A quad-active bridge converter and its control method and control system

Abstract

The present invention discloses a four-active bridge converter and its control method and control system, belonging to the field of electric energy conversion technology. The method includes performing PI regulation on the output current reference value and the sampled output current to obtain the small-signal phase shift angle of the PI-regulated output; using the sampled output current and parameter information of the four-active bridge converter, calculating the approximate solution of the steady-state operating point phase shift angle through the Newton-Raphson iteration method; using the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iteration method to calculate the small-signal function model between the control variable and the output variable of the four-active bridge converter, and calculating the feedforward decoupling network; sending the small-signal phase shift angle of the PI-regulated output into the feedforward decoupling network to obtain the decoupled small-signal phase shift angle, and adding it to the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iteration method to obtain the value of each phase shift angle under single phase shift modulation. The present invention can effectively suppress power coupling between the ports of the four-active bridge converter.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to a quad-active bridge converter and a control method and control system thereof. Background Art

[0002] The quad active bridge converter (QAB) is a highly efficient, isolated, multi-port DC-DC (DC-DC) converter that achieves electrical isolation through a multi-winding high-frequency transformer. It features a compact structure, bidirectional energy flow, high energy density, small size, and high efficiency. It is widely used in new energy vehicles, DC microgrids, photovoltaic medium-voltage power generation, and other fields.

[0003] In single-phase-shift (SPS) modulation mode, a four-bridge converter transmits power through a multi-winding high-frequency transformer composed of multiple bridge modules sharing a single transformer core. This results in strong coupling between the ports, and the output power of distributed energy resources is subject to significant uncertainty and volatility. This dynamic characteristic is highly susceptible to cross-disturbance. Power fluctuations at one port can be transmitted to other ports through the core's magnetic circuit coupling, causing fluctuations at other ports, degrading the dynamic performance and reliability of the four-bridge converter. Furthermore, the overlapping energy paths can affect the efficiency of the entire converter.

[0004] Therefore, how to perform power decoupling control on the quad-active bridge converter to improve its dynamic performance and ensure stable and efficient power transmission has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention aims to provide a quad-active bridge converter and a control method and a control system thereof.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A control method for a quad active bridge converter, comprising:

[0008] Step S1, sampling the output current;

[0009] Step S2: Subtracting the output current reference value from the sampled output current, performing PI regulation to obtain a small-signal phase shift angle of the PI-regulated output; and using the sampled output current and parameter information of the four-active-bridge converter, calculating an approximate solution of the steady-state operating point phase shift angle in real time through a Newton-Raphson iteration method.

[0010] Step S3, using the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to calculate in real time the small signal function model between the control variables and the output variables of the four-active bridge converter, and to calculate in real time the feedforward decoupling network;

[0011] In step S4, the small signal phase shift angle output by the PI regulation is sent to the feedforward decoupling network to obtain the decoupled small signal phase shift angle, and the phase shift angle is added to the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to obtain the value of each phase shift angle under single phase shift modulation.

[0012] Furthermore, in step S2, the output current reference value of the second port is The difference between the output current I2 of the second port is obtained through PI regulation to obtain the small signal phase shift angle between the first port and the second port of the PI regulation output. ; Set the output current reference value of the third port The difference between the output current I3 of the third port is obtained through PI regulation to obtain the small signal phase shift angle between the first port and the third port of the PI regulation output. ; Set the output current reference value of the fourth port The small signal phase shift angle between the first port and the fourth port of the PI regulation output is obtained by subtracting the output current I4 from the fourth port. .

[0013] Furthermore, in step S2, the formula for the approximate solution of the steady-state operating point phase shift angle is calculated in real time by the Newton-Raphson iteration method as follows:

[0014] ,

[0015] in, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the Nth iteration, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the N+1th iteration, is a basic real-valued function, is the Jacobian matrix;

[0016] The approximate solution matrix of the phase shift angle at the steady-state operating point of the Nth iteration The expression is as follows:

[0017] ,

[0018] in, is the approximate solution of the steady-state operating point phase shift angle between the first port and the second port, is the approximate solution of the steady-state operating point phase shift angle between the first port and the third port, is the approximate solution for the steady-state operating point phase shift angle between the first port and the fourth port.

[0019] Furthermore, the basic real-valued function The expression is as follows:

[0020]

[0021] in, is the target power of the second port, is the target power of the third port, is the target power of the fourth port, is the actual iterative power of the second port, is the actual iterative power of the third port, is the actual iterative power of the fourth port.

[0022] Furthermore, the Jacobian matrix The expression is:

[0023] .

[0024] Furthermore, in step S3, the small signal function model between the control variables and the output variables of the four active bridge converter is:

[0025] ,

[0026] in, is the small signal value of the output current of the second port, is the small signal value of the output current of the third port, is the small signal value of the output current of the fourth port, is the phase shift angle between the first port and the second port after decoupling, is the phase shift angle between the first port and the third port after decoupling, is the phase shift angle between the first port and the fourth port after decoupling;

[0027] Parameter G in the G matrix ij Expressed as:

[0028]

[0029] Among them, V p is the voltage across the p-th port, L ip is the power equivalent inductance between the i-th port and the p-th port, is the phase shift angle of the steady-state operating point of the i-th port, is the phase shift angle of the steady-state operating point of the p-th port, is the phase shift angle of the steady-state operating point of the jth port, V j is the voltage across the j-th port, L ij is the power equivalent inductance between the i-th port and the j-th port.

[0030] Furthermore, the expressions of the parameters in the feedforward decoupling network D are:

[0031] .

[0032] Furthermore, in step S4, the small signal phase shift angle between the first port and the second port of the PI regulation output is set to , the small signal phase shift angle between the first port and the third port of the PI regulation output , the small signal phase shift angle between the first port and the fourth port of the PI regulation output In the input feedforward decoupling network, the phase shift angle between the first port and the second port after decoupling is calculated. , the phase shift angle between the first port and the third port after decoupling , the phase shift angle between the first port and the fourth port after decoupling , respectively, and the approximate solution of the steady-state operating point phase shift angle between the first port and the second port , the approximate solution of the phase shift angle at the steady-state operating point between the first port and the third port , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port Superposition, get the phase shift angle between the first port and the second port under single phase shift modulation , Phase shift angle between the first port and the third port , Phase shift angle between the first port and the fourth port ;

[0033] The relationship between the phase shift angles of different ports and the phase shift angles between ports is as follows:

[0034] ,

[0035] in, is the first port phase shift angle, is the second port phase shift angle, is the third port phase shift angle, is the fourth port phase shift angle.

[0036] The present invention also provides a control system for a four-active bridge converter, which applies the above-mentioned control method for a four-active bridge converter. The control system of the four-active bridge converter includes a Newton-Raphson calculation module, a feedforward decoupling network module, a driving module, a first PI adjustment module, a second PI adjustment module, and a third PI adjustment module. The input of the first PI adjustment module is connected to the difference between the output current reference value of the second port and the output current of the second port, and the output of the first PI adjustment module is connected to the input of the feedforward decoupling network module; the input of the second PI adjustment module is connected to the difference between the output current reference value of the third port and the output current of the third port. value, the output of the second PI adjustment module is connected to the input of the feedforward decoupling network module; the input of the third PI adjustment module is connected to the difference between the output current reference value of the fourth port and the output current of the fourth port, and the output of the third PI adjustment module is connected to the input of the feedforward decoupling network module; the input of the Newton-Raphson calculation module is connected to the voltage across each port, and the output of the Newton-Raphson calculation module is connected to the input of the feedforward decoupling network module; the output of the feedforward decoupling network module and the output of the Newton-Raphson calculation module are superimposed and connected to the input of the driving module, and the output of the driving module is connected to the four active bridge converters.

[0037] The present invention also provides a four-active bridge converter, which uses the above-mentioned control method of the four-active bridge converter, including a first bridge module, a second bridge module, a third bridge module, a fourth bridge module, and a transformer module, wherein the first end of the first bridge module is connected in parallel to the first port, the second end of the first bridge module is connected in parallel to the first end of the transformer module, the first end of the second bridge module is connected in parallel to the second port, the second end of the second bridge module is connected in parallel to the second end of the transformer module, the first end of the third bridge module is connected in parallel to the third port, the second end of the third bridge module is connected in parallel to the third end of the transformer module, the first end of the fourth bridge module is connected in parallel to the fourth port, and the second end of the fourth bridge module is connected in parallel to the fourth end of the transformer module.

[0038] Beneficial effect: The present invention provides a four-active bridge converter and its control method and control system, which can effectively suppress the power coupling phenomenon between ports of the four-active bridge converter caused by the four ports sharing a magnetic core through the Newton-Raphson iteration method and combined with the feedforward decoupling network; while reducing the amount of calculation, it can realize decoupling control in real time and significantly optimize the dynamic performance of the four-active bridge converter.

[0039] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the circuit of the four active bridge converter of the present invention.

[0041] Figure 2 for Figure 1 Power transfer equivalent model of the four-bridge active converter.

[0042] Figure 3 This is a flow chart of a control method for a quad-active bridge converter according to the present invention.

[0043] Figure 4 Schematic diagram of the feedforward decoupling network and small signal function model.

[0044] Figure 5 for Figure 3 Flowchart of step S2 in FIG.

[0045] Figure 6 The figure is a structural diagram of a control system of a quad-active bridge converter according to the present invention.

[0046] Figure 7 The figure shows the current dynamic response simulation waveforms of the traditional method and the method of the present invention.

[0047] Figure 8 The figure shows the power dynamic response simulation waveforms of the traditional method and the method of the present invention.

[0048] Figure 9 This is a waveform diagram of the inductor current change when the output current I2 of the second port in the method of the present invention changes from 20A to 50A.

[0049] Figure 10 This is the dynamic response curve of the output current of each port when the output current I2 of the second port changes from 20A to 50A in the traditional method.

[0050] Figure 11 This is the dynamic response curve of the output current of each port when the output current I2 of the second port changes from 20A to 50A in the method of the present invention. DETAILED DESCRIPTION

[0051] To make the purpose and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Below Figure 1 Taking the four active bridge converter in FIG. 1 as an example, a control method of the four active bridge converter of the present invention is introduced.

[0053] like Figure 1As shown, the four-active bridge converter 1 includes a first bridge module 11, a second bridge module 12, a third bridge module 13, a fourth bridge module 14, and a transformer module 15. The first end of the first bridge module 11 is connected in parallel to the first port, the second end of the first bridge module 11 is connected in parallel to the first end of the transformer module 15, the first end of the second bridge module 12 is connected in parallel to the second port, the second end of the second bridge module 12 is connected in parallel to the second end of the transformer module 15, the first end of the third bridge module 13 is connected in parallel to the third port, the second end of the third bridge module 13 is connected in parallel to the third end of the transformer module 15, the first end of the fourth bridge module 14 is connected in parallel to the fourth port, and the second end of the fourth bridge module 14 is connected in parallel to the fourth end of the transformer module 15. The voltage across the first port is V1, the voltage across the second port is V2, the voltage across the third port is V3, and the voltage across the fourth port is V4. The voltage across the second end of the first bridge module 11 is U1, the voltage across the second end of the second bridge module 12 is U2, the voltage across the second end of the third bridge module 13 is U3, and the voltage across the second end of the fourth bridge module 14 is U4.

[0054] Furthermore, the first bridge module 11 includes a switch S1, a switch S2, a switch S3, and a switch S4. The switch S1 is connected in series with the switch S2, and the switch S3 is connected in series with the switch S4. The two ends of the series connection of the switch S1 and the switch S2 and the two ends of the series connection of the switch S3 and the switch S4 are connected in parallel to form a first end of the first bridge module 11. The midpoint of the series connection of the switch S1 and the switch S2 and the midpoint of the series connection of the switch S3 and the switch S4 are the second end of the first bridge module 11.

[0055] Furthermore, the second bridge module 12 includes a switch S5, a switch S6, a switch S7, and a switch S8. The switch S5 is connected in series with the switch S6, and the switch S7 is connected in series with the switch S8. The two ends of the series connection of the switch S5 and the switch S6 and the two ends of the series connection of the switch S7 and the switch S8 are connected in parallel to form a first end of the second bridge module 12. The midpoint of the series connection of the switch S5 and the switch S6 and the midpoint of the series connection of the switch S7 and the switch S8 are the second end of the second bridge module 12.

[0056] Furthermore, the third bridge module 13 includes a switch S9, a switch S 10 , switch S 11 , switch S 12 , switch S9 and switch S 10 Series, switch S 11 With switch S 12 In series, switch S9 and switch S 10 The two ends of the series connection, switch S 11 With switch S 12 The two ends of the series connection are connected in parallel to form the first end of the third bridge module 13, and the switch S9 and the switch S 10 The series midpoint, switch S 11 With switch S 12The series midpoint of the connections is the second end of the third bridge module 13 .

[0057] Furthermore, the fourth bridge module 14 includes a switch S 13 , switch S 14 , switch S 15 , switch S 16 , switch S 13 With switch S 14 Series, switch S 15 With switch S 16 Series, switch S 13 With switch S 14 The two ends of the series connection, switch S 15 With switch S 16 The two ends after series connection are connected in parallel to form the first end of the fourth bridge module 14, and the switch S 13 With switch S 14 The series midpoint, switch S 15 With switch S 16 The series midpoint of the circuit is the second end of the fourth bridge module 14 .

[0058] Furthermore, the transformer module 15 includes an inductor L1, an inductor L2, an inductor L3, an inductor L4 and a transformer T r , the first terminal of the inductor L1 is connected to the transformer T r The first terminal of the first winding N1, the second terminal of the inductor L1 and the second terminal of the first winding N1 are the first end of the transformer module 15; the transformer T r The first terminal of the second winding N2 is connected to the first terminal of the inductor L2, and the second terminal of the second winding N2 and the second terminal of the inductor L2 are the second end of the transformer module 15; the transformer T r The first terminal of the third winding N3 is connected to the first terminal of the inductor L3, and the second terminal of the third winding N3 and the second terminal of the inductor L3 are the third end of the transformer module 15; the transformer T r The first terminal of the fourth winding N4 is connected to the first terminal of the inductor L4, and the second terminal of the third winding N4 and the second terminal of the inductor L4 are the fourth end of the transformer module 15. r For multi-winding transformer.

[0059] Optionally, the first bridge module 11 further includes a capacitor C1 , which is connected in parallel to a first end of the first bridge module 11 .

[0060] Optionally, the second bridge module 12 further includes a capacitor C2 , which is connected in parallel to the first end of the second bridge module 12 .

[0061] Optionally, the third bridge module 13 further includes a capacitor C3 , which is connected in parallel to the first end of the third bridge module 13 .

[0062] Optionally, the fourth bridge module 14 further includes a capacitor C4 , which is connected in parallel to the first end of the fourth bridge module 14 .

[0063] More specifically, the current at the first port is i 1. The current at the second port is i 2. The current at the third port is i 3. The current at the fourth port is i 4. The current flowing through inductor L1 is i L1 , the current flowing through the inductor L2 is i L2 , the current flowing through the inductor L3 is i L3 , the current flowing through the inductor L4 is i L4 .

[0064] Figure 2 for Figure 1 The power transmission equivalent model of the four-bridge active converter is shown in Figure 2, where: i 12 is the current between the first port and the second port, i 13 is the current between the first port and the third port, i 14 is the current between the first port and the fourth port, i 23 is the current between the second port and the third port, i 24 is the current between the second port and the fourth port, i 34 is the current between the third and fourth ports, U2 ’ U3 is the voltage converted from the second end of the second bridge module 12 to the second end of the first bridge module 11, ’ U4 is the voltage converted from the second end of the third bridge module 13 to the second end of the first bridge module 11, ’ is the voltage of the second end of the fourth bridge module 14 converted to the second end of the first bridge module 11, i2 ’ is the current from the second port converted to the first port, i3 ’ is the current from the third port converted to the first port, i4 ’ is the current from the fourth port converted to the first port, L 12 is the power equivalent inductance between the first port and the second port, L 13 is the power equivalent inductance between the first port and the third port, L 14 is the power equivalent inductance between the first port and the fourth port, L 24 is the power equivalent inductance between the second port and the fourth port, L23 is the power equivalent inductance between the second port and the third port, L 34 is the power equivalent inductance between the third port and the fourth port.

[0065] like Figure 3 As shown, a control method for a quad-active bridge converter of the present invention includes steps S1 to S4.

[0066] Step S1, sampling the output current.

[0067] In step S2, the output current reference value and the sampled output current are subtracted to perform PI regulation to obtain the small signal phase shift angle of the PI regulated output; the sampled output current and the parameter information of the four-active bridge converter are used to calculate the approximate solution of the steady-state operating point phase shift angle in real time through the Newton-Raphson iteration method.

[0068] Step S3, using the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to calculate the small signal function model between the control variables and the output variables of the four-active bridge converter in real time, and to calculate the feedforward decoupling network in real time.

[0069] In step S4, the small signal phase shift angle output by the PI regulation is sent to the feedforward decoupling network to obtain the decoupled small signal phase shift angle, and the phase shift angle is added to the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to obtain the value of each phase shift angle under single phase shift modulation.

[0070] Optionally, the control method of the four-active-bridge converter of the present invention further includes, in step S5, generating a pulse width modulation (PWM) signal according to each phase shift angle to drive the switches of the four-active-bridge converter to control the operation of the four-active-bridge converter.

[0071] More specifically, in step S1, after the quad active bridge converter is started, the output current is sampled. The sampled output current specifically includes the output current I2 of the second port, the output current I3 of the third port, and the output current I4 of the fourth port.

[0072] More specifically, the sampled output current is a current instantaneous value.

[0073] Furthermore, in step S1 , a low-pass filtering module is used to perform low-pass filtering on the sampled output current.

[0074] More specifically, the transfer function of the low-pass filter module is as follows:

[0075]

[0076] in, is the damping ratio, which can be taken as 0.707; It is the undamped oscillation frequency and can be taken as one tenth of the switching period T.

[0077] Furthermore, in step S1 , a zero-order hold module is used on the output current after low-pass filtering to convert the discrete signal into a continuous signal.

[0078] More specifically, the transfer function of the zero-order hold module (ZOH) is as follows:

[0079]

[0080] Where T is the switching period.

[0081] Furthermore, in step S2, the output current reference value of the second port is The difference between the output current I2 of the second port is obtained through PI regulation to obtain the small signal phase shift angle between the first port and the second port of the PI regulation output. ; Set the output current reference value of the third port The difference between the output current I3 of the third port is obtained through PI regulation to obtain the small signal phase shift angle between the first port and the third port of the PI regulation output. ; Set the output current reference value of the fourth port The small signal phase shift angle between the first port and the fourth port of the PI regulation output is obtained by subtracting the output current I4 from the fourth port. .

[0082] Furthermore, in step S2, the formula for the approximate solution of the steady-state operating point phase shift angle is calculated in real time by the Newton-Raphson iteration method as follows:

[0083] ,

[0084] in, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the Nth iteration, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the N+1th iteration, is a basic real-valued function, is the Jacobian matrix.

[0085] More specifically, the approximate solution matrix of the steady-state operating point phase shift angle of the Nth iteration is The expression is as follows:

[0086] ,

[0087] in, is the approximate solution of the steady-state operating point phase shift angle between the first port and the second port, is the approximate solution of the steady-state operating point phase shift angle between the first port and the third port, is the approximate solution for the steady-state operating point phase shift angle between the first port and the fourth port.

[0088] More specifically, the approximate solution matrix of the phase shift angle at the steady-state operating point is The initial value can be set to

[0089] .

[0090] More specifically, the basic real-valued function The expression is as follows:

[0091]

[0092] in, is the target power of the second port, is the target power of the third port, is the target power of the fourth port, is the actual iterative power of the second port, is the actual iterative power of the third port, is the actual iterative power of the fourth port.

[0093] More specifically, the expression for the target power of each port is as follows:

[0094] .

[0095] More specifically, the expression for the actual iterative power of each port is as follows:

[0096]

[0097] Among them, P 2j is the transmission power between the second port and the jth port, P 3j is the transmission power between the third port and the jth port, P 4j is the transmission power between the fourth port and the jth port, f s is the switching frequency, V2' is the voltage converted from the second port to the first port, V3' is the voltage converted from the third port to the first port, V4' is the voltage converted from the fourth port to the first port, L 21 is the power equivalent inductance between the second port and the first port, L 31 is the power equivalent inductance between the third port and the first port, L 41 is the power equivalent inductance between the fourth port and the first port, L 23 is the power equivalent inductance between the second port and the third port, L 32 is the power equivalent inductance between the third port and the second port, L 42 is the power equivalent inductance between the fourth port and the second port, L 24is the power equivalent inductance between the second port and the fourth port, L 34 is the power equivalent inductance between the third port and the fourth port, L 43 is the power equivalent inductance between the fourth port and the third port, is the approximate solution of the steady-state operating point phase shift angle between the second port and the third port, is the approximate solution of the steady-state operating point phase shift angle between the second port and the fourth port, is the approximate solution for the phase shift angle at the steady-state operating point between the third and fourth ports.

[0098] More specifically, the approximate solution for the steady-state operating point phase shift angle between the second port and the third port is , the approximate solution of the steady-state operating point phase shift angle between the second port and the fourth port , the approximate solution of the phase shift angle at the steady-state operating point between the third port and the fourth port The expression is as follows:

[0099] .

[0100] More specifically, the voltage V2 converted from the second port to the first port ’ , the voltage V3 of the third port converted to the first port ’ , the voltage V4 of the fourth port converted to the first port ’ The expression is as follows:

[0101] .

[0102] More specifically, L 12 is the power equivalent inductance between the first port and the second port, L 21 is the power equivalent inductance between the second port and the first port, L 13 is the power equivalent inductance between the first port and the third port, L 31 is the power equivalent inductance between the third port and the first port, L 14 is the power equivalent inductance between the first port and the fourth port, L 41 is the power equivalent inductance between the fourth port and the first port, L 23 is the power equivalent inductance between the second port and the third port, L 32 is the power equivalent inductance between the third port and the second port, L 24 is the power equivalent inductance between the second port and the fourth port, L 42 is the power equivalent inductance between the fourth port and the second port, L 34 is the power equivalent inductance between the third port and the fourth port, L 43is the power equivalent inductance between the fourth port and the third port, and its expression is as follows:

[0103] ,

[0104] Among them, L ’ k is the inductance of the kth port converted to the first port, and the expression is as follows:

[0105] ,

[0106] In the above formula, the value of k is 2, 3 or 4.

[0107] More specifically, the Jacobian matrix The expression is:

[0108] .

[0109] More specifically, the Jacobian matrix The expression in the first line is:

[0110]

[0111] More specifically, the Jacobian matrix The expression in the second line is:

[0112]

[0113] More specifically, the Jacobian matrix The expression in the third line is:

[0114]

[0115] Further, in step S3, please refer to Figure 4 , the small signal function model between the control variables and output variables of the four-active bridge converter is:

[0116]

[0117] in, is the small signal value of the output current of the second port, is the small signal value of the output current of the third port, is the small signal value of the output current of the fourth port, is the phase shift angle between the first port and the second port after decoupling, is the phase shift angle between the first port and the third port after decoupling, is the phase shift angle between the first port and the fourth port after decoupling.

[0118] In the above formula, the parameter G in the G matrix ij Expressed as:

[0119]

[0120] Among them, V p is the voltage across the p-th port, L ip is the power equivalent inductance between the i-th port and the p-th port, is the phase shift angle of the steady-state operating point of the i-th port, is the phase shift angle of the steady-state operating point of the p-th port, is the phase shift angle of the steady-state operating point of the jth port, V j is the voltage across the j-th port, L ij is the power equivalent inductance between the i-th port and the j-th port, the value of i is 2~4, the value of j is 2~4, and the value of p is 2~4.

[0121] Among them, the phase shift angle of the first port steady-state operating point is , the phase shift angle of the second port steady-state operating point , the phase shift angle of the third port steady-state operating point , the phase shift angle of the fourth port steady-state operating point Calculated according to the following formula:

[0122] .

[0123] Furthermore, in step S3, the design idea of ​​the feedforward decoupling network is to eliminate the non-diagonal elements in the G matrix in the small signal model between the control variables and the output variables of the original four-active bridge converter through feedforward compensation, thereby eliminating the mutual influence between the ports and realizing decoupling control.

[0124] Please continue to refer to Figure 4 , the expression of the feedforward decoupling network D is:

[0125] ,

[0126] in, is the small signal phase shift angle between the first and second ports of the PI regulation output, is the small signal phase shift angle between the first and third ports of the PI regulation output, is the small signal phase shift angle between the first and fourth ports of the PI regulation output, is the phase shift angle between the first port and the second port after decoupling, is the phase shift angle between the first port and the third port after decoupling, is the phase shift angle between the first port and the fourth port after decoupling.

[0127] Therefore, the expression of the small signal function model changes to:

[0128] .

[0129] As mentioned above, the values ​​of the parameters in the feedforward decoupling network D should satisfy the off-diagonal elements in the above formula to be 0. Only in this way can the power coupling between the ports be eliminated and the dynamic performance of the four-active-bridge converter be improved.

[0130] Therefore, the expressions of the parameters in the feedforward decoupling network D are:

[0131] .

[0132] Furthermore, in step S4, the small signal phase shift angle between the first port and the second port of the PI regulation output is set to , the small signal phase shift angle between the first port and the third port of the PI regulation output , the small signal phase shift angle between the first port and the fourth port of the PI regulation output In the input feedforward decoupling network, the phase shift angle between the first port and the second port after decoupling is calculated. , the phase shift angle between the first port and the third port after decoupling , the phase shift angle between the first port and the fourth port after decoupling , respectively, and the approximate solution of the steady-state operating point phase shift angle between the first port and the second port , the approximate solution of the phase shift angle at the steady-state operating point between the first port and the third port , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port Superposition, get the phase shift angle between the first port and the second port under single phase shift modulation , Phase shift angle between the first port and the third port , Phase shift angle between the first port and the fourth port .

[0133] Furthermore, the relationship between the phase shift angles of different ports and the phase shift angles between ports is as follows:

[0134] ,

[0135] in, is the first port phase shift angle, is the second port phase shift angle, is the third port phase shift angle, is the fourth port phase shift angle. Therefore, when the first port phase shift angle is pre-set Under the premise of , Phase shift angle between the first port and the third port , Phase shift angle between the first port and the fourth port The second port phase shift angle can be obtained , the third port phase shift angle , the fourth port phase shift angle .

[0136] Optionally, for convenience and calculation, the first port phase shift angle can be Fixed to 0.

[0137] Furthermore, in step S5, the phase shift angle of each port is sent to the driving module, and the phase shift angle of the first port is The switch assigned to the first bridge module 11 shifts the second port phase by an angle The switch assigned to the second bridge module 12 shifts the phase angle of the third port The switch assigned to the third bridge module 13 shifts the fourth port phase by an angle The switches assigned to the fourth bridge module 14 output 16 pulse width modulation (PWM) signals to drive the switches of the four active bridge converters and control the operation of the four active bridge converters.

[0138] In one embodiment, the pulse width modulation signals of the switches in the same bridge arm are complementary.

[0139] In a specific embodiment, the duty cycle of the 16 pulse width modulation (PWM) signals is 0.5.

[0140] In a specific embodiment, if Figure 5 As shown, in step S2, before the approximate solution of the steady-state operating point phase shift angle is calculated in real time by the Newton-Raphson iteration method, the following steps S21 to S216 are also included.

[0141] Step S21, setting the target power of each port and the voltage across each port, specifically the target power of the second port , target power of the third port , target power of the fourth port , voltage V1 across the first port, voltage V2 across the second port, voltage V3 across the third port, and voltage V4 across the fourth port.

[0142] Step S22: Calculate the power equivalent inductance between each port, specifically the power equivalent inductance L between the first port and the second port. 12 , the power equivalent inductance L between the first port and the third port 13 , the power equivalent inductance L between the first port and the fourth port 14 , the power equivalent inductance L between the second port and the third port 23 , the power equivalent inductance L between the second port and the fourth port 24, the power equivalent inductance L between the third port and the fourth port 34 .

[0143] Step S23, set the constraint conditions: set the error phase shift angle φ error , maximum number of iterations N max .

[0144] Step S24, initialization setting: setting the initial value of the phase shift angle between each port and setting the number of iterations N to 0, specifically the approximate solution of the steady-state operating point phase shift angle between the first port and the second port , the approximate solution of the phase shift angle at the steady-state operating point between the first port and the third port , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port The initial value of .

[0145] Step S25: determine whether the number of iterations N is less than the maximum number of iterations N max If so, go to step S26; otherwise, go to step S216.

[0146] Step S26: Determine the approximate solution of the steady-state operating point phase shift angle between the first port and the second port. Does -π / 2< <π / 2, if so, go to step S27; otherwise, go to step S216.

[0147] Step S27: Calculate the transmission power P between the first port and the second port. 12 .

[0148] Step S28, determining the approximate solution of the steady-state operating point phase shift angle between the first port and the third port Does -π / 2< <π / 2, if so, go to step S29; otherwise, go to step S216.

[0149] Step S29: Calculate the transmission power P between the first port and the third port 13 .

[0150] Step S210: Determine the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port. Does -π / 2< <π / 2, if so, go to step S211; otherwise, go to step S216.

[0151] Step S211, calculate the transmission power P between the first port and the fourth port 14 .

[0152] Step S212: Determine the approximate solution of the steady-state operating point phase shift angle between the i-th port and the j-th port. Does -π / 2< <π / 2, if so, proceed to step S213; otherwise, proceed to step S216. Wherein, the value of i ranges from 1 to 4, the value of j ranges from 1 to 4, and i≠j.

[0153] Step S213: Calculate the transmission power P between the second port and the third port. 23 , the transmission power P between the second port and the fourth port 24 , the transmission power P between the third port and the fourth port 34 .

[0154] Step S214, according to Calculate the approximate solution of the phase shift angle at the steady-state operating point and set N=N+1.

[0155] Step S215: Determine the approximate solution matrix of the steady-state operating point phase shift angle of the N+1th iteration The approximate solution matrix of the phase shift angle of the steady-state operating point of the Nth iteration Is the difference less than the error phase shift angle φ error If so, go to step S216; otherwise, return to step S25 and continue execution.

[0156] More specifically, in step S215, the approximate solution matrix of the steady-state operating point phase shift angle of the N+1th iteration is determined. The three phase shift angles in the approximate solution matrix of the steady-state operating point phase shift angle of the Nth iteration Are the differences in the corresponding phase shift angles in the equation less than the error phase shift angle φ? error If so, go to step S216; otherwise, return to step S25 and continue execution.

[0157] Step S216: Output the phase shift angle in the approximate solution matrix of the steady-state operating point phase shift angle of this iteration, specifically, the approximate solution of the steady-state operating point phase shift angle between the first port and the second port. , the approximate solution of the steady-state operating point phase shift angle between the first port and the third port is , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port is .

[0158] More specifically, in steps S21 to S216, before calculating the approximate solution of the phase shift angle at the steady-state operating point, it is first determined whether the phase shift angles between the ports meet the range requirements. If not, no subsequent calculation is required and the process ends directly. If so, iterative calculation is performed. This ensures the reliability and fault tolerance of the control method for a four-active-bridge converter of the present invention.

[0159] like Figure 6As shown, the present invention also provides a control system 2 of a four-active bridge converter, which is connected to the four-active bridge converter 1. The control system 2 of the four-active bridge converter includes a Newton-Raphson calculation module 21, a feedforward decoupling network module 22, a drive module 23, a first PI adjustment module 24, a second PI adjustment module 25, and a third PI adjustment module 26. The input of the first PI adjustment module 24 is connected to the output current reference value of the second port. The output of the first PI adjustment module 24 is the small signal phase shift angle between the first port and the second port of the PI adjustment output. And connected to the input of the feedforward decoupling network module 22; the input of the second PI adjustment module 25 is connected to the output current reference value of the third port The output of the second PI adjustment module 25 is the small signal phase shift angle between the first port and the third port of the PI adjustment output. And connected to the input of the feedforward decoupling network module 22; the input of the third PI adjustment module 26 is connected to the output current reference value of the fourth port The output of the third PI adjustment module 26 is the small signal phase shift angle between the first port and the fourth port. And connected to the input of the feedforward decoupling network module 22; the input of the Newton-Raphson calculation module 21 is connected to the voltage V1 at both ends of the first port, the voltage V2 at both ends of the second port, the voltage V3 at both ends of the third port, and the voltage V4 at both ends of the fourth port. The output of the Newton-Raphson calculation module 21 is an approximate solution of the steady-state operating point phase shift angle between the first port and the second port. , the approximate solution of the phase shift angle at the steady-state operating point between the first port and the third port , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port And connected to the input of the feedforward decoupling network module 22; the output of the feedforward decoupling network module 22 is the phase shift angle between the first port and the second port after decoupling , the phase shift angle between the first port and the third port after decoupling , the phase shift angle between the first port and the fourth port after decoupling The output of the feedforward decoupling network module 22 is superimposed with the output of the Newton-Raphson calculation module 21 and connected to the input of the driving module 23. The output of the driving module 23 is connected to the four-active bridge converter 1 to drive the switches of the four-active bridge converter and control the operation of the four-active bridge converter.

[0160] More specifically, the first PI regulation module 24, the second PI regulation module 25, and the third PI regulation module 26 perform PI regulation by subtracting the output current reference value from the sampled output current to obtain the small-signal phase shift angle of the PI-regulated output. The Newton-Raphson calculation module 21 uses the Newton-Raphson iteration method to calculate an approximate solution for the steady-state operating point phase shift angle in real time. The feedforward decoupling network module 22 uses the approximate solution for the steady-state operating point phase shift angle calculated by the Newton-Raphson iteration method to calculate the small-signal function model between the control variables and output variables of the four-active-bridge converter in real time. It also calculates the feedforward decoupling network in real time, and obtains the decoupled small-signal phase shift angle based on the small-signal phase shift angle of the PI-regulated output. The drive module 23 generates a pulse-width modulation (PWM) signal based on the sum of the decoupled small-signal phase shift angle and the approximate solution for the steady-state operating point phase shift angle calculated by the Newton-Raphson iteration method to drive the switches of the four-active-bridge converter, thereby controlling the operation of the four-active-bridge converter.

[0161] Furthermore, the control system 2 of the four-active-bridge converter of the present invention further includes a plurality of low-pass filter modules 27, the inputs of the low-pass filter modules 27 being respectively connected to the output current I2 of the second port, the output current I3 of the third port, and the output current I4 of the fourth port. After the sampled output current is low-pass filtered, the difference is calculated with the output current reference value.

[0162] Furthermore, the control system 2 of the quad-active bridge converter of the present invention also includes multiple zero-order holding modules 28, the inputs of the zero-order holding modules 28 are respectively connected to the outputs of the corresponding low-pass filtering modules 28, and the output current after low-pass filtering is converted from a discrete signal to a continuous signal, and then the signal is subtracted from the output current reference value.

[0163] The present invention also provides a four-active-bridge converter, applying the above-mentioned control method of the four-active-bridge converter.

[0164] Furthermore, simulation verification was conducted on the PLECS simulation platform and experimental verification was conducted on the PLECS RT-Box semi-physical simulation platform to compare the dynamic response performance of the system during load switching between the traditional closed-loop control method without adding decoupling control strategy and the method of the present invention. The switching frequency of the PLECS simulation platform was set to 50kHz. Due to the limitation of hardware resources, the switching frequency of the PLECS RT-Box semi-physical simulation platform was set to 1kHz. Among them, the current dynamic response simulation waveforms of the traditional method and the method of the present invention are shown as follows: Figure 7 As shown, the power dynamic response simulation waveforms of the traditional method and the method of the present invention are as follows Figure 8As shown in the figure, at 0.2s, the output current I2 of the second port changes from 100A to 50A, and the port power changes from full load to half load. Compared with the traditional method, the dynamic response time of the method of the present invention is significantly shortened, and the current and power fluctuations of the third and fourth ports are significantly smaller than those of the traditional method, which effectively suppresses the power coupling phenomenon caused by the four ports of the four active bridge converter sharing a multi-winding transformer core. Figure 9 、 Figure 10 、 Figure 11 This is the waveform measured by the oscilloscope in the PLECS RT-Box hardware-in-the-loop simulation platform, where: Figure 9 is the waveform of the inductor current change when the output current I2 of the second port in the method of the present invention changes from 20A to 50A, Figure 10 This is the dynamic response curve of the output current of each port when the output current I2 of the second port changes from 20A to 50A in the traditional method. Figure 11 The figure shows the dynamic response curve of the output current of each port when the output current I2 of the second port changes from 20A to 50A in the method of the present invention. Compared with the traditional method, the method of the present invention can significantly suppress the power coupling phenomenon, and the output current fluctuation of the third and fourth ports is significantly reduced. The dynamic time is also greatly shortened. In addition, the control method used has a small amount of calculation and is easy to implement.

[0165] In summary, the proposed quad-active-bridge converter, control method, and control system enable real-time decoupling control within a closed-loop controller without requiring extensive and complex calculations and adjustments. This method effectively suppresses inter-port power coupling during power switching, significantly improving the system's dynamic response. Furthermore, simulation experiments validated the effectiveness of this method and demonstrated superior power coupling suppression compared to existing methods.

[0166] Although the present invention has been disclosed above with reference to the embodiments, they are not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope of protection defined by the claims.

Claims

1. A control method for a quad active bridge converter, characterized in that: include, Step S1, sampling the output current; Step S2, taking the difference between the output current reference value and the sampled output current, performing PI regulation to obtain a small signal phase shift angle of the PI regulated output; The approximate solution of the phase shift angle at the steady-state operating point is calculated in real time using the sampled output current and parameter information of the four-active-bridge converter via the Newton-Raphson iteration method. Step S3, using the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to calculate in real time the small signal function model between the control variables and the output variables of the four-active bridge converter, and to calculate in real time the feedforward decoupling network; Step S4, sending the small signal phase shift angle output by PI regulation into the feedforward decoupling network to obtain the decoupled small signal phase shift angle, and adding it to the approximate solution of the steady-state operating point phase shift angle calculated by the Newton-Raphson iterative method to obtain the value of each phase shift angle under single phase shift modulation; In step S2, the output current reference value of the second port is The output current of the second port The small signal phase shift angle between the first port and the second port of the PI regulation output is obtained by PI regulation. ; Set the output current reference value of the third port The output current of the third port The small signal phase shift angle between the first port and the third port of the PI regulation output is obtained by PI regulation. ; Set the output current reference value of the fourth port The output current of the fourth port The small signal phase shift angle between the first port and the fourth port of the PI regulation output is obtained by PI regulation. ; In step S2, the approximate solution of the steady-state operating point phase shift angle is calculated in real time using the Newton-Raphson iteration method. The formula is as follows: ， in, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the Nth iteration, is the approximate solution matrix of the phase shift angle of the steady-state operating point of the N+1th iteration, is a basic real-valued function, is the Jacobian matrix; The approximate solution matrix of the phase shift angle at the steady-state operating point of the Nth iteration The expression is as follows: ， in, is the approximate solution of the steady-state operating point phase shift angle between the first port and the second port, is the approximate solution of the steady-state operating point phase shift angle between the first port and the third port, is the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port; The four-active bridge converter includes a first bridge module, a second bridge module, a third bridge module, a fourth bridge module, and a transformer module. The first end of the first bridge module is connected in parallel to the first port, the second end of the first bridge module is connected in parallel to the first end of the transformer module, the first end of the second bridge module is connected in parallel to the second port, the second end of the second bridge module is connected in parallel to the second end of the transformer module, the first end of the third bridge module is connected in parallel to the third port, the second end of the third bridge module is connected in parallel to the third end of the transformer module, the first end of the fourth bridge module is connected in parallel to the fourth port, and the second end of the fourth bridge module is connected in parallel to the fourth end of the transformer module.

2. A control method for a quad active bridge converter according to claim 1, characterized in that: Basic real-valued functions The expression is as follows: in, is the target power of the second port, is the target power of the third port, is the target power of the fourth port, is the actual iterative power of the second port, is the actual iterative power of the third port, is the actual iterative power of the fourth port.

3. A control method for a quad active bridge converter as claimed in claim 2, characterized in that: Jacobian matrix The expression is: 。 4. A control method for a quad active bridge converter as claimed in claim 3, characterized in that: In step S3, the small signal function model between the control variables and the output variables of the four active bridge converter is: ， in, is the small signal value of the output current of the second port, is the small signal value of the output current of the third port, is the small signal value of the output current of the fourth port, is the phase shift angle between the first port and the second port after decoupling, is the phase shift angle between the first port and the third port after decoupling, is the phase shift angle between the first port and the fourth port after decoupling; Parameter G in the G matrix ij Expressed as: Among them, V p is the voltage across the p-th port, L ip is the power equivalent inductance between the i-th port and the p-th port, is the phase shift angle of the steady-state operating point of the i-th port, is the phase shift angle of the steady-state operating point of the p-th port, is the phase shift angle of the steady-state operating point of the jth port, V j is the voltage across the j-th port, L ij is the power equivalent inductance between the i-th port and the j-th port.

5. A control method for a quad active bridge converter as claimed in claim 4, characterized in that: The expression of the feedforward decoupling network D is: ， in, is the small signal phase shift angle between the first and second ports of the PI regulation output, is the small signal phase shift angle between the first and third ports of the PI regulation output, is the small signal phase shift angle between the first and fourth ports of the PI regulation output, is the phase shift angle between the first port and the second port after decoupling, is the phase shift angle between the first port and the third port after decoupling, is the phase shift angle between the first port and the fourth port after decoupling; The expressions of the parameters in the feedforward decoupling network D are: 。 6. A control method for a quad active bridge converter as claimed in claim 5, characterized in that: In step S4, the small signal phase shift angle between the first port and the second port of the PI regulation output is set to , the small signal phase shift angle between the first port and the third port of the PI regulation output , the small signal phase shift angle between the first port and the fourth port of the PI regulation output In the input feedforward decoupling network, the phase shift angle between the first port and the second port after decoupling is calculated. , the phase shift angle between the first port and the third port after decoupling , the phase shift angle between the first port and the fourth port after decoupling , respectively, and the approximate solution of the steady-state operating point phase shift angle between the first port and the second port , the approximate solution of the phase shift angle at the steady-state operating point between the first port and the third port , the approximate solution of the steady-state operating point phase shift angle between the first port and the fourth port Superposition, get the phase shift angle between the first port and the second port under single phase shift modulation , Phase shift angle between the first port and the third port , Phase shift angle between the first port and the fourth port ; The relationship between the phase shift angles of different ports and the phase shift angles between ports is as follows: ， in, is the first port phase shift angle, is the second port phase shift angle, is the third port phase shift angle, is the fourth port phase shift angle.

7. A control system for a quad-active bridge converter, characterized in that: A control method for a quad-active bridge converter according to any one of claims 1 to 6 is applied, wherein the control system of the quad-active bridge converter includes a Newton-Raphson calculation module, a feedforward decoupling network module, a drive module, a first PI adjustment module, a second PI adjustment module, and a third PI adjustment module, wherein an input of the first PI adjustment module is connected to a difference between an output current reference value of the second port and an output current of the second port, and an output of the first PI adjustment module is connected to an input of the feedforward decoupling network module; The input of the second PI adjustment module is connected to the difference between the output current reference value of the third port and the output current of the third port, and the output of the second PI adjustment module is connected to the input of the feedforward decoupling network module; The input of the third PI adjustment module is connected to the difference between the output current reference value of the fourth port and the output current of the fourth port, and the output of the third PI adjustment module is connected to the input of the feedforward decoupling network module; the input of the Newton-Raphson calculation module is connected to the voltage at both ends of each port, and the output of the Newton-Raphson calculation module is connected to the input of the feedforward decoupling network module; the output of the feedforward decoupling network module is superimposed with the output of the Newton-Raphson calculation module and connected to the input of the drive module, and the output of the drive module is connected to the four active bridge converters.

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