Method for suppressing bus oscillation of multi-voltage-level direct current distribution network and converter

Abstract

The application provides a multi-voltage-grade DC power distribution network bus oscillation suppression method and a converter. The method comprises the following steps: when a load mutation occurs, the change rate of a corresponding bus voltage is detected; an adaptive virtual impedance is obtained by using an adaptive impedance solving algorithm according to the bus voltage change rate; and the duty cycle of the converter is obtained according to the adaptive virtual impedance and the voltage difference of two DC buses. Thus, the multi-voltage-grade bus voltage fluctuation and oscillation are effectively suppressed, and the stability of system operation is improved.

Claims

1. A method for suppressing DC bus oscillations at multiple voltage levels, characterized in that, The method includes: When the load changes abruptly, the rate of change of the corresponding bus voltage is detected; Based on the bus voltage change rate, an adaptive impedance solution algorithm is used to obtain the adaptive virtual impedance; The duty cycle of the converter is obtained based on the adaptive virtual impedance and the voltage difference between the two DC buses. The adaptive impedance solution algorithm includes: The rate factor λ of the bus voltage change is obtained based on the bus voltage change rate. According to the speed factor λ, the initial virtual impedance Z0 and the impedance coefficient Z of the speed factor k Obtaining an adaptive virtual impedance; The rate factor λ of the bus voltage change is obtained from the bus voltage change rate using the following formula: ， Among them, U Bus The bus voltage due to load abrupt change. The rate of change of bus voltage; The adaptive virtual impedance Z is obtained by the following equation from the speed factor λ, the initial virtual impedance Z0 and the impedance coefficient Z of the speed factor k obtaining an adaptive virtual impedance Z: ， Where Z0 represents the initial virtual impedance, which is set according to the impedance model of each bus and is generally resistive-inductive; Z k The impedance coefficient representing the speed factor is generally resistive-capacitive and is used to adjust the magnitude of the speed factor. It is set according to the system's sensitivity to sudden load changes. The initial virtual impedance Z0 and the speed factor impedance coefficient Z are... k They can be represented as: Where R0 is the real part of the initial virtual impedance; R k X is the real part of the velocity factor impedance coefficient; X0 is the imaginary part of the initial virtual impedance; X k is the imaginary part of the velocity factor impedance coefficient; j is the imaginary unit.

2. The method for suppressing DC bus oscillations at multiple voltage levels according to claim 1, characterized in that, The step of obtaining the converter's duty cycle based on the adaptive virtual impedance and the DC bus voltage difference includes: The current setpoint of the current loop is obtained based on the virtual impedance output by the adaptive impedance solver and the voltage difference between the two DC buses. Obtain the difference between the given current value and the output current of the converter; The difference is passed through a PI circuit and a PWM generator to obtain the converter's duty cycle.

3. The method for suppressing DC bus oscillations at multiple voltage levels according to claim 2, characterized in that, The current setpoint of the current loop is obtained by dividing the virtual impedance output by the adaptive impedance solver by the absolute value of the voltage difference between the two DC buses.

4. A converter, characterized in that, The converter includes an adaptive impedance solver, which employs the adaptive impedance solving algorithm described in any one of claims 1-3.

5. A converter according to claim 4, characterized in that, The transfer function D corresponding to the converter is obtained using the following formula: Where Z0 represents the initial virtual impedance; Z k The impedance coefficient representing the velocity factor; U Bus Indicates the bus voltage during load abrupt changes; 1 / U dc Indicates the voltage modulation ratio; H PI (s) represents the transfer function of the PI element, U Bus1 and U Bus2 These represent the voltages of the two DC bus lines respectively; T represents the switching time period; s is a complex parameter, i o This is the output current of the converter.

6. An aircraft electrical system, characterized in that, The aircraft electrical system includes the converter as described in claim 4 or 5.

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