Power supply filtering topology and frequency converter thereof

Abstract

In order to solve the problem that the existing power conversion system inevitably generates external interference current or voltage, the utility model provides a power supply filtering topology and a frequency converter thereof, which comprise a common mode inductor connected in series with a main power supply cable, and a filtering module consisting of a plurality of devices between the common mode inductor and a load end, one end of the filtering module is connected with the power line and the other end is grounded. According to the utility model, different current paths and suppression methods are designed mainly from the characteristics of the interference current of the equipment, so that the influence of the interference current of the equipment on the filter is reduced. And due to the addition of the attenuation resistor, the generation of resonance can be inhibited, the design requirement of the filter inductor is reduced, and the applicability of the filter is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field especially is related to a power filter topology and frequency converter thereof. BACKGROUND

[0002] In the drive system or other power conversion system, due to the equipment will output or produce high-low alternation change work voltage, it is inevitable to produce the interference current or voltage to outside. In order to suppress interference, reduce the influence to power grid and environment, it is a kind of more suitable choice to give relevant equipment supporting input power filter structure.

[0003] In actual use, due to the use scene of relevant power or drive and other equipment is various, is influenced by temperature, power and the working frequency of equipment itself, has strict requirement to its supporting filter to avoid the resonance of filter or other application beyond the design specification of filter, thereby causes the failure of filter, and even produces negative influence.

[0004] At present, the design of power filter generally adopts LC (inductance-capacitance combination) filter topology structure, and in addition to considering the attenuation of electromagnetic noise of filter, the various working frequencies of the equipment using filter and the interference frequency existing in the use site are also considered to avoid the possible filter resonance and other problems. So that it is difficult to select the inductance and capacitance of the basic elements of filter. At the same time, due to the requirement of filter basic device to environmental conditions, the application scene or performance of equipment is limited.

[0005] In order to solve the above problems, the Chinese utility model patent with patent No. CN220156498U proposes an elevator EMI power filter circuit, which comprises a first phase line, a second phase line, a third phase line, a zero line, a first resistor, a second resistor, a third resistor, a first inductor, a second inductor, a third inductor, a fourth inductor, a fifth inductor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor and a tenth capacitor. But in order to avoid filter saturation in a larger range, larger filter inductance and larger filter capacitance need to be selected. For the selection of filter devices, larger devices mean higher cost and larger product volume. But larger devices cannot avoid the generation of LC resonance, only the resonance point is shifted to other frequencies. In some special environments, resonance may still occur. UTILITY MODEL CONTENT

[0006] The utility model mainly solves the problem that the power conversion system in the prior art will inevitably produce interference current or voltage to outside, and provides a power filter topology and frequency converter thereof.

[0007] The above technical problems of the utility model are solved through the following technical scheme:

[0008] A power filter topology, comprising a source end and a load end connected by a three-wire circuit, a common-mode inductor connected to the three-wire circuit, the three-wire circuit between the common-mode inductor and the load end being electrically connected to one end of an X capacitor group and a Y capacitor group, and the other end of the X capacitor group and the Y capacitor group being connected to a ground wire.

[0009] As a preferred scheme, the X capacitor group comprises a first X capacitor, a second X capacitor and a third X capacitor connected in parallel.

[0010] As a preferred scheme, the X capacitor group is connected to the ground wire through a first Y capacitor group and a second Y capacitor group connected in parallel.

[0011] As a preferred scheme, the first Y capacitor group comprises a first Y capacitor and a first diode connected in series, and the second Y capacitor group comprises a second Y capacitor and a second diode connected in series, so that when interference current is generated, the diodes can quickly absorb the current into the Y capacitor group.

[0012] As a preferred scheme, the first diode is connected in parallel with a first resistor, and the second diode is connected in parallel with a second resistor, so that when the output voltage is stable, the charge stored in the first Y capacitor can be discharged through the resistor, thereby achieving the purpose of suppressing oscillation to avoid unstable operation of the filter caused by oscillation current.

[0013] As a preferred scheme, the first diode and the second diode are opposite in direction, so that when the output voltage suddenly changes to a negative level, the direction of the interference current will be opposite, at which time the second Y capacitor replaces the first Y capacitor to play a main charging and discharging role, and the principle is the same as described above.

[0014] As a preferred scheme, a voltage clamping device is arranged between the middle connection points of the first Y capacitor group and the second Y capacitor group.

[0015] As a preferred scheme, the first diode and the second diode are opposite in direction, so that when the output voltage suddenly changes to a negative level, the direction of the interference current will be opposite, at which time the second Y capacitor replaces the first Y capacitor to play a main charging and discharging role, and the principle is the same as described above.

[0016] A frequency converter, comprising a rectifier and an inverter connected through a three-wire circuit, a common mode inductor is connected to the three-wire circuit, one end of the three-wire circuit between the common mode inductor and a load is electrically connected with an X capacitor group, the other end of the X capacitor group is connected with a first Y capacitor group and a second Y capacitor group, and the other end of the first Y capacitor group and the second Y capacitor group is connected with a ground wire.

[0017] Therefore, the power supply filter topology has the advantages that:

[0018] The scheme is mainly based on the characteristics of the interference current of the equipment itself, and reasonable current paths and suppression methods are designed, so that the influence of the equipment on the filter under different working conditions can be reduced, the requirements for the basic elements of the filter are reduced, the applicability of the filter is improved, and the anti-interference performance of the product is improved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of the power supply filter topology of the utility model.

[0020] Figure 2 is a comparison of the suppression effect of the interference current flowing through the common mode inductor when the utility model is in oscillation.

[0021] Figure 3 is a schematic diagram of the current direction when the interference current is generated in the utility model.

[0022] Figure 4 is a schematic diagram of the interference current direction when the output voltage is stable in the utility model. DETAILED DESCRIPTION

[0023] The technical scheme of the utility model will be further specifically explained below by means of embodiments and in combination with the drawings.

[0024] Embodiment one:

[0025] The utility model is to avoid the dilemma that the filter design has to choose larger or more expensive inductors, capacitors and other filter devices in order to meet the requirements of more extensive equipment use, and provides a power supply filter topology and a frequency converter. Through the scheme, under the same conditions, the interference current through the common mode inductor is reduced, and the interference energy is attenuated, so that the filter inductor is more difficult to saturate and fail, and the filter is prevented from entering the LC oscillation environment. Avoid the reduction or failure of the LC filter effect. Expand the applicability of the filter and expand the use scenarios of the final equipment.

[0026] The utility model provides a power filter topology, including source end and load end through three -wire circuit connection, the common mode inductance is connected on three -wire circuit, and the common mode inductance and load end between three -wire circuit with X capacitor group and one end of Y capacitor group electric connection, and the other end of X capacitor group and Y capacitor group is connected ground wire, the utility model discloses in order to avoid the predicament that filter design has to select larger or more expensive inductance, capacitor and other filter devices in order to satisfy more extensive equipment use requirement, under the same condition, reduce the interference current through the common mode inductance through the utility model, and the interference energy is attenuated simultaneously, thereby make filter inductance more difficult saturation failure, and avoid filter into LC oscillation environment, avoid LC filter effect reduction, or failure, expand filter applicability, expand final equipment use scene.

[0027] The filter structure is explained by a three-wire filter topology. In actual use, a two-wire case can be adapted by using a two-wire common mode inductor and deleting one X capacitor.

[0028] In actual use, a four-wire case can also be adapted by using a four-wire common mode inductor and adding a set of X capacitors, or directly connecting the neutral line in the four-wire to the X capacitor group and the first Y capacitor group, and the second Y capacitor group connection point.

[0029] The X capacitor group includes a first X capacitor, a second X capacitor, and a third X capacitor connected in parallel. Their functions are multifaceted. First, they are used to suppress oscillation of the filter, which is crucial for maintaining system stability. Second, the X capacitor group can effectively prevent saturation of the common mode inductor, which helps reduce interference current and improve overall system reliability. Additionally, the X capacitor group can also handle abnormal excitation high voltage, protecting the system from potential damage. The X capacitor group is connected to the ground through a first Y capacitor group and a second Y capacitor group connected in parallel. The Y capacitor group plays a role in balancing and stabilizing the system, which is beneficial for improving the system's anti-interference ability and stability. By carefully designing and reasonably configuring the X capacitor group and the Y capacitor group, voltage surges or interference signals that may occur in the system can be effectively prevented, ensuring the effective operation of the power filter.

[0030] In summary, the existence and reasonable application of the X capacitor group and the Y capacitor group bring many benefits to the power filter topology system, including but not limited to oscillation suppression, common mode inductor saturation prevention, abnormal excitation high voltage protection, anti-interference ability improvement, and system stability enhancement. These measures help ensure the reliability and stability of the power filter in complex working environments, thereby improving the service life and performance of the final equipment.

[0031] The first Y capacitor group includes a first Y capacitor and a first diode arranged in series, and the second Y capacitor group includes a second Y capacitor and a second diode arranged in series, so that when interference current is generated during conversion, the diodes can quickly absorb the current into a group of Y capacitors, and this fast response characteristic is crucial for maintaining system stability, as it effectively prevents interference current from further spreading throughout the system, thereby reducing the impact on the outside world, but this is not all, the first diode is connected in parallel with a first resistor, and the second diode is connected in parallel with a second resistor, so that when idle, that is, when the output voltage is stable, the charge stored in the first Y capacitor can be discharged through the resistor, thereby achieving the purpose of suppressing oscillation, and this mechanism ensures that there is no oscillation current to cause the filter to work unstably in the normal working state of the system. By reasonably setting the values of the capacitors and resistors, the frequency and amplitude of the oscillation can be effectively controlled, thereby further improving the stability and performance of the system.

[0032] The first Y capacitor group and the second Y capacitor group in the power filter topology have multiple functions. They not only quickly absorb interference current generated during conversion, but also discharge charge through the resistor when the system is idle, thereby achieving oscillation suppression and ensuring system stability and reliability. The cleverness of this design is that multiple functions are integrated together to form an efficient and stable power filter system, providing reliable power support for equipment in complex working environments.

[0033] The first diode and the second diode are in opposite directions, which means they can effectively handle interference current when the output voltage suddenly changes to a negative level. For the output voltage to suddenly change to a negative level, the direction of the interference current will be reversed, and at this time the second Y capacitor replaces the first Y capacitor to play the main charge and discharge role. This design principle is similar to the one described earlier, which stabilizes the system by charging and discharging the capacitor, thereby ensuring that the filter system can effectively function when the output voltage changes positively or negatively.

[0034] In addition, the first diode and the second diode are connected in parallel with a supplementary capacitor at both ends. This arrangement further enhances the system's ability to absorb interference current and improves the system's response speed. By connecting small-value Y capacitors in parallel, the system's filtering effect can be more flexibly adjusted to adapt to different working environments and power quality.

[0035] The positions of the added diodes, resistors, and supplementary capacitors can be interchanged. This means that when designing a power filter system, the layout and connection of components can be flexibly adjusted according to specific needs and actual conditions to achieve optimal performance and stability.

[0036] Overall, this flexible design makes the power filter system more adaptable and adjustable. By reasonably configuring the position and connection method of the components, fine control of the system can be achieved, thereby better meeting the needs of different scenarios. This design idea not only improves the stability and anti-interference ability of the system, but also provides engineers with more design options and optimization space.

[0037] A voltage clamping device Rd, such as a TVS, a voltage-dependent resistor, etc., is provided between the middle connection points of the first Y capacitor group and the second Y capacitor group. By selecting an appropriate clamping voltage, the reliability of the filter structure can be improved without affecting the filter effect.

[0038] A frequency converter using the above power filter topology circuit includes a rectifier and an inverter connected by a three-wire circuit. A common-mode inductor is connected to the three-wire circuit. The three-wire circuit between the common-mode inductor and the load end is electrically connected to one end of the X capacitor group. The other end of the X capacitor group is connected to the first Y capacitor group and the second Y capacitor group. The other end of the first Y capacitor group and the second Y capacitor group is connected to the ground. A first capacitor is connected between the two-wire circuits.

[0039] The circuit can be used as a filter structure for a frequency converter. The rectifier and inverter circuits are connected at the back end of the circuit. By adjusting appropriate parameters, the overall filter effect can be obtained.

[0040] This scheme is mainly based on the characteristics of the device's own interference current. By designing a reasonable current path and using effective suppression methods, the influence of the device on the filter under different working conditions is reduced. This measure aims to reduce the requirements for the basic components of the filter, thereby improving the applicability and performance stability of the filter. Among them, according to the characteristics of the device's own interference current, we carefully designed the current path to effectively reduce the influence on the filter, thereby improving the reliability and stability of the overall system.

[0041] In addition, the attenuation resistor added in the scheme also plays an important role. It not only effectively suppresses the generation of resonance, but also reduces the external electromagnetic emission of related products, and further improves the anti-interference performance of the product. By reasonably configuring and selecting the attenuation resistor, we successfully reduce the resonance phenomenon in the system, effectively improving the electromagnetic compatibility and stability of the overall product. This improvement not only makes the product more easily meet the electromagnetic compatibility requirements, but also provides stronger protection for its application in complex electromagnetic environments.

[0042] In summary, the design concept and implementation scheme of the present scheme fully consider the characteristics of the interference current of the device itself, and successfully reduce the influence of the device on the filter, improve the applicability and stability of the filter through reasonable current path design, effective suppression method and the addition of attenuation resistance and other means. At the same time, the scheme also effectively suppresses the resonance phenomenon, reduces the electromagnetic emission of the product, and improves the anti-interference performance of the product, which provides strong support for the stability and reliability in actual application scenarios.

[0043] Embodiment two:

[0044] For example, when the frequency converter device, when the output voltage waveform of the frequency converter becomes positive voltage, due to the existence of output cable and load capacitance to ground, with the output voltage mutation, a sharp current will be generated. As shown in Figure 3 The total current generated in this process is I0, in the case of adapting the filter of the present design, the return current is divided into three parts, I1 through the second diode and the second Y capacitor path, I2 through the first resistance and the first Y capacitor, and the common-mode current I3 returned through the power supply. When the output voltage becomes negative, a sharp current in the opposite direction will be generated, that is, when the frequency converter works, positive and negative interference currents will be generated, and the idle state when the output voltage does not change.

[0045] When the frequency converter output voltage changes and generates interference current, the diode can quickly absorb the current into a group of Y capacitors, and at the same time in the idle state, that is, when the output voltage is stable, as shown in Figure 4 The charge stored in the second Y capacitor can be discharged through the absorption resistance R, so as to achieve the purpose of suppressing oscillation, so as to avoid the occurrence of oscillation current causing the filter to work unstably.

[0046] When the output voltage mutation is negative, the above interference current direction will be opposite, at this time the first Y capacitor replaces the second Y capacitor to play the role of main charging and discharging, the principle is the same as the above section, which will not be repeated here.

[0047] The absorption resistance R needs to be selected with a suitable value, so as to neither attenuate too slowly, nor consume as much interference energy as possible. Here the initial value is recommended as:

[0048]

[0049] Where L is the inductance value of the common-mode inductance Lcm, and C is the series capacitance value of the three X capacitors and a group of Y capacitors.

[0050] C=3Cx / / Cy1

[0051] Then according to the actual frequency converter, load and other conditions, make certain adjustment, so that the attenuation speed and attenuation size of the energy absorbed by the capacitor reach a suitable level.

[0052] In the filter, the common-mode inductance saturation current can be approximately described by the following formula:

[0053]

[0054] Where Bsat is the saturation flux of the magnetic ring used by the common-mode inductance, l is the equivalent magnetic path length of the magnetic ring, n is the number of turns of the inductance, μ e is the relative permeability, μ r is the vacuum permeability. It can be seen that, compared with a general filter, when using the same common-mode inductance and filter parameters, and under the condition of the same load, part of the current is forced to be consumed on the resistor, the current flowing through the common-mode inductance is reduced, so that the inductance is more difficult to enter the saturation state, and the heating of the magnetic core is reduced, avoiding problems such as excessive temperature rise leading to reduction of inductance value. Conversely, under the condition of similar current, using the present scheme can reduce the saturation flux requirement of the magnetic core, or reduce the equivalent magnetic path length of the magnetic core, and can reduce the material requirement of the magnetic core or use smaller magnetism, thereby achieving the effect of reducing the cost and volume of the magnetic core.

[0055] At the same time, due to the damping effect of the resistor in the LC loop, the oscillation current of the LC loop will be smaller when the next output voltage conversion process comes. By selecting a suitable damping resistor R, the LC filter system can be prevented from entering an oscillation state at certain specific noise frequencies. Thus, problems such as core saturation, heating, abnormal voltage, and abnormal sound caused by LC oscillation are avoided.

[0056] Under the same filter parameters, when the frequency converter is working at a certain frequency, the general LC structure enters an oscillation state, and a periodic peak current appears. At this time, if the common-mode inductance magnetic core is not properly selected, it will easily enter a saturation failure state. However, due to the presence of the damping resistor R, the current waveform through the common-mode inductance is relatively stable and has a smaller amplitude during the rectification period in the LC structure using the present design.

[0057] Figure 2 is the LC filter structure using the present utility model and the same parameters, and the size of the interference current flowing through the common-mode inductance when the system oscillates under the operating condition of a specific carrier frequency of the frequency converter. The larger current is the current flowing through the common-mode inductance in the LC filter structure, and the smaller current is the current flowing through the common-mode inductance under the condition of the present utility model.

[0058] The specific embodiments described in the present document are merely illustrative of the spirit of the present utility model. Those skilled in the art to which the present utility model belongs can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, without deviating from the spirit of the present utility model or exceeding the scope defined by the appended claims.

Claims

1. A power filter topology, characterized by, The application relates to a three-wire circuit, which comprises a source end and a load end connected by a three-wire circuit, wherein a common mode inductor is connected to the three-wire circuit, the three-wire circuit between the common mode inductor and the load end is electrically connected to one end of an X capacitor group and a Y capacitor group, and the other end of the X capacitor group and the Y capacitor group is connected to a ground wire.

2. A power filtering topology according to claim 1, characterized in that, The X capacitor group comprises a first X capacitor, a second X capacitor and a third X capacitor connected in parallel.

3. A power filtering topology according to claim 1 or 2, characterized in that, A first Y capacitor group and a second Y capacitor group are connected in parallel between the X capacitor group and the ground wire.

4. A power filtering topology according to claim 3, wherein, The first Y capacitor group comprises a first Y capacitor and a first diode connected in series, and the second Y capacitor group comprises a second Y capacitor and a second diode connected in series.

5. A power filtering topology according to claim 4, wherein, A first resistor is connected in parallel to the first diode, and a second resistor is connected in parallel to the second diode.

6. A power filtering topology according to claim 4, wherein, The first diode and the second diode are oppositely directed.

7. A power filtering topology according to claim 6, wherein, A voltage clamping device is arranged between the middle connection points of the first Y capacitor group and the second Y capacitor group.

8. A power filtering topology according to claim 6, wherein, Supplementary capacitors are connected in parallel to the two ends of the first diode and the second diode respectively.

9. A frequency converter adapted for use in the power filter topology of any one of claims 1 to 8, characterized in that The application also relates to a three-wire circuit, which comprises a rectifier and an inverter connected by a three-wire circuit, wherein a common mode inductor is connected to the three-wire circuit, the three-wire circuit between the common mode inductor and a load end is electrically connected to one end of an X capacitor group, the other end of the X capacitor group is connected to a first Y capacitor group and a second Y capacitor group, and the other end of the first Y capacitor group and the second Y capacitor group is connected to a ground wire.

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