Multi-path parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loops

Abstract

The invention discloses a multipath parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loops, which comprises an LCL filter and a power supply system, and is characterized in that the LCL filter is connected with the power supply system, and the power supply system comprises a plurality of devices arranged in parallel; wherein each device comprises a boost chopping module, an inversion module, a diode uncontrolled rectification module and a Buck module, and the system adopts double-loop control of voltage outer loop-current inner loop combination for the boost chopping module of each device. An ADRC is designed as a voltage outer ring and a PI is designed as a current inner ring, and an automatic current sharing strategy is added to control the output voltage of the boost module and the current sharing condition between multiple paths of equipment; and the inverter module and the Buck module adopt a fixed duty ratio to control the output power of the power supply to be matched with the power required by the load. According to the invention, the output power quality and transient performance of the multi-path parallel current-sharing high-frequency auxiliary system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of active disturbance rejection control, and particularly to a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on an ADRC-PI double closed-loop. Background Art

[0002] As a new control strategy, the active disturbance rejection control (ADRC) technology has the ability to estimate and compensate for internal uncertainties and external disturbances of the system in real time, and can effectively improve the robustness and anti-interference ability of the system. However, in some cases, the pure ADRC control may have an unsatisfactory steady-state accuracy. Therefore, combining ADRC with PI control to construct an ADRC-PI double closed-loop control structure and giving full play to the advantages of both is of great significance for a multi-channel parallel high-frequency auxiliary power supply system. This double closed-loop control method can improve the steady-state control accuracy while ensuring the fast response and strong anti-interference ability of the system, better meet the stable and efficient power supply requirements of the auxiliary power supply of urban rail vehicles under complex working conditions, and provide a strong guarantee for the safe and reliable operation of urban rail transit.

[0003] With the rapid development of modern urban rail transit technology, various electrical equipment in urban rail vehicles is increasing in number and becoming more complex in function, and the requirements for the auxiliary power supply system are also constantly rising. On the one hand, for numerous electrical equipment such as air conditioners, lighting, communication, door control, and various electronic monitoring equipment, the total power demand continues to grow, and the traditional single-channel or simple multi-channel auxiliary power supply is difficult to meet the power output capacity. On the other hand, urban rail transit has extremely high standards for operation safety and reliability. Once the auxiliary power supply fails and causes a power supply interruption, it will seriously affect the normal operation of the train and even endanger the safety of passengers.

[0004] In the existing power control technology field, traditional control methods such as PI control have limitations in dealing with complex non-linear systems and variable load conditions. For a multi-channel parallel high-frequency auxiliary power supply system, due to the mutual coupling and interference between parallel branches and the large dynamic range of the load, it is difficult for PI control to achieve high-precision fast response and stable control. For example, when the train starts, accelerates, and different equipment frequently starts and stops and switches, the power supply system under PI control may have problems such as large output voltage fluctuations and uneven current distribution, affecting the power supply quality and system reliability. Summary of the Invention

[0005] According to the problems existing in the prior art, the present invention discloses a multi-parallel current-sharing high-frequency auxiliary power supply system based on an ADRC-PI double closed-loop, including: an LCL filter and a power supply system, wherein the LCL filter is connected to the power supply system, and the power supply system includes a plurality of devices arranged in parallel, and each device includes a boost chopper module, an inverter module, a diode uncontrolled rectifier module, and a Buck buck module; the boost chopper module adopts a double closed-loop control combining the ADRC algorithm and the PI algorithm, and uses LADRC as the voltage outer loop and PI as the current inner loop controller to control the output voltage value of the boost chopper module; the inverter module and the Buck buck module adopt a fixed duty cycle control.

[0006] Furthermore, the system adopts a double-loop control combining a voltage outer loop and a current inner loop for the boost chopper module of the device, designs a linear active disturbance rejection control (LADRC) as the voltage outer loop and PI as the current inner loop to stabilize the output voltage of the boost module, and adds an automatic current-sharing strategy to the current inner loop to control the current difference between two devices to achieve a current-sharing effect; the inverter and Buck buck modules adopt a fixed duty cycle to control the power output of the power supply to match the power required by the load;

[0007] The specific design of ADRC-PI is as follows: First, the mathematical model of the boost chopper module is fitted into a second-order LADRC model, and a second-order linear extended state observer is designed to achieve more accurate estimation and compensation of the total disturbance, enhance the anti-disturbance ability, and improve the response speed. At the same time, the observer parameters are optimized and selected; second, an automatic current-sharing strategy is designed: the currents of two devices are selected for subtraction, and then the current inner loop parameters are designed so that the current difference between the two devices is 0; finally, a suitable PWM signal is output to control the conduction and turn-off of the IGBT.

[0008] The characteristics of the present invention also lie in that

[0009] The specific implementation of the ADRC-PI design is carried out according to the following steps:

[0010] Step 1: Establish the mathematical model of the boost chopper module;

[0011] Step 2: LESO design;

[0012] Step 3: Simplify the adjustable parameters of the observer based on the ADRC principle;

[0013] Step 4: Deduce the equivalent PID control by the frequency domain method;

[0014] Step 5: Automatic current-sharing strategy design;

[0015] Step 6: Fixed duty cycle control.

[0016] Specifically, Step 1 is

[0017] Take the output voltage U of the boost chopper circuit dc as the negative feedback quantity and the output quantity, and set U dc reference value U dc * as the input, and the branch current i * (n represents the device number, which is device 1 when it is 1 and device 2 when it is 2) as the input. Figure 2 In it, b0 is the high-frequency gain related to the controlled object; Z1 and Z2 are the state estimation values of the linear extended state observer (LESO), where Z2 is defined as the "total disturbance", e is the estimation error, and u0 can be regarded as the control quantity before compensation. The mathematical model for LADRC is:

[0018]

[0019] In the formula, h is the total disturbance.

[0020] After substituting the parameters of the boost chopper circuit of the high-frequency power supply, the mathematical model is obtained:

[0021]

[0022] In the formula: C = [1 0], D = [0],

[0023] z1 and z2 are respectively the output voltage of the boost chopper circuit and the state of the total disturbance estimated in real time, and β1 and β2 are the error feedback gains.

[0024] Step 2 is specifically:

[0025] Linear extended state observer (LESO), its specific design:

[0026] It should be noted that from formula (1) to formula (2), h is ignored because h is unknown and can be estimated through the error correction term. The mathematical model derived from the mathematical derivation of LESO:

[0027]

[0028] Step 3 is specifically:

[0029] Using the pole placement method, it is necessary to use the matrix L to place all the poles of the characteristic equation of LESO at -ω0, and find the relationship between the error feedback gains β1 and β2 and the observer bandwidth ω0:

[0030] λ(s) = |sI - (A - LC)| = (s + ω0) (4)

[0031] In the formula: I is the second-order identity matrix.

[0032] Substituting matrices A, L, and C, we can obtain:

[0033]

[0034] So far, the control parameters of LADRC are only ω0, b0, and k p Three parameters need to be designed, where k p is the controller bandwidth.

[0035] Specifically, step 4 is as follows:

[0036] Using the frequency-domain method to derive the transfer function of the first-order LADRC, replace the voltage outer loop in the double closed-loop PID of the boost chopper circuit with LADRC, and still use PID control for the current inner loop. Derive Figure 1 the transfer function from U dc * to U dc as follows. Now, the derivation process is given:

[0037] The feedback control law of the first-order LADRC includes a proportional controller and a disturbance compensation link. According to Figure 2 , design the disturbance compensation link:

[0038]

[0039] In the formula: The parameter r is used to eliminate the oscillation brought by the response.

[0040] Substitute equation (6) into equation (3) to get:

[0041]

[0042] Use the frequency-domain method to find the transfer function matrix of the state-space equation:

[0043] G = [sI - A] -1 Β (8)

[0044] We can obtain:

[0045]

[0046] Let U dc * = 0 in equation (9), then we can find i * For the transfer function of U dc ; Similarly, let U dc = 0, then we can find i * For the transfer function of U dc * :

[0047]

[0048] The denominator order of the expression of the PI parameters is increased by one order using a low-pass filter, so that the LADRC is equivalent to the PI parameters. The equivalent process is as follows:

[0049]

[0050] where α is an adjustable parameter, k i ′ and k p ′ are the PI parameters to be equivalent.

[0051] By combining Equation (12) and Equation (5), the expressions for the three parameters ω0, b0, and k p can be obtained:

[0052]

[0053] So far, the voltage outer-loop PI in the LADRC equivalent boost chopper circuit control has been completed.

[0054] Step 5 is specifically:

[0055] When using phase-shifted voltage-current double-loop PI control, due to the imbalance of the resistances of the two devices (inductor internal resistance, circuit internal resistance, switch tube internal resistance, etc.), the current imbalance between Device 1 and Device 2 will occur.

[0056] The difference between the two-way currents is taken to obtain Δi d :

[0057]

[0058] where Ts is the switching period of the switch tube, i1 is the current flowing through Device 1, I1 is the average current flowing through Device 1 per unit period; i2 is the current flowing through Device 1, and I2 is the average current flowing through Device 1 per unit period.

[0059] The DC high voltage of 1500V supplies power to the device after passing through the DC filter. The feedback output voltage V dc is compared with the set voltage V ref to obtain the error value e. After being processed by the ADRC controller, the total current set reference value i ref is obtained. Then, an averaging operation is performed on i ref to obtain the current reference value of each branch. On this basis, the current acquisition compensation amount Δi r is added to obtain the input ideal current. Subsequently, this current passes through the current loop (PI), and finally, the current automatic balancing double-loop control is achieved by adjusting the PWM.

[0060] Now, the calculation method of the current compensation amount Δi r is given:

[0061]

[0062] Wherein, m (m is generally selected as 5 - 15 according to experience) is the number of times of averaging within a unit period, a is the starting number of averaging, and n is the device label.

[0063] Δi r By comparing with the threshold value Δi of the current difference rth to determine whether the current imbalance phenomenon occurs, the determination criterion is:

[0064]

[0065] When current uneven flow occurs, Δi is required r to compensate the current values of each branch, and the compensation method is as follows:

[0066]

[0067] Wherein, i ref1 [n] and i ref2 [n] are the total branch currents of device 1 and device 2, and the equal current sharing of each branch current can be completed through the calculation of formulas (15) - (16).

[0068] Step 6 is specifically

[0069] The duty cycle refers to the ratio of the high - level duration in the pulse signal to the entire cycle time. The value of the fixed duty cycle is determined according to the system requirements, usually determined by the performance requirements of the inverter module and the Buck module. It is also necessary to determine the period of the PWM signal. For some systems with requirements for response speed, an appropriate period needs to be selected. Connect the output pin of the produced PWM signal to the control ends of the inverter module and the Buck module, and adjust the output voltage of the module according to the input PWM signal.

[0070] Due to the adoption of the above - mentioned technical solution, a multi - path parallel current - sharing high - frequency auxiliary power supply system based on ADRC - PI double - closed - loop provided by the present invention adopts a double - loop control of voltage outer - loop and current inner - loop for the boost chopper module of the power supply system, designs ADRC as the voltage outer - loop and PI as the current inner - loop, and adds an automatic current - sharing strategy to control the output voltage of the boost module and the current sharing situation among multiple devices; the inverter module and the Buck buck - down module adopt a fixed duty cycle to control the output power of the power supply to match the power required by the load. The present invention improves the output power quality and transient performance of the multi - path parallel current - sharing high - frequency auxiliary system. Description of the Drawings

[0071] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0072] Figure 1 is the schematic diagram of the main circuit;

[0073] Figure 2 is the control block diagram of LADRC;

[0074] Figure 3 is the control block diagram of the linear extended state observer;

[0075] Figure 4 is the control block diagram of the boost chopper circuit;

[0076] Figure 5 is the simulation waveform diagram of the output voltage of the boost chopper module;

[0077] Figure 6 is the simulation waveform diagram of the current sharing current of the multi-channel devices;

[0078] Figure 7 is the simulation waveform diagram of the output voltage of the Buck module under the condition of load mutation. Specific embodiments

[0079] To make the technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention:

[0080] As Figure 1 shown, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI dual closed-loop. This system adopts a dual-loop control of voltage outer loop - current inner loop for the boost chopper module of the power supply system, designs a linear active disturbance rejection control (LADRC) as the voltage outer loop, designs a PI as the current inner loop, and adds an automatic current-sharing strategy between two devices in the current inner loop to control the current difference between devices; adopts a fixed duty cycle control for the inverter module and the Buck module to simplify the overall control difficulty of the system.

[0081] Combined with the high-frequency auxiliary power supply model, a second-order LADRC controller is designed for the urban rail train with uncertain parameters and external disturbances. Its traditional structure is as Figure 2As shown in the figure. The traditional LADRC is mainly composed of a tracking differentiator (TD), a linear extended state observer (LESO) and a linear error feedback rate (LSEF). The role of TD is to soften the start-up link signal and eliminate the conflict between overshoot and rapidity. In order to avoid high-frequency oscillation of the bus voltage, TD is not used. LESO monitors the expansion state in real time, and LSEF is used to compensate for disturbances to form an integral series control rate. Figure 2 Middle: Boost chopper circuit output voltage U dc As negative feedback and output; set U dc Reference value U dc * As input, the branch current i * (n represents the device number, 1 for device 1, 2 for device 2) as the input control quantity; b0 is the high-frequency gain related to the controlled object; Z1, Z2 and Z3 are the state estimates of the linear extended state observer (LESO), where Z2 is defined as the "total disturbance"; e is the estimation error; u0 can be regarded as the control quantity before compensation; the ADRC controller structure after canceling TD is as follows Figure 3 As shown. The specific model of the high-frequency auxiliary power boost chopper module is:

[0082]

[0083] Where: C=[1 0],D=[0],

[0084] LESO is crucial in LADRC. It estimates the system state, treats internal and external disturbances as a total disturbance, and feeds it back to the controller as an extended state to achieve accurate estimation of system disturbances. LSEF performs linear state feedback based on the state estimate provided by LESO, generates control signals, and compensates for system state errors, thereby achieving fast and accurate control of the system. Figure 4 As shown. The LESO expression is:

[0085]

[0086] According to the bandwidth method of the linear observer, all poles of LESO are configured to ω0, and the following configuration is made for equation (1):

[0087]

[0088] The above configuration simplifies the two adjustable parameters of the observer to one.

[0089] The voltage outer-loop parameters are equivalent to the ADRC control parameters ω0, b0, and k through the frequency-domain method. p Expressions for the three parameters:

[0090]

[0091] The voltage outer-loop PI in the LADRC equivalent boost chopper circuit control has been completed. The control block diagram after equivalent control is as Figure 5 shown. The ADRC-PI double closed-loop control can control the output voltage of the boost chopper module at 960V, achieving a current sharing effect between two devices and enhancing the stability of the system.

[0092] Simulation verification:

[0093] To further compare and verify the effectiveness and better control ability of the control method of the present invention, a multi-parallel high-frequency auxiliary power supply system based on the ADRC-PI double closed-loop is built in Matlab Simulink. The circuit parameters are shown in Table 1, and the circuit control parameters under different strategies are shown in Table 2.

[0094] Table 1 Circuit topology parameters

[0095] parameter numerical value <![CDATA[High-voltage bus voltage V in / V]]> 1500 <![CDATA[Filter Inductor L1 / mH]]> 0.8 <![CDATA[Filter inductor L2 / mH]]> 3.3 <![CDATA[Filter capacitor C1 / μF]]> 4

[0096] Table 2 Control strategy parameters

[0097]

[0098] In Table 2, k p ′ and k i ′ are the proportional coefficient and integral coefficient of the voltage outer loop under the traditional double closed-loop PI control strategy respectively. k pd and k id are the proportional coefficient and integral coefficient of the current inner loop under the traditional double closed-loop PI and ADRC-PI double closed-loops respectively. Select α = 1×10 25 , and then substitute k p ′ and k i ′ into Equation (4) to calculate the ADRC controller parameters k p , the disturbance bandwidth ω0, and the high-frequency gain b0 related to the controlled object.

[0099] (I) Comparative analysis of the output voltage of the boost chopper module

[0100] To verify the superiority of the control method of the present invention, the control method of the present invention and the traditional double closed-loop PI control are used to control the boost chopper module of the high-frequency auxiliary power supply system, and their transient performances are compared and analyzed.

[0101] Figure 6When the boost chopper module of the high-frequency auxiliary power supply outputs 960V under the rated working condition, the output voltage waveforms under two control strategies are as follows. The comparison results are as Figure 6 shown. It can be seen that the control method of the present invention has a shorter adjustment time and a smaller overshoot, showing better control ability. The transient performance indexes of the output voltage waveforms of the boost chopper module under different control strategies are shown in Table 3.

[0102] Table 3 Transient performance indexes of the output voltage waveforms of the boost chopper module

[0103]

[0104] (2) Current sharing situation of multiple parallel devices

[0105] In order to further verify the control effect of the automatic current sharing strategy under the control method of the present invention, the automatic current sharing is applied in the ADRC-PI double closed-loop strategy. Figure 7 shows the control of the high-frequency auxiliary power supply system under the control method of the present invention and the traditional double closed-loop PI two strategies, and a comparative analysis is carried out.

[0106] Under the rated condition, the total current output of the high-frequency auxiliary power supply is 100A, and the current sharing between two devices is 50A. The comparison results of the transient process are as Figure 7(a) to Figure 7(b) shown. When the total output current of the system reaches 100A, the current waveforms of Device 1 and Device 2 are similar and stable near 50A. Only the current of Device 1 is shown here. It can be seen that the control method of the present invention has a faster response time, a shorter adjustment time and a smaller overshoot compared with the traditional double closed-loop PI control. Table 4 and Table 5 are the transient performance indexes of the total system current waveform and the transient performance indexes of the current sharing waveform of the system devices respectively.

[0107] Table 4 Transient performance indexes of the total system current waveform

[0108]

[0109]

[0110] Table 5 Transient performance indexes of the current sharing waveform of the system devices

[0111]

[0112] In summary, the high-frequency auxiliary power supply model suitable for multi-way parallel connection constructed in the present invention takes into account that active disturbance rejection control (ADRC) is a control method that does not rely on the accurate modeling of the system. Comparing with the deficiencies of the above control strategies, the ADRC controller has a simple structure and strong robustness. It can regard the internal disturbance and unmeasurable external disturbance in the model as the extended state of the system, and realizes the accurate observation and real-time compensation of the total disturbance through the extended state observer and the feedback mechanism. It is very suitable for the design of strongly nonlinear and uncertain systems such as urban rail trains. Therefore, the train dynamics model under multi-way parallel connection is combined with the active disturbance rejection control principle, aiming at fast response and current sharing among devices. Adding an automatic current sharing control strategy to the ADRC-PI double closed-loop effectively improves the safety of the train, providing a theoretical reference for the safe operation of multi-way parallel urban rail trains under complex working conditions.

[0113] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that include: An LCL filter and a power supply system, wherein the LCL filter is connected to the power supply system, wherein the power supply system comprises a plurality of devices arranged in parallel, wherein each device comprises a boost chopper module, an inverter module, a diode uncontrolled rectifier module and a Buck buck module; the boost chopper module adopts a double closed-loop control combining an ADRC algorithm with a PI algorithm, and adopts LADRC as a voltage outer loop and PI as a current inner loop controller to control the output voltage value of the boost chopper module; and a fixed duty cycle control is adopted for the inverter module and the Buck buck module.

2. According to claim 1, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that: The mathematical model of the boost chopper module is fitted into a second-order linear extended state observer model, and the second-order extended state observer is used to achieve accurate estimation and compensation of the total disturbance, thereby enhancing the anti-disturbance capability and improving the response speed. The parameters of the extended state observer are optimized to improve the accuracy of its dynamic response to the system, and an automatic current equalization strategy is designed. The current difference between the two devices is made zero by differentially processing the currents of the two devices and designing the current inner loop parameters. Finally, an appropriate PWM signal is output to control the on and off of the IGBT.

3. According to claim 1, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that: The ADRC algorithm obtains the feedback error of the entire multi-channel parallel current-sharing high-frequency auxiliary power system based on a linear expansion observer, nonlinearly combines the input voltage, expected voltage, and feedback total error data, and calculates the optimal PWM expansion signal of the current boost chopper module, thereby realizing ADRC-PI dual closed-loop control.

4. According to claim 1, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that: The expected current sharing value is obtained by subtracting the current of the two devices, and the expected control voltage that needs to be controlled at the output is calculated through the PI inner loop.

5. According to claim 1, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that: The inverter module of each device in the system includes an H-bridge control circuit composed of four power IGBT switching tubes, an uncontrolled rectifier module composed of high-frequency diodes, and a Buck step-down module.

6. According to claim 1, a multi-channel parallel current-sharing high-frequency auxiliary power supply system based on ADRC-PI double closed loop, characterized in that: The mathematical model of the boost chopper module is: Where: z1 and z2 are the real-time estimated output voltage and total disturbance states of the boost chopper circuit, respectively, and β1 and β2 are the error feedback gains.

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