Frequency conversion circuit, inverter, compressor and air conditioning equipment for achieving harmonic suppression

Abstract

The present invention discloses a frequency conversion circuit, a frequency converter, a compressor and an air conditioning device for achieving harmonic suppression. The frequency conversion circuit for achieving harmonic suppression includes a rectifier module, a bus capacitor and an inverter module which are sequentially arranged between an AC power supply and a load. The rectifier module is turned on or off by the rectifier element inside it, thereby controlling the conduction state between the phases of the AC power supply. The frequency conversion circuit also includes: a resonance module, the input end of which is connected to the AC power supply, and the output end of which is connected to the rectifier module; the resonance module is used to change its own charge and discharge state according to the conduction state between the phases of the AC power supply, thereby triggering the rectifier element inside the rectifier module to be turned on or off. Through the present invention, it is possible to reduce the cutoff angle of the rectifier element, thereby reducing current distortion, making the input current of the frequency conversion circuit closer to a sine wave, and suppressing the harmonic content of the input current to the greatest extent, thereby achieving power factor correction.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a frequency conversion circuit, a frequency converter, a compressor and an air conditioning device for achieving harmonic suppression. Background Art

[0002] At present, high-power air conditioning equipment uses three-phase AC power supply. Traditional AC-DC-AC frequency conversion circuits generally use three-phase uncontrolled rectifier circuits. Figure 1 The waveform diagram of the output current of the existing frequency conversion circuit using an uncontrolled rectifier circuit is as follows: Figure 1 As shown in FIG. 1 , the frequency conversion circuit using an uncontrolled rectifier circuit has a cutoff angle in the rectifier element in the uncontrolled rectifier circuit, which leads to serious input current distortion, a large number of harmonics, and a reduction in the input power factor. These nonlinear harmonic sources cause serious pollution to the power system and are also an important factor endangering the safe operation of the power grid. The harmonic processing method currently used is high-frequency PWM (Pulse Width Modulation) rectifier technology. Compared with the three-phase rectifier element rectifier circuit, high-frequency PWM rectifier adds an IPM module, which is more expensive and increases the difficulty of control, and lacks competitiveness in the variable frequency air conditioning market.

[0003] With regard to the problem that the input current of the frequency conversion circuit using an uncontrolled rectifier circuit in the prior art is seriously distorted and a large number of harmonics are generated, no effective solution has been proposed so far. Summary of the invention

[0004] The embodiments of the present invention provide a frequency conversion circuit, a frequency converter, a compressor and an air conditioning device for achieving harmonic suppression, so as to solve the problem that the input current of the frequency conversion circuit using an uncontrolled rectifier circuit in the prior art is seriously distorted and generates a large number of harmonics.

[0005] In order to solve the above technical problems, the present invention provides a frequency conversion circuit for achieving harmonic suppression, comprising a rectifier module, a bus capacitor and an inverter module sequentially arranged between an AC power supply and a load, wherein the rectifier module is turned on or off by the rectifier element inside thereof, thereby controlling the conduction state between the phases of the AC power supply, and the frequency conversion circuit for achieving harmonic suppression further comprises:

[0006] A resonance module, whose input end is connected to the AC power supply and whose output end is connected to the rectifier module; the resonance module is used to change its own charge and discharge state according to the conduction state between the phases of the AC power supply, thereby triggering the rectifier element inside the rectifier module to turn on or off.

[0007] Furthermore, the AC power supply is a three-phase AC power supply; the rectifier module is specifically used to: when the value of the DC bus current is less than or equal to a preset threshold value, trigger the internal rectifier element to turn on or off according to the value of the DC bus current and the charge and discharge state of the resonance module, so as to achieve each preset time interval, triggering conduction between any two phases in the AC power supply and cutting off after a preset time; and also used to: when the value of the DC bus current is greater than a preset threshold value, trigger the internal rectifier element to turn on or off according to the charge and discharge state of the resonance module, so that each phase of the AC power supply is alternately turned on alone with any one of the other two phases or turned on simultaneously with the other two phases.

[0008] Furthermore, the resonance module comprises:

[0009] A first inductor, a second inductor and a third inductor, wherein the first inductor is connected in series to the first phase of the AC power source, the second inductor is connected in series to the second phase of the AC power source, and the third inductor is connected in series to the third phase of the AC power source;

[0010] A first capacitor, a second capacitor and a third capacitor, wherein the first capacitor is connected between the first phase of the AC power supply and the second phase of the AC power supply, the second capacitor is connected between the second phase of the AC power supply and the third phase of the AC power supply, and the third capacitor is connected between the first phase of the AC power supply and the third phase of the AC power supply.

[0011] Furthermore, the first inductor, the second inductor and the first capacitor form a charge-discharge loop for charging and discharging the first capacitor;

[0012] The second inductor, the third inductor and the second capacitor form a charge-discharge loop for charging and discharging the second capacitor;

[0013] The first inductor, the third inductor and the third capacitor form a charge-discharge loop for charging and discharging the third capacitor.

[0014] Further, the rectifier module is an uncontrolled rectifier module, which includes three rectifier bridges arranged in parallel, namely, a first rectifier bridge, a second rectifier bridge and a third rectifier bridge;

[0015] The upper bridge arm of each rectifier bridge forms different conduction loops with the lower bridge arms of the other two rectifier bridges, and the conduction loops are used to control conduction between any two phases of the AC power supply.

[0016] Further, the first rectifier bridge has an upper bridge arm composed of a first rectifier element and a lower bridge arm composed of a fourth rectifier element, and the first phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge;

[0017] The second rectifier bridge has an upper bridge arm composed of a third rectifier element and a lower bridge arm composed of a sixth rectifier element, and the second phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge;

[0018] The third rectifier bridge has an upper bridge arm composed of the fifth rectifier element and a lower bridge arm composed of the second rectifier element. The third phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the third rectifier bridge.

[0019] Furthermore, the rectifier module is an uncontrolled rectifier module.

[0020] Furthermore, the first capacitor, the second capacitor and the third capacitor are AC film capacitors.

[0021] The present invention also provides a frequency converter, comprising the frequency conversion circuit for achieving harmonic suppression.

[0022] The present invention also provides a compressor, comprising a load, wherein the load is a motor, and also comprising the above-mentioned frequency converter.

[0023] The present invention also provides an air-conditioning device, comprising the above compressor.

[0024] By applying the technical solution of the present invention, the resonance module changes its own charging and discharging state according to the conduction state between the phases of the AC power supply, thereby triggering the rectification element inside the rectification module to be turned on or off, thereby reducing the cut-off angle of the rectification element, thereby reducing current distortion, making the input current of the frequency conversion circuit closer to a sine wave, and suppressing the harmonic content of the input current to the greatest extent, thereby realizing the power factor correction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The waveform diagram of the output current of the existing frequency conversion circuit using an uncontrolled rectifier circuit;

[0026] Figure 2 It is a circuit topology diagram of a traditional AC-DC-AC frequency conversion circuit;

[0027] Figure 3 A structural diagram of a frequency conversion circuit for achieving harmonic suppression according to an embodiment of the present invention;

[0028] Figure 4 A structural diagram of a frequency conversion circuit for achieving harmonic suppression according to another embodiment of the present invention;

[0029] Figure 5 is a waveform diagram of the input current of the AC power supply according to an embodiment of the present invention;

[0030] Figure 6The figure is a comparison diagram between an actual waveform input to a frequency conversion circuit for achieving harmonic suppression according to an embodiment of the present invention and a sine wave. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0033] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0034] It should be understood that although the terms first, second, third, etc. may be used to describe ... in the embodiments of the present invention, these ... should not be limited to these terms. These terms are only used to distinguish .... For example, without departing from the scope of the embodiments of the present invention, the first ... may also be referred to as the second ..., and similarly, the second ... may also be referred to as the first ....

[0035] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0036] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0037] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] Example 1

[0039] As mentioned above Figure 1 As shown in the figure, the frequency conversion circuit using an uncontrolled rectifier circuit has a cutoff angle in the rectifier element in the uncontrolled rectifier circuit, which leads to serious input current distortion and the generation of a large number of harmonics, which reduces the input power factor. These nonlinear harmonic sources cause serious pollution to the power system and are also an important factor endangering the safe operation of the power grid. Figure 2 This is the circuit topology diagram of the traditional AC-DC-AC frequency conversion circuit, where U, V, and W are three-phase AC inputs, and also include a high-frequency PWM rectifier module and an inverter module, a bus capacitor C, and an external compressor load. Compared with the traditional rectifier inverter topology, a high-frequency PWM rectifier module is added, which requires a peripheral circuit to control the opening and closing of the IGBT. The added circuits and modules not only increase the cost of the controller and increase the difficulty of software control, but also affect the reliability of the controller. Therefore, it is obvious that the method of eliminating harmonics by setting a high-frequency PWM rectifier module has many disadvantages.

[0040] This embodiment provides a frequency conversion circuit for achieving harmonic suppression. Figure 3 FIG. 4 is a structural diagram of a frequency conversion circuit for achieving harmonic suppression according to an embodiment of the present invention. Figure 3 As shown, the frequency conversion circuit for achieving harmonic suppression includes a rectifier module 2, a bus capacitor C and an inverter module 3 which are sequentially arranged between the AC power supply and the load. The rectifier module 2 is turned on or off by the internal rectifier element thereof, thereby controlling the conduction state between the phases of the AC power supply. The frequency conversion circuit for achieving harmonic suppression also includes:

[0041] The resonance module 1 has an input end connected to an AC power source and an output end connected to a rectifier module 2; the resonance module 1 is used to change its own charge and discharge state according to the conduction state between each phase of the AC power source, thereby triggering the rectifier element inside the rectifier module 2 to turn on or off.

[0042] The frequency conversion circuit for achieving harmonic suppression in this embodiment changes its own charge and discharge state according to the conduction state between the phases of the AC power supply through the resonance module 1, thereby triggering the rectification element inside the rectification module 2 to be turned on or off, which can reduce the cut-off angle of the rectification element, thereby reducing current distortion, making the input current of the frequency conversion circuit closer to a sine wave, and can suppress the harmonic content of the input current to the greatest extent, thereby achieving power factor correction.

[0043] Example 2

[0044] The present embodiment provides another frequency conversion circuit for achieving harmonic suppression. In the present embodiment, the above-mentioned AC power supply is a three-phase AC power supply, and the rectifier module 2 is specifically used for: when the value of the DC bus current is less than or equal to a preset threshold value, triggering the internal rectifier element to be turned on or off according to the value of the DC bus current and the charge and discharge state of the resonance module 1, so as to achieve each preset time interval, triggering conduction between any two phases in the AC power supply and cutting off after the preset time; when the value of the DC bus current is greater than the preset threshold value, triggering the internal rectifier element to be turned on or off according to the value of the DC bus current and the charge and discharge state of the resonance module 1, so that each phase of the AC power supply is alternately turned on alone with any of the other two phases or turned on simultaneously with the other two phases.

[0045] Figure 4 FIG. 1 is a structural diagram of a frequency conversion circuit for achieving harmonic suppression according to another embodiment of the present invention. In order to reduce the cutoff angle of the rectifying element in the rectifying module, as shown in FIG. Figure 4 As shown, the above-mentioned resonance module 1 includes:

[0046] A first inductor Lu, a second inductor Lv and a third inductor Lw, wherein the first inductor Lu is connected in series to the first phase U of the AC power supply, the second inductor Lv is connected in series to the second phase of the AC power supply, and the third inductor Lw is connected in series to the third phase of the AC power supply; a first capacitor C1, a second capacitor C2 and a third capacitor C3, wherein the first capacitor C1 is connected between the first phase U of the AC power supply and the second phase of the AC power supply, the second capacitor C2 is connected between the second phase V of the AC power supply and the third phase W of the AC power supply, and the third capacitor C3 is connected between the first phase U of the AC power supply and the third phase W of the AC power supply.

[0047] The first inductor Lu, the second inductor Lv and the first capacitor C1 constitute a charge-discharge circuit for charging and discharging the first capacitor C1; the second inductor Lv, the third inductor Lw and the second capacitor C2 constitute a charge-discharge circuit for charging and discharging the second capacitor C2; the first inductor Lu, the third inductor Lw and the third capacitor C3 constitute a charge-discharge circuit for charging and discharging the third capacitor C3.

[0048] In this embodiment, the first capacitor C1 , the second capacitor C2 and the third capacitor C3 are all AC film capacitors.

[0049] In order to save device costs, the rectifier module is an uncontrolled rectifier module, which includes three rectifier bridges arranged in parallel, namely a first rectifier bridge, a second rectifier bridge and a third rectifier bridge; wherein the upper bridge arm of each rectifier bridge respectively forms a different conduction loop with the lower bridge arms of the other two rectifier bridges, and the conduction loop is used to control the conduction between any two phases of the AC power supply.

[0050] Specifically, Figure 4 As shown, the first rectifier bridge, its upper bridge arm is composed of the first rectifier element VD1, its lower bridge arm is composed of the fourth rectifier element VD4, and the first phase U of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge; the second rectifier bridge, its upper bridge arm is composed of the third rectifier element VD3, its lower bridge arm is composed of the sixth rectifier element VD6, and the second phase V of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge; the third rectifier bridge, its upper bridge arm is composed of the fifth rectifier element VD5, its lower bridge arm is composed of the second rectifier element VD2, and the third phase W of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the third rectifier bridge. The above-mentioned rectifier elements can be diodes.

[0051] When the value of the DC bus current is less than or equal to the preset threshold value, it indicates that the load is running under low load. The rectifier module triggers the internal rectifier element to turn on or off according to the value of the DC bus current and the charge and discharge state of the resonance module 1, so as to achieve a preset time period at each interval, triggering any two phases in the AC power supply to turn on and turn off after a preset time period, including: at the initial moment, there is current passing between the third phase W and the first phase U of the AC power supply, so that the voltage across the third capacitor C3 is equal to the load voltage, triggering the fifth rectifier element VD5 and the fourth rectifier element VD4 to turn on; after the preset time period, the DC bus current changes to zero, triggering the fifth rectifier element VD5 and the fourth rectifier element VD4 to turn off, and at the same time, the first inductor Lu and the second inductor Lv charge the first capacitor C1 forward, and the second inductor Lv and the third inductor Lw charge the second capacitor C2 reversely;

[0052] After a preset time interval, the voltage across the second capacitor C2 drops to the negative load voltage, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to turn on; after a preset time interval, the DC bus current changes to zero, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to turn off, the first capacitor C1 keeps positive charging, and the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor Lw;

[0053] After a preset time interval, the voltage across the first capacitor C1 rises to the load voltage, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to turn on. After a preset time interval, the DC bus current changes to zero, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to turn off. At the same time, the second inductor Lv and the third inductor Lw begin to positively charge the second capacitor C2, and the third capacitor C3 discharges.

[0054] After a preset time interval, the voltage across the third capacitor C3 drops to the negative load voltage, triggering the first rectifier element VD1 and the second rectifier element VD2 to turn on. After a preset time interval, the DC bus current changes to zero, triggering the first rectifier element VD1 and the second rectifier element VD2 to turn off. At the same time, the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv, and the second capacitor C2 continues to charge positively.

[0055] After a preset time interval, the voltage across the second capacitor C2 rises to the load voltage, triggering the third rectifier element VD3 and the second rectifier element VD2 to turn on. After a preset time interval, the DC bus current changes to zero, triggering the third rectifier element VD3 and the second rectifier element VD2 to turn off. At the same time, the first capacitor C1 continues to discharge, and the first inductor Lu and the third inductor Lw begin to charge the third capacitor C3.

[0056] After a preset time interval, the voltage across the first capacitor C1 drops to the negative load voltage, triggering the third rectifier element VD3 and the fourth rectifier element VD4 to turn on. After a preset time interval, the DC bus current changes to zero, triggering the third rectifier element VD3 and the fourth rectifier element VD4 to turn off. At the same time, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor Lw, and the third capacitor C3 continues to charge.

[0057] After a preset time interval, the voltage across the third capacitor C3 rises to the load voltage, triggering the fifth rectifier element VD5 and the fourth rectifier element VD4 to turn on, and starting the next AC power cycle; wherein the initial moment is the moment when the phase angles of the three phases of the AC power are all zero, and the preset time is 1 / 12 of the cycle. The load in this embodiment can specifically be the motor of the compressor.

[0058] In specific implementation, technical personnel in this field can design the inductance values ​​of the first inductor Lu, the second inductor Lv, and the third inductor Lw and the capacitance values ​​of the first capacitor C1, the second capacitor C2, and the third capacitor C3 according to the actual three-phase current size and the expected charging time to achieve the charging and discharging state at the above moment.

[0059] As mentioned above Figure 4As shown in , the first inductor Lu, the second inductor Lv, and the third inductor Lw are respectively connected in series at the input ends of the first phase U, the second phase V, and the third phase W of the AC power supply, the first phase U outputs current iu, the second phase V outputs current iv, and the third phase W outputs current iw. The first capacitor C1, the second capacitor C2, and the third capacitor C3 can be AC ​​film capacitors, which are respectively connected in parallel between the first phase U and the second phase V, between the second phase V and the third phase W, and between the first phase U and the third phase W of the AC power supply. The above-mentioned devices constitute a resonant module 1 to achieve power factor correction (i.e., passive PFC), and the use of uncontrolled rectifier elements instead of high-frequency PWM rectifier modules reduces the cost of the controller and reduces the difficulty of software control. In this process, the presence of parallel capacitors can effectively raise the DC bus voltage and reduce the impact of the compressor back electromotive force on the software control due to the bus voltage being too low.

[0060] The operations triggered at different times under light load conditions are shown in Table 1 below:

[0061] Table 1 Operations triggered at different times under low load conditions

[0062]

[0063]

[0064] Figure 5 The waveform diagram of the input current of the AC power supply according to the embodiment of the present invention is shown below in combination with Figure 5 As shown in Table 1 above, the operations triggered at different times are introduced:

[0065] At time t0, current flows between the third phase W and the first phase U of the AC power supply, making the voltage across the third capacitor C3 equal to the load voltage, triggering the fifth rectifying element VD5 and the fourth rectifying element VD4 to turn on; at time t1, the DC bus current i0=iw+iv / 2 changes to zero, triggering the fifth rectifying element VD5 and the fourth rectifying element VD4 to turn off, and at the same time, the first capacitor C1 starts to charge forward, and the second inductor Lv and the third inductor Lw charge the second capacitor C2 in reverse;

[0066] At time t2, the voltage across the second capacitor C2 drops to the negative load voltage, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to turn on; at time t3, the DC bus current iw+iu / 2 changes to zero, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to turn off, the first capacitor C1 keeps positive charging, and the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor Lw;

[0067] At time t4, the voltage across the first capacitor C1 rises to the load voltage, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to turn on. At time t5, the DC bus current i0=iu+iw / 2 changes to zero, triggering the first rectifying element VD1 and the sixth rectifying element VD6 to turn off. At the same time, the second inductor Lv and the third inductor Lw begin to positively charge the second capacitor C2, and the third capacitor C3 discharges.

[0068] At time t6, the voltage across the third capacitor C3 drops to the negative load voltage, triggering the first rectifier element VD1 and the second rectifier element VD2 to turn on. At time t7, the DC bus current i0=iu+iv / 2 changes to zero, triggering the first rectifier element VD1 and the second rectifier element VD2 to turn off. At the same time, the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv, and the second capacitor C2 continues to charge positively.

[0069] At time t8, the voltage across the second capacitor C2 rises to the load voltage, triggering the third rectifier element VD3 and the second rectifier element VD2 to turn on. At time t9, the DC bus current i0=iv+iu / 2 changes to zero, triggering the third rectifier element VD3 and the second rectifier element VD2 to turn off. At the same time, the first capacitor C1 continues to discharge, and the first inductor Lu and the third inductor begin to charge the third capacitor C3.

[0070] At time t10, the voltage across the first capacitor C1 drops to the negative load voltage, triggering the third rectifier element VD3 and the fourth rectifier element VD4 to turn on. At time t11, the DC bus current i0=iv+iw / 2 changes to zero, triggering the third rectifier element VD3 and the fourth rectifier element VD4 to turn off. At the same time, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor, and the third capacitor C3 continues to charge.

[0071] At time t12, the voltage across the third capacitor C3 rises to the load voltage, triggering the fifth rectifying element VD5 and the fourth rectifying element VD4 to turn on, and starting the next AC power cycle; wherein, t0 is the moment when the phase angles of the three phases of the AC power are all zero, and the interval between any two moments is 1 / 12 of the cycle. Figure 6 FIG. 4 is a comparison diagram of an actual waveform input to a frequency conversion circuit for achieving harmonic suppression according to an embodiment of the present invention and a sine wave, as shown in FIG. Figure 6 As shown, after adopting the frequency conversion circuit for achieving harmonic suppression according to the embodiment of the present invention, the actual waveform input by the frequency conversion circuit reduces the cutoff angle of the rectifier element, is closer to a sine wave, and effectively suppresses harmonics.

[0072] Table 2 below shows the operations triggered at different times under heavy load conditions:

[0073] Table 2 Operations triggered at different times under heavy load

[0074]

[0075]

[0076] In conjunction with Table 2 above, the following describes how, under heavy load conditions, the present invention triggers the internal rectifying element to be turned on or off according to the charge and discharge state of the resonance module 1, so that each phase of the AC power source is alternately turned on alone with any of the other two phases or turned on simultaneously with the other two phases:

[0077] At time t0, the voltage across the second capacitor C2 is a negative load voltage, triggering the fifth rectifying element VD5 and the sixth rectifying element VD6 to turn on; so that the third phase W and the second phase V of the AC power supply are turned on separately, and at the same time, the first inductor Lu and the second inductor Lv charge the first capacitor C1 in a positive direction. At time t1, the voltage across the first capacitor C1 rises to the load voltage, triggering the first rectifying element VD1 to turn on, so that the first phase U and the third phase W and the second phase V of the AC power supply are turned on at the same time, and at the same time, the second capacitor C2 starts to charge forward;

[0078] At time t2, the voltage across the second capacitor C2 rises to a value greater than the negative load voltage, triggering the fifth rectifying element VD5 to be turned off, so that the first phase U and the second phase V of the AC power supply are turned on separately, and the third capacitor C3 starts to charge; at time t3, the third capacitor C3 is charged to the load voltage, triggering the second rectifying element VD2 to be turned on, so that the first phase U and the second phase V and the third phase W of the AC power supply are turned on simultaneously, and the first capacitor C1 starts to discharge to the first inductor Lu and the second inductor Lv;

[0079] At time t4, the voltage of the first capacitor C1 drops to less than the load voltage, triggering the sixth rectifier element VD6 to be turned off, so that the first phase U and the third phase W of the AC power supply are turned on separately, and at the same time, the second capacitor C2 continues to be positively charged; at time t5, the voltage across the second capacitor C2 rises to the load voltage, triggering the third rectifier element VD3 to be turned on, so that the second phase V of the AC power supply is turned on simultaneously with the first phase U and the third phase W, and at the same time, the third capacitor C3 starts to discharge to the first inductor Lu and the third inductor;

[0080] At time t6, the voltage across the third capacitor C3 is lower than the load voltage, triggering the first rectifying element VD1 to be turned off, so that the second phase V and the third phase W of the AC power supply are turned on separately, and the first capacitor C1 is reversely charged. At time t7, the voltage across the first capacitor C1 drops to the negative load voltage, triggering the fourth rectifying element VD4 to be turned on, so that the second phase V and the first phase U and the third phase W of the AC power supply are turned on at the same time, and at the same time, the second capacitor C2 starts to discharge to the second inductor Lv and the third inductor;

[0081] At time t8, the voltage across the second capacitor C2 drops to less than the load voltage, triggering the second rectifying element VD2 to be turned off, so that the second phase V and the first phase U of the AC power supply are turned on separately, and the third capacitor C3 is reversely charged; at time t9, the voltage across the third capacitor C3 drops to the negative load voltage, triggering the fifth rectifying element VD5 to be turned on, so that the third phase W and the first phase U and the second phase V of the AC power supply are turned on at the same time, and the first capacitor C1 is forwardly charged;

[0082] At time t10, the voltage across the first capacitor C1 rises to a value greater than the negative load voltage, triggering the third rectifying element VD3 to be turned off, so that the third phase W and the first phase U of the AC power supply are turned on separately, and at the same time, the second inductor Lv and the third inductor reversely charge the second capacitor C2; at time t11, the voltage across the second capacitor C2 drops to the negative load voltage, triggering the sixth rectifying element VD6 to be turned on, so that the third phase W and the second phase V and the first phase U of the AC power supply are turned on at the same time, and at the same time, the first inductor Lu and the third inductor start to positively charge the third capacitor C3;

[0083] At time t12, the voltage across the third capacitor C3 rises to a value greater than the negative load voltage, triggering the fourth rectifier element VD4 to be turned off, so that the third phase W and the second phase V of the AC power supply are turned on separately, and the next AC power supply cycle begins.

[0084] Example 3

[0085] This embodiment provides a frequency converter, including the frequency conversion circuit for achieving harmonic suppression in the above embodiment, which is used to reduce the cutoff angle of the rectifier element in the rectifier module, thereby making the input waveform of the frequency conversion circuit closer and effectively suppressing harmonics.

[0086] Example 4

[0087] This embodiment provides a compressor, including a load, which is a motor, and also includes the inverter in the above embodiment, which is used to suppress harmonics and improve the quality of electric energy input to the compressor.

[0088] Example 5

[0089] This embodiment provides an air-conditioning device, including the compressor in the above embodiment, which is used to improve the quality of electric energy input to the entire air-conditioning device to improve the reliability of the device.

[0090] The circuit embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency conversion circuit for achieving harmonic suppression, comprising a rectifier module, a bus capacitor and an inverter module arranged in sequence between an AC power supply and a load, characterized in that: The rectifier module controls the conduction state between the phases of the AC power supply by turning on or off the internal rectifier element thereof; when the value of the DC bus current is less than or equal to a preset threshold value, the rectifier module triggers the internal rectifier element thereof to turn on or off according to the value of the DC bus current and the charge and discharge state of the resonance module, so as to achieve conduction between any two phases of the AC power supply at each preset interval and to be turned off after the preset duration; and is also used for: when the value of the DC bus current is greater than a preset threshold value, triggering the internal rectifier element thereof to turn on or off according to the charge and discharge state of the resonance module, so that each phase of the AC power supply is alternately turned on alone with any one of the other two phases or turned on simultaneously with the other two phases; The frequency conversion circuit for achieving harmonic suppression also includes: a resonance module, whose input end is connected to the AC power supply, and whose output end is connected to the rectifier module; the resonance module is used to change its own charging and discharging state according to the conduction state between the phases of the AC power supply, thereby triggering the rectifier element inside the rectifier module to be turned on or off; the resonance module includes: a first inductor, a second inductor and a third inductor, the first inductor is connected in series to the first phase of the AC power supply, the second inductor is connected in series to the second phase of the AC power supply, and the third inductor is connected in series to the third phase of the AC power supply; a first capacitor, a second capacitor and a third capacitor, the first capacitor is connected between the first phase of the AC power supply and the second phase of the AC power supply, the second capacitor is connected between the second phase of the AC power supply and the third phase of the AC power supply, and the third capacitor is connected between the first phase of the AC power supply and the third phase of the AC power supply.

2. The frequency conversion circuit for achieving harmonic suppression according to claim 1, characterized in that: The first inductor, the second inductor and the first capacitor form a charge-discharge loop for charging and discharging the first capacitor; The second inductor, the third inductor and the second capacitor form a charge-discharge loop for charging and discharging the second capacitor; The first inductor, the third inductor and the third capacitor form a charge-discharge loop for charging and discharging the third capacitor.

3. The frequency conversion circuit for achieving harmonic suppression according to claim 1, characterized in that: The rectifier module comprises three rectifier bridges arranged in parallel, namely, a first rectifier bridge, a second rectifier bridge and a third rectifier bridge; The upper bridge arm of each rectifier bridge forms different conduction loops with the lower bridge arms of the other two rectifier bridges, and the conduction loops are used to control conduction between any two phases of the AC power supply.

4. The frequency conversion circuit for achieving harmonic suppression according to claim 3, characterized in that: The first rectifier bridge has an upper bridge arm composed of a first rectifier element and a lower bridge arm composed of a fourth rectifier element, and the first phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the first rectifier bridge; The second rectifier bridge has an upper bridge arm composed of a third rectifier element and a lower bridge arm composed of a sixth rectifier element, and the second phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the second rectifier bridge; The third rectifier bridge has an upper bridge arm composed of the fifth rectifier element and a lower bridge arm composed of the second rectifier element. The third phase of the AC power supply is connected between the upper bridge arm and the lower bridge arm of the third rectifier bridge.

5. The frequency conversion circuit for achieving harmonic suppression according to claim 4, characterized in that: The rectifier module is an uncontrolled rectifier module.

6. The frequency conversion circuit for achieving harmonic suppression according to claim 1, characterized in that: The first capacitor, the second capacitor and the third capacitor are AC film capacitors.

7. A frequency converter, characterized in that: A frequency conversion circuit for achieving harmonic suppression comprising any one of claims 1 to 6.

8. A compressor, comprising a load, wherein the load is a motor, characterized in that: Also includes the frequency converter as claimed in claim 7.

9. An air conditioning device, characterized in that: Comprising the compressor as claimed in claim 8.

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