Short-circuit recovery voltage limiting method for three-stage direct-current generator

Abstract

The invention discloses a short-circuit recovery voltage limiting method for a three-stage direct-current generator, and the method comprises the steps: judging the state of a load through detecting the output voltage U0 and load current iL of the three-stage direct-current generator, and adjusting the output state of the three-stage direct-current generator through employing an asymmetric half-bridge excitation topology according to the state of the load. By detecting power generation output voltage and load current, a short-circuit state, a short-circuit recovery state, a falling edge of a first voltage wave crest after short-circuit recovery and other characteristic states are determined, and an upper excitation power tube and a lower excitation power tube are closed during short-circuit recovery in combination with an asymmetric half-bridge. The two power tubes are started until the first voltage peak drops to the voltage undervoltage value after the short circuit is recovered, so that the voltage overshoot when the output short circuit of the three-stage direct-current generator is recovered can be 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 supply system, and a specified voltage is output 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 maximum voltage of 350 V of the abnormal transient required by the national military standard. The 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 excitation control circuit. When the output voltage of the three-stage DC generator is detected to be overvoltage, the excitation current is turned off, and a demagnetizing resistor is added to quickly dissipate the excitation 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 excitation 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 excitation current faster, but this hardware detection-based method is not suitable for different parameters of the generator, and there is a situation that the short-circuit recovery voltage cannot be suppressed within 350 V. SUMMARY

[0004] The purpose of the present application is: for the short-circuit working condition of the aircraft power supply load, in order to meet the requirement of uninterrupted power supply of the power supply system, 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 in a safe voltage range. It is of great significance to improve the safety and robustness of the aircraft power supply system.

[0005] The technical scheme of the present application is: A short-circuit recovery voltage limiting method for a three-stage DC generator, which detects the output voltage U0 and load current i of the three-stage DC generatorL To determine the load status, an asymmetrical half-bridge excitation topology is used to adjust the output status of the three-stage DC generator based on the load status. The specific steps are as follows: S1: Collect the output voltage U0 and load current i of the three-stage DC generator. L ; S2: Based on the preset short-circuit voltage threshold U1 and short-circuit current threshold k1×i N Determine the short circuit state: when U0 < U1 and i L >k1×i N If the condition is short-circuited, the short-circuit flag flg_sht=1 is set; otherwise, flg_sht=0 is set and normal excitation regulation is maintained. S3: When flg_sht=1, based on the preset recovery voltage threshold U2 and recovery current threshold k2×i N Determine the short-circuit recovery state: when U0 > U2 and i L <k2×i N If the condition is met, it is determined to be a short-circuit recovery state, and the recovery flag flg_rst=1 is set; otherwise, flg_rst=0 is set and short-circuit control is maintained. 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. Among them, i N This is the rated current of a three-stage DC generator.

[0006] In steps S2-S6, the output voltage of the three-stage DC generator after short-circuit recovery is limited to within 350V.

[0007] In step S2, k1 > 2.

[0008] In step S3, the value range of k2 is 1 ≤ k2 < 2.

[0009] In 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 under the short-circuit state in step S3.

[0010] U4∈[U2,U3], U2>U1, U3>U2.

[0011] U4 is the undervoltage value that the output voltage of the three-stage DC generator drops after the first peak during short-circuit recovery.

[0012] The value of U4 can be an undervoltage protection value.

[0013] 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.

[0014] The beneficial effects of this invention are as follows: By detecting the generator output voltage and load current, the short-circuit state, short-circuit recovery state, and the falling edge of the first voltage peak after short-circuit recovery are determined. Combined with an asymmetrical half-bridge, the upper and lower excitation power transistors are turned off during short-circuit recovery, and only when the first voltage peak after short-circuit recovery drops to the undervoltage value are the two power transistors turned on. This can limit the voltage overshoot during short-circuit recovery of the three-stage DC generator output to the greatest extent and ensure the safety of the power supply system. Attached Figure Description

[0015] Figure 1 This is a flowchart of short-circuit recovery voltage limiting technology; Figure 2 This is a schematic diagram of an asymmetric half-bridge excitation control topology; Figure 3 This is a schematic diagram of the detection of various variables in the short-circuit recovery voltage limiting technology. Detailed Implementation

[0016] Example 1: System Overall Architecture The excitation control system consists of four main modules: The excitation control circuit module consists of an asymmetric half-bridge topology circuit composed of upper power transistor Q1, lower power transistor Q2, and diodes D1 and D2; the sensing module includes a voltage sensor, a current sensor, and a 12-bit ADC module with a sampling frequency of 20kHz; the core control module uses an MCU chip (such as TMS320F2835) with built-in short-circuit state determination unit, recovery state determination unit, power transistor drive control unit, and PWM generation unit, and is configured with three status flag registers flg_sht, flg_rst, and flg_up (all with initial values ​​of 0); the drive module uses an isolated drive chip to convert the logic signals output by the MCU into power transistor drive signals.

[0017] Example 2: Control Method Steps Step S1: Parameter Acquisition The voltage sensor collects the generator output voltage U0 in real time (range 0-400V), and the current sensor collects the load current iL in real time (range 0-800A). The sampled signals are converted by the ADC module and input to the core control module at a frequency of 20kHz. The generator rated current iN=180A and the generator rated voltage UN=270V.

[0018] Step S3: Short Circuit Status Determination The preset short-circuit voltage threshold U1 = 10V (10% lower than the normal output voltage to avoid misjudgment) and short-circuit current threshold k1 × iN = 450A (k1 = 2.5 > 2). If U0 < 10V and iL > 450A, it is determined to be a short circuit state, and flg_sht = 1 is set; otherwise flg_sht = 0, and normal PWM excitation regulation is maintained.

[0019] Step S4: Recovery Status Determination Execute only when flg_sht=1, preset recovery voltage threshold U2=50V (10V≤U2≤100V, and higher than the actual output voltage during short circuit by 3-5V), recovery current threshold k2×iN=225A (k2=1.25, 1≤k2<2). If U0 > 50V and iL < 225A, it is determined to be a short-circuit recovery state, and flg_rst = 1 is set; otherwise flg_rst = 0, and short-circuit control is maintained (Q1 and Q2 are both turned off).

[0020] Step S5: Overvoltage Suppression Control When flg_rst=1, the core control module outputs a low-level signal to the drive module, turning off the gate drive voltage of Q1 and Q2 (≤0V) and cutting off the excitation circuit; at this time, the energy of the excitation winding is discharged through the freewheeling diode to avoid voltage overshoot.

[0021] Step S6: Determine the voltage rise state Execute only when flg_rst=1, with a preset voltage rise threshold of U3=275V (<350V safety threshold, and higher than U2=20V). If U0 > 275V, it means the voltage is recovering, so set flg_up = 1; otherwise, flg_up = 0, and continue to keep Q1 and Q2 off.

[0022] Step S7: Normal excitation recovery When flg_up=1, the preset voltage recovery threshold U4=245V (U4∈[U2,U3]); If U0 < 245V, the core control module outputs a PWM signal to the drive module, turns on Q1 and Q2, restores PWM control, and resets flg_sht, flg_rst, and flg_up to 0, completing one short-circuit recovery cycle.

Claims

1. A short-circuit recovery voltage limiting method for a three-stage DC generator, which involves detecting the output voltage U0 and load current i of the three-stage DC generator. L The method determines the load state and adjusts the output state of the three-stage DC generator using an asymmetrical half-bridge excitation topology based on the load state. Its characteristic is... The specific steps are as follows: S1: Collect the output voltage U0 and load current i of the three-stage DC generator. L ; S2: Based on the preset short-circuit voltage threshold U1 and short-circuit current threshold k1×i N Determine the short circuit state: when U0 < U1 and i L >k1×i N If the condition is short-circuited, the short-circuit flag flg_sht=1 is set; otherwise, flg_sht=0 is set and normal excitation regulation is maintained. S3: When flg_sht=1, based on the preset recovery voltage threshold U2 and recovery current threshold k2×i N Determine the short-circuit recovery state: when U0 > U2 and i L <k2×i N If the condition is met, it is determined to be a short-circuit recovery state, and the recovery flag flg_rst=1 is set; otherwise, flg_rst=0 is set and short-circuit control is maintained. 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. Among them, i N This is the rated current of a three-stage DC generator.

2. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: In steps S2-S6, the output voltage of the three-stage DC generator after short-circuit recovery is limited to within 350V.

3. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: In step S2, k1 > 2.

4. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: In step S3, the value range of k2 is 1 ≤ k2 < 2.

5. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: In 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 under the short-circuit state in step S3.

6. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 1, characterized in that: U4∈[U2,U3], U2>U1, U3>U2.

7. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 6, 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.

8. The short-circuit recovery voltage limiting method for a three-stage DC generator according to claim 7, characterized in that: The value of U4 can be an undervoltage protection value.

9. 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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