Electric vehicle charging system

Abstract

The invention relates to an electric vehicle charging system. The electric vehicle charging system comprises a power grid side charging circuit, a charging pile energy storage side charging circuit, a direct current bus and an electric vehicle, one end of the direct current bus is connected with the power grid side charging circuit, and the other end of the direct current bus is connected with the charging pile energy storage side charging circuit and the electric vehicle; the electric vehicle is charged through the power grid side charging circuit and / or the charging pile energy storage side charging circuit. When the charging system is used for charging the electric automobile, the charging stability of the electric automobile can be improved.

Description

Technical Field

[0001] This application relates to the technical field of electric vehicle charging, and particularly to an electric vehicle charging system. Background Art

[0002] As an energy replenishment device, the charging system is a key infrastructure for the large-scale popularization and application of new energy vehicles.

[0003] In related technologies, electric vehicles are usually charged unidirectionally by electric vehicle charging piles, or the charging and discharging between the power grid and electric vehicles is achieved through the power grid.

[0004] However, in the electric vehicle charging methods in related technologies, the situation of large loads on the power grid or charging piles is likely to occur, resulting in a sudden increase in the load of the distribution network and causing voltage fluctuations, seriously affecting the charging stability of electric vehicles. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide an electric vehicle charging system that can improve the charging stability of electric vehicles.

[0006] In a first aspect, an embodiment of the present application provides an electric vehicle charging system. The electric vehicle charging system includes a grid-side charging circuit, a charging pile energy storage-side charging circuit, a DC bus, and an electric vehicle. One end of the DC bus is connected to the grid-side charging circuit, and the other end of the DC bus is respectively connected to the charging pile energy storage-side charging circuit and the electric vehicle;

[0007] The electric vehicle is charged through the grid-side charging circuit and / or the charging pile energy storage-side charging circuit.

[0008] In one embodiment, the grid-side charging circuit includes a power grid, a filtering module, and a bidirectional AC-DC conversion module;

[0009] One end of the filtering module is connected to the power grid, the other end of the filtering module is connected to one end of the bidirectional AC-DC conversion module, and the other end of the bidirectional AC-DC conversion module is connected to the DC bus.

[0010] In one embodiment, the filtering module includes a three-phase inductance-capacitance filter;

[0011] The three-phase inductance-capacitance filter filters out harmonics and noise in the power grid through the frequency selectivity of capacitors and inductors.

[0012] In one embodiment, the bidirectional AC-DC conversion module includes a three-level neutral-point clamped converter; each phase of the three-level neutral-point clamped converter is provided with four insulated gate bipolar transistors and two clamping diodes;

[0013] The three-level neutral-point clamped converter is used to convert the industrial-frequency alternating current into direct current to provide a stable voltage for the DC bus when the power grid is used as a power source to supply power to the outside; and, when the power grid is used as a load to receive electrical energy, it converts the direct current into industrial-frequency alternating current to charge the power grid.

[0014] In one embodiment, the charging circuit on the energy storage side of the charging pile includes a bidirectional voltage regulation module and a charging pile energy storage battery;

[0015] One end of the bidirectional voltage regulation module is connected to the DC bus, and the other end of the bidirectional voltage regulation module is connected to the charging pile energy storage battery.

[0016] In one embodiment, the bidirectional voltage regulation module includes a bidirectional buck / boost converter;

[0017] The bidirectional buck / boost converter is used to step down / step up the electrical energy of the charging pile energy storage battery and transmit it to the DC bus when the charging pile energy storage battery is used as a power source to supply power to the outside; and, when the charging pile energy storage battery is used as a load to receive electrical energy, it steps down / step up the electrical energy on the DC bus and transmits it to the charging pile energy storage battery.

[0018] In one embodiment, the electric vehicle charging system further includes a bidirectional DC conversion module;

[0019] One end of the bidirectional DC conversion module is connected to the DC bus, and the other end of the bidirectional DC conversion module is connected to the electric vehicle.

[0020] In one embodiment, the bidirectional DC conversion module includes a plurality of parallel-connected dual-active-bridge converters; each of the dual-active-bridge converters includes a plurality of primary power tubes, a plurality of secondary power tubes, and a high-frequency transformer;

[0021] The dual-active-bridge converter is used to convert the electrical energy of the electric vehicle to the DC bus to charge the power grid when the electric vehicle is used as a power source to supply power to the outside; and, when the electric vehicle is used as a load to receive electrical energy, it converts the bus voltage of the DC bus into the voltage required by the electric vehicle to charge the electric vehicle.

[0022] In one embodiment, two parallel capacitors are provided on the DC bus, which are used to jointly suppress the dynamic fluctuations and ripple noise of the bus voltage on the DC bus through the energy storage characteristics and filtering characteristics of the capacitors.

[0023] In one embodiment, the electric vehicle charging system includes multiple working modes;

[0024] Multiple working modes include the grid charging the electric vehicle, the electric vehicle charging the grid, the grid charging the energy storage battery of the charging pile, the energy storage battery of the charging pile charging the grid, the energy storage battery of the charging pile charging the electric vehicle, the grid simultaneously charging the electric vehicle and the energy storage battery of the charging pile, and the electric vehicle and the energy storage battery of the charging pile simultaneously charging the grid.

[0025] The electric vehicle charging system provided by the embodiment of the present application includes a grid-side charging circuit, a charging pile energy storage-side charging circuit, a DC bus, and an electric vehicle. One end of the DC bus is connected to the grid-side charging circuit, and the other end of the DC bus is respectively connected to the charging pile energy storage-side charging circuit and the electric vehicle; the electric vehicle is charged through the grid-side charging circuit and / or the charging pile energy storage-side charging circuit. In this electric vehicle charging system, one end of the DC bus is connected to the grid-side charging circuit, and the other end is connected to the charging pile energy storage-side charging circuit and the electric vehicle, so as to expand the interaction mode between the grid and the electric vehicle to the interaction modes of the grid and the electric vehicle, the grid and the charging pile energy storage, and the charging pile energy storage and the electric vehicle, enabling the grid and the charging pile energy storage to jointly charge the electric vehicle. In this way, the electric vehicle can be charged either by the grid-side charging circuit or the charging pile energy storage-side charging circuit alone, or by the grid-side charging circuit and the charging pile energy storage-side charging circuit simultaneously. Whether the load on the grid side is large or the load on the charging pile energy storage side is large, the electric vehicle can be continuously powered by the charging circuit on the other side, or by the charging circuits on both sides simultaneously, reducing the charging pressure on each charging circuit and improving the charging stability of each side, thereby improving the charging stability of the electric vehicle. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is a schematic structural diagram of an electric vehicle charging system in an embodiment;

[0028] Figure 2 It is a schematic structural diagram of an electric vehicle charging system in another embodiment;

[0029] Figure 3 It is a schematic structural diagram of an electric vehicle charging system in another embodiment;

[0030] Figure 4 It is a schematic structural diagram of an electric vehicle charging system in another embodiment;

[0031] Figure 5aSchematic diagram of power flow in the G2V mode in an embodiment;

[0032] Figure 5b Schematic diagram of power flow in the V2G mode in an embodiment;

[0033] Figure 5c Schematic diagram of power flow in the G2B mode in an embodiment;

[0034] Figure 5d Schematic diagram of power flow in the B2G mode in an embodiment;

[0035] Figure 5e Schematic diagram of power flow in the B2V mode in an embodiment;

[0036] Figure 5f Schematic diagram of power flow in an embodiment where the power grid charges both the electric vehicle and the energy storage battery of the charging pile simultaneously;

[0037] Figure 5g Schematic diagram of power flow in an embodiment where the electric vehicle and the energy storage battery of the charging pile supply power to the power grid simultaneously;

[0038] Figure 6 Schematic diagram of the structure of an integrated converter topology in an embodiment. Detailed implementation manners

[0039] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and any variations thereof in the specification and claims of this application and the above accompanying drawings are intended to cover non-exclusive inclusion. In the description of the embodiments of this application, the technical terms "first", "second", "third", "fourth", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means more than two unless otherwise specifically defined.

[0041] Reference to "embodiments" in this specification means that the particular features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0042] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "connection" should be understood in a broad sense. For example, it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal connection of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0043] The technical background of the embodiments of the present application will be described below.

[0044] As an energy supply device, the charging system is a key infrastructure for the large-scale popularization and application of new energy vehicles, and is the key to solving the energy and environmental crisis and achieving the goals of "carbon peak" and "carbon neutrality". In this context, the interactive and integrated development of the new distribution network "electric vehicle - charging pile - power grid" is an important way to improve the flexibility and stability of the power grid and promote the clean and low-carbon transformation of energy. The electric vehicle charging system is constantly innovating and there are various types. However, existing technologies often focus on how "electric vehicles" interact with the power grid economically and efficiently through "public / utility / special charging piles", and basically do not consider the additional potential of charging piles in the idle state. Relevant data shows that the actual utilization rate of existing charging piles does not exceed 30%, and some charging piles are even in a long-term idle state. If distributed energy storage can be effectively integrated with charging piles and share a set of inverters for grid connection, it can not only reduce the grid connection cost of distributed energy storage, but also improve the power regulation ability of charging piles in the idle state, and even further enrich the flexibility and adjustable margin of V2G technology.

[0045] Traditional electric vehicle charging piles can often only charge electric vehicles unidirectionally, or realize the charging and discharging between the power grid and electric vehicles. The electric vehicle charging station mode relying on the traditional power grid for power supply has too much impact on the distribution network; and in special application scenarios such as limited distribution capacity, traditional charging pile technologies cannot meet the charging and emergency power supply needs of users.

[0046] Based on this, the embodiments of the present application provide an electric vehicle charging system. A grid-side charging circuit is connected to one end of the DC bus, and a charging pile energy storage side charging circuit and an electric vehicle are connected to the other end, so as to expand the interaction mode between the grid and the electric vehicle to the interaction modes of the grid and the electric vehicle, the grid and the charging pile energy storage, and the charging pile energy storage and the electric vehicle, enabling the grid and the charging pile energy storage to jointly charge the electric vehicle. In this way, the electric vehicle can be charged either by the grid-side charging circuit or the charging pile energy storage side charging circuit alone, or by the grid-side charging circuit and the charging pile energy storage side charging circuit simultaneously. Whether the load on the grid side is large or the load on the charging pile energy storage side is large, the electric vehicle can be continuously powered by the charging circuit on the other side, or powered by both charging circuits simultaneously, reducing the charging pressure on each charging circuit and improving the charging stability of each side, thereby improving the charging stability of the electric vehicle. Of course, the technical solutions provided in the embodiments of the present application are not limited to only solving the above problems, and there are other technical effects. For specific details, please refer to the following embodiments for description.

[0047] The following will illustrate the detailed implementation process of the electric vehicle charging system provided by the present application through specific embodiments.

[0048] In an exemplary embodiment, as Figure 1 shown, an electric vehicle charging system is provided. The electric vehicle charging system includes a grid-side charging circuit 10, a charging pile energy storage side charging circuit 20, a DC bus 30, and an electric vehicle 40. One end of the DC bus 30 is connected to the grid-side charging circuit 10, and the other end of the DC bus 30 is respectively connected to the charging pile energy storage side charging circuit 20 and the electric vehicle 40;

[0049] The electric vehicle 40 is charged through the grid-side charging circuit 10 and / or the charging pile energy storage side charging circuit.

[0050] In the embodiments of the present application, the grid-side charging circuit 10 is a circuit for directly charging the electric vehicle 40 by the grid, which can convert the alternating current of the grid into high-voltage direct current, inject it into the DC bus 30 through links such as rectification, filtering, and power factor correction, and provide electrical energy for the electric vehicle 40 through the DC bus 30.

[0051] The charging pile energy storage side charging circuit 20 is a circuit for charging the electric vehicle 40 by the charging pile energy storage device, which can draw power from the DC bus 30, adjust the voltage / current through a DC-DC converter, and provide electrical energy for the electric vehicle 40.

[0052] The DC bus 30 is a key DC conduction path connecting the power grid and the electric vehicle. During charging, the DC bus 30 efficiently and stably transmits the direct current rectified by the charging pile from the power grid to the battery of the electric vehicle 40. During discharging, the DC bus 30 reversely transmits the direct current in the battery of the electric vehicle 40 back to the power grid.

[0053] In the embodiment of the present application, one end of the DC bus 30 is connected to the grid-side charging circuit 10, and the other end is connected to the charging pile energy storage side charging circuit 20 and the electric vehicle 40. Among them, the electric energy of the grid-side charging circuit 10 is transmitted to the electric vehicle 40 through the DC bus 30 to charge the electric vehicle 40. The electric energy of the charging pile energy storage side charging circuit 20 can also be transmitted to the electric vehicle 40 to charge the electric vehicle 40.

[0054] In one embodiment, when the load of the grid-side charging circuit 10 is large, the grid-side charging circuit 10 can be cut off, and the electric vehicle 40 can continue to be charged through the charging pile energy storage side charging circuit 20, so as to reduce the charging pressure of the power grid, improve the stability of the power grid, and thus improve the charging stability of the electric vehicle 40. When the load of the charging pile energy storage side charging circuit 20 is large, the charging pile energy storage side charging circuit 20 can be cut off, and the electric vehicle 40 can continue to be charged through the grid-side charging circuit 10, so as to reduce the charging pressure of the charging pile energy storage and improve the charging stability of the electric vehicle 40.

[0055] In another embodiment, when the load of the grid-side charging circuit 10 or the charging pile energy storage charging circuit 20 is large, the grid-side charging circuit 10 and the charging pile energy storage charging circuit 20 can be used simultaneously to charge the electric vehicle 40, so as to reduce the charging pressure of the power grid and the charging pile energy storage and improve the charging stability of the electric vehicle 40.

[0056] Based on this, in actual use, the electric vehicle 40 can be charged separately by the grid-side charging circuit 10 or the charging pile energy storage side charging circuit 20, or the electric vehicle 40 can be charged simultaneously by the grid-side charging circuit 10 and the charging pile energy storage side charging circuit 20. When the load of one of the charging circuits is large, it can be switched to the other charging circuit to supply power to the electric vehicle 40, or the two charging circuits can charge the electric vehicle 40 simultaneously, so as to reduce the pressure on each charging circuit and improve the charging stability of the electric vehicle 40.

[0057] The electric vehicle charging system provided by the embodiments of the present application includes a grid-side charging circuit, a charging pile energy storage-side charging circuit, a DC bus, and an electric vehicle. One end of the DC bus is connected to the grid-side charging circuit, and the other end of the DC bus is respectively connected to the charging pile energy storage-side charging circuit and the electric vehicle; the electric vehicle is charged through the grid-side charging circuit and / or the charging pile energy storage-side charging circuit. In this electric vehicle charging system, one end of the DC bus is connected to the grid-side charging circuit, and the other end is connected to the charging pile energy storage-side charging circuit and the electric vehicle, so as to expand the interaction mode between the grid and the electric vehicle to the interaction modes of the grid and the electric vehicle, the grid and the charging pile energy storage, and the charging pile energy storage and the electric vehicle, enabling the grid and the charging pile energy storage to jointly charge the electric vehicle. In this way, the electric vehicle can be charged either separately by the grid-side charging circuit or the charging pile energy storage-side charging circuit, or simultaneously by the grid-side charging circuit and the charging pile energy storage-side charging circuit. Whether the load on the grid side is large or the load on the charging pile energy storage side is large, the electric vehicle can be continuously powered by the charging circuit on the other side, or simultaneously powered by the charging circuits on both sides, reducing the charging pressure on each charging circuit and improving the charging stability of each side, thereby improving the charging stability of the electric vehicle.

[0058] Based on the above embodiments, an embodiment is provided to illustrate the structure of the above grid-side charging circuit and the functions of each structure.

[0059] In an exemplary embodiment, as Figure 2 shown, the grid-side charging circuit 10 includes a grid 11, a filtering module 12, and a bidirectional AC-DC conversion module 13;

[0060] One end of the filtering module 12 is connected to the grid 11, the other end of the filtering module 12 is connected to one end of the bidirectional AC-DC conversion module 13, and the other end of the bidirectional AC-DC conversion module 13 is connected to the DC bus 30.

[0061] Among them, the filtering module 12 can suppress grid harmonics and noise and improve the power quality. In one embodiment, the filtering module 12 includes a three-phase inductance-capacitance filter, and the three-phase inductance-capacitance filter filters out harmonics and noise in the grid through the frequency selectivity of capacitors and inductors.

[0062] Inductors and capacitors present different impedances to different frequencies. Utilize this characteristic to design the amplitude-frequency response of the filter, such as low-pass and band-stop characteristics, so that the fundamental frequency signal can pass through smoothly, and specific-frequency harmonics / noise are attenuated or bypassed. For harmonics, the inductance-capacitance characteristics can be used to specifically filter them; for noise, the high-frequency bypass of the capacitor and the high-frequency suppression of the inductor can be relied on.

[0063] In the embodiments of the present application, the three-phase inductance-capacitance filter presents different impedance characteristics to high-order harmonics and high-frequency noise in the power grid through the frequency selectivity of the high-frequency high impedance of the inductor and the high-frequency low impedance of the capacitor, allowing the fundamental frequency signal to pass through smoothly while providing a low-impedance path for the harmonics or blocking the harmonic transmission, thereby filtering out the harmonics and noise and improving the power quality of the power grid.

[0064] The bidirectional AC-DC conversion module 13 can achieve bidirectional energy flow between AC and DC, and its working modes include a rectification mode and an inversion mode. Among them, the rectification mode converts the AC power of the power grid into DC power, and the inversion mode converts the DC power into AC power.

[0065] In one embodiment, the bidirectional AC-DC conversion module 13 includes a three-level neutral point clamped converter; each phase of the three-level neutral point clamped converter is provided with four insulated gate bipolar transistors and two clamping diodes; the three-level neutral point clamped converter is used to convert the industrial frequency AC power into DC power to provide a stable voltage for the DC bus when the power grid supplies power as a power source; and, when the power grid accepts electric energy as a load, convert the DC power into industrial frequency AC power to charge the power grid.

[0066] Each phase of the three-level neutral point clamped (NPC) converter is provided with four insulated gate bipolar transistors (IGBTs), and at the same time, each phase is also provided with two clamping diodes. Such a standardized structure of 4 transistors + diodes achieves a balance among voltage stress, output performance, reliability, and cost, avoids voltage imbalance, and improves the stability of the charging system.

[0067] When the power grid is charging and being charged, the three-level neutral point clamped converter has different functions. If the power grid supplies power as a power source, for example, the power grid charges an electric vehicle, the power grid charges the energy storage battery of a charging pile, or the power grid charges both the electric vehicle and the energy storage battery of the charging pile at the same time. At this time, the three-level neutral point clamped converter can convert the industrial frequency AC power of the power grid into DC power to provide a stable voltage for the DC bus, thereby charging the electric vehicle and / or the energy storage battery of the charging pile. If the power grid accepts electric energy as a load, for example, the electric vehicle charges the power grid, the energy storage battery of the charging pile supplies power to the power grid, or the electric vehicle and the energy storage battery of the charging pile supply power to the power grid at the same time. At this time, the three-level neutral point clamped converter converts the DC power of the DC bus into industrial frequency AC power to supply power to the power grid.

[0068] The electric vehicle charging system provided by the embodiment of the present application, the grid-side charging circuit includes a grid, a filtering module and a bidirectional AC-DC conversion module; one end of the filtering module is connected to the grid, the other end of the filtering module is connected to one end of the bidirectional AC-DC conversion module, and the other end of the bidirectional AC-DC conversion module is connected to the DC bus. In this electric vehicle charging system, a grid, a filtering module and a bidirectional AC-DC conversion module are provided in the grid-side charging circuit to filter out harmonics and noise from the electric energy of the grid through the filtering module, thereby improving the power quality of the grid, and, through the bidirectional AC-DC conversion module, converting alternating current into direct current, or converting direct current into alternating current, so as to realize power supply from the grid to the outside or the grid receiving electric energy.

[0069] Based on the above embodiment, an embodiment is provided to illustrate the structure of the charging pile energy storage side charging circuit and the functions of each structure.

[0070] In an exemplary embodiment, as Figure 3 shown, the charging pile energy storage side charging circuit 20 includes a bidirectional voltage regulation module 21 and a charging pile energy storage battery 22;

[0071] One end of the bidirectional voltage regulation module 21 is connected to the DC bus 30, and the other end of the bidirectional voltage regulation module 21 is connected to the charging pile energy storage battery 22.

[0072] The charging pile energy storage battery 22 is a device that converts electric energy into chemical energy and stores it, and then releases the stored energy as electric energy when needed. In the charging system of the embodiment of the present application, electric energy is stored through the energy storage battery and charging services are provided for electric vehicles when needed. Combining energy storage technology and charging technology, the storage, regulation and release of electric energy are realized, and the flexibility and reliability of charging facilities are improved.

[0073] The bidirectional voltage regulation module 21 can adjust the voltage bidirectionally, that is, boost or buck. In one embodiment, the bidirectional voltage regulation module 21 includes a bidirectional buck / boost converter; the bidirectional buck / boost converter is used to step down / step up the electric energy of the charging pile energy storage battery and transmit it to the DC bus when the charging pile energy storage battery is used as a power source to supply power to the outside; and, when the charging pile energy storage battery is used as a load to receive electric energy, step down / step up the electric energy on the DC bus and transmit it to the charging pile energy storage battery.

[0074] When the charging pile energy storage battery is charging and being charged, the bidirectional buck / boost converter has different functions. If the charging pile energy storage battery serves as a power source to supply power outward, for example, the charging pile energy storage battery supplies power to the power grid, the charging pile energy storage battery charges an electric vehicle, or the electric vehicle and the charging pile energy storage battery supply power to the power grid simultaneously. At this time, the bidirectional buck / boost converter steps down / up the electrical energy of the charging pile energy storage battery and transmits the regulated electrical energy to the DC bus to supply power to the electric vehicle and / or the power grid. If the charging pile energy storage battery serves as a load to receive electrical energy, for example, the power grid charges the charging pile energy storage battery, or the power grid charges the electric vehicle and the charging pile energy storage battery simultaneously. At this time, the bidirectional buck / boost converter steps down / up the electrical energy on the DC bus and transmits the regulated electrical energy to the charging pile energy storage battery to charge the charging pile energy storage battery.

[0075] In the electric vehicle charging system provided by the embodiment of the present application, the charging circuit on the energy storage side of the charging pile includes a bidirectional voltage regulation module and a charging pile energy storage battery; one end of the bidirectional voltage regulation module is connected to the DC bus, and the other end of the bidirectional voltage regulation module is connected to the charging pile energy storage battery. In this electric vehicle charging system, the charging circuit on the energy storage side of the charging pile is provided with a bidirectional voltage regulation module and a charging pile energy storage battery. The bidirectional voltage regulation module steps up and down the electrical energy to adjust the voltage to a matching value, thereby realizing the charging and being charged of the charging pile energy storage battery, and storing electrical energy through the charging pile energy storage battery to provide charging services for electric vehicles, improving the reliability and stability of the charging system.

[0076] Based on the above embodiment, an embodiment of the module for voltage level conversion in the above charging system is described.

[0077] In an exemplary embodiment, as Figure 4 shown, the electric vehicle charging system further includes a bidirectional DC conversion module 50; one end of the bidirectional DC conversion module 50 is connected to the DC bus 30, and the other end of the bidirectional DC conversion module 50 is connected to the electric vehicle 40.

[0078] Among them, the bidirectional DC conversion module 50 is used to realize the bidirectional flow of DC electrical energy, that is, while keeping the polarities of the input and output voltages unchanged, the direction of the current is changed according to needs to realize the bidirectional transmission of electrical energy.

[0079] In one embodiment, the bidirectional DC conversion module 50 includes a plurality of parallel-connected dual active bridge converters (DAB); each dual active bridge converter includes a plurality of primary power tubes, a plurality of secondary power tubes, and a high-frequency transformer;

[0080] The dual-active-bridge converter is used to convert the electrical energy of an electric vehicle to the DC bus to charge the power grid when the electric vehicle serves as a power source to supply power outward; and, when the electric vehicle serves as a load to receive electrical energy, convert the bus voltage of the DC bus to the voltage required by the electric vehicle to charge the electric vehicle.

[0081] The dual-active-bridge converter is a high-performance bidirectional DC-DC conversion device, and its core function is to achieve efficient bidirectional energy flow between the DC bus and the electric vehicle battery. Among them, the dual-active-bridge converter includes 4 primary-side power transistors, 4 secondary-side power transistors, and a high-frequency transformer. The primary side and the secondary side each consist of 4 power transistors to form an H-bridge structure. Each bridge arm contains two upper and lower switching transistors. By controlling the on and off of the switching transistors, bidirectional energy transfer between the primary and secondary sides is achieved. The high-frequency transformer is used for electrical isolation to isolate the primary and secondary side circuits and achieve power regulation.

[0082] If the electric vehicle serves as a power source to supply power outward, for example, the electric vehicle charges the power grid, or the electric vehicle and the energy storage battery of the charging pile supply power to the power grid simultaneously. At this time, the dual-active-bridge converter converts the electrical energy of the electric vehicle from the voltage of the electric vehicle to the voltage required by the power grid and transmits it to the DC bus, thereby charging the power grid. If the electric vehicle serves as a load to receive electrical energy, for example, the power grid charges the electric vehicle, the energy storage battery of the charging pile charges the electric vehicle, or the power grid charges the electric vehicle and the energy storage battery of the charging pile simultaneously. At this time, the dual-active-bridge converter converts the voltage of the DC bus to the voltage level required by the electric vehicle and transmits the converted electrical energy to the electric vehicle to charge the electric vehicle.

[0083] In one embodiment, two parallel capacitors are arranged on the DC bus 30 to jointly suppress the dynamic fluctuations and ripple noise of the bus voltage on the DC bus through the energy storage characteristics and filtering characteristics of the capacitors.

[0084] Two capacitors are connected in parallel on the DC bus. Through the energy storage characteristics of the capacitors (buffering energy fluctuations and maintaining voltage stability) and filtering characteristics (bypassing ripple current and suppressing high-frequency / low-frequency voltage ripple), the dynamic fluctuations and ripple noise of the bus voltage are jointly suppressed, and the voltage quality of the DC bus is improved.

[0085] When the load suddenly changes, resulting in a sudden increase or decrease in the bus current, the parallel capacitors can quickly release or absorb energy, avoiding a large voltage drop or spike. Utilizing the characteristic that the voltage of the capacitor cannot change suddenly, the dynamic fluctuations of the bus voltage are flattened. Among them, parallel connection can increase the equivalent capacitance and strengthen the energy storage and filtering capabilities.

[0086] The electric vehicle charging system provided by the embodiment of the present application further includes a bidirectional DC conversion module; one end of the bidirectional DC conversion module is connected to the DC bus, and the other end of the bidirectional DC conversion module is connected to the electric vehicle. In this electric vehicle charging system, a bidirectional DC conversion module is further provided to convert the voltage of the electric energy in the DC bus or the electric vehicle into different levels through the bidirectional DC conversion module, so as to transmit the converted electric energy to charge the electric vehicle or the power grid, improving the flexibility of the electric vehicle charging system.

[0087] Based on the above embodiment, an embodiment of various working modes of the above electric vehicle charging system is provided for description.

[0088] In an exemplary embodiment, the electric vehicle charging system includes multiple working modes;

[0089] The multiple working modes include the power grid charging the electric vehicle, the electric vehicle charging the power grid, the power grid charging the energy storage battery of the charging pile, the energy storage battery of the charging pile charging the power grid, the energy storage battery of the charging pile charging the electric vehicle, the power grid simultaneously charging the electric vehicle and the energy storage battery of the charging pile, and the electric vehicle and the energy storage battery of the charging pile simultaneously charging the power grid.

[0090] In the embodiment of the present application, the electric vehicle charging system includes seven working modes and can realize flexible switching of multi-mode functions.

[0091] The first mode is the power grid charging the electric vehicle (Grid-to-Vehicle, G2V), and its power flow is as Figure 5a shown. In the G2V mode, the high-power three-level NPC converter works in the rectification mode to convert the industrial-frequency alternating current into direct current and provide a stable voltage for the DC bus. The electric energy on the DC bus is transmitted to the power battery of the electric vehicle through the DAB converter via the high-frequency isolation transformer to achieve charging. Among them, by controlling the DAB module and the high-power NPC to work in the forward mode and the rectification mode respectively, the power flows from the grid side to the electric vehicle battery, and it is ensured that the system always works in the state of unity power factor. In this mode, by using the peak-valley electricity price difference, the electric vehicle can charge during the low-load period of the power grid (when the electricity price is low), thereby reducing the charging cost and increasing the power utilization rate.

[0092] The second mode is the electric vehicle charging the power grid (Vehicle-to-Grid, V2G), and its power flow is as Figure 5bAs shown in the figure. In the V2G mode, the electric energy stored in the electric vehicle battery is efficiently converted to the DC bus through a DAB converter, and then converted to industrial frequency alternating current through a high-power NPC three-level inverter. Through grid connection control, bidirectional energy interaction with low loss and high power quality is achieved with the power grid, completing the dynamic power support from the vehicle-side energy storage to the grid-side. Among them, by controlling the DAB module and the high-power NPC to work in the reverse mode and the inverter mode respectively, the power is realized to flow from the electric vehicle battery to the power grid, and the system is ensured to always work under the state of unity power factor. In this mode, by centrally managing the distributed EV batteries, discharging during peak electricity price periods and charging during valley periods, the peak-valley difference of the power grid is significantly reduced, thus increasing the flexibility and stability of the power grid.

[0093] The third mode is that the power grid charges the energy storage battery of the charging pile (Grid-to-Battery, G2B), and its power flow is as Figure 5c shown in the figure. In the G2B mode, the high-power three-level NPC converter works in the rectification mode to convert industrial frequency alternating current into direct current and provide a stable voltage for the DC bus. The electric energy on the DC bus is transmitted to the energy storage battery of the charging pile through a bidirectional buck-boost converter to achieve charging. Among them, by controlling the bidirectional buck-boost converter and the high-power NPC to work in the forward mode and the rectification mode respectively, the power is realized to flow from the grid side to the energy storage battery of the charging pile, and the system is ensured to always work under the state of unity power factor. In this mode, by using the peak-valley electricity price difference, the energy storage battery of the charging pile can be charged during the low-load period of the power grid (when the electricity price is low), thus reducing the charging cost and reducing the dependence on traditional fossil energy.

[0094] The fourth mode is that the energy storage battery of the charging pile supplies power to the power grid (Battery-to-Grid, B2G), and its power flow is as Figure 5d shown in the figure. In the B2G mode, the energy storage battery of the charging pile boosts the electric energy through a bidirectional buck-boost converter and transmits it to the DC bus, and then converts it to industrial frequency alternating current through a high-power NPC three-level inverter. Through grid connection control, efficient energy interaction with the power grid is achieved, completing the low-loss and high-power-quality transmission of electric energy from the energy storage end to the grid end. Among them, by controlling the bidirectional buck-boost converter and the high-power NPC to work in the reverse mode and the inverter mode respectively, the power is made to flow from the energy storage battery of the charging pile to the power grid, and the system is ensured to always work under the state of unity power factor. When the power grid fails or in case of an emergency, the internal energy storage device of the charging pile can be used as an emergency power source, and the stored electric energy in the energy storage device is released back to the power grid, reducing the power grid load pressure, reducing the peak-valley difference, smoothing the fluctuations of renewable energy, improving the utilization rate of renewable energy, providing necessary power support for the power grid, and enhancing the stability of the power grid.

[0095] The fifth mode is that the energy storage battery of the charging pile charges the electric vehicle (Battery-to-Vehicle, B2V), and its power flow is as Figure 5e shown. In the B2V mode, after the electric energy inside the energy storage battery of the charging pile is stepped up / down to the bus voltage through a bidirectional buck-boost converter, it is stably transmitted through the DC bus, and then efficiently converted into the voltage required for charging the electric vehicle through a DAB dual-active bridge converter, completing the safe and controllable power transmission. Controlling the DAB module and the bidirectional buck-boost converter to work in the forward working mode and the reverse working mode respectively ensures that the power flows from the energy storage battery of the charging pile to the electric vehicle. This mode can reduce the dependence of electric vehicle charging on the power grid. The internal energy storage battery of the charging pile can continue to charge the electric vehicle during a power grid fault, providing an independent power supply. During the peak period of the power grid load, the power supply of the energy storage battery can reduce the direct demand of the charging pile for the power grid, avoid power grid overload, optimize energy utilization, improve charging efficiency and user experience, and also promote the utilization of renewable energy, bringing significant economic and environmental benefits.

[0096] The sixth mode is that the power grid charges both the electric vehicle and the energy storage battery of the charging pile at the same time, and its power flow is as Figure 5f shown. In this mode, the high-power three-level NPC converter works in the rectification mode to convert the industrial-frequency alternating current into direct current and provide a stable voltage for the DC bus. The electric energy on the DC bus is transmitted to the power battery of the electric vehicle through the DAB converter via the high-frequency isolation transformer, and at the same time, it is transmitted to the energy storage battery of the charging pile via the bidirectional buck-boost converter, realizing the efficient coordinated charging of both. Among them, by controlling the DAB module and the bidirectional buck-boost converter to work in the forward mode and controlling the high-power NPC to work in the rectification mode, the power flows from the power grid side to the electric vehicle battery and the energy storage battery of the charging pile, and it is ensured that the system always works in the state of unity power factor. In this mode, the economy is further improved, and the peak-valley arbitrage is maximized. When the power grid load is at a low valley, the power grid charges the electric vehicle and the charging pile energy storage at the same time, combining the advantages of G2V and G2B, achieving the effect of 1+1>2, doubling the valley filling ability, and greatly enhancing the consumption of renewable energy.

[0097] The seventh mode is that the electric vehicle and the energy storage battery of the charging pile supply power to the power grid at the same time, and its power flow is as Figure 5gAs shown below. In this mode, the electric vehicle battery and the charging pile energy storage battery respectively convert electrical energy into DC bus through a DAB converter and a bidirectional buck-boost converter, and then cooperate to convert it into industrial frequency alternating current through a high-power NPC three-level inverter, and realize low-loss and high-quality electrical energy two-way energy interaction with the power grid through unified grid connection control, completing the dynamic power aggregation support of vehicle-side energy storage and charging pile energy storage. Among them, by controlling the DAB module and the bidirectional buck-boost converter to work in the reverse mode, and controlling the high-power NPC to work in the inverter mode, the power flows from the electric vehicle side and the charging pile energy storage battery side to the power grid side, and ensures that the system always works in the state of unity power factor. In this mode, the grid stability is increased and the power supply reliability is improved. When the grid load is at its peak, the electric vehicle and the charging pile energy storage supply power to the grid at the same time, combining the advantages of V2G and B2G, better alleviating the grid load pressure and achieving the effect of 1+1>2.

[0098] The electric vehicle charging system provided by the embodiment of the present application, after introducing the charging pile energy storage, has seven different working modes of G2V, G2B, V2G, B2G, B2V, G2B and G2V, V2G and B2G, thus realizing the interaction mode among the internal energy storage of the electric vehicle charging pile, the power grid and the electric vehicle, and forming a three-level energy transmission link of "power grid - charging pile energy storage - vehicle battery".

[0099] In addition, in an exemplary embodiment, the integrated converter topology structure of the charging system in the embodiment of the present application is described.

[0100] As Figure 6 shown, the topology mainly consists of a three-phase LC filter module, a high-power three-level NPC converter, N DAB converter modules, and a bidirectional buck-boost converter. The three-phase LC filter module is connected in series with the high-power NPC converter, passes through the DC bus capacitors C1 and C2, and N DAB modules and an isolated DC / DC converter are connected in parallel to the DC bus. The three-phase LC filter module consists of capacitors C1a, C1b, C1c, and inductors La, Lb, Lc. Each phase of the high-power NPC has 4 IGBT tubes, namely Sx1, Sx2, Sx3, Sx4 (x = a, b, c), and at the same time each phase has two clamping diodes Dx1, Dx2 (x = a, b). C1 and C2 are two voltage stabilizing capacitors on the DC bus. The DAB module includes 4 primary power tubes S1, S2, S3, S4, 4 secondary power tubes S5, S6, S7, S8, the sum of the equivalent inductance and leakage inductance of the transformer L1, and a high-frequency transformer.

[0101] In this embodiment, the interaction mode between the power grid and electric vehicles is expanded to the interaction modes among the power grid and electric vehicles, the power grid and charging pile energy storage, and charging pile energy storage and electric vehicles, avoiding the limitation of charging piles to the power grid capacity, meeting the growing demand for electric vehicle charging, and greatly promoting the popularization of new energy vehicles; it can effectively reduce the impact on the power grid caused by random charging, enrich the flexibility and adjustable margin of V2G technology; it can also improve the power regulation ability of charging piles in the idle state, reduce the grid connection cost of distributed energy storage, and effectively improve the system operation efficiency and equipment utilization rate, thereby constructing a new type of "vehicle-pile-grid" collaborative support technology for the distribution network, strongly supporting the green, flexible, and intelligent development of the new type of distribution network.

[0102] The above content is a further detailed description of the embodiments of the present application in combination with specific / preferred implementation manners. It cannot be determined that the specific implementation of the embodiments of the present application is only limited to these descriptions. For those of ordinary skill in the technical field to which the embodiments of the present application belong, without departing from the concept of the embodiments of the present application, they can still make several substitutions or modifications to these described implementation manners, and these substitution or modification manners should all be regarded as belonging to the protection scope of the embodiments of the present application. In the description of this specification, the description with reference to terms such as "an embodiment", "some embodiments", "preferred embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The above-described embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An electric vehicle charging system, characterized in that The electric vehicle charging system includes a grid-side charging circuit, a charging pile energy storage side charging circuit, a DC bus, and an electric vehicle. One end of the DC bus is connected to the grid-side charging circuit, and the other end of the DC bus is respectively connected to the charging pile energy storage side charging circuit and the electric vehicle; The electric vehicle is charged through the grid-side charging circuit and / or the charging pile energy storage side charging circuit.

2. The electric vehicle charging system according to claim 1, wherein The grid-side charging circuit includes a grid, a filtering module, and a bidirectional AC-DC conversion module; One end of the filtering module is connected to the grid, the other end of the filtering module is connected to one end of the bidirectional AC-DC conversion module, and the other end of the bidirectional AC-DC conversion module is connected to the DC bus.

3. The electric vehicle charging system according to claim 2, characterized in that, The filtering module includes a three-phase inductance-capacitance filter; The three-phase inductance-capacitance filter filters out harmonics and noise in the grid through the frequency selectivity of capacitors and inductors.

4. The electric vehicle charging system according to claim 2, characterized in that, The bidirectional AC-DC conversion module includes a three-level neutral point clamped converter; each phase of the three-level neutral point clamped converter is provided with four insulated gate bipolar transistors and two clamping diodes; The three-level neutral point clamped converter is used to convert industrial frequency alternating current into direct current to provide a stable voltage for the DC bus when the grid is used as a power source to supply power outward; and, when the grid is used as a load to receive electric energy, convert the direct current into the industrial frequency alternating current to charge the grid.

5. The electric vehicle charging system according to any one of claims 1-4, characterized in that, The charging pile energy storage side charging circuit includes a bidirectional voltage regulation module and a charging pile energy storage battery; One end of the bidirectional voltage regulation module is connected to the DC bus, and the other end of the bidirectional voltage regulation module is connected to the charging pile energy storage battery.

6. The electric vehicle charging system according to claim 5, wherein The bidirectional voltage regulation module includes a bidirectional buck / boost converter; The bidirectional buck / boost converter is used to step down / step up the electric energy of the charging pile energy storage battery and transmit it to the DC bus when the charging pile energy storage battery is used as a power source to supply power outward; and, when the charging pile energy storage battery is used as a load to receive electric energy, step down / step up the electric energy on the DC bus and transmit it to the charging pile energy storage battery.

7. The electric vehicle charging system according to any one of claims 1-4, characterized in that, The electric vehicle charging system further includes a bidirectional DC conversion module; One end of the bidirectional DC conversion module is connected to the DC bus, and the other end of the bidirectional DC conversion module is connected to the electric vehicle.

8. The electric vehicle charging system according to claim 7, wherein The bidirectional DC conversion module includes a plurality of parallel-connected dual active bridge converters; each of the dual active bridge converters includes a plurality of primary power tubes, a plurality of secondary power tubes, and a high-frequency transformer; The dual active bridge converter is used to convert the electric energy of the electric vehicle to the DC bus to charge the grid when the electric vehicle is used as a power source to supply power outward; and, when the electric vehicle is used as a load to receive electric energy, convert the bus voltage of the DC bus into the voltage required by the electric vehicle to charge the electric vehicle.

9. The electric vehicle charging system according to any one of claims 1-4, characterized in that, Two parallel capacitors are provided on the DC bus to jointly suppress the dynamic voltage fluctuations and ripple noise of the bus voltage on the DC bus through the energy storage characteristics and filtering characteristics of the capacitors.

10. The electric vehicle charging system according to any one of claims 1-4, characterized in that, The electric vehicle charging system includes multiple working modes; The multiple working modes include the grid charging the electric vehicle, the electric vehicle charging the grid, the grid charging the energy storage battery of the charging pile, the energy storage battery of the charging pile charging the grid, the energy storage battery of the charging pile charging the electric vehicle, the grid simultaneously charging the electric vehicle and the energy storage battery of the charging pile, and the electric vehicle and the energy storage battery of the charging pile simultaneously charging the grid.

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