Control strategy optimization method based on fundamental wave circulating current

Abstract

The invention provides a control strategy optimization method based on fundamental wave circulating current, which is applied to a three-active bridge DC-DC converter and comprises the following steps: collecting the middle-point voltage of each port in the three-active bridge DC-DC converter; determining a phasor relationship between the midpoint voltage and the inductive current between the ports based on the midpoint voltage of each port; determining the active power and the reactive power of the second port and the active power and the reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductive current between the ports; and based on the active power and the reactive power of the second port and the active power and the reactive power of the third port, an optimized phase shift ratio combination is determined, and the optimized phase shift ratio combination is used for realizing control of the three-active-bridge DC-DC converter. According to the optimization control strategy provided by the invention, the reactive power of the TAB can be effectively reduced, the optimization control strategy is more obvious under the light load condition, and the system operation efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of power electronic equipment control, and in particular to the field of converter control. Background Art

[0002] The triple active bridge DC-DC converter (TAB) has the advantages of high power density, electrical isolation and flexible control, and has a broad application prospect in DC power grid. The triple active bridge converter under the traditional single phase shift (SPS) control strategy has a large internal reflux power, which leads to an increase in the effective current value and loss of the converter.

[0003] In the prior art, there are many documents that have studied the modeling method, topology improvement, soft switching characteristics, control strategy, and other issues of TAB, and proposed corresponding improvement methods. However, such improvement methods are either only for TAB converters with specific resonant structures and are not applicable to all DC-DC converters, or they do not analyze the reactive return and loss of TAB, and all are segmented analysis in the time domain. Moreover, although the reactive power of the DC-DC converter is optimized and the system operation efficiency is improved, the mathematical model is difficult to analyze and complex to solve. Therefore, how to achieve a mathematical model that can be applied to all DC-DC converters and analyze the reactive return and loss of TAB while having low analysis difficulty and simple solution is a problem that needs to be solved urgently. Summary of the invention

[0004] In order to overcome the above technical defects, the present application provides a control strategy optimization method, storage medium and device based on fundamental circulation.

[0005] To achieve the above objectives, this application is implemented according to the following technical solutions:

[0006] In a first aspect, the present application provides a control strategy optimization method based on fundamental circulation, which is applied to a three-active-bridge DC-DC converter, wherein the three-active-bridge DC-DC converter has three ports, including:

[0007] Collecting the midpoint voltage of each port in the three active bridge DC-DC converter;

[0008] Based on the midpoint voltages of the ports, determining the phasor relationship between the midpoint voltages and the inductor current between the ports;

[0009] Determine the active power and reactive power of the second port and the active power and reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductor current between the ports;

[0010] Based on the active power and reactive power of the second port and the active power and reactive power of the third port, an optimized phase shift combination is determined, and the optimized phase shift combination is used to realize control of the three active bridge DC-DC converter.

[0011] Optionally, determining the phasor relationship between the midpoint voltage and the inductor current between the ports based on the midpoint voltage of each port includes:

[0012] Performing Fourier series decomposition on the midpoint voltage of each port to determine the frequency spectrum characteristics of the midpoint voltage of each port;

[0013] Determining the fundamental wave midpoint voltage of each port based on the frequency spectrum characteristics of the midpoint voltage of each port;

[0014] Based on the determination of the fundamental wave midpoint voltage of each port; determining the phasor form of the fundamental wave midpoint voltage of each port;

[0015] Based on the phasor form of the fundamental wave midpoint voltage of each port, the phasor relationship between the midpoint voltage and the inductor current between each port is determined.

[0016] Optionally, it is characterized in that the determining the active power and reactive power of the second port, and the active power and reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductor current between the ports includes:

[0017] Determining the calculation relationship of the voltage and current fundamental components between the ports based on the phasor relationship between the midpoint voltage and the inductor current between the ports;

[0018] Based on the phasor form of the fundamental wave midpoint voltage of each port and the calculation relationship between the voltage and current fundamental wave components between the ports, the phasor expressions of the inductor currents of the second port and the third port are determined; wherein the second port and the third port are two ports among the ports;

[0019] Based on the phasor form of the fundamental midpoint voltage of each port and the phasor expression of the inductor current of the second port and the third port, the active power and reactive power of the second port and the active power and reactive power of the third port are determined.

[0020] Optionally, determining the optimized shift ratio combination based on the active power and reactive power of the second port and the active power and reactive power of the third port includes:

[0021] Taking the minimum sum of the reactive power of the second port and the reactive power of the third port as the objective function;

[0022] Taking the active power of the second port and the active power of the third port as constraint conditions;

[0023] The objective function is solved by using a particle swarm algorithm to obtain the corresponding shift ratio within the full power range;

[0024] Obtaining output voltages of the second port and the third port;

[0025] An optimized shift phase combination is determined based on the output voltages of the second port and the third port and corresponding shift phase ratios within the full power range.

[0026] Optionally, taking the active power of the second port and the active power of the third port as constraint conditions includes:

[0027] Taking the maximum value of the active power of the third port as a reference, normalizing the active power of the second port and the active power of the third port to obtain a per-unit value of the active power of the second port and a per-unit value of the active power of the third port;

[0028] Taking the per-unit value of the active power of the second port and the per-unit value of the active power of the third port as constraint conditions;

[0029] Optionally, the determining an optimized shift phase combination based on the output voltages of the second port and the third port and corresponding shift phases within the full power range comprises:

[0030] The output voltages of the second port and the third port are respectively subtracted from a given value, and then a second phase shift ratio and a third phase shift ratio are obtained after a PI controller; wherein the second phase shift ratio is a phase shift angle duty ratio between the first port and the second port, and the third phase shift ratio is a phase shift angle duty ratio between the first port and the third port;

[0031] Based on the second shift phase ratio and the third shift phase ratio, and the corresponding shift phase ratio within the full power range, an optimized shift phase combination is determined.

[0032] In a second aspect, the present application provides a computer device, comprising a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, at least one program, a code set or an instruction set is loaded and executed by the processor to implement a control strategy optimization method based on fundamental circulation as described in any one of the first aspects.

[0033] In a third aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores at least one instruction, at least one program, code set or instruction set, and the at least one instruction, at least one program, code set or instruction set is loaded and executed by a processor to implement a control strategy optimization method based on fundamental circulation as described in any one of the first aspects.

[0034] This application has the following beneficial effects:

[0035] This application calculates the inductor current, active power and reactive power of TAB under the optimized control strategy based on Fourier series decomposition and phasor analysis, and constructs a TAB mathematical model, thereby avoiding the complexity of the traditional time domain analysis method and simplifying the calculation. The PSO algorithm is used to solve the model, and the fundamental circulation current of the output section is optimized by analyzing the different output powers. The particle swarm algorithm is used to not only reduce the complexity of the mathematical model, but also solve the problem that the optimal solution cannot be obtained due to multivariable and nonlinear constraints. Thereby, in the case of forward power transmission, the optimized control strategy proposed in this application can effectively reduce the reactive power of TAB, which is more obvious under light load conditions, and improves the system operation efficiency.

[0036] In addition to the above-described purposes, features and advantages, the present application also has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 This is the topological structure diagram of the TAB converter of this application.

[0039] Figure 2 It is a schematic diagram of the waveform of TAB under the SPS control strategy.

[0040] Figure 3 It is a schematic diagram of the waveform of TAB under the optimized control strategy of the present application.

[0041] Figure 4 It is a flow chart of a control strategy optimization method based on fundamental circulation provided in an embodiment of the present application.

[0042] Figure 5 It is a schematic diagram of the voltage and current vector analysis of the equivalent circuit provided in the embodiment of the present application.

[0043] Figure 6 It is a flow chart of the particle swarm algorithm provided in the embodiment of the present application.

[0044] Figure 7 It is a block diagram for implementing the minimum reactive power optimization control strategy of the output ports (the second port and the third port) provided in an embodiment of the present application.

[0045] Figure 8 This is the voltage waveform of each port under two control modes when P2=500W and P3=122.5W during the simulation verification of the embodiment of the present application.

[0046] Fig. 9 It is a schematic diagram of the output voltage and current waveforms of port 2 and port 3 when a sudden load change occurs at port 2 during the simulation verification of the embodiment of the present application.

[0047] FIG10( a ) is a schematic diagram of the inductor current waveforms of port 2 under two control modes when P2=125W and P3=122.5W during simulation verification of an embodiment of the present application.

[0048] FIG10( b ) is a schematic diagram of the inductor current waveforms of port 3 under two control modes when P2=125W and P3=122.5W during the simulation verification of the embodiment of the present application.

[0049] FIG. 11( a ) is a schematic diagram of the inductor current waveforms of port 2 under two control modes when P2 = 250 W and P3 = 122.5 W during simulation verification of an embodiment of the present application.

[0050] FIG11( b ) is a schematic diagram of the inductor current waveforms of port 3 under two control modes when P2=250W and P3=122.5W during the simulation verification of the embodiment of the present application.

[0051] FIG. 12( a ) is a schematic diagram of the inductor current waveforms of port 2 under two control modes when P2 = 500 W and P3 = 122.5 W during simulation verification of an embodiment of the present application.

[0052] FIG12( b ) is a schematic diagram of the inductor current waveforms of port 3 under two control modes when P2=500W and P3=122.5W during the simulation verification of the embodiment of the present application.

[0053] Fig.13 A simple schematic diagram of the RT-LAB experimental platform during the experimental verification of the embodiments of the present application.

[0054] FIG. 14( a ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under SPS control when P2 = 125 W and P3 = 122.5 W during the experimental verification of the embodiment of the present application.

[0055] FIG14( b ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under the optimized control strategy when P2=125W and P3=122.5W during the experimental verification of the embodiment of the present application.

[0056] FIG. 15( a ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under SPS control when P2 = 250 W and P3 = 122.5 W during the experimental verification of the embodiment of the present application.

[0057] FIG15( b ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under the optimized control strategy when P2=250W and P3=122.5W during the experimental verification of the embodiment of the present application.

[0058] FIG. 16( a ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under SPS control when P2 = 500 W and P3 = 122.5 W during the experimental verification of the embodiment of the present application.

[0059] FIG16( b ) is a schematic diagram of the experimental waveforms of the inductor current at port voltages 2 and 3 under the optimized control strategy when P2=500W and P3=122.5W during the experimental verification of the embodiment of the present application.

[0060] Fig.17 It is a schematic diagram of the reactive power curves under two control modes during the experimental verification of the embodiment of the present application. DETAILED DESCRIPTION

[0061] The embodiments of the present application are described in detail below with reference to the accompanying drawings; however, the present application can be implemented in many different ways as defined and covered by the claims.

[0062] Since the control strategy of TAB is optimized in the present application, in order to facilitate the understanding of the optimized control strategy of the present application, the working principle and loss analysis of the TAB converter, as well as the inventive concept of the present application, are briefly explained here.

[0063] TAB working principle:

[0064] like Figure 1 As shown in the figure, it is a three-port isolated bidirectional DC-DC converter based on three active bridges. This topology consists of three full bridges and a three-winding high-frequency transformer. The transformer winding ratio is N1:N2:N3, V1, V2, and V3 are the voltages on the DC side of the three ports, C1, C2, and C3 are the capacitors on the DC side of the three ports, and the square wave voltage of each H-bridge is V H1 、V H2 、V H3, L2 and L3 are the sum of the leakage inductance and external inductance of transformer port 2 and port 3 respectively. Port 1 is connected to the DC bus, and ports 2 and 3 are connected to the load. This paper defines the power flow direction output from port 1 as the positive direction, and the power flow direction input to the load as the positive direction. Define the voltage ratio k between ports 1 and 2 12 =N1 / N2, the voltage ratio of ports 1 and 3 is k 13 =N1 / N3. This paper analyzes the forward power transmission of TAB converter.

[0065] Under the SPS control strategy, the output power of each port is adjusted by controlling the phase shift angle between the output of each port of the isolated bidirectional DC-DC converter to the square wave voltage VH1, VH2, and VH3 on the transformer side. The waveform of TAB under SPS is as follows: Figure 3 As shown in the figure, it can be seen that the midpoint voltages VH1, VH2, and VH3 of the three H-bridges are all square waves with a duty cycle of 50%. and Two control degrees of freedom. is the phase shift angle between VH1 and VH2, is the phase shift angle between VH2 and VH3.

[0066] like Figure 2 As shown in Figure 1, the waveform of TAB under SPS control strategy. Since there are only two control degrees of freedom under SPS control, it is impossible to flexibly control the inductor current of the converter in each time period, resulting in a large reflux power inside the TAB converter, which in turn reduces the operating efficiency of the TAB converter under SPS control.

[0067] The addition of three internal phase shift angles will increase the number of variables, making the analysis and calculation process too complicated. Figure 3 As shown in the figure, this paper only discusses the addition of the internal phase shift angle α1 (i.e. S 11 With S 14 The phase shift between them).

[0068] Depend on Figure 3 It can be seen from the figure that after the inward shift phase α1 is introduced, the H-bridge midpoint voltage at port 1 is a three-level voltage, and the voltages at ports 2 and 3 are two-level voltages. is the internal phase shift angle of port 1, and is the phase shift angle between the H-bridges of port 1 and port 2, is the phase shift angle between the H-bridges at port 1 and port 3. is the phase shift angle duty ratio between port 1 and port 2 and port 3, and

[0069] The power loss is analyzed as follows:

[0070] TAB is suitable for high power density application scenarios. Its power loss is mainly composed of the conduction loss and switching loss of the power switch tube, the conduction loss and reverse recovery loss of the anti-parallel diode, and the copper loss and iron loss of the high-frequency transformer. The power loss of the switch tube includes transient loss and steady-state loss. For the convenience of analysis, the transient loss of the switch tube is small and can be ignored. This article only considers the conduction loss of the TAB converter switch tube. The conduction loss is related to the characteristics of the device and will also be affected by the current waveform. Since the magnetizing inductance of the high-frequency transformer is much larger than the leakage inductance, the leakage inductance can be ignored for the conduction loss of the switch tube. The conduction loss P of each switch tube of TAB in one cycle on It can be expressed as

[0071]

[0072] Where: R(on)i is the on-resistance of the switch tube in each H-bridge. Lrmsi are the effective values ​​of the inductor current at each port respectively.

[0073] The power loss of high-frequency transformer mainly includes copper loss and iron loss. Copper loss is caused by the resistance of transformer winding, and iron loss is caused by hysteresis and eddy current loss of transformer core. Since the iron loss of transformer and inductor is much smaller than the total loss, the iron loss of transformer and inductor can be ignored for the convenience of analysis. From formula (2), we can know the expression of copper loss:

[0074]

[0075] Among them, R T,i and R L,i are the resistance of each winding of the transformer and the internal resistance of the inductor. Based on equations (1)-(2), the total power loss of the TAB converter can be written as:

[0076] P tatol =P on +P Cu (3)

[0077] From formula (3), it can be seen that the total power loss of the TAB converter is proportional to the sum of the squares of the effective value of the inductor current. Therefore, the conduction loss of the switch tube and the copper loss of the transformer can be reduced by reducing the effective value of the inductor current at each port, thereby improving the working efficiency of the TAB. From formula (4), it can be seen that when the converter transmission power is constant, the reduction of reactive power indicates the reduction of the effective value of the inductor current. Therefore, the reactive power can be reduced by optimizing the fundamental circulating current, thereby reducing the effective value of the inductor current and improving the working efficiency of the converter.

[0078]

[0079] In order to solve the technical problems raised in the above background technology, Figure 1 and Figure 4 , to explain in detail the aspects proposed in this application. Figure 4 As shown, the present application proposes a control strategy optimization method based on fundamental wave circulation, which is applied to a three-active bridge DC-DC converter, wherein the three-active bridge DC-DC converter has three ports, including:

[0080] Step S1: collecting the midpoint voltage of each port in the three active bridge DC-DC converter;

[0081] The value of the midpoint voltage is critical to the control strategy of the converter. Especially in this paper based on model predictive control (MPC) or direct power control (DPC), the midpoint voltage is an important feedback quantity. Taking power balance as an example, when it is detected that the midpoint voltage of a port is too high or too low, the control system can adjust the switching action of the active bridge of the port, thereby adjusting the voltage and power output of the port to ensure that the converter can operate stably under different load conditions. This paper controls the converter based on model prediction, so it is necessary to first collect the midpoint voltage of each port in the three-active bridge DC-DC converter.

[0082] For ease of understanding, Figure 1 The full bridge on the left is defined as the first port, and in the upper and lower structures on the right, the full bridge located in the upper part is defined as the second port, and the full bridge located in the lower part is defined as the third port.

[0083] The midpoint voltage of each port collected here is Figure 1 V H1 、V H2 、V H3 For ease of understanding, V will be referred to in this article. H1 As the midpoint voltage of the first port, V H2 As the second port midpoint voltage, V H3 As the midpoint voltage of the third port. It should be noted that this article does not limit the specific method of collecting voltage.

[0084] Step S2: determining the phasor relationship between the midpoint voltage and the inductor current between the ports based on the midpoint voltage of each port;

[0085] As the degrees of freedom of TAB increase, the difficulty of time domain segmentation analysis of the model also increases. In order to solve this problem, this paper adopts the Fourier series decomposition method to transform the complex time domain analysis into a relatively easy frequency domain analysis, which greatly simplifies the calculation process of time domain analysis.

[0086] The collected midpoint voltages of each port are decomposed by Fourier series to determine the spectrum characteristics of the midpoint voltages of each port, as shown in formula (5):

[0087]

[0088] Where, angular frequency ω0 = 2πf, is the internal phase shift angle of port 1, is the phase shift angle between the H-bridges of port 1 and port 2, is the phase shift angle between the H-bridges at port 1 and port 3, V H1 (t) is the frequency spectrum characteristic of the midpoint voltage of the first port, V H2 (t) is the frequency spectrum characteristic of the midpoint voltage of the first port, V H2 (t) is the frequency spectrum characteristic of the midpoint voltage of the first port.

[0089] After obtaining the spectrum characteristics of the midpoint voltage of each port, the fundamental midpoint voltage of each port can be obtained by performing corresponding calculations on formula (5), as shown in formula (6). The fundamental midpoint voltage refers to the voltage value of the fundamental component at the midpoint of the circuit in a periodically changing voltage signal. The use of the fundamental midpoint for calculation is mainly based on the consideration of the fundamental component using Fourier transform, which can simplify the power calculation process under complex waveforms, and highlight the main contribution of the fundamental wave to power transmission and conversion, which is convenient for evaluating the core energy conversion process and basic performance and efficiency.

[0090]

[0091] In order to simplify the calculation, the present application adopts the phasor method for analysis. After obtaining the fundamental midpoint voltage of each port, that is, formula (6), the phasor form of the fundamental midpoint voltage of each port can be obtained, as shown in formula (7).

[0092]

[0093] In the formula, is the phasor form of the fundamental midpoint voltage of the first port, is the phasor form of the fundamental midpoint voltage at the second port, is the phasor form of the fundamental midpoint voltage of the third port, and V1, V2, and V3 are the voltages on the DC sides of the three ports.

[0094] The phasor form of the fundamental midpoint voltage of each port is to express the voltage value of the fundamental voltage (main component) at the midpoint of each port as a complex number, which contains amplitude and phase information. The phasor form can clearly express the phase difference between the fundamental voltage and current, which is very critical for analyzing important concepts such as power factor. The power factor is the ratio of active power to apparent power, which is equal to the cosine value of the phase difference between voltage and current. Through the phasor diagram or phasor expression, the size of the phase difference can be intuitively seen, and then the power factor can be accurately calculated to evaluate the energy utilization efficiency of the circuit.

[0095] According to formula (7), the fundamental midpoint voltage phasor expressions of the three ports are obtained, and then analyzed from the phasor aspect. Figure 5 As shown, the phasor relationship between the midpoint voltage and the inductor current between the first port and the second port and the third port can be obtained.

[0096] Step S3: determining the active power and reactive power of the second port, and the active power and reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductor current between the ports;

[0097] Depend on Figure 5 It can be seen that when the transformer is in a steady state, the voltage and current fundamental components between the first port and the second port and the third port have the following relationship:

[0098]

[0099] Where L2 and L3 are the sum of the leakage inductance and external inductance of the second and third ports of the transformer, respectively. is the phasor form of the fundamental midpoint current of the second port, is the phase form of the fundamental midpoint current of the third port, k 12 = N1 / N2 is the voltage ratio between the first port and the second port, k 13 =N1 / N3 is the voltage ratio between the first port and the third port.

[0100] That is to say, the present application can further determine the calculation relationship of the voltage and current fundamental components between the first port and the second port and the third port according to the phasor relationship between the midpoint voltage and the inductor current between the ports.

[0101] Then, based on the phasor form of the fundamental wave midpoint voltage of each port and the calculation relationship between the voltage and current fundamental wave components between the ports, the phasor expressions of the inductor currents of the second port and the third port are determined; wherein the second port and the third port shown are two ports among the ports;

[0102] According to formulas (7) and (8), the phasor expressions of the inductor currents at the second port and the third port can be obtained, as shown in formula (9):

[0103]

[0104] After obtaining the phasor form of the fundamental midpoint voltage of each port and the phasor expression of the inductor current of the second port and the third port, the active power P2 and reactive power Q2 of the second port, and the active power P3 and reactive power Q3 of the third port can be determined by complex power calculation, formula (10).

[0105]

[0106] Depend on Can get

[0107]

[0108] Step S4: Based on the active power and reactive power of the second port and the active power and reactive power of the third port, an optimized phase shift ratio combination is determined, and the optimized phase shift ratio combination is used to realize control of the three active bridge DC-DC converter.

[0109] In phase shift control, there are multiple phase shift angle combinations to achieve the specified power output, so it is necessary to combine the algorithm to find the optimal combination that minimizes the reactive power of the second port and the third port. According to the expressions of the active power P2 and P3 of the second port and the reactive power Q2 and Q3 of the second port and the third port, the sum of the reactive power of the second port and the reactive power of the third port Q 2，3 The minimum is used as the objective function, and the active power of the second port and the active power of the third port are used as constraints; the particle swarm algorithm is used to solve the objective function and obtain the corresponding shift ratio in the full power range. The sum of the reactive power of the second port and the reactive power of the third port Q 2，3 As shown in formula (13).

[0110]

[0111] The active power of the second port and the active power of the third port are used as constraint conditions, specifically:

[0112] According to formula (11) and formula (12), the maximum active power P of the third port is 3N =8V1V3 / π 2 L3k 13 The active powers P2 and P3 are normalized as the reference value to obtain the normalized value P2 of the active power of the second port. * And the per unit value of the active power at the third port P3 * , in order to facilitate analysis, the per-unit value of the active power of the second port P2 * And the per unit value of the active power at the third port P3 * as constraints for the objective function.

[0113]

[0114] This paper adopts the particle swarm algorithm to solve the objective function and obtain the corresponding shift ratio in the full power range, which is briefly explained here.

[0115] Particle swarm optimization (PSO) is an intelligent optimization method based on group collaboration, which simulates the foraging behavior of bird flocks to find the global optimal solution. Particle swarm algorithm is simple and easy to implement, has fast convergence speed, strong global search ability, strong parallel processing ability, and fewer parameters. Compared with other evolutionary algorithms (such as genetic algorithms), particle swarm algorithm requires fewer parameters to be adjusted, mainly including particle swarm size, learning factor, inertia weight, etc., which reduces the complexity and difficulty of parameter adjustment. Compared with other evolutionary algorithms (such as genetic algorithms), particle swarm algorithm requires fewer parameters to be adjusted, mainly including particle swarm size, learning factor, inertia weight, etc., which reduces the complexity and difficulty of parameter adjustment.

[0116] like Figure 6 As shown, it fully explains the process of solving the objective function using the particle swarm algorithm in this application. That is:

[0117] First, the population is initialized. A certain number of particles are randomly generated as the initial population. Each particle represents a potential solution to the problem and has two attributes: speed and position. Then the fitness value is calculated. According to the objective function of the problem and the constraints, the fitness value of each particle is calculated to evaluate its quality. Then the individual extreme value, global optimal value, particle speed and position are updated. According to the individual extreme value and global optimal value, as well as the preset learning factor and inertia weight and other parameters, the speed and position of each particle are updated. After calculating the particle objective function, the output test is whether it converges. If it converges, the optimal value is output. If it does not converge, it returns to the step of determining the global optimal particle and continues to iterate. The initialization parameters are shown in Table 1.

[0118] Table 1 Initial parameters of particle swarm algorithm

[0119]

[0120] like Figure 8 As shown in the figure, the implementation process of the output port (second port and third port) minimum reactive power optimization control strategy is described in detail. First, before the system control program runs, the particle swarm algorithm is used to find the optimal value and obtain the corresponding shift ratio α1 ( is the internal phase shift angle of port 1, and ). By detecting the difference between the output voltages of the second port and the third port and a given value (the given value is generally the rated voltage of the second port and the third port), the obtained values ​​are input into the PI controller to obtain the second phase shift ratio and the third phase shift ratio, wherein the second phase shift ratio is the phase shift angle duty ratio between the first port and the second port, and the third phase shift ratio is the phase shift angle duty ratio between the first port and the third port.

[0121] Then, the second shift phase is compared with the third shift phase and the corresponding shift phase within the full power range to determine an optimized shift phase combination, and the optimized shift phase combination is input into the PWM signal device to optimize the TAB control strategy.

[0122] It should be noted that the addition of three internal phase shift angles will increase the number of variables, making the analysis and calculation process too complicated. 11 With S 14 However, subsequent technical solutions, whether adding two inner phase shift angles or adding three inner phase shift angles, all fall within the protection scope of this application.

[0123] In some embodiments, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the processor implements the three-dimensional Gaussian-based incremental map optimization method provided in the first aspect.

[0124] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In a hardware implementation, the division between the functional blocks / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or may be implemented as hardware, or may be implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable storage medium, which may include a computer-readable storage medium (or a non-transitory medium) and a communication medium (or a temporary medium).

[0125] As is known to those of ordinary skill in the art, the term computer-readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). Computer-readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transmission mechanism, and may include any information delivery medium.

[0126] Exemplarily, the computer-readable storage medium may be an internal storage unit of the network management device described in the foregoing embodiment, such as a hard disk or memory of the network management device. The computer-readable storage medium may also be an external storage device of the network management device, such as a plug-in hard disk, a smart memory card (SmartMediaCard, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc., equipped on the network management device.

[0127] In some embodiments, a device is provided, including a processor and a memory, wherein the memory is used to store a computer program; the processor is used to execute the computer program and implement the three-dimensional Gaussian-based incremental map optimization method provided in the first aspect of the present application when executing the computer program.

[0128] It should be understood that the processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0129] The method of the present application is simulated and experimentally verified as follows. In order to avoid misunderstanding, in the following simulations and experimental verifications, port 1 is the first port mentioned above, port 2 is the second port mentioned above, and port 3 is the third port mentioned above. The optimization control is the control strategy optimization method proposed in the present application:

[0130] Simulation Verification

[0131] In order to verify the effectiveness of the mentioned minimum reactive power optimization control strategy, this section builds the SPS control strategy and minimum reactive power optimization control strategy simulation models of TAB based on the MATLAB / Simulink platform, and compares and analyzes the two control strategies. The main simulation parameters are shown in Table 2.

[0132]

[0133] Figure 8 The voltage waveforms of each port under two different control modes when P2=500W and P3=122.5W are given. Since the voltage control method is used for both port 2 and port 3 in the optimization control of this paper, only the voltage waveform when P2=500W and P3=122.5W is analyzed here. In this case, compared with SPS control, the optimization control has an additional inner phase shift angle at port 1, and α1=0.117.

[0134] Fig. 9 The output waveforms of port 2 and port 3 are given when the load mutation occurs at port 2. This paper further analyzes the effectiveness of the optimal control when the power of port 2 changes by analyzing the load mutation of the output port of port 2. Fig. 9 It can be seen that at 0.3S, the load of port 2 suddenly changes from 80Ω to 40Ω, and the current of port 2 suddenly changes from 1.25A to 2.5A. At 0.6S, the load of port 2 suddenly changes from 40Ω to 20Ω, and the current of port 2 suddenly changes from 2.5A to 5A. The output voltage of port 2 remains stable at 100V during the two load mutations. The output voltage and current of port 3 remain basically unchanged during the mutations.

[0135] Figure 10 shows the inductor current waveforms of port 2 and port 3 under two control modes when P2 = 125 W and P3 = 122.5 W. α1 = 0.0338 is calculated by the optimized control strategy.

[0136] Figure 11 shows the inductor current waveforms of port 2 and port 3 under two control modes when P2 = 250 W and P3 = 122.5 W. α1 = 0.0556 is calculated by the optimized control strategy.

[0137] Figure 12 shows the inductor current waveforms of port 2 and port 3 under two control modes when P2 = 500 W and P3 = 122.5 W. α1 = 0.117 is calculated by the optimized control strategy.

[0138] Experimental verification

[0139] In order to verify the correctness of the optimization control strategy proposed in this paper, this paper conducted experimental verification based on the RT-LAB experimental platform. Fig.13 shown.

[0140] Figure 14 shows the experimental waveforms of port 2 and port 3 under two control modes when P2 = 125W and P3 = 122.5W. It can be concluded from the experimental waveforms that under the SPS control strategy, the peak inductor current of port 2 is 8.35A, and the peak inductor current of port 3 is 9.43A. Under the optimized control strategy, the peak inductor current of port 2 is 7.91A, and the peak inductor current of port 3 is 9.3A.

[0141] Figure 15 shows the working experimental waveforms of port 2 and port 3 under two control modes when P2 = 250W and P3 = 122.5W. It can be concluded from the experimental waveforms that under the SPS control strategy, the inductor current peak value of port 2 is 8.9A, and the inductor current peak value of port 3 is 9.95A. Under the optimized control strategy, the inductor current peak value of port 2 is 8.25A, and the inductor current peak value of port 3 is 9.8A.

[0142] Figure 16 shows the working experimental waveforms of port 2 and port 3 under two control modes when P2 = 500W and P3 = 122.5W. It can be concluded from the experimental waveforms that under the SPS control strategy, the inductor current peak value of port 2 is 12.23A, and the inductor current peak value of port 3 is 12.3A. Under the optimized control strategy, the inductor current peak value of port 2 is 10.15A, and the inductor current peak value of port 3 is 10.03A.

[0143] As shown in Figures 14, 15, and 16, the simulated theoretical waveforms are basically consistent with the experimental waveforms, indicating that the TAB converter has certain practicality under the optimization control strategy proposed in this paper. The peak value of the inductor current under the optimization control strategy is smaller than that under the SPS control strategy, indicating that the optimization control strategy effectively reduces the effective value of the inductor current and the current stress. When the output power of ports 2 and 3 is constant, the reduction in the effective value of the current indicates a reduction in power loss (1.2 Power loss analysis), and the reactive power is also reduced accordingly, which improves the system efficiency and verifies the effectiveness of the optimization control strategy.

[0144] Fig.17The reactive power curves under the two control modes are given. From the graph, it can be seen that under light load conditions, the effect of the fundamental circulating current optimization control strategy is more obvious. This shows that the optimization control strategy has a significant effect on reducing reactive power and improves the operating conditions of the TAB converter.

[0145] In summary, this application calculates the inductor current, active power and reactive power of TAB under the optimized control strategy based on Fourier series decomposition and phasor analysis, and constructs a TAB mathematical model, thereby avoiding the complexity of the traditional time domain analysis method and simplifying the calculation. The PSO algorithm is used to solve the model, and the fundamental circulation current of the output section is optimized by analyzing the different output powers. The particle swarm algorithm is used to not only reduce the complexity of the mathematical model, but also solve the problem that the optimal solution cannot be obtained due to multivariable and nonlinear constraints. Thereby, in the case of forward power transmission, the optimized control strategy proposed in this application can effectively reduce the reactive power of TAB, which is more obvious under light load conditions, and improves the system operation efficiency.

[0146] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control strategy optimization method based on fundamental circulation is applied to a three-active-bridge DC-DC converter, wherein the three-active-bridge DC-DC converter has three ports and is characterized in that: include: Collecting the midpoint voltage of each port in the three active bridge DC-DC converter; Based on the midpoint voltages of the ports, determining the phasor relationship between the midpoint voltages and the inductor current between the ports; Determine the active power and reactive power of the second port and the active power and reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductor current between the ports; Based on the active power and reactive power of the second port and the active power and reactive power of the third port, an optimized phase shift combination is determined, and the optimized phase shift combination is used to realize control of the three active bridge DC-DC converter.

2. The method according to claim 1, characterized in that The determining the phasor relationship between the midpoint voltage and the inductor current between the ports based on the midpoint voltage of each port includes: Performing Fourier series decomposition on the midpoint voltage of each port to determine the frequency spectrum characteristics of the midpoint voltage of each port; Determining the fundamental wave midpoint voltage of each port based on the frequency spectrum characteristics of the midpoint voltage of each port; Based on the determination of the fundamental wave midpoint voltage of each port; determining the phasor form of the fundamental wave midpoint voltage of each port; Based on the phasor form of the fundamental wave midpoint voltage of each port, the phasor relationship between the midpoint voltage and the inductor current between each port is determined.

3. The method according to claim 2, characterized in that The determining of the active power and reactive power of the second port and the active power and reactive power of the third port based on the phasor relationship between the midpoint voltage and the inductor current of the ports comprises: Determining the calculation relationship of the voltage and current fundamental components between the ports based on the phasor relationship between the midpoint voltage and the inductor current between the ports; Based on the phasor form of the fundamental wave midpoint voltage of each port and the calculation relationship between the voltage and current fundamental wave components between the ports, the phasor expressions of the inductor currents of the second port and the third port are determined; wherein the second port and the third port are two ports among the ports; Based on the phasor form of the fundamental midpoint voltage of each port and the phasor expression of the inductor current of the second port and the third port, the active power and reactive power of the second port and the active power and reactive power of the third port are determined.

4. The method according to claim 3, characterized in that The step of determining an optimized shift ratio combination based on the active power and reactive power of the second port and the active power and reactive power of the third port comprises: Taking the minimum sum of the reactive power of the second port and the reactive power of the third port as the objective function; Taking the active power of the second port and the active power of the third port as constraint conditions; The objective function is solved by using a particle swarm algorithm to obtain the corresponding shift ratio within the full power range; Obtaining output voltages of the second port and the third port; An optimized shift phase combination is determined based on the output voltages of the second port and the third port and corresponding shift phase ratios within the full power range.

5. The method according to claim 4, characterized in that The taking the active power of the second port and the active power of the third port as constraint conditions comprises: Taking the maximum value of the active power of the third port as a reference, normalizing the active power of the second port and the active power of the third port to obtain a per-unit value of the active power of the second port and a per-unit value of the active power of the third port; Taking the per-unit value of the active power of the second port and the per-unit value of the active power of the third port as constraint conditions; 6. The method according to claim 4, characterized in that The step of determining an optimized shift phase combination based on the output voltages of the second port and the third port and the corresponding shift phases within the full power range comprises: The output voltages of the second port and the third port are respectively subtracted from a given value, and then a second phase shift ratio and a third phase shift ratio are obtained after a PI controller; wherein the second phase shift ratio is a phase shift angle duty ratio between the first port and the second port, and the third phase shift ratio is a phase shift angle duty ratio between the first port and the third port; Based on the second shift phase ratio and the third shift phase ratio, and the corresponding shift phase ratio within the full power range, an optimized shift phase combination is determined.

7. A computer device, characterized in that: The computer device includes a processor and a memory, wherein the memory stores at least one instruction, at least one program, a code set or an instruction set, and the at least one instruction, at least one program, a code set or an instruction set is loaded and executed by the processor to implement the control strategy optimization method based on fundamental circulating current as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that: The readable storage medium stores at least one instruction, at least one program, code set or instruction set, and the at least one instruction, at least one program, code set or instruction set is loaded and executed by a processor to implement the control strategy optimization method based on fundamental circulation as described in any one of claims 1 to 6.

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