Circuit control method based on PWM (Pulse Width Modulation) control signal and low-harmonic inverter circuit

Abstract

The invention relates to the technical field of electronic circuits, and provides a circuit control method based on PWM control signals and a low-harmonic inverter circuit. According to the circuit control method based on the PWM control signal, the target output voltage, the target output frequency and the carrier frequency of a low-harmonic inverter circuit are obtained, the modulation ratio is determined according to the target output voltage, and the carrier period is determined according to the carrier frequency. And determining on and off time according to the target output frequency, the modulation ratio and the carrier period, and finally obtaining a PWM control signal according to the on and off time for controlling on and off of an inversion module in the low-harmonic inversion circuit. Therefore, the turn-on and turn-off time of each IGBT in the inverter module can be accurately controlled, so that the low-harmonic inverter circuit has the characteristics of high efficiency, stability, low power consumption and the like, can stably operate under various working conditions, has good overall performance, and is suitable for the application fields such as motor driving of a compressor in air conditioning equipment and the like.

Description

[0001] This application is a divisional application of the invention patent application filed on May 30, 2024, with the invention name “Low harmonic inverter circuit, control method, compressor drive device and air-conditioning equipment” and application number 2024106878013. Technical Field

[0002] The present invention relates to the field of electronic circuits, and in particular to a circuit control method based on PWM control signals and a low harmonic inverter circuit. Background Art

[0003] In the field of power electronics, inverter circuits are widely used in various motor drive systems, including compressor motor drives in air-conditioning equipment. Air-conditioning compressor inverters are the core components of modern air-conditioning systems. However, the inverter circuit control methods in related technologies often use simple modulation techniques, which makes it difficult to accurately control the on and off time of the IGBT. As a result, high harmonic content is easily generated under certain working conditions, and the motor heats up, vibrates, and increases noise, resulting in a low power factor and reduced overall energy efficiency. It also affects the stability and overall efficiency of the system. Summary of the invention

[0004] In view of this, the embodiments of the present invention provide a circuit control method based on a PWM control signal and a low harmonic inverter circuit to solve the problems of high harmonic content of circuit current, low power factor and low efficiency in the prior art.

[0005] In a first aspect, an embodiment of the present invention provides a circuit control method based on a PWM control signal, which is applied to a low harmonic inverter circuit, and is characterized in that the method includes:

[0006] Obtaining a target output voltage, a target output frequency, and a carrier frequency of the low harmonic inverter circuit;

[0007] Determining the modulation ratio of the low harmonic inverter circuit according to the target output voltage includes: determining the modulation ratio of the low harmonic inverter circuit according to the ratio of the target output voltage to the DC side voltage; wherein the DC side voltage is the DC voltage output by the rectifier module in the low harmonic inverter circuit;

[0008] Determining a carrier period according to the carrier frequency;

[0009] Determining the on and off time according to the target output frequency, the modulation ratio and the carrier period;

[0010] A PWM control signal is acquired according to the on and off time, and the PWM control signal is used to control the on and off of the inverter module in the low harmonic inverter circuit.

[0011] Preferably, determining the on and off time according to the target output frequency, the modulation ratio and the carrier period includes:

[0012] generating a reference sine wave according to the target output frequency and the modulation ratio;

[0013] generating a triangular carrier according to the carrier cycle;

[0014] The reference sine wave and the triangular carrier are compared to determine the turn-on and turn-off time of each IGBT in the inverter module.

[0015] Preferably, generating a reference sine wave according to the target output frequency and the modulation ratio comprises:

[0016] Calculating the angular frequency of the reference sine wave according to the target output frequency;

[0017] Determining the peak amplitude of the reference sine wave according to the modulation ratio and the DC side voltage;

[0018] A waveform of the reference sine wave is generated according to the angular frequency and the peak amplitude.

[0019] Preferably, generating a triangular carrier according to the carrier period includes:

[0020] In each of the carrier cycles, the value of the carrier increases linearly until it reaches a maximum value, and then decreases linearly to a minimum value, forming a sawtooth or triangular waveform.

[0021] Preferably, the comparing the reference sine wave and the triangular carrier to determine the turn-on and turn-off time of each IGBT in the inverter module includes:

[0022] Acquire the instantaneous value of the reference sine wave and the instantaneous value of the triangular carrier at different time parameters of the control cycle;

[0023] Comparing the instantaneous value of the reference sine wave with the instantaneous value of the triangular carrier;

[0024] When the instantaneous value of the reference sine wave is greater than the instantaneous value of the triangular carrier, each IGBT in the inverter module is set to an on state at the time parameter setting;

[0025] When the instantaneous value of the reference sine wave is less than the instantaneous value of the triangular carrier, each IGBT in the inverter module is set to an off state at the time parameter.

[0026] Preferably, the method further comprises:

[0027] Determining the dead time of the inverter module;

[0028] Determine a compensation increment corresponding to the dead time according to the total period of the PWM control signal and the modulation ratio;

[0029] Acquire a new modulation ratio according to the compensation increment and the modulation ratio;

[0030] The duty cycle of the PWM control signal is set according to the new modulation ratio.

[0031] Preferably, determining the compensation increment corresponding to the dead time according to the total period of the PWM control signal and the modulation ratio includes:

[0032] Calculating the ratio of the dead time to the total period of the PWM control signal to obtain a ratio result;

[0033] The ratio result and the modulation ratio are multiplied to obtain the compensation increment; wherein the compensation increment is the portion of the modulation ratio lost due to the dead time.

[0034] In a second aspect, the present invention provides a low harmonic inverter circuit, applying the circuit control method based on PWM control signal in the first aspect of the above-mentioned embodiment, the low harmonic inverter circuit comprises:

[0035] A filter lightning protection module, a pre-charging module, a rectifier module, a DC bus filter module and an inverter module which are electrically connected in sequence;

[0036] The filtering and lightning protection module is electrically connected to the pre-charging module, and the filtering and lightning protection module includes an electrically connected capacitor, a fuse, a varistor and an inductor, which are used to suppress electromagnetic interference signals;

[0037] The pre-charging module is electrically connected to the filtering and lightning protection module and the rectifying module respectively, and the pre-charging module includes an electrically connected capacitor, a resistor and a switch for current limiting when the circuit is powered on;

[0038] The rectifier module is electrically connected to the pre-charging module and the DC bus filter module respectively, and the rectifier module includes an electrically connected inductor, a diode and a switch tube, and is used to rectify the AC input current into a DC current, and control the input current waveform so that the harmonic content of the input current meets the preset requirements;

[0039] The DC bus filter module is electrically connected to the rectifier module and the inverter module respectively, and the DC bus filter module includes a capacitor for smoothing and filtering the rectified DC bus voltage;

[0040] The inverter module is electrically connected to the DC bus filter module, and the inverter module includes an IGBT unit for converting the rectified DC current into an AC output current, wherein the output current is used to drive the motor.

[0041] Preferably, the low harmonic inverter circuit further includes: a first control module;

[0042] The first control module includes a first DSP unit, a first EEPROM unit, an output voltage processing unit, a first driving and protection circuit unit, a current signal processing unit, and a voltage signal processing unit;

[0043] Among them, the current signal processing unit is used to access the current signal detected by the ammeter set between the pre-charging module and the rectifier module, the voltage signal processing unit is used to access the voltage signal output by the filtering and lightning protection module, and the output voltage processing unit is used to adjust the voltage signal input to the inverter module.

[0044] Preferably, the low harmonic inverter circuit further includes a second control module;

[0045] The second control module includes an ARM unit, a second DSP unit, a second EEPROM unit, a second driving and protection circuit unit, a control I / O interface unit, an output current processing unit, and a communication unit;

[0046] Wherein, the output current processing unit is used to access the output current signal of the inverter module.

[0047] In summary, the beneficial effects of the present invention are as follows:

[0048] The circuit control method based on PWM control signal and low harmonic inverter circuit provided by the embodiment of the present invention, wherein the circuit control method based on PWM control signal obtains the target output voltage, target output frequency and carrier frequency of the low harmonic inverter circuit, determines the modulation ratio according to the target output voltage, and determines the carrier period according to the carrier frequency. Then, the on-off time is determined according to the target output frequency, the modulation ratio and the carrier period, and finally the PWM control signal is obtained according to the on-off time to control the on-off of the inverter module in the low harmonic inverter circuit. In this way, the on-off time of each IGBT in the inverter module is accurately controlled, so that the low harmonic inverter circuit has the characteristics of high efficiency, stability, low power consumption, etc., can operate stably under various working conditions, has good overall performance, and is suitable for application fields such as motor drive of compressors in air-conditioning equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings required for use in the embodiment of the present invention will be briefly introduced below. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work, and these are all within the protection scope of the present invention.

[0050] Figure 1 It is a structural schematic diagram of a low harmonic inverter circuit according to an embodiment of the present invention.

[0051] Figure 2 It is a specific circuit diagram of the low harmonic inverter circuit of an embodiment of the present invention.

[0052] Figure 3 It is a flow chart of a low harmonic inverter circuit control method according to an embodiment of the present invention.

[0053] Figure 4 1 is a schematic structural diagram of a compressor driving device according to an embodiment of the present invention.

[0054] Figure 5 Schematic diagram of the structure of the air conditioning device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0055] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention.

[0056] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "include..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. The implementation method described below is only schematic, and the division of the module or circuit is only a logical function division, and there may be other division methods when actually implemented. In this embodiment and the accompanying drawings, the elements unrelated to the present invention have been omitted and not illustrated, and the size relationship between the elements in the accompanying drawings is only for easy understanding, not for limiting the actual proportion.

[0057] See also Figure 1An embodiment of the present invention provides a low harmonic inverter circuit, which includes: a filter lightning protection module 1, a pre-charging module 2, a rectifier module 3, a DC bus filter module 4 and an inverter module 5 which are electrically connected in sequence, wherein the filter lightning protection module 1 is electrically connected to the pre-charging module 2, the pre-charging module 2 is electrically connected to the filter lightning protection module 1 and the rectifier module 3 respectively, the rectifier module 3 is electrically connected to the pre-charging module 2 and the DC bus filter module 4 respectively, the DC bus filter module 4 is electrically connected to the rectifier module 3 and the inverter module 5 respectively, and is used for smoothing and filtering the rectified DC bus voltage; the inverter module 5 is electrically connected to the DC bus filter module 4. The filtering and lightning protection module 1 includes several electrically connected capacitors, fuses, varistors and inductors, which are used to suppress EMI signals and prevent signal interference between the circuit and external devices, such as preventing the low harmonic inverter circuit from interfering with external devices or external devices from interfering with the normal operation of the low harmonic inverter circuit; the pre-charging module 2 includes several electrically connected capacitors, resistors and switches, which are used to limit the current when the circuit is powered on; the rectifier module 3 includes several electrically connected inductors, diodes and switching tubes, which are used to rectify the AC input current into DC current, and control the input current waveform so that the harmonic content of the input current meets the preset requirements; the DC bus filter module 4 includes several capacitors, which are used to smooth and filter the rectified DC bus voltage; the inverter module 5 includes several IGBT units, which are used to convert the rectified DC current into an AC output current, wherein the output current is used to drive the motor.

[0058] In one embodiment, see Figure 2 The low harmonic inverter circuit is suitable for application scenarios using three-phase AC current as input current. The low harmonic inverter circuit includes a first input port CON1, a second input port CON2 and a third input port CON3, which are respectively connected to the first phase current R, the second phase current S and the third phase current T of the input current. Each phase AC current is input from the first input port CON1, the second input port CON2 and the third input port CON3, and is filtered by the filtering and lightning protection module.

[0059] In one embodiment, Figure 2As shown, the filtering and lightning protection module includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, capacitor C8, capacitor C9, capacitor C10, capacitor C11, fuse FU1, fuse FU2, fuse FU3, varistor RV1, varistor RV2, varistor RV3, inductor L11, inductor L12, inductor L13, inductor L21, inductor L22 and inductor L23, wherein one end of capacitor C1 is electrically connected to the first input port and the other end is electrically connected to the grounded inner shell, and one end of fuse FU1 is electrically connected to the grounded inner shell. The first input port is electrically connected to the second input port, and the other end is electrically connected to the inductor L11, the other end of the inductor L11 is electrically connected to the inductor L21, and the other end of the inductor L21 is electrically connected to the pre-charge module. One end of the capacitor C4 is electrically connected to the connection point of the inductor L11 and the inductor L21, and the other end is electrically connected to the grounded inner shell. The varistor RV1 is connected in series between the fuse FU1 and the fuse FU2; one end of the capacitor C2 is electrically connected to the second input port, and the other end is electrically connected to the grounded inner shell. One end of the fuse FU2 is electrically connected to the second input port, and the other end is electrically connected to the inductor L12. , the other end of the inductor L12 is electrically connected to the inductor L22, and the other end of the inductor L22 is electrically connected to the pre-charge module; one end of the capacitor C5 is electrically connected to the connection point of the inductor L12 and the inductor L22, and the other end is electrically connected to the grounded inner shell through the capacitor C10, and the varistor RV2 is connected in series between the fuse FU1 and the fuse FU3; one end of the capacitor C3 is electrically connected to the third input port, and the other end is electrically connected to the grounded inner shell, one end of the fuse FU3 is electrically connected to the third input port, and the other end is electrically connected to the inductor L13, and the other end of the inductor L13 is electrically connected to the inductor L2 3 is electrically connected, the other end of the inductor L23 is electrically connected to the pre-charge module, one end of the capacitor C6 is electrically connected to the connection point of the inductor L13 and the inductor L23, and the other end is connected to the grounded inner shell through the capacitor C10, and the varistor RV3 is connected in series between the fuse FU2 and the fuse FU3; one end of the capacitor C7 is electrically connected to the inductor L22, and the other end is electrically connected to the grounded inner shell through the capacitor C11, one end of the capacitor C8 is electrically connected to the inductor L21, and the other end is electrically connected to the grounded inner shell through the capacitor C11, and one end of the capacitor C9 is electrically connected to the inductor L23, and the other end is electrically connected to the grounded inner shell through the capacitor C11. In the filter lightning protection module 1, the fuses FU1, FU2, and FU3 are used to protect circuits and equipment from damage caused by overcurrent. For example, when the input current exceeds the rated value of the fuse, the fuse will disconnect the circuit, cut off the current, and prevent damage caused by circuit overload. The series-connected varistors RV1, RV2, and RV3 can adjust the parameters of the circuit according to actual application requirements to meet specific filtering and resistance requirements, thereby helping to adjust the performance of the circuit.Inductors L11, L12, L13, L21, L22, and L23 are used together with capacitors C4, C5, C6, C7, C8, C9, C10, and C11 for filtering and lightning protection, and reduce harmonics and suppress electromagnetic interference by adjusting the waveform of the input current. The above components work together to achieve the purpose of filtering and lightning protection, and protect the normal and stable operation of the entire circuit.

[0060] In one embodiment, Figure 2 As shown, the pre-charging module 2 includes a relay K1, a relay K2, a resistor R1 and a resistor R2, wherein one end of the parallel relay K1 and the resistor R1 is electrically connected to the inductor L21 of the filter lightning protection module 1, and the other end is electrically connected to the rectifier module 3, and one end of the parallel relay K2 and the resistor R2 is electrically connected to the inductor L23 of the filter lightning protection module 1, and the other end is electrically connected to the rectifier module 3. At the moment of power-on, the bus capacitors E1 and E2 in the low harmonic inverter circuit are equivalent to short circuits, and there is a large impact current. In order to prevent the adverse effects of the current impact on the circuit and ensure the stable startup and operation of the circuit, in an embodiment of the present invention, the current at power-on is limited by resistors R1 and R2. When the bus capacitors E1 and E2 are fully charged, the relays K1 and K2 are closed. After closing, the input current bypasses the resistors R1 and R2 to ensure that the circuit can operate normally and efficiently.

[0061] In one embodiment, Figure 2As shown, the rectifier module 3 is a three-phase Vienna rectifier, including: an inductor L3, an inductor L4, an inductor L5, a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a switch tube Q1, a switch tube Q2, a switch tube Q3, a switch tube Q4, a switch tube Q5, and a switch tube Q6, wherein the diode D1, the diode D2, the diode D3, the diode D4, the diode D5, and the diode D6 form a three-phase uncontrolled rectifier bridge, the switch tube Q1 and the switch tube Q2 are connected in series to form a first bidirectional switch group, the switch tube Q3 and the switch tube Q4 are connected in series to form a second bidirectional switch group, and the switch tube Q4 and the switch tube Q5 are connected in series to form a third bidirectional switch group, and one end of the inductor L3 is electrically connected The resistor R1 of the pre-charge module is electrically connected to the first bridge arm composed of diode D1 and diode D5 in the three-phase uncontrolled rectifier bridge at one end; the inductor L4 is electrically connected to the inductor L22 of the filter lightning protection module at one end, and electrically connected to the second bridge arm composed of diode D2 and diode D6 in the three-phase uncontrolled rectifier bridge at the other end; the inductor L3 is electrically connected to the resistor R2 of the pre-charge module at one end, and electrically connected to the third bridge arm composed of diode D3 and diode D6 in the three-phase uncontrolled rectifier bridge at the other end, and the first bidirectional switch group, the second bidirectional switch group and the third bidirectional switch group are electrically connected to the first bridge arm, the second bridge arm and the third bridge arm at one end, respectively, and the other ends are electrically connected to the busbar DC module. The three-phase Vienna rectifier is used to rectify the AC input current into DC current, and at the same time control the waveform of the input current, so that the harmonic content of the input current meets the specification requirements. Among them, the three input boost filter inductors L3, L4, and L5 are used for boosting and filtering, and reducing harmonic content. The three-phase uncontrolled rectifier bridge composed of six diodes is used to convert the input AC current into DC current. The uncontrollable here means that the diodes in the bridge cannot be actively controlled, but are only turned on according to the positive and negative half cycles of the input voltage. However, by connecting two reverse-series power MOSFETs (bidirectional switch groups) between each phase of the rectifier bridge, the current direction is controlled so that it can flow in both directions, thereby realizing the power factor correction (PFC) function, improving the power factor, and achieving more efficient and stable AC to DC conversion.

[0062] In one embodiment, see Figure 2The DC bus filter module 4 includes capacitor E1, capacitor E2 and capacitor C0, wherein capacitor E1 and capacitor E2 are connected in series, capacitor C0 is connected in parallel with the series-connected capacitors E1 and E2, the series-connected capacitors E1, E2 and capacitor C0 are connected between the output ports of the three-phase uncontrolled rectifier bridge, and the connection point of capacitor E1 and capacitor E2 is electrically connected to the first bidirectional switch group, the second bidirectional switch group and the third bidirectional switch group respectively. The DC bus filter capacitors E1, E2 and C0 are used to smooth and filter the rectified DC bus voltage, reduce the bus voltage ripple, improve the stability of the DC bus, and ensure that the circuit works under good voltage conditions.

[0063] In one embodiment, Figure 2 As shown, the DC current input by the DC bus filter module enters the inverter module 5, which is a three-phase inverter. The three-phase inverter is composed of three groups of IGBT units, wherein I1 and I2 form a group of IGBT units, I3 and I4 form a group of IGBT units, and I5 and I6 form a group of IGBT units. Each group of IGBTs converts one phase of DC current into AC current and outputs it, thereby realizing the frequency conversion and voltage conversion function.

[0064] In one embodiment, Figure 2 As shown, the low harmonic inverter circuit also includes a first control module 6 and a second control module 7, wherein the first control module 6 includes a first DSP unit, a first EEPROM unit, an output voltage processing unit, a first drive and protection circuit unit, a current signal processing unit, and a voltage signal processing unit, wherein the current signal processing unit is used to access the current signal detected by the ammeter set between the pre-charge module and the rectifier module, the voltage signal processing unit is used to access the voltage signal output by the filter lightning protection module, and the output voltage processing unit is used to adjust the voltage signal input to the inverter module; the second control module 7 includes a first ARM unit, a second DSP unit, a second EEPROM unit, a second drive and protection circuit unit, a control I / O interface unit, an output current processing unit, and a communication unit, wherein the output current processing unit is used to access the output current signal of the inverter module. The voltage and current signals before entering the rectifier module 3 are detected by the first control module, and the PWM control signal is output to the inverter module 5 after calculation according to the detection result, so as to realize the power change and input power factor calibration function. In addition, the first drive and protection unit and the second drive and protection unit, which are electrically connected to the first control module 6 and the second control module 7 respectively, are used to realize signal isolation and power amplification. The IGBT drive signal generated by the first control module 6 is isolated and amplified by the first drive and protection unit, and then drives the IGBT unit of the Vienna rectifier and the inverter module, thereby realizing power change.

[0065] In one embodiment, Figure 2 As shown, the low harmonic inverter circuit also includes a control panel module 8, wherein the control panel module 8 includes a combination of a keyboard and a display, or a touch screen. The control panel module 8 is used to monitor and control the operation of the low harmonic inverter circuit. The display or touch screen can output information such as input voltage and current or output voltage and current in the circuit, monitor the operation and stop status of the inverter, and the user can input control parameters into the second control module 7 through the keyboard or touch screen to adjust the power change in the circuit and control the simple operation of the circuit.

[0066] In summary, the low harmonic inverter circuit provided by the embodiment of the present invention effectively suppresses the electromagnetic interference (EMI) signal through the filtering and lightning protection module, improves the anti-interference ability of the circuit, and enables it to operate stably under complex electromagnetic environment conditions. The pre-charging module ensures the stable startup of the circuit at the moment of power-on through the current limiting mechanism, prevents the impact current from causing adverse effects on the system, and improves the reliability of the system; the rectifier module realizes the conversion from AC to DC, and by controlling the input current waveform, the input harmonic content meets the preset requirements and realizes the power factor correction function; the DC bus filter module smoothes and filters the rectified DC bus voltage, reduces the ripple, and improves the stability of the DC voltage. The inverter module realizes the frequency conversion and voltage conversion function of the DC current, so that the circuit can adapt to different motor working conditions and improve the efficiency and control accuracy of the motor. By integrating the above modules, the low harmonic inverter circuit of the present invention has the characteristics of high efficiency, stability, low power consumption, etc., can operate stably under various working conditions, has good overall performance, and is suitable for application fields such as motor drive of compressors in air-conditioning equipment.

[0067] Embodiment 2

[0068] Based on the low harmonic inverter circuit described in the above embodiment 1, the embodiment of the present invention provides a low harmonic inverter circuit control method, see Figure 3 , the method comprises the following steps:

[0069] S1: Obtaining the target output voltage, target output frequency and carrier frequency of the low harmonic inverter circuit;

[0070] S2: Determine the modulation ratio of the low harmonic inverter circuit according to the target output voltage value;

[0071] S3: Determine a carrier period according to the carrier frequency;

[0072] S4: Determine the on and off time according to the target output frequency, the modulation ratio and the carrier period;

[0073] S5: Acquire a PWM control signal according to the on and off time, wherein the PWM control signal is used to control the on and off of the inverter module of the low harmonic inverter circuit.

[0074] Specifically, to use an AC low harmonic inverter circuit to perform frequency conversion control on an AC motor, it is necessary to control the IGBT devices (such as Figure 2 The on and off time of the six IGBTs (I1, I2, I3, I4, I5, I6) in the inverter module 5 shown in the figure makes the output line voltage fundamental wave of the inverter circuit a sine wave, and uses sine voltages of different frequencies and voltages to control the speed of the AC motor. In this embodiment, the PWM drive signal for driving the inverter module to turn on and off is determined by obtaining the target output voltage and carrier frequency of the inverter circuit to realize the turning on and off of each IGBT. The target output voltage, target output frequency and carrier frequency here can be determined according to actual conditions. In one embodiment, it can be determined by Figure 2 The control panel module shown in the figure inputs the corresponding value. After obtaining the target output voltage and carrier frequency, the modulation ratio of the inverter circuit is calculated using the output voltage, the carrier period is calculated using the carrier frequency setting, the on and off time of each IGBT is calculated using the PWM method, and the PWM control signal output to the inverter module is generated by controlling the PWM related control register in the first DSP unit, and each IGBT in the inverter module is turned on or off according to the PWM control signal.

[0075] In one embodiment, the modulation ratio of the low harmonic inverter circuit is determined according to the ratio of the target output voltage value and the DC side voltage; the carrier period is determined according to the inverse of the carrier frequency; the DC side voltage here is the DC voltage output by the rectifier module.

[0076] In one embodiment, determining the on and off time according to the output frequency, the modulation ratio and the carrier period includes:

[0077] generating a reference sine wave and a triangular carrier according to the output frequency, the modulation ratio and the carrier period;

[0078] The reference sine wave and the triangular carrier are compared to determine the turn-on and turn-off time of each IGBT in the inverter module.

[0079] Specifically, the frequency of the reference sine wave determines the frequency of the inverter output voltage, while its amplitude is controlled by the modulation ratio. The reference sine wave is obtained by the following steps: ref Calculate the angular frequency of the reference sine wave ω=2πf ref ; Using modulation ratio m and DC voltage V dc To determine the peak amplitude of the reference sine wave A = m × Vdc / 2; Generate waveform: In each control cycle T, calculate the value of the reference sine wave V(t)=Asin(ωt), where t is the current time.

[0080] The triangular carrier is a high-frequency waveform used for comparison with the reference waveform. The carrier frequency is usually much higher than the frequency of the reference sine wave to ensure that enough PWM switching points are generated to improve the quality of the output waveform. The triangular carrier is obtained by: According to the carrier frequency f carrier Get the carrier period T carrier =1 / f carrier Finally, within each carrier cycle, the value of the carrier is linearly increased until it reaches the maximum value, and then linearly decreased to the minimum value, forming a sawtooth or triangular waveform.

[0081] By comparing the reference sine wave with the triangular carrier, the on and off moments of the PWM signal can be determined. The specific steps include: in each control cycle, comparing the reference sine wave V(t) = Asin(ωt) and the instantaneous value of the carrier. When V(t) is greater than the carrier, a high level is output (IGBT of the inverter module is turned on); when V(t) is less than the carrier, a low level is output (IGBT is turned off). The PWM control signals are obtained based on the high and low level states generated by the comparison. These signals directly drive the IGBT devices in the inverter, thereby accurately controlling the frequency and amplitude of the inverter module output voltage and achieving precise drive control of the motor.

[0082] In one embodiment, when switching in a PWM cycle, in order to prevent the IGBTs of the upper and lower bridge arms from being turned on at the same time and causing a short circuit (i.e., a shoot-through phenomenon), a time interval, i.e., a dead time, is set between the closing of one IGBT and the opening of another IGBT to ensure that the other starts to open only after one IGBT is completely turned off. However, since the introduction of the dead time will affect the output power of the PWM signal, if the dead time is not set properly, it may lead to reduced efficiency or decreased motor performance, so the dead time needs to be adjusted or compensated. The method also includes:

[0083] Determining the dead time of the inverter module;

[0084] Determine the compensation increment corresponding to the dead time according to the total period and modulation ratio of the PWM control signal;

[0085] Acquire a new modulation ratio according to the compensation increment and the modulation ratio;

[0086] The duty cycle of the PWM control signal is set according to the new modulation ratio.

[0087] Specifically, the dead time can be determined based on the turn-on and turn-off characteristics of the IGBT used, for example, by setting the dead time through the switching time and turn-off time in the IGBT data sheet. Furthermore, by setting different dead times under different load conditions, it is ensured that the output waveform and output power of the inverter circuit are observed when no shoot-through occurs to determine the optimal dead time. Through repeated testing, training data such as IGBT-related parameters (such as turn-off time), dead time, load size, output waveform, output power, etc. are obtained, and these data are input into a preset mathematical model for training and learning to obtain the optimal dead time corresponding to different load conditions.

[0088] After the dead time is obtained, the PWM control signal is further compensated and adjusted by determining the compensation increment corresponding to the dead time to ensure the output power. In the embodiment of the present invention, the compensation increment corresponding to the dead time is determined according to the total period and modulation ratio of the PWM control signal. Specifically, the modulation ratio is determined by the target output voltage V ref Divide by the DC voltage V dc The compensation increment is the product of the ratio of the dead time to the total period of the PWM control signal and the modulation ratio. The compensation increment is the part of the modulation ratio lost due to the dead time, and it is added back to the modulation ratio to obtain the new modulation ratio m. final ,

[0089] Then, the duty cycle of the PWM waveform is changed according to the new modulation ratio. For example, the new duty cycle is obtained by adding the original PWM waveform duty cycle to the sum of the product of the new modulation ratio and the preset coefficient. The preset coefficient is a constant and can be determined according to the actual application, and is not limited here. In one embodiment, by Figure 2 The output current processing unit shown obtains the output current of the inverter module and determines whether the output power meets the requirements, and adjusts the output power to meet the application requirements by adjusting the compensation increment and / or the preset coefficient.

[0090] Through the above method, the dead time effect in the inverter system can be effectively managed and compensated, ensuring the efficiency and reliability of the system operation.

[0091] Embodiment 3

[0092] See also Figure 4 , an embodiment of the present invention provides a compressor driving device, the device comprising:

[0093] As described in the first embodiment of the low harmonic inverter circuit and the motor, the low harmonic inverter circuit is used to drive the motor, and the motor is used to drive the compressor. Exemplarily, the motor is an asynchronous induction motor.

[0094] The compressor drive device integrated with low harmonic inverter circuit is characterized by high efficiency, stability and low power consumption. It can operate stably under various working conditions and has good overall performance. It can provide more intelligent and energy-saving air-conditioning solutions under different environments and usage conditions. It is suitable for various types of air-conditioning equipment, especially railway locomotive air-conditioning equipment with high requirements on the use environment and functions.

[0095] Embodiment 4

[0096] See also Figure 5 An embodiment of the present invention provides an air-conditioning device, which includes a compressor driving device as described in Example 2, and the compressor driving device is used to circulate the refrigerant in the air-conditioning device to realize variable frequency control of the air-conditioning device, so that the air-conditioning device can adjust the flow rate of the refrigerant according to actual needs to adapt to different environmental conditions and load requirements.

[0097] The low harmonic inversion provided by the present invention is described in detail above. Those skilled in the art will further understand that the various illustrative logic blocks, modules, circuits and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented as electronic hardware, computer software or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, various illustrative components, blocks, modules, circuits and steps have been described above in general terms of functionality. Whether the functionality is implemented as hardware or software depends on the specific use and the design constraints imposed on the entire system. Those skilled in the art can implement the described functionality in different ways for each specific use. All equivalent structures or equivalent process transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly used in other related technical fields, are similarly included in the patent protection scope of the present invention. It should not be understood as a limitation of the present invention.

[0098] The above is only a specific implementation of the present invention. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process of the system, module and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be covered within the protection scope of the present invention.

Claims

1. A circuit control method based on PWM control signal, applied to low harmonic inverter circuit, characterized in that: The method comprises: Obtaining a target output voltage, a target output frequency, and a carrier frequency of the low harmonic inverter circuit; Determining the modulation ratio of the low harmonic inverter circuit according to the target output voltage, comprising: determining the modulation ratio of the low harmonic inverter circuit according to the ratio of the target output voltage to the DC side voltage; wherein the DC side voltage is the DC voltage output by the rectifier module in the low harmonic inverter circuit; Determining a carrier period according to the carrier frequency; Determining the on and off time according to the target output frequency, the modulation ratio and the carrier period; A PWM control signal is acquired according to the on and off time, and the PWM control signal is used to control the on and off of the inverter module in the low harmonic inverter circuit.

2. The circuit control method based on PWM control signal according to claim 1, characterized in that: The step of determining the on and off time according to the target output frequency, the modulation ratio and the carrier period includes: generating a reference sine wave according to the target output frequency and the modulation ratio; generating a triangular carrier according to the carrier cycle; The reference sine wave and the triangular carrier are compared to determine the turn-on and turn-off time of each IGBT in the inverter module.

3. The circuit control method based on PWM control signal according to claim 2, characterized in that: The generating a reference sine wave according to the target output frequency and the modulation ratio comprises: Calculating the angular frequency of the reference sine wave according to the target output frequency; Determining the peak amplitude of the reference sine wave according to the modulation ratio and the DC side voltage; A waveform of the reference sine wave is generated according to the angular frequency and the peak amplitude.

4. The circuit control method based on PWM control signal according to claim 2, characterized in that: The generating a triangular carrier according to the carrier period comprises: In each of the carrier cycles, the value of the carrier increases linearly until it reaches a maximum value, and then decreases linearly to a minimum value, forming a sawtooth or triangular waveform.

5. The circuit control method based on PWM control signal according to any one of claims 2 to 4, characterized in that: The step of comparing the reference sine wave with the triangular carrier wave to determine the on and off time of each IGBT in the inverter module includes: Acquire the instantaneous value of the reference sine wave and the instantaneous value of the triangular carrier at different time parameters of the control cycle; Comparing the instantaneous value of the reference sine wave with the instantaneous value of the triangular carrier; When the instantaneous value of the reference sine wave is greater than the instantaneous value of the triangular carrier, each IGBT in the inverter module is set to an on state at the time parameter setting; When the instantaneous value of the reference sine wave is less than the instantaneous value of the triangular carrier, each IGBT in the inverter module is set to an off state at the time parameter.

6. The circuit control method based on PWM control signal according to claim 1, characterized in that: The method further comprises: Determining the dead time of the inverter module; Determine a compensation increment corresponding to the dead time according to the total period of the PWM control signal and the modulation ratio; Acquire a new modulation ratio according to the compensation increment and the modulation ratio; The duty cycle of the PWM control signal is set according to the new modulation ratio.

7. The circuit control method based on PWM control signal according to claim 6, characterized in that: The step of determining the compensation increment corresponding to the dead time according to the total period of the PWM control signal and the modulation ratio comprises: Calculating the ratio of the dead time to the total period of the PWM control signal to obtain a ratio result; The ratio result and the modulation ratio are multiplied to obtain the compensation increment; wherein the compensation increment is the portion of the modulation ratio lost due to the dead time.

8. A low harmonic inverter circuit, characterized in that: According to the circuit control method based on PWM control signal as described in any one of claims 1 to 7, the low harmonic inverter circuit comprises: A filter lightning protection module, a pre-charging module, a rectifier module, a DC bus filter module and an inverter module which are electrically connected in sequence; The filtering and lightning protection module is electrically connected to the pre-charging module, and the filtering and lightning protection module includes an electrically connected capacitor, a fuse, a varistor and an inductor, which are used to suppress electromagnetic interference signals; The pre-charging module is electrically connected to the filtering and lightning protection module and the rectifying module respectively, and the pre-charging module includes an electrically connected capacitor, a resistor and a switch for current limiting when the circuit is powered on; The rectifier module is electrically connected to the pre-charging module and the DC bus filter module respectively, and the rectifier module includes an electrically connected inductor, a diode and a switch tube, and is used to rectify the AC input current into a DC current, and control the input current waveform so that the harmonic content of the input current meets the preset requirements; The DC bus filter module is electrically connected to the rectifier module and the inverter module respectively, and the DC bus filter module includes a capacitor for smoothing and filtering the rectified DC bus voltage; The inverter module is electrically connected to the DC bus filter module, and the inverter module includes an IGBT unit for converting the rectified DC current into an AC output current, wherein the output current is used to drive the motor.

9. The low harmonic inverter circuit according to claim 8, characterized in that: The low harmonic inverter circuit further includes: a first control module; The first control module includes a first DSP unit, a first EEPROM unit, an output voltage processing unit, a first driving and protection circuit unit, a current signal processing unit, and a voltage signal processing unit; Among them, the current signal processing unit is used to access the current signal detected by the ammeter set between the pre-charging module and the rectifier module, the voltage signal processing unit is used to access the voltage signal output by the filtering and lightning protection module, and the output voltage processing unit is used to adjust the voltage signal input to the inverter module.

10. The low harmonic inverter circuit according to claim 9, characterized in that: The low harmonic inverter circuit also includes a second control module; The second control module includes an ARM unit, a second DSP unit, a second EEPROM unit, a second driving and protection circuit unit, a control I / O interface unit, an output current processing unit, and a communication unit; Wherein, the output current processing unit is used to access the output current signal of the inverter module.

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