency and switching loss of the IGBT, reduce device heating, while maintaining the response speed and control accuracy of the system, thereby improving the stability and reliability of the frequency converter under different temperature and load conditions.

[0110] In some embodiments, the step of increasing the dead time and / or the minimum on time of the frequency conversion device includes:

[0111] Step S166: Based on the current dead time and / or minimum on time of the frequency converter, add at least one preset increment to increase the current dead time and / or minimum on time; wherein the increment is a predefined time value.

[0112] In this embodiment, the preset increment can be expressed as a pre-set time value for adjusting the dead time and the minimum on time. In this embodiment, one or more preset increments are added to the original time value each time to gradually improve the time parameter. By introducing the preset increment, the control device can gradually adjust the control parameter in small steps to avoid excessive instantaneous changes, thereby finely controlling the switching time of the frequency converter.

[0113] In a specific scenario example, assuming that the current dead time is 2s, the minimum on time is 6s, and the preset increments are 1s (for the dead time) and 3s (for the minimum on time). During the first increase, when the control device detects that the temperature exceeds the first threshold, it increases the current dead time by 1s to 3s and increases the minimum on time by 3s to 9s. If the temperature continues to rise and reaches the preset condition, the control device increases the preset increment again, increasing the dead time to 4s and the minimum on time to 12s.

[0114] In this embodiment, by adding at least one preset increment based on the current dead time and / or minimum on time, the control device can adapt to temperature and load changes more flexibly without relying on fixed gear adjustment. This method of gradually increasing the preset increment can finely control the change of dead time and minimum on time according to the actual needs of temperature rise, reduce the switching frequency and effectively reduce the switching loss and heat generation of the IGBT. Compared with the method of directly adjusting the gear, this method avoids frequent and large-scale parameter adjustments while maintaining high control accuracy, thereby improving the response speed and temperature control stability of the system, effectively extending the life of the frequency converter and enhancing the system reliability.

[0115] In some embodiments, when the temperature data is less than or equal to a preset first temperature threshold, the method further includes:

[0116] Reduce the dead time and / or the minimum on time of the frequency conversion device.

[0117] In this embodiment, the control device can reduce the dead time of the frequency converter, reduce the minimum on time of the frequency converter, or reduce the dead time and the minimum on time of the frequency converter at the same time.

[0118] In this embodiment, when the temperature data is lower than or equal to the preset first temperature threshold, by actively reducing the dead time and / or the minimum on time of the frequency converter, the minimum turn-off delay and on time of the IGBT can be reduced, thereby improving the switching frequency and the overall efficiency of the system. In this method, when the temperature permits, the frequency converter can operate more efficiently while maintaining a good control response speed and output accuracy, reducing unnecessary losses. This dynamic adjustment mechanism not only improves the energy efficiency of the system, but also effectively extends the service life of the equipment and improves the operating stability of the frequency converter under low temperature and normal temperature conditions.

[0119] like Figure 3 As shown, in some embodiments, after the step of increasing the dead time and / or the minimum on time of the frequency conversion device, the method further includes:

[0120] Step S18: Update the temperature data.

[0121] Step S20: Determine whether the current temperature data is greater than a second temperature threshold; wherein the second temperature threshold is greater than the first temperature threshold, and is used to determine whether the control method can effectively suppress the temperature rise.

[0122] In this embodiment, the second temperature threshold can be expressed as a temperature reference point for evaluating whether the control measures can effectively suppress the temperature rise. Its value can be set to a temperature value slightly higher than the first temperature threshold so as to quickly judge the temperature control effect after the initial adjustment measures. The control device evaluates whether the current temperature control strategy is effective enough by monitoring whether the temperature reaches or exceeds the second temperature threshold. If the temperature exceeds the second temperature threshold, the control device will take further cooling measures, such as increasing the adjustment range of the dead time and the minimum opening time or reducing the operating frequency.

[0123] For example, the first temperature threshold is set to 75° C., and the second temperature threshold can be set to 78° C., which is slightly higher than the first threshold.

[0124] Step S22: when the current temperature data is greater than the second temperature threshold, controlling the frequency conversion device to reduce the operating frequency of the frequency conversion device.

[0125] In this embodiment, the control device can calculate an appropriate target frequency value according to the current temperature data and load conditions. The target frequency can be set to be slightly lower than the current frequency so as to gradually reduce the power output and reduce the temperature rise. The control device applies the calculated target frequency parameter to the PWM signal generation to generate a new low-frequency PWM signal, thereby reducing the output frequency of the frequency conversion device.

[0126] In this embodiment, by further monitoring the temperature data after increasing the dead time and / or the minimum on time, and judging whether the temperature control effect is effective, additional frequency reduction measures can be taken in time when the temperature continues to rise. This method implements a multi-level temperature control strategy, ensuring that when the initial temperature control measures (increasing the dead time and the minimum on time) are not sufficient to control the temperature rise, the frequency can be automatically reduced to further reduce the switching burden of the power device, thereby reducing the temperature. This multi-step monitoring and response mechanism significantly improves the stability and reliability of the frequency conversion device under high temperature conditions, extends the service life of the equipment, and avoids the risk of damage that may be caused by a sudden temperature increase.

[0127] In some embodiments, after the step of controlling the frequency conversion device to reduce the operating frequency of the frequency conversion device, the method further includes:

[0128] Step S24: re-update the updated temperature data.

[0129] Step S26: Determine whether the current temperature data is greater than a third temperature threshold; wherein the third temperature threshold is greater than the second temperature threshold.

[0130] In this embodiment, the third temperature threshold may be a limit temperature value. Once the current temperature exceeds this value, the control device will trigger a forced shutdown to avoid irreversible damage to the device due to overheating. The temperature threshold may be set to the highest safe temperature that the device or key components (e.g., IGBT module) can withstand to ensure that the device can be fully protected under extreme high temperature conditions.

[0131] For example, if the maximum allowable temperature of a key component (IGBT module) of the frequency converter is 105°C, the third temperature threshold may be set to 100°C.

[0132] Step S28: when the current temperature data is greater than the third temperature threshold, at least control the frequency conversion device to stop running.

[0133] In this embodiment, the control device can control the frequency conversion device to stop running, and can also control the motor to stop running.

[0134] In this embodiment, when the current temperature data is greater than the third temperature threshold, the control device may also start a cooling device, for example, start a hair dryer or a cooling fan to increase air circulation, accelerate the heat dissipation process of the frequency conversion device and key components, and reduce the temperature.

[0135] In this embodiment, when the current temperature data is greater than the third temperature threshold, the control device may also trigger an alarm system.

[0136] In this embodiment, by continuously monitoring the temperature data after reducing the operating frequency and setting a third temperature threshold, the control device can take protective measures of forced shutdown when the temperature continues to rise and exceeds the safe range. This method establishes a multi-level safety protection mechanism, which not only controls the temperature by gradually reducing the frequency, but also automatically shuts down when the temperature reaches an uncontrollable limit to prevent component damage or system failure caused by overheating. This multiple temperature control protection measure ensures the safety and stability of the frequency converter under extreme conditions, effectively prolongs the service life of the equipment and reduces the risk of shutdown due to high temperature.

[0137] In some embodiments, the operation data further includes the operation frequency data and bus voltage data of the current frequency converter; before the step of increasing the dead time and / or the minimum on time of the frequency converter, the method further includes:

[0138] Step S151: Calculate the back electromotive force voltage data of the current motor based on the operating frequency data.

[0139] In this embodiment, the back EMF voltage data can be expressed as a voltage generated by the interaction of the magnetic field during the rotation of the motor. Its direction is opposite to the direction of the power supply voltage of the motor. In an AC motor, the back EMF voltage increases as the speed of the motor increases. When the motor speed is high, the back EMF voltage is also large, which will offset a part of the drive voltage supplied to the motor and reduce the motor's demand for input power. The existence of back EMF is part of the internal energy conversion of the motor, and its value affects the operating efficiency, speed control and temperature control of the motor.

[0140] In this embodiment, based on the operating frequency data, calculating the current motor back electromotive force voltage data can be expressed as multiplying the operating frequency data by the back electromotive force constant to obtain the back electromotive force voltage data. It can be understood that the current operating frequency of the motor is proportional to the speed of the motor.

[0141] In this embodiment, the operating frequency data can be represented by the frequency of the alternating current currently outputted by the frequency converter to the motor. The operating frequency determines the rotation speed of the motor.

[0142] In this implementation, the bus voltage data may be represented by a DC bus voltage of the frequency converter, that is, a DC power supply voltage input to the frequency converter.

[0143] Step S152: Determine whether the back electromotive force voltage data is smaller than the bus voltage data.

[0144] The step of increasing the dead time and / or the minimum on time of the frequency conversion device when the temperature data is greater than the first temperature threshold value further includes:

[0145] Step S160: Only when the temperature data is greater than the first temperature threshold and the back electromotive force voltage data is less than the bus voltage data, increase the dead time and / or the minimum on time of the frequency conversion device.

[0146] It is understandable that the back EMF voltage is directly related to the motor speed, and its magnitude largely reflects the motor load. When the motor runs at high speed or high load, the back EMF voltage will increase and gradually approach the bus voltage. If the back EMF voltage reaches or even exceeds the bus voltage, the supply voltage will be insufficient, causing the motor to run unstable or not operate normally.

[0147] When the back EMF voltage approaches the bus voltage, the effective amplitude of the drive voltage will decrease. At this time, if the dead time is increased, the equivalent voltage at the motor end will be further reduced, resulting in insufficient motor drive voltage, which may cause speed instability, torque drop, and even motor stall. Therefore, only by increasing the dead time when the back EMF is lower than the bus voltage can the motor have sufficient voltage margin.

[0148] When the back EMF is high, the motor's output power is already close to the upper limit. If the minimum on time and dead time are increased at this time, the motor's on time will be reduced, which will cause the output voltage to decrease, further affecting the motor's output power. By ensuring that the back EMF voltage is less than the bus voltage, the control device can effectively adjust the switching time under light or medium load conditions without affecting the motor's output performance.

[0149] Therefore, in this embodiment, only when the temperature data is greater than the first temperature threshold and the back electromotive force voltage data is less than the bus voltage data, the dead time and / or the minimum on time of the frequency converter are increased. This allows the switching frequency and switching loss to be effectively reduced when the temperature is too high, but does not cause unnecessary output waveform distortion under heavy load or high-speed operation. This ensures that while taking cooling measures at high temperatures, the motor can still maintain stable performance output and achieve a more sophisticated temperature control effect.

[0150] In this embodiment, the back electromotive force voltage of the motor is calculated based on the operating frequency data before increasing the dead time and / or the minimum on time, and compared with the bus voltage. The dead time and the minimum on time are increased only when the back electromotive force voltage is less than the bus voltage and the temperature exceeds the first temperature threshold. This method can ensure that temperature control adjustment is performed only when the motor load conditions permit, avoiding the reduction of output voltage due to excessive increase of dead time under high back electromotive force state, resulting in unstable operation of the motor or performance degradation. This dual-condition judgment mechanism improves the accuracy of temperature control measures, effectively suppresses temperature rise while ensuring motor performance, and enhances the safety and reliability of the frequency converter under complex working conditions.

[0151] In some implementations, when the back electromotive force voltage data is greater than or equal to the bus voltage data, the method further includes:

[0152] At least the dead time and / or minimum on time of the current frequency converter is maintained.

[0153] In this implementation manner, when the back electromotive force voltage data is greater than or equal to the bus voltage data, the control device may maintain the dead time and / or the minimum on time of the current frequency conversion device.

[0154] In this implementation manner, when the back electromotive force voltage data is greater than or equal to the bus voltage data, the dead time and / or the minimum on time of the current frequency conversion device may also be reduced.

[0155] In this embodiment, when the back electromotive force voltage data is greater than or equal to the bus voltage data, the control device can switch to a more suitable PWM modulation method (for example, switching from space vector PWM to sinusoidal PWM) to improve voltage utilization and ensure a stable driving voltage when the back electromotive force is high.

[0156] In this embodiment, when the back electromotive force voltage data is greater than or equal to the bus voltage data, the control device can enable weak magnetic control to reduce the back electromotive force by reducing the magnetic flux of the motor, thereby increasing the voltage difference between the bus voltage and the back electromotive force.

[0157] In this embodiment, when the back electromotive force voltage data is greater than or equal to the bus voltage data, by maintaining the current dead time and / or minimum on time, the risk of insufficient driving voltage caused by further increasing the dead time can be avoided. This method can effectively maintain the stable output of the motor under high motor speed or high load conditions (i.e., when the back electromotive force approaches or exceeds the bus voltage), avoiding speed fluctuations or power drops caused by insufficient voltage margin. This strategy ensures the stability of the frequency converter when running at high load or high speed, avoids unnecessary power loss, extends the service life of the equipment, and ensures reliable operation under high load conditions.

[0158] like Figure 4 As shown, in a possible and specific implementation scheme, a control method of a frequency conversion device is provided, the method comprising:

[0159] During the operation of the inverter, the control module (eg, DSP) may collect the current temperature T, frequency F, and bus voltage V of the inverter.

[0160] 1. Determine whether the temperature T is greater than the temperature threshold T1 (for example, 90 degrees Celsius)

[0161] When the temperature T is less than the temperature threshold T1, the current dead time and / or the minimum on time can be reduced by one level. The significance of such operation is that the current temperature T is less than the temperature threshold T1, indicating that the current temperature of the inverter is not high and has not reached the warning threshold. In this case, efficiency can be prioritized. Therefore, the current dead time and / or the minimum on time can be reduced by one level, so that the inverter can output higher power.

[0162] It can be understood that the gear is pre-configured, that is, it is pre-written in the control module, and can be divided into multiple gears. For example, five gears are pre-configured, and each gear has a corresponding dead time and minimum opening time. The higher the gear, the larger the dead time and minimum opening time. If it is currently in the second gear, when the temperature T is less than the temperature threshold T1, the current second gear can be adjusted to the first gear.

[0163] When the temperature T is greater than or equal to the temperature threshold T1, the current back electromotive force needs to be further calculated. VF = F*K. F is the current frequency of the inverter. K is a constant.

[0164] It should be noted that the motor will generate a back EMF during rotation, which is usually proportional to the motor speed. This back EMF is a "reverse" voltage that will offset part of the drive voltage. When the dead time is increased, the equivalent output voltage will decrease, while the back EMF generated by the motor will increase with the speed. If the equivalent voltage is less than the back EMF, the motor will operate unstably or even fail to operate normally. To avoid this, it is necessary to ensure that the equivalent voltage is always greater than the back EMF.

[0165] In control, in order to ensure that the equivalent voltage is greater than the back electromotive force, the dead time needs to be limited.

[0166] Tmax=P*(V1-V2) / V1

[0167] In the formula, the controlled carrier period is P, the current bus voltage is V1, and V2 is the back electromotive force.

[0168] This formula shows that at the current motor speed, the maximum value of the dead time depends on the motor's back EMF. If the back EMF is close to the bus voltage, the maximum dead time will decrease, otherwise it can increase.

[0169] 2. Determine whether the current back electromotive force is less than the bus voltage

[0170] When the current back electromotive force is less than the bus voltage, it means that there is still room for adjustment, and the current dead time and / or minimum on time can be increased by one level on the original basis, or each can be increased by one adjustment unit.

[0171] Correspondingly, if the current back electromotive force is greater than or equal to the bus voltage, it means that there is no adjustment space. In this case, the dead time and / or the minimum on time cannot be increased.

[0172] So in this case, keep the current dead time and minimum opening time first, and proceed to the next step.

[0173] 3. Determine whether the current temperature T is greater than the temperature threshold T2 (for example, 95 degrees Celsius)

[0174] If it is greater than the indication, after the above adjustments, the trend of the inverter temperature increase still cannot be curbed, so in this case, directly reduce the operating frequency of the inverter to reduce the temperature.

[0175] In other words, in this case, increasing the dead time and the minimum on time will not reduce the temperature, or in this case, the current back electromotive force is already greater than or equal to the bus voltage, and the dead time and the minimum on time cannot be increased, otherwise the motor operation will become unstable.

[0176] So, in this case, simply reduce the operating frequency of the inverter to reduce the temperature.

[0177] Correspondingly, if the current temperature T is less than the temperature threshold T2, it means that after adjusting the dead time and the minimum on time in the above process, the rising trend of the inverter temperature has been curbed (although the temperature still rises because T2 is greater than T1, the increase rate is very small and controllable). So in this case, directly return to the initial step and re-collect the current inverter temperature T, frequency F and bus voltage V.

[0178] 4. Determine whether the current temperature T is greater than the temperature threshold T3 (for example, 100 degrees Celsius)

[0179] The temperature threshold T3 is a warning value, exceeding which may cause malfunction and damage.

[0180] So it shuts down directly. If it does not exceed, it returns to the initial step and re-collects the current inverter temperature T, frequency F and bus voltage V.

[0181] According to an embodiment of the present invention, a control system is provided, the control system comprising:

[0182] Motor;

[0183] A frequency conversion device, which is used to drive the motor;

[0184] A control device, which is used to collect operating data of the current frequency conversion device; wherein the operating data at least includes temperature data; then determine whether the temperature data is greater than a preset first temperature threshold; and when the temperature data is greater than the preset first temperature threshold, increase the dead time and / or minimum opening time of the frequency conversion device.

[0185] According to an embodiment of the present invention, an air conditioner is provided, the air conditioner comprising: a control device, a frequency conversion device and a motor driven by the frequency conversion device, the control device performs the above method. According to an embodiment of the present invention, an electronic device is provided, see Figure 5 The electronic device in this embodiment may include one or more of the following components: a processor, a network interface, a memory, a non-volatile memory, and one or more applications, wherein the one or more applications may be stored in the non-volatile memory and configured to be executed by one or more processors, and the one or more programs are configured to execute the method described in the aforementioned method embodiment.

[0186] According to an embodiment of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a computer, the computer executes the method described in any of the above embodiments.

[0187] According to an embodiment of the present invention, a computer program product including instructions is also provided. When the instructions are executed by a computer, the computer executes a method in any one of the above embodiments.

[0188] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0189] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0190] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0191] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0192] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A control method for a frequency conversion device, characterized in that: The method is applied to a control device, the control device is used to control a frequency conversion device, and the frequency conversion device is used to drive a motor; the method includes: Collecting the operating data of the current frequency conversion device; wherein the operating data at least includes temperature data; Determining whether the temperature data is greater than a preset first temperature threshold; When the temperature data is greater than a preset first temperature threshold, the dead time and / or the minimum on time of the frequency conversion device is increased.

2. The method according to claim 1, characterized in that The step of increasing the dead time and / or the minimum on time of the frequency conversion device comprises: Determine that the current dead time and / or minimum opening time is in a current gear position among preset gear positions; wherein the dead time and / or minimum opening time are pre-configured with multiple gear positions, and each gear position corresponds to a specific gear position value; The dead time and / or the minimum opening time are adjusted from the current gear to the target gear; wherein the gear value of the target gear is greater than the gear value of the current gear.

3. The method according to claim 1, characterized in that The step of increasing the dead time and / or the minimum on time of the frequency conversion device comprises: Based on the current dead time and / or minimum on time of the frequency conversion device, at least one preset increment is added to increase the current dead time and / or minimum on time; wherein the increment is a predefined time value.

4. The method according to claim 1, characterized in that: When the temperature data is less than or equal to a preset first temperature threshold, the method further includes: Reduce the dead time and / or the minimum on time of the frequency conversion device.

5. The method according to claim 1, characterized in that After the step of increasing the dead time and / or the minimum on time of the frequency conversion device, the method further comprises: updating the temperature data; Determine whether the current temperature data is greater than a second temperature threshold; wherein the second temperature threshold is greater than the first temperature threshold, and is used to determine whether the control method can effectively suppress the temperature rise; When the current temperature data is greater than the second temperature threshold, the frequency conversion device is controlled to reduce the operating frequency of the frequency conversion device.

6. The method according to claim 5, characterized in that After the step of controlling the frequency conversion device to reduce the operating frequency of the frequency conversion device, the method further includes: Update the updated temperature data again; Determine whether the current temperature data is greater than a third temperature threshold; wherein the third temperature threshold is greater than the second temperature threshold; When the current temperature data is greater than the third temperature threshold, at least the frequency conversion device is controlled to stop running.

7. The method according to any one of claims 1 to 6, characterized in that: The operation data also includes the operation frequency data and bus voltage data of the current frequency converter; before the step of increasing the dead time and / or the minimum opening time of the frequency converter, the method also includes: Based on the operating frequency data, calculating the back electromotive force voltage data of the current motor; Determining whether the back electromotive force voltage data is less than the bus voltage data; The step of increasing the dead time and / or the minimum on time of the frequency conversion device when the temperature data is greater than the first temperature threshold value further includes: Only when the temperature data is greater than the first temperature threshold and the back electromotive force voltage data is less than the bus voltage data, the dead time and / or the minimum on time of the frequency conversion device is increased.

8. The method according to claim 7, characterized in that In the case where the back electromotive force voltage data is greater than or equal to the bus voltage data, the method further includes: At least the dead time and / or minimum on time of the current frequency converter is maintained.

9. A control system, characterized in that: The control system comprises: Motor; A frequency conversion device, which is used to drive the motor; A control device, which is used to collect operating data of the current frequency conversion device; wherein the operating data at least includes temperature data; then determine whether the temperature data is greater than a preset first temperature threshold; and when the temperature data is greater than the preset first temperature threshold, increase the dead time and / or minimum opening time of the frequency conversion device.

10. An air conditioner, characterized in that: The air conditioner comprises: a control device, a frequency conversion device and a motor driven by the frequency conversion device, and the control device executes the method according to any one of claims 1 to 8.

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