Active current sharing strategy for master-slave cooperative control

Abstract

The invention relates to the technical field of semiconductors, in particular to an active current sharing strategy for master-slave cooperative control. According to the technical scheme, the system comprises an S < iC > device dynamic current sampling unit, a dynamic current information conversion unit, a dynamic current information processing unit and a variable grid resistance driving circuit, wherein the S < iC > device dynamic current sampling unit is used for collecting real-time current information of the S < iC > device in the turn-on transient process. The method can effectively solve the problem of current imbalance caused by parameter difference of multi-device parallel connection, is especially suitable for parallel connection of three or more modules, guarantees the current sharing effect through fine active current sharing control, adopts a master-slave cooperative control strategy, solves the problem of single-point fault of a main module in traditional master-slave control, and improves the robustness of the system. The device is prevented from being damaged due to excessive current and voltage stress caused by current imbalance, stable operation of the system is guaranteed, current distribution can be effectively adjusted in the load switching process, and stable operation of the system is guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an active current sharing strategy for master-slave collaborative control. Background Art

[0002] The third generation of power devices represented by SiC power devices have excellent performances such as high speed, high temperature, high voltage, and high efficiency. They will greatly improve the efficiency and power density of electrical equipment and systems, and determine the future form of power conversion equipment and power grid technology. For high-power conversion systems, the rated power of a single SiC power device is low, and multiple SiC devices are often required to be used in parallel. However, the parallel application of devices will inevitably bring about the problem of uneven current distribution. Ideally, the total load current of the parallel SiC power device system is evenly divided by each device participating in the parallel connection. However, due to factors such as production process errors, the parameters of each device of the SiC device itself will always be different. Although these differences can be minimized, they cannot be completely eliminated. Since the parameters of the devices participating in the parallel connection cannot be exactly the same, if no measures are taken and they are simply connected in parallel directly, it will not be possible to ensure that each device can evenly share the load current, which may lead to inconsistent output currents between devices. In extreme cases, the output current of some devices may even be zero.

[0003] The current imbalance of parallel devices will inevitably lead to a series of problems: 1. The current imbalance will cause some devices to bear higher current, which will cause these modules to be subjected to higher current and voltage stress. 2. When the system output power is large, the uneven current distribution may cause a device to reach its maximum output current, which will cause the device to burn out and affect the reliability of the system. 3. During the load switching process, due to the inconsistency between devices, the difference in current distribution may be aggravated, and even cause the system to fail to operate normally.

[0004] The existing current balancing control strategy is mainly centralized control. However, for the parallel SiC active current balancing control system, the master-slave collaborative control system proposed in this patent can improve the robustness of the system so that each device can achieve the same control target.

[0005] In addition, the traditional parallel SiC active current sharing control system mainly focuses on the two-tube parallel current sharing control, while the three-tube parallel current sharing is less mentioned. For the parallel current sharing of two modules, simple passive current sharing control (such as adjustment through resistance or inductance) is usually sufficient and relatively easy to implement. However, when there are three or more modules in parallel, uneven current distribution is more likely to occur, especially when there are differences in the conduction characteristics of the devices. At this time, if passive current sharing is used, complete balance may not be guaranteed. In order to ensure the current sharing effect, a more sophisticated active current sharing control scheme (such as control based on current detection and feedback) is usually required.

[0006] In addition, for the multi-tube parallel current sharing scheme, the single-point failure problem of the master module in the traditional master-slave control cannot be avoided, and the fault tolerance of the system is relatively low. However, the proposed master-slave collaborative control strategy can better solve the single-point failure problem of the master module. Each module measures its own current information through the real-time current detection unit, and shares information with other modules according to the measured current value to adjust its own working state to achieve current sharing.

[0007] In summary, this application proposes an active current sharing strategy based on master-slave collaborative control. Summary of the Invention

[0008] The object of the present invention is to address the problem of how to provide an active current sharing method for master-slave collaborative control of multi-device parallel connection in the background technology, and propose an active current sharing strategy based on master-slave collaborative control.

[0009] The technical solution of the present invention: An active current sharing strategy based on master-slave collaborative control includes:

[0010] SiC device dynamic current sampling unit, which is used to collect the real-time current information of the SiC device during the turn-on transient process, and transmit the current information to the current information conversion unit;

[0011] Dynamic current information conversion unit, which is used to extract the starting value information and current change rate information when the current starts to rise during the device turn-on / off transient of the collected real-time current information of the SiC device, and transmit them to the current information processing and control unit;

[0012] Dynamic current information processing unit, which is used to receive the current starting value and current change rate of multiple SiC devices, perform difference comparison, generate a PWM drive signal according to the deviation value, and transmit the PWM drive signal to the SiC drive circuit;

[0013] Variable gate resistance drive circuit, which is used to change the starting time of the three drive signals and the duty cycle of the auxiliary drive circuit drive signal according to the drive signal instruction transmitted by the dynamic current information processing unit to achieve parallel current sharing.

[0014] Optionally, the SiC device dynamic current sampling unit includes resistor R 1 、resistor R 2 、resistor R 3 、resistor R 4 、resistor R 5 、operational amplifier U 1 、operational amplifier U 2 and capacitor C 1 , where one end of resistor R 1 is connected to the power source electrode of the SiC power device, and resistor R 1The other end is connected to capacitor C 1 One end of 1 The other end of capacitor C is connected to the Kelvin source of the SiC power device and grounded. Resistor R 1 The end connected to capacitor C 1 The connected end is connected to one end of resistor R 2 One end of and operational amplifier U 2 The non-inverting input terminal of, resistor R 2 The other end of is connected to the inverting input terminal of operational amplifier U 1 The other end of resistor R 3 One end of is connected to the input terminal of operational amplifier U 1 The other end of resistor R 3 Is connected to one end of resistor R 2 One end of resistor R 3 The other end is also connected to the output terminal of operational amplifier U 1 The output terminal of operational amplifier U 1 The non-inverting input terminal of is grounded. The inverting input terminal of operational amplifier U 2 Is connected to one end of resistor R 4 One end of and resistor R 3 One end of resistor R 4 The other end is grounded. The other end of resistor R 5 One end of is connected to the output terminal of operational amplifier U 2 The other end of resistor R 5 Is connected to the other end of resistor R 3 The other end.

[0015] Optionally, the dynamic current sampling unit passes through the passive integration circuit built by R 1 And C 1 Builds a passive integration circuit to represent the dynamic current information in the form of voltage. And after the processing of the passive integration circuit, the voltage Vin is linearly related to the SiC device conduction current. The mathematical expression is as follows:

[0016]

[0017] Through operational amplifier U 1 And operational amplifier U 2 Converts the voltage values during the SiC device turn-on / off process into positive values. Operational amplifier U 1 Is responsible for processing the dynamic current signal during the turn-on process of the SiC power device. Operational amplifier U 2 Is responsible for processing the dynamic current signal during the turn-off process of the SiC power device.

[0018] Optionally, the dynamic current information conversion unit includes a first high-speed comparator, a second high-speed comparator, a third high-speed comparator, and a fourth high-speed comparator. The inverting inputs of the first high-speed comparator and the second high-speed comparator are connected together and connected to Vs_n. The non-inverting input of the first high-speed comparator is connected to a reference voltage Vref1, and the non-inverting input of the second high-speed comparator is connected to a reference voltage Vref2. The inverting inputs of the third high-speed comparator and the fourth high-speed comparator are connected together and connected to Vs_p. The non-inverting input of the third high-speed comparator is connected to a reference voltage Vref3, and the non-inverting input of the fourth high-speed comparator is connected to a reference voltage Vref4. The output terminals of the first high-speed comparator, the second high-speed comparator, the third high-speed comparator, and the fourth high-speed comparator are respectively marked as Vcp1, Vcp2, Vcp3, and Vcp4.

[0019] Optionally, during the turn-on process, the dynamic current information processing unit obtains matrices D1 and D2 by collecting dynamic current, and then determines the intermediate value by comparing the numerical magnitudes of the two. The SiC device corresponding to the intermediate value is used as the control group, and the rest are the experimental groups. The deviation value is calculated and the PWM wave of the drive circuit is adjusted; during the turn-off process, the deviation value is calculated and the PWM wave is adjusted in a similar manner.

[0020] Optionally, for the adjustment of the turn-on delay, according to matrix D1, if cnt on-delay-1 <cnt on-delay-2 , cnt on-delay-2 <cnt on-delay-3 , then the intermediate value is cnt on-delay-2 , and the device corresponding to the intermediate value is used as the control group, and the control group does not adjust the dynamic current;

[0021] The difference is taken between the turn-on delay time of the device corresponding to the experimental group and the turn-on delay time of the device corresponding to the control group;

[0022] The deviation value Δcnt on-delay-1 = cnt on-delay-1 -cnt on-delay-2 and

[0023] Δcnt on-delay-3 = cnt on-delay-3 -cnt on-delay-2 is obtained. Then, according to the positive or negative of the deviation value, the sequence of turn-on delay between the experimental group and the control group is judged;

[0024] If Δcnt on-delay-1 = cnt on-delay-1 -cnt on-delay-2 <0, then

[0025] T S1_current = T S1_last +Δcnt on-delay-1 *Tworking；

[0026] If Δcnt on-delay-1 = cnt on-delay-1 - cnt on-delay-2 > 0, then

[0027] T S1_current = T S1_last - Δcnt on-delay-1 * T working；

[0028] Furthermore, the purpose of having the same starting time for the dynamic current is achieved.

[0029] Optionally, for the adjustment of the current change rate, according to matrix D2, if cnt on-slope-1 < cnt on-slope-2 , cnt on-slope-2 < cnt on-slope-3 , then the intermediate value is cnt on-slope-2 ; Using the device corresponding to the intermediate value as the control group, no dynamic current adjustment is performed on the control group; The difference is taken between the turn-on current change rate of the device corresponding to the experimental group and the turn-on current change rate of the device corresponding to the control group;

[0030] The deviation value Δcnt on-slope-1 = cnt on-slope-1 - cnt on-slope-2 and

[0031] Δcnt on-slope-3 = cnt on-slope-3 - cnt on-slope-2 are obtained, and then, based on the positive or negative of the deviation value, it is judged whether the current change rate of the experimental group is faster or slower than that of the control group;

[0032] If Δcnt on-slope-1 = cnt on-slope-1 - cnt on-slope-2 < 0, then

[0033] T S3_1_current = T S3_1_last - T working；

[0034] If Δcnt on-slope-1 = cnt on-slope-1 - cnt on-slope-2 > 0, then

[0035] T S3_1_current = T S3_1_last + T working；

[0036] Furthermore, the purpose of having the same current change rate for the dynamic current is achieved. The rest is the same for AGD, and the turn-off process is the same.

[0037] The mathematical expression is as follows:

[0038] Δcnt on / off-delay = cnt on / off-delay-slave - cnt on / off-delay-master；

[0039] Δcnt on / off-slope = cnt on / off-slope-slave - cnt on / off-slope-master .

[0040] Optionally, the variable gate resistance driving circuit includes a main driving circuit Q1, an auxiliary driving circuit Q2, and an auxiliary driving circuit Q3. The on-resistance of the main driving circuit Q1 is Ron, and the off-resistance is Roff, which is connected to the gate of the SiC device. The output terminal of the auxiliary driving circuit Q2 is connected to the gate of the NMOS. The drain of the connected NMOS is connected to the external power supply VDD, and the source is connected to the auxiliary on-resistance Ron_aux. The other end of the auxiliary on-resistance Ron_aux is connected to the gate of the SiC device. The output terminal of the auxiliary driving circuit Q3 is connected to the gate of the NOMS. The source of the connected NOMS is connected to the external power supply VEE, and the drain is connected to the auxiliary off-resistance Roff_aux. The other end of the auxiliary off-resistance Roff_aux is connected to the gate of the SiC device.

[0041] Optionally, the main driving circuit Q1 controls the on and off of the SiC device. The PWM wave of the auxiliary driving circuit Q2 is synchronized with the rising edge of the PWM wave of the main driving circuit Q1. At this time, the on-resistance of the SiC device is Ron / / Ron_aux. When the auxiliary driving circuit Q2 is turned off, the on-resistance of the SiC device is Ron. When the on-resistance is Ron / / Ron_aux, the on-resistance of the SiC device is smaller, and the current change rate is faster. When the on-resistance is Ron, the on-resistance of the SiC device is larger, and the current change rate is slower. The rising edge of the auxiliary driving circuit Q3 is synchronized with the falling edge of the main driving circuit Q1. At this time, Q1 is turned off, and the NMOS corresponding to Q3 is turned on. At this time, the off-resistance of the SiC device is Roff / / Roff_aux. When the auxiliary driving circuit Q3 is turned off, the off-resistance of the SiC device is Roff. When the off-resistance is Roff / / Roff_aux, the off-resistance of the SiC device is smaller, and the current change rate is faster. When the off-resistance is Roff, the off-resistance of the SiC device is larger, and the current change rate is slower.

[0042] Compared with the prior art, the present application includes at least one of the following beneficial technical effects:

[0043] It can effectively solve the problem of current imbalance caused by parameter differences in multi-device parallel connection, especially suitable for parallel connection of three or more transistors. The equal current sharing effect is ensured through fine active equal current sharing control.

[0044] The master-slave collaborative control strategy is adopted to solve the single-point failure problem of the master module in traditional master-slave control, improve the system robustness, avoid damage caused by excessive current and voltage stress on devices due to current imbalance, and ensure the stable operation of the system.

[0045] During the load switching process, the current distribution can be effectively adjusted to ensure the stable operation of the system. Brief Description of the Drawings

[0046] Figure 1 It is the hardware structure diagram of the active current sharing scheme provided by the embodiment of the present invention;

[0047] Figure 2 It is the waveform diagram of the turn-on / turn-off process of the active current sharing scheme provided by the embodiment of the present invention;

[0048] Figure 3 It is the logic flow chart of the control strategy of the active current sharing scheme provided by the embodiment of the present invention;

[0049] Figure 4 It is an equivalent circuit diagram of a dynamic current sampling unit provided by the embodiment of the present invention;

[0050] Figure 5 It is an equivalent circuit diagram of a dynamic current information conversion unit provided by the embodiment of the present invention;

[0051] Figure 6 It is an equivalent circuit diagram based on gate variable resistance drive provided by the embodiment of the present invention;

[0052] Figure 7 It is the waveform diagram of the dynamic current sampling unit and the dynamic current information conversion unit provided by the embodiment of the present invention. Detailed Embodiments

[0053] The technical solutions of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0054] Embodiment

[0055] The present invention discloses an active current sharing strategy for master-slave collaborative control. Among them, the schematic diagram of the circuit hardware structure relied on is as Figure 1 shown, which is a silicon carbide metal-oxide-semiconductor field effect transistor (SiC MOSFET) power module, including: a dynamic current sampling unit, a dynamic current information conversion unit, a dynamic current information processing unit, and a variable gate resistance drive circuit; among them,

[0056] (1) The dynamic current sampling unit is used to collect the real-time current information of the SiC device during the on / off transient process and transmit its respective current information to the current information conversion unit.

[0057] Specifically, as Figure 4 shown, the dynamic current sampling unit includes resistor R 1 , resistor R 2 , resistor R 3 , resistor R 4 , resistor R 5 , operational amplifier U 1 (above), operational amplifier U 2 (below), capacitor C 1 ; where one end of resistor R 1 is connected to the power source electrode of the SiC power device, and the other end of resistor R 1 is connected to one end of capacitor C 1 ; the other end of capacitor C 1 is connected to the Kelvin source electrode of the SiC power device and grounded; the end of resistor R 1 connected to capacitor C 1 is connected to one end of resistor R 2 and the non-inverting input terminal of operational amplifier U 2 ; the other end of resistor R 2 is connected to the inverting input terminal of operational amplifier U 1 and is connected to one end of resistor R 3 ; the other end of resistor R 3 is connected to the output terminal of operational amplifier U 1 ; the non-inverting input terminal of operational amplifier U 1 is grounded; the inverting input terminal of operational amplifier U 2 is connected to one end of resistor R 4 and one end of resistor R 5 ; the other end of R 4 is grounded; the other end of R 5 is connected to the output terminal of operational amplifier U 2 . Among them, the connection terminal of resistor R 1 and capacitor C 1 is marked as V in , the output terminal of operational amplifier U1 is denoted as V s_n , and the output terminal of operational amplifier U2 is denoted as V s_p .

[0058] In this embodiment, the dynamic current sampling unit uses a passive integration circuit built by R 1 and C 1 to represent the dynamic current information in the form of voltage. After being processed by the passive integration circuit, voltage V in has a linear relationship with the conduction current of the SiC device, and the mathematical expression is as follows:

[0059]

[0060] Through operational amplifier U 1 and operational amplifier U 2 Convert the voltage values during the turn-on / turn-off process of the SiC device into positive values, which is convenient for the subsequent dynamic current information conversion unit to process the dynamic current information. Among them, operational amplifier U 1 is responsible for processing the dynamic current signal during the turn-on process of the SiC power device, and operational amplifier U 2 is responsible for processing the dynamic current signal during the turn-off process of the SiC power device.

[0061] (2) The dynamic current information conversion unit is used to extract the real-time current information of the SiC device collected, extract the starting value information when the current starts to rise during the turn-on / turn-off transient of the device, and the current change rate information during the turn-on / turn-off transient of the device, and transmit the starting value information of the current and the current change rate information to the current information processing and control unit.

[0062] Specifically, as Figure 5 shown, the dynamic current information conversion unit includes a high-speed comparator one, a high-speed comparator two, a high-speed comparator three, and a high-speed comparator four. The inverting inputs of the high-speed comparator one and the high-speed comparator two are connected together and connected to V s_n ; the non-inverting input of the high-speed comparator one is connected to the reference voltage V ref1 ; the non-inverting input of the high-speed comparator two is connected to the reference voltage V ref2 ; the inverting inputs of the high-speed comparator three and the high-speed comparator four are connected together and connected to V s_p ; the non-inverting input of the high-speed comparator three is connected to the reference voltage V ref3 ; the non-inverting input of the high-speed comparator four is connected to the reference voltage V ref4 ; the outputs of the high-speed comparator one, the high-speed comparator two, the high-speed comparator three, and the high-speed comparator four are respectively marked as V cp1 , V cp2 , V cp3 , V cp4 .

[0063] In this embodiment (as Figure 7 shown), taking the turn-on process as an example, the dynamic current information conversion unit sets the reference voltage V ref1 through the high-speed comparator one and compares it with the inverting input V s_n . Among them, V ref1 is set to a voltage close to 0. When V cp1 = 1, it indicates that the current starts to turn on; the high-speed comparator two sets the reference voltage V ref2 and compares it with the inverting input V s_n . Among them, V ref2 is set to a voltage level greater than 0 through manual debugging. When Vcp2 = 1, then V cp1 = 1 to V cp2 = 1 during this period represents the current change rate. The turn-off process is the same.

[0064] (3) The dynamic current information processing unit receives the starting current values and current change rates of the No. 1 SiC device, No. 2 SiC device, and No. 3 SiC device, and performs subtraction and comparison. According to the magnitude of the deviation value, corresponding PWM drive signals are generated and the corresponding PWM drive signals are transmitted to the SiC drive circuit, thereby achieving the purpose of parallel current sharing.

[0065] Specifically, the dynamic current information obtained by each power device through its respective dynamic current sampling unit and dynamic current information conversion unit is transmitted to the dynamic current information processing unit. The dynamic current information processing unit determines whether each SiC device is used as the main AGD. The SiC device corresponding to the main AGD does not adjust the dynamic current, while the remaining slave AGDs perform the processing of the dynamic current information.

[0066] In this embodiment, during the turn-on process: The control system obtains the matrix D1 = [cnt on-delay-1 ; cnt on-delay-2 ; cnt on-delay-3 and D2 = [cnt on-slope-1 ; cnt on-slope-2 ; cnt on-slope-3 by collecting the dynamic current information of the three, and then determines the intermediate value by comparing the magnitudes of the three values. Taking the intermediate value as the control group and the others as the experimental groups, the deviation value is calculated, and based on the obtained deviation value, the PWM wave of the drive circuit is adjusted.

[0067] For example, for the adjustment of the turn-on delay, according to the matrix D1, if cnt on-delay-1 < cnt on-delay-2 , cnt on-delay-2 < cnt on-delay-3 , then the intermediate value is cnt on-delay-2 . Taking the device corresponding to the intermediate value as the control group (the No. 2 power device), the control group does not adjust the dynamic current. The turn-on delay times (cnt on-delay-1 , cnt on-delay-3 ) of the devices corresponding to the experimental groups are subtracted from the turn-on delay time

[0068] (cnt on-delay-2 ) of the device corresponding to the control group.

[0069] The deviation values Δcnt on-delay-1 = cnt on-delay-1 - cnt on-delay-2 and Δcnton-delay-3 = cnt on-delay-3 -cnt on-delay-2 , then, according to the positive or negative of the deviation value, judge the sequence of turn-on delays between the experimental group and the control group.

[0070] If Δcnt on-delay-1 = cnt on-delay-1 -cnt on-delay-2 < 0, then

[0071] T S1_current = T S1_last +Δcnt on-delay-1 *T working；

[0072] If Δcnt on-delay-1 = cnt on-delay-1 -cnt on-delay-2 > 0, then

[0073] T S1_current = T S1_last -Δcnt on-delay-1 *T working；

[0074] Furthermore, the purpose of having the same starting time for the dynamic current is achieved.

[0075] For the regulation of the current change rate, according to matrix D2, if cnt on-slope-1 < cnt on-slope-2 , cnt on-slope-2 < cnt on-slope-3 , then the intermediate value is cnt on-slope-2 . Use the device corresponding to the intermediate value as the control group (Power Device No. 2), and no dynamic current regulation is performed on the control group. Subtract the turn-on current change rates (cnt on-slope-1 , cnt on-slope-3 ) of the devices corresponding to the experimental group from the turn-on current change rate (cnt on-slope-2 ) of the device corresponding to the control group. Obtain the deviation value Δcnt on-slope-1 = cnt on-slope-1 -cnt on-slope-2 and Δcnt on-slope-3 =

[0076] cnt on-slope-3 -cnt on-slope-2 , then, according to the positive or negative of the deviation value, judge the speed of the current change rates between the experimental group and the control group.

[0077] If Δcnt on-slope-1 = cnt on-slope-1 -cnt on-slope-2 < 0, then

[0078] TS3_1_current = T S3_1_last -T working；

[0079] If Δcnt on-slope-1 = cnt on-slope-1 -cnt on-slope-2 > 0, then

[0080] T S3_1_current = T S3_1_last + T working；

[0081] Furthermore, the purpose of having the same current change rate for the dynamic current is achieved.

[0082] For the rest, it is the same with AGD, and the turn-off process is the same.

[0083] The mathematical expression is as follows:

[0084] Δcnt on / off-delay = cnt on / off-delay-slave -cnt on / off-delay-master；

[0085] Δcnt on / off-slope = cnt on / off-slope-slave -cnt on / off-slope-master；

[0086] (4) The variable gate resistance drive circuit changes the start time of the three drive signals and the duty cycle of the drive signal of the auxiliary drive circuit through the drive signal instructions transmitted by the dynamic current information processing unit, so as to achieve the purpose of parallel current sharing.

[0087] Specifically, as Figure 6 shown, for each power device, the three EPWM interfaces of the dynamic current information processing unit are respectively connected to the main drive circuit Q1, the auxiliary drive circuit Q2, and the auxiliary drive circuit Q3. The on-resistance of the main drive circuit is R on , the off-resistance R off , which are connected to the gate of the SiC device; the output end of the auxiliary drive circuit Q2 is connected to the gate of the NMOS, the drain of the connected NMOS is connected to the external power supply V DD , the source is connected to the auxiliary on-resistance R on_aux , and the other end of this resistor is connected to the gate of the SiC device; the output end of the auxiliary drive circuit Q3 is connected to the gate of the NMOS, the source of the connected NMOS is connected to the external power supply V EE , the drain is connected to the auxiliary on-resistance R off_aux , and the other end of this resistor is connected to the gate of the SiC device.

[0088] In this embodiment, the main drive circuit Q1 controls the on and off of the SiC device. The PWM wave of the auxiliary drive circuit Q2 is synchronized with the rising edge of the PWM wave of the main drive circuit Q1. At this time, the on-resistance of the SiC device is R on / / R on_aux , when the auxiliary drive circuit Q2 is turned off, the on-resistance of the SiC device is R on . When the on-resistance is R on / / R on_aux , the on-resistance of the SiC device is small and the current change rate is fast; when the on-resistance is R on , the on-resistance of the SiC device is large and the current change rate is slow. The rising edge of the auxiliary drive circuit Q3 is synchronized with the falling edge of the main drive circuit Q1. At this time, Q1 is turned off and the NMOS corresponding to Q3 is turned on. At this time, the off-resistance of the SiC device is R off / / R off_aux , when the auxiliary drive circuit Q3 is turned off, the off-resistance of the SiC device is R off . When the off-resistance is R off / / R off_aux , the off-resistance of the SiC device is small and the current change rate is fast; when the off-resistance is R off , the off-resistance of the SiC device is large and the current change rate is slow. Therefore, the purpose of adjusting the current change rate is achieved. For the adjustment of the turn-on / turn-off delay, it is realized by advancing or delaying the rising edge and falling edge of the PWM wave of the main drive circuit Q1 to make the start values of the turn-on / turn-off currents of the modules consistent. off

[0089] In this embodiment, as shown in Figure 2 , Figure 2 is the waveform diagram of the turn-on / turn-off process.

[0090] Among them, the turn-on process: S1 is the adjustment stage of the turn-on delay. At the initial stage of this stage, the S of the three devices 1 stage is set to the same time. The mentioned ΔT on-delay is adjusted within this time period. By adjusting the S 1 time, the purpose of making the starting times of the currents between the power devices consistent is achieved.

[0091] S 3 stage is the current change rate adjustment stage. The adjustment of the current change rate is obtained by the vector synthesis principle of the current change rates in the S 3-1 stage and the S 3-2 stage to get an overall current change rate. And the S 3 stage is further divided into two small stages, namely the S 3-1 stage and the S 3-2 ​Phase. Among them, S 3-1 The driving circuit corresponding to the phase ( Figure 6 ) The working state is that the main driving circuit Q1 works and the auxiliary driving circuit Q2 works. S 3-2 The working state of the driving circuit corresponding to the phase is that the main driving circuit Q1 works alone. The mentioned Δd i / dt is adjusted within this time period, and by adjusting the working time of the auxiliary driving circuit Q2, the purpose of making the current change rates between power devices consistent is achieved.

[0092] Turn-off process: S 6 Is the adjustment stage of turn-off delay. At the beginning of this stage, the S of the three devices 6 The phase is set to the same time. The ΔT of the turn-off process off-delay Is adjusted within this time period, and by adjusting the S 6 Time, the purpose of making the starting time of the current between power devices consistent is achieved.

[0093] S 9 The phase is the current change rate adjustment stage. The adjustment of the current change rate is achieved by the S 9-1 Phase and S 9-2 The current change rates of the phases are synthesized vectorially to obtain an overall current change rate. And the S 3 The phase is further divided into two small phases, namely S 9-1 Phase and S 9-2 Phase. Among them, S 9-1 The driving circuit corresponding to the phase ( Figure 6 ) The working state is that the main driving circuit Q1 works and the auxiliary driving circuit Q3 works. S 9-2 The working state of the driving circuit corresponding to the phase is that the main driving circuit Q1 works alone. The mentioned Δd i / dt is adjusted within this time period, and by adjusting the working time of the auxiliary driving circuit Q3, the purpose of making the current change rates between power devices consistent is achieved.

[0094] An active current sharing strategy with master-slave collaborative control disclosed by the present invention (as Figure 3 shown). Combining the above analysis, when the rising edge of the PWM wave of the main driving circuit Q1 corresponding to each SiC device arrives, the dynamic current information processing unit starts to count cnt on-delay and cnt on-slope (as Figure 7 shown), and at this time, it is judged whether the output values Vcp1, Vcp2, Vcp3, Vcp4 of the dynamic current information conversion unit are timed out. If not timed out, the count values of the three SiC devices are uploaded to obtain the turn-on current delay matrix D1 = [cnt on-delay-1 ; cnt on-delay-2 ; cnt on-delay-3; The matrix D2 of the turn-on current change rate = [cnt on-slope-1 ; cnt on-slope-2 ; cnt on-slope-3 ; The matrix D3 of the turn-off current delay = [cnt off-delay-1 ; cnt off-delay-2 ; cnt off-delay-3 ; The matrix D4 of the turn-off current change rate = [cnt off-slope-1 ; cnt off-slope-2 ; cnt off-slope-3 . Taking the turn-on process as an example, the intermediate value is obtained by comparison, and the SiC device corresponding to the intermediate value is used as the main AGD, and the other two paths are the slave AGDs. During the current pulse stage, the main AGD does not adjust the turn-on delay and current change rate of the corresponding SiC device. The slave AGD adjusts the S 1 stage and the S 3-1 stage (as shown in Figure 2 ). The turn-off process is the same, and the S 6 stage and the S 9-1 stage are adjusted (as shown in Figure 2 ).

[0095] As can be seen from the above analysis, the embodiment of the present invention provides a master-slave cooperative control active current sharing strategy, which can be used for the dynamic current sharing of three or more parallel SiC devices. The master-slave cooperative control active current sharing strategy has the following advantages:

[0096] 1. An active current sharing strategy is adopted. Compared with the traditional current sharing control for two-device parallel connection, simple passive current sharing control (such as adjusting through resistors or inductors) is usually sufficient and relatively easy to implement. However, when three modules are connected in parallel, uneven current distribution is more likely to occur, especially when there are differences in the conduction characteristics of the devices. In this case, if passive current sharing is used, it may not be possible to ensure complete balance.

[0097] 2. The proposed master-slave cooperative control strategy can further improve the robustness of the system and greatly improve the reliability of the system compared with the traditional master-slave control strategy, in which the entire system cannot work properly once the main module fails.

[0098] The above specific embodiments are only several alternative embodiments of the present invention. Based on the technical solution of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. An active current sharing strategy for master-slave collaborative control, characterized in that: include: SiC device dynamic current sampling unit, used to collect real-time current information of SiC device during the transient process of opening, and transmit the current information to the current information conversion unit; A dynamic current information conversion unit is used to extract the initial value information and current change rate information of the current when the device is turned on / off transiently from the collected real-time current information of the SiC device, and transmit it to the current information processing control unit; A dynamic current information processing unit, used to receive the current starting values ​​and current change rates of multiple SiC devices, perform difference comparison, generate a PWM drive signal according to the deviation value, and transmit the PWM drive signal to the SiC drive circuit; The variable gate resistance driving circuit is used to change the starting time of the three-way driving signal and the duty cycle of the auxiliary driving circuit driving signal according to the driving signal instruction transmitted by the dynamic current information processing unit to achieve parallel current sharing.

2. The active current sharing strategy of master-slave collaborative control according to claim 1 is characterized in that: The SiC device dynamic current sampling unit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, an operational amplifier U1, an operational amplifier U2 and a capacitor C1, wherein one end of the resistor R1 is connected to the power source of the SiC power device, the other end of the resistor R1 is connected to one end of the capacitor C1, the other end of the capacitor C1 is connected to the Kelvin source of the SiC power device and grounded, one end of the resistor R1 connected to the capacitor C1 is connected to one end of the resistor R2 and the in-phase input end of the operational amplifier U2, the other end of the resistor R2 is connected to the inverting input end of the operational amplifier U1, one end of the resistor R3 is connected to the input end of the operational amplifier U1, the other end of the resistor R3 is connected to one end of the resistor R2, the other end of the resistor R3 is also connected to the output end of the operational amplifier U1, the in-phase input end of the operational amplifier U1 is grounded, the inverting input end of the operational amplifier U2 is connected to one end of the resistor R4 and one end of the resistor R3, the other end of the resistor R4 is grounded, one end of the resistor R5 is connected to the output end of the operational amplifier U2, and the other end of the resistor R5 is connected to the other end of the resistor R3.

3. The active current sharing strategy of master-slave collaborative control according to claim 2 is characterized in that: The dynamic current sampling unit uses a passive integration circuit constructed by R1 and C1 to express the dynamic current information in the form of voltage. After being processed by the passive integration circuit, the voltage Vin is linearly related to the on-current of the SiC device. The mathematical expression is as follows: The voltage values ​​of the SiC device turn-on / off process are converted into positive values ​​through operational amplifier U1 and operational amplifier U2. Operational amplifier U1 is responsible for processing the dynamic current signal of the SiC power device turn-on process, and operational amplifier U2 is responsible for processing the dynamic current signal of the SiC power device turn-off process.

4. The active current sharing strategy of master-slave collaborative control according to claim 1, characterized in that: The dynamic current information conversion unit includes a high-speed comparator 1, a high-speed comparator 2, a high-speed comparator 3, and a high-speed comparator 4. The inverting input terminals of the high-speed comparator 1 and the high-speed comparator 2 are connected and connected to Vs_n, the non-inverting input terminal of the high-speed comparator 1 is connected to the reference voltage Vref1, the non-inverting input terminal of the high-speed comparator 2 is connected to the reference voltage Vref2, the inverting input terminals of the high-speed comparator 3 and the high-speed comparator 4 are connected and connected to Vs_p, the non-inverting input terminal of the high-speed comparator 3 is connected to the reference voltage Vref3, and the non-inverting input terminal of the high-speed comparator 4 is connected to the reference voltage Vref4. The output terminals of the high-speed comparator 1, the high-speed comparator 2, the high-speed comparator 3, and the high-speed comparator 4 are marked as Vcp1, Vcp2, Vcp3, and Vcp4, respectively.

5. The active current sharing strategy of master-slave collaborative control according to claim 1, characterized in that: During the opening process, the dynamic current information processing unit obtains matrix D1 and matrix D2 by collecting dynamic current, and then confirms the intermediate value by comparing the numerical values ​​of the two. The SiC device corresponding to the intermediate value is used as the control group, and the rest are the experimental group. The deviation value is calculated and the PWM wave of the driving circuit is adjusted; during the closing process, the deviation value calculation and PWM wave adjustment are also performed by a similar method.

6. The active current sharing strategy of master-slave collaborative control according to claim 5, characterized in that: For the adjustment of the opening delay, according to the matrix D1, if cnt on-delay-1 <cnt on-delay-2 ,cnt on-delay-2 <cnt on-delay-3 , then the middle value is cnt on-delay-2 , the device corresponding to the middle value is used as the control group, and the control group does not adjust the dynamic current; The difference between the turn-on delay time of the corresponding device in the experimental group and the turn-on delay time of the corresponding device in the control group is calculated; Get the deviation value Δcnt on-delay-1 =cnt on-delay-1 -cnt on-delay-2 and Δcnt on-delay-3 =cnt on-delay-3 -cnt on-delay-2 ,Then, based on the positive and negative values ​​of the deviation, the order of opening the delay between the experimental group and the control group is determined; If Δcnt on-delay-1 =cnt on-delay-1 -cnt on-delay-2 <0, then T S1_current =T S1_last +Δcnt on-delay-1 *T working； If Δcnt on-delay-1 =cnt on-delay-1 -cnt on-delay-2 >0, then T S1_current =T S1_last -Δcnt on-delay-1 *T working； This achieves the goal of ensuring that the dynamic current has the same starting time.

7. The active current sharing strategy of master-slave collaborative control according to claim 6, characterized in that: For the regulation of the current change rate, according to matrix D2, if cnt on-slope-1 <cnt on-slope-2 ,cnt on-slope-2 <cnt on-slope-3 , then the middle value is cnt on-slope-2 ; The device corresponding to the middle value is used as the control group, and the control group does not adjust the dynamic current; the turn-on current change rate of the device corresponding to the experimental group is subtracted from the turn-on current change rate of the device corresponding to the control group; Get the deviation value Δcnt on-slope-1 =cnt on-slope-1 -cnt on-slope-2 and Δcnt on-slope-3 =cnt on-slope-3 -cnt on-slope-2 Then, according to the positive or negative value of the deviation, the speed of the current change rate of the experimental group and the control group is judged; If Δcnt on-slope-1 =cnt on-slope-1 -cnt on-slope-2 <0, then T S3_1_current =T S3_1_last -T working； If Δcnt on-slope-1 =cnt on-slope-1 -cnt on-slope-2 >0, then T S3_1_current =T S3_1_last +T working； Then the purpose of dynamic current having the same current change rate is achieved. The rest is the same from AGD and the shutdown process is the same. The mathematical expression is as follows: Δcnt on / off-delay =cnt on / off-delay-slave -cnt on / off-delay-master 4 Δcnt on / off-slope =cnt on / off-slope-slave -cnt on / off-slope-master 。 8. The active current sharing strategy of master-slave collaborative control according to claim 1, characterized in that: The variable gate resistance drive circuit includes a main drive circuit Q1, an auxiliary drive circuit Q2 and an auxiliary drive circuit Q3. The main drive circuit Q1 has an on-resistance of Ron and an off-resistance of Roff, and is connected to the gate of the SiC device. The output end of the auxiliary drive circuit Q2 is connected to the gate of the NMOS, the drain of the connected NMOS is connected to the external power supply VDD, the source is connected to the auxiliary on-resistance Ron_aux, and the other end of the auxiliary on-resistance Ron_aux is connected to the gate of the SiC device. The output end of the auxiliary drive circuit Q3 is connected to the gate of the NOMS, the source of the connected NOMS is connected to the external power supply VEE, the drain is connected to the auxiliary on-resistance Roff_aux, and the other end of the auxiliary on-resistance Roff_aux is connected to the gate of the SiC device.

9. The active current sharing strategy of master-slave collaborative control according to claim 8, characterized in that: The main drive circuit Q1 controls the on and off of the SiC device, and the PWM wave of the auxiliary drive circuit Q2 is synchronized with the rising edge of the PWM wave of the main drive circuit Q1. At this time, the on-resistance of the SiC device is Ron / / Ron_aux. When the auxiliary drive circuit Q2 is turned off, the on-resistance of the SiC device is Ron. When the on-resistance is Ron / / Ron_aux, the on-resistance of the SiC device is small and the current change rate is fast. When the on-resistance is Ron, the on-resistance of the SiC device is large and the current change rate is fast. slow; the rising edge of the auxiliary drive circuit Q3 is synchronized with the falling edge of the main drive circuit Q1, then Q1 is turned off at this time, and the NMOS corresponding to Q3 is turned on. At this time, the off resistance of the SiC device is Roff / / Roff_aux. When the auxiliary drive circuit Q3 is turned off, the off resistance of the SiC device is Roff; when the off resistance is Roff / / Roff_aux, the off resistance of the SiC device is small, and the current change rate is fast; when the off resistance is Roff, the off resistance of the SiC device is large, and the current change rate is slow.

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