Four-port energy router impedance modeling method considering external characteristics of ports

Abstract

The invention discloses a four-port energy router impedance modeling method considering port external characteristics, and the method comprises the steps: constructing a magnetic network energy router frequency domain small signal model containing bus voltage disturbance and control loop dynamics, and building an equivalent circuit of each port sub-network; taking the equivalent impedance of the port sub-network as an additional element, and removing the influence of the additional element to obtain an energy router port impedance model in an ideal operation state without considering the external characteristics of the sub-network; adding the additional element to the corresponding port sub-network of the energy router successively to form a new equivalent circuit, calculating the driving point impedance and the zero driving impedance of the additional element, and further obtaining a correction factor of the corresponding port sub-network of the additional element to the impedance model in a general operation state; the influence of each port sub-network on the system impedance model is included in the model by using the correction factor of each additional element, so that the energy router impedance model considering the external characteristics of the full-port sub-network is obtained, the modeling calculation is simplified, and the accuracy of the system model is improved.

Description

Technical Field

[0001] The present invention relates to an impedance modeling method for a four-port energy router considering the external characteristics of ports, belonging to the technical field of isolated power electronic converters. Background Art

[0002] The magnetic network energy router integrates a multi-port power electronic converter and a high-power magnetic coupling transformer, which can flexibly configure the DC bus voltage levels of ports, fully compatible with the access requirements of various forms of power sources, loads, and energy storage devices. At the same time, its isolated structure can achieve efficient electromagnetic isolation between ports, significantly improving the operating efficiency, power supply reliability, and system power density in the operating scenarios of new power systems, showing important engineering practice value in microgrid systems and integrated energy systems.

[0003] However, the magnetic network energy router has multiple ports and the characteristic of high power coupling between ports, resulting in very complex interactions between the sub-networks of each port of the energy router. Using the traditional impedance analysis method to establish a model is computationally complex and difficult to accurately describe the coupling characteristics of the multi-port system. Ignoring the external characteristics of the port sub-network will lead to significant deviations in the analysis of the system impedance model and operating characteristics. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an impedance modeling method for a four-port energy router considering the external characteristics of ports. By solving the correction parameters of the additional components to the system under special working conditions, the impedance model of the system considering the influence of the additional components under general operating conditions is obtained, reducing the difficulty of system modeling and providing a theoretical support for analyzing the operating stability of the system.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] An impedance modeling method for a four-port energy router considering the external characteristics of ports. The four-port energy router includes a four-winding transformer and the first to fourth full-bridge converters. The four-port energy router controls each full-bridge converter through a single-phase-shift control strategy with voltage closed-loop to achieve constant bus voltages at the second to fourth ports. The first to fourth full-bridge converters utilize the magnetic coupling effect of the four-winding transformer to achieve power transmission between ports. The method includes the following steps:

[0007] Step 1, establish the equivalent circuits of the sub-networks of each port of the four-port energy router, and considering the disturbances of the bus voltages and phase-shift control signals of the energy router ports, construct a small-signal model of the four-port energy router in the frequency domain;

[0008] Step 2: Take the equivalent impedance in the equivalent circuit of each port sub-network as an additional element, remove the influence of all additional elements, and calculate the impedance model of the i-th port under the ideal operating state without considering the external characteristics of the sub-network, where i = 1, 2, 3, 4;

[0009] Step 3: Add additional elements to the corresponding ports of the four-port energy router one by one. For each added additional element, solve the new equivalent circuit formed after adding the current additional element to obtain the driving-point impedance and zero-driving impedance of the current additional element, and then obtain the impedance correction factor of the impedance model of the sub-network corresponding to the current additional element for the i-th port under general operating conditions;

[0010] Step 4: Based on the additional element theorem, integrate the impedance correction factors of all port sub-networks obtained in Step 3 into the impedance model of the i-th port under the ideal operating state without considering the external characteristics of the sub-network, so as to obtain the impedance model of the energy router considering the coupling of the external characteristics of all port sub-networks.

[0011] Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects:

[0012] 1. Based on the additional element theorem, the present invention adopts a systematic method to simplify the analysis of complex networks by introducing additional elements, and gradually introduces the influence of the external characteristics of the port sub-network into the system impedance model to gradually correct the model to obtain an accurate and effective impedance model of the energy router. At the same time, the modeling method of obtaining the correction parameters of the system under the general operating state by solving the system parameters under special operating conditions can effectively reduce the modeling difficulty.

[0013] 2. The present invention gradually superimposes the influence of the actual equivalent impedance of the sub-network on the system on the ideal model without equivalent impedance of the sub-network by introducing additional elements, and avoids the problem of excessive calculation amount and difficult solution caused by the increase of matrix dimension in the traditional method when analyzing a multi-port energy router through step-by-step processing, effectively reducing the complexity of model establishment.

[0014] 3. The present invention regards the external characteristics of the sub-network as flexible and variable additional elements, updates the system impedance model according to the actual operating conditions without re-solving the system, realizes the analysis of the influence of the difference in the operating characteristics of the sub-network on the system operating state, and improves the practicability of the system model.

[0015] 4. The present invention realizes the separation of the core model and the influence of additional elements through a modular modeling method, avoids complex formula derivation compared with the analysis method based on transfer functions, and more directly correlates the changes in physical quantities in the system with the impedance characteristics of the system, enhancing the interpretability of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is the main circuit and control circuit model of the energy router system of the present invention;

[0017] Figure 2 It is the schematic diagram of the small-signal model of the energy router of the present invention;

[0018] Figure 3 It is the schematic diagram of the circuit for calculating the driving-point impedance and zero-driving impedance of the additional element of the present invention. Among them, (a) is the driving-point impedance and (b) is the zero-driving impedance;

[0019] Figure 4 It is the schematic diagram of the swept-frequency result of the load-port impedance model of the energy router of the present invention. Detailed implementation manners

[0020] The following details the implementation manners of the present invention. The examples of the implementation manners are shown in the accompanying drawings. The implementation manners described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0021] Figure 1 Shown is the system topology structure and control circuit of the four-port magnetic network energy router. The four-port magnetic network energy router includes a four-winding transformer and four full-bridge converters. The four-port energy router controls each full-bridge converter through a single-phase-shift control strategy with voltage closed-loop to achieve constant bus voltages at the second to fourth ports. The first to fourth full-bridge converters utilize the magnetic coupling effect of the four-winding transformer to achieve power transmission between ports. The port 1 sub-network uses a Thevenin equivalent circuit with an ideal voltage source and an equivalent impedance in series to simulate the external characteristics of the power sub-network, and the ports 2 to 4 use a Norton equivalent circuit with an ideal current source and an equivalent impedance in parallel to simulate the external characteristics of the load sub-network.

[0022] The present invention provides a method for impedance modeling of a four-port magnetic network energy router considering the external characteristics of port sub-networks, including the following steps:

[0023] S1. Considering the disturbances of the bus voltages and control signals of the energy router ports, construct a small-signal model of the energy router system adopting voltage-loop phase-shift control in the frequency domain;

[0024] Assume that each port is reduced to port 1. Then, according to the operating characteristics of the magnetic network energy router, the average value of the port current within the switching period can be obtained as:

[0025]

[0026] Among them, L ij is the equivalent link inductance between ports i and j, n i is the number of turns of the transformer at port i, f s is the switching frequency of the full-bridge converter, V iis the bus voltage of port i, φ ij is the phase difference between port i and port j, d ij = φ ij / π.

[0027] Based on the expression of port current, the perturbation signals considering the bus voltage and control signal are obtained Figure 2 The small-signal model of the four-port magnetic network energy router system and the control loop shown below is as follows:

[0028]

[0029] Among them, are the perturbation signals corresponding to the current, voltage of port i, and the phase-shift angle of the drive signal between port i and port 1, respectively. G PI2 、G PI3 、G PI4 are all controller transfer functions in the loop. Define the variable Then the expressions of each element in the above matrix are:

[0030]

[0031] Among them, the superscript on the horizontal line represents the steady-state value of the corresponding variable.

[0032] S2. Take the equivalent impedance of each port sub-network as an additional element, remove the influence of all additional elements in the system, and calculate the frequency-domain expression Z Li (s) of the impedance of port i of the system in the ideal operating state without considering the external characteristics of the sub-network;

[0033] Take the equivalent impedance of the sub-network as an additional element of the system. By removing the influence of the equivalent impedance of the sub-network, the equivalent circuit of the system in the ideal operating condition can be obtained. The parametric limit method can be used to eliminate its coupling effect on the system. There are two specific implementation methods: increasing or decreasing the modulus value of the additional element to make it tend to infinity or 0, which is equivalent to performing an open-circuit or short-circuit treatment on the port where the additional element is located for the additional element. Usually, for the Thevenin equivalent circuit, the additional element can be made to tend to 0, while for the Norton equivalent circuit, the additional element can be made to tend to infinity, so as to eliminate the non-ideal characteristics of the voltage source or current source in the equivalent circuit.

[0034] After removing all additional elements in the system, calculate the ratio of the voltage perturbation signal to the current perturbation signal at the common connection point between the bus of the port whose impedance is to be calculated and the sub-network, and the obtained frequency-domain transfer function is the impedance Z Li (s) expression of the energy router neglecting the external characteristics of the sub-network.

[0035] S3. Add the additional elements to the corresponding ports of the energy router one by one, and solve the driving-point impedance Z D(s) and zero driving impedance Z N (s), and then obtain the impedance correction factor of the impedance model of the port sub-network corresponding to the current additional element for port i under general working conditions;

[0036] Add additional elements to the system one by one to form a new equivalent circuit. By solving the driving point impedance and zero driving impedance of the additional element in the newly formed equivalent circuit under special working conditions, obtain the impedance correction factor for port i under general working conditions after adding the additional element, which is used to account for the influence of the external characteristics of the sub-network corresponding to the additional element on the system impedance model. According to the two treatment methods of short-circuiting or opening the additional element corresponding to the port when removing the port additional element, the expression forms of the correction factor are respectively:

[0037]

[0038] Among them, Z D , Z N are respectively the driving point impedance and zero driving impedance of the additional element for the impedance model to be solved.

[0039] For the Thevenin equivalent circuit, when the additional element is short-circuited, the correction factor in the form of H 1 (s) can be used, while for the Norton equivalent circuit when it is open-circuited, the correction factor in the form of H 2 (s) is used. That is, the impedance correction factor H1(s) of the impedance model of the first port sub-network for port i under general working conditions is:

[0040]

[0041] Among them, Z1(s) is the equivalent impedance in the equivalent circuit of the first port sub-network, and Z 1_D (s), Z 1_N (s) are respectively the driving point impedance and zero driving impedance of the impedance model of the first port sub-network for the i-th port;

[0042] The impedance correction factors of the impedance models of the second, third, and fourth port sub-networks for the i-th port under general working conditions are respectively:

[0043]

[0044] Among them, Z2(s), Z3(s), and Z4(s) are respectively the equivalent impedances in the equivalent circuits of the second, third, and fourth port sub-networks; Z 2_D (s), Z 2_N (s) are respectively the driving point impedance and zero driving impedance of the impedance model of the second port sub-network for the i-th port; Z 3_D (s), Z 3_N(s) are the driving-point impedance and zero-drive impedance of the third-port sub-network with respect to the impedance model of the i-th port; Z 4_D (s), Z 4_N (s) are the driving-point impedance and zero-drive impedance of the fourth-port sub-network with respect to the impedance model of the i-th port.

[0045] To solve the correction factor, two special operating conditions need to be selected to calculate the equivalent impedance observed by the system from the additional port, corresponding to the driving-point impedance Z D (s) and the zero-drive impedance Z N (s). Replace the additional element with a current source to form a new equivalent circuit. The ratio of the voltage perturbation signal at both ends of the current source to the output current perturbation signal is the equivalent impedance observed from the additional element. Set the current perturbation signal flowing through the equivalent circuit of the sub-network at the impedance port i to be solved to 0, and calculate the equivalent impedance observed from the additional element at this time, which is the driving-point impedance Z D (s); by adjusting the output current perturbation signal of the current source replacing the additional element, the equivalent impedance observed from the additional element when the output voltage perturbation signal of the equivalent circuit of the sub-network at the impedance port to be solved is 0 is the zero-drive point impedance Z N (s), as shown in Figure 3 (a) and (b).

[0046] It should be noted that when an additional element is added to the corresponding port, when forming the equivalent circuit of subsequent other additional elements to solve the driving-point impedance and zero-drive point impedance, the added additional element does not need to be removed.

[0047] S4. After gradually calculating the correction factors corresponding to the additional elements of all ports, based on the additional element theorem, integrate all the correction factors into the ideal system impedance Z Li (s) that does not consider the external characteristics of the sub-network, so as to obtain the impedance model Z Li_c (s) of the energy router considering the coupling of the external characteristics of all-port sub-networks;

[0048] Integrate the correction parameters corresponding to all accessory elements based on the additional element theorem. The influence of the external characteristics of each port sub-network on the impedance model of the energy router is incorporated into the system impedance model through the correction factor, so as to obtain the accurate impedance model of the energy router system considering the external characteristics of all-port sub-networks as follows:

[0049]

[0050] Figure 4It is the swept frequency result of the impedance model of the load port of the energy router. Due to the coupling of switch ripple and the aliasing of discrete sampling, errors occur in the output impedance scanning result near the switch frequency of 10 kHz of the energy router. Generally, the theoretical calculation result is in good agreement with the simulation experiment scanning result, which proves the correctness of the established impedance model of the energy router.

[0051] Based on the same inventive concept, an embodiment of the present application provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the foregoing four-port energy router impedance modeling method considering the external characteristics of the port are implemented.

[0052] Based on the same inventive concept, an embodiment of the present application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the foregoing four-port energy router impedance modeling method considering the external characteristics of the port are implemented.

[0053] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can be in the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can be in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0055] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the specified functions in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0056] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so as to cause a series of operation steps to be executed on the computer or other programmable apparatus to generate a computer-implemented process, thereby the instructions executed on the computer or other programmable apparatus provide steps for realizing the functions specified in one process or multiple processes and / or one block or multiple blocks in the flow Figure 1 one process or multiple processes and / or Figure 1 steps for realizing the functions specified in one block or multiple blocks.

[0057] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

Claims

1. A method for impedance modeling of a four-port energy router considering external port characteristics. The four-port energy router includes a four-winding transformer and first to fourth full-bridge converters. The four-port energy router controls each full-bridge converter through a single-phase-shift control strategy with voltage closed-loop to achieve constant bus voltages at the second to fourth ports. The first to fourth full-bridge converters utilize the magnetic coupling effect of the four-winding transformer to achieve power transfer between ports. It is characterized in that It includes the following steps: Step 1: Establish the equivalent circuits of the sub-networks of each port of the four-port energy router. Considering the disturbances of the bus voltages and phase-shifting control signals at the ports of the energy router, construct a small-signal model of the four-port energy router in the frequency domain; Step 2: Take the equivalent impedances in the equivalent circuits of the sub-networks of each port as additional elements, remove the influences of all additional elements, and calculate the impedance model of the i-th port (i = 1, 2, 3, 4) under the ideal operating state without considering the external characteristics of the sub-networks; Step 3: Add the additional elements to the corresponding ports of the four-port energy router one by one. For each added additional element, solve the new equivalent circuit formed after adding the current additional element to obtain the driving-point impedance and zero-driving impedance of the current additional element, and then obtain the impedance correction factor of the sub-network corresponding to the current additional element for the i-th port under general operating conditions; Step 4: Based on the additional element theorem, integrate the impedance correction factors of all port sub-networks obtained in Step 3 into the impedance model of the i-th port under the ideal operating state without considering the external characteristics of the sub-networks, so as to obtain the impedance model of the energy router considering the coupling of the external characteristics of all port sub-networks.

2. The impedance modeling method of the four-port energy router considering the external characteristics of ports according to claim 1, wherein The specific process of Step 1 is as follows: Define the first-port sub-network of the four-port energy router as the power sub-network, and the second to fourth-port sub-networks as load sub-networks. Use the Thevenin equivalent circuit with an ideal voltage source in series with an equivalent impedance to simulate the external characteristics of the power sub-network, and use the Norton equivalent circuit with an ideal current source in parallel with an equivalent impedance to simulate the external characteristics of the load sub-networks; Reduce the parameters of other ports to the first port, then according to the operating characteristics of the four-port energy router, the average values of the currents at each port within the switching period are: Wherein, I j is the average current of the j-th port during the switching period, n1 is the number of turns of the transformer of the first port, V i is the bus voltage of the i-th port, n i is the number of turns of the transformer of the i-th port, f s is the switching frequency of each full-bridge converter, L ij is the equivalent link inductance between the i-th and j-th ports, d ij = φ ij / π, φ ij is the phase difference between the i-th port and the j-th port; Based on the average values of the currents at each port within the switching period, considering the disturbance signals of the bus voltage and phase-shifting control signal, the small-signal model of the four-port energy router and the control loop is as follows: wherein, are respectively the disturbance signals corresponding to the current and voltage of the i-th port, is the disturbance signal corresponding to the phase shift angle of the driving signal between the i-th port and the first port, G PI2 、G PI3 、G PI4 are all controller transfer functions in the loop; Define variables are d respectively 1i , d 1j is the steady-state value, then the expressions for each element in the model are as follows: Among them, is the steady-state value of V i .

3. The impedance modeling method of the four-port energy router considering external port characteristics according to claim 2, characterized in that The specific process of Step 2 is as follows: Make the equivalent impedance in the equivalent circuit of the first port sub-network, i.e., the modulus value of the additional element, tend to 0, and at the same time make the equivalent impedances in the equivalent circuits of the second to fourth port sub-networks, i.e., the modulus values of the additional elements, all tend to infinity. Calculate the ratio of the voltage disturbance signal to the current disturbance signal at the common connection point between the bus of the i-th port and the sub-network. The obtained frequency-domain transfer function is the impedance model Z Li (s) of the i-th port of the energy router ignoring the external characteristics of the sub-network.

4. The impedance modeling method of the four-port energy router considering the external characteristics of ports according to claim 3, characterized in that In Step 3, if the current additional element is the equivalent impedance in the equivalent circuit of the first-port sub-network, the impedance correction factor H1(s) of the first-port sub-network for the impedance model of the i-th port under general operating conditions is: Among them, Z1(s) is the equivalent impedance in the equivalent circuit of the first port sub-network, Z 1_D (s), Z 1_N (s) are respectively the driving-point impedance and the zero-drive impedance of the impedance model of the first port sub-network for the i-th port; If the current additional element is the equivalent impedance in the equivalent circuits of the second, third, or fourth-port sub-networks, the impedance correction factors of the second, third, and fourth-port sub-networks for the impedance model of the i-th port under general operating conditions are respectively: Among them, H2(s), H3(s), and H4(s) are the impedance correction factors of the impedance models of the second, third, and fourth port sub-networks with respect to the i-th port under normal operating conditions, respectively, and Z2(s), Z3(s), and Z4(s) are the equivalent impedances in the equivalent circuits of the second, third, and fourth port sub-networks; Z 2_D (s), Z 2_N (s) are the driving-point impedance and zero-driving impedance of the impedance model of the second port sub-network with respect to the i-th port, respectively; Z 3_D (s), Z 3_N (s) are the driving-point impedance and zero-driving impedance of the impedance model of the third port sub-network with respect to the i-th port, respectively; Z 4_D (s), Z 4_N (s) are the driving-point impedance and zero-driving impedance of the impedance model of the fourth port sub-network with respect to the i-th port, respectively; By setting the disturbance quantity of the current flowing through the equivalent circuit of the i-th port sub-network to 0, calculate the equivalent impedance observed from the current additional element at this time, which is the driving-point impedance; make the disturbance quantity of the output voltage of the i-th port sub-network 0, and the equivalent impedance observed from the current additional element is the zero-driving impedance; When the additional element is added to the corresponding port, when forming the equivalent circuits of subsequent other additional elements to solve the driving-point impedance and zero-driving impedance, it is not necessary to remove the added additional elements.

5. The impedance modeling method of the four-port energy router considering external port characteristics according to claim 4, characterized in that In Step 4, the impedance model of the energy router considering the coupling of the external characteristics of all port sub-networks is as follows: Among them, Z Li_c (s) is the impedance model of the energy router that takes into account the coupling of the external characteristics of all port sub-networks.

6. A computer device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, When the processor executes the computer program, the steps of the impedance modeling method for a four-port energy router considering external port characteristics as described in any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, the steps of the impedance modeling method for a four-port energy router considering external port characteristics as described in any one of claims 1 to 5 are implemented.

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