CN-121984368-A - Current sharing control method and device based on parallel SiC MOSFET grid inverter

CN121984368ACN 121984368 ACN121984368 ACN 121984368ACN-121984368-A

Abstract

A current sharing control method and device based on parallel SiC MOSFET grid-structured inverter relates to a current sharing control method and device. The invention aims to solve the problem that the parallel SiC MOSFET has unbalanced transient current in the switching process. According to the invention, by introducing an active driving circuit, current signals of all parallel SiC MOSFET branches are collected, and after calculation processing, rising edge and falling edge time delay of driving signals of all devices are dynamically regulated, so that transient current imbalance of the parallel SiC MOSFETs in the switching process is effectively inhibited. The current equalizing device is independent of a core control loop of the grid-built inverter, and can improve the capacity of the inverter and avoid increasing the complexity of a system control strategy. The invention belongs to the technical field of inverter control.

Inventors

XU HONGYAN
DONG CHENGLIN
WANG YIZE
ZUO HONGJIAN
YU ZEPING
LI DONGFU
WANG XU
WU ZHIQIANG
WANG JIACHEN
REN ZHENYU
Ma Wanshi

Assignees

国网吉林省电力有限公司长春供电公司

Dates

Publication Date: 20260505
Application Date: 20260127

Claims (6)

1. A current sharing control method based on parallel SiC MOSFET grid-built inverter is characterized by comprising the following specific steps: Step 1, setting parallel devices A current sharing control device; step 2, inputting a driving signal Then, the on-off delay time calculated by the current difference of the parallel SiC MOSFETs in the previous period is extracted, and a driving signal corresponding to the parallel SiC MOSFETs is generated At the same time drive signal Collecting branch current of the parallel SiC MOSFET at the moment of rising edge and falling edge respectively; step 3, parallel SiC MOSFET branch current passes through sampling resistor The differential operational amplifier is converted into a voltage signal, and then transmitted to the CPLD through the ADC; and 4, the CPLD calculates the current difference of each parallel device in the switching-on and switching-off processes.
2. The current sharing control method based on parallel SiC MOSFET grid-structured inverter as claimed in claim 1, wherein the parallel SiC MOSFET is formed by 、、、 The parallel SiC MOSFET is driven and controlled by an active driver, and a sampling resistor is arranged in the active driver Sampling resistor Is connected with the drain and source of the parallel SiC MOSFET.
3. The current sharing control method based on parallel SiC MOSFET grid-connected inverter as claimed in claim 1, wherein the CPLD calculates the current difference of each parallel device in the switching-on and switching-off process as follows: (1), In the formula (1), Representing parallel connection of The difference between the individual devices and the theoretical equilibrium current, The number of SiC MOSFETs in parallel is indicated, Indicating the j-th number of all parallel SiC MOSFETs, Representing the drain-source current of the ith device in parallel.
4. The current sharing control method based on parallel SiC MOSFET grid inverter according to claim 1, wherein for parallel SiC MOSFET switching process, current is flowing at drain and source (Here What is defined by (c) rise phase, by virtue of its voltage-current relationship, includes: (2), in the formula (2), Indicating that the drive system is driving a voltage, Representing the parasitic inductance of the gate drive loop, Representing the input capacitance of the SiC MOSFET, Representing the transconductance of the light, Representing the gate-source drive voltage, The gate drive resistance is shown as being, Represents the threshold voltage of the SiC MOSFET; Solving the turn-on process SiC MOSFET by the formula (2) The slope is: (3)。
5. the current sharing control method based on parallel SiC MOSFET grid-connected inverter as set forth in claim 1 or 4, wherein during the turn-off process of the SiC MOSFET, the current sharing control method is characterized in that The falling stage can solve the SiC MOSFET in the turn-off process by means of the voltage-current relationship The slope is: (4), In the formula (4) of the present invention, Representing a negative voltage of the drive system; Combining the formula (3) and the formula (4), collecting current differences of all parallel branches of the parallel SiC MOSFETs at the moment of switching on and switching off in the last switching period, calculating the next switching period, and connecting the delay time of the driving signal of each parallel SiC MOSFET at the rising edge and the delay time of the switching off falling edge in parallel On delay time of individual devices Off delay time Expressed as: (5), (6), in the formulas (5) and (6), Indicating the on-process difference between the ith device and the theoretical parallel balanced current, Representing the drain-source current of the j-th device of all n devices connected in parallel, Representing the shutdown process difference between the ith device and the theoretical parallel balanced current; When a driving signal is input to the CPLD, the CPLD reads the delay time of the rising edge and the falling edge of each current parallel SiC MOSFE And Generating corresponding device driving signals, and Respectively extracting parallel branch current after differential operational amplification processing in one-time turn-on or turn-off process, and calculating parallel device delay time of the next switching period And 。
6. The current-sharing control device based on the parallel SiC MOSFET grid-structured inverter is characterized by comprising a parallel SiC MOSFE structure and an active driver, wherein the parallel SiC MOSFE structure is driven by the active driver, and a sampling resistor is arranged in the active driver Sampling resistor Is connected with the drain and source of the parallel SiC MOSFE structure, and the parallel SiC MOSFE structure is formed by 、、、 Four circuits.

Description

Current sharing control method and device based on parallel SiC MOSFET grid inverter Technical Field The invention relates to a current sharing control method and device, and belongs to the technical field of inverter control. Background Compared with a grid inverter based on a high-power SiC MOSFET device module, the inverter cost based on parallel discrete SiC MOSFET devices can depend on lower cost to improve the current level of the grid inverter. The parallel current sharing technology mainly has the key challenges of three aspects, namely, the distribution parameter difference among parallel devices comprises parasitic parameters such as parasitic capacitance, transconductance and grid resistance, delay time exists among stage components in the switching process of the parallel devices, unbalanced distribution of parallel currents is caused, the driving branch and a power current loop are asymmetric in a multi-device parallel connection mode, parasitic inductance difference is introduced to cause current unbalance of the parallel branches and overhigh current overshoot, device current stress is increased, the contradictory relation between the traditional current sharing control scheme and device loss is increased, reasonable symmetrical layout or active voltage sharing control strategies both lead to cost increase, the system control complexity under the application scene of the converter is increased to restrict wide application of the converter, and the compact layout leads to good control of heat balance among devices, but electromagnetic coupling and oscillation. In summary, parallel current sharing of SiC MOSFETs is a known but not yet fully solved engineering problem, and requires systematic and refined optimization from device selection, circuit design, PCB layout, drive design and thermal management, and currently lacks a simple and scalable SiC MOSFET current sharing control scheme. Disclosure of Invention The invention provides a current sharing control method and device based on a parallel SiC MOSFET grid inverter, which aims to solve the problem that transient current imbalance exists in the switching process of a parallel SiC MOSFET. The invention adopts the technical scheme that the current sharing control method based on the parallel SiC MOSFET grid inverter comprises the following steps of: Step 1, setting parallel devices A current sharing control device; step 2, inputting a driving signal Then, the on-off delay time calculated by the current difference of the parallel SiC MOSFETs in the previous period is extracted, and a driving signal corresponding to the parallel SiC MOSFETs is generatedAt the same time drive signalCollecting branch current of the parallel SiC MOSFET at the moment of rising edge and falling edge respectively; step 3, parallel SiC MOSFET branch current passes through sampling resistor The differential operational amplifier is converted into a voltage signal, and then transmitted to the CPLD through the ADC; and 4, the CPLD calculates the current difference of each parallel device in the switching-on and switching-off processes. Further, the parallel SiC MOSFET is composed of、、、The parallel SiC MOSFET is driven and controlled by an active driver, and a sampling resistor is arranged in the active driverSampling resistorIs connected with the drain and source of the parallel SiC MOSFET. Further, the formula for calculating the current difference of each parallel device in the switching-on and switching-off process by the CPLD is as follows: (1), In the formula (1), Representing parallel connection ofThe difference between the individual devices and the theoretical equilibrium current,The number of SiC MOSFETs in parallel is indicated,Indicating the j-th number of all parallel SiC MOSFETs,Representing the drain-source current of the ith device in parallel. Further, for parallel SiC MOSFET switching process, the current is at the drain-sourceThe rising stage comprises the following steps depending on the voltage-current relationship: (2), in the formula (2), Indicating that the drive system is driving a voltage,Representing the parasitic inductance of the gate drive loop,Representing the input capacitance of the SiC MOSFET,Representing the transconductance of the light,Representing the gate-source drive voltage,The gate drive resistance is shown as being,Represents the threshold voltage of the SiC MOSFET; Solving the turn-on process SiC MOSFET by the formula (2) The slope is: (3)。 further, during the turn-off process of the SiC MOSFET The falling stage can solve the SiC MOSFET in the turn-off process by means of the voltage-current relationshipThe slope is: (4), In the formula (4) of the present invention, Representing a negative voltage of the drive system; Combining the formula (3) and the formula (4), collecting current differences of all parallel branches of the parallel SiC MOSFETs at the moment of switching on and switching off in the last switching period, calcul