Modularized expandable low-voltage transformer area micro-grid integrated interface device

Abstract

The invention relates to a modular expandable low-voltage transformer area micro-grid integrated interface device. The device comprises a common low-voltage high-frequency AC bus; the alternating current end of the AC / DC module serves as a transformer area grid-connected port to be connected with an alternating current distribution line of a transformer area, and the direct current end of the AC / DC module is connected with the common low-voltage high-frequency alternating current bus through the IPOP-H module; the direct current end of the DC / AC module is connected with the common low-voltage high-frequency alternating current bus through the IPOP-H module, and the alternating current end of the DC / AC module serves as an alternating current micro-grid port to be connected with an agricultural alternating current micro-grid; the first DC end of the DC / DC module is connected with the common low-voltage high-frequency AC bus through the IPOP-H module, and the second DC end of the DC / DC module is used as a DC micro-grid port to be connected with the optical storage and charging DC micro-grid; and the central controller is used for controlling the AC / DC module, the DC / AC module and the DC / DC module so as to realize bidirectional energy scheduling between microgrids. According to the invention, the consumption capability of the whole rural low-voltage transformer area micro-grid system on rural micro-grids with different power capacities and different energy types can be improved, and the autonomous operation capability of the rural micro-grids is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic conversion, and in particular to a modular and expandable low-voltage station area microgrid integrated interface device. Background Art

[0002] The types of distributed energy generation in rural microgrids are becoming more and more abundant, and the differences in randomness, seasonality, etc. of different types of distributed energy generation are becoming increasingly obvious. This requires the future development of rural microgrids in terms of expanding power capacity and diversifying structures. However, the existing rural microgrids have a single structure and limited power capacity, which cannot meet the needs of large-scale access to various types of distributed energy in rural areas. In response to the problem that the existing rural microgrids are insufficient in absorbing large-scale and multi-type distributed energy, some scholars have proposed an "energy Internet" system that can coordinate the energy complementarity and efficient energy management between "microgrid power generation units of different types of distributed energy".

[0003] In the energy Internet system, the energy router is the core device for interconnecting different energy sources. It can combine the current distributed energy generation and power load demand in rural microgrids, autonomously allocate the proportion of each energy generation, and realize the energy complementarity and information exchange of rural microgrids with different energy types. The energy router greatly improves the rural microgrid's ability to absorb large-scale and multi-type distributed energy.

[0004] At present, microgrid integrated interface devices are mainly divided into two categories in terms of topological structure. One is a microgrid integrated interface device based on a multi-port converter structure, and the other is a microgrid integrated interface device using a solid-state transformer structure. Among them, the topology of the microgrid integrated interface device based on the solid-state transformer structure mainly achieves the purpose of high-frequency conversion of electric energy by combining power electronic conversion technology and electromagnetic induction technology. Compared with the microgrid integrated interface device with a multi-port converter structure, it has obvious advantages in accessing rural microgrids where distributed energy is relatively concentrated. For example, the microgrid integrated interface device based on the solid-state transformer structure has some functions that are difficult to achieve with the microgrid integrated interface device with a traditional transformer structure. These functions mainly include power coordination between microgrids, microgrid voltage and frequency support, fault current limiting protection, and microgrid autonomous operation.

[0005] The existing integrated microgrid interface device still has certain defects in topological design. The defects are specifically manifested in that it is difficult to meet the needs of large-scale access to rural microgrids with different power capacities and multiple energy types, it is difficult to achieve energy complementarity between rural microgrids with different energy types, and it is difficult to reduce the dependence of rural microgrids on distribution networks, resulting in weak autonomous operation capabilities of rural microgrids. In addition, in the face of the uncertainty caused by the randomness and seasonality of different types of distributed energy generation in rural areas, the existing integrated microgrid interface device topology cannot effectively avoid it. Summary of the invention

[0006] The present invention provides a modular and expandable low-voltage substation microgrid integrated interface device, which can improve the absorption capacity of the entire rural low-voltage substation microgrid system for rural microgrids with different power capacities and different energy types, and also realizes two-way energy dispatch between rural microgrids with different energy types, which to a certain extent reduces the dependence of rural microgrids on distribution networks and improves the autonomous operation capability of rural microgrids.

[0007] The technical solution adopted by the present invention to solve the technical problem is: to provide a modular and expandable low-voltage area microgrid integrated interface device, including:

[0008] Public low-voltage high-frequency AC bus;

[0009] AC / DC module, the AC end is connected to the AC distribution line of the substation as the substation grid-connected port, and the DC end is connected to the public low-voltage and high-frequency AC bus through the IPOP-H module; the AC / DC module is used to connect the substation distribution network with the microgrid integrated interface device;

[0010] A DC / AC module, wherein the DC end is connected to the common low-voltage high-frequency AC busbar through an IPOP-H module, and the AC end is connected to the agricultural AC microgrid as an AC microgrid port; the DC / AC module is used to enable various distributed energy sources in the agricultural AC microgrid to receive unified dispatching from the microgrid integrated interface device;

[0011] A DC / DC module, wherein the first DC end is connected to the common low-voltage high-frequency AC bus through an IPOP-H module, and the second DC end is connected to the photovoltaic storage and charging DC microgrid as a DC microgrid port; the DC / DC module is used to enable various DC micro-sources and DC loads in the photovoltaic storage and charging DC microgrid to receive unified dispatching from the microgrid integrated interface device;

[0012] The central controller is connected to the AC / DC module, the DC / AC module and the DC / DC module respectively through signal lines, and is used to control the AC / DC module, the DC / AC module and the DC / DC module to achieve two-way energy scheduling between microgrids.

[0013] The IPOP-H module includes n H full-bridge circuits, and the n H full-bridge circuits are connected using IPOP, wherein n is a positive integer greater than 1.

[0014] The power formula of the IPOP-H module is: dc I dc =U1I1+U2I2+…+U n I n , where U dc I dc is the input power of the IPOP-H module, U1I1 is the input power of the first H full-bridge circuit in the IPOP-H module, U2I2 is the input power of the second H full-bridge circuit in the IPOP-H module, and U n I n is the input power of the nth H full-bridge circuit in the IPOP-H module.

[0015] The AC / DC module is a VSC power conversion circuit.

[0016] The DC / AC module is a VSC power conversion circuit.

[0017] The DC / DC module is a three-level in-phase Buck-Boost conversion circuit.

[0018] A high-frequency transformer is also provided between the IPOP-H module and the common low-voltage high-frequency AC bus.

[0019] Beneficial Effects

[0020] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention realizes the interconnection and bidirectional dispatch of rural microgrids with different energy forms such as rural DC microgrids and rural AC microgrids through an expandable public low-voltage high-frequency AC bus, thereby improving the autonomous operation capability of the entire rural microgrid system and the overall absorption capacity of the rural microgrid system for various distributed energy sources. The present invention also modularizes multiple H full-bridge circuits and adopts an IPOP connection structure to form an IPOP-H module, which can not only meet the access requirements of rural microgrids with different power capacities, but also the IPOP connection structure simplifies the problem of current sharing control of switch tubes. In addition, the present invention also uses a high-frequency transformer to achieve electrical isolation of the microgrid system, ensuring that rural microgrids with multiple energy types are safely and stably connected to the microgrid integrated interface device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an application scenario diagram of a modular and expandable low-voltage area microgrid integrated interface device according to an embodiment of the present invention;

[0022] Figure 2 It is a system structure diagram of a modular and expandable low-voltage area microgrid integrated interface device according to an embodiment of the present invention;

[0023] Figure 3 It is a topological structure diagram of a modular and expandable low-voltage area microgrid integrated interface device according to an embodiment of the present invention;

[0024] Figure 4 It is a topological structure diagram of the expandable low-voltage substation microgrid integrated interface device in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0026] The embodiment of the present invention relates to a modular and expandable low-voltage area microgrid integrated interface device, the application scenario of the microgrid integrated interface device is as follows: Figure 1 As shown, it is mainly used for the access of rural low-voltage microgrids. The microgrid integrated interface device has a total of 3 ports, namely the 380V grid-connected port, the DC microgrid port, and the AC microgrid port. Among them, the DC microgrid port corresponds to the photovoltaic storage and charging DC microgrid connected to rural photovoltaic, energy storage, charging piles and other DC power sources and loads; the AC microgrid port corresponds to the agricultural AC microgrid connected to rural small wind turbines, rural family workshops, rural small factories, small hydropower, biogas and other AC and DC micro sources and loads. It can be seen that the microgrid integrated interface device is mainly used in the application of rural microgrid access with various types of distributed energy and different rural electricity loads.

[0027] like Figure 2 and Figure 3 As shown, the modular expandable low-voltage area microgrid integrated interface device of this embodiment includes:

[0028] Public low-voltage and high-frequency AC busbar. The main function of this public low-voltage and high-frequency AC busbar is to realize the interconnection of microgrids with different energy types in the microgrid integrated interface device, ensure that two-way energy scheduling can be carried out between rural microgrids with different energy types, further reduce the dependence of rural microgrids on distribution networks, and improve the autonomous operation capabilities of rural microgrids, so that the entire device can effectively offset the uncertainty brought to the rural power grid by distributed energy in rural microgrids due to differences in randomness, seasonality, etc.

[0029] The AC / DC module, the AC end is connected to the AC distribution line of the substation as the substation grid-connected port, and the DC end is connected to the public low-voltage high-frequency AC bus through the IPOP-H module; the AC / DC module is used to connect the substation distribution network with the microgrid integrated interface device. The AC / DC module in this embodiment can adopt a VSC power conversion circuit, which can realize the energy interaction between the low-voltage substation distribution network and the entire rural microgrid system.

[0030] The DC / AC module has a DC end connected to the common low-voltage high-frequency AC busbar through an IPOP-H module, and an AC end connected to the agricultural AC microgrid as an AC microgrid port; the DC / AC module is used to enable various distributed energy sources in the agricultural AC microgrid to receive unified dispatching from the microgrid integrated interface device. The DC / AC module in this embodiment can adopt a VSC power conversion circuit, which can achieve energy complementarity between the agricultural AC microgrid and rural microgrids of other energy types, and make full use of various energy sources in the rural microgrid.

[0031] The DC / DC module has a first DC end connected to the common low-voltage high-frequency AC busbar through an IPOP-H module, and a second DC end connected to the photovoltaic storage and charging DC microgrid as a DC microgrid port; the DC / DC module is used to enable various DC micro-sources and DC loads in the photovoltaic storage and charging DC microgrid to receive unified dispatching from the microgrid integrated interface device. The DC / DC module in this embodiment can adopt a three-level in-phase Buck-Boost conversion circuit, and its main function is to achieve access to the rural photovoltaic storage and charging DC microgrid, make up for the defects of the rural photovoltaic storage and charging DC microgrid and other rural microgrids in terms of energy type differences, and make full use of various energy sources in the rural microgrid.

[0032] The central controller is connected to the AC / DC module, the DC / AC module and the DC / DC module respectively through signal lines, and is used to control the AC / DC module, the DC / AC module and the DC / DC module to achieve two-way energy scheduling between microgrids.

[0033] The IPOP-H module in this embodiment includes n H full-bridge circuits, which are connected by IPOP, where n is a positive integer greater than 1. Its function realization process can be described as follows: the electricity demand in rural areas is relatively dispersed, and the distributed energy generation forms are diverse and of different scales. The power capacity of rural microgrids with different energy structures is different, and the current output is different. Figure 3 It can be seen that the power formula of the IPOP-H module is: U dc I dc =U1I1+U2I2+…+U n I n In the formula, Udc I dc is the input power of the IPOP-H module, U1I1 is the input power of the first H full-bridge circuit in the IPOP-H module, U2I2 is the input power of the second H full-bridge circuit in the IPOP-H module, and U n I n is the input power of the nth H full-bridge circuit in the IPOP-H module. The size of n is related to the power capacity of the connected microgrid. By adjusting the size of n, the access requirements of rural microgrids with different power capacities can be met.

[0034] In this embodiment, a high-frequency transformer is also provided between the IPOP-H module and the common low-voltage high-frequency AC bus. The main function of the high-frequency transformer is to realize the electrical isolation of the entire low-voltage substation microgrid system, to ensure that when an internal fault occurs in the microgrid integrated interface device, it will not affect the normal operation of other microgrids in the microgrid system, thereby improving the robustness and fault tolerance of the rural microgrid system.

[0035] The present invention is further described below by an embodiment.

[0036] like Figure 4 As shown, the microgrid integrated interface device of this embodiment mainly includes a 380V grid-connected port, a 380V agricultural AC microgrid port, and a ±375V photovoltaic storage and charging DC microgrid port. Among them, the 380V grid-connected port and the 380V agricultural AC microgrid port are composed of a VSC conversion circuit module, the ±375V photovoltaic storage and charging DC microgrid port is composed of a three-level in-phase Buck-Boost conversion circuit module, and the middle part is composed of a plurality of IPOP H-bridge modular combination circuits and an isolated high-frequency transformer energy conversion circuit. It should be noted that each IPOP-H-bridge modular combination circuit is composed of n H-bridge circuits, n is related to the power capacity of the connected rural microgrid, and the access of rural microgrids with different power capacities can be achieved by adjusting the size of n. Three high-frequency transformers are used to achieve electrical isolation of the entire microgrid system between rural microgrids, and a common low-voltage and high-frequency AC bus is used to achieve energy complementarity between rural photovoltaic storage and charging DC microgrids and agricultural AC microgrids, thereby reducing the dependence of rural microgrids on distribution networks, improving the autonomous operation capabilities of rural microgrids, and further reducing the uncertainty of the randomness, seasonality and other differences in rural distributed energy generation on the power grid.

[0037] It is not difficult to find that the present invention realizes the interconnection and two-way dispatch of rural microgrids with different energy forms such as rural DC microgrids and rural AC microgrids through an expandable public low-voltage high-frequency AC bus, thereby improving the autonomous operation capability of the entire rural microgrid system and the overall absorption capacity of the rural microgrid system for various distributed energy sources. The present invention also modularizes multiple H full-bridge circuits and adopts an IPOP connection structure to form an IPOP-H module, which can not only meet the access requirements of rural microgrids with different power capacities, but also the IPOP connection structure simplifies the problem of current sharing control of switch tubes. In addition, the present invention also uses a high-frequency transformer to achieve electrical isolation of the microgrid system, ensuring that rural microgrids with multiple energy types can be safely and stably connected to the microgrid integrated interface device.

Claims

1. A modular and expandable low-voltage area microgrid integrated interface device, characterized in that: include: Public low-voltage high-frequency AC bus; AC / DC module, the AC end is connected to the AC distribution line of the substation as the substation grid-connected port, and the DC end is connected to the public low-voltage and high-frequency AC bus through the IPOP-H module; the AC / DC module is used to connect the substation distribution network with the microgrid integrated interface device; A DC / AC module, wherein the DC end is connected to the common low-voltage high-frequency AC busbar through an IPOP-H module, and the AC end is connected to the agricultural AC microgrid as an AC microgrid port; the DC / AC module is used to enable various distributed energy sources in the agricultural AC microgrid to receive unified dispatching from the microgrid integrated interface device; A DC / DC module, wherein the first DC end is connected to the common low-voltage high-frequency AC bus through an IPOP-H module, and the second DC end is connected to the photovoltaic storage and charging DC microgrid as a DC microgrid port; the DC / DC module is used to enable various DC micro-sources and DC loads in the photovoltaic storage and charging DC microgrid to receive unified dispatching from the microgrid integrated interface device; The central controller is connected to the AC / DC module, the DC / AC module and the DC / DC module respectively through signal lines, and is used to control the AC / DC module, the DC / AC module and the DC / DC module to achieve two-way energy scheduling between microgrids.

2. The modular expandable low-voltage area microgrid integrated interface device according to claim 1 is characterized in that: The IPOP-H module includes n H full-bridge circuits, and the n H full-bridge circuits are connected using IPOP, wherein n is a positive integer greater than 1.

3. The modular expandable low-voltage area microgrid integrated interface device according to claim 2 is characterized in that: The power formula of the IPOP-H module is: dc I dc =U1I1+U2I2+…+U n I n , where U dc I dc is the input power of the IPOP-H module, U1I1 is the input power of the first H full-bridge circuit in the IPOP-H module, U2I2 is the input power of the second H full-bridge circuit in the IPOP-H module, and U n I n is the input power of the nth H full-bridge circuit in the IPOP-H module.

4. The modular expandable low-voltage area microgrid integrated interface device according to claim 1 is characterized in that: The AC / DC module is a VSC power conversion circuit.

5. The modular expandable low-voltage area microgrid integrated interface device according to claim 1 is characterized in that: The DC / AC module is a VSC power conversion circuit.

6. The modular expandable low-voltage area microgrid integrated interface device according to claim 1, characterized in that: The DC / DC module is a three-level in-phase Buck-Boost conversion circuit.

7. The modular expandable low-voltage area microgrid integrated interface device according to claim 1 is characterized in that: A high-frequency transformer is also provided between the IPOP-H module and the common low-voltage high-frequency AC bus.

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