Active EMI filter, frequency converter and air conditioning system

Abstract

The invention discloses an active EMI filter, a frequency converter and an air conditioning system. The filter comprises a detection network module, a signal processing module and an injection network module, the signal processing module comprises a sampling detection circuit, a gain circuit comprising a gain adjusting element and a signal injection circuit, and the capacitance volume corresponding to a preset capacitor in the filter is smaller than a preset volume threshold value. The predetermined capacitors comprise at least one of the following capacitors: a detection capacitor included in the detection network module and an injection capacitor included in the injection network module. By adopting a small-capacitance preset capacitance cooperation and dynamic gain regulation and control mode, the purpose of eliminating noise while greatly reducing the size of the filter is achieved, bidirectional optimization of filter miniaturization and high noise filtering precision is realized, and the problem that in the prior art, noise is not easily generated when noise signals are processed is solved. And the filter volume and the noise filtering precision are difficult to balance.

Description

Active EMI filters, frequency converters and air conditioning systems Technical Field

[0001] This invention relates to the field of filters, and more specifically, to an active EMI filter, a frequency converter, and an air conditioning system. Background Technology

[0002] EMI filtering is a key technology for ensuring electronic equipment complies with electromagnetic compatibility regulations, guaranteeing system reliability, and enhancing product competitiveness. As high-power switching power supply devices, frequency converters must undergo effective EMI filtering to meet international standards, prevent interference with the power grid and other equipment, and ensure their own stable operation.

[0003] Currently, the traditional passive EMI filters commonly used in frequency converters have a core architecture consisting of a multi-stage π-type filter network composed of a large-inductance common-mode inductor, an X capacitor, and a Y capacitor. This approach has revealed a series of technical shortcomings in practical applications:

[0004] Traditional solutions often struggle to achieve effective filtering with smaller components, while larger components are bulky and heavy. Common-mode inductors and their core materials result in individual filters weighing over 200 grams, and high-performance core materials account for a significant portion of the cost. Multi-stage filtering networks further increase production costs and maintenance complexity, severely impacting overall costs and hindering miniaturization. Therefore, a significant technical challenge exists in balancing filter size and noise filtering accuracy.

[0005] There is currently no effective solution to the above problems. Summary of the Invention

[0006] This invention provides an active EMI filter, a frequency converter, and an air conditioning system to at least solve the technical problem in the related art of balancing filter size and noise filtering accuracy when processing noise signals.

[0007] According to one aspect of the present invention, an active electromagnetic interference (EMI) filter is provided, comprising: a detection network module, a signal processing module, and an injection network module, wherein the signal processing module includes a sampling detection circuit, a gain circuit, and a signal injection circuit, the gain circuit includes a gain adjustment element, and the volume of a predetermined capacitor in the filter is less than a predetermined volume threshold, the predetermined capacitor including at least one of the following: a detection capacitor included in the detection network module, an injection capacitor included in the injection network module, a first terminal of the detection network module connected to the live wire of the power grid, a second terminal of the detection network module connected to the neutral wire of the power grid, a third terminal connected to the first terminal of the sampling detection circuit, and a fourth terminal connected to the second terminal of the sampling detection circuit; the third terminal of the sampling detection circuit connected to the first terminal of the gain circuit; the second terminal of the gain circuit connected to the first terminal of the signal injection circuit; the second terminal of the signal injection circuit connected to the first terminal of the injection network module; and the second terminal of the injection network module connected to a common connection point, wherein the common connection point is the common connection point between the live wire and the neutral wire.

[0008] Optionally, the filter further includes a common-mode inductor, comprising a pre-stage common-mode inductor and a post-stage common-mode inductor. The first terminal of the pre-stage common-mode inductor is connected to the live wire of the external power grid, the second terminal is connected to the neutral wire of the external power grid, the third terminal is connected to the first terminal of the detection network module, and the fourth terminal is connected to the second terminal of the detection network module. The first terminal of the post-stage common-mode inductor is connected to the live wire after the common connection point, the second terminal is connected to the neutral wire after the common connection point, the third terminal constitutes the live wire output terminal, and the fourth terminal constitutes the neutral wire output terminal.

[0009] Optionally, the injection network module includes an injection capacitor, wherein one end of the injection capacitor forms a first terminal corresponding to the injection network module and is connected to a second terminal corresponding to the signal injection circuit, and the other end of the injection capacitor forms a second terminal corresponding to the injection network module and is connected to the common connection point; the injection capacitor is used to receive the cancellation signal, obtain the cancellation power parameter, and inject the cancellation power parameter into the common connection point to cancel the original noise signal and obtain the target denoised signal.

[0010] Optionally, the capacitance parameters corresponding to the injected capacitor are set as injected capacitor parameters, wherein the injected capacitor parameters include at least one of the following: the physical capacitance range corresponding to the application scenario, and the active equivalent capacitance value. The active equivalent capacitance value is determined based on the physical capacitance value of the injected capacitor and the gain coefficient in the gain circuit. In the case where the application scenario includes an air conditioning scenario, the corresponding physical capacitance range is 470pF-2.2nF. The gain coefficient is adjusted by the gain circuit, the active equivalent capacitance value is updated, and the frequency of the cancellation signal is adjusted to obtain a signal with a frequency that meets a predetermined condition. The signal that meets the predetermined condition is converted into a cancellation power parameter and injected into the common connection point. It is then superimposed and canceled with the original noise signal to obtain the target denoised signal. The predetermined condition is that the capacitive reactance generated by the active equivalent capacitance value to the cancellation signal is within a predetermined resistance range.

[0011] Optionally, when the original mixed signal includes a live wire noise component and a neutral wire noise component, the detection network module includes a detection capacitor, which includes a first detection capacitor and a second detection capacitor. One end of the first detection capacitor forms a first terminal corresponding to the detection network module and is connected to the live wire of the power grid; the other end of the first detection capacitor forms a third terminal corresponding to the detection network module and is connected to the first terminal corresponding to the sampling detection circuit. One end of the second detection capacitor forms a second terminal corresponding to the detection network module and is connected to the neutral wire of the power grid; the other end of the second detection capacitor forms a fourth terminal corresponding to the detection network module and is connected to the second terminal corresponding to the sampling detection circuit. The first detection capacitor is used to collect the live wire noise component relative to a reference point, and the second detection capacitor is used to collect the neutral wire noise component relative to a reference point, where the reference point is the internal common ground point of the active EMI filter.

[0012] Optionally, it further includes an enable control circuit, wherein a first terminal of the enable control circuit is used to connect to an external control signal source, a second terminal is connected to the enable control terminal of the signal processing module, a third terminal of the enable control circuit is connected to the internal power supply terminal of the filter, and a fourth terminal is connected to the ground line; the enable control circuit is used to receive the enable signal output by the external control signal source, and to control the start and stop state of the signal processing module to realize the start and stop control of the filter.

[0013] Optionally, it also includes an AC-DC converter, wherein a first terminal of the AC-DC converter is connected to the live wire after the common connection point; a second terminal of the AC-DC converter is connected to the neutral wire after the common connection point; and a third terminal of the AC-DC converter is connected to the grounding line.

[0014] Optionally, the signal processing module further includes a temperature compensation module, wherein a first terminal of the temperature compensation module is connected to the internal main control unit of the signal processing module, and a second terminal is connected to the coefficient feedback terminal of the gain circuit; the temperature compensation module is used to collect the ambient temperature and correct the processing parameters of the signal processing module according to the ambient temperature, the processing parameters including the gain coefficient.

[0015] Optionally, the capacitance parameters corresponding to the detection capacitor are set as target capacitance parameters, wherein the target capacitance parameters include at least one of the following: capacitance range in the corresponding application scenario, withstand voltage rating in the corresponding application scenario, and in the case where the application scenario includes an air conditioning scenario, the corresponding capacitance range is 100pF-4.7nF, and the corresponding withstand voltage rating is greater than or equal to 275VAC.

[0016] Optionally, the inductance parameters corresponding to the common-mode inductor are set as target inductance parameters, wherein the target inductance parameters include: the inductance range in the corresponding application scenario. In the case where the application scenario includes an air conditioning scenario, the corresponding inductance range is 100uH-900uH.

[0017] Optionally, the sampling and detection circuit includes a detection filtering unit, and the filtering parameters corresponding to the detection filtering unit are set as target filtering parameters. The target filtering parameters include the effective operating frequency band range of the bandpass filter in the corresponding application scenario. In the case that the application scenario includes an air conditioning scenario, the corresponding effective operating frequency band range is 150kHz-3MHz, so as to filter out the first noise signal in the original noise signal within the corresponding effective operating frequency band range.

[0018] According to one aspect of the present invention, a frequency converter is provided, including an active EMI filter and a rectifier bridge as described above, wherein the input terminal corresponding to the active EMI filter serves as the external power grid interface of the frequency converter, the output terminal corresponding to the active EMI filter is connected to the input terminal of the rectifier bridge, the external power grid interface represents the interface of the frequency converter for connecting to the external power grid, and is used to realize the power connection between the frequency converter and the external power grid, the corresponding input terminal includes a first terminal and a second terminal corresponding to the detection network module, and the corresponding output terminal includes a live wire output terminal and a neutral wire output terminal after the common connection point.

[0019] According to one aspect of the present invention, an air conditioning system is provided, including an air conditioning body and an inverter as described above located within the air conditioning body.

[0020] According to one aspect of the present invention, a noise cancellation method for the above-described active EMI filter is provided, comprising: controlling a detection network module to acquire a raw mixed signal between a live wire and a neutral wire in a power grid, wherein the raw mixed signal includes a raw noise signal; controlling a sampling detection circuit to filter the raw mixed signal to obtain a first noise signal; controlling a gain circuit to adjust a corresponding gain coefficient according to the amplitude of the first noise signal through a gain adjustment element, and performing gain processing on the first noise signal with the adjusted gain coefficient to obtain a second noise signal with a corresponding amplitude within a predetermined amplitude range; controlling a signal injection circuit to obtain a cancellation signal with a phase opposite to and amplitude matching that of the raw noise signal according to the amplitude and phase of the second noise signal; and controlling an injection network module to obtain a cancellation power parameter injected to the point of common coupling according to the cancellation signal to cancel the raw noise signal and obtain a target denoised signal.

[0021] In this embodiment of the invention, a detection network module, a signal processing module, and an injection network module are included. The signal processing module includes a sampling detection circuit, a gain circuit, and a signal injection circuit. The gain circuit includes a gain adjustment element. The volume of a predetermined capacitor in the filter is less than a predetermined volume threshold. The predetermined capacitor includes at least one of the following: a detection capacitor included in the detection network module; an injection capacitor included in the injection network module; a first terminal of the detection network module connected to the live wire of the power grid, a second terminal connected to the neutral wire of the power grid, a third terminal connected to the first terminal of the sampling detection circuit, and a fourth terminal connected to the second terminal of the sampling detection circuit; a third terminal of the sampling detection circuit connected to the first terminal of the gain circuit; a second terminal of the gain circuit connected to the first terminal of the signal injection circuit; a second terminal of the signal injection circuit connected to the first terminal of the injection network module; and a second terminal of the injection network module connected to a common connection point, wherein the common connection point is the common connection point between the live wire and the neutral wire. The system comprises the following components: a detection network module for acquiring the raw mixed signal between the live and neutral wires, including raw noise; a sampling detection circuit for filtering the raw mixed signal to obtain a first noise signal; a gain circuit for adjusting the gain coefficient of the first noise signal using a gain adjustment element based on its amplitude, and then applying the adjusted gain coefficient to the first noise signal to obtain a second noise signal with an amplitude within a predetermined range; a signal injection circuit for obtaining a cancellation signal with the opposite phase and matching amplitude to the original noise signal based on the amplitude and phase of the second noise signal; and an injection network module for obtaining the cancellation power parameters injected to the common connection point based on the cancellation signal to cancel the original noise signal, thus obtaining the target denoised signal. By employing a small-value predetermined capacitor and dynamic gain control, the system achieves a significant reduction in filter size while maintaining the accuracy of targeted noise suppression. This results in a bidirectional optimization of filter miniaturization and high noise filtering accuracy, solving the technical problem in related technologies where it is difficult to balance filter size and noise filtering accuracy when processing noise signals. Attached Figure Description

[0022] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0023] Figure 1 is a structural block diagram of an active electromagnetic interference (EMI) filter device according to an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the structure of an active EMI filter provided in an optional embodiment of the present invention;

[0025] Figure 3 is a flowchart of an active electromagnetic interference (EMI) filter method according to an embodiment of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0028] Example 1

[0029] According to an embodiment of the present invention, an embodiment of an active electromagnetic interference (EMI) filter device is provided.

[0030] Figure 1 is a structural block diagram of an active electromagnetic interference (EMI) filter device according to an embodiment of the present invention. As shown in Figure 1, the device includes: a detection network module 102, a signal processing module 104, and an injection network module 106. The signal processing module includes a sampling detection circuit 1042, a gain circuit 1044, and a signal injection circuit 1046. The gain circuit includes a gain adjustment element. The capacitance corresponding to a predetermined capacitor in the filter is less than a predetermined capacitance threshold. The predetermined capacitor includes at least one of the following: a detection capacitor included in the detection network module, and an injection capacitor included in the injection network module. The device will now be described in detail.

[0031] The first terminal of the detection network module is connected to the live wire of the power grid, the second terminal is connected to the neutral wire of the power grid, the third terminal is connected to the first terminal of the sampling detection circuit, the fourth terminal is connected to the second terminal of the sampling detection circuit, the third terminal of the sampling detection circuit is connected to the first terminal of the gain circuit, the second terminal of the gain circuit is connected to the first terminal of the signal injection circuit, the second terminal of the signal injection circuit is connected to the first terminal of the injection network module, and the second terminal of the injection network module is connected to the common connection point, where the common connection point is the common connection point between the live wire and the neutral wire.

[0032] In this device, a detection network module is used to acquire the original mixed signal between the live wire and the neutral wire, wherein the original mixed signal includes an original noise signal; a sampling detection circuit is used to filter the original mixed signal to obtain a first noise signal; a gain circuit is used to adjust the corresponding gain coefficient according to the amplitude of the first noise signal through a gain adjustment element, and to perform gain processing on the first noise signal with the adjusted gain coefficient to obtain a second noise signal with an amplitude within a predetermined amplitude range; a signal injection circuit is used to obtain a cancellation signal with opposite phase and matching amplitude to the original noise signal according to the amplitude and phase of the second noise signal; an injection network module is used to obtain the cancellation power parameters injected to the common connection point according to the cancellation signal to cancel the original noise signal, so as to obtain the target denoised signal.

[0033] This involves a detection network module, which is used to collect the original mixed signal between the live wire and the neutral wire in the power grid. The detection network module is a circuit unit set at the power grid input end and connected to the live wire and the neutral wire. It directly collects the original mixed signal present in the power grid. This signal may contain both normal power frequency components and original noise signals generated by switching power supplies such as frequency converters, so that the original noise signals can be processed later.

[0034] The original mixed signal is a composite electrical signal containing power frequency signal and noise between the live wire and neutral wire of the power grid, which is the direct target of EMI filtering. The original noise signal is the electromagnetic interference component mixed in the original mixed signal that needs to be filtered out or canceled.

[0035] This involves a sampling and detection circuit used to filter the original mixed signal to obtain a first noise signal. The sampling and detection circuit is located at the output of the detection network module and performs preliminary processing on the original mixed signal. Its main function is to filter out the power frequency components in the signal and extract the effective noise signal, providing a clean noise input for subsequent gain and phase inversion processing. The first noise signal is the noise signal obtained after the original mixed signal has been filtered by the sampling and detection circuit; most of the power frequency components have been filtered out, making it purer and easier for subsequent processing.

[0036] This involves a gain circuit, which adjusts the corresponding gain coefficient based on the amplitude of the first noise signal using a gain adjustment element, and performs gain processing on the first noise signal with the adjusted gain coefficient to obtain a second noise signal with an amplitude within a predetermined range. The gain circuit is a circuit connected after the sampling and detection circuit that adjusts the amplitude of the extracted noise signal. It includes a gain adjustment element, which can change the gain brought by the gain circuit by adjusting the power parameters, thereby adaptively amplifying the noise signal to make its amplitude reach a level suitable for injection cancellation.

[0037] The gain adjustment element is the core adjustable element of the gain circuit. It can change the gain coefficient of the gain circuit by adjusting its own power parameters (such as resistance and voltage), so as to realize the dynamic adaptation and adjustment of the amplitude of the input noise signal. It is a key element to make up for the insufficient signal amplitude of small capacitance.

[0038] The predetermined capacitors are core capacitor components pre-set in the filter for noise acquisition or signal injection. Specifically, they include the detection capacitor of the detection network module and / or the injection capacitor of the injection network module. Their key characteristics are small capacitance and small size, which are crucial for filter miniaturization. The corresponding capacitor volume is less than a predetermined volume threshold, which is the upper limit of the preset capacitor volume to achieve the filter miniaturization goal. The volume of the predetermined capacitor must be lower than this threshold to ensure that the volume of the capacitor itself and the entire filter meets the space constraints of the installation scenario (such as an air conditioner outdoor unit).

[0039] It should be noted that in related technologies, large-value capacitors are generally selected as the predetermined capacitors, such as detection capacitors and injection capacitors, to meet the performance requirements of noise coupling and current injection. However, large capacitance means larger electrode area and thicker dielectric, resulting in a bulky filter. This application, through the setting of a gain adjustment element in the gain circuit, can detect the amplitude of the first noise signal coupled to the small-value capacitor in real time and dynamically adjust the gain coefficient. For example, the gain coefficient can be adjusted to a factor corresponding to amplifying the signal by 20-100 times, amplifying the weak mV-level signal to a predetermined amplitude range, such as 20mV-500mV, forming a second noise signal. This avoids the traditional method of increasing the capacitance of the detection capacitor to increase the amplitude of the coupled signal. The small-value capacitor, through gain amplification, obtains an effective signal amplitude comparable to that of a traditional large-value detection capacitor, satisfying the processing requirements of subsequent circuits while achieving miniaturization of the detection capacitor.

[0040] This involves a signal injection circuit, used to generate a cancellation signal with opposite phase and matching amplitude to the original noise signal based on the amplitude and phase of the second noise signal. The signal injection circuit is connected after the gain circuit and is used to generate the cancellation signal. Based on the amplitude and phase information of the amplified noise signal, it generates an inverted signal with opposite phase and equal amplitude to the original noise signal, thus achieving vector cancellation of the noise. The second noise signal is obtained by amplifying and adjusting the first noise signal through the gain circuit, with its amplitude adjusted to a level suitable for generating the cancellation signal.

[0041] The cancellation signal is an inverse signal generated based on the second noise signal. It is opposite in phase and matches the amplitude of the original noise signal. It is used to cancel the original noise after being injected into the power grid.

[0042] This involves an injection network module, which is used to obtain the cancellation power parameters injected to the point of common coupling based on the cancellation signal, so as to cancel the original noise signal and obtain the target denoised signal. The injection network module is a circuit unit connected between the output of the signal injection circuit and the point of common coupling of the power grid. It is responsible for injecting the generated cancellation signal into the power grid in the form of current, so that it is superimposed and canceled with the original noise signal on the line at the point of common coupling.

[0043] The point of common coupling (PCC) is the electrical connection node between the live and neutral wires in the power grid. It is the location where the canceling power parameters are injected and a key node for the superposition and cancellation of the original noise signal and the canceling signal, thus affecting the final noise suppression effect. The target denoised signal is the signal obtained on the line after the PCC, after the noise components in the original mixed signal have been partially or completely canceled by the canceling power parameters. The EMI noise level of this signal is significantly reduced, meeting electromagnetic compatibility standards. The canceling power parameters are the current actually injected into the PCC after the canceling signal is converted by the injection network module. This current, superimposed on the line noise current, achieves mutual cancellation of noise energy.

[0044] By setting up the above device and using a combination of small-value predetermined capacitors and dynamic gain control, the goal of significantly reducing the size of the filter while ensuring the accuracy of targeted noise signal suppression is achieved. This realizes the technical effect of bidirectional optimization of filter miniaturization and high noise filtering accuracy, and solves the technical problem in related technologies where it is difficult to balance filter size and noise filtering accuracy when processing noise signals.

[0045] As an optional embodiment, a common-mode inductor is also included. The common-mode inductor includes a pre-stage common-mode inductor and a post-stage common-mode inductor. The first terminal of the pre-stage common-mode inductor is connected to the live wire of the external power grid, the second terminal is connected to the neutral wire of the external power grid, the third terminal is connected to the first terminal of the detection network module, and the fourth terminal is connected to the second terminal of the detection network module. The first terminal of the post-stage common-mode inductor is connected to the live wire after the common connection point, the second terminal is connected to the neutral wire after the common connection point, the third terminal of the post-stage common-mode inductor constitutes the live wire output terminal, and the fourth terminal of the post-stage common-mode inductor constitutes the neutral wire output terminal.

[0046] In this alternative embodiment, an implementation scheme is described that adds two stages of common-mode inductors, one before and one after, to help improve the overall electromagnetic interference suppression effect in addition to the basic active cancellation architecture.

[0047] This involves a pre-stage common-mode inductor, a magnetic core inductor located between the mains input and the detection network module, with its two windings connected in series with the live and neutral wires, respectively. Its main function is to provide preliminary common-mode noise suppression before noise signals enter the detection network. Specifically, the pre-stage common-mode inductor can suppress common-mode interference signals from the external power grid, including electromagnetic interference coupled from the grid side and surge interference, from entering the filter. Simultaneously, it prevents interference signals inside the filter from leaking back to the external power grid, avoiding grid-side interference affecting the detection network's accurate acquisition of the original noise signal, and providing a stable signal input environment for subsequent active cancellation stages.

[0048] This involves a post-stage common-mode inductor, a magnetic core inductor located between the common connection point and the filter output. Its two windings are connected in series with the live and neutral wires, respectively. The inductance range matches that of the pre-stage inductor. Its main function is to passively filter any residual common-mode noise that may remain on the lines after active cancellation, ensuring that the noise level at the output meets standard requirements. In other words, the post-stage common-mode inductor further suppresses any residual common-mode noise that may remain after active cancellation, as well as potential new common-mode interference in the filtering link. It performs secondary purification on the initial denoised signal output from the common connection point, ensuring that the target denoised signal delivered to the load through the live and neutral wire outputs has higher purity, while protecting the load from performance abnormalities or damage caused by common-mode interference.

[0049] This embodiment enables the construction of a highly efficient hybrid filtering architecture. Preliminary filtering is achieved through a front-stage common-mode inductor, precise dynamic cancellation by the core active module, and final purification by a rear-stage common-mode inductor, forming a multi-stage, collaborative filtering system. This setup also enhances the system's ability to suppress sudden interference. The front-stage common-mode inductor attenuates transient surges or sudden interference from the power grid, protecting the downstream detection network and signal processing modules. The rear-stage common-mode inductor suppresses transient noise spikes that the active module may not have fully canceled, improving output stability. This improves the operating environment and stability of the active system, making the active cancellation loop operate more stably and accurately.

[0050] As an optional embodiment, the injection network module includes an injection capacitor, wherein one end of the injection capacitor forms a first terminal corresponding to the injection network module and is connected to a second terminal corresponding to the signal injection circuit, and the other end of the injection capacitor forms a second terminal corresponding to the injection network module and is connected to a common connection point; the injection capacitor is used to receive the cancellation signal, obtain the cancellation power parameters, and inject the cancellation power parameters into the common connection point to cancel the original noise signal and obtain the target denoised signal.

[0051] In this alternative embodiment, one specific implementation of the injection network module is described, in which the processed cancellation signal is coupled and injected into the common connection point of the power grid through an injection capacitor.

[0052] This involves an injection capacitor, a capacitor connected between the output of the signal injection circuit and the common point of connection of the power grid. It receives the cancellation signal output from the signal injection circuit, converts it into cancellation electrical parameters that can physically cancel the original noise signal, and precisely injects it into the power grid loop, thus achieving noise vector superposition cancellation—a key interface component. Optionally, the parameters of the injection capacitor can be set. For example, the physical capacitance value can be less than a predetermined capacitance threshold, ranging from 470pF to 2.2nF. It can also be set with a certain withstand voltage rating, such as a withstand voltage rating not lower than 275VAC.

[0053] This involves the cancellation power parameter, which refers to the physical quantity that can be directly injected into the power grid common connection point after the injection capacitor of the injection network module receives the cancellation signal output by the signal injection circuit. The cancellation power parameter can be the cancellation current or it can include the cancellation voltage. Its essence is to carry an electromagnetic quantity with the opposite phase and amplitude matching characteristics to the original noise signal. It is used to perform vector superposition with the corresponding power parameter noise signal of the original noise signal at the circuit physical level to achieve noise cancellation.

[0054] This embodiment provides a precise and controllable injection path by directly connecting the signal injection circuit and the common connection point through a single small-value injection capacitor. It utilizes the capacitor's AC-passing and DC-blocking characteristics to accurately convert the cancellation signal into cancellation power parameters and efficiently inject them into the power grid, achieving precise cancellation of common-mode and differential-mode noise. The capacitor's impedance characteristics ensure a definite linear relationship between the amplitude and phase of the injected current and the cancellation signal voltage, facilitating precise control of the injected cancellation power parameters through pre-processing, thus achieving accurate noise cancellation. The small capacitance value also supports filter miniaturization, while providing electrical isolation to protect downstream circuits and reduce leakage current risks. Furthermore, it works in conjunction with the gain circuit to compensate for the short capacitive reactance of the small-value capacitor. While simplifying the structure and controlling costs, it balances high-frequency adaptability, cancellation accuracy, and system safety, perfectly meeting the core requirements of EMI noise treatment in variable frequency air conditioners. Moreover, it can work with the gain circuit to achieve a capacitance multiplication effect. By adjusting the gain coefficient of the gain circuit, the capacitive reactance of the injection capacitor can be equivalently changed, achieving the filtering effect of an equivalent large-capacity capacitor with a smaller physical capacitor, thus reducing the size and cost of the required safety capacitor.

[0055] As an optional embodiment, the capacitance parameters corresponding to the injected capacitor are set as injected capacitor parameters, which include at least one of the following: the physical capacitance range corresponding to the application scenario, and the active equivalent capacitance value. The active equivalent capacitance value is determined based on the physical capacitance value of the injected capacitor and the gain coefficient in the gain circuit. In the case of an application scenario including an air conditioning scenario, the corresponding physical capacitance range is 470pF-2.2nF. The gain coefficient is adjusted by the gain circuit, the active equivalent capacitance value is updated, and the frequency of the cancellation signal is adjusted to obtain a signal with a frequency that meets the predetermined conditions. The signal that meets the predetermined conditions is converted into cancellation power parameters and injected into the common connection point. It is then superimposed and canceled with the original noise signal to obtain the target denoised signal. The predetermined condition is that the capacitive reactance generated by the active equivalent capacitance value to the cancellation signal is within a predetermined resistance range.

[0056] In this alternative embodiment, it is explained that the parameter configuration of the injection capacitor not only includes its physical capacitance value, but also introduces the dynamic concept of active equivalent capacitance value, and through the coordinated work with the gain circuit, realizes the intelligent adjustment of the frequency characteristics of the cancellation signal, thereby optimizing the complete process of noise cancellation effect.

[0057] This involves the injection capacitor parameters, which are comprehensive parameter specifications set for the injection capacitor. They include not only its inherent physical capacitance value, but also the system-level dynamic parameter of the active equivalent capacitance value, to describe its actual filtering characteristics in the active loop.

[0058] This involves the active equivalent capacitance value, which is the virtual capacitance value equivalent to the injection point exhibited by the combined action of the entire active cancellation loop and the physical injection capacitor. The value can be determined by the physical capacitance value of the injection capacitor and the gain coefficient in the gain circuit.

[0059] This involves the gain coefficient, which is the amplification factor of the first noise signal by the gain circuit. It is a programmable or adjustable parameter. Adjusting the gain coefficient not only changes the amplitude of the output signal but also directly alters the active equivalent capacitance value, making it one of the core control variables for the system's adaptive adjustment. Specifically, by adjusting the gain parameter, not only can the gain coefficient be adjusted through the gain circuit to change the amplitude of the first noise signal, resulting in a second noise signal with an amplitude within a predetermined range, but the active equivalent capacitance value can also be updated, adjusting the frequency of the cancellation signal to obtain a signal with a frequency that meets predetermined conditions. This signal, meeting the predetermined conditions, is converted into a cancellation current and injected into the common connection point, where it is superimposed and canceled with the original noise signal to obtain the target denoised signal.

[0060] It should be noted that by adjusting the gain parameter, on the one hand, the signal amplification factor is matched with the original noise signals of different amplitudes. For example, if the predetermined amplitude range is 50mV-200mV, the matching standard is that the amplitude of the amplified second noise signal is within the effective range of 50mV-200mV. This allows weak noise signals to be amplified above the lower limit of this range, ensuring that the subsequent signal injection circuit can recognize them; strong noise signals are limited below the upper limit of this range to avoid saturation distortion. On the other hand, the active equivalent capacitance value is updated simultaneously to match the active equivalent capacitance value with the original noise signals of different frequencies. For example, if the target frequency band is 150kHz-3MHz, the matching standard is that the capacitive reactance of the active equivalent capacitance value to the noise signal within the target frequency band (150kHz-3MHz) is within a predetermined resistance range, such as the low resistance range of 1Ω-10kΩ, to ensure that the injection efficiency of the cancellation current is ≥80%. Then, the first noise signal is subjected to gain processing to obtain a second noise signal that meets the subsequent phase compensation requirements.

[0061] This involves a predetermined amplitude range, which is the target range to which the amplitude of the second noise signal needs to be adjusted. This range ensures that the signal is strong enough to drive the subsequent circuit to generate effective cancellation power parameters, but is not so strong that it will cause the signal injection circuit to saturate or become distorted. It is a necessary condition for maintaining linear operation and optimal cancellation effect.

[0062] This involves predetermined conditions, which are optimization targets for the frequency characteristics of the cancellation signal. The target is that the capacitive reactance generated by the active equivalent capacitance to the cancellation signal is within a predetermined resistance range.

[0063] This involves a predetermined resistance range, which is the target range of capacitive reactance designed by the system optimization. This range is usually selected so that the impedance of the injection path matches the impedance of the noise source on the grid side or is in the optimal power transmission state, thereby maximizing the injection efficiency of the power parameters and achieving the best noise cancellation effect.

[0064] This embodiment achieves a significant capacitance multiplication effect. By increasing the gain coefficient through a gain circuit, a small physical capacitor can exhibit the filtering impedance characteristics equivalent to a capacitor with tens or even hundreds of nanofarads. This enables reliance on large, costly safety capacitors, a key technology for miniaturizing and reducing the cost of filters. Furthermore, the system dynamically changes the active equivalent capacitance value by adjusting the gain coefficient in real-time or through preset strategies. This finely adjusts the capacitive reactance of the injection path at different noise frequencies, ensuring that the capacitive reactance remains within the optimal resistance range. This guarantees efficient current injection and noise cancellation at all frequencies, broadening the effective filtering bandwidth.

[0065] As an optional embodiment, when the original mixed signal includes a live wire noise component and a neutral wire noise component, the detection network module includes detection capacitors, namely a first detection capacitor and a second detection capacitor. One end of the first detection capacitor forms the first terminal corresponding to the detection network module, connected to the live wire of the power grid; the other end of the first detection capacitor forms the third terminal corresponding to the detection network module, connected to the first terminal corresponding to the sampling detection circuit. One end of the second detection capacitor forms the second terminal corresponding to the detection network module, connected to the neutral wire of the power grid; the other end of the second detection capacitor forms the fourth terminal corresponding to the detection network module, connected to the second terminal corresponding to the sampling detection circuit. The first detection capacitor is used to collect the live wire noise component relative to a reference point, and the second detection capacitor is used to collect the neutral wire noise component relative to the reference point, where the reference point is the internal common ground point of the active EMI filter.

[0066] In this embodiment, a specific and preferred circuit implementation of the detection network module is described, namely, the noise signals of the live wire and the neutral wire are coupled through the first detection capacitor and the second detection capacitor, respectively, and then transmitted to the subsequent processing circuit.

[0067] This involves a first detection capacitor, which is a discrete capacitor element connected between the live wire of the power grid and the first input terminal of the sampling and detection circuit. Its physical capacitance value is less than a predetermined volume threshold, and it is used to couple the noise voltage on the live wire to the sampling and detection circuit.

[0068] This involves a second detection capacitor, which is a discrete capacitor element connected between the neutral line of the power grid and the second input terminal of the sampling and detection circuit. Its capacitance value and withstand voltage rating can be set to match those of the first detection capacitor, and it is used to couple the high-frequency noise voltage on the neutral line to the sampling and detection circuit.

[0069] This involves the live wire noise component, which is the conducted interference voltage existing on the live wire of the power grid. It is a noise component in the original mixed signal that needs to be suppressed.

[0070] This involves the neutral line noise component, which is the conducted interference voltage existing on the neutral line of the power grid. Together with the live wire noise component, it forms a complete noise loop.

[0071] This involves a reference point, which is a common potential reference set inside the filter. It is usually the internal common ground point of the circuit. The first detection capacitor and the second detection capacitor both use this point as the reference potential, so as to collect the noise voltage of the live wire and the neutral wire relative to this point, respectively.

[0072] This embodiment enables independent and symmetrical acquisition of noise from both wires. By using a first detection capacitor and a second detection capacitor to detect the live wire and neutral wire respectively, noise information on both wires can be acquired simultaneously. This provides the possibility for subsequent differentiation between common-mode and differential-mode noise and more accurate cancellation. Furthermore, the use of the first and second detection capacitors simplifies circuit design and reduces costs. Noise detection can be achieved using only two conventional small-capacity capacitors. The circuit structure is simple, the component cost is low, and the reliability is high, making it easy to implement and mass-produce in products such as air conditioner inverters. Moreover, the dual-channel setup provides richer input information for adaptive noise cancellation. Dual-channel detection allows the system to acquire more complete noise spectrum and phase information, enabling more accurate generation of anti-phase cancellation signals, thereby achieving better noise suppression effects over a wide frequency range.

[0073] As an optional embodiment, it also includes an enable control circuit, wherein the first terminal of the enable control circuit is used to connect to an external control signal source, the second terminal is connected to the enable control terminal of the signal processing module, the third terminal of the enable control circuit is connected to the internal power supply terminal of the filter, and the fourth terminal is connected to the ground line; the enable control circuit is used to receive the enable signal output by the external control signal source, and realize the start and stop control of the filter by controlling the start and stop state of the signal processing module.

[0074] In this optional embodiment, an implementation method is described that adds an enable control circuit to receive external commands to flexibly control the working state of the active EMI filter core processing module.

[0075] This involves an enable control circuit, which is a logic control and drive interface circuit that receives digital or analog control signals from the outside and converts them into internal instructions that can reliably control the power supply or operating mode of the signal processing module.

[0076] This involves an external control signal source, which is a control unit located outside the active EMI filter. It generates corresponding digital levels or PWM signals as enable signals according to the system operating status.

[0077] This involves an enable control terminal, which is a pin or interface on the signal processing module specifically used to receive start / stop control commands. When this terminal is set to an active level by the enable control circuit, the signal processing module starts working; when it is set to an inactive level, the module enters a shutdown or low-power standby state.

[0078] This involves an enable signal, which is a control command issued by an external control signal source and transmitted to the signal processing module through the enable control circuit. It can usually be a preset voltage level.

[0079] This involves the internal power supply terminal of the filter, which is the power supply node inside the filter that provides operating voltage to the signal processing module and other active circuits. The enable control circuit can control the on / off state of this power supply.

[0080] This embodiment enables flexible on-demand operation and energy-saving control. For example, in air conditioning applications, the main control system can control the start and stop of the active filter based on the actual operating status of the compressor and other loads. When the load does not generate strong EMI, the active processing section is shut down, significantly reducing the overall standby power consumption of the system and conforming to the trend of energy-saving and environmentally friendly product design. Furthermore, this setting improves system reliability and extends component lifespan. Enable control can temporarily shut down sensitive signal processing circuits when the filter is powered on or during system malfunctions, preventing damage from voltage instability or surge impacts. Shutting down the active section during long-term non-use periods also reduces circuit heating and aging, extending the lifespan of core components. The externally controllable start / stop mechanism also allows the active filter to function as part of an intelligent power module, accepting unified management from the upper-level system and enabling functions such as system self-testing and fault diagnosis.

[0081] As an optional embodiment, it also includes an AC-DC converter, wherein a first terminal of the AC-DC converter is connected to the live wire after the common connection point; a second terminal of the AC-DC converter is connected to the neutral wire after the common connection point; and a third terminal of the AC-DC converter is connected to the grounding line.

[0082] In this alternative embodiment, an implementation scheme is described that adds an AC-DC converter to convert electrical energy into the DC voltage required for the operation of the active circuitry inside the filter.

[0083] This involves an AC-DC converter, which is a power conversion module that converts AC power into DC power. It typically includes a rectifier bridge, filter capacitors, voltage regulator circuits, etc. The input terminal is connected to the live and neutral wires on the output side of the filter, and the output terminal provides a stable DC operating voltage to the signal processing module and enable control circuit inside the filter.

[0084] This embodiment enables the filter to be self-powered, simplifying system integration. The design makes the active EMI filter an independent, self-powered functional module that only needs to be connected to the AC power grid to operate, eliminating the need for a separate external DC power supply. This significantly simplifies integration and wiring complexity in inverters, especially air conditioning inverters. This setup optimizes the overall power architecture and cost, eliminating the need for a dedicated DC power supply for the EMI filter on the inverter's main control board. It simplifies the power distribution network design and may reduce overall system cost and board layout complexity.

[0085] As an optional embodiment, the signal processing module further includes a temperature compensation module, wherein the first terminal of the temperature compensation module is connected to the internal main control unit of the signal processing module, and the second terminal is connected to the coefficient feedback terminal of the gain circuit; the temperature compensation module is used to collect the ambient temperature and correct the processing parameters of the signal processing module according to the ambient temperature, the processing parameters including the gain coefficient.

[0086] In this alternative embodiment, a method is described that integrates a temperature compensation function within the signal processing module to monitor the ambient temperature in real time and automatically adjust key circuit parameters to ensure stable filter performance across the entire temperature range.

[0087] This includes a temperature compensation module, which is a functional unit that integrates temperature sensing and compensation logic. It senses the ambient temperature of the filter in real time and calculates the correction amount for the signal processing parameters based on the preset temperature and parameter relationship.

[0088] This involves an internal main control unit, which is the core control part of the signal processing module. It can be a microcontroller, digital signal processor, or application-specific integrated circuit. It receives temperature data or compensation instructions from the temperature compensation module and performs corresponding parameter adjustment operations.

[0089] This involves the coefficient feedback terminal of the gain circuit, which is the interface on the gain circuit used to receive external control signals to dynamically adjust its amplification factor. The temperature compensation module applies the correction command calculated based on temperature to the gain circuit through this interface.

[0090] This involves processing parameters, which are adjustable variables that affect the performance of the signal processing module. The core parameters include the gain coefficient, and may also include the filter cutoff frequency, phase compensation parameters, etc. These parameters will change due to the drift of the characteristics of the devices or components in the circuit caused by temperature changes.

[0091] This involves ambient temperature, which is the air temperature around the installation location of the active EMI filter. For air conditioning inverters, the operating temperature range is relatively wide, making it a major environmental factor affecting the performance of electronic components.

[0092] This embodiment ensures performance stability over a wide temperature range. Through real-time temperature monitoring and automatic parameter correction, it can compensate for gain drift and filter characteristic changes caused by temperature variations, maintaining consistent active cancellation performance across the specified wide operating temperature range and meeting higher environmental reliability requirements. Temperature compensation stabilizes key parameters such as the gain coefficient, ensuring that the generated cancellation signal always precisely matches the original noise signal. This avoids insufficient cancellation or overcompensation due to temperature drift, improving the long-term operational reliability of the filter. Furthermore, this compensation mechanism avoids the use of expensive low-temperature drift components, helping to control overall system costs while ensuring performance.

[0093] As an optional embodiment, the capacitance parameters corresponding to the detection capacitor are set as target capacitance parameters, wherein the target capacitance parameters include at least one of the following: capacitance range corresponding to the application scenario, withstand voltage level corresponding to the application scenario, and in the case where the application scenario includes an air conditioning scenario, the corresponding capacitance range is 100pF-4.7nF, and the corresponding withstand voltage level is greater than or equal to 275VAC.

[0094] In this alternative embodiment, specific and critical electrical parameter ranges are set for the detection capacitors constituting the detection network, such as the first detection capacitor and the second detection capacitor, to ensure their performance, safety and reliability in practical applications. The low capacitance values ​​set contribute to the miniaturization of the filter.

[0095] This involves target capacitance parameters, which are a set of performance and safety specifications specifically designed for the test capacitor. The core of these parameters includes the capacitance range and voltage rating, providing clear engineering constraints for capacitor selection.

[0096] This includes the withstand voltage rating, which refers to the maximum voltage that a capacitor can continuously withstand under the premise of long-term safe operation. It is a core indicator of the safety and reliability of a capacitor and must be adapted to the power grid voltage and fluctuation range of the application scenario.

[0097] This embodiment enables accurate and effective high-frequency noise detection. Specifically, in air conditioning applications, a capacitance range of 100pF-4.7nF is specified. The small capacitance value ensures moderate capacitive reactance at high frequencies, efficiently coupling noise signals while blocking interference from power frequency signals, ensuring the purity and signal-to-noise ratio of the acquired signal. With a withstand voltage rating greater than or equal to 275VAC, it adapts to the 220VAC rated voltage of the power grid, reserving approximately 25% safety redundancy to withstand power grid voltage fluctuations, such as ±10%, and instantaneous surges, avoiding the risk of capacitor breakdown. The small capacitance value detection capacitor can adopt an ultra-small package design, with a single capacitor volume less than 1 / 8 of that of traditional large capacitance value detection capacitors, significantly reducing the volume ratio of the detection network module and achieving miniaturization. In air conditioning applications, it is perfectly suited to the limited installation space of air conditioning outdoor units.

[0098] As an optional embodiment, the inductance parameters corresponding to the common-mode inductor are set as target inductance parameters, wherein the target inductance parameters include: the inductance range in the corresponding application scenario. In the case where the application scenario includes an air conditioning scenario, the corresponding inductance range is 100uH-900uH.

[0099] In this alternative embodiment, the common-mode inductors of the pre-stage and post-stage are configured with an optimized small inductance range to achieve filter miniaturization and high reliability.

[0100] This involves the target inductance parameters, which are performance specifications specifically designed for the common-mode inductor used in the active EMI filter of this application, and are different from those of traditional passive solutions. The core of these specifications is the inductance range.

[0101] This embodiment optimizes parameters for common-mode inductors in specific application scenarios. In air conditioning applications, the common-mode inductance is reduced from the mH range of traditional solutions to 100uH-900uH. Based on the approximate proportionality between inductor volume and inductance, this directly reduces the core size, number of coil turns, and amount of copper used. The smaller inductance design significantly lowers the ampere-turns required at rated operating current, and the core operating point is further away from the saturation region, extending the filter's operating temperature range and reliability. Moreover, this inductance range design allows the common-mode inductor to primarily suppress higher-frequency, larger-amplitude noise components, while the active module focuses on dynamically and accurately canceling noise in the main frequency bands. Their clear division of labor and complementary functions work together to create a wide-bandwidth, high-suppression hybrid filtering performance, reducing material costs and power consumption.

[0102] For example, the 100uH-900uH inductor range precisely matches the common-mode noise band of 150kHz-3MHz in air conditioning scenarios. According to the inductor impedance formula Z=2πfL, where f is the noise frequency and L is the inductance value, when the noise frequency is 150kHz, the impedance of a 100uH inductor is approximately 94Ω and that of a 900uH inductor is approximately 848Ω, effectively blocking low-frequency common-mode noise. When the noise frequency rises to 3MHz, the impedance of a 100uH inductor is approximately 1885Ω and that of a 900uH inductor is approximately 16965Ω, strongly suppressing high-frequency common-mode noise. This achieves preliminary filtering of common-mode noise across the entire target frequency band, reducing the processing burden on subsequent active cancellation modules and improving overall filtering efficiency. Meanwhile, this inductance range is compatible with the rated current of variable frequency air conditioners, and the selected common-mode inductor can match the corresponding rated current specification, avoiding magnetic saturation problems caused by insufficient rated current of the inductor, ensuring stable operation under complex conditions such as full load operation, start-up and shutdown of the air conditioner. At the same time, the common-mode inductor in this parameter range does not need to use an ultra-large magnetic core, and the magnetic core volume can be controlled within 20mm×15mm×10mm, which can realize the miniaturization design of the entire filter.

[0103] As an optional embodiment, the sampling and detection circuit includes a detection filtering unit, and the filtering parameters corresponding to the detection filtering unit are set as target filtering parameters. The target filtering parameters include the effective operating frequency band range of the bandpass filter in the corresponding application scenario. In the case that the application scenario includes an air conditioning scenario, the corresponding effective operating frequency band range is 150kHz-3MHz, so as to filter out the first noise signal in the original noise signal within the corresponding effective operating frequency band range.

[0104] In this embodiment, the key parameter settings of the detection filter unit of the sampling detection circuit are described, that is, it is designed as a bandpass filter with a specific passband, specifically used to extract noise signals in the target frequency band.

[0105] This involves a detection filtering unit, which is a signal conditioning part integrated inside the sampling and detection circuit. It can typically be composed of operational amplifiers, resistors, capacitors, etc., forming an active filter circuit. Its function is to perform frequency filtering on the raw mixed signal input from the detection network.

[0106] This involves the target filtering parameters, which are a set of key parameters set for the detection filtering unit that determine its frequency response characteristics. Here, it refers to the effective operating frequency band range of its bandpass filter.

[0107] This involves bandpass filtering, a signal processing technique that allows signals within a specific frequency range to pass through while significantly attenuating frequency components outside the passband.

[0108] This embodiment enables high-precision, high signal-to-noise ratio noise extraction. In air conditioning applications, by setting the detection filter unit within the 150kHz-3MHz bandpass range, it effectively filters out strong 50Hz / 60Hz power frequency signals and their low-order harmonics, preventing them from drowning out weak MHz-level high-frequency noise. It also suppresses non-critical high-frequency components above 3MHz, significantly improving the signal-to-noise ratio of the output signal. The system samples, amplifies, and inversely cancels noise within the 150kHz-3MHz range, concentrating limited circuit resources and processing power on the frequency band most influential on EMC test results. This avoids energy dispersion, achieving deeper and more precise noise suppression within this critical frequency band, thus improving the filter's measured performance.

[0109] Based on the above embodiments and optional embodiments, an optional implementation method is provided for use in air conditioning scenarios, which is described in detail below.

[0110] In current household air conditioner inverters, traditional passive EMI filters are commonly used. These filters, such as multi-stage π-type filter networks composed of large-capacitance common-mode inductors, X capacitors, and Y capacitors, are relatively large in size and weight. The common-mode inductor and its core material result in a single filter weighing over 200 grams, severely restricting miniaturization design. In terms of electrical performance, the insertion loss in the critical 150kHz-3MHz frequency band is only 20-35dB, failing to meet the stringent requirements of modern EMC standards. More seriously, when the ambient temperature exceeds 85℃, the ferrite core easily saturates, causing a sharp drop in inductance and a significant deterioration in filtering performance. Furthermore, fixed-parameter designs cannot adapt to the dynamic changes in the EMI spectrum during compressor speed changes, and transient interference caused by sudden load changes cannot be effectively suppressed. In terms of economy, the cost of high-performance core materials is too high, and multi-stage filter networks further increase production costs and maintenance complexity. Therefore, at least the following problems exist in these technologies:

[0111] 1) Excessive size and weight: The common mode inductor and matching magnetic core materials cause the weight of a single filter to exceed 200 grams, which seriously restricts the miniaturization design of air conditioner inverters;

[0112] 2) Insufficient filtering performance: The insertion loss is only 20-35dB in the 150kHz-3MHz range (critical frequency band for EMI suppression), which is difficult to meet the stringent modern EMC standards;

[0113] 3) Poor high-temperature stability: When the ambient temperature exceeds 85℃, the ferrite core is prone to saturation, which leads to a sharp drop in inductance and a significant deterioration in the filtering effect;

[0114] 4) Unable to adapt to dynamic interference: Fixed parameter design cannot match the EMI spectrum changes when the compressor is running at variable speed, and instantaneous interference caused by sudden load changes cannot be effectively suppressed.

[0115] In view of this, an active electromagnetic interference (EMI) filter is provided in an optional embodiment of the present invention to solve the above problems. Figure 2 is a schematic diagram of the structure of the active EMI filter provided in an optional embodiment of the present invention. As shown in Figure 2, it will be described below.

[0116] An optional embodiment of the present invention provides an active EMI filter for a household air conditioner inverter, which includes a detection network module, a signal processing module, an injection network module, a common-mode inductor, and an AC-DC converter to form the filter shown in Figure 2. The detection network module includes a detection capacitor, the signal processing module includes a sampling detection circuit, a gain circuit, and a signal injection circuit, the injection network module includes an injection capacitor, and the common-mode inductor includes a front-stage common-mode inductor and a rear-stage common-mode inductor.

[0117] Optionally, the detection network module uses a detection capacitor bank to collect power line noise, the EMI processing module integrates a capacitance multiplier and signal processing functions, and the injection network feeds back the canceling current to the power line through the injection capacitor.

[0118] Optionally, common-mode inductors for both the preamp and power amp stages, with inductance ranging from 100uH to 900uH.

[0119] Optionally, the detection network includes two sets of detection capacitors Csen1 (same as the first detection capacitor mentioned above) and Csen2 (same as the second detection capacitor mentioned above), which are respectively connected between the live wire and the neutral wire and the detection input terminal of the EMI processing module, with a capacitance range of 100pF-4.7nF and a withstand voltage rating of not less than 275VAC.

[0120] Optionally, the injection network module includes an injection capacitor Cinj, connected between the output of the EMI processing module and the power line, with a capacitance range of 470pF-2.2nF, which, together with the gain coefficient in the gain circuit, sets the effective active equivalent capacitance value.

[0121] Optionally, the sampling and detection circuit includes a detection filtering unit, the effective operating frequency band of which is 150kHz-3MHz, includes bandpass filtering function, and has power frequency signal suppression capability.

[0122] Optionally, the control circuit can also be enabled to support the start / stop of the filter and the switching of low-power modes by external signals.

[0123] Optionally, it also includes a temperature compensation function, which automatically corrects the processing parameters according to the ambient temperature.

[0124] By configuring the aforementioned filters, a unique three-stage signal processing architecture is employed, constructing a complete closed-loop control system through a detection network, signal processing module, and injection network. The signal processing module is further divided into three functionally distinct and collaborative processing stages: a detection and filtering stage, a gain stage, and an injection stage. The detection and filtering stage is responsible for accurately extracting effective noise signals; the gain stage integrates programmable gain amplification and capacitance multiplication functions; and the injection stage ensures the effective injection of cancellation signals. Voltage detection and current injection technologies are employed, along with innovative capacitance multiplication technology, achieving the filtering effect of a large-capacity capacitor with a smaller physical capacitor. The system incorporates an adaptive control algorithm that can analyze noise characteristics in real time and automatically optimize processing parameters, while also integrating a comprehensive protection mechanism.

[0125] The above settings can reduce the volume of the common-mode inductor by 60-80% and the overall weight by 50-70%; achieve noise suppression of more than 30dB in the key frequency band of 150kHz-3MHz, and improve insertion loss at each frequency by 15-25dB; the system response time is less than 100 microseconds, enabling real-time tracking of load changes; the operating temperature range is extended to -40℃ to +105℃, significantly improving reliability; and the overall system cost is reduced by 30-50%, demonstrating excellent economic efficiency and market competitiveness.

[0126] With the above setup, a three-stage signal processing module is installed at the power input of the frequency converter, dividing the EMI filtering system into three parts: the detection network module, the signal processing module, and the injection network module. The detection network module is located at the front end of the power input and collects high-frequency noise on the live and neutral wires through two sets of detection capacitors. The signal processing module is located after the detection network. The injection network is connected between the output of the processing module and the power line.

[0127] The following describes a more specific implementation method, dividing the active EMI filter into several parts and introducing each part separately:

[0128] (a) Detection Network:

[0129] Two sets of detection capacitors (Csen1, Csen2, capacitance 100pF-4.7nF, withstand voltage ≥275VAC) are used to replace the traditional inductor-based detection method, accurately collecting high-frequency noise from the live and neutral wires while avoiding interference with the 50Hz power frequency signal.

[0130] Optionally, the detection network can use two sets of 470pF C0G capacitors with a voltage rating of 275VAC, which are directly connected to the live and neutral input ports respectively.

[0131] (II) Signal Processing Module:

[0132] Compared to the traditional single filter circuit, it is divided into three circuits.

[0133] 1) The sampling and detection circuit involves detection and filtering stage processing. Through bandpass filtering design, the effective operating frequency band is 150kHz-3MHz, while also having the ability to suppress power frequency signals (50Hz) and accurately extract effective noise.

[0134] Optionally, the detection filter stage can employ a fourth-order active filter architecture with a bandpass characteristic of 150kHz-3MHz.

[0135] 2) Gain circuit, which involves gain stage processing, can dynamically adjust the signal amplification factor (gain range 20-60dB) by integrating programmable gain amplification and capacitance multiplication technology.

[0136] Optionally, the gain circuit may include a programmable gain amplifier and a capacitor multiplier circuit.

[0137] 3) The signal injection circuit involves injection stage processing and adopts an AB class power amplifier design to ensure effective driving of the canceled signal.

[0138] Alternatively, the injection circuit can be designed using a Class AB power amplifier.

[0139] (iii) Injection into the network:

[0140] By replacing traditional passive components with injection capacitors (Cinj, capacitance 470pF-2.2nF), the processed cancellation current is fed back to the power line to achieve vector cancellation with the original noise.

[0141] Alternatively, a 4.7nFC0G capacitor with an equivalent series resistance of less than 10mΩ can be used.

[0142] Optionally, auxiliary components may also be provided, which may include a 470μH aluminum wire common mode inductor and a 0.47μF Class X safety capacitor.

[0143] It should be noted that, regarding parameter settings, the capacitance range of the detection capacitor is limited to 100pF-4.7nF. This setting ensures effective detection of high-frequency noise above 150kHz while avoiding interference with 50Hz power frequency signals. The capacitance range of the injection capacitor is set to 470pF-2.2nF. This range, in conjunction with the capacitance multiplication function of the gain stage, can effectively achieve a filtering capacitor effect of 10-100nF. The gain range of the gain stage is set to be adjustable from 20-60dB, achieving precise control through an external resistor network.

[0144] With the above setup, when the frequency converter is operating, the high-frequency noise generated by the power switching devices is collected by the detection capacitor and enters the detection and filtering stage. The detection and filtering stage first filters out the 50Hz power frequency interference, and then extracts the effective noise signal from 150kHz to 30MHz. These signals then enter the gain stage, where they are amplified by a programmable gain amplifier, and a corresponding inverse cancellation signal is generated using capacitance multiplication technology. Finally, the injection stage amplifies the power of the cancellation signal and feeds it back to the power line through the injection capacitor, achieving vector cancellation with the original noise signal.

[0145] Through experimental verification and analysis, based on experimental data from household air conditioner inverters with rated power ranging from 1.5KW to 2.2KW, when the capacitance of the detection capacitor is 470pF and the capacitance of the injection capacitor is 4.7nF, the system achieves an insertion loss of 45dB at 150kHz and 55dB at 500kHz, fully meeting the limits of the CISPR32 standard. Experimental results show that the system's adaptive adjustment time under this configuration is less than 100μs, enabling real-time tracking of compressor load changes.

[0146] Furthermore, considering the application requirements of inverters with different power levels, the capacitance values ​​of the test capacitor and the injection capacitor need to be precisely matched. Taking inverters with rated power ranging from 1.5kW to 2.2kW as the experimental object, when the capacitance value of the test capacitor is 470pF and the capacitance values ​​of the injection capacitors are 470pF, 4.7nF, and 2.2nF respectively, the insertion loss test results at a frequency of 150kHz are obtained. The results show that when the capacitance value of the injection capacitor is 4.7nF, it can ensure sufficient noise suppression effect while avoiding system stability problems caused by excessive capacitance.

[0147] To ensure system reliability, the withstand voltage ratings of the test capacitor and injection capacitor must be strictly limited. Considering mains voltage fluctuations and surge impacts, the capacitor withstand voltage rating is set to no less than 275VAC, which ensures stable operation even at a mains voltage of 264VAC.

[0148] As can be seen, through the above optional embodiments, the method provided by the optional embodiments of the present invention can solve the above-mentioned technical problems and achieve the corresponding beneficial effects through the following technical means:

[0149] 1) Capacitor multiplication technology: Through the algorithm and circuit design of the signal processing module, the filtering effect of a 10-100nF large-capacity capacitor is achieved by using a small physical capacitor (such as a 470pF detection capacitor and a 4.7nF injection capacitor), avoiding the use of traditional large-volume capacitors and solving the problem mentioned in 1) above.

[0150] 2) Small-volume common-mode inductor design: The common-mode inductance is reduced to 100uH-900uH (only 1 / 5-1 / 30 of the traditional), which greatly reduces the amount of magnetic core material used. Ultimately, the common-mode inductor volume is reduced by 60-80% and the overall filter weight is reduced by 50-70%. This breaks through the constraints of traditional solutions on miniaturization design. Combined with architecture optimization, the volume is greatly reduced, solving the problem mentioned in 1) above.

[0151] 3) Three-stage precision signal processing architecture: The detection and filtering stage is responsible for accurately extracting the effective noise signal. It adopts a bandpass filter design, accurately locks the effective operating frequency band to 150kHz-3MHz, and has the ability to suppress power frequency signals, thus accurately extracting the effective noise; The gain stage integrates programmable gain amplification and capacitance multiplication functions, and enhances noise signal processing through 20-60dB programmable gain amplification; The injection stage ensures the effective injection of the cancellation signal. It adopts a Class AB power amplifier to ensure that the cancellation signal is efficiently injected into the power line, realizing vector cancellation between the original noise and the cancellation signal, improving the insertion loss of the key frequency band to more than 30dB, which is 15-25dB higher than the traditional solution, and solving the problem mentioned in 2) above.

[0152] 4) Temperature compensation and active architecture optimization: On the one hand, it integrates temperature compensation function, which can automatically correct processing parameters according to ambient temperature to offset the impact of temperature changes on circuit performance; on the other hand, it adopts an active filtering architecture, which relies on the collaborative work of signal processing algorithms and electronic components to significantly reduce the performance dependence on traditional ferrite cores, avoid core saturation problems at high temperatures, and extend the operating temperature range to -40℃ to +105℃, thus solving the problem mentioned in 3) above.

[0153] 5) Adaptive control algorithm: The built-in real-time analysis module can accurately capture the dynamic changes of EMI spectrum and instantaneous interference caused by load changes during compressor speed change operation, automatically optimize gain parameters, capacitance multiplication factor and phase compensation parameters, and the system response time is <100μs. It realizes real-time tracking and suppression of dynamic interference. That is, through the adaptive control algorithm, it can analyze noise characteristics in real time and automatically optimize processing parameters. At the same time, it integrates a complete protection mechanism to solve the problem mentioned in 4) above.

[0154] 6) The inverters manufactured by the optional embodiments of the present invention reduce the volume of the common-mode inductor by 60-80% and the overall weight by 50-70%; achieve noise suppression of more than 30dB in the key frequency band of 150kHz-3MHz, and improve the insertion loss at each frequency point by 15-25dB; the system response time is less than 100 microseconds, and it can track load changes in real time; the operating temperature range is extended to -40℃ to +105℃, and the reliability is significantly improved; the overall system cost is reduced by 30-50%, and it has excellent economic efficiency and market competitiveness.

[0155] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0156] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0157] Example 2

[0158] According to another aspect of the present invention, a frequency converter is also provided, including an active EMI filter and a rectifier bridge as described above. The input terminal of the active EMI filter serves as the external power grid interface of the frequency converter, and the output terminal of the active EMI filter is connected to the input terminal of the rectifier bridge. The external power grid interface represents the interface of the frequency converter for connecting to the external power grid, which is used to realize the power connection between the frequency converter and the external power grid. The corresponding input terminal includes a first terminal and a second terminal corresponding to the detection network module, and the corresponding output terminal includes a live wire output terminal and a neutral wire output terminal after the common connection point.

[0159] Example 3

[0160] According to another aspect of the present invention, an air conditioning system is also provided, including an air conditioning body and an inverter as described above located within the air conditioning body.

[0161] Example 4

[0162] According to an embodiment of the present invention, an embodiment of an active electromagnetic interference (EMI) filter method is also provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0163] Figure 3 is a flowchart of an active electromagnetic interference (EMI) filter method according to an embodiment of the present invention. As shown in Figure 3, the method includes the following steps:

[0164] Step S302: Control the detection network module to collect the original mixed signal between the live wire and the neutral wire in the power grid, wherein the original mixed signal includes the original noise signal;

[0165] In step S302 of this application, the noise cancellation process of the active EMI filter is initiated. First, the control detection network module is directly connected to the live and neutral wires of the AC power grid to sense and acquire the electrical signals on the line in real time. This signal is a raw electrical signal without any processing, containing the power frequency voltage and current components of the power grid as well as high-frequency electromagnetic interference components generated by the downstream load.

[0166] This step completes the signal sensing for the active cancellation loop. It provides the initial and most authentic input signal source for the entire noise cancellation system, ensuring that all subsequent processing, analysis, and cancellation actions are based on the actual noise conditions present on the power grid. This is the prerequisite and foundation for achieving accurate and dynamic noise suppression. If the signal acquired in this step is distorted or contains irrelevant interference, it will directly affect the accuracy of subsequent stages, ultimately leading to poor cancellation results.

[0167] Step S304: Control the sampling and detection circuit to filter the original mixed signal to obtain the first noise signal;

[0168] In step S304 of this application, the raw mixed signal acquired in step S302 is sent to the sampling and detection circuit for processing. The core function of this circuit is to perform frequency filtering. Through its internally integrated detection and filtering unit, the raw mixed signal containing strong power frequency components and out-of-band clutter is converted into a purer signal containing only the target frequency band components.

[0169] This step completes the crucial preprocessing and purification of the noise signal. It focuses the massive and chaotic raw signal onto the core noise frequency band critical for EMC compliance, significantly improving the signal-to-noise ratio. This prevents the powerful power frequency signal from drowning out the weak MHz-level noise and avoids irrelevant frequency interference from misleading subsequent processing. This ensures that subsequent gain, inversion, and injection stages are based on accurate and effective noise information, forming the foundation for the entire active cancellation loop to achieve precise and efficient suppression.

[0170] Step S306: The control gain circuit adjusts the corresponding gain coefficient through the gain adjustment element according to the amplitude of the first noise signal, and performs gain processing on the first noise signal with the adjusted gain coefficient to obtain a second noise signal with the corresponding amplitude within the predetermined amplitude range.

[0171] In step S306 of this application, the first noise signal, which has been focused on the target frequency band and output from step S304, is input to the gain circuit. The gain circuit linearly amplifies and conditions the signal based on a dynamically adjusted gain coefficient, outputting a second noise signal with an amplitude suitable for subsequently generating a cancellation signal. This process not only adjusts the signal amplitude but also provides a crucial control dimension for achieving the capacitance multiplication effect.

[0172] This involves gain processing, which refers to the amplitude amplification operation performed by the gain circuit on the input first noise signal. The amplification factor of this operation is determined by the gain coefficient, and its purpose is to amplify the weak, filtered noise signal to a suitable level so that subsequent circuits can generate a sufficiently strong cancellation signal based on it.

[0173] This step enables the amplitude enhancement and controllable adjustment of the target noise signal. It boosts the weak noise signal extracted from the previous stage to a suitable processing level, providing the necessary amplitude basis for generating effective cancellation power parameters. By adjusting the gain coefficient of the gain circuit, not only can the strength of the cancellation signal be controlled, but the active equivalent capacitance value of the entire system can also be dynamically changed, thus achieving a capacitance multiplication innovation by using a small physical capacitor to achieve the filtering effect of a large capacitor.

[0174] Step S308: The control signal injection circuit obtains a cancellation signal with opposite phase and matching amplitude to the original noise signal based on the amplitude and phase of the second noise signal.

[0175] In step S308 of this application, the second noise signal output in step S306 is sent to the signal injection circuit. It accurately analyzes the real-time amplitude and phase information of the second noise signal and generates a new signal, namely the cancellation signal, based on this. The new signal has the same or proportional amplitude as the detected original noise signal, but is exactly 180 degrees out of phase, so as to cancel the original noise signal.

[0176] This involves the amplitude and phase of the second noise signal. The amplitude of the second noise signal characterizes the intensity information of the target noise after extraction and amplification by the previous stage; its phase reflects the waveform position of the noise signal at a specific moment. The signal injection circuit needs to accurately acquire these two pieces of information as a reference for generating the cancellation signal.

[0177] This involves phase reversal, which means that the waveform of the signal introduced into the power grid for cancellation is exactly half a cycle off from the waveform of the original noise signal on the line. When two signals with the same frequency and equal amplitude but opposite phase are superimposed, their instantaneous values ​​will cancel each other out, and the total amplitude will tend to zero. This is the fundamental physical principle of noise cancellation.

[0178] This involves amplitude matching, which refers to controlling the amplitude of the generated cancellation signal to be equal to or at a fixed, optimized ratio to the amplitude of the original noise signal on the line. If the amplitude of the cancellation signal is too small, the cancellation will be incomplete; if it is too large, overcompensation may occur, introducing new interference. Precise amplitude matching is a necessary condition for achieving the best cancellation effect.

[0179] This step transforms the passive noise detection and analysis by the pre-amplifier circuit into the active generation of a cancellation signal for precise countermeasure. By ensuring that the cancellation signal is strictly out of phase and amplitude matched with the original noise signal, the next step of effectively injecting the cancellation signal in the form of electrical energy into the power grid and achieving physical noise cancellation is achieved.

[0180] In step S310, the control injection network module obtains the cancellation power parameters injected to the common connection point based on the cancellation signal, so as to cancel the original noise signal and obtain the target denoised signal.

[0181] In step S310 of this application, the control injection network module receives and processes the cancellation signal generated by the signal injection circuit. The core function of the injection network module is to efficiently convert this voltage-form cancellation signal into actual cancellation power parameters that can be injected into the power grid, and to accurately inject this current into the point of common coupling of the power grid. At this point, the injected cancellation power parameters are vector-superimposed with the original noise signal on the line. Since the two have the same frequency, matched amplitude, and opposite phase, the result of the superposition is that the noise energy is mutually canceled, thereby obtaining a target denoising signal with a significantly reduced noise level after the point of common coupling, completing the entire active noise cancellation process.

[0182] Through steps S302-S310, by employing a combination of small-value predetermined capacitors and dynamic gain control, the goal of significantly reducing the filter size while ensuring the accuracy of targeted noise signal suppression is achieved. This realizes the technical effect of bidirectional optimization of filter miniaturization and high noise filtering accuracy, thereby solving the technical problem in related technologies where it is difficult to balance filter size and noise filtering accuracy when processing noise signals.

[0183] Example 5

[0184] According to another aspect of the present invention, an electronic device is also provided, comprising: a processor; and a memory for storing processor-executable instructions, wherein the processor is configured to execute instructions to implement the active electromagnetic interference (EMI) filter method of any of the above embodiments.

[0185] Example 6

[0186] According to another aspect of the present invention, a computer-readable storage medium is also provided, which, when the instructions in the computer-readable storage medium are executed by a processor of an electronic device, enables the electronic device to perform any of the above-described active electromagnetic interference (EMI) filter methods.

[0187] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0188] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0189] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0190] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0191] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0192] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0193] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An active electromagnetic interference (EMI) filter, characterized in that, include: The system includes a detection network module, a signal processing module, and an injection network module. The signal processing module comprises a sampling detection circuit, a gain circuit, and a signal injection circuit. The gain circuit includes a gain adjustment element. The volume of a predetermined capacitor in the filter is less than a predetermined volume threshold. The predetermined capacitor includes at least one of the following: a detection capacitor included in the detection network module; an injection capacitor included in the injection network module; a first terminal of the detection network module connected to the live wire of the power grid; a second terminal connected to the neutral wire of the power grid; a third terminal connected to the first terminal of the sampling detection circuit; a fourth terminal connected to the second terminal of the sampling detection circuit; a third terminal of the sampling detection circuit connected to the first terminal of the gain circuit; a second terminal of the gain circuit connected to the first terminal of the signal injection circuit; a second terminal of the signal injection circuit connected to the first terminal of the injection network module; and a second terminal of the injection network module connected to a common connection point, wherein the common connection point is the common connection point between the live wire and the neutral wire.

2. The filter according to claim 1, characterized in that, It also includes a common-mode inductor, which includes a pre-stage common-mode inductor and a post-stage common-mode inductor. The first terminal of the pre-stage common-mode inductor is connected to the live wire of the external power grid, the second terminal is connected to the neutral wire of the external power grid, the third terminal is connected to the first terminal of the detection network module, and the fourth terminal is connected to the second terminal of the detection network module. The first terminal of the post-stage common-mode inductor is connected to the live wire after the common connection point, the second terminal is connected to the neutral wire after the common connection point, the third terminal of the post-stage common-mode inductor constitutes the live wire output terminal, and the fourth terminal of the post-stage common-mode inductor constitutes the neutral wire output terminal.

3. The filter according to claim 1, characterized in that, The injection network module includes an injection capacitor, wherein one end of the injection capacitor forms a first terminal corresponding to the injection network module and is connected to a second terminal corresponding to the signal injection circuit, and the other end of the injection capacitor forms a second terminal corresponding to the injection network module and is connected to the common connection point. The injection capacitor is used to receive the cancellation signal, obtain the cancellation power parameter, and inject the cancellation power parameter into the common connection point to cancel the original noise signal and obtain the target denoised signal.

4. The filter according to claim 3, characterized in that, The capacitance parameters corresponding to the injected capacitor are set as injection capacitor parameters, wherein the injection capacitor parameters include at least one of the following: the physical capacitance range corresponding to the application scenario, and the active equivalent capacitance value. The active equivalent capacitance value is determined based on the physical capacitance value of the injected capacitor and the gain coefficient in the gain circuit. In the case where the application scenario includes an air conditioning scenario, the corresponding physical capacitance range is 470pF-2.2nF. The gain coefficient is adjusted by the gain circuit, the active equivalent capacitance value is updated, and the frequency of the cancellation signal is adjusted to obtain a signal with a frequency that meets a predetermined condition. The signal that meets the predetermined condition is converted into a cancellation power parameter and injected into the common connection point. It is then superimposed and canceled with the original noise signal to obtain the target denoised signal. The predetermined condition is that the capacitive reactance generated by the active equivalent capacitance value to the cancellation signal is within a predetermined resistance range.

5. The filter according to claim 1, characterized in that, The detection network module includes detection capacitors, specifically a first detection capacitor and a second detection capacitor. One end of the first detection capacitor forms the first terminal of the detection network module, connected to the live wire of the power grid, and the other end forms the third terminal of the detection network module, connected to the first terminal of the sampling detection circuit. One end of the second detection capacitor forms the second terminal of the detection network module, connected to the neutral wire of the power grid, and the other end forms the fourth terminal of the detection network module, connected to the second terminal of the sampling detection circuit. The first detection capacitor is used to collect the live wire noise component relative to a reference point, and the second detection capacitor is used to collect the neutral wire noise component relative to a reference point. The reference point is the internal common ground point of the active EMI filter.

6. The filter according to claim 1, characterized in that, It also includes an enable control circuit, wherein the first terminal of the enable control circuit is used to connect to an external control signal source, the second terminal is connected to the enable control terminal of the signal processing module, the third terminal of the enable control circuit is connected to the internal power supply terminal of the filter, and the fourth terminal is connected to the ground line; the enable control circuit is used to receive the enable signal output by the external control signal source, and to control the start and stop state of the signal processing module to realize the start and stop control of the filter.

7. The filter according to claim 1, characterized in that, It also includes an AC-DC converter, wherein the first terminal of the AC-DC converter is connected to the live wire after the common connection point, the second terminal of the AC-DC converter is connected to the neutral wire after the common connection point, and the third terminal of the AC-DC converter is connected to the grounding line.

8. The filter according to claim 1, characterized in that, The signal processing module further includes a temperature compensation module, wherein the first terminal of the temperature compensation module is connected to the internal main control unit of the signal processing module, and the second terminal is connected to the coefficient feedback terminal of the gain circuit. The temperature compensation module is used to collect the ambient temperature and correct the processing parameters of the signal processing module according to the ambient temperature. The processing parameters include the gain coefficient.

9. The filter according to claim 1, characterized in that, The capacitance parameters corresponding to the detection capacitor are set as target capacitance parameters, wherein the target capacitance parameters include at least one of the following: capacitance range in the corresponding application scenario, withstand voltage rating in the corresponding application scenario, and in the case where the application scenario includes an air conditioning scenario, the corresponding capacitance range is 100pF-4.7nF, and the corresponding withstand voltage rating is greater than or equal to 275VAC.

10. The filter according to claim 2, characterized in that, The inductance parameters corresponding to the common-mode inductor are set as target inductance parameters, wherein the target inductance parameters include: the inductance range in the corresponding application scenario. In the case where the application scenario includes an air conditioning scenario, the corresponding inductance range is 100uH-900uH.

11. The filter according to any one of claims 1 to 10, characterized in that, The sampling and detection circuit includes a detection and filtering unit. The filtering parameters corresponding to the detection and filtering unit are set as target filtering parameters. The target filtering parameters include the effective operating frequency band range of the bandpass filter in the corresponding application scenario. In the case that the application scenario includes an air conditioning scenario, the corresponding effective operating frequency band range is 150kHz-3MHz, so as to filter out the first noise signal in the original noise signal within the corresponding effective operating frequency band range.

12. A frequency converter, characterized in that, The system includes an active EMI filter and a rectifier bridge as described in any one of claims 1 to 11, wherein the input terminal of the active EMI filter serves as the external power grid interface of the frequency converter, the output terminal of the active EMI filter is connected to the input terminal of the rectifier bridge, the external power grid interface represents the interface of the frequency converter for connecting to the external power grid, and is used to realize the power connection between the frequency converter and the external power grid, the corresponding input terminal includes the first terminal and the second terminal corresponding to the detection network module, and the corresponding output terminal includes the live wire output terminal and the neutral wire output terminal after the common connection point.

13. An air conditioning system, characterized in that, Includes an air conditioner body, and a frequency converter as described in claim 12 is located within the air conditioner body.

14. A noise cancellation method based on an active EMI filter according to any one of claims 1 to 11, characterized in that, include: The control and detection network module collects the raw mixed signal between the live wire and the neutral wire in the power grid, wherein the raw mixed signal includes the raw noise signal; The control sampling and detection circuit filters the original mixed signal to obtain a first noise signal; the control gain circuit adjusts the corresponding gain coefficient through the gain adjustment element according to the amplitude of the first noise signal, and performs gain processing on the first noise signal with the adjusted gain coefficient to obtain a second noise signal with the corresponding amplitude within a predetermined amplitude range; the control signal injection circuit obtains a cancellation signal with opposite phase and matching amplitude to the original noise signal according to the amplitude and phase of the second noise signal; the control injection network module obtains the cancellation power parameters injected to the common connection point according to the cancellation signal to cancel the original noise signal and obtain the target denoised signal.

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