Active EMI filtering device based on Rogowski coil non-contact current sensing

Abstract

The invention relates to an active EMI filtering device and power system based on Rogowski coil non-contact current sensing. The active EMI filtering device comprises a Rogowski coil module, a detection module, an error amplification module and a compensation injection module. A Rogowski coil of the Rogowski coil module surrounds the grounding conductor; the detection module is connected with the Rogowski coil module; the input end of the error amplification module is connected with the detection module, the output end of the error amplification module is connected with the compensation injection module, and the compensation injection module is grounded; the Rogowski coil module is used for detecting common-mode leakage current flowing through a grounding loop through a Rogowski coil and outputting detection voltage; the detection module is used for receiving the detection voltage; the error amplification module is used for applying a target gain to the voltage output by the detection module and outputting the voltage after the gain is applied; the compensation injection module is used for generating compensation current according to the voltage after the gain is applied and outputting the compensation current to a grounding loop; therefore, the injection of the compensation current is realized, and the common-mode leakage current is inhibited.

Description

Technical Field

[0001] This application relates to the field of electromagnetic compatibility technology, and in particular to an active EMI filter device based on Rogowski coil non-contact current sensing. Background Technology

[0002] With the advancement of global energy transition and carbon neutrality goals, power electronics technology has experienced unprecedented rapid development in fields such as new energy vehicles, industrial automation, rail transportation, wind power generation, and photovoltaic grid connection. Particularly in the electric vehicle sector, with the widespread adoption of high-voltage platforms and the extensive use of third-generation semiconductor devices such as SiC (silicon carbide), high-power inverter systems are evolving towards higher switching frequencies and higher power densities. While this technological evolution brings improvements in system efficiency, it also makes electromagnetic compatibility issues increasingly prominent, becoming a key factor restricting system performance and reliability. Summary of the Invention

[0003] Therefore, it is necessary to provide an active EMI filter and power system based on Rogowski coil non-contact current sensing.

[0004] In a first aspect, embodiments of this application provide an active EMI filter based on Rogowski coil non-contact current sensing, comprising a Rogowski coil module, a detection module, an error amplification module, and a compensation injection module; the Rogowski coil of the Rogowski coil module is wound around a grounded conductor; the detection module is connected to the Rogowski coil module; the input terminal of the error amplification module is connected to the detection module, the output terminal of the error amplification module is connected to the compensation injection module, and the compensation injection module is grounded;

[0005] The Rogowski coil module is used to detect the common-mode leakage current flowing through the grounding loop via the Rogowski coil and output a detection voltage.

[0006] The detection module is used to receive the detection voltage;

[0007] The error amplification module is used to apply a target gain to the voltage output by the detection module and output the voltage after applying the gain.

[0008] The compensation injection module is used to generate a compensation current based on the voltage after the applied gain is applied, and output the compensation current to the grounding circuit.

[0009] In one embodiment, the error amplification module includes an error amplifier, a first gain unit, a second gain unit, and a power amplifier unit;

[0010] The input terminal of the first gain unit is connected to the first terminal of the detection module, the first output terminal of the first gain unit is connected to the first input terminal of the error amplifier, and the second output terminal of the first gain unit is grounded.

[0011] The input terminal of the second gain unit is connected to the second terminal of the detection module, and the first output terminal of the second gain unit is connected to the second input terminal of the error amplifier.

[0012] The output of the error amplifier is connected to the input of the compensation injection module through the power amplifier unit. The output of the compensation injection module is grounded, and the second output of the second gain unit is connected to the input of the compensation injection module.

[0013] In one embodiment, the first gain unit includes a second resistor and a third resistor; a first end of the second resistor is connected to a first end of the detection module, and a second end of the second resistor is connected to a first input end of the error amplifier; a first end of the third resistor is connected to a second end of the second resistor, and a second end of the third resistor is grounded.

[0014] In one embodiment, the second gain unit includes a second resistor and a third resistor; a first end of the second resistor is connected to a second end of the detection module, and a second end of the second resistor is connected to a second input end of the error amplifier; a first end of the third resistor is connected to a second end of the second resistor, and a second end of the third resistor is connected to an input end of the compensation injection module.

[0015] In one embodiment, the power amplifier unit includes a first fourth resistor, a second fourth resistor, a first fifth resistor, a second fifth resistor, a first diode, a second diode, a first transistor, and a second transistor;

[0016] The first terminal of the first fourth resistor is connected to the first power supply, the second terminal of the first fourth resistor is connected to the first electrode of the first diode, the second electrode of the first diode is connected to the first electrode of the second diode, the second electrode of the second diode is connected to the first terminal of the second fourth resistor, and the second terminal of the second fourth resistor is connected to the second power supply.

[0017] The first terminal of the first transistor is connected to the first terminal of the first fourth resistor, the second terminal of the first transistor is connected to the first terminal of the first fifth resistor, the control terminal of the first transistor is connected to the second terminal of the first fourth resistor, and the second terminal of the first fifth resistor is connected to the input terminal of the compensation injection module.

[0018] The first end of the second fifth resistor is connected to the second end of the first fifth resistor, the second end of the second fifth resistor is connected to the first end of the second transistor, the second end of the second transistor is connected to the second end of the second fourth resistor, and the control end of the second transistor is connected to the first end of the second fourth resistor.

[0019] In one embodiment, the compensation injection module includes a sixth resistor and a first capacitor; the first end of the sixth resistor is connected to the output of the error amplifier, the second end of the sixth resistor is connected to the first end of the first capacitor, and the second end of the first capacitor is grounded.

[0020] In one embodiment, the resistance value of the sixth resistor is greater than or equal to 3Ω, and the capacitance value of the first capacitor is greater than or equal to 680nF.

[0021] In one embodiment, the detection module includes a first resistor; a first end of the first resistor is connected to the input terminal of the first gain unit, and a second end of the first resistor is connected to the input terminal of the second gain unit.

[0022] In one embodiment, the Rogowski coil module includes a printed circuit board and a Rogowski coil disposed on the printed circuit board; the detection module is connected to the Rogowski coil via a connection terminal on the printed circuit board.

[0023] Secondly, embodiments of this application provide a power system including an active EMI filter based on Rogowski coil non-contact current sensing as described in the first aspect above.

[0024] The aforementioned active EMI filter and power system based on Rogowski coil non-contact current sensing cleverly combines the non-invasive detection characteristics of the Rogowski coil with the traditional direct current injection compensation method. This fully maintains the non-contact detection characteristics, avoiding any alteration to the integrity of the original grounding loop, while simultaneously achieving wideband common-mode current suppression through a simple and efficient compensation circuit. This design solves the safety hazards caused by the need for series components in the grounding loop in traditional solutions, such as increased potential on the motor casing. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a topology diagram of a power system according to one embodiment;

[0027] Figure 2 This is a schematic diagram of the equivalent circuit of phase A of a parallel inverter according to one embodiment;

[0028] Figure 3 This is a schematic diagram of the common-mode equivalent circuit of a power system according to one embodiment;

[0029] Figure 4 This is a schematic diagram of an active EMI filter device based on Rogowski coil non-contact current sensing according to an embodiment.

[0030] Figure 5 This is a schematic diagram of a Rogowski coil current sensor according to one embodiment;

[0031] Figure 6 Here is a time-domain waveform diagram of the common-mode leakage current in one embodiment;

[0032] Figure 7 This is an enlarged view of the time-domain waveform of the common-mode leakage current in one embodiment;

[0033] Figure 8 This is a common-mode leakage current spectrum diagram of one embodiment. Detailed Implementation

[0034] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0036] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0037] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0038] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0039] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0040] Parallel inverter architecture, with its modular design, high power density, and good fault tolerance, has become the mainstream technology for large-capacity motor drive systems. Modular design facilitates manufacturing and maintenance, allows for flexible power level expansion, and the failure of a single module does not lead to complete system failure. Furthermore, carrier phase-shift modulation can effectively reduce output current ripple and increase the equivalent switching frequency. However, while high-frequency PWM (Pulse Width Modulation) improves the system's dynamic response, it also generates a serious common-mode leakage current problem through the parasitic capacitance of the motor windings to ground. In related technologies, inverters typically use switching frequencies above 10kHz to improve dynamic response performance, and SiC devices can even reach above 100kHz. High-frequency PWM modulation generates a high-frequency common-mode voltage at the motor neutral point, with an amplitude that can reach half the DC bus voltage and a spectral distribution range extending from a few kHz to tens of MHz. This common-mode voltage forms a common-mode leakage current loop through paths such as the parasitic capacitance of the motor windings to ground and the distributed capacitance of the cables.

[0041] Under high-frequency operating conditions, the impact of parasitic parameters in the system becomes increasingly significant and cannot be ignored. Parasitic capacitances ranging from several nF to hundreds of nF exist between the motor windings and the chassis; the distributed capacitance of long cables can reach hundreds of pF / m; and parasitic capacitances also exist between the heatsinks of power devices and ground. These parasitic parameters provide a low-impedance path for high-frequency common-mode currents, allowing common-mode leakage currents to reach several amperes or even higher. In parallel inverter topologies, when multiple inverter modules operate in parallel, circulating currents can occur between modules due to differences in device parameters, inconsistent drive delays, and asymmetrical layouts. Although coupling inductors can suppress differential-mode circulating currents, their suppression effect on common-mode currents is limited. More seriously, the common-mode voltages generated by each module can superimpose, significantly increasing the overall common-mode interference level of the system and making EMI (Electromagnetic Interference) problems more complex.

[0042] Common-mode leakage current poses multifaceted hazards to systems. In terms of electromagnetic interference (EMI), common-mode current generates EMI through both cable radiation and conduction, affecting the normal operation of surrounding electronic equipment. In electric vehicle applications, it may interfere with sensitive electronic devices such as in-vehicle communication, navigation, and entertainment systems; in industrial environments, it may affect the normal operation of sensors, controllers, and communication networks. Regarding motor damage, high-frequency common-mode current forms a discharge circuit through bearings, causing electro-erosion, resulting in pits and streaks on the bearing surface and accelerating bearing wear. Studies show that electro-erosion damage occurs when the bearing current density exceeds 0.1 A / mm². Furthermore, common-mode voltage accelerates winding insulation aging, shortening motor lifespan. Excessive leakage current may trigger malfunctions in protection devices, affecting normal system operation and potentially posing a threat to personal safety in some applications. Simultaneously, common-mode current generates additional losses in the system's parasitic resistance, reducing overall efficiency. Especially at high frequencies, the skin effect and proximity effect increase the equivalent resistance, exacerbating the loss problem.

[0043] Passive EMI filtering solutions in related technologies mainly include components such as common-mode inductors, Y-class capacitors, and magnetic rings. These solutions face numerous challenges in high-power, high-frequency applications. To achieve sufficient attenuation, common-mode inductors require large inductance values, resulting in bulky cores. In high-power systems of hundreds of kW, the EMI filter's volume can account for 20-30% of the entire system, and its weight can be even higher, contradicting the high power density goals of modern power electronics systems. Due to limitations in core material properties, the impedance characteristics of common-mode inductors decrease significantly at high frequencies, and parasitic capacitances in the windings can resonate at high frequencies, leading to a sharp deterioration in attenuation at certain frequency points. In high-current applications, common-mode inductors are prone to saturation, losing their filtering effect. While this can be mitigated by increasing the core cross-sectional area, this further increases size and cost.

[0044] Active EMI filtering technology cancels interference by actively injecting compensating current or voltage, theoretically achieving better filtering performance and smaller size. However, related technologies generally suffer from serious technical bottlenecks. Most active filters use current transformers for current sensing. These current transformers require magnetic cores, which are prone to saturation under high-frequency and high-current conditions, leading to measurement distortion. The hysteresis and eddy current losses of the magnetic core reduce high-frequency response, making it difficult to accurately capture the transient characteristics of rapidly changing common-mode currents. The frequency response of current transformers with magnetic cores is typically limited to below 100kHz, while the spectrum of common-mode interference can extend to tens of MHz. Related technologies require the current transformer to be directly connected in series in the main power circuit, which not only increases the system's conduction losses but also introduces additional parasitic parameters. In high-power applications, even small series impedances can generate considerable power loss and heat generation. While cascaded active filters can improve overall attenuation performance, each stage requires independent detection elements, control circuits, and power amplifiers, leading to a sharp increase in system complexity and cost. The coordination and control between multiple stages also increases the design difficulty.

[0045] More seriously, the current transformer solution in related technologies introduces new technical problems when connected to the motor grounding wire. When a current transformer or other sensing element is connected in series to the motor grounding circuit, an additional impedance is introduced into the grounding wire. Although this series impedance is small in value, it will produce a significant voltage drop under the action of high-frequency common-mode current. This voltage drop is superimposed on the motor-to-ground voltage, causing the motor casing to rise to ground potential, which may reach dangerous voltage levels in extreme cases. This phenomenon is particularly serious when the common-mode current contains high-order harmonic components, the system experiences grounding faults or insulation degradation, multiple motors share a grounding system, or long cables are in operation. The high-order harmonics of the common-mode current cause the inductive impedance to increase with increasing frequency. During grounding faults, the leakage current increases sharply. The superposition of mutual interference between multiple motors and the distributed parameter effect of long cables all exacerbate the problem of rising motor casing potential. Rising motor casing potential not only threatens personal safety but may also lead to increased shaft voltage, exacerbating bearing erosion problems. Excessively high ground voltage may also break down weak points in the insulation, causing secondary faults.

[0046] To address the aforementioned technical challenges, this application proposes an active EMI filter based on non-contact current sensing. The core innovation of this application lies in its completely non-contact detection method. A Rogowski coil is installed outside the motor ground wire for current detection, eliminating the need to disconnect or alter the original grounding loop. This fundamentally improves and avoids the problem of increased potential on the motor casing caused by series impedance in related technologies. The Rogowski coil, based on the principle of electromagnetic induction, measures current by detecting the rate of change of the magnetic field around the conductor, achieving truly non-invasive measurement. The Rogowski coil employs a hollow structure, containing no magnetic materials, fundamentally improving and avoiding magnetic saturation problems, and enabling the measurement of wideband current signals. Its excellent linearity ensures measurement accuracy over a large dynamic range. Furthermore, the output of the Rogowski coil is proportional to the derivative of the measured current, thus exhibiting high-pass characteristics, making it particularly suitable for detecting high-frequency common-mode interference.

[0047] This application's embodiments achieve effective EMI suppression using only the detection signal from a single Rogowski coil through optimized signal processing and control strategies, eliminating the need for complex multi-stage cascaded structures. This not only reduces system costs but also improves reliability. While ensuring efficient EMI suppression, the solution presented in this application completely resolves the safety hazards present in related technologies, providing a novel technical path for the electromagnetic compatibility design of high-performance motor drive systems. This approach has significant theoretical implications and broad application prospects.

[0048] In some exemplary embodiments, the power system may include an active EMI filter based on Rogowski coil-based non-contact current sensing, a parallel inverter, a DC power supply, a Line Impedance Stabilization Network (LISN), a coupled inductor, and a three-phase motor. Wherein:

[0049] In some exemplary embodiments, reference is made to Figure 1 The parallel inverter uses two typical voltage source inverter modules connected in parallel, T1 to T... 12 For IGBT (Insulated Gate Bipolar Transistor) switching transistors or next-generation SiC MOSFET (Metal Oxide Semiconductor Field Effect Transistor) power devices, D1 to D 12 For the fast recovery diode or the internal body diode of the power device connected in anti-parallel with the switching transistor, each switching transistor, power device and diode has the same model and specifications to ensure the symmetry of the two inverter modules.

[0050] In some exemplary embodiments, reference is made to Figure 1 Vdc It is a DC power supply, and the voltage level can be 400V, 600V or 800V high-voltage platform depending on the application requirements. C dc For DC bus capacitors, thin-film capacitor technology is used to obtain low equivalent series resistance and excellent high-frequency characteristics.

[0051] In some exemplary embodiments, reference is made to Figure 1 Linear impedance stabilization networks provide a standardized test impedance environment, ensuring the repeatability of EMI measurements. lisn1 C lisn2 C lisn3 C lisn4 L is the decoupling capacitor in the LISN. lisn1 L lisn2 For a 50μH standard inductor, R lisn1 R lisn2 R lisn3 R lisn4 R lisn5 A 50Ω / 50μH standard measurement network is constructed.

[0052] In some exemplary embodiments, reference is made to Figure 1 The direction of the circulating current flowing into the coupled inductor is defined as the same-name terminal. The coupled inductor is made of double E-type nanocrystalline or high-frequency ferrite cores connected together, and the coupled inductance of each phase is L. A L B L C Air gaps of 0.5-2mm are left on both sides of the magnetic pillar and in the middle to prevent magnetic saturation and to adjust the inductance value.

[0053] The core innovation of this application's embodiments lies in the use of Rogowski coils for completely non-contact common-mode current detection. The Rogowski coils are wrapped around the outside of the grounding loop conductor, without the need to disconnect or change the original circuit connection. Combined with a resistor direct injection compensation network, this achieves an active filtering scheme that is simple in structure, compact in size, and does not affect the system's grounding integrity.

[0054] First, we conduct an in-depth analysis of the non-contact detection principle based on Rogowski coils. A Rogowski coil is a hollow coil sensor based on Faraday's law of electromagnetic induction, composed of wires uniformly wound on a non-magnetic frame. Its unique advantage lies in achieving accurate current measurement without needing to be connected in series with the main circuit, fundamentally avoiding the insertion loss and safety hazards caused by the series connection of current transformers in related technologies. Compared to current transformers with magnetic cores in related technologies, the coreless structure of the Rogowski coil completely avoids magnetic saturation problems, giving it an extremely wide linear measurement range, with a frequency response extending from a few Hz to over 100 MHz and a dynamic range exceeding 80 dB. When the measured current passes through the central conductor of the Rogowski coil, according to Ampere's circuital law, the magnetic field strength generated inside the coil is proportional to the current. Due to the uniformly tightly wound structure of the coil, the electromotive force induced in each turn of the coil is equal and superimposed in series, and the total output voltage is proportional to the rate of change of magnetic flux, i.e., the differential of the measured current.

[0055] Since the parallel inverter system has three-phase symmetry, we will take phase A as an example for detailed analysis. Figure 2 This is an accurate model of the equivalent circuit of phase A of a parallel inverter. L c M and L are the self-inductance and mutual inductance of the coupled inductor, respectively. Their values ​​are determined by the characteristics of the core material, the number of turns in the winding, and the air gap length. A typical value is L. c The range is 200-500 μH, and the coupling coefficient is typically designed to be 0.4-0.6. R Aout L is the equivalent resistance of the A-phase output line, including the conductor's DC resistance and the AC resistance increment caused by the skin effect and proximity effect at high frequencies. Aout The stray inductance of the A-phase output line depends on the conductor length, cross-sectional area, and spatial layout, with typical values ​​ranging from tens of nH to several μH. C AS A represents stray capacitance to ground, mainly composed of motor winding capacitance to the chassis (typically 1-10nF), cable distributed capacitance (100-500pF / m), and power device heatsink capacitance to ground. Z LISN The standardized common-mode impedance provided for LISN remains at 50Ω ± 20% within the EMC test band of 150kHz–30MHz. A1O This is the output voltage of bridge arm A1 in inverter 1, which exhibits high-frequency square wave characteristics under SPWM or SVPWM modulation. cmA1 It is the common-mode leakage current component flowing through bridge arm A1, V A2O It is the output voltage of bridge arm A2 in inverter 2, I cmA2 It is the common-mode leakage current component flowing through bridge arm A2.

[0056] Using Thevenin's theorem and the equivalent model of coupled inductors, complex three-phase parallel systems can be simplified to common-mode equivalent circuits, such as... Figure 3As shown. According to the definition of common-mode voltage, the total common-mode voltage of the system is the arithmetic mean of the output voltages of all bridge arms: V cm = (V A1O +V A2O +V B1O +V B2O +V C1O +V C2O Under SVPWM modulation, the common-mode voltage of the parallel inverter exhibits a stepped wave at three times the switching frequency, with a peak value of ±Vdc / 6. The total leakage inductance L of the coupled inductor... leak = (L c While the leakage inductance of -M) / 6 does have some effect on limiting di / dt, it is far from sufficient to suppress the common-mode current to the level required by EMC (Electromagnetic Compatibility) standards. out R out The combined stray inductance and resistance represent the parasitic parameter characteristics of the system at high frequencies. cm The total mode leakage current flowing through the grounding loop is the target that needs to be detected and actively suppressed in the embodiments of this application.

[0057] The Rogowski coil operates based on Faraday's law of electromagnetic induction, and its output voltage v coil With the measured current i cm It is proportional to the time derivative:

[0058] (1)

[0059] Among them, M coil The mutual inductance of the Rogowski coil is determined by the coil's geometric parameters: M coil = μ0N·A / l, where μ0=4π×10⁻ 7 H / m is the free permeability, N is the total number of turns in the coil, A is the cross-sectional area enclosed by a single turn of the coil, and l is the average perimeter of the coil frame. Optimizing these parameters allows for adjustment of the detection sensitivity and frequency response characteristics. Since the output is a differential signal, it needs to be converted back into a voltage signal proportional to the common-mode current using a precision integrator to achieve accurate measurement across the entire EMI frequency band.

[0060] Taking advantage of the non-contact detection capabilities of Rogowski coils, this application innovatively designs an active EMI filter architecture based on feedback control, such as an active EMI filter device.

[0061] In some exemplary embodiments, combined with Figure 4 and Figure 5 , Figure 4This application illustrates an active filter implementation circuit provided by an embodiment of the present application, such as an active EMI filter device based on Rogowski coil non-contact current sensing, comprising a Rogowski coil module, a detection module 410, an error amplification module 420, and a compensation injection module 420. The Rogowski coil of the Rogowski coil module is wound around a ground conductor. The detection module 410 is connected to the Rogowski coil module. The input terminal of the error amplification module 420 is connected to the detection module 410, and the output terminal of the error amplification module 420 is connected to the compensation injection module 420, which is grounded. The Rogowski coil module is used to detect the common-mode leakage current flowing through the ground loop via the Rogowski coil and output a detection voltage. The detection module 410 is used to receive the detection voltage. The error amplification module 420 is used to apply a target gain to the voltage output by the detection module 410 and output the voltage after applying the gain. The compensation injection module 420 is used to generate a compensation current based on the voltage after applying the gain and output the compensation current to the ground loop.

[0062] like Figure 5 As shown, the Rogowski coil employs a uniformly tightly wound structure. The coil, wound around the grounding conductor, forms a closed detection loop, eliminating the need to disconnect the circuit during installation and enabling rapid installation through its open design. In some exemplary embodiments, after parameter optimization, the coil is designed with: an average diameter of 80mm to accommodate different sizes of grounding conductors (adjustable to 40-120mm depending on the application), 100 turns to provide sufficient detection sensitivity (adjustable within the range of 50-200 turns), a wire diameter of 0.5mm to balance DC resistance and distributed capacitance, and a turn spacing of 0.8mm to ensure uniformity. The mutual inductance coefficient M is calculated. coil Approximately 50 nH. To improve anti-interference capability and measurement accuracy, the coil adopts a double-layer shielding structure: the inner layer is a copper foil electrostatic shielding layer with a thickness of 35 μm, with one end grounded; the outer layer is an electromagnetic shielding layer made of high permeability material, effectively isolating external magnetic field interference. Figure 5 In this context, L2 represents the self-inductance of the Rogowski coil. The Rogowski coil is connected to... Figure 4 R1 is connected in parallel to the motor ground wire.

[0063] The integrator circuit integrated on the PCB board in the Rogowski coil module is a key component of signal processing. In some exemplary embodiments, it is implemented using the low-noise, high-speed operational amplifier AD8065, which features a 145MHz gain-bandwidth product, a slew rate of 180V / μs, and a low noise density of 2.7nV / √Hz. The integrated signal forms a voltage signal V proportional to the common-mode current across the sense resistor R1 (a 50Ω precision non-inductive resistor). sense The transfer function of the entire detection channel is: V sense =(M coil × R1) / (1 + jωτ) × i cmWherein, the time constant τ = 10μs, ω can be the angular frequency of the Rogowski coil, and j is the imaginary unit.

[0064] In some exemplary embodiments, the error amplification module 420 includes an error amplifier 423, a first gain unit 421, a second gain unit 422, and a power amplifier unit 424.

[0065] The input terminal of the first gain unit 421 is connected to the first terminal of the detection module 410, and the first output terminal of the first gain unit 421 is connected to the first input terminal of the error amplifier 423. The second output terminal of the first gain unit 421 is grounded. The input terminal of the second gain unit 422 is connected to the second terminal of the detection module 410, and the first output terminal of the second gain unit 422 is connected to the second input terminal of the error amplifier 423. The output terminal of the error amplifier 423 is connected to the input terminal of the compensation injection module 420 through the power amplifier unit 424. The output terminal of the compensation injection module 420 is grounded, and the second output terminal of the second gain unit 422 is connected to the input terminal of the compensation injection module 420.

[0066] In some exemplary embodiments, reference is made to Figure 4 The first gain unit 421 includes a second resistor R2 and a third resistor R3; the first end of the second resistor R2 is connected to the first end of the detection module 410, and the second end of the second resistor R2 is connected to the first input end of the error amplifier 423; the first end of the third resistor R3 is connected to the second end of the second resistor R2, and the second end of the third resistor R3 is grounded.

[0067] In some exemplary embodiments, reference is made to Figure 4 The second gain unit 422 includes a second resistor R2 and a third resistor R3; the first end of the second resistor R2 is connected to the second end of the detection module 410, and the second end of the second resistor R2 is connected to the second input end of the error amplifier 423; the first end of the third resistor R3 is connected to the second end of the second resistor R2, and the second end of the third resistor R3 is connected to the input end of the compensation injection module 420.

[0068] In some exemplary embodiments, reference is made to Figure 4 The power amplifier unit 424 includes a first fourth resistor R4, a second fourth resistor R4, a first fifth resistor R5, a second fifth resistor R5, a first diode D, a second diode D, a first transistor J, and a second transistor J.

[0069] The first terminal of the first fourth resistor R4 is connected to the first power supply Vs. The second terminal of the first fourth resistor R4 is connected to the first terminal of the first diode D. The second terminal of the first diode D is connected to the first terminal of the second diode D. The second terminal of the second diode D is connected to the first terminal of the second fourth resistor R4. The second terminal of the second fourth resistor R4 is connected to the second power supply -Vs. The first terminal of the first transistor J is connected to the first terminal of the first fourth resistor R4. The second terminal of the first transistor J is connected to the first terminal of the first fifth resistor R5. The control terminal of the first transistor J is connected to the second terminal of the first fourth resistor R4. The second terminal of the first fifth resistor R5 is connected to the input terminal of the compensation injection module 420. The first terminal of the second fifth resistor R5 is connected to the second terminal of the first fifth resistor R5. The second terminal of the second fifth resistor R5 is connected to the first terminal of the second transistor J. The second terminal of the second transistor J is connected to the second terminal of the second fourth resistor R4. The control terminal of the second transistor J is connected to the first terminal of the second fourth resistor R4. In some exemplary embodiments, the compensation injection module 420 includes a sixth resistor R6 and a first capacitor C1; the first end of the sixth resistor R6 is connected to the output terminal of the error amplifier 423, the second end of the sixth resistor R6 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is grounded.

[0070] In some exemplary embodiments, the resistance value of the sixth resistor R6 is greater than or equal to 3Ω, and the capacitance value of the first capacitor C1 is greater than or equal to 680nF.

[0071] In some exemplary embodiments, the detection module 410 includes a first resistor R1; a first end of the first resistor R1 is connected to the input terminal of the first gain unit 421, and a second end of the first resistor R1 is connected to the input terminal of the second gain unit 422.

[0072] In some exemplary embodiments, the Rogowski coil module includes a printed circuit board (PCB) and a Rogowski coil disposed on the PCB; the detection module 410 is connected to the Rogowski coil via connection terminals on the PCB.

[0073] The error amplifier module 420 and the compensation injection module 420 are the core components for achieving high-performance suppression. Considering the gain-bandwidth product, slew rate, output drive capability, power supply range, and power consumption, the THS3091 was selected as the error amplifier 423. This device features a 210MHz gain-bandwidth product, an ultra-high voltage slew rate of 7300V / μs, a wide power supply range of ±15V, and a high current output capability of ±250mA, fully meeting the requirements for fast response and large signal drive in the EMI frequency band (150kHz-30MHz). The voltage gain was set to -20 (26dB) using a precision resistor network R2 (10kΩ) and R3 (250kΩ). This gain value, after theoretical analysis and experimental optimization, achieved the best balance between suppression depth and system stability. The compensation network, consisting of R6 (3Ω) and C1 (680nF), forms a Type-II compensator, ensuring good compensation performance in the 150kHz-30MHz range.

[0074] The compensation injection module 420 is a resistor-injection type compensation circuit module, meaning it uses a direct resistor injection method. The output of the error amplifier 423 is enhanced with a power buffer stage (using a BUF634 or LH0033 high-speed buffer) to improve its driving capability. The buffer has a 250MHz bandwidth, a 2000V / μs slew rate, and a 250mA continuous output current capability. The buffer stage output is directly connected to the main circuit ground point through a low-value injection resistor R6 (3Ω, 5W wire-wound non-inductive resistor), forming a low-impedance compensation current injection path. The advantages of this direct resistor injection method include: no need for coupling transformers or high-voltage isolation capacitors, simplifying the circuit and reducing costs; flat frequency response, without the bandwidth and saturation limitations of transformers; constant and precisely controllable injection impedance; and no phase delay or parasitic parameter effects.

[0075] Compensation current i comp The relationship with the detection signal can be expressed as:

[0076] (2)

[0077] In the formula, V sense The measured voltage is the integrated voltage from the Rogowski coil, G = -20 is the voltage gain of the error amplifier 423, and Z is the voltage gain of the error amplifier 423. load This is the equivalent impedance of the grounding loop. At high frequencies, Z... load It is mainly characterized by sensitivity, but because R6 is chosen as a low value of 3Ω, compared to the typical Z... load (>10Ω@1MHz) is negligible, so the compensation current is mainly determined by the detection signal and the amplifier gain, and has good linearity.

[0078] To optimize performance across the entire frequency band, the system employs a frequency adaptive compensation strategy. In the low-frequency band (150kHz-1MHz), common-mode interference is mainly concentrated in the fundamental and lower harmonics of the switching frequency. Maintaining a constant voltage gain of 20 times provides sufficient compensation, achieving a suppression ratio of 20-26dB. In the mid-to-high frequency band (1-30MHz), the amplifier's natural roll-off characteristic is utilized to prevent noise amplification and potential parasitic oscillations, still maintaining an effective suppression of 10-15dB. R4 and R5 respectively serve as current limiters.

[0079] The closed-loop common-mode current rejection ratio (CMRR) of the system can be expressed as:

[0080] (3)

[0081] In the formula, T(jω) is the open-loop gain of the system, which is the cascaded transfer function of the detection, amplification, and injection stages. Through optimized design, T(jω) >> 1 is guaranteed within the target frequency band, theoretically achieving common-mode interference suppression of over 20dB. Considering actual parasitic parameters and non-ideal factors, the measured suppression effect reaches 26dB at 150kHz and remains above 18dB at 10MHz.

[0082] Stability design is a critical consideration for ensuring reliable system operation. The main challenge lies in compensating for multiple sources of phase lag: a 90° phase lag introduced by the Rogowski coil and integrator, propagation delay in the power stage (approximately 10-20 ns), and high-frequency phase shift caused by parasitic capacitance. Through a designed compensation network, a 45° phase lead is introduced at 5 MHz, ensuring a phase margin greater than 45° at the unity-gain frequency (approximately 30 MHz). Simultaneously, R5 limits the high-frequency gain slope to no more than -20 dB / dec, ensuring a gain margin greater than 8 dB. SPICE simulations and experimental verification demonstrate that the system maintains stable operation under various load conditions and temperature ranges (-40°C to +85°C).

[0083] The thermal design considerations for the injection resistor R6 are as follows, and its instantaneous power dissipation is:

[0084] (4)

[0085] Under the worst operating conditions, the peak common-mode current can reach 136mA, with a corresponding compensation current of approximately 102mA (considering a 20x gain), and power dissipation at the milliwatt level. Considering PWM duty cycle and RMS conversion, a 5W wire-wound resistor with a rated power of 5W is selected to provide a 5x safety margin, and a small aluminum heatsink (20×20×10mm) is sufficient to meet the heat dissipation requirements for long-term operation.

[0086] As an example, the parameters of each component can be:

[0087] Mcoil: 50nH. R1: 50Ω. R2: 10kΩ. R3: 250kΩ. R4: 100Ω. R5: 1kΩ. R6: 3Ω. C1: 680nF.

[0088] The key innovation of this application lies in the ingenious combination of the non-intrusive detection characteristics of the Rogowski coil with the traditional direct current injection compensation method. This not only fully maintains the non-contact detection characteristics and avoids altering the integrity of the original grounding loop, but also achieves wideband common-mode current suppression through a simple and efficient compensation circuit. This design solves the safety hazards caused by the need for series components in the grounding loop in traditional solutions, such as the potential rise of the motor casing.

[0089] A complete parallel inverter system and active filter simulation model were built in LTspice, and the suppression effect before and after adding the active filter proposed in this application was compared and analyzed. Figure 6 The time-domain waveform comparison of the common-mode leakage current is shown. Figure 8 The comparison of frequency domain characteristics is presented. Simulation results show that after adopting the active EMI filter based on Rogowski coil non-contact detection and resistor injection compensation, the peak common-mode leakage current decreased from the original 137mA to 26mA, and the effective value decreased from 98mA to 29mA. In frequency domain analysis, the maximum attenuation reached 28dB, with 22dB attenuation at 1MHz and a 15dB suppression effect still maintained at 10MHz, demonstrating excellent overall suppression performance. Particularly noteworthy is that, due to the completely non-contact detection scheme, the system grounding loop remains intact, and the motor casing's potential to ground is always kept within a safe range, completely resolving the safety hazards of traditional solutions.

[0090] This application proposes an innovative current-compensated active EMI filter design based on Rogowski coil non-contact sensing. It innovatively employs a hollow Rogowski coil wound around the outside of the grounding loop for common-mode current detection without disconnecting the main circuit. Combined with a direct resistor injection compensation structure, this improves system detection accuracy and compensation efficiency. The coreless structure of the Rogowski coil completely avoids the magnetic saturation limitations of traditional current transformers, exhibiting better detection accuracy at high frequencies. The direct resistor injection compensation method eliminates the coupling transformer required in related technologies, significantly simplifying the circuit structure and reducing system cost. Compared to passive filtering solutions in related technologies, this application achieves 15-28dB suppression in the 150kHz-30MHz range, while reducing size by 60% and weight by 50%. This design has broad application prospects, especially in high-frequency switching power equipment such as new energy vehicle electric drive systems, industrial servo drives, and wind and solar inverters, providing a non-intrusive, high-precision, and compact EMI suppression solution.

[0091] The active EMI filter device based on Rogowski coil non-contact current sensing provided in this application embodiment can be applied, for example but not limited to, to high-frequency switching power equipment such as motor drive systems, new energy vehicle electric drive systems, industrial servo controllers, wind power and photovoltaic grid-connected inverters, high-power energy storage systems, and aerospace power supply devices. It is used to perform non-intrusive wideband detection and active compensation for common-mode interference current generated by PWM modulation. By injecting reverse current in real time through a voltage source type compensation network, it effectively suppresses conducted electromagnetic noise, meets international EMC standard requirements, prevents motor bearing current damage, and improves system electromagnetic compatibility and operational reliability.

[0092] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An active EMI filter device based on a non-contact current sensing of a Rogowski coil, characterized by, The device comprises a Rogowski coil module, a detection module, an error amplification module and a compensation injection module; the Rogowski coil of the Rogowski coil module surrounds the ground conductor; the detection module is connected with the Rogowski coil module; the input end of the error amplification module is connected with the detection module, the output end of the error amplification module is connected with the compensation injection module, and the compensation injection module is grounded; The Rogowski coil module is used for detecting common-mode leakage current flowing through the ground loop through the Rogowski coil and outputting a detection voltage; The detection module is used for receiving the detection voltage; The error amplification module is used for applying a target gain to the voltage output by the detection module and outputting the voltage after the gain is applied; The compensation injection module is used for generating a compensation current according to the voltage after the gain is applied and outputting the compensation current to the ground loop.

2. The apparatus of claim 1, wherein, The error amplification module comprises an error amplifier, a first gain unit, a second gain unit and a power amplifier unit; The input end of the first gain unit is connected with the first end of the detection module, the first output end of the first gain unit is connected with the first input end of the error amplifier, and the second output end of the first gain unit is grounded; The input end of the second gain unit is connected with the second end of the detection module, and the first output end of the second gain unit is connected with the second input end of the error amplifier; The output end of the error amplifier is connected with the input end of the compensation injection module through the power amplifier unit, the output end of the compensation injection module is grounded, and the second output end of the second gain unit is connected with the input end of the compensation injection module.

3. The apparatus of claim 2, wherein, The first gain unit comprises a second resistor and a third resistor; the first end of the second resistor is connected with the first end of the detection module, and the second end of the second resistor is connected with the first input end of the error amplifier; the first end of the third resistor is connected with the second end of the second resistor, and the second end of the third resistor is grounded.

4. The apparatus of claim 2, wherein, The second gain unit comprises a second resistor and a third resistor; the first end of the second resistor is connected with the second end of the detection module, and the second end of the second resistor is connected with the second input end of the error amplifier; the first end of the third resistor is connected with the second end of the second resistor, and the second end of the third resistor is connected with the input end of the compensation injection module.

5. The apparatus of claim 2, wherein, The power amplifier unit comprises a first fourth resistor, a second fourth resistor, a first fifth resistor, a second fifth resistor, a first diode, a second diode, a first triode and a second triode; The first end of the first fourth resistor is connected with a first power supply, the second end of the first fourth resistor is connected with the first electrode of the first diode, the second electrode of the first diode is connected with the first electrode of the second diode, the second electrode of the second diode is connected with the first end of the second fourth resistor, and the second end of the second fourth resistor is connected with a second power supply; The first end of the first triode is connected with the first end of the first fourth resistor, the second end of the first triode is connected with the first end of the first fifth resistor, the control end of the first triode is connected with the second end of the first fourth resistor, and the second end of the first fifth resistor is connected with the input end of the compensation injection module. The first end of the second fifth resistor is connected with the second end of the first fifth resistor, the second end of the second fifth resistor is connected with the first end of the second triode, the second end of the second triode is connected with the second end of the second fourth resistor, and the control end of the second triode is connected with the first end of the second fourth resistor.

6. The apparatus of claim 2, wherein, The compensation injection module comprises a sixth resistor and a first capacitor, the first end of the sixth resistor is connected with the output end of the error amplifier, the second end of the sixth resistor is connected with the first end of the first capacitor, and the second end of the first capacitor is grounded.

7. The apparatus of claim 6, wherein, The resistance value of the sixth resistor is greater than or equal to 3Ω, and the capacitance value of the first capacitor is greater than or equal to 680nF.

8. The apparatus of claim 1, wherein, The detection module comprises a first resistor, the first end of the first resistor is connected with the input end of the first gain unit, and the second end of the first resistor is connected with the input end of the second gain unit.

9. The apparatus of claim 1, wherein, The Rogowski coil module comprises a printed circuit board and a Rogowski coil arranged on the printed circuit board, and the detection module is connected with the Rogowski coil through a connecting terminal on the printed circuit board.

10. A power system characterized by, An active EMI filter device based on a Rogowski coil non-contact current sensor, comprising the active EMI filter device based on a Rogowski coil non-contact current sensor according to any one of claims 1-9.

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