Novel active adaptability control method for railway vehicle power grid

Abstract

The invention relates to the technical field of rail transit electrical control, in particular to a novel railway vehicle power grid active adaptability control method which comprises the steps that the switching frequency of a grid-side electric energy conversion unit is adjusted, and the harmonic content of input current is adjusted; the grid-side electric energy conversion unit adopts a voltage and current double-closed-loop control structure; a current loop in the grid-side electric energy conversion unit adopts a PIR controller, and active adaptability of a railway vehicle power grid is achieved. According to the invention, the switching frequency of the grid-side electric energy conversion unit is dynamically switched according to the actual harmonic condition of the power grid current, the effective suppression of the power grid current harmonic is realized in the full frequency range, the application matching of the railway vehicle and the power grid can be better improved, and the harmonic content of the power grid is reduced.

Description

Technical Field

[0001] This invention relates to the field of railway electrical control technology, and in particular to a novel active adaptive control method for railway vehicle power grids. Background Technology

[0002] Railway traction locomotives and EMUs typically employ four-quadrant rectifiers as grid-side power conversion units. This enables bidirectional energy flow and unity power factor control, effectively meeting the operational requirements of the vehicles. The input current quality of the grid-side power conversion unit directly affects its own performance and is also directly related to the power quality of the power grid. Therefore, harmonic control of the input current is of great significance. Summary of the Invention

[0003] To address the aforementioned technical problems, a novel active adaptive control method for railway vehicles and power grids is provided. This invention dynamically switches the switching frequency of the grid-side power conversion unit based on the actual harmonic characteristics of the power grid current, effectively suppressing power grid current harmonics across the entire frequency range. This significantly improves the operational compatibility between railway vehicles and the power grid, and reduces the harmonic content of the power grid.

[0004] The technical means employed in this invention are as follows: A novel active adaptive control method for railway vehicle power grids includes: adjusting the switching frequency of a grid-side power conversion unit to adjust the harmonic content of the input current; the grid-side power conversion unit adopts a voltage and current dual closed-loop control structure; the current loop in the grid-side power conversion unit uses a PIR controller to achieve active adaptation of the railway vehicle power grid.

[0005] Furthermore, the adjustment of the switching frequency of the grid-side power conversion unit specifically includes: setting a target switching frequency and determining whether the current switching frequency is the target switching frequency; if the current switching frequency is the target switching frequency, the adjustment is completed; if the current switching frequency is not the target switching frequency, a flag bit of the target switching frequency is set, the flag bit of the current switching frequency is stored, the phase-locked loop parameters and carrier controller parameters under the target switching frequency are initialized, and marked as the first process flag position for further adjustment of the switching frequency.

[0006] Furthermore, the further adjustment of the switching frequency specifically includes: updating the PIR current controller parameters and the grid phase compensation angle according to the flag bit of the target switching frequency and the flag bit of the current switching frequency, and marking them as the second process flag position; updating the PIR current controller parameters and the grid phase compensation angle according to the flag bit of the target switching frequency, and marking them as the third process flag position; initializing and updating the PIR current controller parameters and the grid phase compensation angle according to the flag bit of the target switching frequency, and marking them as the process flag position, thus completing the adjustment of the switching frequency.

[0007] Furthermore, the grid-side power conversion unit adopts a voltage and current dual closed-loop control structure, specifically including: the voltage loop of the grid-side power conversion unit is the outer loop, the current loop is the inner loop, and the modulation wave output by the current loop is compared with a fixed frequency triangular carrier wave to obtain a pulse signal with a fixed switching frequency.

[0008] Furthermore, the PIR controller comprises two parts: a PR controller and a current controller.

[0009] Furthermore, the current controller uses different control parameters when operating at different switching frequencies. When dynamically switching the switching frequency of the grid-side power conversion unit, the controller parameters need to be dynamically adjusted to ensure a smooth transition of the input current and intermediate voltage during switching.

[0010] Compared with the prior art, the present invention has the following advantages: This invention provides a novel active adaptive control method for railway vehicle power grids. Based on the actual harmonic characteristics of the grid current, it dynamically switches the switching frequency of the grid-side power conversion unit, effectively suppressing grid current harmonics across the entire frequency range. This invention optimizes the quality of the input current to the grid-side power conversion unit and improves control performance.

[0011] This invention can effectively reduce the harmonic content of grid current and improve the power quality of the grid; it can smoothly realize the switching frequency switching of grid-side power conversion units, reduce the input current surge during switching, and ensure stable system operation. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of the switching frequency adjustment process of the grid-side power conversion unit in this invention.

[0014] Figure 2 This is a schematic diagram of the PIR current controller structure in this invention.

[0015] Figure 3 This is a waveform diagram illustrating the switching frequency from 450Hz to 1050Hz in an embodiment of the present invention.

[0016] Figure 4 This is a waveform diagram illustrating the switching frequency from 1050Hz to 450Hz in an embodiment of the present invention.

[0017] Figure 5 This is a block diagram of a fast current control algorithm in the prior art. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0023] like Figure 1 As shown, this invention provides a novel active adaptive control method for railway vehicle power grids, comprising: adjusting the switching frequency of the grid-side power conversion unit to adjust the harmonic content of the input current; in a preferred embodiment of this invention, a target switching frequency is set, and it is determined whether the current switching frequency is the target switching frequency; if the current switching frequency is the target switching frequency, the adjustment is completed; if the current switching frequency is not the target switching frequency, a flag bit of the target switching frequency is set, the flag bit of the current switching frequency is stored, the phase-locked loop parameters and carrier controller parameters under the target switching frequency are initialized, and marked as the first process flag position for further adjustment of the switching frequency.

[0024] In a specific implementation, as a preferred embodiment of the present invention, the PIR current controller parameters and the grid phase compensation angle are updated according to the flag bit of the target switching frequency and the flag bit of the current switching frequency, and marked as the second process flag position; the PIR current controller parameters and the grid phase compensation angle are updated according to the flag bit of the target switching frequency, and marked as the third process flag position; the PIR current controller parameters and the grid phase compensation angle are initialized and updated according to the flag bit of the target switching frequency, and marked as the process flag position, thus completing the adjustment of the switching frequency.

[0025] The grid-side power conversion unit adopts a dual closed-loop control structure of voltage and current. In a preferred embodiment of this invention, the voltage loop of the grid-side power conversion unit is the outer loop, and the current loop is the inner loop. The modulated wave (a 50Hz sinusoidal wave) output by the current loop is compared with a fixed-frequency triangular carrier wave (a triangular wave that is an integer multiple of 50Hz) to obtain a pulse signal with a fixed switching frequency. Adjusting the switching frequency is actually adjusting the frequency of the triangular carrier wave.

[0026] The current loop in the grid-side power conversion unit employs a PIR controller to achieve active adaptation of the railway vehicle power grid. In a preferred embodiment of this invention, the PIR controller comprises two parts: a PR controller and a current controller. The structure of the PIR controller is as follows: Figure 2 As shown.

[0027] In specific implementation, as a preferred embodiment of the present invention, the control parameters used by the current controller are different when operating at different switching frequencies. When dynamically switching the switching frequency of the grid-side power conversion unit, the controller parameters need to be dynamically adjusted to ensure a smooth transition of the input current and intermediate voltage during switching.

[0028] Example Existing technologies incorporate notch filters into control algorithms to suppress current harmonics, thereby reducing grid-side current harmonics, minimizing their pollution to the power grid, and improving power quality.

[0029] Fast current algorithm control structure such as Figure 5 As shown, its control structure includes a voltage loop and a current loop. The control objective of the voltage loop is to control the DC bus voltage to reach a given command voltage. The difference between the specified voltage and the actual bus voltage is passed through a PI controller, and the output of the PI controller serves as the command current given by the current loop. The output of the voltage loop, the phase-locked loop, the actual input current, the grid voltage signal, and the PI controller constitute the current loop, which tracks the command current output by the voltage loop to achieve unity power factor control. The output of the current loop is passed through a modulation unit to obtain PWM pulses, which are used to turn on and off the IGBT power devices, thereby realizing the PWM rectification function.

[0030] Harmonics in the grid-side current are the main source of harmonic pollution in the traction power supply network. Assuming the traction power supply network has no harmonics, the grid-side voltage... and grid-side current They are defined as follows:

[0031]

[0032] in, This represents the effective value of the fundamental frequency of the grid-side voltage. This represents the effective value of the fundamental frequency of the grid-side current. The angle between the fundamental voltage and fundamental current of the grid side. This is the angular frequency of the grid-side voltage.

[0033] The input power of a single-phase four-quadrant circuit can then be expressed as:

[0034] The input power of a single-phase four-quadrant circuit consists of steady-state components. and dynamic components It consists of two parts.

[0035] Based on the main circuit topology of a single-phase four-quadrant circuit, the output power of the single-phase four-quadrant circuit can be expressed as:

[0036] in, and DC side voltage The average and fluctuation values, Load current The average value.

[0037] According to the law of conservation of energy, the instantaneous power on the input side and the instantaneous power on the output side of a single-phase four-quadrant circuit should be equal, therefore:

[0038] As shown in the above equation, the DC-side voltage contains a pulsation of twice the grid frequency, i.e., a 100Hz pulsation component. According to the fast current control algorithm, this second-harmonic pulsation component will be introduced into the voltage loop. When a current command is input into the current loop, a third-harmonic pulsation component is introduced into the control. Because of the second-harmonic pulsation in the DC voltage, the grid-side current introduces the third harmonic, as well as the fifth and seventh harmonics accordingly. Therefore, suppressing the introduction of the second-harmonic pulsation into the control loop can suppress the content of the third, fifth, and seventh harmonics.

[0039] Therefore, the shortcomings of existing technology are: (1) It is only effective for eliminating specific harmonics and cannot achieve harmonic elimination across the entire frequency range.

[0040] (2) As the number of specific harmonics to be eliminated increases, the order of the corresponding transfer function also increases, the structure of the transfer function becomes more complex, and the discretized program becomes more complex.

[0041] This invention can adjust the harmonic content of the input current by adjusting the switching frequency of the grid-side power conversion unit. The lower the switching frequency, the higher the harmonic content of the input current and the worse the sinusoidal property. The higher the switching frequency, the lower the harmonic content of the input current and the better the sinusoidal property.

[0042] have Figure 3 and Figure 4 It can be seen that in the switching strategy and concept of this invention, the input current and intermediate voltage are in a stable state, and there is no obvious impact.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel active adaptive control method for railway vehicle power grids, characterized in that, include: The switching frequency of the grid-side power conversion unit is adjusted to regulate the harmonic content of the input current. The grid-side power conversion unit adopts a dual closed-loop control structure for voltage and current. The current loop in the grid-side power conversion unit uses a PIR controller to achieve active adaptability of the railway vehicle power grid.

2. The novel active adaptive control method for railway vehicle power grids according to claim 1, characterized in that, The adjustment of the switching frequency of the grid-side power conversion unit specifically includes: Set the target switching frequency and determine whether the current switching frequency is the target switching frequency. If the current switching frequency is the target switching frequency, the adjustment is completed. If the current switching frequency is not the target switching frequency, set the flag bit of the target switching frequency, store the flag bit of the current switching frequency, initialize the phase-locked loop parameters and carrier controller parameters under the target switching frequency, and mark it as the first process flag position for further adjustment of the switching frequency.

3. The novel active adaptive control method for railway vehicle power grids according to claim 2, characterized in that, The further adjustment of the switching frequency specifically includes: Based on the flag bits of the target switching frequency and the current switching frequency, update the PIR current controller parameters and the grid phase compensation angle, and mark them as the second process flag position; based on the flag bits of the target switching frequency, update the PIR current controller parameters and the grid phase compensation angle, and mark them as the third process flag position; based on the flag bits of the target switching frequency, initialize and update the PIR current controller parameters and the grid phase compensation angle, and mark them as the process flag position, thus completing the adjustment of the switching frequency.

4. The novel active adaptive control method for railway vehicle power grids according to claim 1, characterized in that, The grid-side power conversion unit adopts a voltage and current dual closed-loop control structure, specifically including: The voltage loop of the grid-side power conversion unit is the outer loop, and the current loop is the inner loop. The modulated wave output by the current loop is compared with a fixed-frequency triangular carrier wave to obtain a pulse signal with a fixed switching frequency.

5. The novel active adaptive control method for railway vehicle power grids according to claim 1, characterized in that, The PIR controller consists of two parts: a PR controller and a current controller.

6. The novel active adaptive control method for railway vehicle power grids according to claim 5, characterized in that, The current controller uses different control parameters when operating at different switching frequencies. When dynamically switching the switching frequency of the grid-side power conversion unit, the controller parameters need to be dynamically adjusted to ensure a smooth transition of input current and intermediate voltage during switching.

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