Anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breaker

Abstract

The invention discloses an anti-islanding driving circuit suitable for a distributed photovoltaic grid-connected circuit breaker. The anti-islanding driving circuit comprises a DC-DC power supply circuit, a super-capacitor charging control circuit, a super-capacitor boost discharging circuit, a motor driving circuit, a motor charging linkage circuit and a motor current-limiting protection circuit. The DC-DC power supply circuit converts 12V input voltage into motor target voltage, the super capacitor charging control circuit adopts double NPN triodes and diodes to prevent reverse breakdown, and charging is stopped when the motor is started. The super capacitor boost discharge circuit supplies power to the motor when the main power supply is powered off. The motor driving circuit controls operation of a motor through logic level signals, a sampling resistor monitors input current, and the linkage circuit adopts AND gate logic peak shifting power utilization. And the current-limiting protection circuit realizes overcurrent protection through the current induction amplifier and the control triode. According to the invention, the photovoltaic grid-connected connection can be automatically disconnected, the islanding effect is prevented, and the reliability and the stability are high.

Description

Technical Field

[0001] The present invention relates to the field of motor drive circuits for photovoltaic power generation systems, and in particular to an anti-islanding drive circuit suitable for distributed photovoltaic grid-connected circuit breakers. Background Art

[0002] With the widespread application of distributed photovoltaic power generation systems, the safety and stability of their grid-connected operation have become an important guarantee for grid operation. However, due to the volatility and dispersion of photovoltaic power generation, when the main grid fails or the power is cut off for maintenance, the distributed photovoltaic power generation system may continue to feed power to the grid, forming "island operation". Island operation can cause equipment damage, grid failure, and even threaten the lives of maintenance personnel. Therefore, the power grid company has put forward mandatory anti-island protection requirements for photovoltaic grid-connected systems.

[0003] Most existing photovoltaic grid-connected circuit breakers use conventional motor drive circuits to achieve automatic power-off protection in the event of a fault. However, the traditional design has the following defects: Backup power supply and system main power supply are mixed: Existing systems usually share the backup power supply of the motor with the main power supply of the system, resulting in excessive consumption of the backup power supply when the motor is running, affecting the overall stability and power failure response capability of the system.

[0004] In traditional designs, the charging of supercapacitors and the operation of motors are often carried out simultaneously. Without reasonable scheduling of the power usage sequence, power competition is prone to occur, resulting in unstable motor operation or even failure to shut down normally.

[0005] Common motor driver chips only have a fixed overcurrent protection function, and do not have precise current limit settings for motors of different specifications, which can easily cause gear damage during stalling. In addition, they do not use a flexible overcurrent protection mechanism and cannot adapt to complex load changes in actual operation.

[0006] Some existing designs do not take into account the boost circuit and voltage protection functions, resulting in the output voltage of the supercapacitor being unable to meet the motor drive requirements when it is discharged, affecting the success rate of the emergency power-off operation.

[0007] To solve the above problems, there is an urgent need for an efficient, flexible and economical anti-islanding drive circuit design, which can automatically start when the main power supply is cut off, and ensure the stable operation of the circuit breaker and the safety of photovoltaic grid connection through power scheduling and motor current limiting protection functions. Summary of the invention

[0008] In order to solve the above problems, the present invention provides an anti-islanding drive circuit suitable for distributed photovoltaic grid-connected circuit breakers, which is equipped with an independent motor backup power supply to improve system reliability, stability and energy efficiency, and ensures "peak power consumption" of backup power supply charging and motor drive through a preset power management circuit. By monitoring the current of the motor power supply, it ensures that the motor can be reliably cut off when it is blocked to protect mechanical gears and other components.

[0009] The present invention is realized by the following technical scheme: an anti-islanding drive circuit suitable for distributed photovoltaic grid-connected circuit breakers, comprising: The DC-DC power supply circuit is used to convert the 12V input voltage from the switching power supply into the target operating voltage of the motor. The target voltage is provided to the motor driver chip as a driving power supply on the one hand, and is transmitted to the supercapacitor charging control circuit for backup power charging on the other hand; The supercapacitor charging control circuit is connected to the DC-DC power supply circuit and has a current limiting charging function. It stops charging when the motor starts. It is characterized by using dual NPN transistors to achieve charging control and using diodes to prevent reverse voltage breakdown; The supercapacitor boost discharge circuit is used to boost the energy stored in the supercapacitor to a motor drive voltage, and to dynamically discharge the energy under the control of the motor charging linkage circuit when the motor starts; The motor drive circuit receives the forward and reverse drive signals, monitors the motor input current through a sampling resistor connected in series to the power input terminal, and is connected to the motor current limiting protection circuit to realize motor overcurrent protection; The motor charging linkage circuit includes an AND gate logic circuit, which is used to perform logic operations on the motor forward and reverse control signals and output a charging control signal to control the supercapacitor charging process; The motor current limiting protection circuit includes a current sensing amplifier and a control transistor, which is used to monitor the motor input current. When overcurrent is detected, the control transistor is triggered to perform power-off protection; The anti-islanding driving circuit realizes the anti-islanding protection function of the distributed photovoltaic grid-connected system by driving the motor to disconnect the photovoltaic grid-connected connection when the main power supply fails.

[0010] As a preferred technical solution, the DC-DC power supply circuit includes a boost converter, whose output end is connected to the power input end of the motor drive chip and the input end of the supercapacitor charging control circuit, and the boost converter has overvoltage protection and undervoltage protection functions.

[0011] As a preferred technical solution, the supercapacitor charging control circuit includes two NPN transistors connected in series and two reverse parallel diodes, one of which is used to prevent reverse current when the supercapacitor is discharged, and the other is used to prevent voltage backflow at the DC-DC power supply end.

[0012] As a preferred technical solution, the supercapacitor boost discharge circuit includes a boost chip, whose input end is connected to the positive electrode of the supercapacitor, and whose output end is connected to the power input end of the motor drive chip through a current limiting resistor to prevent instantaneous large current from impacting the system.

[0013] As a preferred technical solution, the motor drive circuit is equipped with a power MOSFET drive module, and the gate of the power MOSFET receives a logic level signal from a control signal terminal to control the forward and reverse rotation and start and stop of the motor.

[0014] As a preferred technical solution, the motor charging linkage circuit includes an AND gate logic chip, whose input end is connected to the motor forward signal and reverse signal, and whose output end is connected to the start-stop control end of the supercapacitor charging control circuit.

[0015] As a preferred technical solution, the motor current limiting protection circuit is equipped with a current sensing amplifier, whose input end is connected to the sampling resistor at the motor power supply end, and the voltage difference signal at both ends is amplified to control the switching state of the transistor.

[0016] As a preferred technical solution, the motor drive chip drive output end is equipped with a reverse diode for absorbing the instantaneous current caused by the reverse electromotive force of the motor.

[0017] As a preferred technical solution, the supercapacitor charging control circuit includes a current limiting resistor, which is connected between the supercapacitor and the DC-DC power supply to limit the charging current of the supercapacitor and avoid damage to the charging circuit due to overcurrent.

[0018] As a preferred technical solution, the motor current limiting protection circuit further includes a transistor with a base resistor, whose base is connected to the output end of the current sensing amplifier. When an over-limit current is detected, the transistor is turned on and the motor drive signal is forcibly cut off.

[0019] The beneficial effects of the present invention are as follows: 1. The present invention adopts an independent motor backup power supply design based on supercapacitors, which avoids the risk of mixing with the system main power supply and ensures that a reliable driving power supply can still be provided to the motor when the main power supply is powered off, thereby greatly improving the reliability and power-off protection capability of the system; Second, the present invention integrates intelligent power scheduling management functions, automatically stops supercapacitor charging when the motor starts, avoids power resource competition, reduces system peak power consumption, and effectively reduces equipment capacity requirements and overall system costs. In addition, in view of the problem that traditional motor drive circuits lack flexible current limiting protection, the present invention realizes precise current limiting protection for the motor through the combined design of current sensing amplifiers and transistors, and can automatically cut off power supply when the motor is stalled or overloaded, preventing mechanical damage to key components such as gears, and enhancing the durability and stability of the equipment; 3. At the same time, the supercapacitor boost discharge circuit can be started immediately when the main power supply is cut off, ensuring that the motor completes the tripping operation in a short time, thereby improving the emergency response speed and execution success rate of the system. The present invention has modular structure, independent functions, strong adaptability, and can be widely used in distributed photovoltaic grid-connected circuit breaker equipment of different specifications. In addition, the system design also includes multiple safety measures such as overvoltage protection, undervoltage protection and reverse voltage protection, which further enhances the stability and electrical safety of the system operation; Through reasonable circuit design and control algorithm, the present invention improves the safety of photovoltaic grid-connected and system reliability while effectively controlling the hardware cost, and has good economic benefits and social value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 is a system block diagram of the present invention; Figure 2 A circuit schematic diagram of a DCDC power supply circuit portion of the present invention; Figure 3 This is a schematic diagram of the supercapacitor charging control circuit of the present invention; Figure 4 It is a schematic diagram of the supercapacitor boost discharge circuit of the present invention; Figure 5 is a circuit schematic diagram of the motor drive circuit of the present invention; Figure 6 It is a circuit principle diagram of the motor charging linkage circuit of the present invention; Figure 7 The circuit diagram of the motor current limiting protection circuit of the present invention is shown in FIG. DETAILED DESCRIPTION

[0022] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0023] Any feature disclosed in this specification (including any additional claims, abstract and drawings), unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0024] like Figure 1-Figure 7 As shown, an anti-islanding driving circuit suitable for a distributed photovoltaic grid-connected circuit breaker of the present invention comprises: The DC-DC power supply circuit is used to convert the 12V input voltage from the switching power supply into the target operating voltage of the motor. The target voltage is provided to the motor driver chip as a driving power supply on the one hand, and is transmitted to the supercapacitor charging control circuit for backup power charging on the other hand; The supercapacitor charging control circuit is connected to the DC-DC power supply circuit and has a current limiting charging function. It stops charging when the motor starts. It is characterized by using dual NPN transistors to achieve charging control and using diodes to prevent reverse voltage breakdown; The supercapacitor boost discharge circuit is used to boost the energy stored in the supercapacitor to a motor drive voltage, and to dynamically discharge the energy under the control of the motor charging linkage circuit when the motor starts; The motor drive circuit receives the forward and reverse drive signals, monitors the motor input current through a sampling resistor connected in series to the power input terminal, and is connected to the motor current limiting protection circuit to realize motor overcurrent protection; The motor charging linkage circuit includes an AND gate logic circuit, which is used to perform logic operations on the motor forward and reverse control signals and output a charging control signal to control the supercapacitor charging process; The motor current limiting protection circuit includes a current sensing amplifier and a control transistor, which is used to monitor the motor input current. When overcurrent is detected, the control transistor is triggered to perform power-off protection; The anti-islanding driving circuit realizes the anti-islanding protection function of the distributed photovoltaic grid-connected system by driving the motor to disconnect the photovoltaic grid-connected connection when the main power supply fails.

[0025] The following is a detailed description of the specific principles of each functional module: like Figure 2 As shown, first, the DC-DC power supply circuit is the core power management module of the drive circuit, and its main function is to convert the 12V input voltage from the switching power supply into the motor target operating voltage, such as 6V.

[0026] The DC-DC power supply circuit adopts a buck converter structure, which is mainly composed of a boost chip (such as ETA2845), a power inductor (such as 2.2uH) and an output filter capacitor (such as 10uF).

[0027] The input end is connected to the main power supply of the system, and after pulse modulation by the inductor and the buck chip, a stable motor operating voltage is generated at the output end.

[0028] In order to improve the stability of the system, the DC-DC power supply circuit integrates overvoltage protection and undervoltage protection functions to prevent abnormal input voltage from damaging the motor driver chip. The voltage output of the module not only supplies power to the motor driver chip, but also provides power input for the supercapacitor charging control circuit to ensure continuous charging of the supercapacitor.

[0029] like Figure 3 As shown in Figure 1, the supercapacitor charging control circuit uses two series-connected NPN transistors (such as Q1 and Q2) and two reverse-parallel diodes (such as D1 and D2) to form a current-limited charging circuit. The power input is connected to the positive electrode of the supercapacitor through a current-limiting resistor (such as R9). The current-limiting resistor is used to control the charging current to prevent instantaneous overcurrent from causing damage to the charging circuit; Diode D1 is used to prevent the supercapacitor from reversely discharging to the DC-DC power supply circuit when the power is off, while D2 is used to prevent the voltage reflux at the DC-DC power supply end from impacting the circuit. When the motor is not running, the supercapacitor is in a charging state. When the motor starts, the control signal from the motor charging linkage circuit triggers transistor Q1 to turn on, immediately cutting off the supercapacitor's charging circuit, avoiding power competition between the supercapacitor and the motor, and ensuring that the motor runs first.

[0030] When the main power fails, Figure 4 As shown, the supercapacitor boost discharge circuit is automatically activated to provide sufficient operating voltage for the motor. The core component of this circuit is the boost chip (such as ETA1061), whose input is connected to the positive electrode of the supercapacitor, and whose output is connected to the power input of the motor driver chip through diode D2; The boost chip has a built-in boost control circuit, which uses the internal power MOSFET to boost the energy in the supercapacitor according to the high-frequency switching principle to ensure that the output voltage meets the motor's operating requirements. In addition, the circuit also includes multiple filter capacitors (such as C9) to suppress high-frequency interference signals generated during the boost process and ensure stable power supply voltage when the motor is running.

[0031] like Figure 5As shown in the figure, the motor drive circuit is the execution module of the entire anti-islanding drive circuit. The motor drive chip (such as DRV8870) has dual output terminals, which are used for forward and reverse control of the motor. The control signal terminals (such as CTL_MOTOR_F and CTL_MOTOR_B) are connected to the direction control pins of the driver chip respectively. When a high-level control signal is received, the H-bridge circuit inside the driver chip is turned on, allowing the motor to run in the specified direction; The switch network composed of power MOSFET controls the running state of the motor when receiving the logic level signal. To protect the normal operation of the motor and the driver chip, the module is equipped with a reverse diode D3 to absorb the reverse electromotive force generated when the motor stops and avoid transient current shocks that damage the driver chip.

[0032] like Figure 6 As shown, the motor charging linkage circuit uses an AND gate logic chip (such as 74LV32) to control the charging process of the supercapacitor; When the forward signal and reverse signal of the motor are both at low levels, the AND gate chip outputs a low-level signal to activate the supercapacitor charging control circuit and start charging the supercapacitor. If any input signal is at a high level, it means that the motor is running, the AND gate chip outputs a high-level signal, and the supercapacitor charging process is stopped. This design ensures that the charging of the supercapacitor and the operation of the motor are staggered, avoiding power supply conflicts and energy waste.

[0033] like Figure 7 As shown in the figure, in order to protect the motor from stalling and overcurrent damage, the motor current limiting protection circuit uses a current sensing amplifier (such as INA180) combined with the control transistor Q3. The current sampling resistor R11 is connected in series to the motor power input end to monitor the motor's operating current in real time. The current sensing amplifier amplifies the voltage difference across the sampling resistor and outputs it to the base of the transistor Q3; When the current exceeds the set safety threshold, Q3 turns on, cuts off the motor drive signal, and forces the motor to stop running, thereby avoiding damage to mechanical structures such as gears and enhancing the stability and safety of the system.

[0034] The present invention realizes rapid power-off operation when the main power fails through precise power management, intelligent power scheduling and reliable motor protection mechanism, thus ensuring the stable and safe operation of the photovoltaic grid-connected system. The system has a reasonable structure and perfect functional module design, and can effectively adapt to distributed photovoltaic grid-connected circuit breaker equipment of different specifications, and has a wide range of market application potential.

[0035] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. An anti-islanding drive circuit suitable for distributed photovoltaic grid-connected circuit breakers, characterized in that: include: The DC-DC power supply circuit is used to convert the 12V input voltage from the switching power supply into the target operating voltage of the motor. The target voltage is provided to the motor driver chip as a driving power supply on the one hand, and is transmitted to the supercapacitor charging control circuit for backup power charging on the other hand; The supercapacitor charging control circuit is connected to the DC-DC power supply circuit and has a current limiting charging function. It stops charging when the motor starts. It is characterized by using dual NPN transistors to achieve charging control and using diodes to prevent reverse voltage breakdown; The supercapacitor boost discharge circuit is used to boost the energy stored in the supercapacitor to a motor drive voltage, and to dynamically discharge the energy under the control of the motor charging linkage circuit when the motor starts; The motor drive circuit receives the forward and reverse drive signals, monitors the motor input current through a sampling resistor connected in series to the power input terminal, and is connected to the motor current limiting protection circuit to realize motor overcurrent protection; The motor charging linkage circuit includes an AND gate logic circuit, which is used to perform logic operations on the motor forward and reverse control signals and output a charging control signal to control the supercapacitor charging process; The motor current limiting protection circuit includes a current sensing amplifier and a control transistor, which is used to monitor the motor input current. When overcurrent is detected, the control transistor is triggered to perform power-off protection; The anti-islanding driving circuit realizes the anti-islanding protection function of the distributed photovoltaic grid-connected system by driving the motor to disconnect the photovoltaic grid-connected connection when the main power supply fails.

2. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breaker according to claim 1, characterized in that: The DC-DC power supply circuit includes a boost converter, whose output end is connected to the power input end of the motor drive chip and the input end of the supercapacitor charging control circuit. The boost converter has overvoltage protection and undervoltage protection functions.

3. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The supercapacitor charging control circuit includes two NPN transistors connected in series and two reverse parallel diodes, wherein one diode is used to prevent reverse current when the supercapacitor is discharged, and the other diode is used to prevent voltage backflow at the DC-DC power supply end.

4. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The supercapacitor boost discharge circuit includes a boost chip, whose input end is connected to the positive electrode of the supercapacitor, and whose output end is connected to the power input end of the motor drive chip through a current limiting resistor to prevent instantaneous large current from impacting the system.

5. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The motor drive circuit is equipped with a power MOSFET drive module, and the gate of the power MOSFET receives a logic level signal from a control signal terminal to control the forward and reverse rotation and start and stop of the motor.

6. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The motor charging linkage circuit includes an AND gate logic chip, an input end of which is connected to the motor forward signal and reverse signal, and an output end of which is connected to the start-stop control end of the supercapacitor charging control circuit.

7. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The motor current limiting protection circuit is equipped with a current sensing amplifier, whose input end is connected to the sampling resistor at the motor power supply end, and the voltage difference signal at both ends is amplified to control the switching state of the transistor.

8. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The motor drive chip drive output end is equipped with a reverse diode for absorbing the instantaneous current caused by the reverse electromotive force of the motor.

9. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The supercapacitor charging control circuit includes a current limiting resistor, which is connected between the supercapacitor and the DC-DC power supply to limit the charging current of the supercapacitor and avoid damage to the charging circuit due to overcurrent.

10. The anti-islanding driving circuit suitable for distributed photovoltaic grid-connected circuit breakers according to claim 1, characterized in that: The motor current limiting protection circuit further includes a transistor with a base resistor, whose base is connected to the output end of the current sensing amplifier. When an over-limit current is detected, the transistor is turned on and the motor drive signal is forcibly cut off.

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