Harmonic suppression device for three-phase alternating current charging pile

Abstract

The invention discloses a harmonic suppression device for a three-phase alternating current charging pile, and relates to the field of harmonic suppression, the harmonic suppression device comprises a plurality of filtering devices which are designed for harmonic waves with different frequencies, and each filtering device comprises a core controller, a plurality of LCR filtering modules connected in parallel, a communication module and a fault detection module; the filtering devices are correspondingly connected to each phase line of a three-phase power supply, the core controllers of the filtering devices are connected through a data bus to form a three-phase cooperative control network, the communication module is in communication connection with the intelligent electric meter of the charging pile, and three-phase load current signals are collected in real time; the core controller carries out fast Fourier transform (FFT) analysis, identifies the five-time, seven-time and eleventh-time harmonic content of each phase, and switches the LCR filtering modules in a grading manner according to a preset THDi threshold value, thereby achieving the dynamic response and precise treatment of harmonic waves.

Description

A harmonic mitigation device for three-phase AC charging piles Technical Field

[0001] This invention belongs to the field of harmonic mitigation, specifically relating to a harmonic mitigation device for three-phase AC charging piles. Background Technology

[0002] With the rapid popularization of new energy vehicles, three-phase AC charging piles are widely used in residential areas, commercial buildings, and other scenarios due to their high charging power and wide compatibility with various vehicle models. However, the rectifier circuit inside the charging pile, as a typical nonlinear load, generates a large amount of high-order harmonic currents, mainly the 5th, 7th, and 11th harmonics, during operation. These harmonics, injected into the power distribution network, can cause a series of power quality problems, such as increased line and transformer losses, three-phase current imbalance, and relay protection malfunctions.

[0003] Existing three-phase harmonic mitigation devices mostly adopt a "fixed filtering" mode, that is, a fixed filter module is preset and put into operation for a long time. It cannot be dynamically adjusted according to the real-time changes in harmonic frequency and content. This results in increased losses due to redundant operation of the module under low harmonic conditions, and insufficient mitigation under high harmonic conditions.

[0004] Furthermore, most devices lack a rapid linkage mechanism with the smart meters of charging piles, resulting in delayed load start-up detection. Additionally, each phase operates independently, lacking three-phase coordinated control capabilities, making it difficult to effectively resolve three-phase imbalance issues. Fault detection functions are also relatively weak, typically only able to detect overall device failures without pinpointing specific faulty modules, thus affecting the continuity of treatment. Summary of the Invention

[0005] To address the problems of response lag, insufficient control accuracy, and lack of coordinated control in existing harmonic mitigation devices, this invention provides a harmonic mitigation device for three-phase AC charging piles.

[0006] The solution adopted by this invention to solve its technical problem is as follows: a harmonic mitigation device for a three-phase AC charging pile, comprising multiple filtering devices designed for harmonics of different frequencies. Each filtering device includes a core controller, multiple parallel LCR filtering modules, a communication module, and a fault detection module. The filtering devices are connected to each phase of the three-phase power supply, and the core controllers of each filtering device are connected via a data bus to form a three-phase collaborative control network. The communication module is used to establish a communication connection with the smart meter of the charging pile to acquire the three-phase load current signal in real time. The core controller is configured to: identify the harmonic content based on the load current signal and dynamically control the switching of the corresponding LCR filtering module based on the identification result; and simultaneously interact with the core controllers of other filtering devices via the data bus to collaboratively adjust the switching strategy of each phase LCR filtering module to achieve three-phase harmonic mitigation and current balance control.

[0007] Preferably, the core controller uses an FPGA development board and has a built-in harmonic signal processing chip, logic control unit and data storage unit.

[0008] Preferably, the LCR filter module consists of an inductor, a capacitor, and a power resistor forming a series resonant circuit, and each module is equipped with an independent IGBT electronic switch.

[0009] Preferably, the electronic switch is an insulated gate bipolar transistor with a switching response time of no more than 10 microseconds.

[0010] Preferably, the communication module is an isolated RS485 chip with overvoltage and overcurrent protection functions.

[0011] Preferably, the fault detection module integrates a voltage sensor, a current sensor, and a PT100 temperature sensor to collect real-time data on the terminal voltage, branch current, and component temperature of the LCR filter module and transmit it to the core controller. The core controller is configured to control the corresponding electronic switch to disconnect when the terminal voltage, branch current, or component temperature exceeds a preset safety threshold, thereby disconnecting the faulty module.

[0012] Preferably, the core controller has a built-in backup power module, which can maintain the operation of the device when the AC power supply is momentarily interrupted.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention communicates with the smart meter of the charging pile through the communication module, collects the three-phase load current signal in real time, performs fast Fourier transform (FFT) analysis by the core controller, identifies the 5th, 7th and 11th harmonic content of each phase, and switches the LCR filter module according to the preset THDi threshold, thereby realizing dynamic response and precise control of harmonics.

[0014] 2. This invention connects three filtering devices to the U, V, and W phases of a three-phase power supply, respectively. The core controller forms a collaborative control network through a data bus to synchronize the governance status of each phase in real time. When the three-phase current deviation is detected to exceed a set threshold (e.g., 5%), the system automatically and collaboratively adjusts the switching combination of the LCR modules of each phase, effectively suppressing the three-phase imbalance problem caused by single-phase load fluctuations and improving the stability of the power grid.

[0015] 3. The fault detection module of this invention monitors voltage, current and temperature in real time. Once the voltage exceeds the safety threshold, the fault module is immediately disconnected and reported, ensuring the continuous operation and rapid recovery of the system under fault conditions.

[0016] 4. This invention supports receiving remote commands via RS485 interface, and can flexibly modify parameters such as harmonic mitigation threshold, load start-up threshold, and three-phase current balance deviation threshold to adapt to the charging pile operation requirements in different scenarios such as residential communities and commercial buildings. Furthermore, the core controller adopts a domestic FPGA development board, which takes into account both technological independence and cost advantages. The modular design and independent electronic switch configuration of the LCR filter module facilitate future expansion and maintenance. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the system access of the device of the present invention; Figure 2 is a block diagram of the collaborative control structure of the three-phase filter device of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Please refer to Figures 1-2. The present invention provides a technical solution for a harmonic control device for a three-phase AC charging pile: Embodiment 1: As shown in Figures 1 and 2, it includes three filtering devices designed for the 5th, 7th, and 11th harmonics, respectively. The three filtering devices correspond to the U-phase, V-phase, and W-phase lines of the three-phase power supply.

[0020] Each filter unit has the same structure, including a core controller, four sets of parallel LCR filter modules, a communication module, and a fault detection module. The LCR filter modules are designed to adapt to harmonic frequencies, and the LCR modules of the three filter units resonate specifically at the 5th, 7th, and 11th harmonic frequencies to ensure filtering accuracy.

[0021] The core controllers of the three filter devices are connected by a data bus to form a three-phase collaborative control network, which can realize real-time synchronization and collaborative adjustment of the treatment status data of each phase.

[0022] One end of the communication module establishes a communication connection with the smart meter of the charging pile, and the other end is connected to the core controller to transmit load current signals and command information. The communication module is an RS485 chip and adopts an isolated design with overvoltage and overcurrent protection functions to avoid power grid interference affecting data transmission.

[0023] The core controller is configured to: identify the harmonic content based on the load current signal, and dynamically control the switching of the corresponding LCR filter module based on the identification result; at the same time, it interacts with the core controllers of other filtering devices through the data bus to coordinate and adjust the switching strategy of each phase LCR filter module to achieve three-phase harmonic control and current balance control.

[0024] In practical use, this invention provides a harmonic mitigation device for three-phase AC charging piles. First, the device is installed after the smart meter and before the load of the three-phase charging pile. The smart meter collects the three-phase load current data in real time and continuously transmits the current signal to the core controller of each phase via a communication module. The core controller determines in real time whether the current exceeds a preset load start threshold. When the current of any phase reaches or exceeds this threshold, the harmonic mitigation process is immediately initiated. When the threshold is not reached, the device maintains a low-power standby state. The core controller performs a Fast Fourier Transform (FFT) on the received current signal, decomposing the fundamental wave and the 5th, 7th, and 11th harmonic components, calculating the total harmonic distortion (THDi) of each harmonic, and switching the LCR filter modules according to the following rules: when the THDi of a certain harmonic in a certain phase exceeds 8% (first threshold), the electronic switches of two sets of LCR filter modules are closed; when the THDi exceeds 12% (second threshold), the electronic switches of three sets of LCR filter modules are closed; when the THDi exceeds 15% (third threshold), all four sets of LCR filter modules are closed. The filter module has an electronic switch; at the same time, the core controller synchronizes the three-phase current data through the data bus and calculates the three-phase current deviation. If the deviation exceeds 5%, the switching combination of the LCR modules of each phase is adjusted through the collaborative control network (such as reducing one set of modules in one phase and adding one set of modules in another phase) until the three-phase current deviation is ≤5%, taking into account both harmonic control and three-phase balance.

[0025] II. Example 2: This example differs from Example 1 in the following ways: The core controller uses a domestic FPGA development board and has a built-in harmonic signal processing chip, logic control unit, data storage unit and backup power module.

[0026] Among them, the backup power module can maintain the core functions of the device for ≥10 seconds when the AC power supply is momentarily interrupted, thus avoiding power outage.

[0027] The LCR filter module consists of a series resonant circuit composed of an inductor, a capacitor, and a power resistor. Each module is equipped with an independent IGBT electronic switch. The electronic switch is an insulated gate bipolar transistor, and its switching response time is no more than 10 microseconds. Compared with traditional relay switches, it significantly improves the switching speed of the filter module and shortens the response time of harmonic mitigation.

[0028] The fault detection module integrates a voltage sensor, a current sensor, and a PT100 temperature sensor to collect real-time data on the terminal voltage, branch current, and component temperature of the LCR filter module and transmit it to the core controller. The core controller is configured to control the corresponding electronic switch to disconnect when the terminal voltage, branch current, or component temperature exceeds a preset safety threshold, thereby disconnecting the faulty module.

[0029] The core controller has a built-in "treatment effect feedback adjustment" logic; after the LCR module is put into operation for the first time, THDi and three-phase balance are re-checked every 100ms. If the standard is not met (THDi>8% or current deviation>5%), one set of LCR modules is added or removed for fine adjustment. The single adjustment interval is not less than 50ms to avoid frequent operation.

[0030] The device supports sending RS485 commands to the core controller via a host computer or remote control terminal to modify the load start threshold, harmonic content classification threshold (8%, 12%, 15%), and three-phase current balance deviation threshold (5%).

[0031] For example, for high-power charging piles in commercial buildings, the third harmonic threshold can be lowered to 14% to improve governance sensitivity; for low-power charging piles in residential areas, the load start threshold can be raised to reduce unnecessary standby power consumption.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit its scope of protection. Any modifications or equivalent substitutions to the component structure and control parameters without departing from the design principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A harmonic mitigation device for three-phase AC charging piles, characterized in that, The system includes multiple filtering devices, each designed to target harmonics at different frequencies. Each filtering device comprises a core controller, multiple parallel LCR filter modules, a communication module, and a fault detection module. The filtering devices correspond to the respective phases of a three-phase power supply, and the core controllers of each filtering device are connected via a data bus to form a three-phase collaborative control network. The communication module establishes a communication connection with the smart meter of the charging pile to acquire the three-phase load current signal in real time. The core controller is configured to: identify the harmonic content based on the load current signal and dynamically control the switching of the corresponding LCR filter module based on the identification result; simultaneously, it interacts with the core controllers of other filtering devices via the data bus to collaboratively adjust the switching strategy of each phase LCR filter module, thereby achieving three-phase harmonic mitigation and current balance control.

2. The harmonic mitigation device for three-phase AC charging piles according to claim 1, characterized in that: The core controller uses an FPGA development board and has a built-in harmonic signal processing chip, logic control unit and data storage unit.

3. The harmonic mitigation device for three-phase AC charging piles according to claim 1, characterized in that: The LCR filter module consists of an inductor, a capacitor, and a resistor forming a series resonant circuit, and each LCR filter module is connected in series with an independent electronic switch.

4. The harmonic mitigation device for three-phase AC charging piles according to claim 3, characterized in that: The electronic switch is an insulated gate bipolar transistor.

5. The harmonic mitigation device for three-phase AC charging piles according to claim 1, characterized in that: The communication module is an isolated RS485 chip.

6. The harmonic mitigation device for three-phase AC charging piles according to claim 1, characterized in that: The fault detection module integrates a voltage sensor, a current sensor, and a temperature sensor.

7. The harmonic mitigation device for three-phase AC charging piles according to claim 1, characterized in that: The core controller has a built-in backup power module, which can maintain the operation of the device when the AC power supply is momentarily interrupted.

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