Sensorless parallel current sharing control method and device for dual-active bridge converter

Abstract

The invention provides a sensorless parallel current-sharing control method and device for a dual active bridge converter, and the method comprises the steps: building the corresponding relation between the phase-shifting offset of DAB except a main DAB and the circuit parameters of DAB except the main DAB, and the circuit parameters and phase-shifting offset of the main DAB according to a power balance condition when all DAB circuit parameters are not matched; the IPOP dual-active bridge converter starts to operate in a common phase shift phase ratio stage, the phase shift phases of the DABs are equal, a disturbance component is applied to the phase shift phase ratio of the main DAB, and a transmission power expression of the DABs except the main DAB and the main DAB in a new steady state is obtained; calculating the phase shift offset of the DAB except the main DAB relative to the main DAB; then outputting a current based on a phase shift offset amount of DABs other than the main DAB relative to the main DAB; current sharing can be well realized when the system is in a forward mode and a reverse mode; current sharing can be realized without a current sensor.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power electronic conversion, and particularly relates to a sensorless parallel current sharing control method and device for a dual active bridge (DAB) converter. BACKGROUND

[0002] An airborne power supply system needs to meet the requirements of high power density, high efficiency and high reliability. Dual active bridge (DAB) converters are widely used in airborne power supply systems due to their electrical isolation, bidirectional power transmission capability, soft switching characteristics and ease of modularization. By connecting multiple DAB converter units in series or parallel, the high power level and system integration requirements can be effectively met. This scheme can increase the output power of the power supply, realize N+1 redundancy backup function, and improve the system reliability. When multiple DAB units are operated in parallel, the balanced distribution of load current is crucial. Traditional current sharing methods rely on current sensors to detect the output current of each module and adjust the phase shift angle to achieve current sharing, which increases the system cost and complexity.

[0003] Existing sensorless schemes mostly achieve current sharing by estimating inductance current, but the algorithm is complex and relies on accurate parameters, and the current sharing accuracy decreases when the input voltage fluctuates (such as during the startup / transient process of the aviation power supply) or the module parameters are inconsistent. SUMMARY

[0004] To solve the technical problem that the current sharing algorithm through estimation of inductance current in the prior art is complex and relies on accurate parameters, and the current sharing accuracy decreases when the input voltage fluctuates or the module parameters are inconsistent, the present application proposes a sensorless parallel current sharing control method for a dual active bridge (DAB) converter, which is a simple sensorless control strategy that achieves current sharing control of an IPOP-DAB converter through a perturbation algorithm and estimates the parameter mismatch of each module using the perturbation algorithm. The technical solution is as follows: In a first aspect, a sensorless parallel current sharing control method for a dual active bridge (DAB) converter is provided, which is used for a voltage loop regulator. The method comprises: Step 1. When the circuit parameters of all DABs are mismatched (not equal), the phase shift bias of the DABs except the main DAB is established according to the power balance condition, and the phase shift bias of the DABs except the main DAB, the circuit parameters of the main DAB and the corresponding relationship of the phase shift bias are established. The phase shift bias of the main DAB is generated by the voltage loop regulator composed of the output voltage and the reference voltage; Step 2. The IPOP dual active bridge (DAB) converter starts to operate in the common phase shift bias stage, the phase shift bias of each DAB is equal, a disturbance component is applied to the phase shift bias of the main DAB, and the transmission power expressions of the DABs except the main DAB and the main DAB in the new steady state are obtained according to the law of conservation of energy to estimate the circuit parameters of the DABs except the main DAB; Step 3, based on the phase-shifted bias amount of the DAB other than the main DAB and the correspondence relationship between the circuit parameters of the DAB other than the main DAB, the circuit parameters of the main DAB and the phase-shifted bias amount, the phase-shifted bias amount of the DAB other than the main DAB relative to the main DAB is calculated; Step 4, based on the phase-shifted bias amount of the DAB other than the main DAB relative to the main DAB, the output current is output.

[0005] Optionally, the main DAB is the first DAB, The phase-shifted bias amount of the DAB other than the main DAB The correspondence relationship between the circuit parameters of the DAB other than the main DAB, the circuit parameters of the main DAB and the phase-shifted bias amount is: (1) In formula (1), , represents the circuit parameters of the i-th DAB, represents the circuit parameters of the main DAB, is the transformer ratio of the i-th DAB, is the sum of the series inductance and the transformer leakage inductance of the i-th DAB, is the transformer ratio of the main DAB, is the sum of the series inductance and the transformer leakage inductance of the main DAB, i is greater than or equal to 2 and less than or equal to m, and m is the total number of DABs.

[0006] Further, the method further comprises: For each DAB in the IPOP DAB, a steady-state output current expression is obtained according to the transmission power expression thereof under the single-phase-shift modulation strategy.

[0007] wherein, The IPOP dual active bridge converter starts to operate in the common phase-shifted phase, the phase-shifted bias amount of each DAB is equal, and is denoted as , a disturbance component is applied to the phase-shifted bias of the main DAB After the IPOP dual active bridge converter reaches a new steady state, the voltage loop regulator adjusts to According to the law of conservation of energy, it is obtained that the transmission power of the DAB other than the main DAB and the main DAB satisfies formula (2) under the new steady state: (2) The phase-shifted bias amount of each DAB is calculated by formula (2); The current of each DAB after the disturbance is obtained by substituting the phase-shifted bias amount of each DAB into the steady-state output current expression; The phase-shift ratio biasing amount of the DABs other than the main DAB is obtained based on the current of each DAB after the disturbance, and a corresponding relationship between the phase-shift ratio biasing amount of the DABs other than the main DAB, the circuit parameters of the DABs other than the main DAB, the circuit parameters of the main DAB and the phase-shift ratio.

[0008] The phase-shift ratio biasing amount of the DABs other than the main DAB is obtained based on the current of each DAB after the disturbance, and a corresponding relationship between the phase-shift ratio biasing amount of the DABs other than the main DAB, the circuit parameters of the DABs other than the main DAB, the circuit parameters of the main DAB and the phase-shift ratio. The output current variation of each DAB caused by the disturbance is calculated based on the current of each DAB after the disturbance. The total variation of the current is set to 0, and a steady-state output current expression is obtained. The phase-shift ratio biasing amount of the DABs other than the main DAB is obtained based on the current of each DAB after the disturbance, and a corresponding relationship between the phase-shift ratio biasing amount of the DABs other than the main DAB, the circuit parameters of the DABs other than the main DAB, the circuit parameters of the main DAB and the phase-shift ratio.

[0009] The circuit parameters include transformer turns ratio and inductance.

[0010] In a second aspect, a sensorless parallel current sharing control device for a dual active bridge (DAB) converter is provided, which is used in a voltage loop regulator and performs the method of any one of the first aspect, and the device comprises: The establishing module is configured to establish a corresponding relationship between the phase-shift ratio biasing amount of the DABs other than the main DAB, the circuit parameters of the DABs other than the main DAB, the circuit parameters of the main DAB and the phase-shift ratio, according to a power balance condition, when the circuit parameters of all the DABs are not matched (not equal); and the phase-shift ratio of the main DAB is generated by a voltage loop regulator composed of an output voltage and a reference voltage. The estimating module is configured to start the IPOP DAB converter to run in a common phase-shift ratio stage, the phase-shift ratios of the DABs are equal, a disturbance component is applied to the phase-shift ratio of the main DAB, a transmission power expression of the DABs other than the main DAB and the main DAB under a new steady state is obtained according to the law of conservation of energy, and the circuit parameters of the DABs other than the main DAB are estimated. The calculating module is configured to calculate the phase-shift ratio biasing amount of the DABs other than the main DAB relative to the main DAB, based on the corresponding relationship between the phase-shift ratio biasing amount of the DABs other than the main DAB, the circuit parameters of the DABs other than the main DAB, the circuit parameters of the main DAB and the phase-shift ratio. The output module is configured to output the current based on the phase-shift ratio biasing amount of the DABs other than the main DAB relative to the main DAB.

[0011] In a third aspect, a sensorless parallel current sharing control device for a dual active bridge converter is provided, characterized in that for a voltage loop regulator, the device comprises a processor and a memory, the processor is configured to execute instructions stored in the memory, and the processor implements the sensorless parallel current sharing control method for a dual active bridge converter according to the first aspect by executing the instructions.

[0012] The present application has at least the following beneficial effects: The present application provides a sensorless current sharing control method for IPOP-DAB converter, which realizes power balance of DAB units and simplifies the system circuit. The proposed control method can well realize current sharing when the system is in forward mode and reverse mode. Through the disturbance algorithm, current sharing can be realized without current sensor, which can simplify the system circuit and reduce the cost. The proposed method can also be used as a backup scheme for other control schemes that require additional current sensors, meeting the lightweight demand in the aviation field. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a two-phase IPOP DAB converter topology diagram; Figure 2 is a disturbance block diagram of two-phase DAB; Figure 3 is a phase shift ratio change diagram of two-phase DAB under disturbance; Figure 4 is a control block diagram of two-phase DAB sensorless parallel current sharing algorithm. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0015] The features and exemplary embodiments of the various aspects of the present application will be described below in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without some or all of these specific details. The description of the embodiments is merely illustrative of the present application and does not limit the scope of the present application. The present application is not limited to the specific arrangements and instrumentalities set forth in the following description and claims, but covers any improvements, alternatives, and modifications within the spirit and scope of the present application. In the drawings and the following description, well-known structures and techniques have not been shown in order not to obscure the present application.

[0016] It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict, and each embodiment can be referred to and cited by each other.

[0017] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] The present application provides a sensorless parallel current sharing control method and device for a dual active bridge converter, which can solve the problem of sensorless parallel current sharing control of an input parallel output parallel (IPOP) dual active bridge (DAB) module.

[0019] The present application introduces the principle of sensorless parallel current sharing of IPOP DAB based on power balance mechanism and phase parameter estimation based on disturbance.

[0020] The sensorless current sharing control method provided by the present application estimates the parameter mismatch of each DAB unit through a disturbance algorithm, and designs a corresponding phase shift ratio compensation according to the parameter mismatch information. The method has strong robustness and is suitable for harsh environments in the aviation field.

[0021] Specifically, referring to Figure 1 The system involved in the present application includes a multi-phase DAB. The present application proposes a sensorless current sharing control method for IPOP-DAB converter, which includes the following contents: 1. Power balance mechanism For each DAB unit in the IPOP DAB system, the steady-state output current expression is obtained according to the transmission power expression under the single phase shift modulation strategy. When the system parameters are mismatched, in order to realize the current sharing of each DAB unit, the phase shift ratio bias of each DAB unit relative to the main unit of the DAB needs to be considered, and the phase shift ratio compensation is performed. According to the power balance condition, the relationship between the phase shift ratio bias of the first DAB unit and the internal parameters of the first DAB unit and the phase shift ratio is found.

[0022] ​2. Parameter estimation based on perturbation method The system starts to run in the common phase shift ratio phase, and the phase shift ratio of each DAB unit is equal, which is generated by the voltage loop regulator composed of the output voltage and the reference voltage. In order to realize the parameter estimation of the second to mth DAB unit, a perturbation component needs to be applied to the phase shift ratio of the first DAB unit, because the phase shift ratio is positively correlated with the power, and according to the law of conservation of energy, the transmission power expression of the second or i-th DAB in the new state can be obtained, and then the internal parameters of the second or i-th DAB unit are estimated, and the phase shift ratio perturbation of each module is obtained.

[0023] Specifically, the implementation process of the present application includes the following contents: 1. Principle of sensorless parallel current sharing based on power balance For each DAB unit in the IPOP DAB system, under the single phase shift modulation strategy, the power transmission expression is as formula (3), wherein is the transformer ratio of the i-th DAB, is the sum of the series inductance and the transformer leakage inductance of the i-th DAB, is the switching frequency, is the primary side DC voltage, is the secondary side DC voltage, is the phase shift ratio of the i-th DAB under the single phase shift modulation strategy.

[0024] (3) When the power is transmitted forwardly, the steady-state output current expression of the secondary side (the output end) is as formula (4): (4) As can be seen from formula (3) and formula (4), when the circuit parameters of the first phase and the i-th phase DAB are consistent, the output current of the first phase DAB is equal to the output current of the i-th phase DAB under the control of the common phase shift ratio. In practice, the circuit parameters of each DAB may not match (not equal). When the system parameters do not match, in order to realize parallel current sharing, the first phase DAB (the main DAB) is taken as a reference, and the phase shift ratio of the i-th phase is adjusted on the basis of the common phase shift ratio control to compensate for the influence of parameter mismatch, so there is a relationship as formula (5): (5) is obtained by the voltage loop regulator of the first phase DAB, is the phase shift ratio increment of the second to mth phase DAB, which can be obtained from the IPOP system, , formula (5) is brought into formula (4), and according to the current sharing requirement, , the expression of is as formula (6): (6) In formula (6), , represents the internal parameter of DAB.

[0025] 2. Phase parameter estimation based on disturbance Taking 2-phase DAB as an example, first, the system is in the common phase shift ratio control stage, . In order to estimate , a disturbance is applied to the phase shift ratio of the first phase DAB, denoted as , as shown in Figure 2 . After the disturbance is added, the system reaches a new steady state, and the voltage loop regulator adjusts to . The dynamic process is shown in Figure 3 , and from formula (3) , since the phase shift ratio of the first phase DAB is reduced by , its power will also decrease, according to the law of conservation of energy, the power of the second phase DAB will increase, and in the new steady state, the transmission power and the phase shift ratio of the two modules satisfy the relationship as formula (7): (7) The phase shift ratio of each phase DAB can be represented by formula (8): (8) and is the phase shift ratio offset caused by the disturbance, , formula (8) is brought into formula (4), and the current of the two phase DABs after the disturbance is formula (9): (9) Therefore, the output current change caused by the disturbance can be represented by formula (10): (10) According to the power balance mechanism, the total change of the current should be 0, as formula (11): (11) Combined with formula (4), the expression of can be obtained as formula (12): (12) The sensorless parallel current sharing control block diagram of two-phase DAB is shown in Figure 4 , which mainly includes common phase shift ratio control, phase parameter estimation based on disturbance, and phase shift ratio compensation. This method is also applicable to m-phase DAB, and in the m-phase DAB system, the first phase DAB is taken as the main reference module, and when the i-th phase DAB parameter is estimated, the phase shift ratios of the remaining m-2 phase DABs are locked as To make DAB have greater power adjustment range, smaller backflow power and current stress, this method can also be extended to multi-phase modulation strategy.

[0026] The above merely expresses the embodiments of the present application, which are described in a more specific and detailed manner, but should not be understood as limiting the patent scope. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. In addition, the parts not described in detail of the present application are all conventional technologies.

Claims

1. A sensorless parallel current sharing control method for dual active bridge converter, characterized in that, The method for a voltage loop regulator comprises the following steps: Step 1, when the circuit parameters of all DABs are not matched, a corresponding relationship between the phase-shifted ratio bias of the DABs except the main DAB and the circuit parameters of the DABs except the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio is established according to the power balance condition; the phase-shifted ratio of the main DAB is generated by a voltage loop regulator composed of an output voltage and a reference voltage; Step 2, the IPOP dual active bridge converter starts to operate in the common phase-shifted ratio stage, the phase-shifted ratios of the DABs are equal, a disturbance component is applied to the phase-shifted ratio of the main DAB, the transmission power expressions of the DABs except the main DAB and the main DAB in the new steady state are obtained according to the law of conservation of energy, and the circuit parameters of the DABs except the main DAB are estimated; Step 3, the phase-shifted ratio bias of the DABs except the main DAB relative to the main DAB is calculated based on the corresponding relationship between the phase-shifted ratio bias of the DABs except the main DAB and the circuit parameters of the DABs except the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio; Step 4, the output current of the DABs except the main DAB relative to the main DAB is output based on the phase-shifted ratio bias.

2. The method of claim 1, wherein, The main DAB is the first DAB, Phase shift bias amount of the DAB other than the main DAB The correspondence of the circuit parameter of the DAB other than the main DAB, the circuit parameter of the main DAB, and the phase shift bias amount is: （1） in formula (1), , represents the circuit parameter of the i-th DAB, represents the circuit parameter of the main DAB, is the transformer ratio of the i-th DAB, is the sum of the series inductance and the transformer leakage inductance of the i-th DAB, is the transformer ratio of the main DAB, is the sum of the series inductance and the transformer leakage inductance of the main DAB, i is greater than or equal to 2 and less than or equal to m, and m is the total number of DABs.

3. The method of claim 1, wherein, The method further comprises the following steps: For each DAB in the IPOP DAB, a steady-state output current expression is obtained according to the transmission power expression of the DAB in the single phase-shifted modulation strategy.

4. The method according to claim 3, wherein, The IPOP dual active bridge converter starts to operate in the common phase-shifted phase, and the phase-shifted phase of each DAB is equal, denoted as A disturbance component is applied to the phase-shifted phase of the main DAB After the IPOP dual active bridge converter reaches a new steady state, the voltage loop regulator adjusts to Under the action of the disturbance, to According to the law of conservation of energy, the transmission power of the DABs other than the main DAB and the main DAB in the new steady state satisfies formula (2): (2) the phase-shifted ratio of each DAB is calculated by formula (2); the phase-shifted ratio of each DAB is substituted into the steady-state output current expression to obtain the current of each DAB after disturbance; the corresponding relationship between the phase-shifted ratio bias of the DABs except the main DAB and the circuit parameters of the DABs except the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio is obtained based on the current of each DAB after disturbance.

5. The method of claim 4, wherein, The corresponding relationship between the phase-shifted ratio bias of the DABs except the main DAB and the circuit parameters of the DABs except the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio is obtained based on the current of each DAB after disturbance, and comprises the following steps: the output current variation of each DAB caused by disturbance is calculated based on the current of each DAB after disturbance; Let the total change of the current be 0, and combine the steady-state output current expression to obtain The expression of the phase-shifted bias of the DAB other than the main DAB and the corresponding relationship of the circuit parameters of the DAB other than the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio can be obtained.

6. The method of claim 1, wherein, the circuit parameters include transformer ratio, inductance.

7. A sensorless parallel current sharing control apparatus for a dual active bridge converter, characterized by, The device for executing the method of any one of claims 1 to 6 comprises the following modules: a establishing module, configured to, when the circuit parameters of all DABs are not matched, establish a corresponding relationship between the phase-shifted ratio bias of the DABs except the main DAB and the circuit parameters of the DABs except the main DAB, the circuit parameters of the main DAB and the phase-shifted ratio according to the power balance condition; the phase-shifted ratio of the main DAB is generated by a voltage loop regulator composed of an output voltage and a reference voltage; an estimating module, configured to, when the IPOP dual active bridge converter starts to operate in the common phase-shifted ratio stage, the phase-shifted ratios of the DABs are equal, a disturbance component is applied to the phase-shifted ratio of the main DAB, the transmission power expressions of the DABs except the main DAB and the main DAB in the new steady state are obtained according to the law of conservation of energy, and the circuit parameters of the DABs except the main DAB are estimated; The computing module is configured to calculate the phase-shifted biasing amount of the DAB other than the main DAB relative to the main DAB based on a correspondence between the phase-shifted biasing amount of the DAB other than the main DAB and the circuit parameter of the DAB other than the main DAB, the circuit parameter of the main DAB, and the phase-shifted biasing amount of the main DAB. The output module is configured to output the current based on the phase-shifted biasing amount of the DAB other than the main DAB relative to the main DAB.

8. A sensorless parallel current sharing control device for a dual active bridge converter, characterized in that, A voltage loop regulator includes a processor and a memory, the processor is configured to execute instructions stored in the memory, and the processor implements the sensorless parallel current sharing control method of the dual active bridge converter according to any one of claims 1 to 6 by executing the instructions.

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