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CN-121984341-A - Fault tolerance control method for input-parallel output series double-active-bridge switch Guan Kailu

CN121984341ACN 121984341 ACN121984341 ACN 121984341ACN-121984341-A

Abstract

The invention relates to the field of power electronics, and particularly discloses a fault tolerance control method of an input-parallel output series double-active-bridge switch Guan Kailu, which comprises fault detection, fault tolerance control, self-adaptive voltage equalizing control, starting, stabilizing and tracking three stages of voltage reference value dynamic generation based on running time and voltage state, switching control modes and parameters according to fault and unbalance conditions in the tracking stage, realizing voltage equalization among modules under all working conditions, and limiting the change rate and hard limiting of the voltage reference value by adopting strategies of reducing the secondary side duty ratio and increasing D 3 or blocking the same-bridge-arm switch tubes and increasing D 1 respectively aiming at primary side or secondary side faults. The invention can effectively eliminate the current bias caused by faults, reduce the current stress and ensure the voltage balance and stability of the multi-module DAB system when the switching tube is in open-circuit fault derating operation.

Inventors

  • XING XIANGYANG
  • Che Hanhui

Assignees

  • 山东大学

Dates

Publication Date
20260505
Application Date
20260206

Claims (10)

  1. 1. The fault tolerance control method for the input-parallel output series double-active-bridge switch Guan Kailu is applied to an input-parallel output series system comprising N double-active-bridge modules and is characterized by comprising the following steps of: the method comprises the steps of monitoring inductance current and output voltage of each double-active-bridge module in real time, and identifying position information of a switching tube with open-circuit faults according to direct-current bias characteristics and output voltage changes of the inductance current; Executing different fault-tolerant control strategies on primary side faults and secondary side faults according to the position information of the switching tube so as to eliminate inductance current direct current bias caused by faults; Dynamically generating an output voltage reference value of each module by adopting a multi-stage self-adaptive control algorithm based on the output voltage of each double active bridge module and the system running time; And limiting the change rate of the voltage reference value, hard limiting the voltage reference value, and outputting a voltage reference instruction finally used for controlling each module.
  2. 2. The fault-tolerant control method for an input-parallel output tandem dual active bridge switch Guan Kailu according to claim 1, wherein the fault-tolerant control strategy includes: If the open-circuit fault of the primary side switching tube of any double active bridge module is detected, the duty ratio of the secondary side full bridge of the fault module is reduced to generate a direct current bias component, and the secondary side internal shift phase angle D 3 is increased; If the open-circuit fault of the secondary side switching tube of any double-active-bridge module is detected, the other switching tube of the same bridge arm with the fault switching tube is blocked, and the primary side internal shift phase angle D 1 is increased.
  3. 3. The fault-tolerant control method for the input-parallel output series double-active-bridge switch Guan Kailu is characterized in that specific adjustment quantity of the duty ratio of the secondary full bridge of the fault module is reduced according to the open-circuit fault of the primary switching tube through closed-loop control calculation, so that the corrected inductive current is symmetrical in positive and negative half-cycle amplitude, and the secondary internal phase angle D 3 is increased to reduce the peak value and the change rate of the inductive current in a fault state.
  4. 4. The fault-tolerant control method of input-parallel output series double-active-bridge switch Guan Kailu according to claim 3, wherein for the open-circuit fault of the secondary side switching tube, blocking the other switching tube of the same bridge arm as the fault switching tube means that the driving signal of the fault bridge arm is deactivated to make it in an open-circuit state, and the primary side internal phase angle D 1 is increased to be used for matching with the power transmission characteristic in the single bridge arm working mode to optimize the current waveform.
  5. 5. The fault-tolerant control method of an input-parallel output-series dual-active bridge switch Guan Kailu according to claim 1, wherein the multi-stage adaptive control algorithm includes a start-up stage, a steady-state stage, and a tracking stage, and switches between stages according to the system run time and the voltage states of the respective modules, wherein: The starting stage is to adopt a nonlinear smoothing function to generate a voltage reference value V ref_state which is smoothly increased from zero to a target value in a preset time period t startup after the system is started; The stable phase is to quickly adjust V ref_state by adopting a first group of PI control parameters when the system running time exceeds t startup and the average voltage does not reach a preset target threshold value eta settling ; The tracking stage is to switch control parameters among a normal mode, a fault mode and an unbalanced mode according to the filtered minimum module voltage U min_filtered and the voltage unbalance degree delta U imbalance between modules after the system voltage enters a steady-state range, so as to finely adjust V ref_state .
  6. 6. The fault-tolerant control method for the input-parallel output series double-active-bridge switch Guan Kailu according to claim 5, wherein the nonlinear smooth transition function in the starting stage specifically adopts an S-shaped curve function, and the calculation formula thereof satisfies: V ref_state =f tnorm *V initial_ref Wherein V ref_state is a voltage reference value, V initial_ref is a system initial target voltage, t norm is a normalized time, and f t_norm is a polynomial function of degree three or more with respect to time.
  7. 7. The fault-tolerant control method for the input-parallel output series double-active-bridge switch Guan Kailu according to claim 6, wherein the fault mode determination condition in the tracking stage is U min_filtered <V ref_state - V th_fault , where U min_filtered is the filtered minimum module voltage and V th_fault is a preset fault determination threshold; in the fault mode, a second group of PI control parameters are adopted, and an error calculation formula is adjusted to be error=U min_filtered + V margin - V ref_state , wherein error is an input deviation signal of the PI controller, and V margin is a safety margin.
  8. 8. The fault-tolerant control method for an input-parallel output series double active bridge switch Guan Kailu according to claim 7, wherein the unbalanced mode determination condition in the tracking phase is ΔU imbalance > V th_imbalance , where ΔU imbalance is the difference between the maximum module voltage and the minimum module voltage, and V th_imbalance is a preset unbalanced threshold; In the unbalanced mode, a zero parameter set is adopted, namely the proportional coefficient and the integral coefficient of the PI controller are set to be zero, and updating of the reference voltage is suspended.
  9. 9. A fault-tolerant control system for an input-parallel-output series double-active-bridge switch Guan Kailu, which is used for implementing the fault-tolerant control method for an input-parallel-output series double-active-bridge switch Guan Kailu according to any one of claims 1 to 8, and includes: The fault detection module is used for collecting voltage and current signals of each double-active-bridge module in real time and judging the specific position of the open-circuit fault of the switching tube; The fault-tolerant control module is used for executing a fault-tolerant control strategy according to the fault position information of the switching tube and outputting an adjusted duty ratio and phase-shift angle signal; The voltage equalizing control module is used for calculating a voltage reference value V ref_state of each module by adopting a multi-stage self-adaptive control algorithm; The amplitude limiting protection module is used for limiting the voltage reference value V ref_state ; And the driving module is used for generating driving pulses of the switching tubes according to the output signals of the fault-tolerant control module and the voltage reference value V ref_state after amplitude limiting.
  10. 10. A terminal device comprising a processor and a memory, characterized in that the memory stores a computer program, which is loaded by the processor and which performs a fault-tolerant control method of an input-parallel output-series double active bridge switch Guan Kailu as claimed in any one of claims 1-8.

Description

Fault tolerance control method for input-parallel output series double-active-bridge switch Guan Kailu Technical Field The invention relates to the technical field of power electronics, in particular to a fault tolerance control method for an input-parallel output series double-active-bridge switch Guan Kailu. Background With the promotion of global energy Internet and 'double carbon' targets, the distributed new energy power generation technology represented by photovoltaic and wind power, and application scenes such as a direct current micro-grid, an electric vehicle super charging station, a Solid State Transformer (SST) and the like are rapidly developed. In these applications, achieving high efficiency energy exchange between the high voltage dc bus and the low voltage dc bus is a core key technology. Dual Active Bridge (DAB) converters have become the preferred topology in this field by virtue of their inherent primary-secondary side electrical isolation characteristics, ease of implementing zero voltage on (ZVS) soft switching over the full load range, and ability for bi-directional energy flow. In order to meet the requirements of a medium-high voltage (such as 10kV or higher) direct current distribution network, a single DAB converter is limited by the voltage withstand level of a power semiconductor device (such as a SiC MOSFET or IGBT), and is often difficult to directly apply. Thus, modular combined architecture employing Input Parallel Output Series (IPOS) becomes the dominant solution. The IPOS architecture shares large current through parallel connection of input sides, and output sides are connected in series to bear high voltage, so that the IPOS architecture has the advantages of high modularization degree, strong expansibility, high redundancy and the like. However, the DAB converter is used as a high-frequency switching device, and a power switching tube in the DAB converter works under severe working conditions of high voltage, high current and high-frequency thermal cycle for a long time, so that the DAB converter is one of components with highest inefficiency in a system. The switching tube faults are mainly classified into short-circuit faults and open-circuit faults. Short circuit faults usually cause overcurrent, the circuit needs to be cut in microsecond level through desaturation detection (Desaturation Detection) of a hardware driving circuit, and open circuit faults (such as caused by loss of a gate driving signal, thermal fatigue drop of bonding wires or breakage of chips in a module) are more concealed, so that overcurrent protection cannot be triggered immediately, but the damage is also huge. When the DAB converter has a switching tube open circuit fault, the asymmetry of the circuit topology can cause serious distortion of the voltage waveform of the primary side or the secondary side of the high-frequency transformer. According to the principle of inductive volt-second balance, if the positive volt-second product and the negative volt-second product applied across the inductor (or transformer winding) are not equal, the inductor current will not return to its initial value after one period has ended, thereby creating a continuously accumulated dc bias component. Because the high-frequency transformer is generally designed for transmitting alternating current signals, the magnetic core of the high-frequency transformer is small in size, short in magnetic circuit and extremely weak in DC bias magnetic resistance. Upon the occurrence of a dc bias, the transformer core will rapidly deviate from the linear region and enter a unidirectional saturated state. The magnetic saturation can lead the excitation inductance to drop to be close to zero sharply, and then the primary side or secondary side current is instantaneously increased (possibly reaching several times of rated current), and the overcurrent can not only sharply increase the conduction loss of the system, so that the radiator is overheated, but also directly burn the rest healthy switch tube or lead to the insulation breakdown of the transformer, even cause fire, and lead to paralysis of the whole converter system. For an IPOS system comprising multiple DAB sub-modules, more complex inter-module voltage cooperative control challenges are faced in addition to the risk of failure within a single module. Since the output sides are connected in series, the output currents of the modules are the same, but the output voltages thereof depend on the respective power transmission capabilities. When a certain module fails and operates in a derated mode or the parameters of the modules are different, the output voltage among the modules is easy to be unbalanced. For example, the faulty module voltage drops, and in order to maintain the total output voltage unchanged, the closed loop controller can force the voltage of the remaining normal modules high, resulting in the normal modules being subject to an overvoltage risk. The exi