Dual active bridge converter arrangement of even modules, zero common mode modulation method, arrangement and system

Abstract

The application discloses a dual active bridge converter device of even modules, a zero common-mode modulation method, device and system, belongs to the common-mode interference suppression technical field, the device includes: 2N dual active bridge converters, and the primary side dual active bridge in each dual active converter is connected with the isolation transformer through symmetrical coupling phase-shift inductance;The zero common-mode modulation method comprises the following steps: divide the dual active bridge converter into N groups, for each group, under the condition of meeting the output power requirement, the switching drive signals of bridge arms A1 and A2 are complementary, and the inner phase-shift ratio between A1 and B1 is equal to the inner phase-shift ratio between A2 and B2;Under the condition that the switching drive signals of C1 and D1 are complementary, and the switching drive signals of C2 and D2 are complementary, the outer phase-shift ratio between A1 and C1 and the outer phase-shift ratio between A2 and C2 are adjusted, so that the power of the two converters is equal. The application can effectively solve the common-mode interference suppression problem of the dual active bridge converter device of multiple modules.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of common mode interference suppression, and more particularly, to an even module dual active bridge converter device, a zero common mode modulation method, device and system. BACKGROUND

[0002] Dual active bridge converters have a wide range of applications in energy storage systems, DC microgrids, electric vehicles, and other fields due to their high efficiency, high power density, electrical isolation, bidirectional energy transfer, and ease of achieving zero voltage switching. Dual active bridge converters have modular characteristics, and different series-parallel forms are used depending on the application: series input series output systems are suitable for high input and output voltages; series input parallel output systems are suitable for high input and low output voltages; parallel input parallel output systems are suitable for low output voltage and high current; and parallel input series output systems are suitable for low input voltage and high output voltage. By designing the series-parallel form of the dual active bridge converter, device stress can be effectively reduced, electrical and thermal design can be simplified, and system reliability can be improved.

[0003] However, as power density and efficiency increase, the electromagnetic interference problem of dual active bridge converters becomes more serious. On the one hand, with the development of wide-bandgap semiconductors, silicon carbide devices are gradually replacing silicon devices, and switching frequencies are becoming higher and higher, leading to worsening noise sources of electromagnetic interference. On the other hand, dual active bridge converters use high-frequency transformers for electrical isolation. The compact winding structure of the high-frequency transformer results in a large parasitic capacitance between the windings, which worsens the interference conduction path and produces serious common mode interference. Common mode interference can propagate along the cable, worsening system reliability.

[0004] In order to improve electromagnetic compatibility and meet relevant standards (such as DO160 or MIL-STD-461G), common-mode interference of a dual active bridge converter must be suppressed. The common-mode interference suppression methods are mainly divided into interference path optimization and interference source optimization. The interference path optimization is divided into three categories: electromagnetic interference filter, shielding and leakage current path optimization. The passive filter is the most widely used technology in practical applications, however, the passive filter is large in size and heavy in weight, which reduces the power density of the whole system; the active filter adopts an integrated amplification circuit to sample the interference signal for active compensation, which can effectively improve the power density, but the high-frequency suppression effect is not good. Shielding is a common technique to reduce transformer common-mode interference, but shielding will inevitably increase transformer loss and cost. In addition, the common-mode interference can also be improved by optimizing the topology structure, and zero common-mode can be realized by coupling symmetric inductance, but this method is only applicable to single-phase shift modulation, which limits the modulation degree of freedom. The interference source optimization is mainly divided into spread spectrum modulation and pulse cancellation modulation. Spread spectrum modulation disperses narrowband harmonic energy into a wider frequency spectrum range by periodically adjusting the switching frequency, thereby reducing electromagnetic interference spikes, but the power fluctuation caused by the change of the switching frequency makes the control algorithm more complex. Pulse cancellation realizes common-mode voltage cancellation by optimizing the switching pulse timing, but pulse cancellation puts higher requirements on the circuit topology and is only applicable to multi-module systems. In addition, pulse cancellation requires complementary switching signals for the corresponding bridge arms, which leads to power coupling between different modules, making it difficult to achieve power balance. Power imbalance will lead to overvoltage and overcurrent during part of the period, affecting the safe and stable operation of the system. SUMMARY

[0005] In view of the defects of the prior art and the improvement needs, the present application provides an even module dual active bridge converter device, a zero common-mode modulation method, device and system, which aims to effectively solve the common-mode interference suppression problem of the multi-module dual active bridge converter device.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present application, an even module dual active bridge converter device is provided, comprising: 2N dual active bridge converters;

[0007] A symmetrically coupled phase-shift inductance is arranged between the original side dual active bridge and the isolation transformer in the dual active bridge converter;

[0008] The symmetrically coupled phase-shift inductance includes two inductances, which are arranged between the midpoint of the two bridge arms of the original side dual active bridge and the isolation transformer; the windings of the two inductances are opposite in name and equal in self-inductance, and the series equivalent inductance is L ph ;

[0009] Wherein, N is a positive integer, L ph is a preset original side and secondary side phase-shift inductance value.

[0010] According to another aspect of the present invention, there is provided a zero common mode modulation method for the dual active bridge converter device of the even-numbered modules, comprising:

[0011] The 2N dual-active bridge converters in the dual-active bridge converter device of the even-numbered modules are evenly divided into N groups of converters; in each group of converters, the two dual-active bridge converters are respectively denoted as a first converter and a second converter, the two bridge arms of the primary side of the first converter are respectively denoted as A1 and B1, and the two bridge arms of the secondary side are respectively denoted as C1 and D1; the two bridge arms of the primary side of the second converter are respectively denoted as A2 and B2, and the two bridge arms of the secondary side are respectively denoted as C2 and D2;

[0012] For each group of converters, power balanced zero common mode modulation is performed respectively to achieve zero common mode modulation of the dual active bridge converter device with an even number of modules;

[0013] Power-balanced zero-common-mode modulation includes:

[0014] Under the condition of meeting the output power requirement, the switch drive signals of control bridge arms A1 and A2 are complementary, and the internal shift between bridge arms A1 and B1 is controlled to be D 1_1 Compared with the inward shift between bridge arms A2 and B2, D 1_2 Equal; Under the condition that the switch drive signals of bridge arms C1 and D1 are complementary, and the switch drive signals of bridge arms C2 and D2 are complementary, the outward shift between bridge arms A1 and C1 is adjusted to be D 0_1 Compared with the outward shift between bridge arms A2 and C2, D 0_2 , so that the power of the first converter and the second converter are equal.

[0015] Furthermore, the inward shift is compared to D 1_1 and D 1_2 , and outward shift compared to D 0_1 and D 0_2 Methods of determination include:

[0016] Determine the output power per unit value P * , and calculate the voltage conversion ratio k;

[0017] Find P from the pre-established optimal phase shift lookup table * The optimal phase-shift lookup table records all possible combinations of inward and outward phase shifts that meet preset conditions for each per-unit output power value and voltage conversion ratio. The preset conditions include the relationship between the per-unit output power value and the inward and outward phase shifts, soft switching boundary conditions, and whether the inward phase shift D1 can suppress DC-side ripple.

[0018] Compare the inward shift to D 1_1 and D 1_2 All are assigned the value of D1;

[0019] Determine the control error ΔD0 of the outward shift phase and obtain the output power per unit value P * The sign of the partial derivative relative to the current outward shift of the first converter, and the per-unit output power value P * The signs of the partial derivatives relative to the current outward shift of the second transformer are denoted as the first sign and the second sign respectively;

[0020] Assign the first sign to ΔD0 to get ΔD0', and compare the outward shift to D 0_1 Assign the value D0-ΔD0'; assign the second sign to ΔD0 to get ΔD0", and compare the outward shift to D 0_2 Assign the value to D0+ΔD0".

[0021] Furthermore, the optimal phase shift lookup table is established by:

[0022] Select the output power per unit value P in the range of (0,1) * , and select the voltage conversion ratio k in the range of (0,1.5) to obtain multiple operating points; each operating point corresponds to a combination of output power per unit value and voltage conversion ratio;

[0023] For each working point (P * ,k), solve the output power per unit value P * Compared with the size relationship between the inner shift D1 and the outer shift D0, the inner shift and outer shift are combined to obtain the working point (P * ,k) The corresponding shift ratio set U1;

[0024] From the working point (P * ,k) in the corresponding shift ratio set U1, select the inner shift ratio and outer shift ratio combination that meet the soft switching boundary conditions, and get the working point (P * ,k) corresponds to the shift set U2;

[0025] From the working point (P * ,k) in the corresponding shift ratio set U2, select the inner shift ratio and outer shift ratio combination that satisfies D1=l / m, and obtain the working point (P * ,k) corresponds to the optimal shift ratio set;

[0026] The optimal phase shift ratio set corresponding to each working point is recorded in the optimal phase shift ratio lookup table to complete the establishment of the optimal phase shift lookup table;

[0027] Wherein, l is a positive odd number, and m is the multiple or order of the target harmonic frequency relative to the switching frequency.

[0028] Further, before recording the optimal phase shift ratio set corresponding to each working point to the optimal phase shift ratio lookup table, the method further comprises:

[0029] For each working point, the inner phase shift ratio and the outer phase shift ratio combination with the minimum inner phase shift ratio value in the optimal phase shift ratio set corresponding to the working point are determined, and the remaining inner phase shift ratio and outer phase shift ratio combinations are deleted from the optimal phase shift ratio set.

[0030] Further, the output power reference P * is determined, comprising:

[0031] The output voltage command value U o * is subtracted from the output voltage U o of the first converter or the second converter to perform PI control, so as to obtain the output power reference P * .

[0032] Further, the control error ΔD0 of the outer phase shift ratio is determined, comprising:

[0033] If the inputs of the first converter and the second converter are in series, the input voltage command value U i_ave is subtracted from the input voltage U i1 of the first converter to perform PI control, so as to obtain the control error ΔD0 of the outer phase shift ratio.

[0034] If the inputs of the first converter and the second converter are in parallel and the outputs are in parallel, the input current average value I i_ave is subtracted from the input current I i1 of the first converter to perform PI control, so as to obtain the control error ΔD0 of the outer phase shift ratio, or the output current average value I o_ave is subtracted from the output current I o1 of the first converter to perform PI control, so as to obtain the control error ΔD0 of the outer phase shift ratio.

[0035] If the inputs of the first converter and the second converter are in parallel and the outputs are in series, the input current average value I i_ave is subtracted from the input current I i1 of the first converter to perform PI control, so as to obtain the control error ΔD0 of the outer phase shift ratio, or the output voltage average value U o_ave is subtracted from the output voltage U o1 of the first converter to perform PI control, so as to obtain the control error ΔD0 of the outer phase shift ratio.

[0036] According to still another aspect of the present application, there is provided a zero common mode modulation device of the dual active bridge converter device of the even module, comprising: a control module and N modulation modules.

[0037] A control module is configured to evenly divide 2N dual-active bridge converters in the dual-active bridge converter device of the even-numbered modules into N groups of converters; in each group of converters, the two dual-active bridge converters are respectively denoted as a first converter and a second converter, the two bridge arms of the primary side of the first converter are respectively denoted as A1 and B1, and the two bridge arms of the secondary side are respectively denoted as C1 and D1, and the two bridge arms of the primary side of the second converter are respectively denoted as A2 and B2, and the two bridge arms of the secondary side are respectively denoted as C2 and D2;

[0038] N modulation modules are respectively used to perform power-balanced zero common mode modulation on N groups of converters, so as to realize zero common mode modulation of a dual active bridge converter device with an even number of modules;

[0039] The modulation module includes:

[0040] The first control loop is used to determine the output power per unit value P * , and calculate the voltage conversion ratio k;

[0041] The table lookup unit has an input terminal connected to the output terminal of the first control loop and is used to look up P from a pre-established optimal phase shift lookup table. * The optimal phase shift lookup table records all possible combinations of inward and outward phase shifts that meet the preset conditions for each output power per unit value and voltage conversion ratio. The preset conditions include the relationship between the output power per unit value and the inward and outward phase shifts, soft switching boundary conditions, and the ability to suppress DC side ripple.

[0042] The second control loop is used to determine the control error ΔD0 of the outward shift phase and obtain the output power per unit value P * The sign of the partial derivative relative to the current outward shift of the first converter, and the per-unit output power value P * The signs of the partial derivatives relative to the current outward shift of the second transformer are denoted as the first sign and the second sign respectively;

[0043] and a shift ratio determination unit, a first input terminal of which is connected to the output terminal of the table lookup unit, and a second input terminal of which is connected to the output terminal of the second control loop, and is configured to perform the following operations:

[0044] Compare the inward shift between bridge arms A1 and B1 to D 1_1 Compared with the inward shift between bridge arms A2 and B2, D 1_2 All are assigned the value of D1;

[0045] Assign the first sign to ΔD0 to get ΔD0', and compare the outward displacement between bridge arms A1 and C1 to D 0_1 Assign the value to D0-ΔD0';

[0046] Assign the second sign to ΔD0, and get ΔD0", and compare the outward displacement between bridge arms A2 and C2 with D 0_2 Assign the value to D0+ΔD0".

[0047] According to another aspect of the present invention, a dual active bridge converter system with an even number of modules is provided, comprising: the dual active bridge converter device with an even number of modules provided by the present invention, the zero common mode modulation device provided by the present invention, and a driver;

[0048] The driver is used to generate a switch driving signal for each converter according to the inner shift phase ratio and the outer shift phase ratio determined by the zero common mode modulation device, and apply the signal to the corresponding converter.

[0049] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0050] (1) The present invention provides a dual-active bridge converter device with an even number of modules, wherein the primary full bridge in each dual-active bridge converter is connected between a symmetrically coupled phase-shifting inductor and an isolation transformer, and the two inductor windings in the symmetrically coupled phase-shifting inductor are respectively arranged between the midpoints of the two bridge arms of the primary dual-active bridge and the isolation transformer, and the self-inductance of the two inductor windings is equal and the series equivalent inductance is L ph , thus ensuring that the inductance of the coupled phase-shifting inductor is equal to the preset phase-shifting inductance, without affecting power output. Furthermore, because the two inductor windings have opposite ends, the equivalent voltage sources of the two inductor windings complement each other. For the common-mode loop, the common-mode excitations generated by the two inductor windings cancel each other out, eliminating the inductor's excitation of the common-mode voltage and effectively reducing the common-mode interference of the dual-active bridge converter. Furthermore, the dual-active bridge converters in the present invention have an even number of dual-active bridge converters, allowing for modulation by grouping them in pairs, achieving zero common-mode modulation while ensuring power balance.

[0051] (2) The zero common mode modulation method provided by the present invention divides the dual active bridge converters in the dual active bridge converter device of the even number of modules into a group of two. For each group of converters, under the condition of meeting the output power requirement, the switch drive signals of the bridge arms A1 and A2 are controlled to be complementary, and the internal shift ratio D between the bridge arms A1 and B1 is controlled to be 1_1 Compared with the inward shift between bridge arms A2 and B2, D 1_2 Equal, and control the switch drive signals of bridge arms C1 and D1 to be complementary, and the switch drive signals of bridge arms C2 and D2 to be complementary, thereby enabling both converters in the group to achieve zero common mode modulation. On this basis, the outward shift ratio D between bridge arms A1 and C1 is adjusted. 0_1 Compared with the outward shift between bridge arms A2 and C2, D 0_2 , making the power of the first converter and the second converter equal, thereby achieving power balance while realizing zero common mode modulation.

[0052] (3) The zero common mode modulation method provided by the application, in the preferred scheme thereof, a combination of inner phase shift ratio and outer phase shift ratio corresponding to each working point, i.e. output power unit and voltage conversion ratio, is established in advance, and these combinations of inner phase shift ratio and outer phase shift ratio satisfy the size relationship between output power unit and inner phase shift ratio and outer phase shift ratio, the soft switching boundary condition, and the setting of inner phase shift ratio D1 can suppress the ripple on the DC side; in the actual modulation process, after the output power unit P * and voltage conversion ratio k are determined, the optimal combination of inner phase shift ratio and outer phase shift ratio is determined by table lookup, and the inner phase shift ratio and outer phase shift ratio of each converter in the group are determined based on this, so that power balance can be achieved while realizing zero common mode modulation, and the ripple on the DC side can be effectively suppressed.

[0053] (4) The zero common mode modulation method provided by the application, in the preferred scheme thereof, when establishing the optimal phase shift lookup table, only the combination of inner phase shift ratio and outer phase shift ratio with the most obvious ripple suppression effect on the DC side is retained, so that the ripple on the DC side can be suppressed to the greatest extent during phase shift modulation. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 It is a schematic diagram of the existing dual active bridge converter topology;

[0055] Figure 2 It is a schematic diagram of the dual active bridge converter topology provided by the embodiment of the application;

[0056] Figure 3 It is a schematic diagram of the extended phase shift modulation of the existing dual active bridge converter;

[0057] Figure 4 It is a schematic diagram of the coordinated modulation of a group of converters composed of two dual active bridge converters according to the embodiment of the application;

[0058] Figure 5 It is a schematic diagram of the zero common mode modulation method and device provided by the embodiment;

[0059] Figure 6 It is a schematic diagram of the topology with two dual active bridge converters provided by the application. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0061] In the present application, the terms "first", "second", and the like (if any) in the present application and the accompanying drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0062] Before detailing the technical solutions of the present application, the topology structure of the dual active bridge converter is briefly described first. Figure 1 The traditional dual active bridge converter is shown, which is connected by a single-phase shift inductance Lph and a high-frequency isolation transformer T connected to the primary and secondary sides of two full bridges, each full bridge contains two bridge arms, a total of four bridge arms, respectively denoted as bridge arm A, bridge arm B, bridge arm C and bridge arm D, and the voltage transformation ratio of the secondary side of the transformer to the primary side is n=N s / N p . Each bridge arm contains 2 switching tubes, the driving signals of the upper and lower switching tubes of bridge arm A are denoted as S A1 and S A2 , the driving signals of the upper and lower switching tubes of bridge arm B are denoted as S B1 and S B2 , and so on. U i and U o represent the DC bus voltage of the primary side and the secondary side, that is, the input voltage and the output voltage.

[0063] However, with the improvement of power density and efficiency, the electromagnetic interference problem of the dual active bridge converter becomes more serious. On the one hand, with the development of wide band gap semiconductors, silicon carbide devices gradually replace silicon devices, and the switching frequency is getting higher and higher, which worsens the noise source of electromagnetic interference. On the other hand, the dual active bridge converter uses a high-frequency transformer to realize electrical isolation. The compact winding structure of the high-frequency transformer results in a large parasitic capacitance between the windings, which worsens the interference conduction path and produces serious common-mode interference. Common-mode interference can propagate along the cable and worsen system reliability.

[0064] The traditional dual active bridge converter only sets a single-phase shift inductance, which can excite the common-mode voltage and further worsen the common-mode interference of the dual active bridge converter.

[0065] In view of the above problems, the topology structure of the dual active bridge converter is improved in the present application, and a symmetric coupled inductor is used instead of the conventional single-sided asymmetric phase shift inductance. Without affecting the power transmission of the dual active bridge converter, the excitation of the inductance to the common-mode voltage is eliminated, and the zero common-mode interference condition of the dual active bridge converter is improved.

[0066] Multi-module can effectively reduce the electrical stress of the device, simplify the electrical design and heat dissipation design, improve the reliability, and can be flexibly applied to various occasions including direct current power grid, multi-electric aircraft, rail transit, etc. In the device provided by the application, the number of dual active bridge converters is even, and modulation can be performed in a two-by-two grouping manner to achieve zero common-mode modulation while ensuring power balance.

[0067] On the basis of the above topology optimization, the phase-shift modulation of the dual active bridge converter is further optimized in the application to achieve zero common-mode modulation while retaining the ability of power balance control. On this basis, the phase-shift ratio is further optimized in the application to further suppress the DC side ripple.

[0068] The following is an embodiment.

[0069] Embodiment 1:

[0070] An even-module dual active bridge converter device, comprising: 2N dual active bridge converters;

[0071] As shown in Figure 2 , in the embodiment, a symmetrically coupled phase-shift inductor is arranged between the primary side dual active bridge and the isolation transformer in the dual active bridge converter.

[0072] The symmetrically coupled phase-shift inductor includes two inductors arranged between the two bridge arm midpoints of the primary side dual active bridge and the isolation transformer. The windings of the two inductors are opposite in name, the self-inductance of the two inductors is equal, and the series equivalent inductance of the two inductors is equal to L ph .

[0073] Wherein, L ph is a preset primary and secondary side phase-shift inductor value; N is a positive integer, which can be set according to the actual application occasion in actual application.

[0074] In the embodiment, the single-sided asymmetric phase-shift inductor in the traditional dual active bridge converter is replaced by a symmetrically coupled phase-shift inductor, which includes two inductors arranged between the two bridge arm midpoints of the primary side dual active bridge and the isolation transformer. The windings of the two inductors are opposite in name, the self-inductance of the two inductors is equal, and the series equivalent inductance of the two inductors is equal to L phTherefore, the inductance value of the symmetrically coupled phase-shift inductor is the same as that of the unilateral asymmetrical phase-shift inductor, which does not affect the power transmission of the dual-active bridge converter. At the same time, the equivalent voltage sources of the two inductor windings are complementary. For the common-mode loop, the common-mode excitations generated by the two inductor windings cancel each other out, thereby eliminating the excitation of the common-mode voltage by the inductor, effectively reducing the common-mode interference of the dual-active bridge converter.

[0075] The even number (2N) dual active bridge converters in this embodiment can adopt different series and parallel forms according to different application scenarios. Since the common mode interference of each dual active bridge converter is improved, the zero common mode interference of the entire device is also improved.

[0076] Example 2:

[0077] A zero common mode modulation method is used to implement zero common mode modulation of the dual active bridge converter device of the even-numbered modules provided in the first embodiment.

[0078] According to the traditional phase-shift modulation method of the dual-active bridge converter, for the two bridge arms A and B included in the primary dual-active bridge and the two bridge arms C and D included in the secondary dual-active bridge, the switch drive signal of each bridge arm is a pulse signal with a 50% duty cycle. The switch drive signal of bridge arm A is used as the reference signal. The phase shift between the switch drive signals of bridge arms A and B is defined as the inner phase shift D1, and the phase shift between the switch drive signals of bridge arms A and C is defined as the outer phase shift D0. The drive signals of bridge arms D and C are complementary. Based on the different relationships between the inner phase shift D1 and the outer phase shift D0, the dual-active bridge converter has two operating modes. In the two operating modes, the drive signal S of the upper switch tubes of bridge arms A, B, C, and D is A1 、S B1 、S C1 and S D1 , the voltage between the midpoints of bridge arms A and B is V AB , the voltage between the midpoints of bridge arms C and D is V CD , and the inductor current I L like Figure 3 shown.

[0079] Through this phase-shift modulation method, zero common-mode modulation can be achieved for a single dual-active bridge converter. However, for a topology containing multiple dual-active bridge converters, since this phase-shift modulation method requires the switching signals of the corresponding bridge arms to be complementary, this will lead to power coupling between different modules, making power balance difficult to achieve.

[0080] This embodiment aims to achieve zero common mode modulation while retaining the control capability of power balancing. This embodiment is proposed based on the following findings:

[0081] For the topology composed of two dual active converters, two bridge arms of the primary side in one of the converters are respectively denoted as A1 and B1, two bridge arms of the secondary side are respectively denoted as C1 and D1, two bridge arms of the primary side in the other converter are respectively denoted as A2 and B2, and two bridge arms of the secondary side are respectively denoted as C2 and D2. In the case that the switching driving signals and the phase shift ratio within a single dual active bridge satisfy the above requirements, the switching driving signals of the bridge arms A1 and A2 are complementary, the inner phase shift ratio between the bridge arms A1 and B1 is D 1_1 , and the outer phase shift ratio between the bridge arms A1 and C1 is D 1_2 . The same is true for the bridge arms A2 and B2, and the bridge arms A2 and C2. Figure 4 As shown in the formula, S A1_1 and S A1_2 respectively represent the driving signals of the upper switching tubes of the bridge arms A1 and A2, S B1_1 and S B1_2 respectively represent the driving signals of the upper switching tubes of the bridge arms B1 and B2, S C1_1 and S C1_2 respectively represent the driving signals of the upper switching tubes of the bridge arms C1 and C2, S D1_1 and S D1_2 respectively represent the driving signals of the upper switching tubes of the bridge arms D1 and D2, T hs represents half of the switching period, T hs = 1 / 2 / f s (f s represents the switching frequency). At this time, by adjusting the outer phase shift ratio D 0_1 between the bridge arms A1 and C1 and the outer phase shift ratio D 0_2 between the bridge arms A2 and C2, the power of the two converters can still be freely adjusted, and the ability of power balance control is retained.

[0082] Based on the above finding, the zero common mode modulation method provided by the embodiment specifically includes the following steps.

[0083] 2N dual active bridge converter devices in an even number of modules of dual active bridge converter devices are evenly divided into N groups of converters. In each group of converters, two dual active bridge converters are respectively denoted as a first converter and a second converter, two bridge arms of the primary side in the first converter are respectively denoted as A1 and B1, two bridge arms of the secondary side are respectively denoted as C1 and D1, two bridge arms of the primary side in the second converter are respectively denoted as A2 and B2, and two bridge arms of the secondary side are respectively denoted as C2 and D2.

[0084] For each group of converters, zero common mode modulation for power balance is performed to realize zero common mode modulation of the even number of modules of dual active bridge converters.

[0085] The zero common mode modulation for power balance includes the following steps.

[0086] In the case of meeting the output power requirement, the switching drive signals of the bridge arms A1 and A2 are complementary, and the inner phase shift between the bridge arms A1 and B1 is controlled to be equal to D 1_1 The inner phase shift between the bridge arms A2 and B2 is controlled to be equal to D 1_2 In the case of meeting the switching drive signals of the bridge arms C1 and D1 being complementary, and the switching drive signals of the bridge arms C2 and D2 being complementary, the outer phase shift between the bridge arms A1 and C1 is adjusted to be equal to D 0_1 The outer phase shift between the bridge arms A2 and C2 is adjusted to be equal to D 0_2 The power of the first converter and the second converter is equalized.

[0087] The embodiment divides the double active converters in the device into two groups, respectively performs the zero common-mode modulation of the power balance of each group of converters, realizes the zero common-mode modulation of each converter and the equalization of the power of the converters in the group, and thus can realize the zero common-mode modulation while ensuring the equalization of the power of each converter in the double active bridge converter device of the entire even module.

[0088] For each double active bridge converter, according to the relationship between the inner phase shift D1 and the outer phase shift D0, the double active bridge converter has two working modes, when D1 < D0, it is recorded as mode 1; when D0≤D1≤2D0, it is recorded as mode 2. In the two working modes, the output power per unit P * The inner phase shift D1 and the outer phase shift D2 satisfy:

[0089]

[0090] In the two working modes, the soft switching boundary conditions are as follows:

[0091] Mode 1:

[0092]

[0093] Mode 2:

[0094]

[0095] Wherein, f s Indicates the switching frequency; k indicates the voltage conversion ratio, that is, the ratio of the output voltage to the input voltage, which is calculated through the input voltage command, so as to reduce the influence of the input voltage fluctuation on the control. The calculation expression is:

[0096]

[0097] It is easy to understand that the above conditions need to be met at the same time when performing the above power balance zero common mode modulation. Generally, there are multiple combinations of inner phase shift ratio D1 and outer phase shift ratio D2 that can meet the above conditions at the same time, and the direct current side ripple can be further suppressed by optimizing the inner phase shift ratio D1. Specifically, setting D1 = l / m can suppress the direct current side ripple, where m is the multiple or order of the target harmonic frequency relative to the switching frequency, which can be obtained by modeling or measurement in actual application, and the value is an odd number; and l is an odd number, i.e. l = 1, 3, 5, 7, ….

[0098] In order to further suppress the direct current side ripple and optimize the performance of the dual active bridge converter on the basis of realizing zero common mode modulation and power balance, as a preferred embodiment, the setting mode of the inner phase shift ratio and the outer phase shift ratio is further optimized in the embodiment. Specifically, the above size relationship between the output power normalized value and the inner phase shift ratio and the outer phase shift ratio, the soft switching boundary condition, and the setting of the inner phase shift ratio D1 that can suppress the direct current side ripple are preset conditions, and an optimal phase shift ratio lookup table is established in advance, which is used to record all combinations of the inner phase shift ratio and the outer phase shift ratio that can meet the preset conditions under each combination of the output power normalized value and the voltage conversion ratio; so that in actual application, after the output power normalized value and the voltage conversion ratio are determined, the corresponding optimal inner phase shift ratio and outer phase shift ratio combination can be found from the optimal phase shift ratio lookup table, and based on the lookup result, the adjustment between the inverter groups can be performed, so as to realize power balance.

[0099] The output power normalized value P * is the ratio of the output power to the power reference value P N , and P N is expressed as:

[0100]

[0101] In the embodiment, the establishment mode of the optimal phase shift ratio lookup table includes:

[0102] Considering that the output power normalized value P * will not exceed 1, and the voltage conversion ratio k will not exceed 1.5, the output power normalized value P * is selected in the range of (0, 1) with a step of 0.1, and the voltage conversion ratio k is selected in the range of (0, 1.5) with a step of 0.1, and the selected output power normalized value P * and the voltage conversion ratio k are combined to obtain multiple working points; in actual application, the step of selecting the working point can be flexibly adjusted, and if a more specific output power normalized value and voltage conversion ratio range can be determined, the related range can be adjusted accordingly.

[0103] For each working point (P *, solve the output power per unit P * The inner shift phase D1 and the outer shift phase D0 are combined to obtain the working point (P * , k) corresponding to the shift phase set U1.

[0104] The working point (P * , k) corresponding to the shift phase set U1 is filtered to obtain the inner shift phase and the outer shift phase combination satisfying the soft switching boundary condition, and the working point (P * , k) corresponding to the shift phase set U2 is obtained.

[0105] The working point (P * , k) corresponding to the shift phase set U2 is filtered to obtain the inner shift phase and the outer shift phase combination satisfying D1 = l / m, and the working point (P * , k) corresponding to the optimal shift phase set is obtained.

[0106] The optimal shift phase set corresponding to each working point is recorded to the optimal shift phase lookup table, and the establishment of the optimal shift phase lookup table is completed.

[0107] Wherein, l is a positive odd number, and m is the multiple or order of the target harmonic frequency relative to the switching frequency.

[0108] For the inner shift phase and the outer shift phase combination satisfying the preset condition, the smaller the inner shift phase D1, the more obvious the suppression effect on the DC side ripple. Therefore, before recording the optimal shift phase set corresponding to each working point to the optimal shift phase lookup table, the embodiment further includes:

[0109] For each working point, the inner shift phase and the outer shift phase combination with the smallest inner shift phase value in the optimal shift phase set corresponding to the working point are determined, and the remaining inner shift phase and the outer shift phase combination are deleted from the optimal shift phase set.

[0110] Based on the established optimal shift phase lookup table, as shown in Figure 5 When the embodiment performs zero common mode modulation for power balance for each group of transformers, the determination method of the inner shift phase D 1_1 and D 1_2 , and the outer shift phase D 0_1 and D 0_2 includes:

[0111] The output power per unit P * is determined, and the voltage conversion ratio k is calculated.

[0112] The P *, k corresponds to the outer shift phase ratio D0 and the inner shift phase ratio D1; when looking up, the inner shift phase ratio and the outer shift phase ratio corresponding to any working point can be calculated by linear interpolation;

[0113] The inner shift phase ratio D 1_1 and D 1_2 are both assigned as D1;

[0114] The control error ΔD0 of the outer shift phase ratio is determined, and the output power per unit P * The sign of the partial derivative of the output power per unit P * The sign of the partial derivative of the output power per unit P

[0115] The first sign is assigned to ΔD0 to obtain ΔD0', and the outer shift phase ratio D 0_1 is assigned as D0-ΔD0'; the second sign is assigned to ΔD0 to obtain ΔD0", and the outer shift phase ratio D 0_2 is assigned as D0+ΔD0".

[0116] Based on the output power per unit P * , the size relationship between the inner shift phase ratio D1 and the outer shift phase ratio D0 can be obtained, and the output power per unit P * is obtained with respect to the outer shift phase ratio D0, and the output power per unit P

[0117]

[0118] The specific partial derivative value can be obtained by substituting the corresponding outer shift phase ratio value into the above expression, and the corresponding sign can be extracted by using the Sign function; when the input of the Sign function is positive, the output is 1; when the input is negative, the output is -1; when the input is 0, the output is 0.

[0119] It is easy to understand that when the series-parallel connection mode of two transformers in a group of transformers is different, the control mode of the output power per unit P * and the control error ΔD0 of the outer shift phase ratio is different. Taking Figure 6 as an example, the input of the two transformers therein is in series, and the output is in parallel, and the power balance at this time is equivalent to the input voltage balance of the two transformers, wherein S A1_1 and S A1_2 respectively represent the driving signals of the upper switch tubes of the bridge arms A1 and A2, S B1_1 and S B1_2 respectively represent the driving signals of the upper switch tubes of the bridge arms B1 and B2, S C1_1 and S C1_2 respectively represent the driving signals of the upper switch tubes of the bridge arms C1 and C2, S D1_1 and S D1_2Respectively represent the driving signals of the upper switch tubes of bridge arms D1 and D2; S A2_1 and S A2_2 They represent the driving signals of the lower switch tubes of bridge arms A1 and A2, respectively. B2_1 and S B2_2 They represent the driving signals of the lower switch tubes of bridge arms B1 and B2, respectively. C2_1 and S C2_2 They represent the driving signals of the lower switch tubes of bridge arms C1 and C2, respectively. D2_1 and S D2_2 Respectively represent the driving signals of the lower switch tubes of the bridge arms D1 and D2. Figure 5 As shown, determine the output power per unit value P * , including: setting the output voltage command value The output voltage U of the first converter or the second converter o After making the difference, PI control is performed to obtain the output power per unit value P * ; Determine the control error ΔD0 compared to the outward shift, including: the average value of the input voltage U i_ave and the first converter input voltage U i1 After making the difference, PI control is performed to obtain the control error ΔD0 compared to the outward shift.

[0120] In other topologies, for example, if the inputs of the first converter and the outputs of the second converter are connected in parallel, the average value of the input current I i_ave The input current I i1 After making the difference, PI control is performed to obtain the control error ΔD0 of the external shift, or the average output current I o_ave The output current I of the first converter o1 After making the difference, PI control is performed to obtain the control error ΔD0 compared with the outward shift.

[0121] If the inputs of the first converter and the second converter are connected in parallel and their outputs are connected in series, the average input current I i_ave The input current I i1 After making the difference, PI control is performed to obtain the control error ΔD0 compared with the external shift, or the output voltage average value U o_ave The output voltage U of the first converter o1 After making the difference, PI control is performed to obtain the control error ΔD0 compared to the outward shift.

[0122] In general, this embodiment optimizes extended phase-shift modulation, thereby achieving power balance while realizing zero common-mode modulation, and optimizes the phase shift ratio to effectively suppress DC side ripple.

[0123] Example 3:

[0124] A zero common-mode modulation apparatus for implementing zero common-mode modulation of a dual active bridge converter apparatus of an even number of modules provided in Embodiment 1.

[0125] The embodiment comprises a control module and N modulation modules.

[0126] The control module is configured to evenly divide the 2N dual active bridge converters in the dual active bridge converter apparatus of the even number of modules into N groups of converters; in each group of converters, two dual active bridge converters are denoted as a first converter and a second converter, two bridge arms in the primary side of the first converter are denoted as A1 and B1, two bridge arms in the secondary side of the first converter are denoted as C1 and D1, two bridge arms in the primary side of the second converter are denoted as A2 and B2, and two bridge arms in the secondary side of the second converter are denoted as C2 and D2.

[0127] The N modulation modules are respectively configured to perform zero common-mode modulation for power balance of the N groups of converters, so as to implement zero common-mode modulation of the dual active bridge converters of the even number of modules.

[0128] The modulation module comprises:

[0129] a first control loop configured to determine an output power unit value P * and calculate a voltage conversion ratio k;

[0130] a lookup table unit connected to the output end of the first control loop, configured to look up an outer phase shift ratio D0 and an inner phase shift ratio D1 corresponding to P * and k from a pre-established optimal phase shift lookup table; the optimal phase shift lookup table records all combinations of the inner phase shift ratio and the outer phase shift ratio that can meet a preset condition under each combination of the output power unit value and the voltage conversion ratio; the preset condition comprises a size relationship between the output power unit value and the inner phase shift ratio and the outer phase shift ratio, a soft switching boundary condition, and the ability to suppress DC side ripples.

[0131] a second control loop configured to determine a control error ΔD0 of the outer phase shift ratio, and obtain a sign of a partial derivative of the output power unit value P * with respect to a current outer phase shift ratio of the first converter, and a sign of a partial derivative of the output power unit value P * with respect to a current outer phase shift ratio of the second converter, and denote the two signs as a first sign and a second sign, respectively.

[0132] and a phase shift ratio determination unit connected to the output end of the lookup table unit and the output end of the second control loop, configured to perform the following operations:

[0133] assigning the inner phase shift ratio D 1_1 between the bridge arms A1 and B1 to D1, and assigning the inner phase shift ratio D 1_2 between the bridge arms A2 and B2 to D1.

[0134] The first sign is given to ΔD0, and ΔD0' is obtained. The outer shift between the bridge arms A1 and C1 is compared with D 0_1 The value is D0-ΔD0';

[0135] The second sign is given to ΔD0, and ΔD0" is obtained. The outer shift between the bridge arms A2 and C2 is compared with D 0_2 The value is D0+ΔD0".

[0136] In this embodiment, the specific implementation of each module can refer to the description in Embodiment 2, which will not be repeated here.

[0137] Embodiment 4:

[0138] An even-module dual active bridge converter system, comprising: the even-module dual active bridge converter device provided in Embodiment 1, the zero common-mode modulation device provided in Embodiment 3, and a driver;

[0139] The driver is configured to generate the switch driving signals of each converter according to the inner shift phase ratio and the outer shift phase ratio determined by the zero common-mode modulation device, and apply the switch driving signals to the corresponding converter, so that the even-module dual active bridge converter device outputs the specified power.

[0140] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A dual active bridge converter device with an even number of modules, characterized in that: include: 2N dual active bridge converters; In the dual active bridge converter, a symmetrically coupled phase-shifting inductor is provided between the primary dual active bridge and the isolation transformer; The symmetrically coupled phase-shifting inductor includes two inductors, which are respectively arranged between the midpoints of the two bridge arms of the primary dual active bridge and the isolation transformer; the winding ends of the two inductors are in opposite directions, the self-inductance of the two inductors is equal, and the series equivalent inductance is L ph ; Where N is a positive integer, L ph It is the preset primary and secondary side phase shift inductance value.

2. The zero common mode modulation method of the dual active bridge converter device of even modules according to claim 1, characterized in that: include: Evenly divide the 2N dual-active bridge converters in the dual-active bridge converter device of the even-numbered modules into N groups of converters; in each group of converters, the two dual-active bridge converters are respectively recorded as a first converter and a second converter, the two bridge arms of the primary side of the first converter are respectively recorded as A1 and B1, and the two bridge arms of the secondary side are respectively recorded as C1 and D1, and the two bridge arms of the primary side of the second converter are respectively recorded as A2 and B2, and the two bridge arms of the secondary side are respectively recorded as C2 and D2; For each group of converters, respectively performing power balanced zero common mode modulation to achieve zero common mode modulation of the dual active bridge converter device of the even modules; The power balanced zero common mode modulation includes: Under the condition of meeting the output power requirement, the switch drive signals of control bridge arms A1 and A2 are complementary, and the internal shift between bridge arms A1 and B1 is controlled to be D 1_1 Compared with the inward shift between bridge arms A2 and B2, D 1_2 Equal; Under the condition that the switch drive signals of bridge arms C1 and D1 are complementary, and the switch drive signals of bridge arms C2 and D2 are complementary, the outward shift between bridge arms A1 and C1 is adjusted to be D 0_1 Compared with the outward shift between bridge arms A2 and C2, D 0_2 , so that the power of the first converter and the second converter are equal.

3. The zero common mode modulation method according to claim 2, wherein: Inward shift compared to D 1_1 and D 1_2 , and outward shift compared to D 0_1 and D 0_2 Methods of determination include: Determine the output power per unit value P * , and calculate the voltage conversion ratio k; Find P from the pre-established optimal phase shift lookup table * , k corresponding to the outward phase shift D0 and the inward phase shift D1; the optimal phase shift lookup table records all inward phase shift and outward phase shift combinations that can meet preset conditions under each output power per unit value and voltage conversion ratio combination; the preset conditions include: the relationship between the output power per unit value and the inward phase shift and the outward phase shift, the soft switching boundary conditions, and the ability of the inward phase shift D1 to suppress DC side ripple; Compare the inward shift to D 1_1 and D 1_2 All are assigned the value of D1; Determine the control error ΔD0 of the outward shift phase and obtain the output power per unit value P * The sign of the partial derivative relative to the current outward shift of the first converter, and the per-unit output power value P * The signs of the partial derivatives relative to the current outward shift of the second transformer are denoted as the first sign and the second sign respectively; Assign the first sign to ΔD0 to get ΔD0', and compare the outward shift to D 0_1 Assign the value D0-ΔD0'; assign the second sign to ΔD0 to get ΔD0", and compare the outward shift to D 0_2 Assign the value to D0+ΔD0".

4. The zero common mode modulation method according to claim 3, wherein: The optimal phase shift lookup table is established in the following manner: Select the output power per unit value P in the range of (0,1) * , and select the voltage conversion ratio k in the range of (0,1.5) to obtain multiple operating points; each operating point corresponds to a combination of output power per unit value and voltage conversion ratio; For each working point (P * ,k), solve the output power per unit value P * Compared with the size relationship between the inner shift D1 and the outer shift D0, the inner shift and outer shift are combined to obtain the working point (P * ,k) The corresponding shift ratio set U1; From the working point (P * ,k) in the corresponding shift ratio set U1, select the inner shift ratio and outer shift ratio combination that meet the soft switching boundary conditions, and obtain the working point (P * ,k) corresponds to the shift set U2; From the working point (P * ,k) in the corresponding shift ratio set U2, select the inner shift ratio and outer shift ratio combination that satisfies D1=l / m, and obtain the working point (P * ,k) corresponds to the optimal shift ratio set; Recording the optimal phase shift ratio set corresponding to each working point into the optimal phase shift ratio lookup table, thereby completing the establishment of the optimal phase shift ratio lookup table; Wherein, l is a positive odd number, and m is the multiple or order of the target harmonic frequency relative to the switching frequency.

5. The zero common mode modulation method according to claim 4, wherein: Before recording the optimal shift ratio set corresponding to each working point into the optimal shift ratio lookup table, the following steps are also included: For each working point, determine the inner shift ratio and outer shift ratio combination with the smallest inner shift ratio value in the corresponding optimal shift ratio set, and delete the remaining inner shift ratio and outer shift ratio combinations from the optimal shift ratio set.

6. The zero common mode modulation method according to any one of claims 3 to 5, characterized in that: Determine the output power per unit value P * ,include: The output voltage command value U o * The output voltage U of the first converter or the second converter o After making the difference, PI control is performed to obtain the output power per unit value P * .

7. The zero common mode modulation method according to claim 6, wherein: Determine the control error ΔD0 of the outward shift phase, including: If the inputs of the first converter and the second converter are connected in series, the input voltage command value U i_ave and the first converter input voltage U i1 After making the difference, PI control is performed to obtain the control error ΔD0 compared with the outward shift. If the inputs of the first converter and the outputs of the second converter are connected in parallel, the average input current I i_ave The input current I i1 After making the difference, PI control is performed to obtain the control error ΔD0 of the external shift, or the average output current I o_ave The output current I of the first converter o1 After making the difference, PI control is performed to obtain the control error ΔD0 compared with the outward shift. If the inputs of the first converter and the second converter are connected in parallel and their outputs are connected in series, the average input current I i_ave The input current I i1 After making the difference, PI control is performed to obtain the control error ΔD0 compared with the external shift, or the output voltage average value U o_ave The output voltage U of the first converter o1 After making the difference, PI control is performed to obtain the control error ΔD0 compared to the outward shift.

8. The zero common mode modulation device of the dual active bridge converter device of even modules according to claim 1, characterized in that: include: A control module and N modulation modules; The control module is used to evenly divide 2N dual-active bridge converters in the dual-active bridge converter device of the even-numbered modules into N groups of converters; in each group of converters, the two dual-active bridge converters are respectively recorded as a first converter and a second converter, the two bridge arms of the primary side of the first converter are respectively recorded as A1 and B1, and the two bridge arms of the secondary side are respectively recorded as C1 and D1, and the two bridge arms of the primary side of the second converter are respectively recorded as A2 and B2, and the two bridge arms of the secondary side are respectively recorded as C2 and D2; The N modulation modules are respectively used to perform power-balanced zero common mode modulation on the N groups of converters, so as to realize zero common mode modulation of the dual active bridge converter device of the even-numbered modules; The modulation module includes: The first control loop is used to determine the output power per unit value P * , and calculate the voltage conversion ratio k; A lookup table unit, whose input terminal is connected to the output terminal of the first control loop, is used to look up P from a pre-established optimal phase shift lookup table. * , k corresponding to the outward phase shift D0 and the inward phase shift D1; the optimal phase shift lookup table records all inward phase shift and outward phase shift combinations that can meet preset conditions under each output power per unit value and voltage conversion ratio combination; the preset conditions include: the relationship between the output power per unit value and the inward phase shift and the outward phase shift, the soft switching boundary conditions, and the ability to suppress DC side ripple; The second control loop is used to determine the control error ΔD0 of the outward shift phase and obtain the output power per unit value P * The sign of the partial derivative relative to the current outward shift of the first converter, and the per-unit output power value P * The signs of the partial derivatives relative to the current outward shift of the second transformer are denoted as the first sign and the second sign respectively; and a shift ratio determining unit, a first input terminal of which is connected to the output terminal of the table lookup unit, and a second input terminal of which is connected to the output terminal of the second control loop, and configured to perform the following operations: Compare the inward shift between bridge arms A1 and B1 to D 1_1 Compared with the inward shift between bridge arms A2 and B2, D 1_2 All are assigned the value of D1; Assign the first sign to ΔD0 to get ΔD0', and compare the outward displacement between bridge arms A1 and C1 to D 0_1 Assign the value to D0-ΔD0'; Assign the second sign to ΔD0, and get ΔD0", and compare the outward displacement between bridge arms A2 and C2 with D 0_2 Assign the value to D0+ΔD0".

9. A dual active bridge converter system with an even number of modules, characterized in that: include: The dual active bridge converter device of even modules according to claim 1, the zero common mode modulation device and driver according to claim 8; The driver is used to generate a switch drive signal for each converter according to the inward shift phase ratio and the outward shift phase ratio determined by the zero common mode modulation device, and apply it to the corresponding converter, so that the dual active bridge converter device of the even-numbered modules outputs a specified power.

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