Combined power supply filter suitable for high-power frequency conversion working condition

Abstract

The invention provides a combined power supply filter suitable for a high-power frequency conversion working condition, the filter comprises an LCL input filtering assembly, an RC series-parallel damping control assembly and an output filtering assembly, the LCL input filtering assembly is used for filtering a three-phase power supply in an LCL filtering mode to obtain rectifier side current and voltage under different harmonic waves; the RC series-parallel damping control assembly is used for eliminating harmonic waves of current and voltage at the rectifier side by adopting a passive damping mode; the output filtering assembly is used for being placed at the output end of the frequency converter, the rising time of PWM pulses at the output end of the frequency converter can be effectively prolonged, and the change rate of voltage is reduced. The filter provided by the invention meets the harmonic content requirement and the electromagnetic compatibility examination requirement, and effectively inhibits the harmonic content and transmitted interference of a power grid; the LCL resonance risk and the adverse effect are reduced; and motor end overvoltage and bearing current are effectively suppressed.

Description

Technical Field

[0001] The invention belongs to the technical field of power systems, and in particular relates to a combined power supply filter suitable for high-power variable-frequency working conditions. Background Art

[0002] The ship power system is equivalent to a microgrid environment, which is sensitive to the presence of harmonics and places high demands on the harmonic content level of the equipment in the system. As the main power source, the motor plays an important role in the actual engineering application environment. The use of various high-power power electronic devices represented by IGBT has made the AC variable frequency speed regulation system the mainstream of the speed regulation system. In order to convert AC into DC, a rectifier needs to be added to the inverter. The traditional rectifier circuit uses diodes or thyristors, which not only causes a large harmonic content on the AC side and a relatively low power factor, but also the generated harmonics and reactive power will cause the power quality of the power grid to deteriorate or affect other equipment in the power grid. Therefore, how to provide a combined power filter suitable for high-power variable frequency working conditions has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0003] The object of the present invention is to provide a combined power supply filter suitable for high-power variable-frequency working conditions.

[0004] According to the present invention, a combined power supply filter suitable for high-power variable frequency working conditions is provided.

[0005] The filter comprises: an LCL input filter component, an RC series-parallel damping control component and an output filter component, wherein:

[0006] The LCL input filter component is used to filter the three-phase power supply in the form of LCL filtering to obtain the rectifier side current and voltage under different harmonics;

[0007] The RC series-parallel damping control component is used to eliminate the harmonics of the current and voltage on the rectifier side by adopting a passive damping method;

[0008] The output filter component is used to be placed at the output end of the inverter, which can effectively prolong the rise time of the PWM pulse at the output end of the inverter and reduce the voltage change rate.

[0009] Optionally, the first voltage source is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the first inductor Lg, the second end of the first inductor is connected to the first end of the first capacitor, the second end of the first inductor Lg is connected to the first end of the second resistor, the second end of the second resistor is connected to the first end of the second inductor, and the second end of the second inductor is connected to the first voltage branch;

[0010] The second voltage source is connected to the first end of the third resistor, the second end of the third resistor is connected to the first end of the third inductor Lg, the second end of the third inductor is connected to the first end of the second capacitor, the second end of the second inductor Lg is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the first end of the fourth inductor, and the second end of the fourth inductor is connected to the second voltage branch;

[0011] The third voltage source is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the fifth inductor Lg, the second end of the fifth inductor is connected to the first end of the third capacitor, the second end of the third inductor Lg is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the sixth inductor, and the second end of the sixth inductor is connected to the third voltage branch.

[0012] Optionally, the passive damping method specifically includes introducing a damping resistor into the capacitor branch.

[0013] Optionally, the RC series-parallel damping control component includes:

[0014]

[0015] u s Indicates the grid-side voltage on the left, u c Indicates the voltage of each phase input terminal to point O on the grid side, u r represents the grid-side voltage on the right, t represents time, R1 represents the first resistor, R2 represents the second resistor, Lg represents the first inductor, i1 represents the current passing through the resistor R1, and i2 represents the current passing through the resistor R2.

[0016] Optionally, the transfer function of the LCL filter:

[0017]

[0018] Where s represents a complex variable, L represents the grid-side inductance, C f Indicates the grid-side capacitance.

[0019] Optionally, the formula for determining the inductance parameter L is:

[0020]

[0021] in:

[0022] Indicates the power factor angle;

[0023] ω=2*pi*f, f represents the voltage frequency;

[0024] L r =L+L g ——Total reactor value of LCL

[0025] U sm ——Maximum grid phase voltage

[0026] I Tm ——Maximum current on the AC side of a three-phase voltage-type PWM rectifier

[0027] U rm ——The maximum value of the fundamental phase voltage on the AC side of VSR.

[0028] Optionally, the capacitor and resistor transfer function is:

[0029]

[0030] s is a complex variable after conversion to the s domain, R d Represents the damping resistor.

[0031] Optionally, for any one of the three output phases, the transfer function of the RLC filter in the frequency domain is:

[0032]

[0033] Among them, R is the sum of the grid-side equivalent resistance and the inductor equivalent resistance; C represents the du / dt filter capacitor value.

[0034] Optionally, the output filtering component is used for analyzing according to Fourier series, the highest frequency component contained in the PWM pulse depends on the rising slope of the edge of the PWM pulse, and the frequency of the highest frequency component.

[0035] Optionally, the output filter component includes a resistance value that can be calculated based on the PWM pulse voltage rise time.

[0036] The beneficial effects brought by the present invention are as follows:

[0037] It can be seen from the above scheme that the embodiment of the present invention provides a combined power supply filter suitable for high-power variable frequency working conditions, and the filter includes: an LCL input filter component, an RC series-parallel damping control component and an output filter component, wherein: the LCL input filter component is used to filter the three-phase power supply in the form of LCL filtering to obtain the rectifier side current and voltage under different harmonics; the RC series-parallel damping control component is used to eliminate the harmonics of the rectifier side current and voltage by adopting passive damping; the output filter component is used to be placed at the output end of the inverter, which can effectively prolong the rise time of the PWM pulse at the output end of the inverter and reduce the rate of change of the voltage. The filter provided by this application meets the requirements of harmonic content and electromagnetic compatibility assessment, effectively suppresses the harmonic content of the power grid and the transmitted interference; reduces the risk and adverse effects of LCL resonance; and effectively suppresses overvoltage and bearing current at the motor end. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the structure of a combined power supply filter suitable for high-power variable-frequency working conditions provided according to an embodiment;

[0039] Figure 2 An electrical schematic diagram of a main circuit provided according to an embodiment;

[0040] Figure 3 A topological structure diagram of a high-frequency PWM rectifier LCL filter provided according to an embodiment;

[0041] Figure 4 The electrical principle diagram of a single-phase LCL filter provided according to an embodiment;

[0042] Figure 5 is a block diagram of LCL filtering control provided according to an embodiment;

[0043] Figure 6 FIG. 4 is a diagram of an LCL equivalent circuit provided according to an embodiment.

[0044] Figure 7 Schematic diagram of du_dt filtering principle provided according to an embodiment. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Reference Figure 1 , shows a schematic diagram of the structure of a combined power filter suitable for high-power variable frequency working conditions of the present application, the filter includes: an LCL input filter component 101, an RC series-parallel damping control component 102 and an output filter component 103, wherein:

[0047] The LCL input filter component 101 is used to filter the three-phase power supply in the form of LCL filtering to obtain the current and voltage on the rectifier side under different harmonics;

[0048] The RC series-parallel damping control component 102 is used to eliminate the harmonics of the current and voltage on the rectifier side by adopting a passive damping method;

[0049] The output filter component 103 is used to be placed at the output end of the inverter, which can effectively prolong the rise time of the PWM pulse at the output end of the inverter and reduce the voltage change rate.

[0050] Taking the 55kW power level inverter in the embodiment of the present application as an example, in order to meet the harmonic content requirements and electromagnetic compatibility assessment requirements, a combined filter suitable for this high-power frequency conversion working condition is designed, which mainly includes the following parts:

[0051] 1) LCL input filter component; 2) RC series and parallel damping control component; 3) du_dt output filter component.

[0052] The following combines formula calculations and actual engineering applications to determine the device selection of the three-part combined filter, which is used for the configuration and selection of inverter filters with similar power levels and usage scenarios.

[0053] Another embodiment of the present application further supplements the combined power supply filter suitable for high-power variable-frequency working conditions provided in the above embodiment.

[0054] like Figure 3 As shown, optionally, the first voltage source U sa is connected to the first end of the first resistor R1, and the second end of the first resistor R1 is connected to the first inductor L g1 The first end is connected to the first inductor L g1 The second end of the first capacitor C f1 The first end of the first inductor L g1 The second end of the second resistor R2 is connected to the first end of the second inductor L, and the second end of the second inductor L1 is connected to the first voltage branch U ra connected;

[0055] The second voltage source U sb The first end of the third resistor R3 is connected to the second end of the third resistor R3. g2 The first end is connected to the third inductor L g2 The second end of the second capacitor C f2 The first end is connected to the second inductor L g2 The second end of the fourth resistor R4 is connected to the first end of the fourth inductor L2, and the second end of the fourth inductor L2 is connected to the second voltage branch U rb connected;

[0056] The third voltage source U sc The first end of the fifth resistor R5 is connected to the first end of the fifth resistor R5, and the second end of the fifth resistor R5 is connected to the fifth inductor L g3 The first end is connected to the fifth inductor L g3 The second end of the third capacitor C f3 The first end is connected to the third inductor L g3The second end of the sixth resistor R6 is connected to the first end of the sixth inductor L3, the second end of the sixth inductor L3 is connected to the third voltage branch U rc connected.

[0057] The LCL input filter components specifically include:

[0058] The 55kW power level inverter of the present application embodiment adopts a three-phase PWM voltage type rectification strategy, and its main circuit diagram is as follows: Figure 2 .

[0059] where u sk is the grid-side voltage, i k Indicates the current of each phase on the grid side, u rk It represents the voltage of each phase input terminal on the grid side to point O, k=a, b, c; L is the grid side inductance, and R is the sum of the grid side equivalent resistance and the inductor equivalent resistance.

[0060] The topology of the high frequency PWM rectifier LCL filter is shown in Figure 3 .

[0061] From the structural analysis of the LCL filter of the single-phase PWM rectifier, see Figure 4 As shown, where:

[0062]

[0063] Corresponding to LCL filtering, its control block diagram is as follows Figure 5 shown.

[0064] The transfer function is:

[0065]

[0066] When Lg=1.2mH, L=4.9mH, Cf=1.8uF, the corresponding resonant angular frequency is 24007rad / s.

[0067] The equivalent circuit of LCL filter under h harmonic is as follows Figure 6 shown.

[0068] Among them, i2(h) and ur(h) are the current and voltage on the rectifier side under the hth harmonic, and i1(h) and us(h) represent the harmonic current and voltage on the grid side under the hth harmonic.

[0069] The formula for determining the inductance parameter L is:

[0070]

[0071] L T =L+L g ——Total reactor value of LCL

[0072] U sm ——Maximum grid phase voltage

[0073] I Tm ——Maximum current on the AC side of a three-phase voltage-type PWM rectifier

[0074] U rm ——The maximum value of the fundamental phase power on the AC side of VSR

[0075] Optionally, the passive damping method specifically includes introducing a damping resistor into the capacitor branch.

[0076] Optionally, the RC series-parallel damping control component includes:

[0077]

[0078] u s is the grid side voltage, and Uc is the voltage of each phase input terminal on the grid side to point O.

[0079] Specifically, because the capacitor branch in the LCL filter has a third-order system order, it brings trouble to the design of the control system. In practice, the resonance problem must be solved. Use passive damping (introducing damping resistors into the capacitor branch) and adopt capacitor and resistor methods.

[0080] The transfer function of the capacitor and resistor is:

[0081]

[0082] Optionally, the transfer function of the LCL filter:

[0083]

[0084] Optionally, the formula for determining the inductance parameter L is:

[0085]

[0086] Among them: du / dt filter is placed at the output end of the inverter, which can effectively extend the rise time of the PWM pulse at the output end of the inverter, reduce the rate of change of voltage, and play a good role in protecting the insulation of the motor. The circuit structure of LRC du / dt filter is as follows Figure 7 shown.

[0087] For any of the three output phases, the transfer function of the RLC filter in the frequency domain is:

[0088]

[0089] The filter can effectively attenuate the frequency components above ωc. According to Fourier series analysis, the highest frequency component contained in the PWM pulse depends on the rising slope of the edge of the PWM pulse and the frequency of the highest frequency component. Reasonable selection of filter parameters and filtering out a part of the high-frequency components of the PWM pulse can effectively extend the rise time of the PWM pulse and reduce du / dt.

[0090] The resistance value can be calculated based on the PWM pulse voltage rise time (the optimal damping system is 0.707).

[0091] L T =L+L g ——Total reactor value of LCL

[0092] U sm ——Maximum grid phase voltage

[0093] I Tm ——Maximum current on the AC side of a three-phase voltage-type PWM rectifier

[0094] U rm ——The maximum value of the fundamental phase voltage on the AC side of VSR.

[0095] Optionally, the capacitor and resistor transfer function is:

[0096]

[0097] Optionally, for any one of the three output phases, the transfer function of the RLC filter in the frequency domain is:

[0098]

[0099] Optionally, the output filtering component is used for analyzing, according to Fourier series, the highest frequency component contained in the PWM pulse depends on the rising slope of the edge of the PWM pulse, and the frequency of the highest frequency component.

[0100] Optionally, the output filter component includes a resistance value that can be calculated based on the PWM pulse voltage rise time.

[0101] For example, the switching frequency (3.9kHz), rated input voltage (three-phase AC380V), rated output power (55kW) of the main circuit and related harmonic content requirements of the switching device are determined, the filtering parameters are calculated according to the formula, and the device selection is completed by referring to the product manual, as follows:

[0102] 1)LCL filter component: 400uH+420uF+400uF

[0103] 2) Capacitor and resistor components: 10nF safety capacitor + 80kΩ15W resistor

[0104] 3) du_dt components: 120Ω800W resistor + 100uH inductor + 1.5uf safety capacitor.

[0105] The beneficial effects brought by the present invention are as follows:

[0106] It can be seen from the above scheme that the embodiment of the present invention provides a combined power supply filter suitable for high-power variable frequency working conditions, and the filter includes: an LCL input filter component, an RC series-parallel damping control component and an output filter component, wherein: the LCL input filter component is used to filter the three-phase power supply in the form of LCL filtering to obtain the rectifier side current and voltage under different harmonics; the RC series-parallel damping control component is used to eliminate the harmonics of the rectifier side current and voltage by adopting passive damping; the output filter component is used to be placed at the output end of the inverter, which can effectively prolong the rise time of the PWM pulse at the output end of the inverter and reduce the rate of change of the voltage. The filter provided by the present application meets the requirements of harmonic content and electromagnetic compatibility assessment, effectively suppresses the harmonic content of the power grid and the transmitted interference; reduces the risk and adverse effects of LCL resonance; and effectively suppresses overvoltage and bearing current at the motor end.

[0107] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0108] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0109] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0110] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0111] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0112] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0113] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0115] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard drives, ROM, RAM, magnetic disks, or optical disks.

[0116] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0117] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A combined power supply filter suitable for high-power frequency conversion conditions, characterized in that: The filter comprises: an LCL input filter component, an RC series-parallel damping control component and an output filter component, wherein: The LCL input filter component is used to filter the three-phase power supply in the form of LCL filtering to obtain the rectifier side current and voltage under different harmonics; The RC series-parallel damping control component is used to eliminate the harmonics of the current and voltage on the rectifier side by adopting a passive damping method; The output filter component is used to be placed at the output end of the inverter, which can effectively prolong the rise time of the PWM pulse at the output end of the inverter and reduce the voltage change rate.

2. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 1 is characterized in that: The first voltage source is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the first inductor Lg, the second end of the first inductor is connected to the first end of the first capacitor, the second end of the first inductor Lg is connected to the first end of the second resistor, the second end of the second resistor is connected to the first end of the second inductor, and the second end of the second inductor is connected to the first voltage branch; The second voltage source is connected to the first end of the third resistor, the second end of the third resistor is connected to the first end of the third inductor Lg, the second end of the third inductor is connected to the first end of the second capacitor, the second end of the second inductor Lg is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the first end of the fourth inductor, and the second end of the fourth inductor is connected to the second voltage branch; The third voltage source is connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the fifth inductor Lg, the second end of the fifth inductor is connected to the first end of the third capacitor, the second end of the third inductor Lg is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the first end of the sixth inductor, and the second end of the sixth inductor is connected to the third voltage branch.

3. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 1 is characterized in that: The passive damping method specifically includes introducing a damping resistor into the capacitor branch.

4. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 1 is characterized in that: The RC series-parallel damping control component comprises: u s Indicates the grid-side voltage on the left, u c Indicates the voltage of each phase input terminal to point O on the grid side, u r represents the grid-side voltage on the right, t represents time, R1 represents the first resistor, R2 represents the second resistor, Lg represents the first inductor, i1 represents the current passing through the resistor R1, and i2 represents the current passing through the resistor R2.

5. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 4 is characterized in that: The transfer function of LCL filtering is: Where s represents a complex variable, L represents the grid-side inductance, C f Indicates the grid-side capacitance.

6. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 5 is characterized in that: The formula for determining the inductance parameter L is: in: Indicates the power factor angle; ω=2πf, f represents the voltage frequency; L r =L+L g ——Total reactor value of LCL U sm ——Maximum grid phase voltage I Tm ——Maximum current on the AC side of a three-phase voltage-type PWM rectifier U rm ——The maximum value of the fundamental phase electricity on the AC side of VSR.

7. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 6 is characterized in that: The transfer function of the capacitor and resistor is: Among them, s is the complex variable after conversion to s domain, R d Represents the damping resistor.

8. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 6 is characterized in that: For any of the three output phases, the transfer function of the RLC filter in the frequency domain is: Among them, R is the sum of the grid-side equivalent resistance and the inductor equivalent resistance; C represents the du / dt filter capacitor value.

9. The combined power supply filter suitable for high-power variable frequency working conditions according to claim 7 is characterized in that: The output filter component is used for analyzing according to Fourier series that the highest frequency component contained in the PWM pulse depends on the rising slope of the edge of the PWM pulse, and the frequency of the highest frequency component.

10. The combined power supply filter suitable for high-power frequency conversion working conditions according to claim 8, characterized in that: The output filter component includes a resistance value that can be calculated based on the PWM pulse voltage rise time.

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