High-power active variable inductor for speed-adjustable driver and control method of high-power active variable inductor

Abstract

The invention relates to the field of power electronic converter control, and discloses a high-power active variable inductor for a speed-adjustable driver and a control method thereof.The high-power active variable inductor comprises a positive inductor and a negative inductor, the positive inductor is a traditional physical inductor, and the negative inductor is obtained through equivalence of a single-phase inverter; by connecting the positive inductor and the negative inductor in parallel, the overall equivalent inductance value is increased, and meanwhile, a wider-range adjusting space is provided, so that a better filtering effect is achieved, the equivalent inductance value can be adjusted in a wide range, the power density is high, implementation is easy, three-phase imbalance can be dealt with, the electric energy quality of a speed-adjustable driver is improved, and the service life of a direct-current side filtering capacitor is prolonged; the problems that a direct-current side passive filter of an existing speed-adjustable driver is heavy, the inductance size of an active capacitor is difficult to reduce, and the adjusting range of an existing active inductor is narrow are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter control, and discloses a high-power active variable inductor for adjustable speed drivers and its control method. Background Technology

[0002] Adjustable Speed ​​Drives (ASDs) comprise an economical three-phase diode bridge rectifier, DC-DC link filter, and three-phase inverter. They are currently widely used in motor speed control, offshore oil drilling, and other fields. Due to limited space in modern industrial plants, the demand for high-power-density drives is increasing. In specific fields such as offshore drilling, subsea power systems, and maritime transport, design requirements are particularly stringent, and the economic benefits of weight reduction and capacity reduction are substantial. Industry leaders have launched specialized drive product lines with smaller size and lighter weight designs to precisely meet the needs of industrial applications.

[0003] On the DC side of the adjustable speed driver, passive LC filters are bulky, heavy, and expensive, significantly impacting overall system performance—a situation contrary to industry optimization goals. A solution is to suppress line current harmonics by using a large DC link magneto-inductor and to limit DC link voltage fluctuations by configuring a large-capacity DC capacitor. The DC link capacitor employs a dual-series design to increase voltage levels, and then a dual-parallel structure to achieve a large capacity. The magneto-inductor selection is based on power grid specifications and DC link ripple limit standards, but the overall structure is relatively bulky.

[0004] Furthermore, using large-capacity inductors and electrolytic capacitors can lead to issues with the size, stability, and reliability of the DC link. Under normal operating conditions of a three-phase balanced grid, the DC link capacitors and inductors can effectively filter out harmonic components six times the fundamental frequency, thereby stabilizing the DC voltage. However, when the grid voltage is unbalanced, harmonics twice the fundamental frequency will appear in the DC link, and these harmonics will be further amplified by the resonant magnetoinductor and energy storage capacitor. This unexpected oscillation phenomenon can cause DC link voltage instability, leading to electrolytic capacitor and inverter-level failures.

[0005] Therefore, considering factors such as power density, voltage and current ripple limitations, dynamic response capability, maintenance energy requirements, and overall grid-connected drive system stability, there are currently three main approaches: using ultra-thin drivers with thin-film capacitors configured only in the DC link, active capacitors, and active inductors.

[0006] The first type of approach employs an ultra-thin driver with thin-film capacitors configured only in the DC link, aiming to reduce size, weight, and cost while improving the reliability of the adjustable speed driver. However, significant fluctuations in the DC link voltage not only pose challenges to inverter-level control and modulation but also exacerbate the electrothermal stress on the switching devices.

[0007] The second approach is to replace the existing DC link capacitor with an advanced active capacitor. This active capacitor, constructed from power electronic circuitry, can simulate the electrical characteristics of a large-capacity electrolytic capacitor to stabilize the DC link voltage. However, because a large inductor is needed to suppress the inrush current during rectifier startup, this active capacitor connected in parallel to the DC link cannot effectively reduce the size of the DC-side filter inductor.

[0008] The third approach involves designing active inductors to replace magnetic inductors. Similar to active capacitors, using power electronic circuits to represent traditional physical inductors effectively reduces size and weight. Since the inductor is connected in series with the DC link, it can simultaneously sharpen the mains current and stabilize the DC link. Unlike traditional DC link inductors, active inductors completely eliminate the reliance on magnetic materials.

[0009] For active inductors, there are currently two approaches: The first is a two-port active inductor. Its core idea is to achieve the inductor's filtering function through harmonic compensation. Specifically, a digital filter extracts harmonics from the physical inductor, and then a single-phase inverter generates a current with the same amplitude but opposite phase as the harmonics to cancel them out. During operation, its equivalent inductance remains constant, thus only increasing power density and lacking good dynamic performance to cope with harsh conditions such as three-phase voltage imbalance. The second approach uses the equivalent active inductor of a single-phase inverter, directly connected in series in the DC link of a variable-speed driver. This active inductor topology is comparable to a small inductor in terms of weight and size, but achieves a higher unit inductance value, while the inductance value is flexibly adjustable, thus ensuring that the DC current ripple is suppressed to a fixed value. However, the inductance adjustment range of this approach is limited, and it cannot effectively suppress the second harmonic when the three-phase voltage imbalance intensifies. Summary of the Invention

[0010] The purpose of this invention is to provide a high-power active variable inductor and its control method for adjustable speed drivers. It has a wider range of adjustment space, thereby achieving better filtering effect. It can adjust the equivalent inductance value over a wide range, has high power density and is easy to implement. It can cope with three-phase imbalance, improve the power quality of adjustable speed drivers, and extend the life of DC side filter capacitors.

[0011] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows: A high-power active variable inductor for a speed-adjustable driver, comprising a positive inductance negative inductance DC power supply capacitor The DC power supply capacitor Parallel connection in negative inductor The DC side; the negative inductor Including single-phase inverters and filter inductors The single-phase inverter and the filter inductor Series connection to form an equivalent negative inductance Used to adjust the negative inductance The inductance value makes the parallel positive inductors and negative inductance The overall feel value is adjustable.

[0012] Furthermore, the single-phase inverter includes four switching transistors, namely the first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor All four switching transistors are insulated-gate bipolar transistors, wherein: The gates of the four switching transistors are connected to the gate drive control signal. Power diodes are connected in parallel across the two ends of each of the four switching transistors. The collector of each switching transistor is connected to the negative terminal of the diode, and the emitter of each switching transistor is connected to the positive terminal of the diode. First switching transistor and the third switching transistor Series connection, and the first switching transistor The emitter is connected to the third switching transistor. The collector; the second switching transistor and the fourth switching transistor Series connection, and the second switch The emitter is connected to the fourth switching transistor. The collector of the first switching transistor; The collector is connected to the second switching transistor. The collector of the third switching transistor The emitter is connected to the fourth switching transistor. The emitter; DC power supply capacitor Both ends are connected to the first switching transistor. collector and third switching transistor The emitter, the second switching transistor The collector is connected to the DC power supply capacitor. The positive terminal, the fourth switching transistor The emitter is connected to the DC power supply capacitor. The negative electrode; The positive inductor The two ports are respectively ports and Port, filter inductor One end is connected to the first switching transistor The emitter of one end is connected to the positive inductor as a port of the negative inductor. The ports are connected, the Port and fourth switch The collectors are connected.

[0013] Furthermore, it also includes an MCU controller, a PI controller, and an AD converter; the AD converter includes a first AD converter, a second AD converter, and a third AD converter; the first AD converter is connected to the negative inductor. Connection used to acquire negative inductance The current is measured and converted into a first digital signal; a second analog-to-digital converter is used to acquire the positive inductance. The voltage signal between the two ports is converted into a second digital signal; the third AD analog-to-digital converter is used to convert the DC power supply capacitor The analog voltage signals at both ends are converted into a third digital signal; The PI controller is used to receive the third digital signal and perform negative inductance based on the third digital signal. The adjustment of the virtual resistance makes the DC side voltage... The deviation from the voltage reference value is within a preset first deviation range; The MCU controller is used to receive the first digital signal and the second digital signal, and generate a negative inductance based on the current ripple in the active variable inductor. The sensing value; and the virtual resistance adjusted by the PI controller. Generate and adjust negative inductance The control signal for the sensing value.

[0014] To achieve the above-mentioned technical effects, the present invention also provides a control method for a high-power active variable inductor for a speed-adjustable driver. This control method, based on the aforementioned high-power active variable inductor, includes: Step 1: Real-time acquisition of negative inductance DC side voltage negative inductance Port voltage and negative inductance Current Analysis to obtain DC side voltage The first difference between the voltage and the preset voltage reference value; Step 2: Based on the first difference, adjust the negative inductor using a PI controller. A virtual resistor is used to compensate for negative inductance losses, making the DC-side voltage... The deviation from the voltage reference value is within a preset first deviation range; Step 3: Real-time acquisition of current in the parallel main circuit of the active variable inductor Extracting current Current ripple According to current ripple Compared with the preset current ripple reference value The second difference between them is adjusted using an MCU controller to control the negative inductance. The inductance value makes the current ripple Compared with the preset current ripple reference value The second difference between them is within the preset second deviation range.

[0015] Furthermore, in step 2, the PI controller adjusts the negative inductor. The virtual resistance target value is ,in For the virtual resistance target value, This is the reference value for the DC power supply capacitor voltage on the DC side. The proportional parameter of the PI controller, These are the integral parameters of the PI controller. It is a complex frequency variable.

[0016] Furthermore, the single-phase inverter includes four switching transistors, namely the first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor All four switching transistors are insulated-gate bipolar transistors, wherein: The gates of the four switching transistors are connected to the gate drive control signal. Power diodes are connected in parallel across the two ends of each of the four switching transistors. The collector of each switching transistor is connected to the negative terminal of the diode, and the emitter of each switching transistor is connected to the positive terminal of the diode. First switching transistor and the third switching transistor Series connection, and the first switching transistor The emitter is connected to the third switching transistor. The collector; the second switching transistor and the fourth switching transistor Series connection, and the second switch The emitter is connected to the fourth switching transistor. The collector of the first switching transistor; The collector is connected to the second switching transistor. The collector of the third switching transistor The emitter is connected to the fourth switching transistor. The emitter; DC power supply capacitor Both ends are connected to the first switching transistor. collector and third switching transistor The emitter, the second switching transistor The collector is connected to the DC power supply capacitor. The positive terminal, the fourth switching transistor The emitter is connected to the DC power supply capacitor. The negative electrode; The positive inductor The two ports are respectively ports and Port, filter inductor One end is connected to the first switching transistor The emitter of one end is connected to the positive inductor as a port of the negative inductor. The ports are connected, the Port and fourth switch The collector is connected; In step 3, the negative inductor is adjusted using an MCU controller. The inductance value makes the current ripple Compared with the preset current ripple reference value Methods for ensuring that the second difference between the two values ​​falls within a preset second deviation range include: Step 3.1: Adjust the virtual resistance according to the PI controller. and negative inductance Port voltage Current Analysis yields negative inductance The voltage drop of the actual equivalent inductance ; Step 3.2: Based on the negative inductance Voltage drop of the actual equivalent inductance and the required negative inductance Sensitivity Analysis yields negative inductance The reference current for the output current; Step 3.3: Based on the reference current, use a finite set model to predict and select the negative inductor. The switching state with the smallest output current tracking error is selected, and control signals for the four switching transistors are output to adjust the negative inductor. The value of feeling.

[0017] Furthermore, negative inductance The voltage drop of the actual equivalent inductance is based on The results were obtained through analysis.

[0018] Furthermore, negative inductance The reference current for the output current is based on Analysis yielded, among which The reference current is... Voltage drop of actual equivalent inductance The expression function in the frequency domain, It is a complex frequency variable.

[0019] Compared with the prior art, the beneficial effects of this invention are: 1. The high-power active variable inductor of the present invention includes a positive inductor. and negative inductance Among them, positive inductance Traditional physical inductors, negative inductors It is obtained from a single-phase inverter equivalent, through a positive inductor. and negative inductance Parallel connection increases the overall equivalent sensing value and provides a wider range of adjustment, thereby achieving better filtering results.

[0020] 2. The high-power active variable inductor of the present invention has a wide range of adjustable equivalent inductance value, high power density and is easy to implement. It can cope with three-phase imbalance, improve the power quality of the adjustable speed driver, and extend the life of the DC side filter capacitor. Thus, it effectively avoids the problems of bulky DC side passive filters of existing adjustable speed drivers, difficulty in reducing the size of active capacitors and narrow adjustment range of existing active inductors.

[0021] 3. The implementation of the present invention is more convenient: First, the present invention is a parallel structure, which makes it easy to improve the inductors that are already in use. Based on the inductors that are already in use, an H-bridge equivalent structure with a negative inductor is connected in parallel to increase the inductance value, thereby achieving a larger inductive reactance and a better filtering effect; Second, it is plug-and-play. The present invention is a dual-port inductor. Like traditional inductors, the DC side of the single-phase inverter uses a power supply capacitor instead of a DC source. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the application of an active variable inductor in a speed-adjustable driver. Figure 2 This is a schematic diagram of an active negative inductor; Figure 3 This is a block diagram of the structure and control method of an active variable inductor; Figure 4 This is a circuit diagram for testing the characteristics of a negative inductor port. Figure 5 This is a waveform diagram of the voltage and current at the negative inductor port; Figure 6 It is the amplitude-frequency characteristic curve of a negative inductor; Figure 7 This is a circuit diagram for testing the port characteristics of an active variable inductor. Figure 8 This is a waveform diagram of the port voltage and current of an active variable inductor; Figure 9 This is the amplitude-frequency characteristic curve of an active variable inductor; Figure 10 yes The DC-side capacitor voltage and inductor current diagram at that time; Figure 11 yes The DC-side capacitor voltage and inductor current diagram at that time; Figure 12 It is an inductor current diagram during load fluctuation; Figure 13 This is a waveform diagram of passive inductor filtering under unbalanced operating conditions; Figure 14 This is a waveform diagram of an active variable inductor filter under unbalanced operating conditions; Figure 15 This is a current spectrum analysis diagram of passive inductors and active variable inductors under unbalanced operating conditions; Detailed Implementation The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0023] Example 1 See Figure 1 , Figure 2 and Figure 3 A high-power active variable inductor for a speed-adjustable driver, comprising a positive inductance. negative inductance DC power supply capacitor The DC power supply capacitor Parallel connection in negative inductor The DC side; the negative inductor Including single-phase inverters and filter inductors The single-phase inverter and the filter inductor Series connection to form an equivalent negative inductance Used to adjust the negative inductance The inductance value makes the parallel positive inductors and negative inductance The overall feel value is adjustable.

[0024] The control method for the high-power active variable inductor in this embodiment, based on the aforementioned high-power active variable inductor, includes: Step 1: Real-time acquisition of negative inductance DC side voltage negative inductance Port voltage and negative inductance Current Analysis to obtain DC side voltage The first difference between the voltage and the preset voltage reference value; Step 2: Based on the first difference, adjust the negative inductor using a PI controller. A virtual resistor is used to compensate for negative inductance losses, making the DC-side voltage... The deviation from the voltage reference value is within a preset first deviation range; Step 3: Real-time acquisition of current in the parallel main circuit of the active variable inductor Extracting current Current ripple According to current ripple Compared with the preset current ripple reference value The second difference between them is adjusted using an MCU controller to control the negative inductance. The inductance value makes the current ripple Compared with the preset current ripple reference value The second difference between them is within the preset second deviation range.

[0025] In this embodiment, the high-power active variable inductor includes a positive inductor. and negative inductance Among them, positive inductance Traditional physical inductors, negative inductors It is obtained from a single-phase inverter equivalent, through a positive inductor. and negative inductance Parallel connection increases the overall equivalent inductance value and provides a wider adjustment range, resulting in better filtering performance. It allows for wide-range adjustment of the equivalent inductance value, high power density, and easy implementation. It can handle three-phase imbalance, improve the power quality of the adjustable speed driver, and extend the life of the DC-side filter capacitor. This effectively avoids the problems of bulky DC-side passive filters in existing adjustable speed drivers, difficulty in reducing the inductor size of active capacitors, and narrow adjustment range of existing active inductors.

[0026] Example 2 The application diagram of the high-power active variable inductor in the adjustable speed driver in this embodiment is shown below. Figure 1 As shown: The Adjustable Speed ​​Drive (ASD) includes an economical three-phase diode bridge rectifier, a DC-DC link filter, and a three-phase inverter; in the passive inductor, i.e., the positive inductor... negative inductor connected in parallel at both ends This allows for a larger inductance value, resulting in better filtering performance, thereby reducing the inductor's size and increasing power density. Simultaneously, by adjusting the inductance value of the negative inductor, the overall inductance value of the parallel circuit changes, achieving flexible and adjustable active variable inductors.

[0027] Specifically, high-power active variable inductors, including positive inductors negative inductance DC power supply capacitor MCU controller, PI controller and AD analog-to-digital converter, and the DC power supply capacitor. Parallel connection in negative inductor The DC side; the negative inductor Including single-phase inverters and filter inductors The single-phase inverter and the filter inductor Series connection to form an equivalent negative inductance .

[0028] The single-phase inverter (in this embodiment, an H-bridge is used) includes four switching transistors, namely the first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor All four switching transistors are insulated-gate bipolar transistors, wherein: The gates of the four switching transistors are connected to the gate drive control signal. Power diodes are connected in parallel across the two ends of each of the four switching transistors. The collector of each switching transistor is connected to the negative terminal of the diode, and the emitter of each switching transistor is connected to the positive terminal of the diode. First switching transistor and the third switching transistor Series connection, and the first switching transistor The emitter is connected to the third switching transistor. The collector; the second switching transistor and the fourth switching transistor Series connection, and the second switch The emitter is connected to the fourth switching transistor. The collector of the first switching transistor; The collector is connected to the second switching transistor. The collector of the third switching transistor The emitter is connected to the fourth switching transistor. The emitter; DC power supply capacitor Both ends are connected to the first switching transistor. collector and third switching transistor The emitter, the second switching transistor The collector is connected to the DC power supply capacitor. The positive terminal, the fourth switching transistor The emitter is connected to the DC power supply capacitor. The negative electrode; The positive inductor The two ports are respectively ports and Port, filter inductor One end is connected to the first switching transistor The emitter of one end is connected to the positive inductor as a port of the negative inductor. The ports are connected, the Port and fourth switch The collectors are connected.

[0029] A single-phase inverter consists of four switching transistors. During normal operation, the control signal controls the first switching transistor to be in its first state. and the fourth switching transistor Simultaneously, the second switching transistor is turned on. and the third switching transistor Off; the second state is the switching transistor. and switching transistor Turn off, switching transistor and switching transistor Simultaneous conduction, with the two states alternating cyclically, makes the port... , The excitation voltage and port current at both ends conform to the characteristics of a negative inductor.

[0030] In this embodiment, the AD converter includes a first AD converter, a second AD converter, and a third AD converter; the first AD converter is connected to the negative inductor. Connection used to acquire negative inductance The current is measured and converted into a first digital signal; a second analog-to-digital converter is used to acquire the positive inductance. The voltage signal between the two ports is converted into a second digital signal; the third AD analog-to-digital converter is used to convert the DC power supply capacitor The analog voltage signals at both ends are converted into a third digital signal; The PI controller is used to receive the third digital signal and perform negative inductance based on the third digital signal. The adjustment of the virtual resistance makes the DC side voltage... The deviation from the voltage reference value is within a preset first deviation range; The MCU controller is used to receive the first digital signal and the second digital signal, and generate a negative inductance based on the current ripple in the active variable inductor. The sensing value; and the virtual resistance adjusted by the PI controller. Generate and adjust negative inductance The control signal for the sensing value.

[0031] The inductance value of the positive inductor in the active inductor is selected based on the maximum DC-side current ripple allowed by ASD. This ensures that when a negative inductor fault is cleared, the entire system can operate at the minimum power quality standard without failing.

[0032] This embodiment of the control method for a high-power active variable inductor mainly includes three parts: a voltage loop, a control parameter generation loop, and a current loop. The voltage loop charges the DC capacitor of the single-phase inverter, keeping the voltage across the capacitor constant, thus acting as a DC source. The control parameter generation loop generates parameters based on the output current of the active inductor. The peak-to-peak value of the current ripple, combined with the peak-to-peak value of the target current ripple, affects the inductance of the negative inductor. Adjustments are made to change the overall inductance value of the active inductor, thereby adjusting its suppression effect on current ripple. The specific control method is as follows: Step 1: Real-time acquisition of negative inductance DC side voltage negative inductance Port voltage and negative inductance Current Analysis to obtain DC side voltage The first difference between the voltage and the preset voltage reference value; Step 2: Based on the first difference, adjust the negative inductor using a PI controller. A virtual resistor is used to compensate for negative inductance losses, making the DC-side voltage... The deviation from the voltage reference value is within a preset first deviation range; In this embodiment, the PI controller adjusts the negative inductor. The virtual resistance target value is ,in For the virtual resistance target value, This is the reference value for the DC power supply capacitor voltage on the DC side. The proportional parameter of the PI controller, These are the integral parameters of the PI controller. It is a complex frequency variable.

[0033] Step 3: Real-time acquisition of current in the parallel main circuit of the active variable inductor Extracting current Current ripple According to current ripple Compared with the preset current ripple reference value The second difference between them is adjusted using an MCU controller to control the negative inductance. The inductance value makes the current ripple Compared with the preset current ripple reference value The second difference between them is within the preset second deviation range; In this embodiment, the inductance value of the positive inductor is assumed to be... Based on the properties of a negative inductor, the overall equivalent inductance value after connecting positive and negative inductors in parallel can be obtained. When the positive inductance is fixed, as the inductance of the negative inductance gradually decreases and approaches the inductance of the positive inductance, the overall equivalent inductance... The rate of increase is getting larger and larger. When hour, Approaching Therefore, it is evident that the parallel connection of a negative inductor and a positive inductor can significantly increase the equivalent inductance, thereby greatly improving power density and power quality. For active inductors, there is only one control parameter: the equivalent inductance of the negative inductor. Under normal operating conditions, the control equivalent sensing value It can maintain the current ripple flowing through the active inductor at a reasonable level. Set the current ripple reference value. The current flowing through the active inductor is detected by a peak detection circuit. Peak extraction is performed to obtain the actual current ripple. Therefore, the MCU controller determines how to adjust the control parameters. .

[0034] The control precision (the difference between the current ripple after system stabilization and the target current ripple) is set based on the deviation between the current ripple reference value and the actual current ripple. When the deviation is less than the control precision, the system reaches stability, and the control parameters remain unchanged to avoid frequent adjustments caused by small fluctuations; when the deviation is greater than the control precision, the control parameters are adjusted.

[0035] Regarding the adjustment direction of the control parameters, the adjustment trend of the output value is determined according to the direction of the deviation: if the target current ripple is higher than the actual current ripple, the control parameters are adjusted in the direction of increasing; if the target current ripple is lower than the actual current ripple, the control parameters are adjusted in the direction of decreasing.

[0036] The control parameters are always limited to the preset upper and lower limits to ensure that they are within a reasonable operating range and to avoid exceeding the system's allowed boundaries.

[0037] The adjustment rate of the control parameter is related to the current inductance value of the negative inductor and shows a continuous changing trend: when the current control parameter is large, the adjustment rate is fast; when the current output value is small, the adjustment rate is slow. Based on the adjustment rate at the midpoint of the preset adjustable range of the negative inductor value, a smooth rate characteristic is formed throughout the entire adjustment range.

[0038] During the adjustment process, based on the initial value set by the negative inductance, and considering the adjustment direction and rate, the control parameters are updated in real time using the disturbance observation method. The specific adjustment procedure is as follows: Step 3.1: Adjust the virtual resistance according to the PI controller. and negative inductance Port voltage Current Analysis yields negative inductance Voltage drop of the actual equivalent inductance ; In this embodiment, the negative inductor The voltage drop of the actual equivalent inductance is based on The results were obtained through analysis.

[0039] Step 3.2: Based on the negative inductance Voltage drop of the actual equivalent inductance and the required negative inductance Sensitivity Analysis yields negative inductance The reference current for the output current; In this embodiment, the negative inductor The reference current for the output current is based on Analysis yielded, among which The reference current is... Voltage drop of actual equivalent inductance The expression function in the frequency domain, It is a complex frequency variable.

[0040] Step 3.3: Based on the reference current, employ Finite Set Model Predictive Control (FCS-MPC) and select a negative inductor. The switching state with the smallest output current tracking error is selected, and control signals for the four switching transistors are output to adjust the negative inductor. The sensitivity value; In this embodiment, the port output current is first measured in each sampling period. Sampling is performed, and the sampling results are then input into the MCU controller, combined with the output results of the voltage loop. A current reference value can be obtained. .

[0041] When the sampling frequency is low, the current reference value should be used for prediction. The reference value at that location. Lagrange extrapolation can be used for prediction. The current reference value at that location, its general expression is:

[0042] in

[0043] It is the order of the Lagrange extrapolation method. l For the summation index, 0 ≤ l ≤ n ,k This is a discrete-time index, representing the current sampling time. For sinusoidal reference values, It is usually set to 2. This allows us to obtain the predicted reference current value for the next moment.

[0044] Then, based on all the switching states of the switching equipment, a finite control set of the inverter is determined, and the correspondence between all valid switching states and output voltage is established, as shown in Table 1.

[0045] In Table 1, it is assumed that... - It is an ideal switching device with only two states (on and off). The switching state is represented by the state symbol: This indicates that the device is conducting. This indicates the device is off. Because the DC link cannot be short-circuited, the upper and lower switches on the same bridge arm cannot be turned on simultaneously. After eliminating the invalid states that would cause breakdown, the number of valid switch states is 4. The inverter output voltage corresponding to each state is expressed as follows: .

[0046] Table 1 Effective Switching Status of H-Bridge

[0047] The prediction model for the output current of a single-phase inverter is established as follows:

[0048] in It is the sampling period. The output voltage of a single-phase inverter At sampling time The value, Port voltage of a single-phase inverter At sampling time The value, The inductance value of the filter inductor is determined by... and By sampling and combining these samples with inverter system parameters, multiple predicted values ​​of the output current can be obtained. .

[0049] Finally, define the cost function. And select the optimal switching state.

[0050] Based on the cost function, determine the optimal switching state for the next instant.

[0051] To verify the feasibility of the high-power active variable inductor in the adjustable speed driver of this embodiment, according to Figure 1 and Figure 3 Build a simulation module in PSIM, set the predetermined control parameters according to Table 2, start the simulation, and obtain the following simulation results: Table 2 Port Feature Verification Parameter Table

[0052] Experiment 1: Negative Inductance Port Characteristic Test Experimental circuit for negative inductor port characteristics, such as Figure 4 As shown in Table 2, the experimental parameters were also presented. To verify that the port characteristics of the negative inductor conformed to those of a negative inductor, tests were conducted at frequencies of 50Hz and 300Hz. The voltage and current waveforms at the negative inductor port are as follows: Figure 5 As shown, it satisfies the characteristics of the negative inductance.

[0053] In addition, to verify the filtering performance of the negative inductor, the frequency was changed. To test its characteristics across the entire frequency band. For example... Figure 6 As shown, and They represent and The amplitude-frequency characteristic curve, and and These are ideal 5mH and 10mH negative inductors. Results show that the characteristics of the negative inductor match those of the ideal inductor very well in the 0-1kHz range. Experiments demonstrate that, within a specific frequency band, the filtering characteristics of the negative inductor match those of the ideal inductor very well.

[0054] Table 3. Parameters verified experimentally in adjustable speed actuators.

[0055] Experiment 2: Active Variable Inductor Port Testing Experimental circuit for testing port characteristics of active variable filter ports, as shown below. Figure 7 As shown. The experimental parameters are listed in Table 2. This experiment verifies whether the inductance value of the negative inductor can be changed. To adjust the inductance value of the active variable inductor. When At that time, the overall perception value is equivalent to the value. Similarly, hour, ,and hour, A 50V, 50Hz voltage excitation is applied to the port of the active variable inductor, and the voltage is changed... Observe the voltage-current waveforms at ports a and b under the following conditions, such as Figure 8 As shown. The measured effective value of the current shows that when hour, ;when hour, ;when hour, This experiment shows that it is possible to change Flexible adjustment .

[0056] To verify the filtering performance of the active variable filter, its performance across the entire frequency band was tested by changing the frequency of the voltage excitation. and The amplitude-frequency response curves of ideal inductors (inductance values ​​of 20mH and 57.3mH) are shown respectively. and That is and The curve at that time. For example... Figure 9 As shown, within the 0-1kHz frequency band, the curve closely matches the curve of an ideal inductor. At higher frequencies, due to the limitation of the sampling frequency, the output current of the negative inductor has a phase error, thus preventing the positive and negative inductor currents from achieving completely opposite phases. This results in the equivalent inductance value being less than the theoretical value. In a three-phase uncontrolled rectifier bridge, the main DC-side current harmonics are 100Hz and 300Hz; at these frequencies, active variable filters can effectively achieve filtering.

[0057] Experiment 3: Current Ripple Suppression Effect Test In the adjustable speed driver, an active variable filter is used to replace the passive inductor. The experimental parameters are shown in Case I of Table 3. First, the target current ripple is set to 1A, and the current in the active variable inductor is... like Figure 10 As shown. The DC-side power supply capacitor voltage is stable at around 100V with a fluctuation range of 1.273V, the current ripple is 1.05A, and the control error is within 5%. The target current ripple is set at 0.5A, and the current in the active variable inductor... like Figure 11 As shown, the DC-side power supply capacitor voltage is stable at around 100V with a fluctuation range of 0.859V, the current ripple is 0.526A, and the control error is 5.2%.

[0058] Experiment 4: Dynamic Testing 4.1) Load fluctuation During load switching, the current flowing through the inductor undergoes a sudden change. To verify the stability of the active filter during this process, switching is performed between Case I and Case II, with the target current ripple set to 1A. The current in the active variable inductor... like Figure 12 As shown, during load fluctuations, the current ripple is 1.09A, 1.07A and 1.04A respectively, which can be well controlled near the target current ripple.

[0059] 4.2) Three-phase unbalanced operating condition The target current ripple is 1A. A 33.7mH passive inductor and an active inductor are used for comparative experiments. Parameters are shown in Case III of Table 3. When a three-phase voltage imbalance occurs, the passive inductor has no filtering effect, such as... Figure 13 As shown, the current ripple increases from 0.96A to 2.16A. When a voltage imbalance occurs, if the current ripple is detected to be higher than the target value, the inductance of the active inductor adaptively adjusts to suppress the current ripple to the target value. Figure 14 As shown, the current ripple before and after the three-phase unbalanced condition is 1.03A and 1.15A, respectively. Figure 15 As shown, the "content" represents the ratio of the amplitude of each harmonic to the amplitude of the fundamental wave. When three-phase imbalance occurs, the passive inductor cannot effectively suppress the 100Hz harmonic introduced by the unbalanced voltage. At this time, the active inductor with adjustable inductance value has obvious advantages.

[0060] Simulation results demonstrate that the port characteristics of the negative inductor in this invention, when operating normally, satisfy the properties of a negative inductor and can respond across the entire frequency band, making it applicable to filter circuits with complex harmonic content. Through the control method described in this invention, the active variable inductor can exhibit the performance of a large inductance value with a small inductance value, further illustrating that this invention can reduce filter size, increase power density, and reduce cost. Furthermore, its wide inductance adjustment range enables it to better handle harsh operating conditions such as three-phase voltage imbalance, improving power quality and extending the lifespan of passive components.

[0061] The high-power active variable inductor of this embodiment has a wide range of equivalent inductance adjustment space, with a higher upper limit for the equivalent inductance value. It also has the advantages of high power density, small size, and low weight. Under the premise of achieving the same filtering effect, the size of the physical inductor can be reduced, thereby increasing power density and saving costs. The machine control method of the high-power active variable inductor of this embodiment is more convenient to implement. First, through the parallel structure of this invention, it is convenient to improve the inductors already in use. Based on the existing inductors, an H-bridge equivalent structure with a negative inductor is connected in parallel to increase the inductance value, thereby achieving a larger inductive reactance and a better filtering effect. Second, it is plug-and-play. This solution is dual-port, and like traditional inductors, the DC side of the single-phase inverter uses a power supply capacitor instead of a DC source.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-power active variable inductor for an adjustable speed driver, characterized in that, Including positive inductance negative inductance DC power supply capacitor The DC power supply capacitor Parallel connection in negative inductor The DC side; the negative inductor Including single-phase inverters and filter inductors The single-phase inverter and the filter inductor Series connection to form an equivalent negative inductance Used to adjust the negative inductance The inductance value makes the parallel positive inductors and negative inductance The overall feel value is adjustable.

2. The high-power active variable inductor according to claim 1, characterized in that, The single-phase inverter includes four switching transistors, namely the first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor All four switching transistors are insulated-gate bipolar transistors, wherein: The gates of the four switching transistors are connected to the gate drive control signal. Power diodes are connected in parallel across the two ends of each of the four switching transistors. The collector of each switching transistor is connected to the negative terminal of the diode, and the emitter of each switching transistor is connected to the positive terminal of the diode. First switching transistor and the third switching transistor Series connection, and the first switching transistor The emitter is connected to the third switching transistor. The collector; the second switching transistor and the fourth switching transistor Series connection, and the second switch The emitter is connected to the fourth switching transistor. The collector of the first switching transistor; The collector is connected to the second switching transistor. The collector of the third switching transistor The emitter is connected to the fourth switching transistor. The emitter; DC power supply capacitor Both ends are connected to the first switching transistor. collector and third switching transistor The emitter, the second switching transistor The collector is connected to the DC power supply capacitor. The positive terminal, the fourth switching transistor The emitter is connected to the DC power supply capacitor. The negative electrode; The positive inductor The two ports are respectively ports and Port, filter inductor One end is connected to the first switching transistor The emitter of one end is connected to the positive inductor as a port of the negative inductor. The ports are connected, the Port and fourth switch The collectors are connected.

3. The high-power active variable inductor according to claim 1, characterized in that, It also includes an MCU controller, a PI controller, and an AD converter; the AD converter includes a first AD converter, a second AD converter, and a third AD converter; the first AD converter is connected to the negative inductor. Connection used to acquire negative inductance The current is measured and converted into a first digital signal; a second analog-to-digital converter is used to acquire the positive inductance. The voltage signal between the two ports is converted into a second digital signal; the third AD analog-to-digital converter is used to convert the DC power supply capacitor The analog voltage signals at both ends are converted into a third digital signal; The PI controller is used to receive the third digital signal and perform negative inductance based on the third digital signal. The adjustment of the virtual resistance makes the DC side voltage... The deviation from the voltage reference value is within a preset first deviation range; The MCU controller is used to receive the first digital signal and the second digital signal, and generate a negative inductance based on the current ripple in the active variable inductor. The sensing value; and the virtual resistance adjusted by the PI controller. Generate and adjust negative inductance The control signal for the sensing value.

4. A control method for a high-power active variable inductor in a speed-adjustable driver, the control method being based on the high-power active variable inductor as described in claim 1, characterized in that, include: Step 1: Real-time acquisition of negative inductance DC side voltage negative inductance Port voltage and negative inductance Current Analysis to obtain DC side voltage The first difference between the voltage and the preset voltage reference value; Step 2: Based on the first difference, adjust the negative inductor using a PI controller. A virtual resistor is used to compensate for negative inductance losses, making the DC-side voltage... The deviation from the voltage reference value is within a preset first deviation range; Step 3: Real-time acquisition of current in the parallel main circuit of the active variable inductor Extracting current Current ripple According to current ripple Compared with the preset current ripple reference value The second difference between them is adjusted using an MCU controller to control the negative inductance. The inductance value makes the current ripple Compared with the preset current ripple reference value The second difference between them is within the preset second deviation range.

5. The control method according to claim 4, characterized in that, In step 2, the PI controller adjusts the negative inductor. The virtual resistance target value is ,in For the virtual resistance target value, This is the reference value for the DC power supply capacitor voltage on the DC side. The proportional parameter of the PI controller, These are the integral parameters of the PI controller. It is a complex frequency variable.

6. The control method according to claim 4, characterized in that, The single-phase inverter includes four switching transistors, namely the first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor All four switching transistors are insulated-gate bipolar transistors, wherein: The gates of the four switching transistors are connected to the gate drive control signal. Power diodes are connected in parallel across the two ends of each of the four switching transistors. The collector of each switching transistor is connected to the negative terminal of the diode, and the emitter of each switching transistor is connected to the positive terminal of the diode. First switching transistor and the third switching transistor Series connection, and the first switching transistor The emitter is connected to the third switching transistor. The collector; the second switching transistor and the fourth switching transistor Series connection, and the second switch The emitter is connected to the fourth switching transistor. The collector of the first switching transistor; The collector is connected to the second switching transistor. The collector of the third switching transistor The emitter is connected to the fourth switching transistor. The emitter; DC power supply capacitor Both ends are connected to the first switching transistor. collector and third switching transistor The emitter, the second switching transistor The collector is connected to the DC power supply capacitor. The positive terminal, the fourth switching transistor The emitter is connected to the DC power supply capacitor. The negative electrode; The positive inductor The two ports are respectively ports and Port, filter inductor One end is connected to the first switching transistor The emitter of one end is connected to the positive inductor as a port of the negative inductor. The ports are connected, the Port and fourth switch The collector is connected; In step 3, the negative inductor is adjusted using an MCU controller. The inductance value makes the current ripple Compared with the preset current ripple reference value Methods for ensuring that the second difference between the two values ​​falls within a preset second deviation range include: Step 3.1: Adjust the virtual resistance according to the PI controller. and negative inductance Port voltage Current Analysis yields negative inductance Voltage drop of the actual equivalent inductance ; Step 3.2: Based on the negative inductance Voltage drop of the actual equivalent inductance and the required negative inductance Sensitivity Analysis yields negative inductance The reference current for the output current; Step 3.3: Based on the reference current, use a finite set model to predict and select the negative inductor. The switching state with the smallest output current tracking error is selected, and control signals for the four switching transistors are output to adjust the negative inductor. The value of feeling.

7. The control method according to claim 6, characterized in that, negative inductance The voltage drop of the actual equivalent inductance is based on The results were obtained through analysis.

8. The control method according to claim 6, characterized in that, negative inductance The reference current for the output current is based on Analysis yielded, among which The reference current is... Voltage drop of actual equivalent inductance The expression function in the frequency domain, It is a complex frequency variable.

Images