Current sharing control method and ac-DC conversion system

Abstract

A current sharing control method and an AC-DC conversion system. The method is applied to a current sharing controller. The current sharing controller is used for controlling the operating state of an AC-DC converter, the AC-DC converter comprises at least two rectifier units, and each of the at least two rectifier units uses a combination of a bridge topology and an LLC resonant tank. The method comprises: acquiring current sampling values of at least two rectifier units; on the basis of the current sampling values of the at least two rectifier units, determining a target phase shift angle of each rectifier unit, wherein the target phase shift angle is used for indicating the duration during which an input voltage of an LLC resonant tank is in a zero-level state; and on the basis of the target phase shift angle of each rectifier unit, controlling the phase shifting of control signals for target switch transistors in a bridge topology of each rectifier unit. Phase shift angles of switch transistors in rectifier units are adjusted, such that input voltages of LLC resonant tanks are at zero level, so as to control an output current of each rectifier unit, thereby achieving the effect of current sharing among outputs of a plurality of rectifier units.

Description

Current sharing control method and AC-DC conversion system

[0001] The present application claims priority to the Chinese patent application No. 202411323283.3, filed on September 20, 2024, and entitled "Current sharing control method and AC-DC conversion system", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of electric energy conversion, and in particular, to a current sharing control method and an AC-DC conversion system. BACKGROUND

[0003] The conventional AC-DC converter usually adopts a two-stage topology of PFC+DCDC. The front-stage PFC is used to control the input current to achieve high power factor and low total harmonic distortion; and the rear-stage DC-DC converter is used to control the output voltage and current to ensure the stability of the output voltage and current under different working conditions. The two-stage topology requires two-stage switching devices and an intermediate bus capacitor, which limits the optimization of efficiency, power density and cost to a certain extent. On the basis of the two-stage topology, the intermediate bus capacitor is removed, and only a one-stage switching network is needed, which derives a three-phase single-stage topology, has higher efficiency and higher power density, and has a broad application prospect in the fields of communication power supply, electric vehicle charging and other high-power power supplies.

[0004] In the application scenarios of high power and low voltage and large current, the current of the three-phase single-stage topology is large, requiring switching devices with higher current resistance, and the ripple current on the output capacitor is also large, affecting the indicators such as efficiency, heat and reliability. The method of parallel connection of multiple switching devices and parallel connection of multiple output capacitors is usually used to share the current and reduce the current flowing through each switching device and output capacitor.

[0005] In actual applications, devices are non-ideal devices, and device parameters will differ due to process, batch and other reasons, so it is impossible to make the parameters of each component consistent. For example, the inductance and capacitance accuracy of common inductors and capacitors is 5%-10%. The output gain of each rectification unit is greatly affected by the parameters of the resonant tank components, and the difference in gain caused by the difference in component parameters will cause the problem of uneven output current, which further limits the development of the three-phase single-stage topology in the application scenarios of larger power and low voltage and large current. SUMMARY

[0006] The present application provides a current sharing control method and an AC-DC conversion system to solve the technical problem of uneven output current of the converter in the prior art.

[0007] In a first aspect, the present application provides a method for controlling the current sharing of a converter. The method is applied to a current sharing controller, which is configured to control the operation of an AC-DC converter. The AC-DC converter comprises at least two rectifier units, each of which is a combination of a bridge topology and an LLC resonant tank. The method comprises:

[0008] obtaining current sampling values of the at least two rectifier units;

[0009] determining a target phase shift angle of each rectifier unit based on the current sampling values of the at least two rectifier units, wherein the target phase shift angle is indicative of a duration of a period during which the input voltage of the LLC resonant tank is at a 0 voltage level;

[0010] controlling the control signals of target switching tubes in the bridge topology of each rectifier unit to perform phase shifting based on the target phase shift angle of each rectifier unit.

[0011] In one embodiment, the current sampling values include one or more of input current sampling values, rectifier output current sampling values, resonant current sampling values, switching tube current sampling values, and transformer secondary side current sampling values.

[0012] In one embodiment, determining the target phase shift angle of each rectifier unit based on the current sampling values of the at least two rectifier units comprises:

[0013] determining a current error corresponding to each rectifier unit based on the current sampling values of the at least two rectifier units;

[0014] inputting the current error corresponding to each rectifier unit into a preset current sharing loop, performing amplitude limiting on the output of the preset current sharing loop, and obtaining a phase shift angle adjustment amount corresponding to each rectifier unit;

[0015] determining the target phase shift angle of each rectifier unit based on the phase shift angle adjustment amount corresponding to each rectifier unit and an initial value of the phase shift angle.

[0016] In one embodiment, determining the current error corresponding to each rectifier unit based on the current sampling values of the at least two rectifier units comprises:

[0017] comparing the current sampling values of the at least two rectifier units to determine a minimum value among the current sampling values of the at least two rectifier units;

[0018] determining the difference between the current sampling value of each rectifier unit and the minimum value as the current error corresponding to each rectifier unit.

[0019] In one embodiment, determining the current error corresponding to each rectifier unit based on the current sampling values of the at least two rectifier units comprises:

[0020] According to the current sampling values of the at least two rectification units, determine average current values of the at least two rectification units;

[0021] Differences between the current sampling values of each rectification unit and the average current values are taken as corresponding current errors of each rectification unit.

[0022] In one of the embodiments, the limiting range of the limiting amplitude processing corresponding to the output of the phase-shifting angle adjustment amount of each rectification unit is related to the initial value of the phase-shifting angle of each rectification unit.

[0023] In one of the embodiments,

[0024] According to the target phase-shifting angle of each rectification unit, control the control signals of the target switch tubes in the bridge topology structure of each rectification unit to perform phase-shifting, including:

[0025] According to the target phase-shifting angle of each rectification unit, control the control signals of the upper switch tubes of each bridge arm in the bridge topology structure of each rectification unit to perform phase-shifting to the left; or,

[0026] According to the target phase-shifting angle of each rectification unit, control the control signals of the upper switch tubes of each bridge arm in the bridge topology structure of each rectification unit to perform phase-shifting to the right; or,

[0027] According to the target phase-shifting angle of each rectification unit, control the control signals of the lower switch tubes of each bridge arm in the bridge topology structure of each rectification unit to perform phase-shifting to the left; or,

[0028] According to the target phase-shifting angle of each rectification unit, control the control signals of the lower switch tubes of each bridge arm in the bridge topology structure of each rectification unit to perform phase-shifting to the right.

[0029] In a second aspect, the present application provides an AC-DC conversion system, which comprises an AC-DC converter and a current-sharing controller; the AC-DC converter comprises at least two rectification units, and each of the at least two rectification units adopts a combination of a bridge topology structure and an LLC resonant tank;

[0030] The current-sharing controller is used to control the working state of the AC-DC converter, and is specifically used to execute the above method steps.

[0031] In a third aspect, the present application further provides a computer device, which comprises a processor and a memory connected with the processor in communication;

[0032] The memory stores computer execution instructions;

[0033] The processor executes the computer execution instructions stored in the memory to realize the above method.

[0034] In a fourth aspect, the present application provides a computer readable storage medium, wherein the computer readable storage medium stores computer execution instructions, and the computer execution instructions are executed by a processor to implement the method.

[0035] In a fifth aspect, the present application provides a computer program product, comprising computer execution instructions, and the computer execution instructions are executed by a processor to implement the method.

[0036] The present application provides a current sharing control method and an AC-DC conversion system. The method comprises applying to a current sharing controller, the current sharing controller being used to control the working state of an AC-DC converter, the AC-DC converter comprising at least two rectifier units, and each of the at least two rectifier units adopting a combination of a bridge topology and an LLC resonant tank. The method comprises: obtaining current sampling values of the at least two rectifier units; determining a target phase shift angle of each rectifier unit according to the current sampling values of the at least two rectifier units, the target phase shift angle being used to indicate the duration of the input voltage of the LLC resonant tank being at a 0 level state; and controlling the control signal of a target switch tube in the bridge topology of each rectifier unit to be phase shifted according to the target phase shift angle of each rectifier unit. The present application adjusts the phase shift angle of the switch tube in the rectifier unit, so that the input voltage of the LLC resonant tank is at a 0 level, thereby controlling the output current of each rectifier unit, and achieving the effect of the output of the plurality of rectifier units being current shared. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0038] FIG. 1 is a schematic diagram of the current after an LLC rectifier bridge provided in an embodiment;

[0039] FIG. 2 is a schematic diagram of the current ripple cancellation effect of three-phase single-stage two-phase interleaved parallel connection provided in an embodiment;

[0040] FIG. 3 is a flowchart of the current sharing control method provided in an embodiment;

[0041] FIG. 4 is a schematic diagram of a current sampling point provided in an embodiment;

[0042] FIG. 5 is a structural diagram of an AC-DC converter provided in an embodiment;

[0043] FIG. 6 is a control signal waveform diagram of Δθ=0 and θ1=180° provided in an embodiment;

[0044] FIG. 7 is a control signal waveform diagram of Δθ=50° and θ1=130° provided in an embodiment;

[0045] Figure 8 is a comparison chart when the resonant inductance varies by 5% in one embodiment;

[0046] Figure 9 is a comparison chart when the resonant capacitance varies by 5% in one embodiment;

[0047] Figure 10 is a comparison chart when the excitation inductance varies by 5% in one embodiment;

[0048] Figure 11 is a flow chart of the current sharing control method in one embodiment;

[0049] Figure 12 is a block diagram of the current sharing control method in one embodiment;

[0050] Figure 13 is a block diagram of the current sharing control method in one embodiment;

[0051] Figure 14 is a diagram of the left shift of the upper tube in one embodiment;

[0052] Figure 15 is a diagram of the right shift of the upper tube in one embodiment;

[0053] Figure 16 is a diagram of the right shift of the lower tube in one embodiment;

[0054] Figure 17 is a diagram of the structure of the AC-DC conversion system in one embodiment;

[0055] Figure 18 is a diagram of the hardware structure of the computer device in one embodiment.

[0056] The specific embodiments of the present application have been shown by way of example in the above figures, and will be described in more detail hereafter. These figures and written description are not meant to limit the scope of the present application in any way, but merely to illustrate the concepts of the present application to a person skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0057] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The following description is made with reference to the accompanying drawings in which like reference numerals refer to like elements, and by way of example only. The following description is not meant to limit the application to all of the embodiments in which it can be practiced. Rather, the following description is meant to provide example embodiments of the application in accordance with the following claims.

[0058] In the description of the present application, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0059] The conventional AC-DC converter usually adopts a two-stage topology of PFC+DCDC. The front-stage PFC is used to control the input current to achieve high power factor and low total harmonic distortion; the rear-stage DC-DC converter is used to control the output voltage and current to ensure the stability of the output voltage and current under different working conditions. The two-stage topology requires two-stage switching devices and an intermediate bus capacitor, which limits the optimization of efficiency, power density and cost to a certain extent. On the basis of the two-stage topology, the intermediate bus capacitor is removed, only one switching network is needed, and a three-phase single-stage topology is derived, which has higher efficiency and higher power density, and has broad application prospects in the fields of communication power supply, electric vehicle charging and other high-power power supplies.

[0060] In high-power and low-voltage high-current application scenarios, the current of the three-phase single-stage topology is large, requiring higher current-resistant switching devices, and the ripple current on the output capacitor is also large, affecting its efficiency, heat and reliability indicators. Usually, multiple switching devices in parallel and multiple output capacitors in parallel are used to divide the current and reduce the current flowing through each switching device and output capacitor. For example, the switching tube is changed from 1 to 2 in parallel, and theoretically the current flowing through each switching tube is reduced by half, and the conduction loss of the switching tube is also reduced by half.

[0061] As the three-phase single-stage topology has only one rectifier unit, the input is 380V, 50HZ, the output is 270V, 50KW, and the output electrolytic capacitor has a capacity of 5640uF, the current ripple after the LLC rectifier bridge is very large, with a peak-to-peak value of 425.9A, as shown in FIG. 1. The ripple current on the output electrolytic capacitor is similar to a half-wave sine wave. The effective value of the ripple current of the output electrolytic capacitor from 0.02s to 0.18s is calculated to be 83.32A. The rated ripple current of the electrolytic capacitor is usually a few amperes. Taking an electrolytic capacitor with a rated ripple current effective value of 2A as an example, at least 42 electrolytic capacitors are needed in parallel without considering the derating. Too many electrolytic capacitors are not conducive to improving the power density of the three-phase single-stage.

[0062] Generally, the method of multiple rectifier units staggered parallel is adopted, the switching tube of the rectifier bridge unit is staggered by an angle, such as 90 degrees for two-phase staggered parallel, 120 degrees for three-phase staggered parallel, the output current of the rectifier unit is staggered to produce ripple cancellation effect, so as to reduce the output current ripple of the rectifier unit, and further reduce the current ripple on the output electrolytic capacitor. As shown in FIG. 2, the current ripple cancellation effect of the output currents of the rectifier units U1 and U2 in the three-phase single-stage two-phase staggered parallel converter.

[0063] Under the same working condition, when the input is 380V, 50HZ, the output is 270V, 50KW, and the output electrolytic capacitor capacity is 5640uF, the ripple current of the output electrolytic capacitor is calculated from 0.02s to 0.18s, and the effective value is 27.2A. Taking the electrolytic capacitor with a rated ripple current effective value of 2A as an example, only 14 electrolytic capacitors are needed in parallel without considering the derating, which is 28 less than the 42 needed without staggering parallel, the number of electrolytic capacitors is greatly reduced, which is conducive to the improvement of the three-phase single-stage power density.

[0064] The output gain of each rectifier unit is greatly affected by the parameters of the resonant tank components, such as the difference in resonant inductance, the difference in resonant capacitance, and the difference in excitation inductance, which will affect the gain of LLC. When the firing frequency, duty cycle and phase of each rectifier unit are the same, the output current will be uneven due to the difference in gain. When the uneven flow exceeds a certain limit, the heat distribution of each rectifier unit will be uneven, and in severe cases, the rectifier unit with large current will overcurrent, which will damage the switching tube and affect the reliability of the switching tube.

[0065] In actual application, the devices are non-ideal devices, and the parameters of the devices will differ due to process, batch, etc. It is impossible to make the parameters of each component consistent, such as the common inductance and capacitance precision of 5%-10%. The uneven flow problem of the staggered parallel three-phase single-stage topology caused by the difference in device parameters further limits the development of the three-phase single-stage topology in larger power and low-voltage high-current application scenarios.

[0066] The embodiment of the present application provides a current sharing control method applied to a current sharing controller, the current sharing controller is used for controlling the working state of an AC-DC converter, the AC-DC converter comprises at least two rectifier units, and the at least two rectifier units all adopt a combination of a bridge topology structure and an LLC resonant tank; as shown in FIG. 3, the method comprises the following steps:

[0067] Step 302, acquiring current sampling values of the at least two rectifier units;

[0068] Step 304, according to the current sampling value of at least two rectifier units, determine the target phase shift angle of each rectifier unit, the target phase shift angle is used to indicate the duration of the input voltage of LLC resonant tank being 0 level state;

[0069] Step 306, according to the target phase shift angle of each rectifier unit, control the control signal of the target switch tube in the bridge topology structure of each rectifier unit to phase shift.

[0070] Wherein, the current sampling value of the rectifier unit refers to the current in the rectifier unit circuit, and the current sampling value is obtained by sampling the current or voltage in the circuit. The sampling point and sampling time of the current sampling value of at least two rectifier units need to be consistent, so as to judge the current size of at least two rectifier units at the same time and the same position.

[0071] According to the difference of the sampling point of the current sampling value, when directly collecting the current in the circuit, the current sampling value can include one or more of input current sampling value (such as collecting at point A in figure 4), rectified output current sampling value (such as collecting at point B in figure 4), resonant current sampling value (such as collecting at point C in figure 4), switch tube current sampling value (such as collecting at points D1-D6 in figure 4) and transformer secondary side current sampling value (such as collecting at point E in figure 4). Directly sampling the current at each point of the circuit can quickly obtain the current sampling value.

[0072] When the current sampling value is indirectly determined by collecting the voltage in the circuit, as shown in figure 4, the resonant capacitor current can be calculated by sampling the resonant capacitor differential voltage through the following formula:

[0073] Since the resonant capacitor and the resonant inductor are in the same current loop, their currents are equal. After calculating the resonant capacitor current, the resonant current i Lr =i cr .

[0074] In addition, the current sampling value of the rectifier unit can be directly sampled and obtained inside the rectifier unit by the above method, and the total current of all rectifier units can also be sampled. The current sampling value of the rectifier unit is determined by the sum of the total current and the current sampling value of other rectifier units.

[0075] In the rectifier unit adopting the combination of the bridge topology and the LLC resonant tank, the input three-phase alternating current is outputted as voltage through the loop formed by the bridge topology and the LLC resonant tank. The output current of the rectifier unit is related to the resonant current of the resonant tank, and the size of the resonant current is related to the input excitation of the resonant tank. Therefore, the size of the output current of the rectifier unit can be controlled by controlling the size of the input excitation of the resonant tank. The switch tube in the bridge topology is in the state of conduction or disconnection under the control of the control signal. The state of the rectifier circuit can be changed by adjusting the phase of the control signal, so as to achieve the purpose of controlling the size of the input excitation of the resonant tank.

[0076] After the current sampling values of the at least two rectifier units are obtained by sampling the currents of the at least two rectifier units, the error between the output currents of the rectifier units can be directly obtained by comparing the sizes of the current sampling values. The control signals of the switch tubes are adjusted according to the error, so as to reduce or even eliminate the error between the input excitations of the resonant tanks of the at least two rectifier units. In the rectifier unit adopting the combination of the bridge topology and the LLC resonant tank, when the bridge arm is in the full-conduction state of the upper and lower tubes, the input voltage Upn of the resonant tank of the rectifier unit is at the 0 level. At this time, the effective energy transmission time of the resonant tank to the secondary side of the transformer is reduced, so as to change the output current of the rectifier unit.

[0077] The phase of the control signal of the switch tube is adjusted in the present application, the phase shift angle between the switch tubes is changed, the time length of the bridge arm in the full-conduction state of the upper and lower tubes is increased or reduced, the effective energy transmission time of the resonant tank to the secondary side of the transformer is increased or reduced, and the output current of the rectifier unit is increased or reduced.

[0078] As shown in FIG. 5, the AC-DC converter includes two rectifier units U1 and U2. The circuit structure of the rectifier units U1 and U2 is shown in FIG. 4. The method of the embodiment of the present application is explained. The current sampling value i1 of the rectifier unit U1 and the current sampling value i2 of the rectifier unit U2 are obtained. According to the sizes of i1 and i2, the phase shift angle of the rectifier unit U1 and / or the rectifier unit U2 is adjusted, the phase of the control signal of the switch tube is changed, one bridge arm in the bridge topology of the rectifier unit U1 and / or the rectifier unit U2 is in the full-conduction state of the upper and lower tubes, or the time length of the full-conduction state is increased or reduced, the time length of Upn at the 0 level is changed, the effective energy transmission time of the resonant tank to the secondary side of the transformer is changed, and the output current of the rectifier unit is changed.

[0079] For example, when i1>i2, as shown in FIG. 6, the rectifier unit U1 has a control signal with an initial phase shift angle of 180°, when the three-phase input voltage Ua>0, Ub<0, Uc<0, and |Ua|>|Ub|>|Uc|, the A-phase connected switch tube is: Sa1 and Sa4 are always on, Sa2 and Sa3 are 50% duty cycle complementary wave, and the time between the falling edge of Sa2 and the falling edge of Sa3 is 180°. At this time, according to the error of i1 and i2, the phase shift angle of the rectifier unit U1 is adjusted to make the resonant tank voltage Upn of the rectifier unit U1 generate 0 level, reduce the time of the rectifier unit U1 to the transformer secondary side, further reduce the current of the rectifier unit U1, and ultimately achieve the purpose of current sharing. After phase shifting, the control signal of the rectifier unit U1 is shown in FIG. 7, in which the target phase shift angle of the rectifier unit U1 is 130°.

[0080] For the above example with two rectifier units, the following data obtained in actual operation:

[0081] The rated three-phase input voltage is 380V, 50HZ, the rated output voltage is 270V, and the rated output power is 50KW. Before using the phase shift current sharing control method provided by the present application, when the precision of the resonant inductance, resonant capacitance, and excitation inductance of the rectifier unit U1 is 5% less than that of the rectifier unit U1, the current sharing effect will be produced; and after using the method provided by the present application, the output current difference between the rectifier unit U1 and the rectifier unit U2 gradually decreases until the current sharing is completed and stabilized, as shown in the effect comparison diagram of FIGS. 8-10 (in this diagram, since the output current of the rectifier unit contains high-frequency switching ripple, for the convenience of observation, the instantaneous value of the output current of the rectifier unit is sampled, and then two-stage 100HZ low-pass filtered before being displayed).

[0082] Based on the above data, Table 1 and Table 2 can be determined, and it can be known that the resonant inductance has the greatest impact on the current sharing degree, the resonant capacitance has the second greatest impact, and the excitation inductance has the least impact.

[0083] Table 1: Current sharing degree without current sharing control

[0084] After adding the current sharing control method of the present application, the current sharing degree after the current sharing is completed and stabilized is as follows: the current sharing degree is less than 2%.

[0085] Table 2: Current sharing degree with current sharing control

[0086] The current sharing degree is calculated as follows:

[0087] In the formula, I avgis an average output current of each rectification unit; I max is a current sampling value of each rectification unit; I avg is an output current of the rectification unit with the largest deviation.

[0088] In the method provided by the above embodiment, current sampling values of at least two rectification units are obtained; target phase shift angles of each rectification unit are determined according to the current sampling values of the at least two rectification units, the target phase shift angles being used to indicate that the input voltage of the LLC resonant tank is in a 0 level state; and control signals of target switch tubes in a bridge topology structure of each rectification unit are controlled to be phase shifted according to the target phase shift angles of each rectification unit. The phase shift angles of the switch tubes in the rectification unit are adjusted, so that the input voltage of the LLC resonant tank is 0, thereby controlling the output current of each rectification unit, and achieving the effect that the outputs of the multiple rectification units are in current sharing.

[0089] In one of the embodiments, as shown in FIG. 11, determining the target phase shift angle of each rectification unit according to the current sampling values of the at least two rectification units includes:

[0090] In step 1102, current errors corresponding to each rectification unit are determined according to the current sampling values of the at least two rectification units;

[0091] In step 1104, the current error corresponding to each rectification unit is input into a preset current sharing loop, and the output of the preset current sharing loop is subjected to amplitude limiting processing to obtain a phase shift angle adjustment amount corresponding to each rectification unit;

[0092] In step 1106, the target phase shift angle of each rectification unit is determined according to the phase shift angle adjustment amount corresponding to each rectification unit and an initial value of the phase shift angle.

[0093] The current error refers to an error between the current sampling value and a specific current value, and the current error of each rectification unit refers to an error between the current sampling value of the rectification unit and the same specific current value. The specific current value can be a current sampling value of any rectification unit in the at least two rectification units, can be determined according to the current sampling values of the at least two rectification units, or can be artificially set based on the working state of the converter.

[0094] The current error corresponding to each rectification unit is input into a preset current sharing loop, and the phase shift angle adjustment amount corresponding to each rectification unit is obtained through the preset current sharing loop operation and current sharing loop output limiting. The target phase shift angle is determined in combination with the initial value of the phase shift angle. The number of preset current sharing loops is at least one and at most determined based on the number of rectification units. When there is only one preset current sharing loop, the current error of each rectification unit is sequentially input into the preset current sharing loop to obtain the phase shift angle adjustment amount of each rectification unit. When there are multiple preset current sharing loops, for example, one preset current sharing loop corresponds to each rectification unit, the current error of each rectification unit is input into the corresponding preset current sharing loop to obtain the phase shift angle adjustment amount.

[0095] The preset current sharing loop in the embodiment of the application can adopt an integral controller, and can also adopt a proportional-integral controller or other general controllers. The feature of the preset current sharing loop is that the phase shift angle adjustment amount can be calculated based on the current error. For example, the preset current sharing loop adopts a PI controller.

[0096] In the method provided in the above embodiment, the phase shift angle adjustment amount of each rectification unit is obtained by inputting the current error into the preset current sharing loop, and the output current of each rectification unit is close to a specific current value through adjustment based on the phase shift angle adjustment amount, so that the current sharing effect is achieved.

[0097] In one of the embodiments, the current error corresponding to each rectification unit is determined based on the current sampling values of the at least two rectification units, and the method comprises the following steps.

[0098] The current sampling values of the at least two rectification units are compared to determine the minimum value among the current sampling values of the at least two rectification units.

[0099] The difference between the current sampling value of each rectification unit and the minimum value is taken as the current error corresponding to each rectification unit.

[0100] In the embodiment, the minimum value among the current sampling values of the at least two rectification units is taken as the specific current value, and the current error is the difference between the current sampling value of each rectification unit and the minimum value. The target phase shift angle of each rectification unit determined based on the current error can adjust the output current of each rectification unit to a value close to the minimum value, and the rectification unit with the minimum value keeps the output current unchanged, so that the output current of all rectification units is balanced.

[0101] With the current error defined in the embodiments of the present application, taking the AC-DC converter including two rectifier units U1 and U2 and the initial phase shift angle of the rectifier units U1 and U2 being 180° as an example, the block diagram of the current sharing control method can be shown in FIG. 12. Wherein, i1 is the current sampling value of the rectifier unit U1; i2 is the current sampling value of the rectifier unit U2; Δθ1 is the phase shift angle adjustment of the switch tube of the rectifier unit U1; Δθ2 is the phase shift angle adjustment of the switch tube of the rectifier unit U2; θ1 is the phase shift angle of the switch tube of the rectifier unit U1; θ2 is the phase shift angle of the switch tube of the rectifier unit U2. The corresponding current sharing control method is as follows:

[0102] (1) When i1>i2, the current error value is positive, and after the integral operation of the current sharing loop, the output is positive, and after the limiting, Δθ1>0 and Δθ2=0. The target phase shift angle of the rectifier unit U1 is less than 180°, the target phase shift angle of the rectifier unit U2 is 180°, the three-phase lower tube drive of the rectifier unit U1 is shifted to the left, so that the 0 level is generated in the resonant tank voltage Upn of the rectifier unit U1, thereby reducing the energy transmission time of the rectifier unit U1 to the secondary side of the transformer, further reducing the current of the rectifier unit U1, and finally achieving the current sharing purpose.

[0103] (2) When i1<i2, the current error value is negative, and after the integral operation of the current sharing loop, the output is negative, and after the limiting, Δθ2<0 and Δθ1=0. The target phase shift angle of the rectifier unit U1 is 180°, the target phase shift angle of the rectifier unit U2 is less than 180°, the three-phase lower tube drive of the rectifier unit U2 is shifted to the left, so that the 0 level is generated in the resonant tank voltage Upn of the rectifier unit U2, thereby reducing the energy transmission time of the rectifier unit U2 to the secondary side of the transformer, further reducing the current of the rectifier unit U2, and finally achieving the current sharing purpose.

[0104] In the method provided in the above embodiments, by comparing the size of the current sampling value, the error between the current sampling value of each rectifier unit and the minimum value is input to the current sharing loop, so that the output currents of all rectifier units are close to or equal to the minimum value, and the effect of balancing the output currents is achieved. When the number of rectifier units is small, only one preset current sharing loop can be set, and the current sampling value is directly input, thereby improving the current sharing control efficiency.

[0105] In one of the embodiments, the current error corresponding to each rectifier unit is determined according to the current sampling values of the at least two rectifier units, including:

[0106] The average current value of the at least two rectifier units is determined according to the current sampling values of the at least two rectifier units.

[0107] The difference between the current sampling value of each rectifier unit and the average current value is taken as the current error corresponding to each rectifier unit.

[0108] In this embodiment, the average current value of the at least two rectifier units is taken as the specific current value, and each rectifier unit is adjusted so that the output current of each rectifier unit after adjustment is close to the average current value. The average value of the current sampling values of the at least two rectifier units can be calculated from the current sampling values of the at least two rectifier units, or can be determined by sampling the total output current of the at least two rectifier units.

[0109] By adjusting all rectifier units and adjusting the current sampling value of each rectifier unit to a value close to the specific current value, since the phase shift angle has a certain range, the method of this embodiment can avoid the situation that the difference between the current sampling value of one rectifier unit and the specific current value is large, and the phase shift angle adjustment cannot achieve current sharing or the current sharing effect is poor.

[0110] With the current error defined in the embodiments of the present application, taking an AC-DC converter including two rectifier units U1 and U2 and the initial values of the phase shift angles of the rectifier units U1 and U2 being 170° as an example, the block diagram of the current sharing control method can be as shown in FIG. 13. Wherein, i1 is the current sampling value of the rectifier unit U1; i2 is the current sampling value of the rectifier unit U2; iavg is the average value of i1 and i2; Δθ1 is the phase shift angle adjustment of the switch tube of the rectifier unit U1; Δθ2 is the phase shift angle adjustment of the switch tube of the rectifier unit U2; θ1 is the phase shift angle of the switch tube of the rectifier unit U1; θ2 is the phase shift angle of the switch tube of the rectifier unit U2. The corresponding current sharing control method is:

[0111] (1) When i1>i2: i1>iavg, the current error value is positive, after the current sharing loop integration operation, the output is positive, after the limiting, Δθ1>0, the target phase shift angle of the rectifier unit U1 becomes smaller, the length of the Upn at the 0 level becomes longer, and the output current of the rectifier unit U1 decreases accordingly; i2<iavg, the current error value is negative, after the current sharing loop integration operation, the output is negative, after the limiting, Δθ2<0, the target phase shift angle of the rectifier unit U2 becomes larger, the length of the Upn at the 0 level becomes shorter, and the output current of the rectifier unit U2 increases accordingly.

[0112] (2) When i1<i2, the above process is opposite.

[0113] It should be noted that when the current average value is used to determine the current error, the output current of some rectifier units needs to be adjusted to be smaller, and the output current of some rectifier units needs to be adjusted to be larger. When the phase shift angle is adjusted to be larger, the maximum value of the target phase shift angle is 180°, and therefore, it is possible that the output current of some rectifier units cannot be adjusted to be larger.

[0114] In the above embodiments, the initial phase shift angle is relative to the previous switching period, and the phase shift angle before the current adjustment time is taken as the initial phase shift angle for this adjustment. The amplitude limiting range of the amplitude limiting process corresponding to the phase shift angle adjustment amount of each rectification unit is related to the initial phase shift angle of each rectification unit. For example, in FIG. 12, the initial phase shift angle is 180°, and the amplitude limiting range is 0-180°. In FIG. 13, the initial phase shift angle is 170°, and the amplitude limiting range is -10-170°. In FIG. 14, the initial phase shift angles of the two rectification units are both 180°, but the amplitude limiting range of one rectification unit is -10°-180°, and the amplitude limiting range of the other rectification unit is -180°-10°. The output of the preset current sharing ring in the embodiments of the present application is subjected to appropriate amplitude limiting process set for the rectification unit, and the phase shift angle adjustment amount of the corresponding rectification unit is output.

[0115] In one of the embodiments, the control signal of the target switch in the bridge topology of each rectification unit is shifted according to the target phase shift angle of each rectification unit, including:

[0116] The control signal of the upper switch of each bridge arm in the bridge topology of each rectification unit is shifted to the left according to the target phase shift angle of each rectification unit; or,

[0117] The control signal of the upper switch of each bridge arm in the bridge topology of each rectification unit is shifted to the right according to the target phase shift angle of each rectification unit; or,

[0118] The control signal of the lower switch of each bridge arm in the bridge topology of each rectification unit is shifted to the left according to the target phase shift angle of each rectification unit; or,

[0119] The control signal of the lower switch of each bridge arm in the bridge topology of each rectification unit is shifted to the right according to the target phase shift angle of each rectification unit.

[0120] Since the control signal of the switch in the bridge topology is a periodic signal, the phase shift angle of the control signal between two switches is relative, and therefore, after the target phase shift angle is determined, there are multiple phase shift schemes to adjust the phase shift angle. As shown in the signal diagrams of FIGS. 6 and 7, FIG. 7 adopts the scheme of shifting the control signal of the lower switch of each bridge arm to the left to adjust the phase shift angle. Relative to the control signal of FIG. 6, the scheme of shifting the control signal of the upper switch of each bridge arm to the left as shown in FIG. 14, the scheme of shifting the control signal of the upper switch of each bridge arm to the right as shown in FIG. 15, and the scheme of shifting the control signal of the lower switch of each bridge arm to the right as shown in FIG. 16 can also be adopted.

[0121] In the method provided by the above embodiment, various phase shift modes are given, and a suitable phase shift mode is selected according to a specific application scene, and the flexibility is higher.

[0122] It should be understood that, although each step in the flowchart involved in each of the above embodiments is shown in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other sequences. Moreover, at least part of the steps in the flowchart involved in each of the above embodiments can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed alternately or alternately with at least part of other steps or steps or stages in other steps.

[0123] Based on the same inventive concept, the embodiment of the present application also provides an AC-DC conversion system, as shown in Figure 17, the system 1700 includes an AC-DC converter 1701 and a current sharing controller 1702; the AC-DC converter includes at least two rectifier units, and each of the at least two rectifier units adopts a combination of a bridge topology and an LLC resonant tank;

[0124] The current sharing controller is configured to control the working state of the AC-DC converter, and is specifically configured to execute the method steps in any one of the above embodiments.

[0125] As shown in Figure 18, the embodiment of the present application provides a computer device 1800, which includes a memory 1801 and a processor 1802.

[0126] The memory 1801 is configured to store computer executable instructions executable by the processor.

[0127] The processor 1802 implements each step in the method in the above embodiment when executing the computer executable instructions. For details, please refer to the related description in the foregoing method embodiment.

[0128] Optionally, the above memory 1801 can be independent or integrated with the processor 1802. When the memory 1801 is independently arranged, the computer device further includes a bus for connecting the memory 1801 and the processor 1802.

[0129] The embodiment of the present application also provides a computer readable storage medium, and the computer readable storage medium stores computer executable instructions. When the processor executes the computer executable instructions, each step in the method in the above embodiment is implemented.

[0130] The embodiment of the present application further provides a computer program product comprising computer execution instructions, which, when executed by a processor, implement all the steps in the method in the above embodiment.

[0131] Those skilled in the art can understand that all or part of the processes in the above method embodiment can be completed by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer readable storage medium. The computer execution instructions in the computer program can include the processes of the above method embodiments when executed. Any reference to memory, database or other medium in the embodiments provided by the present application can include at least one of non-volatile and volatile memory. The non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. The volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, the RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided by the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided by the present application can be a general processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0132] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0133] The above-described embodiments are merely illustrative of several embodiments of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A current sharing control method, characterized by, The application is applied to a current sharing controller used for controlling the working state of an AC-DC converter, the AC-DC converter comprising at least two rectification units, each of which adopts a bridge topology combined with an LLC resonant tank; the method comprises: obtaining current sampling values of the at least two rectification units; determining a target phase shift angle of each rectification unit according to the current sampling values of the at least two rectification units, the target phase shift angle being used for indicating the duration of the input voltage of the LLC resonant tank being in a 0 level state; controlling the control signal of a target switch tube in the bridge topology of each rectification unit to be phase shifted according to the target phase shift angle of each rectification unit.

2. The method of claim 1, wherein, The method of determining the target phase shift angle of each rectification unit according to the current sampling values of the at least two rectification units comprises: determining a current error corresponding to each rectification unit according to the current sampling values of the at least two rectification units; inputting the current error corresponding to each rectification unit into a preset current sharing loop, performing amplitude limiting processing on the output of the preset current sharing loop, and obtaining a phase shift angle adjustment amount corresponding to each rectification unit; determining the target phase shift angle of each rectification unit according to the phase shift angle adjustment amount corresponding to each rectification unit and an initial value of the phase shift angle.

3. The method of claim 2, wherein, The method of determining the current error corresponding to each rectification unit according to the current sampling values of the at least two rectification units comprises: comparing the current sampling values of the at least two rectification units to determine the minimum value among the current sampling values of the at least two rectification units; taking the difference between the current sampling value of each rectification unit and the minimum value as the current error corresponding to each rectification unit.

4. The method of claim 2, wherein, The method of determining the current error corresponding to each rectification unit according to the current sampling values of the at least two rectification units comprises: determining an average current value of the at least two rectification units according to the current sampling values of the at least two rectification units; taking the difference between the current sampling value of each rectification unit and the average current value as the current error corresponding to each rectification unit.

5. The method of claim 2, wherein, The amplitude limiting range of the amplitude limiting processing corresponding to the phase shift angle adjustment amount of each rectification unit is related to the initial value of the phase shift angle of each rectification unit.

6. The method of claim 1, wherein, The method of controlling the control signal of a target switch tube in the bridge topology of each rectification unit to be phase shifted according to the target phase shift angle of each rectification unit comprises: controlling the control signal of the upper switch tube of each bridge arm in the bridge topology of each rectification unit to be phase shifted to the left according to the target phase shift angle of each rectification unit; or, controlling the control signal of the upper switch tube of each bridge arm in the bridge topology of each rectification unit to be phase shifted to the right according to the target phase shift angle of each rectification unit; or, controlling the control signal of the lower switch tube of each bridge arm in the bridge topology of each rectification unit to be phase shifted to the left according to the target phase shift angle of each rectification unit; or, controlling the control signal of the lower switch tube of each bridge arm in the bridge topology of each rectification unit to be phase shifted to the right according to the target phase shift angle of each rectification unit.

7. The method according to any one of claims 1 to 6, characterized in that, The current sampling values include one or more of input current sampling values, rectified output current sampling values, resonant current sampling values, switch tube current sampling values, and transformer secondary side current sampling values.

8. An AC-DC conversion system, characterized by, The system comprises an AC-DC converter and a current sharing controller; the AC-DC converter comprises at least two rectification units, each of which adopts a combination of a bridge topology and an LLC resonant tank; The current sharing controller executes the method steps of any one of claims 1-7 to control the working state of the AC-DC converter.

9. A computer device, comprising: Comprise: A processor, and a memory connected in communication with the processor; The memory stores computer execution instructions; The processor executes the computer execution instructions stored in the memory to realize the method of any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer execution instructions, and the computer execution instructions are executed by the processor to realize the method of any one of claims 1 to 7.

11. A computer program product, characterised in that, Comprise computer execution instructions, and the computer execution instructions are executed by the processor to realize the method of any one of claims 1 to 7.

Images