Electric drive system hybrid common mode emi filter based on virtual common mode inductance enhancement

Abstract

The application discloses a virtual common-mode inductance enhancement-based electric drive system hybrid common-mode EMI filter, belongs to the field of power electronics, and aims at solving the problem that traditional filters are difficult to balance between full-band suppression, volume power density and regulatory restrictions. The application comprises an LC passive common-mode base, a three-winding current transformer CT, a virtual common-mode inductance pump-up assembly and a virtual common-mode capacitance enhancement assembly; the LC passive common-mode base is connected between a direct-current power supply and a motor inverter; two windings of the primary side of the three-winding current transformer CT reuse the common-mode inductance of the LC passive common-mode base, and the auxiliary winding of the secondary side is connected with the virtual common-mode inductance pump-up assembly and the virtual common-mode capacitance enhancement assembly; the virtual common-mode inductance pump-up assembly is a negative impedance network and is used for low-frequency common-mode EMI suppression; and the virtual common-mode capacitance enhancement assembly is a feedback current detection current compensation network and is used for high-frequency common-mode EMI suppression.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, specifically relating to a hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement. Background Technology

[0002] With the continuous advancement of technology, the overall performance of power electronic devices has significantly improved. In applications such as motor drives, wide-bandgap semiconductor devices (such as SiCMOSFETs and GaNHEMTs) are increasingly used in three-phase motor drive systems to achieve better system control and higher energy efficiency. However, their high switching frequencies and extremely fast switching transients (high dv / dt) bring about severe conducted common-mode electromagnetic interference (EMI) problems. EMI is generally classified into common-mode interference and differential-mode interference. These not only seriously affect the stable operation of surrounding electrical and electronic equipment but also become a key bottleneck restricting the advancement of power electronics technology to higher frequencies.

[0003] To address conducted common-mode electromagnetic interference (EMI) in motor drive systems and meet the requirements of international electromagnetic compatibility standards such as CISPR 11, it is crucial to adopt effective suppression measures to reduce its harmful effects. Currently, mainstream EMI suppression strategies can be broadly categorized into two types: source suppression and propagation path suppression. Specifically, source suppression often relies on innovating the inverter's hardware topology or introducing novel modulation algorithms to reduce the amplitude and frequency of the common-mode voltage. However, these methods tend to make the software algorithms increasingly complex and significantly increase the cost and difficulty of hardware implementation. On the other hand, propagation path suppression is typically represented by the introduction of passive LC filters or single active EMI filters. However, for traditional passive LC filters, due to strict safety regulations on leakage current, the value of the common-mode Y capacitor is usually limited to the nanofarad level. To obtain a sufficiently low filter cutoff frequency, the size and weight of the common-mode inductor must be significantly increased, which severely reduces the power density of the motor drive system. Simultaneously, purely passive filters are prone to low-frequency LC series resonance with the motor's parasitic capacitance, leading to abnormal amplification of low-frequency noise. For single feedback or feedforward active EMI filters, noise detection can be achieved through voltage or current sensing. However, current compensation is typically implemented using a RC injection network. This is because voltage compensation requires an additional transformer, which contradicts the core principle of active EMI filters: improving system power density. Using a traditional current-compensated active EMI filter is equivalent to constructing a high-frequency "super common-mode Y capacitor," offering excellent high-frequency attenuation. However, in the low-frequency range, due to the extremely high capacitive reactance of the injected capacitor, the operational amplifier is prone to voltage saturation to output sufficient compensation current, leading to low-frequency suppression failure. Therefore, there is an urgent need for an integrated filtering technology that can simultaneously address these issues, achieving efficient common-mode EMI suppression across the entire frequency range (150kHz-30MHz) without increasing the physical inductor / capacitor volume or meeting safety leakage current limits. Summary of the Invention

[0004] To address the challenge of balancing full-band suppression, volumetric power density, and safety regulations in traditional filters, this invention provides a hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement.

[0005] The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement described in this invention includes an LC passive common-mode base, a three-winding current transformer (CT), a virtual common-mode inductance pump-up component, and a virtual common-mode capacitor enhancement component.

[0006] The LC passive common-mode base includes a common-mode inductor. , and common-mode Y capacitor , It connects between the DC power supply and the motor inverter;

[0007] The three-winding current transformer (CT) includes two primary windings and a secondary auxiliary winding. The two primary windings reuse the common-mode inductor of the LC passive common-mode base. , The three-winding current transformer (CT) is used to detect common-mode current and cancel differential-mode current, and the secondary auxiliary winding... Simultaneously connect the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component;

[0008] The virtual common-mode inductor pump-up component is a negative impedance network, connected to the secondary auxiliary winding. Coupling enables the common-mode inductor , Virtual inductive pump-up; used for low-frequency common-mode EMI suppression;

[0009] The virtual common-mode capacitance enhancement component is a feedback current detection and compensation network that reuses a three-winding current transformer (CT) to enhance the common-mode Y capacitor. , Virtual capacitance enhancement; used for high-frequency common-mode EMI suppression.

[0010] Preferably, the virtual common-mode inductor pump-up assembly includes an inductor. ,resistance ,resistance and the first operational amplifier ;

[0011] First operational amplifier The non-inverting input terminals are respectively connected to the secondary auxiliary winding. Same-name terminal, resistor One end;

[0012] First operational amplifier The inverting input terminals are respectively connected to inductors One end, resistor One end;

[0013] resistance The other end, resistor The other end is connected to the first operational amplifier. Output terminal;

[0014] Secondary auxiliary winding Heterogeneous terminal, inductor The other end is grounded together;

[0015] The equivalent impedance of the negative impedance network is: In the formula Represents the Laplace operator;

[0016] The parameter constraints for virtual inductor pump-up are satisfied: .

[0017] Preferably, the virtual common-mode capacitance enhancement component is a feedback current detection and current compensation network, including a multiplexed three-winding current transformer (CT), a reverse proportional amplifier circuit, a push-pull current amplifier circuit, and a resistor-capacitor injection network.

[0018] The three-winding current transformer (CT) detects the common-mode current and outputs it to the inverting proportional amplifier circuit.

[0019] The inverting amplifier circuit includes a sampling resistor. Voltage divider resistors Phase compensation capacitor Second operational amplifier The sampling resistor Equivalent impedance of negative impedance network When connected in parallel, they together serve as the auxiliary windings of the secondary side of a three-winding current transformer (CT). The load is used to convert the common-mode current into a voltage signal, which is then passed through a second operational amplifier. The reverse amplification outputs a reverse injection voltage;

[0020] The push-pull current amplifier circuit includes a push-pull current amplifier transistor. , It receives the reverse injection voltage and expands the circuit to output drive current;

[0021] The drive signal output from the push-pull current amplifier circuit is then injected through an RC injection network to output a common-mode compensation current with equal amplitude and opposite phase.

[0022] Preferably, the voltage amplification factor of the inverting proportional amplifier circuit is... satisfy .

[0023] Preferably, the resistor-capacitor injection network includes an injection capacitor. Injection capacitor and injection resistance The injected capacitor One end of the injection capacitor is connected to the positive terminal of the DC bus. One end of the injection capacitor is connected to the negative terminal of the DC bus. The other end is connected to the injection capacitor The other end is connected to the injection resistor. Connect the output terminal of the push-pull current amplifier circuit; the impedance of the RC injection network satisfy .

[0024] Preferably, the virtual common-mode inductor pump-up component operates in the low-frequency band of 150kHz to 3.693MHz, and the virtual common-mode capacitor enhancement component operates in the high-frequency band of 3.693MHz to 30MHz. The two frequency bands complement each other and together achieve common-mode EMI suppression across the entire frequency band of 150kHz–30MHz.

[0025] Preferably, by adjusting the sampling resistor The resistance value controls the boundary frequency between the operating frequency bands of the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component.

[0026] Low-frequency operating conditions meet Noise suppression is dominated by virtual common-mode inductor pump-up components;

[0027] High-frequency operating conditions meet Noise suppression is dominated by virtual common-mode capacitor enhancement components.

[0028] Preferably, the common-mode inductor , The inductance value is set to a range of 0.5~1.5mH.

[0029] Preferably, the common-mode Y capacitor , The capacitance value is selected to meet the safety regulations for leakage current limits of high-voltage DC buses.

[0030] The beneficial effects of this invention are as follows: By introducing a negative impedance network, this invention constructs an equivalent negative inductive load on the secondary side of the current transformer, resulting in a virtual pump of several times or even tens of times the common-mode inductance of the primary side. This significantly improves the low-frequency common-mode attenuation capability without increasing the physical inductance value. Simultaneously, by using the same current transformer to detect the common-mode current, and then amplifying it in reverse through an operational amplifier before feeding back the compensation current through a RC injection network, a virtual enhancement of the common-mode Y-capacitor value is achieved. This forms a low-impedance injection path in the high-frequency band, improving the high-frequency suppression effect. The effective operating frequency bands of the two active filter components are complementary, and they share the same transformer and operational amplifier chip, achieving a unification of virtual enhancement of inductive and capacitive capacitance and efficient device reuse. Thus, without increasing the size of physical inductors and capacitors and strictly meeting safety leakage current limits, deep suppression of common-mode EMI across the entire frequency band (150kHz–30MHz) was achieved (simulated time-domain noise envelope reduced from ±40mV to ±4.1mV, and frequency domain spike reduced from -53.4dBV to -117.1dBV). At the same time, the low-frequency resonance amplification problem of traditional passive filters was effectively avoided. Furthermore, by reusing key components, the filtering performance was improved while controlling the size and cost, providing an integrated EMI solution for electric drive systems that is high-power-density, low-cost, safe, and reliable. Attached Figure Description

[0031] Figure 1 This is a diagram showing the overall topology of the hybrid common-mode EMI filter based on virtual common-mode inductance-capacitance enhancement and efficient device multiplexing according to the present invention.

[0032] Figure 2 This is the equivalent schematic diagram of the negative impedance network in this invention;

[0033] Figure 3 This is a simplified equivalent diagram of the current transformer CT detection network in this invention;

[0034] Figure 4 The time-domain simulation waveform of common-mode EMI without any filters added;

[0035] Figure 5 The frequency domain simulation spectrum of common-mode EMI without any filters added;

[0036] Figure 6 The time-domain simulation waveform of common-mode EMI when only a passive LC filter is added;

[0037] Figure 7 Frequency domain simulation spectrum of common-mode EMI when only a passive LC filter is added;

[0038] Figure 8 The time-domain simulation waveform of common-mode EMI when only a virtual common-mode inductor pump-up filter based on a negative impedance network is added;

[0039] Figure 9 The frequency domain simulation spectrum of common-mode EMI when only a virtual common-mode inductor pump-up filter based on a negative impedance network is added;

[0040] Figure 10 The time-domain simulation waveform of common-mode EMI when only a virtual common-mode capacitor enhancement filter based on a feedback current sensing and compensation network is added;

[0041] Figure 11 The frequency domain simulation spectrum of common-mode EMI when only a virtual common-mode capacitor enhancement filter based on a feedback current sensing and compensation network is added;

[0042] Figure 12 The above is a time-domain simulation waveform of the overall hybrid common-mode EMI filter of this invention.

[0043] Figure 13 This is the frequency domain simulation spectrum of the hybrid common-mode EMI filter of this invention. Detailed Implementation

[0044] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0045] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0046] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; and the term "one embodiment" means "at least one embodiment". Definitions of other terms will be given in the following description. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used only to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies.

[0047] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0048] The names of the messages or information exchanged between the multiple devices in the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0049] Combination Figure 1 As shown in the figure, an embodiment of the present invention provides a hybrid common-mode electromagnetic interference filter for an electric drive system based on virtual common-mode inductance-capacitance enhancement, including an LC passive common-mode base, a three-winding current transformer (CT), a virtual common-mode inductance pump-up component, and a virtual common-mode capacitor enhancement component.

[0050] The LC passive common-mode base includes a common-mode inductor. , and common-mode Y capacitor , It connects between the DC power supply and the motor inverter. This LC passive common-mode base uses LC filter parameters with small inductance and small capacity, which can effectively improve the power density of the drive system. However, due to the excessively high cutoff frequency of the filter, it cannot achieve a satisfactory electromagnetic interference suppression effect. Therefore, it is necessary to introduce subsequent active filter components for enhancement.

[0051] The three-winding current transformer (CT) includes two primary windings and a secondary auxiliary winding. The two primary windings reuse the common-mode inductor of the LC passive common-mode base. , The three-winding current transformer (CT) is used to detect common-mode current and cancel differential-mode current. The secondary auxiliary winding... Simultaneously connect the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component. This three-winding current transformer (CT) uses two primary windings connected in parallel to detect common-mode current and cancel differential-mode current, with a secondary auxiliary winding... Simultaneously connecting the negative impedance network component and the feedback current detection and compensation component enables efficient device reuse of the current transformer, effectively controlling the cost and size of the filter device while achieving stronger electromagnetic interference suppression performance.

[0052] The virtual common-mode inductor pump-up component is a negative impedance network, and it is connected to the secondary auxiliary winding. Coupling is achieved for the common-mode inductor. , Virtual inductive reactance pumping is used for low-frequency common-mode electromagnetic interference suppression. This is achieved through the auxiliary winding on the secondary side of the current transformer. Connecting a negative impedance load enables the common-mode inductance of the primary side of the current transformer. and The virtual inductive pump-up provides stronger common-mode rejection, effectively improving low-frequency noise attenuation and significantly reducing resonance without physically increasing the common-mode inductance. Compared to traditional passive solutions that rely solely on physically increasing inductance and capacitance, this component achieves stronger low-frequency suppression while maintaining a small size.

[0053] The virtual common-mode capacitance enhancement component is a feedback current detection and compensation network that reuses the three-winding current transformer (CT) to enhance the common-mode Y capacitor. , The virtual capacitance enhancement is used for high-frequency common-mode electromagnetic interference suppression. This component detects the common-mode current through a three-winding current transformer (CT), amplifies it through an inverting proportional amplifier circuit, and then feeds back the compensation current through a RC injection network. This achieves a virtual enhancement of the common-mode Y capacitor value, thereby forming a low-impedance injection path in the high-frequency band and improving the high-frequency suppression effect.

[0054] Specifically, this invention achieves full-band deep suppression of common-mode electromagnetic interference in motor drive systems through a virtual common-mode inductance-capacitance enhancement mechanism and a highly efficient device reuse strategy, without increasing the physical inductor and capacitor volume or strictly meeting safety leakage current limits. Specifically, the virtual common-mode inductance boosting component constructs an equivalent negative inductance load through a negative impedance network, resulting in a virtual boost of several times or even tens of times the primary-side common-mode inductor impedance. This significantly improves low-frequency common-mode attenuation capability without increasing the physical inductance value. The virtual common-mode capacitor enhancement component, by detecting the common-mode current and feeding back compensation current, virtually enhances the capacitance value of the common-mode Y capacitor, thereby forming a low-impedance injection path in the high-frequency band and improving high-frequency suppression. The effective operating frequency bands of the two active filter components are perfectly complementary—the virtual common-mode inductor pump-up component mainly operates in the low-frequency band from 150kHz to 3.693MHz, while the virtual common-mode capacitor enhancement component mainly operates in the high-frequency band from 3.693MHz to 30MHz—and they share the same three-winding current transformer (CT) and dual operational amplifier chip, achieving a unified approach of virtual inductance-capacitance enhancement and efficient device reuse. Therefore, this invention has achieved significant technical results in simulation verification: the time-domain common-mode noise envelope is... mV drops to mV, frequency domain spikes are dBV decreased to dBV, while effectively avoiding the low-frequency resonant amplification problem of traditional passive filters.

[0055] Furthermore, the virtual common-mode inductor pump-up assembly includes an inductor. ,resistance ,resistance and the first operational amplifier .

[0056] First operational amplifier The non-inverting input terminals are respectively connected to the secondary auxiliary winding. Same-name terminal, resistor One end; the first operational amplifier The inverting input terminals are respectively connected to inductors One end, resistor One end; resistor The other end, resistor The other end is connected to the first operational amplifier. Output terminal; secondary auxiliary winding Heterogeneous terminal, inductor The other end is grounded together.

[0057] Specifically, this virtual common-mode inductor pump-up component achieves inductor pump-up by constructing a negative impedance conversion circuit. Its working mechanism lies in using the auxiliary winding on the secondary side of the current transformer... By connecting a negative impedance load, the equivalent impedance of the primary-side common-mode inductor is altered. When the impedance characteristics of the negative impedance network meet certain conditions, the equivalent impedance of the primary-side common-mode inductor can be increased by several times or even tens of times, thereby significantly enhancing low-frequency common-mode attenuation without increasing the physical inductance value. This component requires only a single operational amplifier circuit, greatly reducing design complexity, and compared to traditional passive solutions that rely solely on physically increasing inductance and capacitance, it achieves stronger low-frequency suppression while maintaining a small size.

[0058] The equivalent schematic diagram of a negative impedance network is as follows: Figure 2 As shown, Figure 2 In , , This constitutes a three-winding current transformer (CT). and It is the primary winding of the common-mode choke. This is the secondary auxiliary winding, which is connected to the negative impedance network. ( ; This refers to the mutual inductance between the three windings. For clarity, we first define the reference directions for the voltage and current of each winding: all voltages and currents are considered positive when flowing out from the same terminal. The mutual inductance parameters satisfy... The voltage mutual inductance equations for three windings are as follows, where... For the Laplace operator, , , These are the terminal voltages of the three windings, , , These represent the currents of the three windings, , , , , , These are the mutual inductances between the windings, and satisfy... :

[0059] (1)

[0060] Auxiliary winding External negative impedance The relationship between its terminal voltage and current is as follows (because the current flows out of the terminal with the same name, the voltage drop across the impedance is in the opposite direction to the induced electromotive force):

[0061] (2)

[0062] The current can be calculated using formulas (1) and (2). The values ​​are as follows:

[0063] (3)

[0064] Current Substituting back into formula (1), we get:

[0065] (4)

[0066] In common-mode conditions, the same current flows through both main windings, i.e. ,in Common-mode current, , Let be the equivalent impedances of the two common-mode inductors on the primary side. Then, the equivalent impedance of the primary common-mode inductor... , They are respectively:

[0067] (5)

[0068] As can be seen from formula (5), the common-mode impedance of the proposed three-winding common-mode choke based on an active negative impedance network consists of an additional impedance term forming an extra coefficient compared to the original two-winding common-mode choke. Multiply by the initial impedance of the common-mode choke. When a resistor is used as the load, this factor is always less than 1, meaning the common-mode impedance of the primary-side common-mode choke deteriorates. However, the situation changes if a negative inductor is used as the load. When the negative inductor is designed to be slightly larger than... At this time, this additional coefficient can be controlled to be much greater than 1. In this way, the common-mode impedance of the primary-side common-mode choke is increased several times, thereby achieving virtual common-mode inductance pumping and enhanced electromagnetic interference noise attenuation while maintaining the physical structure unchanged.

[0069] Simultaneously, based on the small-signal model of the operational amplifier and Figure 2 The impedance value of a negative impedance network can be derived from its topological form. The expression is, where This is the equivalent impedance of the negative impedance network. , The resistor is located in a negative impedance network. Inductance in a negative impedance network:

[0070] (6)

[0071] At this point, the equivalent impedance of the negative inductor network in formula (6) is... Substituting into formula (5), we can obtain the equivalent common-mode impedance of the common-mode inductor on the primary side of the common-mode electromagnetic interference filter based on a negative impedance network proposed in this invention:

[0072] (7)

[0073] To achieve inductive reactance pump-up of the primary-side common-mode inductor, the following must be satisfied:

[0074] (8)

[0075] Therefore, based on the above analysis, when designing this part of the active common-mode electromagnetic interference filter component based on the negative impedance network, as long as the parameter value requirements in formula (8) are met, the inductive reactance of the primary common-mode inductor can be effectively pumped up. Thus, after introducing the principle of the virtual common-mode inductor pumping active filter component based on the negative impedance network and the component selection design, the theoretical feasibility verification and the entire design process of this component have been completed.

[0076] Furthermore, the virtual common-mode capacitance enhancement component is a feedback current detection and current compensation network, including a multiplexed three-winding current transformer (CT), a reverse proportional amplifier circuit, a push-pull current amplifier circuit, and an RC injection network.

[0077] The inverting amplifier circuit includes a sampling resistor. Voltage divider resistors Phase compensation capacitor Second operational amplifier The sampling resistor The equivalent impedance of the negative impedance network After being connected in parallel, they together serve as the auxiliary windings of the secondary side of the three-winding current transformer (CT). The load is used to convert the common-mode current into a voltage signal, which is then passed through the second operational amplifier. The reverse amplification outputs a reverse injection voltage.

[0078] The push-pull current amplifier circuit includes a push-pull current amplifier transistor. , It receives the reverse injection voltage and expands the output drive current of the charging circuit, that is, it increases the output current capability while keeping the output voltage almost constant.

[0079] The drive signal output from the push-pull current amplifier circuit is then injected through an RC injection network to output a common-mode compensation current with equal amplitude and opposite phase.

[0080] Specifically, the working mechanism of this virtual common-mode capacitance enhancement component lies in achieving virtual enhancement of the common-mode Y capacitance value through current detection and current compensation. The three-winding current transformer (CT) is placed at the rear end of the line impedance stabilization network, serving to detect the common-mode current at the test end. The secondary side of the current transformer transmits the detected, scaled common-mode current through the auxiliary winding... Parallel sampling resistors The negative impedance network converts the signal into a voltage signal, which is then amplified by an inverting proportional amplifier circuit to output a reverse injection voltage, thereby enabling the control of the common-mode Y capacitor. and The virtual enhancement reduces the impedance of this branch. Finally, the reverse-injected voltage, through a RC injection network, effectively injects common-mode compensation currents of equal amplitude and opposite phase, effectively reducing the common-mode current at the line impedance stabilization network end. The push-pull current amplifier circuit amplifies the output drive current of the charging circuit while maintaining a nearly constant output voltage. The capacitive coupling of this injection network provides the necessary isolation to meet safety standards, enabling effective blocking of low-frequency signals and reliable flow of high-frequency common-mode signals.

[0081] In a preferred embodiment, combined with Figure 3 As shown, according to Figure 1 From the topology of the hybrid common-mode electromagnetic interference filter mentioned above, we can see the sampling resistor. impedance of negative impedance network The load on the secondary winding converts the detected common-mode current into voltage and pumps up the primary common-mode inductance. Figure 3 A simplified diagram of the detection network for a three-winding current transformer (CT) is given, where the primary-to-secondary turns ratio of the CT is... , and It is the load impedance of the secondary side of the three-winding current transformer (CT), and the common-mode current flowing into the primary winding of the three-winding current transformer (CT) is used for... To represent. Based on Figure 3 Common-mode current can be obtained. Voltage across the load impedance transimpedance It can be represented as:

[0082] (9)

[0083] in, For transimpedance gain, This is the voltage across the load on the secondary side of the current transformer. This refers to the common-mode current flowing into the primary side of the current transformer. This represents the turns ratio of the primary to the secondary side of the current transformer.

[0084] Furthermore, the voltage amplification factor of the inverting proportional amplifier circuit satisfy .

[0085] Specifically, by the sampling resistor Voltage divider resistors and phase compensation capacitor The inverting proportional amplifier circuit is responsible for amplifying the voltage detected by the secondary side of the three-winding current transformer (CT) in reverse. The phase compensation capacitor... The primary function of the push-pull current amplifier circuit is to compensate for high-frequency phase and improve system stability. It primarily amplifies the op-amp's output current without changing its output voltage. Therefore, the op-amp voltage amplification factor can be obtained. for,

[0086] (10)

[0087] in, This represents the voltage amplification factor of the inverting proportional amplifier circuit. This is the reverse injection voltage. This is the detection voltage on the secondary side of a three-winding current transformer (CT).

[0088] The voltage amplification factor determines the amplification factor of the detected common-mode voltage signal. This is achieved by appropriately setting the voltage divider resistors. With sampling resistor The ratio allows for flexible control of the reverse injection voltage amplitude, ensuring that the compensation current effectively offsets the original common-mode current. Phase compensation capacitor. With voltage divider resistor Parallel connection is mainly used to compensate for high-frequency phase and improve system stability.

[0089] Furthermore, the RC injection network includes an injection capacitor. Injection capacitor and injection resistance The injected capacitor One end of the injection capacitor is connected to the positive terminal of the DC bus. One end of the injection capacitor is connected to the negative terminal of the DC bus. The other end is connected to the injection capacitor The other end is connected to the injection resistor. Connect the output terminal of the push-pull current amplifier circuit; the impedance of the RC injection network satisfy:

[0090] (11)

[0091] The RC injection network has the following three functions: ① It requires the injection of capacitors. and ① Isolate the active electromagnetic interference filter from the high-voltage DC input; ② Inject capacitor , and injection resistance It also generates a first-order high-pass filter to further reduce unwanted injection current below the relevant frequency range in electromagnetic interference standards; ③ In the range above the high-pass filter cutoff frequency, the injection resistance... This helps maintain a constant impedance in the RC injection network. Based on the above analysis, the common-mode current compensation injection section is an RC circuit with a impedance of... It can be represented as .

[0092] Based on formulas (9) to (11), the development of a virtual common-mode capacitor enhancement component for a feedback current sensing and compensation network that completes the entire process from detecting common-mode current to reverse compensation of noise current can be realized.

[0093] Furthermore, the virtual common-mode inductor pump-up component operates in the low-frequency band of 150kHz to 3.693MHz, and the virtual common-mode capacitor enhancement component operates in the high-frequency band of 3.693MHz to 30MHz. The two frequency bands complement each other and together achieve common-mode electromagnetic interference suppression across the entire frequency band from 150kHz to 30MHz.

[0094] Specifically, the virtual common-mode inductor boosting component based on a negative impedance network fails at high frequencies because the parasitic inductor parameters in the negative impedance network cause inductor deformation. Therefore, the main effective range of this network is generally in the low-frequency band. In contrast, the virtual common-mode capacitor enhancement component based on feedback current sensing and compensation has a large impedance injected into the RC network in the low-frequency range, resulting in a small reverse current amplitude for compensation. However, in the high-frequency range, the impedance of the injected RC network is very low, allowing for a higher amplitude injection of the reverse compensation current through a current transformer and operational amplifier. The optimal operating frequency bands of the two components are complementary. By effectively combining them, their respective advantages can be leveraged, and efficient component reuse can be achieved. This enables effective suppression of common-mode electromagnetic interference in electric drive systems while achieving lower cost and higher power density.

[0095] Furthermore, by adjusting the sampling resistor The resistance value controls the boundary frequency between the operating frequency bands of the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component.

[0096] Low-frequency operating conditions meet Noise suppression is dominated by virtual common-mode inductor pump-up components; high-frequency operating conditions meet [the requirements]. Noise suppression is dominated by virtual common-mode capacitor enhancement components.

[0097] Specifically, according to formula (6) The expression clearly reveals It possesses inductive properties, therefore satisfying the requirements in the relatively low frequency range. ,Depend on Figure 3 The parallel relationship in the diagram indicates the secondary inductance of the current transformer at this time. Mainly related to negative impedance networks Phase coupling makes active electromagnetic interference filtering based on negative impedance networks crucial; and when in the relatively high-frequency region... At this time, the secondary inductance of the current transformer Mainly related to the sampling resistor Due to phase coupling, active electromagnetic interference filtering based on feedback current sensing and current compensation plays a major role in suppressing interference. Therefore, the sampling resistor can be designed according to the critical frequency points of the two components. The value of the two active filter components is thus adjusted to flexibly control the effective operating frequency range of the two components. Based on this, the hybrid common-mode electromagnetic interference filter not only effectively pumps up the common-mode inductance and capacitance respectively, but also complements each other in its operating frequency range, achieving good compatibility and superior common-mode electromagnetic interference suppression capability. At the same time, it also realizes efficient and reliable multiplexing of current transformers and dual operational amplifier chips, greatly improving the power density of the motor drive system.

[0098] By designing the sampling resistor The value of can be flexibly adjusted to control the effective frequency band boundary between the negative impedance network and the feedback compensation network. At low frequencies, the equivalent impedance of the negative impedance network... much smaller The secondary inductance of the current transformer Primarily coupled to a negative impedance network, the virtual common-mode inductor pump-up component plays a crucial role; at high frequencies... Much larger The secondary inductance of the current transformer Mainly related to sampling resistor The coupling and virtual common-mode capacitance enhancement components play a major role in suppression. This allows the filter to be adapted and optimized for specific application scenarios.

[0099] Furthermore, the common-mode inductor , The inductance value is 0.5mH to 1.5mH.

[0100] Specifically, because this invention effectively enhances the equivalent impedance of the common-mode inductor through a virtual capacitance enhancement mechanism, a small-value common-mode inductor can be physically used, thereby reducing the filter size and increasing the system power density. This inductance value range, while ensuring safety leakage current limits, achieves excellent full-band electromagnetic interference suppression performance in conjunction with active filter components.

[0101] Furthermore, the common-mode Y capacitor , The capacitance value is selected to meet the safety regulations for leakage current limits of high-voltage DC buses.

[0102] Specifically, since the present invention effectively improves the reduction effect of the equivalent capacitive reactance of the common-mode Y capacitor through the virtual capacitive reactance enhancement mechanism, it can physically use a small-value common-mode Y capacitor that meets the leakage current limit of safety regulations, without increasing its physical capacitance to improve filtering performance, thereby achieving excellent electromagnetic interference suppression performance while meeting safety standards.

[0103] The suppression performance of the proposed hybrid common-mode electromagnetic interference (EMI) filter will be simulated and verified using LTspice software. The common-mode equivalent circuit will be simulated to verify the actual effect of the proposed scheme. Simulation analyses will be performed for five cases: no filter, a passive LC filter, an active negative impedance network, a feedback current sensing and compensation filter, and the proposed hybrid common-mode EMI filter, to verify the effectiveness of the proposed scheme.

[0104] In this simulation, to better reflect actual motor operation, a three-phase sinusoidal modulation wave and a triangular carrier wave are generated using an independent voltage source. The carrier switching frequency is set to 20kHz, the current fundamental frequency is set to 1kHz, the modulation ratio of the three-phase modulation wave is set to 0.8, and the three-phase phase difference is 120°, thus realizing the SPWM modulation strategy. The bus voltage is designed to be 100V. To introduce rise and fall delays in the PWM waveform, an RC low-pass filter is added to the back end of the voltage source, thereby generating a square-like wave with a 50ns buffered rise and fall edge under SPWM modulation. These three square-like waves can then be equivalent to the three-phase pole voltages in a three-phase motor drive system. , and Therefore, the behavioral voltage source can be used again through the formula Common-mode noise sources are generated. The frequency range of concern for conducted EMI is 150kHz-30MHz, so the following focuses on the common-mode EMI suppression effect in this frequency band.

[0105] Simulation Result 1: Simulation results of common-mode electromagnetic interference without adding any filters.

[0106] Figure 4 and 5 The time-domain and frequency-domain plots of common-mode electromagnetic interference (EMI) without any filters are given. It can be concluded that the envelope range of the common-mode noise fluctuation in the time domain is... The maximum common-mode electromagnetic interference (EMI) amplitude in the frequency domain occurs at 295 kHz, reaching -53.376 dBV. Subsequent comparison strategies all aim to reduce EMI noise under this condition; therefore, the results of this simulation serve as an important benchmark.

[0107] Simulation Result 2: Simulation results of common-mode electromagnetic interference with only passive LC filter added

[0108] Based on a comprehensive consideration of factors such as filter cutoff frequency, safety requirements, and inductor size, the common-mode inductor of the passive LC filter was ultimately selected. Equivalent Y capacitance The theoretical cutoff frequency at this point Add the passive LC filter described above to the common-mode equivalent circuit. Figure 6 and 7 The time-domain and frequency-domain plots of the common-mode EMI are given. The envelope range in the time domain is ±28mV; the maximum common-mode EMI amplitude in the frequency domain occurs at 151kHz, reaching -74.351dBV. Both the peak-to-peak value in the time domain and the amplitude in the frequency domain are significantly higher than... Figure 4 and 5 It was attenuated.

[0109] Simulation Result 3: Simulation results of common-mode electromagnetic interference under a filter with only an active negative impedance network added.

[0110] Introducing the secondary inductance of a three-winding current transformer (CT) The negative impedance network has already been analyzed in detail and its parameter design range has been provided previously. The coupling coefficient K of the three-winding current transformer (CT) is taken as an empirical value of 0.98 to simulate a certain leakage inductance. The operational amplifier selected is the Analog Devices LT1363, which has a gain-bandwidth product of 70MHz and a slew rate of 1000V / µs, and its output current can reach over 50mA, sufficient to meet the requirements of this invention.

[0111] Figure 8 and 9 The time-domain and frequency-domain plots of the common-mode EMI are presented. The time-domain envelope range is ±9.6mV; the frequency-domain common-mode EMI spike occurs at 151kHz with an amplitude of -92.513dBV, and at 444kHz with an amplitude of -98.636dBV. The data shows that the proposed negative impedance network effectively improves noise attenuation while maintaining the physical common-mode inductance and capacitance. Based on the above analysis, the common-mode EMI filter with the added active negative impedance network exhibits good suppression performance, but it has certain limitations. As the frequency gradually increases, the parasitic parameters of the inductor will cause inductor deformation, leading to the failure of the negative impedance network. Therefore, the main effective range of this network is generally in the low-frequency band, specifically from 150kHz to a few MHz. Thus, it is still necessary to develop common-mode EMI filter topologies for higher frequencies above a few MHz.

[0112] Simulation Result 4: Simulation results of common-mode electromagnetic interference with only a filter that adds feedback current sensing and current compensation.

[0113] The inverting gain of the operational amplifier is selected to be 10x, and a 100pF parallel capacitor is added to increase the phase margin and improve system stability. Figure 10 and 11 The time-domain and frequency-domain plots of the common-mode EMI are presented. The envelope range in the time domain is ±10.6mV; in the frequency domain, the common-mode EMI spike occurs at 151kHz, with an amplitude of -74.739dBV. The spectrum shows that the active common-mode EMI suppression method using feedback current sensing and compensation effectively reduces common-mode EMI noise in the high-frequency range, but its suppression effect in the low-frequency range is poor. This is entirely consistent with theoretical analysis, because the injected RC network has a large impedance in the low-frequency range, therefore the amplitude of the reverse current compensation in the low-frequency range is very small, almost equivalent to that of a traditional passive filtering scheme; however, in the high-frequency range, the impedance of the injected RC network is very low, thus a higher amplitude level of reverse compensation current can be injected through the three-winding current transformer (CT) and operational amplifier.

[0114] Simulation Result 5: Simulation results of common-mode electromagnetic interference under the proposed hybrid common-mode electromagnetic interference filter.

[0115] The preceding simulations have analyzed in detail the active filter schemes employing common-mode inductor pumping based on a negative impedance network and the active filter scheme enhanced by a common-mode Y-capacitor based on feedback current sensing and compensation. They also detailed how the negative impedance network-based scheme is more suitable for low-frequency bands due to the network's failure at high frequencies, while the feedback current sensing and compensation scheme is more suitable for high-frequency bands due to the high impedance of the injected network at low frequencies. Through analysis... Figure 9 and Figure 11 It can also be observed that both the negative impedance network-based scheme and the feedback current sensing and compensation scheme have their own suitable frequency bands, and their optimal operating frequency bands are complementary. Based on the idea of ​​frequency domain complementarity, and considering that both schemes will use three-winding current transformers (CTs) and operational amplifiers, this simulation attempts to effectively combine the two. This approach leverages the advantages of both while achieving efficient component reuse, enabling effective suppression of common-mode EMI in electric drive systems with lower cost and higher power density.

[0116] Figure 12 and 13The time-domain and frequency-domain plots of the common-mode EMI are presented respectively. The envelope range in the time domain is ±4.1mV; in the frequency domain, the common-mode EMI peak appears at 151kHz with an amplitude of -92.554dBV; and at 3.693MHz, the amplitude reaches -117.144dBV. The spectrum shows that the hybrid common-mode EMI filter based on the proposed invention, which combines common-mode inductive-capacitive enhancement and efficient device multiplexing, exhibits the lowest peak-to-peak values ​​in both the time-domain and frequency-domain peak amplitudes of the common-mode noise waveform, demonstrating its optimal common-mode EMI suppression performance.

[0117] The simulation analyses of the above scenarios strongly demonstrate that the proposed strategy can achieve excellent common-mode EMI suppression by reusing a three-winding current transformer (CT) and operational amplifier, while still using a small-value, small-volume 1mH common-mode inductor and 4.7nF common-mode capacitor. This allows the motor drive system to meet relevant international EMI standards while reducing its size and increasing power density. This verifies the feasibility and effectiveness of the proposed strategy.

[0118] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement, characterized in that, This includes an LC passive common-mode base, a three-winding current transformer (CT), a virtual common-mode inductor pump-up assembly, and a virtual common-mode capacitor enhancement assembly; The LC passive common-mode base includes a common-mode inductor. , and common-mode Y capacitor , It connects between the DC power supply and the motor inverter; The three-winding current transformer (CT) includes two primary windings and a secondary auxiliary winding. The two primary windings reuse the common-mode inductor of the LC passive common-mode base. , The three-winding current transformer (CT) is used to detect common-mode current and cancel differential-mode current, and the secondary auxiliary winding... Simultaneously connect the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component; The virtual common-mode inductor pump-up component is a negative impedance network, connected to the secondary auxiliary winding. Coupling enables the common-mode inductor , Virtual inductive pump-up; used for low-frequency common-mode EMI suppression; The virtual common-mode capacitance enhancement component is a feedback current detection and compensation network that reuses a three-winding current transformer (CT) to enhance the common-mode Y capacitor. , Virtual capacitance enhancement; used for high-frequency common-mode EMI suppression.

2. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 1, characterized in that, The virtual common-mode inductor pump-up assembly includes an inductor. ,resistance ,resistance and the first operational amplifier ; First operational amplifier The non-inverting input terminals are respectively connected to the secondary auxiliary winding. Same-name terminal, resistor One end; First operational amplifier The inverting input terminals are respectively connected to inductors One end, resistor One end; resistance The other end, resistor The other end is connected to the first operational amplifier. Output terminal; Secondary auxiliary winding Heterogeneous terminal, inductor The other end is grounded together; The equivalent impedance of the negative impedance network is: In the formula Represents the Laplace operator; The parameter constraints for virtual inductor pump-up are satisfied: .

3. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 2, characterized in that, The virtual common-mode capacitance enhancement component is a feedback current detection and current compensation network, which includes a multiplexed three-winding current transformer (CT), an inverting proportional amplifier circuit, a push-pull current amplifier circuit, and an RC injection network. The three-winding current transformer (CT) detects the common-mode current and outputs it to the inverting proportional amplifier circuit. The inverting amplifier circuit includes a sampling resistor. Voltage divider resistors Phase compensation capacitor Second operational amplifier The sampling resistor Equivalent impedance of negative impedance network When connected in parallel, they together serve as the auxiliary windings of the secondary side of a three-winding current transformer (CT). The load is used to convert the common-mode current into a voltage signal, which is then passed through a second operational amplifier. The reverse amplification outputs a reverse injection voltage; The push-pull current amplifier circuit includes a push-pull current amplifier transistor. , It receives the reverse injection voltage and expands the circuit to output drive current; The drive signal output from the push-pull current amplifier circuit is then injected through an RC injection network to output a common-mode compensation current with equal amplitude and opposite phase.

4. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 3, characterized in that, The voltage amplification factor of the inverting proportional amplifier circuit satisfy .

5. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 3, characterized in that, The resistor-capacitor injection network includes injection capacitors. Injection capacitor and injection resistance The injected capacitor One end of the injection capacitor is connected to the positive terminal of the DC bus. One end of the injection capacitor is connected to the negative terminal of the DC bus. The other end is connected to the injection capacitor The other end is connected to the injection resistor. Connect the output terminal of the push-pull current amplifier circuit; the impedance of the RC injection network satisfy .

6. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 3, characterized in that, The virtual common-mode inductor pump-up component operates in the low-frequency band of 150kHz to 3.693MHz, while the virtual common-mode capacitor enhancement component operates in the high-frequency band of 3.693MHz to 30MHz. The two frequency bands complement each other and together achieve common-mode EMI suppression across the entire frequency band of 150kHz–30MHz.

7. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 1, characterized in that, By adjusting the sampling resistor The resistance value controls the boundary frequency between the operating frequency bands of the virtual common-mode inductor pump-up component and the virtual common-mode capacitor enhancement component. Low-frequency operating conditions meet Noise suppression is dominated by virtual common-mode inductor pump-up components; High-frequency operating conditions meet Noise suppression is dominated by virtual common-mode capacitor enhancement components.

8. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 1, characterized in that, The common mode inductor , The inductance value is set to a range of 0.5~1.5mH.

9. The hybrid common-mode EMI filter for electric drive systems based on virtual common-mode inductance-capacitance enhancement according to claim 1, characterized in that, The common-mode Y capacitor , The capacitance value is selected to meet the safety regulations for leakage current limits of high-voltage DC buses.

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