Resonant filter circuit and device and frequency conversion device

Abstract

The utility model discloses a resonant filter circuit, a device and a frequency conversion device, and relates to the field of circuits, when a frequency conversion system controls a compressor to start, a controllable switch is switched on, an LC filter module is connected to a circuit between an AC power supply and the frequency conversion system, harmonic waves generated in the circuit are filtered, and the frequency conversion system is switched on. The harmonic current content in the air conditioner subsystem is reduced; and when the frequency conversion system does not control the compressor to start, the controllable switch is kept switched off, and the LC filter module is not put into use, so that the consumption of reactive power by the capacitor is avoided. Whether the LC filter module is put into use or not is controlled by switching on and switching off the controllable switch, harmonic suppression is carried out on the working frequency conversion system, meanwhile, voltage loss and electric energy loss caused by the fact that the LC filter module is connected into the circuit when the frequency conversion system does not work are avoided, and reactive power consumption of the whole circuit and the frequency conversion system is reduced.

Description

Technical Field

[0001] The utility model relates to the field of circuits, in particular to a resonant filter circuit, a device and a frequency conversion device. Background Art

[0002] Rail transit train systems are energy-intensive due to their high capacity, extensive equipment, and long operating hours. Reducing the energy consumption of the entire train system is a key development direction. The air conditioning subsystem consumes a relatively large portion of the energy within the entire system. Therefore, reducing the reactive power of the air conditioning can effectively reduce the energy consumption of the entire train system.

[0003] At present, the working process of the compressor of the air-conditioning subsystem is realized by the AC-DC-AC frequency conversion system. The frequency conversion system can dynamically adjust the voltage and frequency of the compressor to achieve the purpose of precise temperature control of the air-conditioning subsystem and reduce energy consumption.

[0004] In the process of realizing the present invention, the inventors discovered that the prior art has at least the following problems:

[0005] When the AC-DC-AC frequency conversion system is in operation, due to the presence of the rectifier bridge and IGBT (Insulated Gate Bipolar Transistor), a large number of odd-order current harmonics such as 5th, 7th, and 9th will be generated. A large amount of current harmonic distortion can affect the normal operation of other equipment in the train system, cause the busbar capacitor life of the train auxiliary inverter system to decrease, and even pose a threat to the safe operation of the train.

[0006] Therefore, how to suppress the harmonics in the frequency conversion system has become a technical problem that needs to be solved urgently. Utility Model Content

[0007] The purpose of the utility model is to provide a resonant filter circuit, device and frequency conversion device, which utilize the on and off of a controllable switch to control whether the LC filter module is put into use, thereby suppressing harmonics of the working frequency conversion system and avoiding voltage loss and power loss caused by the LC filter module being connected to the circuit when the frequency conversion system is not working, thereby reducing the reactive power consumption of the entire circuit and the frequency conversion system.

[0008] In order to solve the above technical problems, the utility model provides a resonant filter circuit, comprising:

[0009] a controllable switch, a first end of which is connected to the output end of the AC power supply and the input end of the frequency conversion system respectively, and is configured to be turned on when the frequency conversion system controls the compressor to start, and turned off when the frequency conversion system does not control the compressor to start;

[0010] The LC filter module connected to the second end of the controllable switch is used to maintain connection with the input end of the frequency conversion system to filter out harmonics when the controllable switch is turned on.

[0011] Optionally, the controllable switch includes a contact and a coil, wherein a first end of the contact is connected to the input end of the AC power supply and the frequency conversion system respectively, and a second end is connected to the input end of the LC filter module; a first end of the coil is connected to the output end of the controller, and a second end is grounded;

[0012] The coil is used to be energized based on the control of the controller when the variable frequency system controls the compressor to start, so as to control the contacts to be turned on; and to lose power based on the control of the controller when the variable frequency system does not control the compressor to start, so as to control the contacts to be turned off.

[0013] Optionally, also include:

[0014] The temperature detection module has an input end connected to the air conditioning subsystem and an output end connected to the input end of the controller, and is used to detect temperature data of the air conditioning subsystem so that the controller can determine whether to start the compressor based on the temperature data.

[0015] Optionally, the AC power supply is a three-phase power supply, and the controllable switch includes:

[0016] a first controllable sub-switch, wherein a first end is connected to the first phase line output end of the AC power supply and the first input end of the frequency conversion system respectively, and a second end is connected to the input end of the LC filter module;

[0017] a second controllable sub-switch, wherein a first end is connected to the second phase line output end of the AC power supply and the second input end of the frequency conversion system respectively, and a second end is connected to the input end of the LC filter module;

[0018] The second controllable sub-switch has a first end connected to the third phase line output end of the AC power supply and the third input end of the frequency conversion system respectively, and a second end connected to the input end of the LC filter module.

[0019] Optionally, the LC filter module includes:

[0020] a first filter reactor, a first end of which is connected to the second end of the first controllable sub-switch;

[0021] a second filter reactor, a first end of which is connected to the second end of the second controllable sub-switch;

[0022] a third filter reactor, a first end of which is connected to the second end of the third controllable sub-switch;

[0023] a first filter capacitor;

[0024] a second filter capacitor, a first end of which is respectively connected to the second end of the second filter reactor and the first end of the first filter capacitor;

[0025] The third filter capacitor has a first end connected to the second end of the third filter inductor and the second end of the second filter capacitor respectively, and a second end connected to the second end of the first filter inductor and the second end of the first filter capacitor respectively.

[0026] Optionally, also include:

[0027] An incoming line reactance module connected in series between the output end of the AC power supply and the first end of the controllable switch and / or an outgoing line reactance module connected in series between the first end of the controllable switch and the input end of the frequency conversion system.

[0028] Optionally, the incoming line reactance module includes:

[0029] a first incoming line reactor, a first end of which is connected to the first phase line output end of the AC power supply, and a second end of which is respectively connected to the first end of the first controllable sub-switch and the first input end of the frequency conversion system;

[0030] a second line reactor, a first end of which is connected to the second phase line output end of the AC power supply, and a second end of which is respectively connected to the first end of the second controllable sub-switch and the second input end of the frequency conversion system;

[0031] The third incoming line reactor has a first end connected to the third phase line output end of the AC power supply, and a second end connected to the first end of the third controllable sub-switch and the third input end of the frequency conversion system respectively.

[0032] Optionally, the outgoing line reactance module includes:

[0033] a first outgoing line reactor, a first end of which is respectively connected to the second end of the first incoming line reactor and the first end of the first controllable sub-switch, and a second end of which is connected to the first input end of the frequency conversion system;

[0034] a second outgoing line reactor, a first end of which is respectively connected to the second end of the second incoming line reactor and the first end of the second controllable sub-switch, and a second end of which is connected to the second input end of the frequency conversion system;

[0035] The third outgoing line reactor has a first end connected to the second end of the third incoming line reactor and the first end of the third controllable sub-switch respectively, and a second end connected to the third input end of the frequency conversion system.

[0036] To solve the above technical problems, the present invention further provides a resonant filter device, comprising a controller and the resonant filter circuit as described above, wherein the output end of the controller is connected to the control end of a controllable switch in the resonant filter circuit.

[0037] In order to solve the above technical problems, the present invention also provides a frequency conversion device, including a rectifier circuit, an inverter circuit and the resonant filter device as described above, the output end of the resonant filter device is connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the compressor.

[0038] Compared with the existing technology, the technical solution provided by the utility model has at least the following beneficial effects:

[0039] The utility model provides a resonant filter circuit, comprising a controllable switch and an LC filter module connected to the controllable switch. When the frequency conversion system controls the compressor to start, the controllable switch is also turned on, connecting the LC filter module to the circuit between the AC power supply and the frequency conversion system, filtering harmonics generated in the circuit and reducing the harmonic current content in the air conditioning subsystem. When the frequency conversion system does not control the compressor to start, the controllable switch remains off, and the LC filter module is not put into use, thereby avoiding the consumption of reactive power by the capacitor therein. The turning on and off of the controllable switch is used to control whether the LC filter module is put into use. While suppressing harmonics in the operating frequency conversion system, it also avoids voltage loss and power loss caused by the LC filter module being connected to the circuit when the frequency conversion system is not operating, thereby reducing the reactive power consumption of the entire circuit and the frequency conversion system.

[0040] The utility model also provides a resonant filter device and a frequency conversion device, which have the same beneficial effects as the above-mentioned resonant filter circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the prior art and the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 A schematic structural diagram of a resonant filter circuit provided by the utility model;

[0043] Figure 2 A schematic structural diagram of a frequency conversion device provided by the utility model;

[0044] Figure 3This is a structural diagram of a control system of a frequency conversion device provided by the utility model. DETAILED DESCRIPTION

[0045] The core of the utility model is to provide a resonant filter circuit, device and frequency conversion device, which uses the on and off of a controllable switch to control whether the LC filter module is put into use. While suppressing the harmonics of the working frequency conversion system, it avoids the voltage loss and power loss caused by the LC filter module being connected to the circuit when the frequency conversion system is not working, thereby reducing the reactive power consumption of the entire circuit and the frequency conversion system.

[0046] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0047] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a resonant filter circuit provided by the utility model; please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of a frequency conversion device provided by the utility model; please refer to Figure 3 , Figure 3 This is a schematic diagram of the control system of a frequency conversion device provided by the present invention. To solve the above technical problems, the present invention provides a resonant filter circuit, including:

[0048] A controllable switch 1, wherein a first end is connected to the output end of the AC power supply 2 and the input end of the frequency conversion system 3, respectively, and is configured to be turned on when the frequency conversion system 3 controls the compressor to start, and turned off when the frequency conversion system 3 does not control the compressor to start;

[0049] The LC filter module 4 connected to the second end of the controllable switch 1 is used to maintain connection with the input end of the frequency conversion system 3 to filter out harmonics when the controllable switch 1 is turned on.

[0050] It can be understood that by setting up the LC filter module 4, some harmonics of specific frequencies generated by the frequency conversion system 3 during operation can be effectively filtered out, thereby achieving the effect of suppressing the harmonics generated by the frequency conversion system 3; at the same time, considering that the frequency conversion system 3 will only generate harmonic currents during operation, that is, when the compressor is started and operated, the present application also adds an LC filter module 4 connected in series with the controllable switch 1. The controllable switch 1 is switched to the on state when the frequency conversion system 3 is working, that is, when the compressor is started. At this time, the LC filter module 4 is connected to the frequency conversion system 3 through the turned-on controllable switch 1. The input end of the inverter system 3 remains connected, and the LC filter module 4 is connected to the working circuit of the frequency conversion system 3 to play a filtering role. The harmonic current generated during the operation of the frequency conversion system 3 will be absorbed by the LC filter module 4 to avoid its influence on the AC power supply 2 or other equipment in the train system; the controllable switch 1 remains turned off when the frequency conversion system 3 is not working, that is, when the compressor is not controlled to start, so that the LC filter module 4 is cut out of the working circuit of the frequency conversion system 3, thereby avoiding the connection between the capacitor in the LC filter module 4 and the AC circuit, and preventing the abnormal consumption of reactive power in the circuit due to the continuous charging and discharging of the capacitor.

[0051] It should be noted that the principle of the LC filter module 4 is based on the characteristics that capacitors pass high frequencies and block low frequencies, while inductors pass low frequencies and block high frequencies. And the capacitive reactance formula: In the LC filter module 4, resonance occurs when the inductive reactance and capacitive reactance are equal at a specific frequency. During parallel resonance, the impedance present in the circuit is maximum, and the voltage in the circuit reaches its maximum value. Because the impedance is maximum, the voltage decreases significantly for signals that deviate from the resonant frequency due to the reduced impedance, thereby achieving a filtering effect. During series resonance, the impedance present in the circuit is minimum, and the current in the circuit reaches its maximum value. Because the impedance is minimum, the current decreases significantly for signals that deviate from the resonant frequency due to the increased impedance, thereby achieving a filtering effect.

[0052] It is easy to understand that the LC filter module 4 specifically includes capacitors and reactors. The specific type, connection method, and number of capacitors and reactors can be set and adjusted according to the actual application. The capacitors and reactors can be connected in parallel and / or in series, and the filtering characteristics under different connection methods are used to effectively eliminate harmonics of specific frequencies. The capacitance value of the capacitors and the inductance value of the reactors also need to be adjusted according to the actual application. By adjusting the parameter values ​​of the reactors and capacitors, the LC filter module 4 can filter and suppress specific harmonic frequencies.

[0053] It should be noted that the present application does not make any special restrictions on the specific type and implementation of the controllable switch 1, and it can be implemented by switching devices such as contactors and power electronic switches. The present application adds a controllable switch 1 at the front end of the LC filter module 4 in the resonant filter circuit. When the frequency conversion system 3 is on standby, it can effectively disconnect the connection between the filter capacitor and the main circuit, thereby achieving the purpose of reducing reactive power consumption, thereby ensuring the power supply capacity of the AC power supply 2 as the power supply equipment, reducing line voltage loss and power loss, avoiding low power factor operation and voltage drop, and ensuring that the capacity of the electrical equipment can be fully utilized. The present application does not make any special restrictions on the specific type and implementation of the AC power supply 2, and it can be directly connected to the power grid or implemented by other means.

[0054] It is understood that the resonant filter circuit provided in this application can be applied to the field of rail transit air conditioning. Installed at the front end of the frequency conversion system 3 in the air conditioning subsystem of a train system, it eliminates and suppresses harmonics generated during the operation of the frequency conversion system 3, thus achieving a functional design that uses resonant filtering in rail transit air conditioning while reducing reactive power consumption. It can also be applied to other circuits with harmonic currents, not limited to the rail transit air conditioning field of this embodiment.

[0055] It is easy to understand that the present application does not make any special restrictions on the specific types and implementation methods of the frequency conversion system 3, the air conditioning subsystem and the entire train system. Figure 2 As shown, the frequency conversion system 3 includes a rectifier bridge V2 and a frequency converter VFD. The frequency converter VFD needs to be used in conjunction with the rectifier bridge V2 and capacitor plate C0. The frequency converter VFD is connected to the DC input output of the rectifier bridge through the P interface and the N interface, and is connected to the capacitor plate C0 through the P1 interface and the N interface. The three-phase output terminals U, V, and W of the frequency converter VFD are connected to the compressor motor M1. The frequency converter VFD also has interfaces such as the A interface, the B interface, the GXDC interface, the +5VC interface, the DC interface, the DI1 interface, the DI2 interface, and the +24VB interface. Figure 3As shown, the PLC (Programmable Logic Controller) serves as the master controller of the entire frequency conversion system 3. An IO expansion board is also installed inside the air conditioning unit to control the frequency converter. The IO expansion board includes interfaces such as 24V, GND, CAN1+, CAN1-, 4851+, 4851-, COM1, DO01, and DO02. The PLC communicates with the IO expansion board via the IO expansion board (CAN) and the CAN bus (Controller Area Network). The IO expansion board then connects to the A and B interfaces of the frequency converter via the IO expansion board communication (485) and communicates with the frequency converter via the 485 bus. Power supply G1 serves as the power supply for the IO expansion board, and supplies power to the IO expansion board for use; the inverter communication power supply is connected to the inverter's GXDC interface and +5VC interface to supply power to the communication module in the inverter; power supply G2 serves as the inverter's main power supply, and is connected to the inverter's DI1 interface and +24VB interface to provide 24V power to the inverter. The inverter is enabled by the power supply.

[0056] by Figure 2 Taking the frequency conversion system 3 and the resonant filter circuit shown as an example, a series-connected circuit breaker F1, a circuit breaker F2, and a circuit breaker F3 are further provided between the AC power supply 2 and the input end of the frequency conversion system 3. When the frequency converter is in standby mode, the PLC controls the frequency converter to be disabled through the IO expansion board. The process of enabling or disabling the frequency converter by the PLC can be achieved by controlling the on and off of the circuit breakers F1, F2, and F3. At the same time, the enabling signal of the controllable switch 1 in the resonant filter circuit is not output, so that the LC filter module 4 is The reactor and capacitor are not in use, reducing the reactive power generated by the inverter in standby mode. When the PLC determines the compressor needs to start based on the collected temperature, it prioritizes the DO01 enable output corresponding to the resonant filter circuit, closing contacts KM1, KM2, and KM3 in the resonant filter circuit. The reactor and capacitor in LC filter module 4 are activated, forming an LC circuit. After a specific delay, the PLC controls the inverter enable signal output, starting the inverter and operating it at the required frequency. When the inverter transitions from running to standby, the PLC first shuts down the inverter via RS485 bus communication and disconnects the inverter enable signal. After a specific delay, the PLC disconnects the DO01 enable signal corresponding to the resonant filter circuit, disconnecting contacts KM1, KM2, and KM3 in the resonant filter circuit and removing the capacitor in LC filter module 4 from the circuit, reducing reactive power consumption.

[0057] The utility model provides a resonant filter circuit, comprising a controllable switch 1 and an LC filter module 4 connected to the controllable switch 1. When the frequency conversion system 3 controls the compressor to start, the controllable switch 1 is also turned on, connecting the LC filter module 4 to the circuit between the AC power supply 2 and the frequency conversion system 3, filtering harmonics generated in the circuit and reducing the harmonic current content in the air conditioning subsystem. When the frequency conversion system 3 does not control the compressor to start, the controllable switch 1 remains off, and the LC filter module 4 is not put into use, thereby avoiding the consumption of reactive power by the capacitor therein. The turning on and off of the controllable switch 1 is used to control whether the LC filter module 4 is put into use. While suppressing harmonics in the operating frequency conversion system 3, it also avoids voltage loss and power loss caused by the LC filter module 4 being connected to the circuit when the frequency conversion system 3 is not operating, thereby reducing the reactive power consumption of the entire circuit and the frequency conversion system 3.

[0058] On the basis of the above embodiments;

[0059] As an optional embodiment, the controllable switch 1 includes a contact and a coil, wherein a first end of the contact is connected to the input end of the AC power supply 2 and the frequency conversion system 3 respectively, and a second end is connected to the input end of the LC filter module 4; a first end of the coil is connected to the output end of the controller, and a second end is grounded;

[0060] The coil is used to be energized based on the control of the controller when the frequency conversion system 3 controls the compressor to start, so as to control the contacts to be turned on; and to be de-energized based on the control of the controller when the frequency conversion system 3 does not control the compressor to start, so as to control the contacts to be turned off.

[0061] It is not difficult to understand that the controllable switch 1 can be implemented specifically by using a contactor. In this case, the control of the controllable switch 1 needs to be implemented by using a coil corresponding to the contact. The controller outputs different control signals to the coil according to whether the frequency conversion system 3 is working or not. The contact is normally open by default. When the frequency conversion system 3 is working, the controller will control the coil to be energized, thereby controlling the contact to switch from the off state to the on state; when the frequency conversion system 3 is not working, the controller will control the coil to lose power, thereby controlling the contact to return to the off state. This application does not make any special restrictions on the specific type and implementation method of the controller. In actual applications, the controller in the frequency conversion system 3 can be directly reused. Figure 3 As shown, the coil corresponding to the contact is connected to the inverter control system and connected to the controller's DO01 point. When the controller's DO01 point does not output a signal, the coil is de-energized and the contact does not close. When the controller's DO01 point outputs a preset signal, the coil is energized and the contact closes. This application does not impose any specific restrictions on the specific types and implementation methods of the contacts and coils, and they can be selected and adjusted based on actual application conditions.

[0062] Specifically, the controllable switch 1 can be implemented through a contact plus coil structure. The contact and the LC filter module 4 are connected in series and connected to the input end of the frequency conversion system 3. The coil is connected to the control system as the control end of the contact. In this way, the action control of the controllable switch 1 can be effectively achieved, and the remote control process can be realized at the same time, so that the control of the controllable switch 1 can also be directly reused by the controller in the frequency converter or the frequency conversion system 3, reducing the design cost and volume of the entire resonant filter circuit.

[0063] As an optional embodiment, the method further includes:

[0064] The temperature detection module has an input end connected to the air conditioning subsystem and an output end connected to the input end of the controller, and is used to detect the temperature data of the air conditioning subsystem so that the controller can determine whether to start the compressor based on the temperature data.

[0065] It is understood that once the inverter system 3 controls the compressor to start, the entire air conditioning subsystem will begin operating, providing cooling or heating. The temperature within the air conditioning subsystem will subsequently change. Therefore, determining whether the inverter system 3 is operating, that is, whether the inverter system 3 controls the compressor to start, can be accomplished by detecting the temperature conditions within the air conditioning subsystem. The specific type, implementation, and placement of the temperature detection module can be configured and adjusted based on actual application requirements. Specifically, a temperature sensor can be used. Temperature data includes the return air temperature, fresh air temperature, supply air temperature, and steam temperature set in the air conditioning subsystem. This temperature data is used in the temperature control logic calculations of the air conditioning subsystem. The air conditioning subsystem's temperature control follows the UIC curve. The fresh air temperature determines the operating mode and calculates the target temperature. The return air temperature minus the target temperature is used to calculate the cooling / heating demand. Therefore, the controller can first use the temperature detection module to obtain the air conditioning subsystem's temperature data. Then, based on the UIC curve corresponding to the temperature data, it can determine whether the compressor needs to start. If the compressor needs to start, the inverter system 3 controls the compressor to start, and then controllable switch 1 can be turned on.

[0066] It should be noted that during compressor operation, the controller also determines whether the air conditioning subsystem is operating normally based on the feedback status of the pressure sensor, pressure switch, or preset contactor installed in the unit. If the air conditioning subsystem is operating abnormally, the compressor may be controlled to shut down. Therefore, in actual applications, the operation of the compressor can also be determined by means of a pressure detection module, etc., and is not limited to the method of providing a temperature detection module in this embodiment.

[0067] Specifically, considering the working characteristics of the air-conditioning subsystem, a temperature detection module connected to the air-conditioning subsystem can be set to determine whether the compressor is working or not, thereby determining whether the frequency conversion system 3 is controlling the operation of the compressor, making it convenient for the controller to control the controllable switch 1 in a timely and accurate manner, thereby ensuring the harmonic suppression effect of the entire resonant filter circuit.

[0068] As an optional embodiment, the AC power supply 2 is a three-phase power supply, and the controllable switch 1 includes:

[0069] A first controllable sub-switch, wherein a first end is connected to the first phase line output end of the AC power supply 2 and the first input end of the frequency conversion system 3, and a second end is connected to the input end of the LC filter module 4;

[0070] A second controllable sub-switch, wherein a first end is connected to the second phase line output end of the AC power supply 2 and the second input end of the frequency conversion system 3, and a second end is connected to the input end of the LC filter module 4;

[0071] The second controllable sub-switch has a first end connected to the third phase line output end of the AC power supply 2 and the third input end of the frequency conversion system 3 , and a second end connected to the input end of the LC filter module 4 .

[0072] It is easy to understand that the frequency conversion system 3 generally requires a three-phase AC power supply 2 for power supply, such as Figure 2 As shown, L1', L2', and L3' represent three phase lines respectively, and the frequency conversion system 3 also has three input terminals connected to the three phase lines respectively. Therefore, correspondingly, the controllable switch 1 also needs to be provided with three controllable sub-switches, and the first terminals of the three controllable sub-switches are respectively connected to the three phase lines of the AC power supply 2 that supplies power to the frequency conversion system 3, and the second terminals are all connected to the LC filter module 4, thereby ensuring that the LC filter module 4 can suppress the harmonic currents existing on the three phase lines. The specific types and implementation methods of the first controllable sub-switch, the second controllable sub-switch, and the third controllable sub-switch are not particularly limited in this application. The controller can synchronously control the three controllable sub-switches, or can set the control processes of the three controllable sub-switches independently of each other. Figure 2 As shown, the controllable switch 1 can be realized by using contacts KM1, KM2, KM3 and coil KM0. Contacts KM1, KM2 and KM3 are synchronously controlled by coil KM0. When coil KM0 is energized, contacts KM1, KM2 and KM3 are all closed. When coil KM0 is de-energized, contacts KM1, KM2 and KM3 are all disconnected.

[0073] Specifically, considering the actual application of the frequency conversion system 3, the setting of the controllable switch 1 also needs to be set accordingly according to the actual power supply situation of the frequency conversion system 3 by the AC power supply 2. By setting multiple controllable sub-switches, the harmonic suppression process of multiple power supply lines can be realized, ensuring that the resonant filter circuit can fully suppress the harmonics generated by the frequency conversion system 3.

[0074] As an optional embodiment, the LC filter module 4 includes:

[0075] A first filter reactor L1, a first end of which is connected to the second end of the first controllable sub-switch;

[0076] a second filter reactor L2, a first end of which is connected to the second end of the second controllable sub-switch;

[0077] a third filter reactor L3, a first end of which is connected to the second end of the third controllable sub-switch;

[0078] A first filter capacitor C1;

[0079] A second filtering capacitor C2, a first end of which is connected to the second end of the second filtering reactor L2 and the first end of the first filtering capacitor C1 respectively;

[0080] The third filtering capacitor C3 has a first end connected to the second end of the third filtering reactor L3 and the second end of the second filtering capacitor C2, and a second end connected to the second end of the first filtering reactor L1 and the second end of the first filtering capacitor C1.

[0081] It is understandable that the LC filter module 4 can be implemented by a π-type filter structure including a first filter reactor L1, a second filter reactor L2, a third filter reactor L3, a first filter capacitor C1, a second filter capacitor C2, and a third filter capacitor C3. The three filter capacitors are interconnected to form a triangle structure. If any capacitor is disconnected, the other capacitors can also cooperate with the reactor to implement the filtering process, which has high reliability. The first filter reactor L1 and the first filter capacitor C1 are connected in series to form an LC series circuit, the second filter reactor L2 and the second filter capacitor C2 are connected in series to form an LC series circuit, and the third filter reactor L3 and the third filter capacitor C3 are connected in series to form an LC series circuit. The reactors and capacitors cooperate with each other and utilize the resonance generated when connected in series to effectively implement the filtering process of specific harmonics. The specific types and implementation methods of the first filter reactor L1, the second filter reactor L2, the third filter reactor L3, the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are not particularly limited in this application.

[0082] Specifically, the present invention controls the closing and opening of the contactor within the resonant filter circuit, so that when the inverter is in standby mode, the capacitors in the LC filter module 4 are not used, reducing reactive power. When the inverter is operating, the LC filter module 4 is used to reduce the harmonic current content in the air conditioning subsystem. The circuit implementation of the LC filter module 4 is simple, effective, and highly reliable.

[0083] As an optional embodiment, the method further includes:

[0084] An incoming line reactance module connected in series between the output end of the AC power supply 2 and the first end of the controllable switch 1 and / or an outgoing line reactance module connected in series between the first end of the controllable switch 1 and the input end of the frequency conversion system 3.

[0085] It is not difficult to understand that, based on the first filter reactor L1, the second filter reactor L2, the third filter reactor L3, the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3, an incoming line reactance module and / or an outgoing line reactance module connected in series can be added between the AC power supply 2 and the input end of the frequency conversion system 3. The reactors in the incoming line reactance module and / or the outgoing line reactance module form a parallel connection relationship with the capacitors in the LC filter module 4, forming an LC parallel circuit, and the resonance generated during parallel connection is used to realize the harmonic filtering process. At different harmonic frequencies, series resonance or parallel resonance may occur in the LC filter module 4, thereby improving the filtering effect of the entire LC filter module 4. This application does not specifically limit the specific type and implementation method of the incoming line reactance module and / or the outgoing line reactance module.

[0086] Specifically, in order to improve the filtering effect of the entire LC filter module 4, after the series-connected inductor and capacitor are set in the LC filter module 4, an incoming line inductor module and / or an outgoing line inductor module connected in series between the AC power supply 2 and the input end of the frequency conversion system 3 can be added to form a parallel connection structure with the capacitor therein to ensure the filtering effect of the entire LC filter module 4.

[0087] As an optional embodiment, the incoming line reactance module includes:

[0088] A first line reactor L11, having a first end connected to the first phase line output end of the AC power source 2, and a second end connected to the first end of the first controllable sub-switch and the first input end of the frequency conversion system 3;

[0089] A second line reactor L12, having a first end connected to the second phase line output terminal of the AC power source 2, and a second end connected to the first end of the second controllable sub-switch and the second input terminal of the frequency conversion system 3;

[0090] The third line reactor L13 has a first end connected to the third phase line output end of the AC power source 2 , and a second end connected to the first end of the third controllable sub-switch and the third input end of the frequency conversion system 3 .

[0091] It is not difficult to understand that, considering the actual application of the frequency conversion system 3, it is also preferable to provide the first incoming line reactor L11, the second incoming line reactor L12, and the third incoming line reactor L13, which are respectively connected in series with the three phase lines, in the incoming line reactor module, so that the first incoming line reactor L11 can form a parallel resonant structure with the first filter capacitor C1, the second incoming line reactor L12 can form a parallel resonant structure with the second filter capacitor C2, and the third incoming line reactor L13 can form a parallel resonant structure with the third filter capacitor C3. The specific types and implementation methods of the first incoming line reactor L11, the second incoming line reactor L12, and the third incoming line reactor L13 are not particularly limited in this application. The specific inductance values ​​can be selected and set according to the specific situation of the harmonics to be filtered.

[0092] Specifically, considering the actual application of the frequency conversion system 3, the setting of the incoming line inductor module also needs to be set accordingly according to the actual power supply situation of the frequency conversion system 3 by the AC power supply 2. By setting multiple incoming line inductors, the harmonic suppression process of multiple power supply lines can be realized, ensuring that the resonant filter circuit can fully suppress the harmonics generated by the frequency conversion system 3.

[0093] As an optional embodiment, the outgoing line reactance module includes:

[0094] A first outgoing line reactor L21, having a first end connected to the second end of the first incoming line reactor L11 and the first end of the first controllable sub-switch, and a second end connected to the first input end of the frequency conversion system 3;

[0095] A second outgoing line reactor L22, having a first end connected to the second end of the second incoming line reactor L12 and the first end of the second controllable sub-switch, and a second end connected to the second input end of the frequency conversion system 3;

[0096] The third outgoing line reactor L23 has a first end connected to the second end of the third incoming line reactor L13 and the first end of the third controllable sub-switch respectively, and a second end connected to the third input end of the frequency conversion system 3 .

[0097] It is not difficult to understand that, considering the actual application of the frequency conversion system 3, it is also preferable to provide the output line reactor module with a first output line reactor L21, a second output line reactor L22, and a third output line reactor L23, which are respectively connected in series with the three phase lines, so that the first output line reactor L21 can form a parallel resonant structure with the first filter capacitor C1, the second output line reactor L22 can form a parallel resonant structure with the second filter capacitor C2, and the third output line reactor L23 can form a parallel resonant structure with the third filter capacitor C3. The specific types and implementation methods of the first output line reactor L21, the second output line reactor L22, and the third output line reactor L23 are not particularly limited in this application. The specific inductance values ​​can be selected and set according to the specific situation of the harmonics to be filtered.

[0098] Specifically, considering the actual application of the frequency conversion system 3, the setting of the outgoing line inductor module also needs to be set accordingly according to the actual power supply situation of the frequency conversion system 3 by the AC power supply 2. By setting multiple outgoing line inductors, the harmonic suppression process of multiple power supply lines can be realized, ensuring that the resonant filter circuit can fully suppress the harmonics generated by the frequency conversion system 3.

[0099] As a specific embodiment, Figure 2 As shown, inside the resonant filter circuit, contacts KM1, KM2, and KM3 are added to the front end of the filter reactor and the filter capacitor. The three contacts can be simultaneously controlled to be closed and disconnected to control whether the filter capacitor in the LC filter module 4 is put into use. Before the contacts are closed, only the incoming line reactor and the outgoing line reactor are working, and the LC filter module 4 as a whole can be used as an AC input reactor to increase the power supply impedance. After the contacts are closed, the reactor and capacitor at the lower end of the contacts, that is, the filter reactor and filter capacitor in the LC filter module 4, form an LC series circuit. When the input power frequency is close to or even equal to the LC resonant frequency, the corresponding LC series circuit impedance is minimum, and the frequency signal can easily pass through the LC filter module 4 and be output. The capacitor in the LC filter module 4 is connected in parallel with the incoming line reactor and / or the outgoing line reactor to form an LC parallel circuit. If the current flowing through the incoming line reactor and / or the outgoing line reactor is equivalent to the current of the capacitor, the circuit reaches a parallel resonance state. At this time, the corresponding impedance is maximum, and the corresponding frequency signal cannot pass through the LC parallel circuit.

[0100] To solve the above technical problems, the present invention further provides a resonant filter device, comprising a controller and the above-mentioned resonant filter circuit, wherein the output end of the controller is connected to the control end of the controllable switch 1 in the resonant filter circuit.

[0101] For an introduction to a resonant filter device provided by the present invention, please refer to the above-mentioned embodiment of the resonant filter circuit, and the present invention will not be described in detail here.

[0102] In order to solve the above technical problems, the present invention also provides a frequency conversion device, including a rectifier circuit, an inverter circuit and a resonant filter device as described above, the output end of the resonant filter device is connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the compressor.

[0103] It is understood that a frequency conversion device generally uses a frequency conversion system 3 including circuit modules such as a rectifier circuit and an inverter circuit to implement the frequency conversion control process. The resonant filter circuit provided in this application is generally provided at the front end of the frequency conversion system 3. The input end of the resonant filter circuit is the input of the AC power supply 2, and the output end is the rectifier bridge in the frequency conversion system 3. This application does not specifically limit the specific types and implementation methods of the rectifier circuit, inverter circuit, and other circuit modules in the frequency conversion system 3, and they can be configured according to actual application conditions.

[0104] For an introduction to a frequency conversion device provided by the present invention, please refer to the embodiment of the resonant filter circuit described above, and the present invention will not be described in detail here.

[0105] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can be referred to each other. It should also be noted that in this specification, relational terms such as first and second 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 terms "comprise", "include" or any other variants thereof are 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 other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "comprise a..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0106] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A resonant filter circuit, characterized in that: include: a controllable switch, a first end of which is connected to the output end of the AC power supply and the input end of the frequency conversion system respectively, and is configured to be turned on when the frequency conversion system controls the compressor to start, and turned off when the frequency conversion system does not control the compressor to start; The LC filter module connected to the second end of the controllable switch is used to maintain connection with the input end of the frequency conversion system to filter out harmonics when the controllable switch is turned on.

2. The resonant filter circuit according to claim 1, wherein: The controllable switch includes a contact and a coil, wherein the first end of the contact is connected to the input end of the AC power supply and the frequency conversion system respectively, and the second end is connected to the input end of the LC filter module; the first end of the coil is connected to the output end of the controller, and the second end is grounded; The coil is used to be energized based on the control of the controller when the variable frequency system controls the compressor to start, so as to control the contacts to be turned on; and to lose power based on the control of the controller when the variable frequency system does not control the compressor to start, so as to control the contacts to be turned off.

3. The resonant filter circuit according to claim 1, wherein: Also includes: The temperature detection module has an input end connected to the air conditioning subsystem and an output end connected to the input end of the controller, and is used to detect temperature data of the air conditioning subsystem so that the controller can determine whether to start the compressor based on the temperature data.

4. The resonant filter circuit according to any one of claims 1 to 3, wherein: The AC power supply is a three-phase power supply, and the controllable switch includes: a first controllable sub-switch, wherein a first end is connected to the first phase line output end of the AC power supply and the first input end of the frequency conversion system respectively, and a second end is connected to the input end of the LC filter module; a second controllable sub-switch, wherein a first end is connected to the second phase line output end of the AC power supply and the second input end of the frequency conversion system respectively, and a second end is connected to the input end of the LC filter module; The third controllable sub-switch has a first end connected to the third phase line output end of the AC power supply and the third input end of the frequency conversion system respectively, and a second end connected to the input end of the LC filter module.

5. The resonant filter circuit according to claim 4, wherein: The LC filter module includes: a first filter reactor, a first end of which is connected to the second end of the first controllable sub-switch; a second filter reactor, a first end of which is connected to the second end of the second controllable sub-switch; a third filter reactor, a first end of which is connected to the second end of the third controllable sub-switch; a first filter capacitor; a second filter capacitor, a first end of which is respectively connected to the second end of the second filter reactor and the first end of the first filter capacitor; The third filter capacitor has a first end connected to the second end of the third filter inductor and the second end of the second filter capacitor respectively, and a second end connected to the second end of the first filter inductor and the second end of the first filter capacitor respectively.

6. The resonant filter circuit according to claim 5, wherein: Also includes: An incoming line reactance module connected in series between the output end of the AC power supply and the first end of the controllable switch and / or an outgoing line reactance module connected in series between the first end of the controllable switch and the input end of the frequency conversion system.

7. The resonant filter circuit according to claim 6, wherein: The incoming line reactance module includes: a first incoming line reactor, a first end of which is connected to the first phase line output end of the AC power supply, and a second end of which is respectively connected to the first end of the first controllable sub-switch and the first input end of the frequency conversion system; a second line reactor, a first end of which is connected to the second phase line output end of the AC power supply, and a second end of which is respectively connected to the first end of the second controllable sub-switch and the second input end of the frequency conversion system; The third incoming line reactor has a first end connected to the third phase line output end of the AC power supply, and a second end connected to the first end of the third controllable sub-switch and the third input end of the frequency conversion system respectively.

8. The resonant filter circuit according to claim 7, wherein: The outgoing line reactance module includes: a first outgoing line reactor, a first end of which is respectively connected to the second end of the first incoming line reactor and the first end of the first controllable sub-switch, and a second end of which is connected to the first input end of the frequency conversion system; a second outgoing line reactor, a first end of which is respectively connected to the second end of the second incoming line reactor and the first end of the second controllable sub-switch, and a second end of which is connected to the second input end of the frequency conversion system; The third outgoing line reactor has a first end connected to the second end of the third incoming line reactor and the first end of the third controllable sub-switch respectively, and a second end connected to the third input end of the frequency conversion system.

9. A resonant filter device, characterized in that: The invention comprises a controller and the resonant filter circuit according to any one of claims 1 to 8, wherein the output end of the controller is connected to the control end of a controllable switch in the resonant filter circuit.

10. A frequency conversion device, characterized in that: It comprises a rectifier circuit, an inverter circuit and the resonant filter device as claimed in claim 9, wherein the output end of the resonant filter device is connected to the input end of the rectifier circuit, the output end of the rectifier circuit is connected to the input end of the inverter circuit, and the output end of the inverter circuit is connected to the compressor.

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