Isolated voltage sag active protection device

Abstract

The utility model discloses an isolation type voltage sag active protection device, which is arranged between a three-phase full-bridge rectification circuit and a frequency converter direct current bus, and comprises a full-bridge LLC resonant converter, a DSP digital control circuit and an isolation unit, and direct current output by the three-phase full-bridge rectification circuit is converted into stable direct current through the full-bridge LLC resonant converter. The isolation unit is connected with a frequency converter DC bus; wherein the DSP digital control circuit controls on and off of a switching tube in the full-bridge LLC resonant converter by generating a PWM signal. According to the isolation type voltage sag active protection device of the utility model, efficient and stable electric energy conversion is realized through the full-bridge LLC resonant converter and the DSP digital control circuit; and furthermore, through the isolation unit and the high-frequency isolation transformer, effective isolation between the power supply and the load is realized, and the system safety is improved.

Description

Technical Field

[0001] This utility model relates to voltage sag protection technology, and in particular to an isolated active voltage sag protection device. Background Technology

[0002] With the continuous development of DC power distribution technology, the requirements for the stable operation of DC loads and the efficiency, stability, and safety of active voltage sag protection devices are becoming increasingly stringent. Traditional active voltage sag protection devices have certain limitations in maintaining stable operation of loads under conditions of large voltage fluctuations and in providing system isolation, making it difficult to achieve effective isolation between the power supply and the load. Therefore, developing an active voltage sag protection device that can efficiently, stably, and safely convert the DC output from the power supply into stable DC and achieve input-output isolation is of great significance. Utility Model Content

[0003] Purpose of the utility model: The purpose of this utility model is to provide an isolated active voltage sag protection device that achieves efficient power conversion while effectively isolating the power supply from the load.

[0004] Technical Solution: To achieve the above objectives, the present invention provides an isolated active voltage sag protection device, which is installed between a three-phase full-bridge rectifier circuit and the DC bus of a frequency converter. The device includes a full-bridge LLC resonant converter, a DSP digital control circuit, and an isolation unit. The DC power output from the three-phase full-bridge rectifier circuit is converted into stable DC power by the full-bridge LLC resonant converter and then connected to the DC bus of the frequency converter through the isolation unit. The DSP digital control circuit generates PWM signals to control the switching transistors in the full-bridge LLC resonant converter to turn on and off.

[0005] The full-bridge LLC resonant converter includes a full-bridge circuit, an LLC resonant network, and a high-frequency isolation transformer. The full-bridge circuit consists of four power switching transistors, the LLC resonant network consists of a resonant inductor and a resonant capacitor, and the high-frequency isolation transformer provides electrical isolation between the input and output.

[0006] The DSP digital control circuit includes a voltage sampling module, a current sampling module, a PWM signal generation module, and a communication module.

[0007] The communication module is used for data transmission with the human-machine interface, the serial port time synchronization interface, and the RS485 communication interface.

[0008] The isolation unit includes an optocoupler.

[0009] Multiple sets of the isolated voltage sag active protection devices are connected in parallel between the three-phase full-bridge rectifier circuit and the inverter DC bus.

[0010] Beneficial effects: The present invention has the following advantages: 1. The isolated voltage sag active protection device of the present invention achieves efficient and stable power conversion through a full-bridge LLC resonant converter and DSP digital control circuit; and further achieves effective isolation between the power supply and the load through the isolation unit and high-frequency isolation transformer, thereby improving system safety;

[0011] 2. Through real-time monitoring and dynamic adjustment of the DSP digital control circuit, intelligent control of the full-bridge LLC resonant converter is realized, ensuring the stable operation of the system;

[0012] 3. Add a serial port time synchronization interface to significantly improve the time synchronization accuracy of the device and the reliability of the system, and avoid protection malfunctions or delays caused by time deviations.

[0013] 4. Multiple isolated voltage sag active protection devices are operated in parallel, which improves the power output capacity, redundancy and reliability of the system. Attached Figure Description

[0014] Figure 1 A schematic diagram of the topology of an isolated voltage sag active protection device;

[0015] Figure 2 This is the circuit schematic of a full-bridge LLC resonant converter;

[0016] Figure 3 A schematic diagram showing the connection of an isolated voltage sag active protection device between the three-phase full-bridge rectifier circuit and the DC bus of the frequency converter.

[0017] Figure 4 This is a DSP digital control circuit diagram;

[0018] Figure 5 This is a software flowchart for DSP control.

[0019] Figure 6 This is a schematic diagram of two isolated voltage sag active protection devices connected in parallel. Detailed Implementation

[0020] The technical solution of this utility model will be described in detail below with reference to the embodiments and accompanying drawings.

[0021] like Figure 1 , 2As shown, the isolated voltage sag active protection device is installed between the three-phase full-bridge rectifier circuit and the inverter's DC bus. Specifically, it includes a full-bridge LLC resonant converter, a DSP digital control circuit, an isolation unit, a human-machine interface, a serial time synchronization interface, and an RS485 communication interface. The DSP digital control circuit generates PWM signals to control the switching transistors in the full-bridge LLC resonant converter, while simultaneously monitoring input and output voltage, current, and other parameters in real time. Based on feedback, it dynamically adjusts the control strategy to ensure stable output. The DC power output from the three-phase full-bridge rectifier circuit is converted into stable DC power by the full-bridge LLC resonant converter, and then connected to the inverter's DC bus through the isolation unit to provide power to DC loads such as the inverter. The human-machine interface, RS485 communication interface, and serial time synchronization interface are connected to the DSP digital control circuit to realize user operation, system monitoring, and data communication functions.

[0022] like Figure 3 As shown, the full-bridge LLC resonant converter includes a full-bridge circuit structure, an LLC resonant network, a high-frequency isolation transformer T, and a rectifier and filter circuit. Its working principle is as follows: the input DC power is first inverted by the full-bridge circuit structure to convert it into high-frequency AC power. The LLC resonant network processes the high-frequency AC power, the high-frequency isolation transformer isolates and transmits the processed AC power, and the rectifier and filter circuit converts the high-frequency AC power into a stable DC power output. The full-bridge circuit structure consists of four power switching transistors (such as IGBT modules), which use PWM control to invert the input DC power. The LLC resonant network consists of resonant inductors (Lr, Lm) and resonant capacitors (Cr), achieving soft-switching characteristics and improving conversion efficiency. The rectifier and filter circuit uses a full-bridge rectifier structure, combined with filter capacitor C2, to ensure the stability and low ripple of the output DC power.

[0023] like Figure 4 As shown, the DSP digital control circuit uses a high-performance digital signal processor STM32F103RBCT6. Its peripheral circuits include voltage sampling, current sampling, PWM signal output, and communication interfaces. The input voltage sampling terminal Ui and the output voltage sampling terminal Uo are connected to the DSP's AD sampling ports (AN0 and AN2) through a resistor divider network, respectively, to achieve real-time monitoring of the input and output voltages of the full-bridge LLC resonant converter circuit. The input current sampling and output current sampling of the full-bridge LLC resonant converter circuit are connected to the DSP's AN1 and AN3 ports through current sensors to ensure accurate acquisition of current signals. The DSP performs digital signal processing based on the sampled signals to generate corresponding PWM control signals (PWM1-PWM4) to control the power switching transistors of the full-bridge LLC resonant converter, realizing closed-loop control of the converter.

[0024] The human-machine interface includes a parameter setting module, an operation status monitoring module, and a fault diagnosis module, allowing users to operate and monitor the system. The serial port time synchronization interface is used for system time calibration and synchronization, ensuring time accuracy during long-term operation. The RS485 communication interface enables bidirectional data transmission, connects to the DSP digital control circuit, and can communicate with a host computer or other devices.

[0025] like Figure 5 As shown, the working process of the isolated voltage sag active protection device is as follows:

[0026] After the system powers on, the DSP digital control circuit completes initialization and begins executing the control program. Input voltage, input current, output voltage, and output current signals are acquired through the AD sampling unit to provide data support for the control algorithm. The main loop includes a current control subroutine and an active protection calculation subroutine.

[0027] The output value calculated by the current control loop is compared with the output value calculated by the tracking control loop. The smaller value is taken as the input of the PWM signal register to generate a PWM drive signal, which controls the on and off of the power transistor in the power circuit, thereby realizing the voltage, current and maximum power point tracking control of the converter and the photovoltaic cell.

[0028] Meanwhile, in the active protection main program, the DSP controller monitors the device's input voltage, current, output voltage, current, temperature, and other parameters in real time. If these parameters exceed the threshold, the device immediately initiates active protection, locking the output; once the parameters return to normal, the device will restart. Furthermore, if a short-circuit fault occurs at the device's output or on the DC load, the DSP controller immediately shuts off the power transistor's drive signal, locking the output to ensure that the short-circuit fault at the output does not propagate to the input, thus protecting and isolating the power supply and load.

[0029] Multiple active voltage sag protection devices can be connected in parallel to provide DC load output, such as... Figure 6 As shown, multiple active voltage sag protection devices are connected in parallel and then connected to the DC bus of the frequency converter through an output isolation unit, jointly providing power to the DC loads such as the frequency converter. This parallel operation mode not only improves the system's power output capability but also enhances the system's redundancy and reliability.

Claims

1. An isolated voltage sag active protection device, which is arranged between a three-phase full-bridge rectifier circuit and a frequency converter DC bus, characterized in that, The full-bridge LLC resonant converter, a DSP digital control circuit, an isolation unit, and a three-phase full-bridge rectifier circuit are included.

2. The isolated voltage sag active protection device according to claim 1, characterized in that, The DSP digital control circuit controls the conduction and turn-off of the switch tube in the full-bridge LLC resonant converter by generating a PWM signal.

3. The isolated voltage sag active protection device according to claim 1, characterized in that, The full-bridge LLC resonant converter includes a full-bridge circuit, an LLC resonant network, and a high-frequency isolation transformer.

4. The isolated voltage sag active protection device according to claim 3, characterized in that, The DSP digital control circuit includes a voltage sampling module, a current sampling module, a PWM signal generation module, and a communication module.

5. The isolated voltage sag active protection device according to claim 1, wherein, The communication module is used for data transmission with a human-computer interaction interface, a serial port time correction interface, and an RS485 communication interface.

6. The isolated voltage sag active protection device according to claim 1, wherein, The isolation unit includes an optoelectronic coupler. Multiple sets of the isolation-type voltage sag active protection device are arranged in parallel between the three-phase full-bridge rectifier circuit and the frequency converter DC bus.

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