Power balance droop control system for frequency converter of coal mining machine

Abstract

The embodiment of the invention provides a coal cutter frequency converter power balance droop control system, and relates to the technical field of coal cutter frequency converter control. A power balance droop control system for a frequency converter of a coal mining machine comprises the frequency converter of the coal mining machine, a power supply input module, a rectification module, a filtering module, a capacitance storage module, an inversion module, a droop control module and a detection feedback module, the direct current is smoothly filtered through the filtering module, the filtered direct current is stored in the capacitance storage module, the inversion module receives a frequency control signal of the droop control module, inverts the direct current into alternating current and outputs the alternating current to a motor of the frequency converter of the coal mining machine, and the droop control module comprises a droop controller, a driving circuit and a signal processing circuit. Compared with a traditional linear control mode, droop control can make control response within milliseconds, and the dynamic performance of power regulation is greatly improved.

Description

Technical Field

[0001] This application relates to the technical field of shearer frequency converter control, and more specifically, to a power balance droop control system for a shearer frequency converter. Background Art

[0002] A shearer frequency converter is a frequency conversion device used to control the movement of a shearer motor. Its main structure consists of three parts: a rectifier, an intermediate DC link, and an inverter. The system first rectifies three-phase alternating current into direct current through the rectifier and stores it on the intermediate DC bus composed of capacitors. Then, it is converted into three-phase alternating current with adjustable frequency and voltage through the inverter and output to drive the shearer motor. The rotational speed of the shearer motor is adjusted by controlling the output frequency of the inverter to meet the speed requirements of the shearer under different working conditions.

[0003] Traditional shearer frequency converters mostly adopt a vector control system with voltage and current double closed loops. Among them, the outer loop is a voltage loop, which stabilizes the DC bus voltage through a PI regulator; the inner loop is a current loop, which makes the motor terminal current accurately follow the given current value. However, this control method has complex parameter design and there is a problem of motor parameter drift, resulting in poor stability and dynamic performance. When the motor load changes, large impact currents are likely to occur, which is not conducive to the stable operation of the drive system.

[0004] Droop control is a non-linear control strategy. Its basic idea is to construct a "drooping" non-linear switching surface in the state space, so that the system state point slides on this surface to achieve the control purpose. Droop control adjusts the shape of the control surface in real time according to the current state of the system and can adapt to system parameter changes. Compared with linear control, droop control has advantages such as strong anti-disturbance ability and large stable control amplitude.

[0005] Droop control does not require an accurate system model and realizes adaptive control through discrete detection of the system state. It can effectively suppress the impact of external load mutations on the system and enhance the anti-interference ability of the frequency converter. Compared with traditional frequency converter control, the application of droop control can simplify the controller design, improve the dynamic response speed, and better meet the control requirements of the shearer frequency converter.

[0006] In view of the control performance problems existing in the shearer frequency converter, a new control scheme for the shearer frequency converter is proposed in order to obtain better control effects and enhance the adaptability and stability of the frequency converter. Summary of the Invention

[0007] This application aims to at least solve the technical problem of the control performance problems existing in the shearer frequency converter in the prior art. For this purpose, this application proposes a power balance droop control system for a shearer frequency converter.

[0008] The power balance droop control system of the shearer frequency converter according to the embodiment of the present application includes a shearer frequency converter, a power input module, a rectification module, a filtering module, a capacitor storage module, an inversion module, a droop control module, and a detection feedback module. The power input module accesses three-phase alternating current, rectifies the three-phase alternating current into direct current through the rectification module, smooths the direct current through the filtering module, stores the filtered direct current in the capacitor storage module after filtering. The inversion module receives the frequency control signal of the droop control module and inverses the direct current into alternating current for output to the motor of the shearer frequency converter. Among them, the droop control module includes a droop controller, a drive circuit, and a signal processing circuit. The droop controller is built with a droop control algorithm model to calculate the system state and generate a control quantity in real time. The detection feedback module collects current and voltage feedback signals, processes them, and sends them to the droop control module to complete feedback control.

[0009] Further, the filtering module uses an input filter, and the input filter includes at least one inductor and at least one capacitor, and the inductor and the capacitor are electrically connected to filter out high-frequency noise and interference in the power supply grid.

[0010] Further, when the rectification module outputs DC voltage fluctuations, it provides buffering through the DC bus module.

[0011] Further, the droop control module further includes a data acquisition module, a power calculation module, a droop control algorithm model, and a PWM drive module;

[0012] The data acquisition module is connected to the detection sensor to collect current and voltage data;

[0013] The power calculation module calculates the grid input power and the motor output power based on the sampled data;

[0014] The droop control algorithm model generates a control quantity;

[0015] The PWM drive module outputs a PWM wave to control the inverter.

[0016] Further, the droop control module further includes constructing a droop switching surface and designing a dead zone for the power error at the same time. When the error exceeds the dead zone, the system switches to the droop surface, and the droop controller calculates the control quantity on the surface in real time, which is amplified and used as the frequency control quantity of the inverter to adjust the output power and control the error within the dead zone.

[0017] Further, the droop control algorithm model adopts an incremental PID structure, and the specific algorithm is as follows:

[0018] uc = uc(k - 1) + ekp + ekiTs + kd(e - e(k - 1)) / Ts

[0019] Among them, uc is the control quantity, e is the power error, and kp, ki, and kd are control parameters.

[0020] Furthermore, the inverter module adopts a three-phase bridge inverter circuit composed of IGBTs, receives the frequency control signal of the droop control module, and converts direct current into alternating current for output.

[0021] Furthermore, the detection and feedback module uses current sensors and voltage sensors to collect the electrical parameter signals at various points in the system.

[0022] Furthermore, the droop control module further includes a sliding mode variable structure controller, which is used to realize the automatic switching of the output power control surface and the speed control algorithm.

[0023] Furthermore, the sliding mode variable structure controller executes the following steps:

[0024] The key state parameters of the shearer frequency converter and its motor system are monitored in real time through the detection and feedback module:

[0025] The monitored state parameters are compared with the preset thresholds to determine whether the system is in a stable state;

[0026] If the system state exceeds the preset threshold, it indicates that the current droop control strategy can no longer effectively maintain the system stability. At this time, the sliding mode variable structure controller will be automatically activated. The sliding mode variable structure controller selects an appropriate control surface and control algorithm according to the current state of the system. According to the selected control surface and control algorithm, the sliding mode variable structure controller calculates the corresponding control quantity and outputs it to the inverter module through the PWM drive module to adjust the output of the inverter and achieve precise control of the shearer frequency converter.

[0027] The beneficial effects of this application are as follows: By adopting the droop control strategy, high-precision control of the power balance of the shearer frequency converter is achieved. Compared with the traditional linear control method, the droop control can make a control response within milliseconds, greatly improving the dynamic performance of power regulation. At the same time, the droop control surface continuously approaches the state point, which can effectively suppress the influence of external load disturbances on the system and enhance the anti-interference ability. The droop control can adapt to changes in external conditions by real-time detecting the system state without relying on accurate system parameters, greatly reducing the requirements for system modeling and parameter identification, simplifying the controller design. By designing different droop switching surfaces, the system state can be restricted to move near the ideal equilibrium state, reducing the overshoot risk and increasing the stability margin. This ensures that when the shearer is under varying loads, the frequency converter can still respond quickly and stably. Compared with the complex vector control system, the droop controller in this solution is simple and intuitive in design, which is beneficial to engineering application and promotion, reducing the implementation difficulty and usage cost. The improvement of the power balance performance of the frequency converter can reduce the negative impact on the operation of the shearer, improve the working smoothness, avoid the mechanical failure risk caused by out-of-control power conversion, and is beneficial to improving the coal mining efficiency and safety.

[0028] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is the overall structural flowchart of the power balance droop control system of the shearer frequency converter according to the embodiment of the present application;

[0031] Figure 2 is the structural flowchart of the droop control module according to the embodiment of the present application;

[0032] Figure 3 is the structural flowchart of the detection and feedback module according to the embodiment of the present application;

[0033] Figure 4 is the hardware topology diagram of the control system according to the embodiment of the present application;

[0034] Figure 5 is the structural diagram of the droop controller according to the embodiment of the present application;

[0035] Figure 6It is a schematic three-dimensional structure diagram of a shearer frequency converter according to an embodiment of the present application;

[0036] Figure 7 It is a schematic side view of the structure of a shearer frequency converter according to an embodiment of the present application.

[0037] Icon: 10, shearer frequency converter. Specific embodiments

[0038] Next, the technical solutions in the embodiments of the present application will be described with reference to the accompanying drawings in the embodiments of the present application.

[0039] To make the purpose, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0040] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0041] It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0042] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0044] In this application, unless otherwise clearly specified and defined, terms such as "installed", "connected", "linked", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0045] In this application, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and diagonally above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes the first feature being directly below and diagonally below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0046] Next, a power balance droop control system for a shearer frequency converter according to an embodiment of this application will be described with reference to the accompanying drawings.

[0047] As Figures 1 - 7 shown, the shearer frequency converter 10 according to the embodiment of this application droop-controls power balance, and includes a shearer frequency converter 10, a power input module, a rectification module, a filtering module, a capacitor storage module, an inversion module, a droop control module, and a detection feedback module, and energy conversion and information transmission are realized through electrical connections between the modules.

[0048] Among them, the power input module accesses three-phase alternating current. The power input module includes a circuit breaker, an electromagnetic contactor, an input filter, and a surge protection device. The power input module is not just a simple interface, but a combination of a group of devices and technologies designed to ensure the safety, reliability, and purity of the power supply. These devices work together to provide a stable three-phase alternating current power supply for the subsequent rectification, filtering, and inversion processes.

[0049] Three-phase alternating current is rectified into direct current by a rectification module. The direct current is smoothed by a filtering module and stored in a capacitor storage module after filtering. The filtering module uses an input filter, which includes at least one inductor and at least one capacitor. The inductor and the capacitor are electrically connected to filter out high-frequency noise and interference in the power supply grid. The rectification module is usually implemented by using a diode rectifier bridge or a thyristor (SCR) rectifier. The most common diode rectifier bridge is the six-pulse rectifier bridge, which consists of six diodes and can effectively convert three-phase alternating voltage into a pulsating direct voltage. The thyristor rectifier provides more flexible control options compared to the diode rectifier bridge, allowing adjustment of the output voltage level. The filtered direct current is fed into the capacitor storage module, where the capacitor not only smooths the voltage but also provides additional energy support when the load suddenly increases, avoiding voltage dips. To effectively cope with load changes, electrolytic capacitors with a large capacitance are usually selected.

[0050] In the shearer frequency converter 10 system, after the rectification module converts three-phase alternating current into direct current, the output direct voltage may fluctuate. To ensure that the inverter module can receive a stable and smooth direct current power supply, a DC bus module (also known as the DC bus or DC-link) is usually set between the rectification module and the inverter module to provide the functions of buffering and smoothing the voltage. Specifically, the rectified direct current is fed into the DC bus module, which mainly consists of a group of large-capacity electrolytic capacitors. These capacitors are connected in parallel on the DC bus to store energy and smooth the voltage. When the load suddenly changes (such as the motor starting or stopping), the voltage on the DC bus may rise or fall briefly. At this time, the capacitor can quickly absorb the excess electrical energy or release the stored energy, thereby reducing the voltage fluctuation. Under normal operating conditions, the DC bus capacitor not only stores enough energy to cope with possible load mutations but also provides additional energy support when the grid voltage fluctuates, helping to maintain a stable direct voltage supply to the inverter module. Usually, the DC bus module is also equipped with a voltage sensor to monitor the voltage level on the DC bus in real time and feed this information back to the control system. If the detected voltage exceeds the set range, the control system can take corresponding measures, such as adjusting the operating state of the rectifier or triggering the protection mechanism.

[0051] The inverter module receives the frequency control signal from the droop control module and converts the direct current into alternating current to output to the motor of the shearer frequency converter 10.

[0052] The inverter module adopts a three-phase bridge inverter circuit composed of IGBTs, receives the frequency control signal from the droop control module, and converts the direct current into alternating current for output.

[0053] Among them, the droop control module includes a droop controller, a drive circuit, and a signal processing circuit. The droop controller has a built-in droop control algorithm model to calculate the system state in real time and generate a control quantity. The detection feedback module collects current and voltage feedback signals, processes them, and sends them to the droop control module to complete feedback control.

[0054] The droop control module further includes a data acquisition module, a power calculation module, a droop control algorithm model, and a PWM drive module;

[0055] The data acquisition module is connected to detection sensors to collect current and voltage data;

[0056] The data acquisition module first needs to be connected to current sensors and voltage sensors. These sensors are usually installed at key nodes, such as the DC bus and the inverter output terminal. The sensors convert the collected current and voltage signals into electrical signals and transmit them to the data acquisition module. The data acquisition module performs analog-to-digital conversion (ADC) on the received analog signals and converts them into digital signals for subsequent processing.

[0057] The power calculation module calculates the grid input power and the motor output power based on the sampled data;

[0058] The power calculation module receives current and voltage data from the data acquisition module.

[0059] The droop control algorithm model generates a control quantity;

[0060] The droop control algorithm model receives data of the grid input power and the motor output power from the power calculation module. Based on the received power data and a preset target value, it uses an incremental PID control algorithm or other suitable control strategies to generate a control quantity. This control quantity is used to adjust the frequency or voltage output of the inverter to achieve power balance.

[0061] The droop control algorithm model adopts an incremental PID structure, and the specific algorithm is as follows:

[0062] uc = uc(k - 1) + ekp + ekiTs + kd(e - e(k - 1)) / Ts

[0063] Among them, uc is the control quantity, e is the power error, and kp, ki, and kd are control parameters.

[0064] After repeated debugging, when kp = 0.8, ki = 0.05, and kd = 0.1 are selected, a better control effect is obtained.

[0065] The PWM drive module outputs a PWM wave to control the inverter.

[0066] The PWM drive module receives the generated control quantity from the droop control algorithm model. According to the received control quantity, the PWM drive module generates the corresponding PWM waveform to control the operation of the IGBT switch, thereby adjusting the frequency and voltage of the inverter output. The generated PWM waveform is sent to the inverter to control the characteristics and quality of the output three-phase alternating current.

[0067] The droop control module also includes constructing a droop switching surface for the power balance subsystem. This surface represents the ideal power balance state. According to the droop control principle, the control surface continuously and adaptively approaches the current state point. A droop controller is designed to calculate the control quantity in real time, driving the system state point to slide towards the droop surface to achieve the purpose of tracking the ideal power balance state.

[0068] At the same time, a dead zone for the power error is designed. When the error exceeds the dead zone, the system switches to the droop surface. The droop controller calculates the control quantity on the surface in real time, which is amplified and used as the frequency control quantity of the inverter to adjust the output power and control the error within the dead zone.

[0069] Adopting the droop control strategy, without the need for an accurate system model, it improves the stability and dynamic response performance of the frequency converter power control through adaptive control, effectively suppresses the influence of the load on the system, and enhances the anti-interference ability.

[0070] The droop control module also includes a sliding mode variable structure controller, which is used to realize the automatic switching of the output power control surface and the speed control algorithm.

[0071] The sliding mode variable structure controller executes the following steps:

[0072] The key state parameters of the shearer frequency converter 10 and its motor system are monitored in real time through the detection and feedback module:

[0073] The monitored state parameters are compared with the preset thresholds to judge whether the system is in a stable state;

[0074] If the system state exceeds the preset threshold, it indicates that the current droop control strategy can no longer effectively maintain the system stability. At this time, the sliding mode variable structure controller will be automatically started. The sliding mode variable structure controller selects an appropriate control surface and control algorithm according to the current state of the system. According to the selected control surface and control algorithm, the sliding mode variable structure controller calculates the corresponding control quantity and outputs it to the inverter module through the PWM drive module to adjust the output of the inverter, realizing the precise control of the shearer frequency converter 10.

[0075] The detection and feedback module uses current sensors and voltage sensors to collect the electrical parameter signals at various points in the system.

[0076] In summary: The rectifier module converts three-phase alternating current into direct current, which is filtered and stored in the capacitor. The inverter module receives the frequency control signal from the droop controller, converts the direct current into alternating current and outputs it to the motor. The droop controller collects the current and voltage feedback signals, calculates the input and output power of the capacitor module and the power balance state, and adjusts the output frequency of the inverter module in real time according to the droop control algorithm to balance the input and output power and achieve stable control of the frequency converter. The droop switching surface of the power balance subsystem is constructed, which represents the ideal power balance state. According to the droop control principle, the control surface continuously and adaptively approaches the current state point. The droop controller is designed to calculate the control quantity in real time and drive the system state point to slide towards the droop surface to achieve the purpose of tracking the ideal power balance state.

[0077] The above are only embodiments of the present application and are not used to limit the protection scope of the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0078] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, and all should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. The power balance droop control system of the coal mining machine inverter is characterized by: It includes a coal mining machine inverter, a power input module, a rectifier module, a filter module, a capacitor storage module, an inverter module, a droop control module and a detection feedback module. The power input module is connected to three-phase AC power, and the three-phase AC power is rectified into DC power by the rectifier module. The DC power is smoothed and filtered by the filter module, and the DC power is stored in the capacitor storage module after filtering. The inverter module receives the frequency control signal of the droop control module, inverts the DC power into AC power and outputs it to the motor of the coal mining machine inverter. Among them, the droop control module includes a droop controller, a drive circuit, and a signal processing circuit. The droop controller has a built-in droop control algorithm model to calculate the system state and generate control quantity in real time. The detection feedback module collects current and voltage feedback signals, and sends them to the droop control module after processing to complete feedback control.

2. The power balance droop control system for a coal mining machine frequency converter according to claim 1 is characterized in that: The filtering module adopts an input filter, which includes at least one inductor and at least one capacitor. The inductor and the capacitor are electrically connected to filter out high-frequency noise and interference in the power supply grid.

3. The power balance droop control system for the coal mining machine inverter according to claim 2 is characterized in that: When the rectifier module outputs DC power fluctuations, the DC bus module provides buffering.

4. The power balance droop control system for a coal mining machine inverter according to claim 1 is characterized in that: The droop control module also includes a data acquisition module, a power calculation module, a droop control algorithm model and a PWM drive module; The data acquisition module is connected to the detection sensor to collect current and voltage data; The power calculation module calculates the grid input power and the motor output power based on the sampled data; The droop control algorithm model generates a control variable; The PWM driving module outputs a PWM wave to control the inverter.

5. The power balance droop control system for the coal mining machine inverter according to claim 4 is characterized in that: The droop control module also includes constructing a droop switching surface and designing a dead zone of the power error. When the error exceeds the dead zone, the system switches to the droop surface. The droop controller calculates the control amount on the surface in real time and amplifies it as the frequency control amount of the inverter to adjust the output power and control the error within the dead zone.

6. The power balance droop control system for the coal mining machine inverter according to claim 5 is characterized in that: The droop control algorithm model adopts an incremental PID structure, and the specific algorithm is as follows: uc=uc(k-1)+ekp+ekiTs+kd(ee(k-1)) / Ts Among them, uc is the control quantity, e is the power error, kp, ki, kd are the control parameters.

7. The power balance droop control system for a coal mining machine inverter according to claim 1 is characterized in that: The inverter module adopts a three-phase bridge inverter circuit composed of IGBTs, receives a frequency control signal from a droop control module, and inverts direct current into alternating current for output.

8. The power balance droop control system for a coal mining machine inverter according to claim 1, characterized in that: The detection feedback module uses current sensors and voltage sensors to collect electrical parameter signals at various points in the system.

9. The power balance droop control system for the coal mining machine inverter according to claim 5, characterized in that: The droop control module also includes a sliding mode variable structure controller, which is used to realize automatic switching of the output power control surface and the speed control algorithm.

10. The power balance droop control system for the coal mining machine inverter according to claim 9, characterized in that: The sliding mode variable structure controller performs the following steps: The key status parameters of the coal mining machine inverter and its motor system are monitored in real time through the detection feedback module: Compare the monitored status parameters with the preset thresholds to determine whether the system is in a stable state; If the system state exceeds the preset threshold, it indicates that the current droop control strategy can no longer effectively maintain system stability. At this time, the sliding mode variable structure controller will automatically start. The sliding mode variable structure controller selects the appropriate control surface and control algorithm according to the current state of the system. Based on the selected control surface and control algorithm, the sliding mode variable structure controller calculates the corresponding control quantity and outputs it to the inverter module through the PWM drive module to adjust the output of the inverter and achieve precise control of the coal mining machine frequency converter.

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