CN112032978A - A winding induction heating method, system and air conditioning equipment - Google Patents

Abstract

The invention provides a winding induction heating method and system and air conditioning equipment. The method comprises the steps of testing a compressor control system, fixing heating target power conditions when a compressor is heated, determining different duty ratios corresponding to different direct current bus voltages, and fitting a curve relation between the direct current bus voltages and the duty ratios; when the compressor is heated, detecting the current direct-current bus voltage in a compressor control system in real time, and adjusting the duty ratio according to the established relation between the direct-current bus voltage and the duty ratio and corresponding to the detected current direct-current bus voltage; and performing PWM output control according to the adjusted duty ratio to control the opening time sequence of the power module of the compressor control system and keep the heating power constant when the compressor is heated. The scheme can realize that the duty ratio is adjusted according to voltage fluctuation to control the winding to perform induction heating to keep the heating power constant, avoids overlarge or undersize heating power caused by voltage fluctuation, and has the characteristics of low power consumption, low cost, high reliability and the like.

Description

A winding induction heating method, system and air conditioning equipment

technical field

The invention relates to the technical field of compressor heating control, in particular to a winding induction heating method, system and air conditioning equipment.

Background technique

Air conditioning compressor, when the temperature is low, the refrigeration oil in the compressor will condense. In this case, the forced start requires a large torque and generates a large amount of driving power, which causes the winding heat to be too large, which will cause the permanent magnet inside the compressor to demagnetize. , the startup fails, and there is a problem of excessive energy consumption. In addition, such long-term operation will increase the wear of the compressor; when the temperature is high and the refrigeration unit is shut down, the refrigerant liquid in the compressor shell is prone to incomplete evaporation, leakage and blockage, which will damage the lubrication of the compressor. . Therefore, the above situation can be avoided by properly heating the air conditioner compressor. Moreover, during the heating process, the heating power can neither be too large nor too small. If the heating power is too large, the motor coil will be overheated and aged or even demagnetized. If the heating power is too small, the intended purpose of heating will not be achieved.

In the existing compressor heating technology, there are mainly three ways:

1) Auxiliary electric heating belt heating: add an external electric heating belt to the compressor, and heat it by supplying power to the heating belt. For open-loop control, an external electric heating belt needs to be added to the compressor, and the cost is high. Shell heat conduction heating compressor has large internal energy consumption and low efficiency, and the power is different when the voltage fluctuates, so the heating power/calorific value cannot be kept constant. Even if it is used for a long time, the heating belt may break due to high temperature and stress, which may affect the normal operation of the compressor, and there is a fire hazard.

2) Use compressor winding copper loss heating: apply a large current to the compressor winding, and generate heat through the winding's own resistance, that is, copper loss, which is closed-loop control. The current flowing through the motor winding is close to DC, and the DC current can be detected to adjust the power module. The duty cycle can ensure the constant heating power, but the winding resistance will cause loss through the large current, the power consumption will be too large, and the power module itself will generate heat.

3) Induction heating using compressor winding iron loss: By applying high-frequency AC voltage to the two phases of the compressor, the hysteresis loss and eddy current loss of the compressor ferromagnetic material, that is, iron loss, are increased to realize winding induction heating, which is open-loop control. , the heating power cannot be guaranteed to be constant. Compared with the first two methods, the current is small, the power module loss is small, the reliability is high, and the cost is low. However, since induction heating is mainly based on hysteresis loss and eddy current loss, the loss model is complex and it is generally difficult to calculate the heating power. It usually relies on experimental data, and its current is small and changes rapidly, which makes detection difficult. When the voltage of the public grid is constant, the power device switches according to a fixed duty cycle under a fixed switching cycle, so that the heating power can be kept constant; in fact, the input voltage of the public grid is not constant, but fluctuates within a certain range. In this case, if the power device switches according to the original duty cycle, the heating power will still be too large or too small (too large will cause the motor coil to overheat, age, demagnetize, and if too small, it will not reach the heating expectation).

In view of the above defects, a new winding induction heating method is required, which can easily adjust the duty cycle according to the voltage fluctuation under the condition of voltage fluctuation, ensure a constant heating power, avoid the voltage fluctuation causing the heating power to be too large or too small, and maintain The winding induced current is small, the power consumption is small, the cost is low, and the reliability is strong.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned defects, the present invention is proposed to solve or at least partially solve the technical problem of how to adjust the duty cycle according to the voltage fluctuation to control the induction heating of the winding to keep the heating power constant. In view of the above technical problems, the present invention provides a winding induction heating method, system and air conditioner.

A first aspect provides a winding induction heating method, comprising: establishing a relationship between a DC bus voltage and an output control duty cycle by fixing a heating target power condition; and adjusting the detected current actual DC bus voltage according to the relationship. For the corresponding duty cycle, the PWM output control is performed with the duty cycle.

Among them, "establish the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power conditions", which specifically includes: testing the compressor control system, fixing the heating target power conditions when heating the compressor, and determining different DC The bus voltage needs to correspond to different duty cycles, and the curve relationship between the DC bus voltage and the duty cycle is fitted.

Among them, "test the compressor control system, fix the heating target power conditions when the compressor is heated, determine the different duty ratios corresponding to different DC bus voltages, and fit the curve relationship between the DC bus voltage and the duty cycle. ”, which specifically includes: setting a constant heating power as the fixed heating target power condition according to the corresponding compressor model; setting the rated DC bus voltage and its fluctuation range, and setting multiple voltage values within the fluctuation range As a voltage test condition; test the duty cycle value when the constant heating power is reached under each voltage value; establish a test coordinate axis, trace the corresponding voltage value and the duty cycle value, and fit Curve trend to determine the relationship between DC bus voltage and duty cycle.

Wherein, the fluctuation range fluctuates within a range of ±20% of the rated DC bus voltage; the multiple voltage values are evenly distributed within the fluctuation range; the coordinate axis selects the voltage as the vertical axis and the duty cycle as the horizontal axis. trace.

Among them, "the detected current actual DC bus voltage is adjusted to the corresponding duty cycle according to the relationship, and the PWM output control is performed with the duty cycle", which specifically includes: when the compressor is heating, real-time detection of the compressor Control the current DC bus voltage in the system; according to the established relationship between the DC bus voltage and the duty cycle, adjust the duty cycle corresponding to the detected current DC bus voltage; perform PWM output control according to the adjusted duty cycle, In order to control the turn-on sequence of the power module of the compressor control system, the heating power when heating the compressor is kept constant.

In a second aspect, a winding induction heating system is provided, which specifically includes: a relationship module for establishing the relationship between the DC bus voltage and the output control duty cycle; The current actual DC bus voltage is adjusted to a corresponding duty cycle according to the relationship, and the PWM output control is performed with the duty cycle.

Among them, "establish the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power conditions", which specifically includes: testing the compressor control system, fixing the heating target power conditions when heating the compressor, and determining different DC The bus voltage needs to correspond to different duty cycles, and the curve relationship between the DC bus voltage and the duty cycle is fitted.

Among them, "test the compressor control system, fix the heating target power conditions when the compressor is heated, determine the different duty ratios corresponding to different DC bus voltages, and fit the curve relationship between the DC bus voltage and the duty cycle. ”, which specifically includes: setting a constant heating power as the fixed heating target power condition according to the corresponding compressor model; setting the rated DC bus voltage and its fluctuation range, and setting multiple voltage values within the fluctuation range As a voltage test condition; test the duty cycle value when the constant heating power is reached under each voltage value; establish a test coordinate axis, trace the corresponding voltage value and the duty cycle value, and fit Curve trend to determine the relationship between DC bus voltage and duty cycle.

Wherein, the fluctuation range fluctuates within a range of ±20% of the rated DC bus voltage; the multiple voltage values are evenly distributed within the fluctuation range; the coordinate axis selects the voltage as the vertical axis and the duty cycle as the horizontal axis. trace.

Among them, "the detected current actual DC bus voltage is adjusted to the corresponding duty cycle according to the relationship, and the PWM output control is performed with the duty cycle", which specifically includes: when the compressor is heating, real-time detection of the compressor Control the current DC bus voltage in the system; according to the established relationship between the DC bus voltage and the duty cycle, adjust the duty cycle corresponding to the detected current DC bus voltage; perform PWM output control according to the adjusted duty cycle, In order to control the turn-on sequence of the power module of the compressor control system, the heating power when heating the compressor is kept constant.

In a third aspect, a computer storage device is provided, the computer storage device storing a plurality of program codes, the program codes being adapted to be loaded and executed by a processor to perform the aforementioned winding induction heating method.

In a fourth aspect, a control device is provided, the control device comprising a processor and a memory, the memory device being adapted to store a plurality of pieces of program code, the program code being adapted to be loaded and run by the processor to execute the aforementioned windings Induction heating method.

In a fifth aspect, an air conditioner is provided, the air conditioner comprising the control system for induction heating of windings as described above; or, comprising: a compressor control system and the control device; a processor of the control device loads the data stored in the memory Multiple program codes and execute any of the aforementioned winding induction heating methods to detect the actual DC bus voltage of the compressor control system in real time and adjust the corresponding duty cycle according to the established relationship between the DC bus voltage and the duty cycle to perform PWM output control.

Scheme 1. A winding induction heating method, characterized in that it includes: establishing a relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition; for the detected current actual DC bus voltage, according to the relationship , adjusted to the corresponding duty cycle, and the PWM output control is performed with the duty cycle.

Option 2. The method according to Option 1, wherein “establishing the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition” specifically includes: testing the compressor control system, fixing the compressor The heating target power condition during heating is used to determine different duty ratios corresponding to different DC bus voltages, and fit the curve relationship between the DC bus voltage and the duty cycle.

Scheme 3. The method according to Scheme 2, wherein, "test the compressor control system, fix the heating target power conditions when heating the compressor, determine the different duty ratios corresponding to different DC bus voltages, and fit the "The curve relationship between the DC bus voltage and the duty cycle", which specifically includes: setting a constant heating power as the fixed heating target power condition according to the corresponding compressor model; setting the rated DC bus voltage and its fluctuation range, in the Set a plurality of voltage values within the fluctuation range as voltage test conditions; test the duty cycle value when the constant heating power is reached under each voltage value; establish a test coordinate axis, and set the corresponding voltage value Draw points with the duty cycle value, fit the trend of the curve, and determine the curve relationship between the DC bus voltage and the duty cycle.

Solution 4. The method according to solution 3, wherein the fluctuation range fluctuates within a range of ±20% of the rated DC bus voltage; the plurality of voltage values are evenly distributed within the fluctuation range; the coordinate axis selects the voltage Plot the vertical axis and the duty cycle as the horizontal axis.

Scheme 5. The method according to Scheme 4, wherein "the detected current actual DC bus voltage is adjusted to a corresponding duty cycle according to the relationship, and the PWM output control is performed with the duty cycle", specifically Including: when the compressor is heating, the current DC bus voltage in the compressor control system is detected in real time; according to the established relationship between the DC bus voltage and the duty cycle, the duty cycle is adjusted corresponding to the detected current DC bus voltage; The duty cycle is controlled by PWM output to control the turn-on sequence of the power module of the compressor control system, so as to keep the heating power constant when heating the compressor.

Scheme 6. A winding induction heating system, which is characterized in that it specifically includes: a relationship module for establishing the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition; a control module for detecting detected According to the relationship, the current actual DC bus voltage is adjusted to the corresponding duty cycle, and the PWM output control is performed with the duty cycle.

Option 7. The system according to Option 6, wherein "establishing the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition" specifically includes: testing the compressor control system, fixing the compressor The heating target power condition during heating is used to determine different duty ratios corresponding to different DC bus voltages, and fit the curve relationship between the DC bus voltage and the duty cycle.

Scheme 8. The system according to Scheme 7, wherein "test the compressor control system, fix the heating target power condition when heating the compressor, determine the different duty ratios corresponding to different DC bus voltages, and fit the "The curve relationship between the DC bus voltage and the duty cycle", which specifically includes: setting a constant heating power as the fixed heating target power condition according to the corresponding compressor model; setting the rated DC bus voltage and its fluctuation range, in the Set a plurality of voltage values within the fluctuation range as voltage test conditions; test the duty cycle value when the constant heating power is reached under each voltage value; establish a test coordinate axis, and set the corresponding voltage value Draw points with the duty cycle value, fit the trend of the curve, and determine the curve relationship between the DC bus voltage and the duty cycle.

Solution 9. The system according to solution 8, wherein the fluctuation range fluctuates within a range of ±20% of the rated DC bus voltage; the plurality of voltage values are evenly distributed within the fluctuation range; the coordinate axis selects the voltage Plot the vertical axis and the duty cycle as the horizontal axis.

Scheme 10. The system according to Scheme 9, wherein "the detected current actual DC bus voltage is adjusted to a corresponding duty cycle according to the relationship, and the PWM output control is performed with the duty cycle", specifically Including: when the compressor is heating, the current DC bus voltage in the compressor control system is detected in real time; according to the established relationship between the DC bus voltage and the duty cycle, the duty cycle is adjusted corresponding to the detected current DC bus voltage; The duty cycle is controlled by PWM output to control the turn-on sequence of the power module of the compressor control system, so as to keep the heating power constant when heating the compressor.

Aspect 11. A computer storage device storing a plurality of program codes adapted to be loaded and executed by a processor to perform the winding induction heating method of aspects 1-5.

Solution 12. A control device, the control device comprising a processor and a memory, the storage device being adapted to store a plurality of program codes, the program codes being adapted to be loaded and executed by the processor to execute the solutions of the solutions 1-5 Winding induction heating method.

Solution 13, an air conditioner, characterized in that the air conditioner includes the control system for winding induction heating according to solutions 6-10; or, includes: a compressor control system and the control device; processing of the control device The compressor loads multiple program codes in the memory and executes any of the winding induction heating methods in Schemes 1-5, detects the actual DC bus voltage of the compressor control system in real time, and adjusts the corresponding DC bus voltage according to the established relationship between the DC bus voltage and the duty cycle. duty cycle for PWM output control.

The above-mentioned one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

The technical scheme of the present invention establishes the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition; the detected current actual DC bus voltage is adjusted to the corresponding duty cycle according to the relationship, to The duty cycle performs PWM output control. In this way, when the voltage fluctuates, the duty cycle of the corresponding heating control is adjusted to adapt to the voltage fluctuation in the actual power supply environment, and the duty cycle can be adjusted quickly and conveniently to keep the heating power constant, avoiding the previous winding induction to maintain the heating power constant. Complicated and tedious experiments and the difficulty of detecting small and fast-changing currents solve the technical problem of how to easily and effectively adjust the duty cycle to control the heating power according to the fluctuation of the voltage to keep the heating power constant.

Further, the improvement of the present invention based on the winding induction heating method can adjust the duty cycle according to the DC bus voltage, and then adjust the closed-loop control heating power to ensure constant heating power, which does not require additional devices to increase costs and avoid power consumption at the same time. If it is too large, closed-loop control is also realized, so that the improved winding induction heating method not only ensures low current, low power consumption, low cost and working stability, but also realizes closed-loop control to ensure constant heating power.

Description of drawings

Specific embodiments of the present invention are described below with reference to the accompanying drawings, in which:

Fig. 1 is the main flow chart of one embodiment of the winding induction heating method according to the present invention;

2 is a structural block diagram of an embodiment of a winding induction heating system according to the present invention;

3 is a schematic diagram of a compressor control circuit according to an embodiment of the technical solution of the present invention;

FIG. 4 is a schematic diagram of the turn-on sequence of the compressor control circuit according to an embodiment of the technical solution of the present invention;

FIG. 5 is a schematic diagram of an embodiment of establishing the relationship between the DC bus voltage and the duty cycle according to the technical solution of the present invention.

Detailed ways

In order to facilitate the understanding of the invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings and examples of the specification, but those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention, and are not intended to Limit the scope of protection of the present invention.

In the description of the present invention, "module" and "processor" may include hardware, software or a combination of both. A module may include hardware circuits, various suitable sensors, communication ports, memory, and may also include software parts, such as program codes, or a combination of software and hardware. The processor may be a central processing unit, a microprocessor, an image processor, a digital signal processor, or any other suitable processor. The processor has data and/or signal processing functions. The processor may be implemented in software, hardware, or a combination of the two. Non-transitory computer-readable storage media include any suitable media that can store program code, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random-access memory, and the like. The term "A and/or B" means all possible combinations of A and B, such as just A, just B, or A and B. The terms "at least one A or B" or "at least one of A and B" have a similar meaning to "A and/or B" and can include just A, only B, or A and B. The terms "a" and "the" in the singular may also include the plural.

Among the three known ways of heating compressors by current air-conditioning equipment, the use of compressor winding iron loss induction heating has the advantages of low cost, low power consumption, safety and stability, etc., but the current of winding iron loss induction heating is small and changes rapidly. The construction of the iron loss model is complex, and the constant process of controlling the heating power through experimental data is complex and tedious. The invention provides a winding induction heating method, system and air-conditioning equipment by improving the method of winding iron loss induction heating, so as to realize the closed-loop control of winding induction heating, without adding any additional device, conveniently and effectively according to voltage fluctuations Adjust the duty cycle to control the heating power constant. An embodiment of the solution of the present invention includes: establishing the relationship between the DC bus voltage and the duty cycle under a constant heating target power; when performing winding induction heating on the compressor, according to the detected actual DC bus voltage, based on The relationship is adjusted to the duty ratio corresponding to the detected actual DC bus voltage, so as to ensure that the actual heating power and the heating target power are basically consistent under the condition of the bus voltage fluctuation.

The following are definitions and explanations of some terms involved in the present invention: (please add the following definitions)

DC bus voltage: The DC voltage that carries the inverter system from DC to AC.

Output control: refers to the control of power devices.

Duty cycle: The ratio of the on-time of a power device to the switching period.

PWM: Pulse Width Modulation, is an analog control method, which modulates the bias of the transistor base or the gate of the MOS tube according to the change of the corresponding load, so as to realize the change of the conduction time of the transistor or MOS tube, so as to realize the switching regulated power supply. Changes in output.

Referring to FIG. 1 , FIG. 1 is a main flow chart of an embodiment of a winding induction heating method according to the present invention.

Step S110, establishing the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition.

Among them, the relationship between the DC bus voltage and the output control duty ratio can be established through testing, and the relationship can be a curve relationship obtained by testing; more specifically, during testing, through existing compressor control systems such as control circuits, Fix the target heating power of the compressor that needs to be heated used in the test, provide different DC bus voltages, determine the required switching sequence to output the control duty cycle, and the corresponding duty cycle has a corresponding output PWM control, which controls the switching sequence It can ensure that the corresponding different DC bus voltages can be controlled to output the fixed target heating power, that is, the heating power is the actual value unchanged. The discrete results of these duty ratios obtained by the test correspond to different DC bus voltages, and the fitted curve ( function) to form the relationship between the DC bus voltage and the duty cycle. For example, linear relationships, etc.

The implementation process for obtaining the relationship between the DC bus voltage and the duty cycle will be described in more detail below with reference to FIGS. 3 , 4 and 5 .

Referring to FIG. 3 , a schematic diagram of a compressor control circuit according to an embodiment of the technical solution of the present invention. In the example of the control circuit, the three-phase alternating currents input to the permanent magnet motor M of the compressor are U, V, and W three phases, respectively. The figure is divided into three parts, DC bus voltage 1, power module 2, compressor 3.

In one embodiment, the DC bus voltage 1 is represented by Vdc, P represents [the positive pole of the DC bus voltage 1], N represents [the positive pole of the DC bus voltage 1], VT1 to VT6 represent [the switching part of the power device], and VD1 to VD6 Indicates [the diode part of the power device].

Specifically, a control signal can be applied to the compressor 3 through the power module 2. For example, in a switching cycle, in the first 1/2 switching cycle, VT1 is always on, VT2 and VT3 are always off, and VT4 is based on the set duty cycle. The time length is turned on; in the last 1/2 switching cycle, VT1 and VT4 are always turned off, VT2 is turned on according to the set duty cycle time length, and VT3 is always turned on. As shown in FIG. 4 , a schematic diagram of the turn-on sequence of the compressor control circuit according to an embodiment of the technical solution of the present invention, the figure schematically shows the change of the control signal of the power module 2 , wherein Ts represents the [power device switch] Period], t means [time], and the rectangular blocks from VT1 to VT6 represent [power device turn-on time].

In one embodiment, taking the above turn-on sequence as an example, VT1 is turned on in the first half of a period Ts, VT3 is turned on in the last half of a period Ts, and the turn-on time is fixed. The opening time of VT2 and VT4 is the same (that is, the opening time length is the same), and the opening time is different (VT4 is opened in the first 1/2 cycle, and VT2 is opened in 1/2 cycle after). By adjusting the turn-on time of VT2 and VT4 in one cycle Ts, respectively, the duty cycle adjustment is realized. The longer the turn-on time, the larger the duty cycle. Under other conditions being the same, the larger the duty cycle, the greater the heating power.

In one embodiment, based on the above circuit and switching sequence, a fluctuating DC bus voltage is provided, and under a fixed heating target power condition, the relationship between the corresponding fluctuating bus voltage and the duty cycle is obtained by testing.

In the following, through a specific example, the process of obtaining the relationship between the DC bus voltage and the duty cycle will be described in further detail, based on the fact that the maximum fluctuation range of the air-conditioning compressor's allowable operating voltage is ±20% of the rated voltage, combined with the above circuit and switch design. :

S1. According to the corresponding compressor model, set a reasonable heating power Wc.

S2. Within the range of ±20% of rated voltage fluctuation, set multiple/N voltage values as voltage test conditions. Further, the test voltage can be evenly distributed within this range. Here, the rated voltage is the value of the normal DC bus voltage, which corresponds to the constant heating power.

S3. Test the duty ratio of the set reasonable heating power Wc under the condition of each voltage value.

S4. After the test is completed, take the voltage as the horizontal axis and the duty cycle as the vertical axis, and trace the points.

S5. Fitting the above-mentioned curve trend FIG. 5 is a schematic diagram of an embodiment of establishing the relationship between the DC bus voltage and the duty cycle according to the technical solution of the present invention. Wherein, after the test is completed, the relationship between the DC bus voltage and the duty cycle is determined, that is, the relationship between the two is fitted with a curve, and a linear relationship between the two is established, preferably, a curve relationship between the two is established. Further, the curve fitting formula represents the relationship between the DC bus voltage and the duty cycle. Taking the Mitsubishi LNB65FBEMC compressor as an example, when the switching period is 50us, the curve of constant heating power under different DC bus voltages can be fitted as ton=(Ureal/U _N ) ² *t _N , where U _N is the rated voltage, t _N is the turn-on time for VT2 and VT4 to meet the heating target power under the rated voltage U _N , Ureal is the actual voltage, and ton is the turn-on time for VT2 and VT4 to meet the heating target power under different DC bus voltage regulation.

In one embodiment, the compressor system in the air-conditioning equipment usually includes a control circuit for controlling the compressor. When heating the compressor, the solution of the present invention does not need to add additional devices, and only uses the existing circuit to control the three-phase input to the compressor. The voltage is controlled to realize the winding induction heating, which first determines the relationship between the fluctuating DC bus voltage and the duty cycle, especially the linear relationship, so that in the compressor heating process when the voltage fluctuates, all the differences with the duty cycle can be passed. According to the above relationship, the duty cycle is adjusted and the heating power is controlled to keep constant during the PWM output.

Step S120: Adjust the detected current actual DC bus voltage to a corresponding duty cycle according to the relationship, and perform PWM output control with the duty cycle.

Among them, after establishing the relationship between the DC bus voltage and the duty ratio corresponding to the compressor to be heated, when the compressor is heating, the corresponding duty ratio is adjusted by detecting the current actual DC bus voltage change in real time.

For example: when the compressor needs to be heated after starting, the current actual DC bus voltage is detected, and according to the curve relationship, the duty cycle corresponding to the actual DC bus voltage is found, the result of the duty cycle is adjusted, and the duty cycle The result is PWM output, which is controlled by the PWM output, and its switching sequence ensures that high-frequency AC voltage is applied to the two phases of the compressor and alternately changes, which increases the hysteresis loss and eddy current loss of the ferromagnetic material of the compressor, and realizes winding induction heating, especially It is the PWM output control, corresponding to the actual DC bus voltage value, to ensure that the heating power is always kept constant.

Table 1

In one embodiment, as shown in Table 1, taking the Mitsubishi LNB65FBEMC compressor as an example, the switching period is 50us. In one switching period, VT1 and VT3 are respectively turned on for 25us in the first half cycle and the second half cycle. The turn-on time of VT2 and VT4 is adjusted according to the detected DC bus voltage. When controlling the heating of the compressor, the fixed heating target power is 50W. When the detected DC bus voltage is 425V, the turn-on time of VT2 and VT4 is adjusted to 14.7us , the duty cycle is 29%, and the actual heating power is 51.6W; when the detected DC bus voltage is 472V, the turn-on time of VT2 and VT4 is adjusted to 12.1us, the duty cycle is 24%, and the actual heating power is 51.0W; When the DC bus voltage is 525V, the turn-on time of VT2 and VT4 is adjusted to 9.8us, the duty cycle is 20%, and the actual heating power is 50.4W; when the DC bus voltage is detected to be 577V, the turn-on time of VT2 and VT4 is adjusted to 8.0us, the duty cycle is 16%, and the actual heating power is 51.1W; when the detected DC bus voltage is 643V, the on-time of VT2 and VT4 is adjusted to 6.7us, the duty cycle is 13%, and the actual heating power is 49.9W. And because the output control has changed with the voltage fluctuation to ensure that the heating power remains constant. In this way, different DC bus voltage changes are accompanied by different duty ratios, corresponding to each other, and the duty cycle can be changed at any time according to different voltage fluctuations and then the PWM output control can be changed. In the same situation, the fixed heating power is always maintained, thereby ensuring the constant control of the heating power.

The solution of the present invention can still keep the heating power of the compressor winding constant during induction heating under the condition of voltage fluctuation, without increasing the equipment cost, low power consumption, small current, convenient and effective, no complicated calculation and model construction are required, and the fixed heating The fitting curve relationship between the DC bus voltage and the duty cycle is obtained by testing under the condition of constant target power. During the heating control of the compressor of the air conditioner, once the voltage fluctuates, the duty cycle can be adjusted according to the DC bus voltage to obtain the corresponding PWM The output control ensures that the heating power/radiation power is constant; and the control program only needs to be run in the microprocessor/microcontroller MCU of the air-conditioning equipment, and the control signal output is realized to realize the scheme of the present invention, which is effective It is convenient and low in cost, realizes constant power closed-loop control without any large power consumption and cost, and does not cause extra power consumption due to self-heating of the compressor system, especially its power module.

It should be pointed out that, although the steps in the above embodiments are described in a specific sequence, those skilled in the art can understand that in order to achieve the effect of the present invention, different steps do not necessarily need to be executed in such an order. It may be performed simultaneously (in parallel) or in other sequences, and these variations are within the scope of the present invention.

Referring to FIG. 2 below, a structural block diagram of an embodiment of the winding induction heating system of the present invention is shown. The system includes at least:

The relationship module 210 is configured to establish the relationship between the DC bus voltage and the output control duty cycle by fixing the heating target power condition;

Among them, the relationship between the DC bus voltage and the output control duty ratio can be established through testing, and the relationship can be a curve relationship obtained by testing; more specifically, during testing, through existing compressor control systems such as control circuits, Fix the heating target power of the compressor that needs to be heated used in the test, provide different DC bus voltages, determine the required switching sequence to output the control duty cycle, and the corresponding duty cycle has a corresponding output PWM control, which controls the switching sequence It can ensure that the corresponding different DC bus voltages can be controlled to output the fixed heating target power, that is, the heating power is the actual value unchanged. The discrete results of these duty ratios obtained by the test correspond to different DC bus voltages, and the fitted curve ( function) to form the relationship between the DC bus voltage and the duty cycle. For example, linear relationships, etc.

The implementation process for obtaining the relationship between the DC bus voltage and the duty cycle will be described in more detail below with reference to FIGS. 3 , 4 and 5 .

Referring to FIG. 3 , a schematic diagram of a compressor control circuit according to an embodiment of the technical solution of the present invention. In the example of the control circuit, the three-phase alternating currents input to the permanent magnet motor M of the compressor are U, V, and W three phases, respectively. The figure is divided into three parts, DC bus voltage 1, power module 2, compressor 3.

In one embodiment, the DC bus voltage 1 is represented by Vdc, P represents [the positive pole of the DC bus voltage 1], N represents [the negative pole of the DC bus voltage 1], VT1 to VT6 represent [the switching part of the power device], and VD1 to VD6 Indicates [the diode part of the power device].

Specifically, a control signal can be applied to the compressor 3 through the power module 2. For example, in a switching cycle, in the first 1/2 switching cycle, VT1 is always on, VT2 and VT3 are always off, and VT4 is based on the set duty cycle. The time length is turned on; in the last 1/2 switching cycle, VT1 and VT4 are always turned off, VT2 is turned on according to the set duty cycle time length, and VT3 is always turned on. As shown in FIG. 4 , a schematic diagram of the turn-on sequence of the compressor control circuit according to an embodiment of the technical solution of the present invention, the figure schematically shows the change of the control signal of the power module 2 , wherein Ts represents the [power device switch] Period], t means [time], and the rectangular blocks from VT1 to VT6 represent [power device turn-on time].

In one embodiment, taking the above turn-on sequence as an example, VT1 is turned on in the first half of a period Ts, VT3 is turned on in the last half of a period Ts, and the turn-on time is fixed. The opening time of VT2 and VT4 is the same (that is, the opening time length is the same), and the opening time is different (VT4 is opened in the first 1/2 cycle, and VT2 is opened in 1/2 cycle after). By adjusting the turn-on time of VT2 and VT4 in one cycle Ts, respectively, the duty cycle adjustment is realized. The longer the turn-on time, the larger the duty cycle. Under other conditions being the same, the larger the duty cycle, the greater the heating power.

In one embodiment, based on the above circuit and switching sequence, a fluctuating DC bus voltage is provided, and under a fixed heating target power condition, the relationship between the corresponding fluctuating bus voltage and the duty cycle is obtained by testing.

In the following, through a specific example, the process of obtaining the relationship between the DC bus voltage and the duty cycle will be described in further detail, based on the fact that the maximum fluctuation range of the air-conditioning compressor's allowable operating voltage is ±20% of the rated voltage, combined with the above circuit and switch design. :

S1. According to the corresponding compressor model, set a reasonable heating power Wc.

S2. Within the range of ±20% of rated voltage fluctuation, set multiple/N voltage values as voltage test conditions. Further, the test voltage can be evenly distributed within this range. Here, the rated voltage is the value of the normal DC bus voltage, which corresponds to the constant heating power.

S3. Test the duty ratio of the set reasonable heating power Wc under the condition of each voltage value.

S4. After the test is completed, take the voltage as the horizontal axis and the duty cycle as the vertical axis, and trace the points.

S5. Fitting the above-mentioned curve trend FIG. 5 is a schematic diagram of an embodiment of establishing the relationship between the DC bus voltage and the duty cycle according to the technical solution of the present invention. Wherein, after the test is completed, the relationship between the DC bus voltage and the duty cycle is determined, that is, the relationship between the two is fitted with a curve, and a linear relationship between the two is established, preferably, a curve relationship between the two is established. Further, the curve fitting formula represents the relationship between the DC bus voltage and the duty cycle. Taking Mitsubishi LNB65FBEMC compressor as an example, when the switching period is 50us, the curve of constant heating power under different DC bus voltages can be fitted as ton=(Ureal/U _N ) ² *t _N , where UN is the rated voltage and tN is the rated voltage Under voltage UN, the turn-on time of VT2 and VT4 to meet the target heating power, Ureal is the actual voltage, and ton is the turn-on time of VT2 and VT4 to meet the target heating power under different DC bus voltage regulation.

In one embodiment, the compressor system in the air-conditioning equipment usually includes a control circuit for controlling the compressor. When heating the compressor, the solution of the present invention does not need to add additional devices, and only uses the existing circuit to control the three-phase input to the compressor. The voltage is controlled to realize the winding induction heating, which first determines the relationship between the fluctuating DC bus voltage and the duty cycle, especially the linear relationship, so that in the compressor heating process when the voltage fluctuates, all the differences with the duty cycle can be passed. According to the above relationship, the duty cycle is adjusted and the heating power is controlled to keep constant during the PWM output.

The control module 220 is configured to adjust the detected current actual DC bus voltage to a corresponding duty cycle according to the relationship, and perform PWM output control with the duty cycle.

Among them, after establishing the relationship between the DC bus voltage and the duty ratio corresponding to the compressor to be heated, when the compressor is heating, the corresponding duty ratio is adjusted by detecting the current actual DC bus voltage change in real time.

For example: when the compressor needs to be heated after starting, the current actual DC bus voltage is detected, and according to the curve relationship, the duty cycle corresponding to the actual DC bus voltage is found, the result of the duty cycle is adjusted, and the duty cycle The result is PWM output, which is controlled by the PWM output, and its switching sequence ensures that high-frequency AC voltage is applied to the two phases of the compressor and alternately changes, which increases the hysteresis loss and eddy current loss of the ferromagnetic material of the compressor, and realizes winding induction heating, especially It is the PWM output control, corresponding to the actual DC bus voltage value, to ensure that the heating power is always kept constant.

Table 1

In one embodiment, as shown in Table 1, taking the Mitsubishi LNB65FBEMC compressor as an example, the switching period is 50us. In one switching period, VT1 and VT3 are respectively turned on for 25us in the first half cycle and the second half cycle. The turn-on time of VT2 and VT4 is adjusted according to the detected DC bus voltage. When controlling the heating of the compressor, the fixed heating target power is 50W. When the detected DC bus voltage is 425V, the turn-on time of VT2 and VT4 is adjusted to 14.7us , the duty cycle is 29%, and the actual heating power is 51.6W; when the detected DC bus voltage is 472V, the turn-on time of VT2 and VT4 is adjusted to 12.1us, the duty cycle is 24%, and the actual heating power is 51.0W; When the DC bus voltage is 525V, the turn-on time of VT2 and VT4 is adjusted to 9.8us, the duty cycle is 20%, and the actual heating power is 50.4W; when the DC bus voltage is detected to be 577V, the turn-on time of VT2 and VT4 is adjusted to 8.0us, the duty cycle is 16%, and the actual heating power is 51.1W; when the detected DC bus voltage is 643V, the on-time of VT2 and VT4 is adjusted to 6.7us, the duty cycle is 13%, and the actual heating power is 49.9W. And because the output control has changed with the voltage fluctuation to ensure that the heating power remains constant. In this way, different DC bus voltage changes are accompanied by different duty ratios, corresponding to each other, and the duty cycle can be changed at any time according to different voltage fluctuations and then the PWM output control can be changed. In the same situation, the fixed heating power is always maintained, thereby ensuring the constant control of the heating power.

An example of an application scenario of the technical solution of the present invention is described below to further illustrate the implementation of the present invention:

The air conditioner is equipped with a compressor control system, as shown in Figure 3. The compressor control system includes a permanent magnet motor M (compressor) part 3, the voltage input to the permanent magnet motor M includes three-phase U, V and W, and this part also returns the oil pool. The compressor control system also includes a DC bus voltage Vdc part 1 connected to the input power supply terminal, and a power module part 2 . The DC bus voltage Vdc part 1 applies a control signal to the compressor part 3 through the power module part 2 to control the on-off of VT1 to VT6, for example, the switching sequence shown in FIG. 4 . For example: in a switching cycle, in the first 1/2 switching cycle, VT1 is always on, VT2 and VT3 are always off, and VT4 is turned on according to the set duty cycle time; in the last 1/2 switching cycle, VT1 and VT4 are always on. Turn off, VT2 is turned on according to the set duty cycle time length, and VT3 is always turned on. VT5 and VT6 are always off. In the turn-on sequence of the switch, VT1 and VT3 have been turned on for 1/2 cycles before and after respectively. The opening time of VT2 and VT4 is different, and the opening time is the same. In this way, the duty cycle can be adjusted by adjusting the turn-on time of VT2 and VT4. The longer the turn-on time, the larger the duty cycle. Under the same other conditions, the duty cycle increases, the current flowing through the winding increases, and the magnetic flux increases accordingly, and the eddy current loss and hysteresis loss of the winding are proportional to the magnetic flux. , so the heating power increases. In this way, the fluctuating voltage range is set corresponding to the compressor. Under this range of voltage, the voltage is evenly distributed. Under each voltage value, the DC bus voltage is determined, and the turn-on sequence under the condition of fixed heating target power is tested to determine the duty cycle result. , 30%, 50%, 80%, etc. After the test is completed, the corresponding duty cycle value is plotted against the DC bus voltage value, and the curve relationship between the DC bus voltage value and the duty cycle value is fitted. When the air-conditioning compressor needs to control heating, the current actual DC bus voltage value detected in real time is adjusted according to the curve relationship, so that the PWM output control is performed according to the duty cycle. Specifically, the VT1 of the power module part 2 can be realized. The control of the time until VT6 is turned on changes accordingly, so that the whole heating process can maintain a constant heating power.

Further, in an embodiment of a computer storage medium of the present invention, the computer storage medium stores a plurality of program codes, and the program codes are adapted to be loaded and executed by a processor to execute any one of the foregoing winding induction heating methods.

Further, in an embodiment of a control device of the present invention, it includes a processor and a memory, the storage device is adapted to store a plurality of program codes, and the program codes are adapted to be loaded and run by the processor to execute the foregoing Either winding induction heating method. Further, the control device may be, for example, an MCU in an air conditioner or the like.

Further, in an embodiment of an air conditioner of the present invention, it includes: any one of the foregoing winding induction heating systems; or, includes: a compressor control system and the foregoing control device. Specifically, the processor of the control device loads a plurality of program codes in the memory and executes any one of the above-mentioned winding induction heating methods, detects the actual DC bus voltage of the compressor control system in real time, and according to the established DC bus voltage and duty cycle The relationship of , adjust the corresponding duty cycle for PWM output control. Further, the PWM output controls the turn-on sequence of the switches in the power module to keep the heating power of the compressor heating constant.

Those skilled in the art can understand that all or part of the process in the method for implementing the above-mentioned embodiment of the present invention can also be completed by instructing relevant hardware through a computer program, and the computer program can be stored in a computer-readable In the storage medium, when the computer program is executed by the processor, the steps of the foregoing method embodiments can be implemented. Wherein, the computer program includes computer program code, and the computer program code may be in the form of source code, object code, executable file or some intermediate form, and the like. The computer-readable medium may include: any entity or device capable of carrying the computer program code, medium, U disk, removable hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal , telecommunication signals, and software distribution media. It should be noted that the content contained in the computer-readable media may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable media Electric carrier signals and telecommunication signals are not included.

Further, it should be understood that since the setting of each module is only for describing the functional units of the system of the present invention, the physical device corresponding to these modules may be the processor itself, or a part of software in the processor, a part of hardware, or Part of the combination of software and hardware. Therefore, the numbers of the various modules in the figures are merely schematic.

Those skilled in the art can understand that each module in the system can be divided or merged adaptively. Such splitting or merging of specific modules will not cause the technical solutions to deviate from the principles of the present invention, and therefore, the technical solutions after splitting or combining will fall within the protection scope of the present invention.

So far, the technical solutions of the present invention have been described with reference to one embodiment shown in the accompanying drawings, but those skilled in the art can easily understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims (10)

1. A method of winding induction heating, comprising:

establishing a relation between the direct current bus voltage and an output control duty ratio by fixing a heating target power condition;

and adjusting the detected current actual direct-current bus voltage into a corresponding duty ratio according to the relation, and performing PWM output control according to the duty ratio.

2. The method according to claim 1, wherein the establishing a relationship between the dc bus voltage and the output control duty cycle by fixing the heating target power condition specifically comprises:

testing a compressor control system, fixing a heating target power condition when the compressor is heated, determining different duty ratios corresponding to different direct current bus voltages, and fitting a curve relation between the direct current bus voltages and the duty ratios.

3. The method according to claim 2, wherein the step of testing a compressor control system, fixing a heating target power condition when the compressor is heated, determining different duty ratios corresponding to different dc bus voltages, and fitting a curve relationship between the dc bus voltages and the duty ratios specifically comprises:

setting a constant heating power as a fixed heating target power condition according to the corresponding compressor model;

setting rated direct current bus voltage and a fluctuation range thereof, and setting a plurality of voltage values in the fluctuation range as voltage test conditions;

testing the duty ratio value when the constant heating power is reached under each voltage value;

and establishing a test coordinate axis, performing point tracing on the corresponding voltage value and the duty ratio value, fitting a curve trend, and determining a curve relation between the direct-current bus voltage and the duty ratio.

4. The method of claim 3, wherein,

the fluctuation range fluctuates within the range of +/-20% of rated direct current bus voltage;

the voltage values are evenly distributed in the fluctuation range;

and the coordinate axis is plotted with the voltage as the vertical axis and the duty ratio as the horizontal axis.

5. The method according to claim 4, wherein the step of adjusting the detected current actual dc bus voltage to a corresponding duty ratio according to the relationship, and performing PWM output control with the duty ratio specifically includes:

when the compressor is heated, detecting the current direct current bus voltage in a compressor control system in real time;

according to the established relation between the direct current bus voltage and the duty ratio, correspondingly detecting the current direct current bus voltage, and adjusting the duty ratio;

and performing PWM output control according to the adjusted duty ratio to control the opening time sequence of the power module of the compressor control system and keep the heating power constant when the compressor is heated.

6. A winding induction heating system, characterized by specifically comprising:

the relation module is used for establishing the relation between the direct-current bus voltage and the output control duty ratio by fixing the heating target power condition;

and the control module is used for adjusting the detected current actual direct-current bus voltage into a corresponding duty ratio according to the relation and performing PWM output control according to the duty ratio.

7. The system according to claim 6, wherein the establishing a relationship between the dc bus voltage and the output control duty cycle by fixing the heating target power condition specifically includes:

testing a compressor control system, fixing a heating target power condition when the compressor is heated, determining different duty ratios corresponding to different direct current bus voltages, and fitting a curve relation between the direct current bus voltages and the duty ratios.

8. The system of claim 7, wherein the step of testing a compressor control system, fixing a heating target power condition when the compressor is heated, determining different duty ratios corresponding to different dc bus voltages, and fitting a curve relationship between the dc bus voltages and the duty ratios specifically comprises:

setting a constant heating power as a fixed heating target power condition according to the corresponding compressor model;

setting rated direct current bus voltage and a fluctuation range thereof, and setting a plurality of voltage values in the fluctuation range as voltage test conditions;

testing the duty ratio value when the constant heating power is reached under each voltage value;

and establishing a test coordinate axis, performing point tracing on the corresponding voltage value and the duty ratio value, fitting a curve trend, and determining a curve relation between the direct-current bus voltage and the duty ratio.

9. The system of claim 8, wherein,

the fluctuation range fluctuates within the range of +/-20% of rated direct current bus voltage;

the voltage values are evenly distributed in the fluctuation range;

and the coordinate axis is plotted with the voltage as the vertical axis and the duty ratio as the horizontal axis.

10. The system according to claim 9, wherein the step of adjusting the detected current actual dc bus voltage to a corresponding duty ratio according to the relationship, and performing PWM output control with the duty ratio specifically includes:

when the compressor is heated, detecting the current direct current bus voltage in a compressor control system in real time;

according to the established relation between the direct current bus voltage and the duty ratio, correspondingly detecting the current direct current bus voltage, and adjusting the duty ratio;

and performing PWM output control according to the adjusted duty ratio to control the opening time sequence of the power module of the compressor control system and keep the heating power constant when the compressor is heated.

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