An anti-islanding drive circuit suitable for a distributed photovoltaic grid-connected circuit breaker

Abstract

The application discloses a kind of to be suitable for distributed photovoltaic grid-connected circuit breaker's anti-islanding drive circuit, including DC-DC power supply circuit, super capacitor charging control circuit, super capacitor boost discharge circuit, motor drive circuit, motor charging linkage circuit and motor current-limiting protection circuit.DC-DC power supply circuit converts 12V input voltage into motor target voltage, super capacitor charging control circuit uses double NPN triode and diode to prevent reverse breakdown, and charging is stopped when motor starts.Upon mains power failure, super capacitor boost discharge circuit supplies power to the motor.Motor drive circuit controls motor operation through logic level signal, sampling resistor monitors input current, and linkage circuit uses AND gate logic to peak-shaving electricity.Current-limiting protection circuit realizes overcurrent protection through current sensing amplifier and control triode.The application can automatically disconnect photovoltaic grid connection, prevent islanding effect, and has high reliability and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor drive circuits for photovoltaic power generation systems, specifically to an anti-islanding drive circuit suitable for distributed photovoltaic grid-connected circuit breakers. BACKGROUND

[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 power grid operation. However, due to the volatility and dispersion of photovoltaic power generation, when the main power grid fails or is under maintenance, the distributed photovoltaic power generation system may continue to feed power to the grid, forming an "island operation". Island operation can cause equipment damage, power grid failure, and even threaten the lives of maintenance personnel. Therefore, power grid companies have made mandatory anti-islanding 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, traditional designs have the following shortcomings:

[0004] Mixing backup power supply with system main power supply:

[0005] Existing systems usually share the backup power supply of the motor with the system main power supply, resulting in excessive consumption of the backup power supply when the motor is running, affecting the overall stability and power-off response capability of the system.

[0006] In traditional designs, the charging of supercapacitors and the operation of motors often occur simultaneously, without proper scheduling of power usage timing, which can lead to power competition and unstable motor operation or even failure to properly trip.

[0007] Common motor drive chips only have fixed value overcurrent protection functions, without precise current limiting settings for different specifications of motors, which can easily cause gear damage during stall. In addition, flexible overcurrent protection mechanisms are not used, which cannot adapt to complex load changes in actual operation.

[0008] Some existing designs do not consider the boost circuit and voltage protection function, resulting in the output voltage of the supercapacitor not meeting the motor drive requirements when discharging, affecting the success rate of emergency power-off operations.

[0009] To solve the above problems, there is an urgent need for an efficient, flexible, and economical anti-islanding drive circuit design that can automatically start when the main power supply is disconnected 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

[0010] In order to solve the above problems, the application provides an anti-island driving circuit suitable for a distributed photovoltaic grid-connected circuit breaker, which is equipped with an independent motor backup power supply to improve system reliability, stability and energy efficiency ratio, a preset power supply management circuit is used to ensure that the backup power supply is charged and the motor driving is "peak-shaving power consumption", and the current monitoring of the motor power supply is used to ensure that the motor can be reliably cut off when it is blocked to protect mechanical gear components.

[0011] The application is realized by the following technical scheme: an anti-island driving circuit suitable for a distributed photovoltaic grid-connected circuit breaker, comprising:

[0012] A DC-DC power supply circuit is used to convert a 12V input voltage from a switching power supply into a target working voltage of the motor, which is provided to a motor driving chip as a driving power supply on one hand and is transmitted to a super capacitor charging control circuit for backup power charging on the other hand;

[0013] The super capacitor charging control circuit is connected to the DC-DC power supply circuit and has a current-limiting charging function and stops charging when the motor starts, characterized in that a double NPN triode is used to realize charging control and a diode is used to prevent reverse voltage breakdown;

[0014] A super capacitor voltage-boosting discharging circuit is used to boost the energy stored in the super capacitor to a motor driving voltage and dynamically discharge under the control of a motor charging linkage circuit when the motor starts;

[0015] The motor driving circuit receives forward and reverse driving signals, monitors the motor input current through a sampling resistor connected in series with the power supply input end, and is connected to a motor current-limiting protection circuit to realize motor overcurrent protection;

[0016] The motor charging linkage circuit comprises an AND logic circuit, which is used to logically operate the motor forward and reverse control signals and output a charging control signal to control the super capacitor charging process;

[0017] The motor current-limiting protection circuit comprises a current sensing amplifier and a control triode, which is used to monitor the motor input current and trigger the control triode to perform power-off protection when overcurrent is detected;

[0018] The anti-island driving circuit drives the motor to disconnect the photovoltaic grid connection when the main power supply fails, thereby realizing the anti-island protection function of the distributed photovoltaic grid-connected system.

[0019] As a preferred technical scheme, the DC-DC power supply circuit comprises a voltage booster connected to the power supply input end of the motor driving chip and the input end of the super capacitor charging control circuit, and the voltage booster has overvoltage protection and undervoltage protection functions.

[0020] As a preferred technical scheme, the super capacitor charging control circuit comprises two serially connected NPN triodes and two anti-parallel diodes, one of which is used for preventing reverse current when the super capacitor discharges, and the other is used for preventing voltage backflow of the DC-DC power supply end.

[0021] As a preferred technical scheme, the super capacitor boosting discharging circuit comprises a boosting chip, an input end of which is connected to the positive pole of the super capacitor, and an output end of which is connected to the power input end of the motor driving chip through a current limiting resistor, so as to prevent the impact of instantaneous large current on the system.

[0022] As a preferred technical scheme, the motor driving circuit is provided with a power MOSFET driving module, a gate of the power MOSFET receiving a logic level signal from a control signal end, so as to control the forward rotation and reverse rotation and start and stop of the motor.

[0023] As a preferred technical scheme, the motor charging linkage circuit comprises an AND gate logic chip, input ends of which are connected to the motor forward rotation signal and reverse rotation signal, and an output end of which is connected to the start and stop control end of the super capacitor charging control circuit.

[0024] As a preferred technical scheme, the motor current limiting protection circuit is provided with a current sensing amplifier, an input end of which is connected to a sampling resistor of the motor power supply end, and a voltage difference signal between two ends of which is amplified to control the switching state of a triode.

[0025] As a preferred technical scheme, the motor driving chip driving output end is provided with a reverse diode, which is used for absorbing instantaneous current caused by reverse electromotive force of the motor.

[0026] As a preferred technical scheme, the super capacitor charging control circuit comprises a current limiting resistor, which is connected between the super capacitor and the DC-DC power supply, so as to limit the charging current of the super capacitor and avoid damage to the charging circuit caused by overcurrent.

[0027] As a preferred technical scheme, the motor current limiting protection circuit further comprises a triode with a base resistor, a base of which is connected to the output end of the current sensing amplifier, and when over-limit current is detected, the triode is turned on to forcibly cut off the motor driving signal.

[0028] The present application has the following advantages: 1. The present application adopts an independent motor backup power supply design based on a super capacitor, avoids the risk of mixing with the system main power supply, ensures that the motor can still be provided with reliable driving power when the main power supply is powered off, and thus greatly improves the reliability and power-off protection capability of the system.

[0029] Secondly, the intelligent power scheduling management function is integrated, the super capacitor charging is automatically stopped when the motor starts, the power resource competition is avoided, the system peak power consumption is reduced, thereby effectively reducing the equipment capacity demand and reducing the overall system cost, in addition, in view of the problem that the traditional motor driving circuit lacks flexible current limiting protection, the motor accurate current limiting protection is realized through the combination design of the current sensing amplifier and the transistor, the power supply can be automatically cut off when the motor is blocked or the current is overloaded, mechanical damage of key components such as gears is prevented, and the durability and stability of the equipment are enhanced;

[0030] Thirdly, at the same time, the super capacitor boost discharge circuit can be started immediately when the main power is disconnected, so that the motor can complete the breaking operation in a short time, and the emergency response speed and execution success rate of the system are improved, the structure of the application is modularized, the functions are independent, the adaptability is strong, and the application can be widely applied to distributed photovoltaic grid-connected circuit breaker equipment of different specifications, in addition, the system design also contains multiple safety measures such as overvoltage protection, undervoltage protection and reverse voltage protection, and the stability and electrical safety of the system operation are further enhanced;

[0031] Through reasonable circuit design and control algorithm, the application improves the photovoltaic grid-connected safety and system reliability, effectively controls the hardware cost, and has good economic benefit and social value. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0033] Figure 1 The system block diagram of the application;

[0034] Figure 2 The circuit principle diagram of the DCDC power supply circuit part of the application;

[0035] Figure 3 The super capacitor charging control circuit principle diagram of the application;

[0036] Figure 4 The super capacitor boost discharge circuit principle diagram of the application;

[0037] Figure 5 The circuit principle diagram of the motor driving circuit of the application;

[0038] Figure 6 The circuit principle diagram of the motor charging linkage circuit of the application;

[0039] Figure 7 The circuit principle diagram of the motor current limiting protection circuit of the application. DETAILED DESCRIPTION

[0040] All features disclosed in this specification, and / or all steps of any methods or processes disclosed, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive.

[0041] Any feature in the present specification, including any accompanying claims, abstract and drawings can be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. That is, unless expressly stated otherwise, every feature is one of a range of equivalent or similar features.

[0042] As Figures 1-7 shown, the anti-island driving circuit suitable for distributed photovoltaic grid-connected circuit of the application comprises:

[0043] A 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, which is provided to the motor drive chip as the driving power supply on the one hand, and is transmitted to the super capacitor charging control circuit for backup power charging on the other hand;

[0044] The super capacitor charging control circuit is connected to the DC-DC power supply circuit and has a current-limiting charging function, which stops charging when the motor starts. Its feature is to use double NPN transistors to realize charging control and prevent reverse voltage breakdown through diodes;

[0045] The super capacitor boost discharge circuit is used to boost the energy stored in the super capacitor to the motor driving voltage, and is controlled by the motor charging linkage circuit to perform dynamic discharge when the motor starts;

[0046] The motor drive circuit receives the forward and reverse drive signals, monitors the motor input current through the sampling resistor connected in series to the power supply input, and is connected to the motor current limiting protection circuit to realize motor overcurrent protection;

[0047] The motor charging linkage circuit includes an AND logic circuit for logical operation of the motor forward and reverse control signals, and outputs a charging control signal to control the super capacitor charging process;

[0048] The motor current limiting protection circuit includes a current sensing amplifier and a control transistor, which is used to monitor the motor input current and trigger the control transistor for power-off protection when overcurrent is detected;

[0049] The anti-island driving circuit drives the motor to disconnect the photovoltaic grid connection when the main power fails, thereby realizing the anti-island protection function of the distributed photovoltaic grid-connected system.

[0050] The specific principles of each functional module are described in detail below:

[0051] As Figure 2 shown, first, the DC-DC power supply circuit is the core power management module of the driving circuit, and its main function is to convert the 12V input voltage from the switching power supply into the target operating voltage of the motor, such as 6V.

[0052] The DC-DC power supply circuit adopts a step-down converter structure, mainly composed of a boost chip (such as ETA2845), a power inductor (such as 2.2uH), and an output filter capacitor (such as 10uF).

[0053] The input end is connected to the main power supply of the system, and after pulse modulation by the inductor and the step-down chip, a stable motor operating voltage is generated at the output end.

[0054] In order to improve the stability of the system, the DC-DC power supply circuit integrates overvoltage protection and undervoltage protection functions to prevent damage to the motor drive chip caused by abnormal input voltage. The voltage output of this module not only powers the motor drive chip, but also provides power input for the supercapacitor charging control circuit, ensuring continuous charging of the supercapacitor.

[0055] As Figure 3 shown, the supercapacitor charging control circuit uses two series-connected NPN transistors (such as Q1 and Q2) and two anti-parallel diodes (such as D1 and D2) to form a current-limiting charging loop. The power input end is connected to the positive pole of the supercapacitor through a current-limiting resistor (such as R9), which is used to control the charging current and prevent transient overcurrent from damaging the charging loop;

[0056] Diode D1 is used to prevent the supercapacitor from reverse discharging to the DC-DC power supply circuit when power is off, and D2 is used to prevent the voltage backflow from 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 the conduction of transistor Q1, immediately cutting off the charging loop of the supercapacitor, avoiding power competition between the supercapacitor and the motor, and ensuring that the motor runs preferentially.

[0057] When the main power supply is powered off, as Figure 4 shown, the supercapacitor boost discharge circuit is automatically activated to provide sufficient operating voltage for the motor. The core component of this circuit is a boost chip (such as ETA1061), whose input end is connected to the positive pole of the supercapacitor, and the output end is connected to the power input end of the motor drive chip through diode D2;

[0058] The boost chip has a built-in boost control circuit. The power MOSFET inside the chip boosts the energy in the super capacitor according to the high-frequency switching principle, ensuring 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, ensuring stable power supply voltage during motor operation.

[0059] As shown in Figure 5 , the motor drive circuit is the execution module of the entire anti-islanding drive circuit. The motor drive chip (such as DRV8870) has a dual-output terminal, which is used for forward and reverse control of the motor respectively. The control signal terminal (such as CTL_MOTOR_F and CTL_MOTOR_B) is connected to the direction control pin of the drive chip. When receiving a high-level control signal, the H-bridge circuit inside the drive chip is turned on, allowing the motor to run in the specified direction;

[0060] The switching network composed of power MOSFET controls the running state of the motor when receiving a logic level signal. To protect the normal operation of the motor and the drive chip, this module is equipped with a reverse diode D3 to absorb the reverse electromotive force generated when the motor stops, avoiding damage to the drive chip caused by transient current impact.

[0061] As shown in Figure 6 , the motor charging linkage circuit uses an AND gate logic chip (such as 74LV32) to control the charging process of the super capacitor;

[0062] When the forward and reverse signals of the motor are both low, the AND gate chip outputs a low-level signal, activating the super capacitor charging control circuit and starting to charge the super capacitor. If any input signal is high, it indicates that the motor is running, and the AND gate chip outputs a high-level signal, stopping the super capacitor charging process. This design ensures that the charging of the super capacitor is staggered with the operation of the motor, avoiding power conflicts and energy waste.

[0063] As shown in Figure 7 , in order to protect the motor from damage caused by stalling and overcurrent, the motor current limiting protection circuit uses a current sensing amplifier (such as INA180) combined with a control transistor Q3. The current sampling resistor R11 is connected in series at the motor power input, which monitors the working current of the motor in real time. The current sensing amplifier amplifies the voltage difference across the sampling resistor and outputs it to the base of transistor Q3;

[0064] When the current exceeds the set safety threshold, Q3 is turned on, cutting off the motor drive signal and forcing the motor to stop running, thereby avoiding damage to mechanical structures such as gears and enhancing the stability and safety of the system.

[0065] The application realizes the quick power-off operation when the main power is off, guarantees the stable and safe operation of the photovoltaic grid-connected system through the accurate power management, the intelligent power scheduling and the reliable motor protection mechanism.

[0066] The above merely describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any change or replacement without creative labor should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be limited by 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 converts the 12V input voltage from the switching power supply into the motor's target operating voltage. This target operating voltage is supplied to the motor driver chip in the motor drive circuit as a driving power source and is also transmitted to the supercapacitor charging control circuit for backup power charging. 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 the motor drive voltage and dynamically discharge it under the control of the motor charging linkage circuit when the motor starts; The motor drive circuit includes a motor drive chip, which receives 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 implement motor overcurrent protection; The motor charging linkage circuit includes an OR gate logic circuit for performing a logical operation on the motor control signal and outputting 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 cut off the power supply for protection. The anti-islanding drive 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; The DC-DC power supply circuit includes a boost converter, the output of which is connected to the power input of the motor drive chip in the motor drive circuit and the input of the supercapacitor charging control circuit. The boost converter has overvoltage protection and undervoltage protection functions. The supercapacitor charging control circuit includes two NPN transistors connected in series and two anti-parallel diodes, one of which is used to prevent reverse current during supercapacitor discharge, and the other is used to prevent voltage backflow at the DC-DC power supply end; 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 in the motor drive circuit through a current limiting resistor to prevent instantaneous large current from impacting the system; the motor drive circuit is equipped with a power MOSFET driver module, and the gate of the power MOSFET receives a logic level signal from the control signal end to control the forward and reverse rotation and start and stop of the motor; the motor charging linkage circuit includes an OR gate logic chip, whose input end is connected to the motor forward rotation signal and reverse rotation signal, and whose output end is connected to the start and stop control end of the supercapacitor charging control circuit; 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 across the sampling resistor is amplified to control the switching state of the transistor.

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

3. The anti-islanding drive circuit for distributed photovoltaic grid-connected circuit breaker according to claim 1, characterized in that: The supercapacitor charging control circuit includes a current limiting resistor connected between the supercapacitor and the DC-DC power supply to limit the charging current of the supercapacitor and prevent damage to the charging circuit due to overcurrent.

4. The anti-islanding drive circuit for distributed photovoltaic grid-connected circuit breaker 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.

Images