A short-circuit recovery voltage limiting method for a three-stage DC generator

Abstract

The application discloses a short-circuit recovery voltage limiting method for a three-stage direct-current generator, which detects output voltage U0 of the three-stage direct-current generator and load current i L to determine the state of the load, adjusts the output state of the three-stage direct-current generator according to the state of the load by using an asymmetric half-bridge excitation topology, detects the generation output voltage and the load current to determine characteristic states such as a short-circuit state, a short-circuit recovery state and a first voltage peak falling edge after short-circuit recovery, and closes upper and lower excitation power tubes in combination with the asymmetric half-bridge during short-circuit recovery, so that the two power tubes are opened only when the first voltage peak falls to a voltage undervoltage value after short-circuit recovery, and voltage overshoot during short-circuit recovery of the three-stage direct-current generator is limited to the maximum extent, and the safety of a power supply system is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to a short-circuit recovery voltage limiting method for a three-stage DC generator. BACKGROUND

[0002] In an aircraft power supply system, an engine or an auxiliary power unit drives a three-stage DC generator in the power generation system, and outputs a specified voltage through the adjustment of a three-stage DC generator controller. The voltage output by the three-stage DC generator is distributed to various power consumption loads through a power distribution system. When a short-circuit fault occurs in the power consumption load, the power supply system requires the three-stage DC generator to output stable short-circuit current to ensure that the power distribution box performs short-circuit protection, and the three-stage DC generator controller needs to control the short-circuit current within the system bearing range. The short-circuit current usually needs to be greater than 3 times the rated current, and the maximum voltage of the three-stage DC generator when recovering from the short-circuit state to normal power supply should not exceed the non-normal transient maximum voltage of 350V required by the national military standard. This function of the three-stage DC generator system mainly tests the output of the three-stage DC generator and the control of the controller.

[0003] For the above short-circuit working condition, the three-stage DC generator controller based on a hardware voltage regulator mainly adopts two methods to control the short-circuit recovery voltage. One is a single power tube-based field control circuit. When the output voltage of the three-stage DC generator is detected to be overvoltage, the field current is turned off, and a demagnetizing resistor is added to quickly dissipate the field current. An absorption resistor and a power tube are added to control the transient overvoltage. The other method is based on an asymmetric half-bridge field control topology. When the output overvoltage of the three-stage DC generator is detected, the upper and lower power tubes are turned off. Both methods can suppress the overvoltage of the three-stage DC generator output. The second method uses the negative voltage freewheeling mode of the asymmetric half-bridge to dissipate the field current faster. However, this hardware detection-based method is not suitable for different parameter generators, and there are cases where the short-circuit recovery voltage cannot be suppressed within 350V. SUMMARY

[0004] The purpose of the present application is to meet the requirements of uninterrupted power supply of the power generation system in the case of short-circuit working condition of the aircraft power supply load. The present application provides a short-circuit recovery voltage limiting technology based on short-circuit characteristic detection, which can suppress the transient overvoltage of the three-stage DC generator output during short-circuit recovery, and ensure that the aircraft power distribution system and the subsequent power consumption equipment work within a safe voltage range. This technology is of great significance to improve the safety and robustness of the aircraft power supply system.

[0005] Technical scheme of the present application:

[0006] The application discloses a short-circuit recovery voltage limiting method for a three-stage DC generator, which comprises the following steps: detecting the output voltage U0 of the three-stage DC generator and the load current i L , judging the state of the load according to the output voltage U0 and the load current i L , and adjusting the output state of the three-stage DC generator by using an asymmetric half-bridge excitation topology according to the state of the load.

[0007] S1: collecting the output voltage U0 of the three-stage DC generator and the load current i N ;

[0008] S2: judging the short-circuit state based on a preset short-circuit voltage threshold U1 and a short-circuit current threshold k1x i L : when U0 N <k1x i N , the short-circuit state is determined, a short-circuit identifier flg_sht is set to 1, otherwise, flg_sht is set to 0 and normal excitation adjustment is maintained;

[0009] S3: when flg_sht=1, judging the short-circuit recovery state based on a preset recovery voltage threshold U2 and a recovery current threshold k2x i L : when U0 N >k2x i N , the short-circuit recovery state is determined, a recovery identifier flg_rst is set to 1, otherwise, flg_rst is set to 0 and short-circuit control is maintained;

[0010] S4: when flg_rst=1, the upper power tube Q1 and the lower power tube Q2 are turned off, and the excitation circuit is cut off to suppress voltage overshoot;

[0011] S5: when flg_rst=1, judging the voltage rising state based on a preset voltage rising threshold U3: when U0 L 0>>U3, a rising identifier flg_up is set to 1, otherwise, flg_up is set to 0 and the power tube is maintained to be turned off;

[0012] S6: when flg_up=1, a voltage recovery threshold U4 is set, and normal excitation adjustment is recovered: when U0 L 1><U4, the upper power tube Q1 and the lower power tube Q2 are turned on, the complementary PWM excitation control is recovered, and flg_sht, flg_rst and flg_up are all reset to 0, otherwise, the power tube is maintained to be turned off.

[0013] Wherein, i L 2>is the rated current of the three-stage DC generator.

[0014] The output voltage of the three-stage DC generator after short-circuit recovery in the steps S2-S6 is limited within 350V.

[0015] In the step S2, k1>2.

[0016] In the step S3, the value of k2 is in the range of 1≤k2<2.

[0017] In the step S4, the value of U2 is in the range of 10V≤U2≤100V, and U2 is not lower than the actual output voltage of the three-stage DC generator in the short-circuit state in the step S3.

[0018] U4∈[U2,U3], U2>U1, U3>U2.

[0019] U4 is the under-voltage value after the output voltage of the three-stage DC generator in the short-circuit recovery state drops through the first peak.

[0020] U4 can be the under-voltage protection value.

[0021] The maximum output voltage of the three-stage DC generator in the short-circuit recovery state is not lower than and approaches the output voltage of the three-stage DC generator in the short-circuit state.

[0022] The present application has the following beneficial effects: by detecting the output voltage and the load current, the short-circuit state, the short-circuit recovery state, the falling edge of the first voltage peak after the short-circuit recovery, and other characteristic states are determined, the asymmetric half-bridge is combined, the upper and lower excitation power tubes are closed in the short-circuit recovery, and the two power tubes are opened only when the first voltage peak after the short-circuit recovery drops to the under-voltage value, so that the voltage overshoot of the three-stage DC generator in the short-circuit recovery is limited to the maximum extent, and the safety of the power supply system is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flow chart of the short-circuit recovery voltage limiting technology;

[0024] Figure 2 is a principle diagram of the asymmetric half-bridge excitation control topology;

[0025] Figure 3 is a schematic diagram of the detection of various variables of the short-circuit recovery voltage limiting technology. DETAILED DESCRIPTION

[0026] Embodiment 1: overall architecture of the system

[0027] The excitation control system includes four modules:

[0028] Excitation control circuit module: composed of upper power tube Q1, lower power tube Q2 and diode D1, D2 asymmetric half bridge topology circuit; sensing module: containing voltage sensor, current sensor, 12-bit ADC module, sampling frequency 20 kHz; core control module: using MCU chip (such as TMS320F2835), built-in short circuit state determination unit, recovery state determination unit, power tube drive control unit, PWM generation unit, and configure flg_sht, flg_rst, flg_up three state identification registers (initial value is 0); drive module: using isolation type drive chip, converting the logic signal output by MCU into power tube drive signal.

[0029] Embodiment 2: control method steps

[0030] Step S1: parameter acquisition

[0031] The voltage sensor collects the generator output voltage U0 (range 0-400V) in real time, and the current sensor collects the load current iL (range 0-800A) in real time. The sampling signal is converted by the ADC module and input to the core control module at a frequency of 20 kHz. Among them, the rated current of the generator iN = 180A, and the rated voltage of the generator UN = 270V.

[0032] Step S3: short circuit state determination

[0033] The preset short circuit voltage threshold U1 = 10V (10% lower than the normal output voltage, to avoid misjudgment), and the short circuit current threshold k1 x iN = 450A (k1 = 2.5 > 2);

[0034] If U0 < 10V and iL > 450A, it is determined that the short circuit state is set, flg_sht = 1; otherwise flg_sht = 0, maintaining normal PWM excitation regulation.

[0035] Step S4: recovery state determination

[0036] Only when flg_sht = 1 is executed, the preset recovery voltage threshold U2 = 50V (10V ≤ U2 ≤ 100V, and higher than the actual output voltage 3-5V during short circuit), and the recovery current threshold k2 x iN = 225A (k2 = 1.25, 1 ≤ k2 < 2);

[0037] If U0 > 50V and iL < 225A, it is determined that the short circuit recovery state is set, flg_rst = 1; otherwise flg_rst = 0, maintaining short circuit control (Q1, Q2 are both off).

[0038] Step S5: overvoltage suppression control

[0039] When flg_rst=1, the core control module outputs a low level signal to the drive module, which closes the gate drive voltage of Q1 and Q2 (≤0V) and cuts off the excitation circuit. At this time, the energy of the excitation winding is discharged through the freewheeling diode, avoiding voltage overshoot.

[0040] Step S6: Voltage rising state determination

[0041] Only when flg_rst=1, preset voltage rising threshold U3=275V (<350V safety threshold, and higher than U2=20V) is executed;

[0042] If U0>275V, it means that the voltage is recovering, and flg_up=1 is set. Otherwise, flg_up=0, and Q1 and Q2 continue to be closed.

[0043] Step S7: Normal excitation recovery

[0044] When flg_up=1, preset voltage recovery threshold U4=245V (U4∈[U2,U3]) is executed;

[0045] If U0<245V, the core control module outputs a PWM signal to the drive module, which opens Q1 and Q2, recovers PWM control, and resets flg_sht, flg_rst, and flg_up to 0, completing a short circuit recovery cycle.

Claims

1. A short-circuit recovery voltage limiting method for a three-stage DC generator, judging the state of a load by detecting an output voltage U0 of the three-stage DC generator and a load current i L and regulating the output state of the three-stage DC generator using an asymmetric half-bridge excitation topology according to the state of the load, characterized in that The specific steps are as follows: S1: Collecting output voltage U0 and load current i of the three-stage DC generator L ; S2: determine the short-circuit state based on the preset short-circuit voltage threshold U1 and short-circuit current threshold k1x i N : when U0 < U1 and i L > k1x i N , determine the short-circuit state, set the short-circuit flag flg_sht = 1; otherwise, set flg_sht = 0 and maintain normal excitation regulation; S3: When flg_sht = 1, based on the preset recovery voltage threshold U2 and recovery current threshold k2 x i N , determine the short-circuit recovery state: when U0 > U2 and i L < k2 x i N , determine the short-circuit recovery state, set the recovery flag flg_rst = 1; otherwise, set flg_rst = 0 and maintain short-circuit control; S4: When flg_rst=1, turn off the upper power transistor Q1 and the lower power transistor Q2 to cut off the excitation circuit and suppress voltage overshoot; S5: When flg_rst=1, determine the voltage rise state based on the preset voltage rise threshold U3: when U0>U3 is satisfied, set the rise flag flg_up=1; otherwise, set flg_up=0 and keep the power transistor off; S6: When flg_up=1, set the voltage recovery threshold U4 to restore normal excitation regulation: when U0<U4 is satisfied, turn on the upper power transistor Q1 and the lower power transistor Q2 to restore complementary PWM excitation control, and reset flg_sht, flg_rst, and flg_up to 0; otherwise, keep the power transistors off. wherein i N is the rated current of the three-stage DC generator; In steps S2-S6, the output voltage of the three-stage DC generator after short-circuit recovery is limited to within 350V. In step S2, k1 > 2; In step S3, the value range of k2 is 1≤k2<2; The value of U2 is in the range of 10V≤U2≤100V, and U2 is not lower than the actual output voltage of the three-stage DC generator under the short-circuit state in step S3. U4∈[U2,U3], U2>U1, U3>U2.

2. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: U4 is the undervoltage value that the output voltage of the three-stage DC generator drops after the first peak during short-circuit recovery.

3. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 2, characterized in that: The value of U4 can be an undervoltage protection value.

4. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: When the three-stage DC generator recovers from a short circuit, its maximum output voltage is not lower than and approaches the output voltage of the three-stage DC generator during the short circuit.

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