CN-121984148-A - Electric automobile charging system and control method thereof

CN121984148ACN 121984148 ACN121984148 ACN 121984148ACN-121984148-A

Abstract

The invention belongs to the technical field of charging systems, and provides an electric vehicle charging system and a control method thereof, which aim to solve the problems of unbalanced proportion of the electric vehicle to the charging system, possible phase failure of a power grid, compatibility of different charging voltage levels and the like. The system comprises an alternating-current/direct-current conversion output module and a cluster charging module, wherein the alternating-current/direct-current conversion output module is an AC/DC converter compatible with multi-mode alternating-current input, the topology is kept when three phases are input based on a three-phase six-switch PFC circuit topology, the three phases can be respectively converted into conditions of adapting to one-phase input and two-phase input, stable direct-current bus voltage is output under three input conditions, the cluster charging module comprises a plurality of independent isolated DC/DC converters, each converter is connected with the alternating-current/direct-current conversion output module through a common direct-current bus, and can output 400V and 800V direct current, and can charge a plurality of electric vehicles with different voltage requirements.

Inventors

ZHOU KAI
WEI MENG
JIN NINGZHI
SUN DONGYANG
GENG XIN
WANG XUDONG

Assignees

哈尔滨理工大学

Dates

Publication Date: 20260505
Application Date: 20260106

Claims (10)

1. The electric automobile charging system is characterized by comprising an alternating-current/direct-current conversion output module and a cluster charging module; The alternating current-direct current conversion output module is an AC/DC converter compatible with a multimode alternating current input function, and is based on a three-phase six-switch PFC circuit topology, wherein the basic topology is maintained during three-phase alternating current input, and the basic topology can be respectively converted into a topological structure of cascade connection of a two-phase staggered totem-pole PFC circuit adapting to a lack of alternating current input, a totem-pole PFC circuit adapting to a lack of two-phase alternating current input and a boost circuit through switch switching, so that stable direct current bus voltage is output under three alternating current input conditions; the cluster charging module comprises a plurality of independent isolated DC/DC converters, each isolated DC/DC converter is connected with the AC/DC conversion output module through a common DC bus, and each independent isolated DC/DC converter can output 400V and 800V direct current at two grades; the cluster charging module is used for simultaneously charging a plurality of electric vehicles with different voltage requirements.
2. The electric vehicle charging system of claim 1, wherein the multi-mode operation of the ac-dc conversion output module comprises: the three-phase input mode is to disconnect the switches K1, kb and Kc of the AC/DC conversion output module, shift the switches K2-K4 to 1 gear, and topologically switch into a three-phase six-switch PFC circuit; in the phase-missing input mode, taking C phase missing as an example, a switch K1 of the AC-DC conversion output module is closed, switches K2 and K3 of the switch K1 are shifted to 1 gear, a switch K4 is shifted to 2 gear, switches Kb and Kc of the switch K4 are opened, the topology is switched into a two-phase staggered parallel totem pole PFC circuit, And in the two-phase-missing input mode, taking a B phase and a C phase missing phase as examples, closing switches K1 and Kb of the alternating-current-direct current conversion output module, shifting switches K2 and K3 to 2 gears and K4 to 1 gear, opening a switch Kc of the alternating-current-direct current-conversion output module, and switching the topology into a cascading structure of totem pole PFC and a boost circuit.
3. The electric vehicle charging system according to claim 2, wherein the open-phase of the open-phase input mode is not limited to the C-phase, and corresponds to on-off and gear states of the switches K1, K2-K4, kb, kc of the ac/dc conversion output module, so as to switch to a two-phase interleaved totem-pole PFC circuit topology according to the actual open-phase adaptation setting.
4. The electric vehicle charging system according to claim 2, wherein the open-phase of the open-phase input mode is not limited to B-phase and C-phase, and corresponds to on-off and gear states of the switches K1, kb, kc, K2-K4 of the ac/dc conversion output module, so as to switch to a cascade topology of totem pole PFC and boost circuit according to the actual open-phase adaptation setting.
5. The electric vehicle charging system according to claim 2, wherein in the three-phase input mode, the power element is controlled by a space voltage vector pulse width modulation technique, so that the input current is in phase with the input voltage and the waveform approximates to a sine wave, and the power factor correction is realized.
6. The electric automobile charging system according to claim 2, wherein in the absence of a phase input mode, when the network side input current is in a positive half period, the power frequency switching tube S7 is constantly cut off, and S8 is constantly switched on, when the network side input current is in a negative half period, the power frequency switching tube S7 is constantly switched on, and S8 is constantly switched off, two high-frequency bridge arms work alternately at 180 degrees, and two inductance currents are lifted alternately at 180 degrees.
7. The electric vehicle charging system of claim 1, wherein each isolated DC/DC converter employs a high frequency power transformer having a primary side dual input + secondary side dual output multiport configuration.
8. The electric vehicle charging system of claim 7, wherein the cluster charging module comprises: The primary side circuit of the transformer works, namely energy coupling and transmission are realized through a high-frequency power transformer, the sum of primary side input power is equal to the sum of output power of each secondary side, and the balance relation of the primary side ampere turns and the secondary side ampere turns is met; When a plurality of electric automobiles are charged simultaneously, the secondary side circuit of the transformer keeps the equal proportion change of the switching frequency of the power elements of the primary side circuit and the secondary side circuit, and the voltage of each output port is stabilized by independently adjusting the external phase shift angle between the primary side circuit and the secondary side circuit.
9. The electric vehicle charging system of claim 8, wherein the voltage waveforms across the inductor satisfy a volt-second balance during one switching cycle when the converter is operating in steady state, the voltage waveforms across the inductor approximate a square wave when the two sets of switches are operating in complementary fashion, and the amplitude of the square wave is adjusted by PWM.
10. A control method for a charging system according to any one of claims 1-9, characterized in that the charging system employs a frequency + pulse width + phase three parameter compound control method, which combines PWM control, PFM control and PS control, wherein PWM is used to control the ac-dc conversion output module, PFM and PS are used to cooperatively control the cluster charging module, so as to realize efficient and stable control of the entire charging system.

Description

Electric automobile charging system and control method thereof Technical Field The invention belongs to the technical field of charging systems, and particularly relates to an electric automobile charging system and a control method thereof. Background The industrialization of electric vehicles is a system engineering, and charging infrastructure is one of the most important links. The electric automobile charging system is used as a power conversion interface between an automobile and a power grid, the performance index of the electric automobile charging system is closely related to the charging efficiency and the charging quality of the electric automobile, and meanwhile, the service life of a power battery is directly influenced. The invention focuses on the technical bottleneck of the problem of difficult charging of the electric automobile, aims at realizing the practical engineering application of a novel charging system, and aims at solving the problems of unbalanced proportion of the electric automobile and the charging system and compatibility of different charging voltage grades. Conventional charging systems may be structurally divided into a front stage Power Factor Correction (PFC) circuit, i.e., an alternating current/direct current converter (AC/DC) section, and a rear stage direct current/direct current converter (DC/DC) section. The front-stage converter is mainly used for realizing power factor correction so as to reduce harmonic pollution of a charging system to a power grid and supply power for a rear stage and an auxiliary power supply, and the rear-stage converter is directly used for providing electric isolation and corresponding charging conditions for a high-voltage power battery of an electric automobile. At present, most of the mainstream electric vehicles in China adopt 400V platforms, the charging voltage is generally 300-500V, and an 800V high-voltage architecture is gradually developed, so that the electric vehicles are expected to become the mainstream voltage platforms of next-generation electric vehicles, and therefore, a charging system compatible with 400V and 800V voltage levels is researched and matched with the development direction of the electric vehicles. The invention aims to use a PFC circuit with a compatible multimode alternating current input function as a front stage, integrate 400V and 800V charging circuits in a rear stage converter by utilizing a multiport high-frequency power transformer, and realize 'one-machine group charging' by adopting a multimode common direct current bus mode. The method is helpful for reducing the overall volume of the system and improving the power density. Disclosure of Invention The invention provides an electric vehicle charging system and a control method thereof, which aim to solve the problems of unbalanced proportion of the electric vehicle and the charging system, possible phase-failure of a power grid, compatibility of different charging voltage levels and the like. In order to achieve the above purpose, the present invention provides the following technical solutions: In a first aspect, the invention provides an electric vehicle charging system, which comprises an alternating current-direct current conversion output module and a cluster charging module; The alternating current-direct current conversion output module is an AC/DC converter compatible with a multimode alternating current input function, and is based on a three-phase six-switch PFC circuit topology, wherein the basic topology is maintained during three-phase alternating current input, and the basic topology can be respectively converted into a topological structure of cascade connection of a two-phase staggered totem-pole PFC circuit adapting to a lack of alternating current input, a totem-pole PFC circuit adapting to a lack of two-phase alternating current input and a boost circuit through switch switching, so that stable direct current bus voltage is output under three alternating current input conditions; the cluster charging module comprises a plurality of independent isolated DC/DC converters, each isolated DC/DC converter is connected with the AC/DC conversion output module through a common DC bus, and each independent isolated DC/DC converter can output 400V and 800V direct current at two grades; the cluster charging module is used for simultaneously charging a plurality of electric vehicles with different voltage requirements. Further, the multimode working process of the ac-dc conversion output module includes: the three-phase input mode is to disconnect the switches K1, kb and Kc of the AC/DC conversion output module, shift the switches K2-K4 to 1 gear, and topologically switch into a three-phase six-switch PFC circuit; in the phase-missing input mode, taking C phase missing as an example, a switch K1 of the AC-DC conversion output module is closed, switches K2 and K3 of the switch K1 are shifted to 1 gear, a switch K4 is shifted to 2 gear, switch