WO2022166928A1

WO2022166928A1 - Rapid shutdown system for photovoltaic grid-connected power generation

Info

Publication number: WO2022166928A1
Application number: PCT/CN2022/075202
Authority: WO
Inventors: 宋悦; 陈泽熙
Original assignee: 深圳市中旭新能源有限公司
Priority date: 2021-02-04
Filing date: 2022-01-30
Publication date: 2022-08-11
Also published as: CN215498289U

Abstract

Disclosed are a rapid shutdown system for photovoltaic grid-connected power generation, which system relates to the technical field of photovoltaic grid-connected power generation. The utility model mainly comprises a short circuit shutdown circuit configured on an output side of a photovoltaic assembly, and a direct-current bypass circuit configured on an output side of a photovoltaic string. By means of the short circuit shutdown circuit that mainly comprises a first switch member, a second switch member, an energy storage element, a first control module and a first auxiliary power source, when there is a short circuit, the connection between the photovoltaic assembly and the photovoltaic string is automatically disconnected, and after the connection is disconnected, re-connection can be performed only when short circuit detection is passed; and by means of the direct-current bypass circuit that comprises a third switch member and a resistor element, the short circuit shutdown circuit of each assembly is short-circuited or bucked, so as to realize rapid shutdown. The utility model can meet the safety regulation requirements of a photovoltaic system for rapid shutdown, and is low in cost and has a good reliability and safety.

Description

A fast shutdown system for photovoltaic grid-connected power generation

technical field

The utility model relates to the technical field of photovoltaic grid-connected power generation, in particular to a fast shutdown system for photovoltaic grid-connected power generation.

Background technique

In recent years, photovoltaic power generation has achieved unprecedented rapid development all over the world, including China, and has been widely installed on the roofs of residential, industrial and commercial buildings. When the PV modules are exposed to light, there is a DC high voltage in the string. When a fire occurs in a building, firefighters cannot spray water to put out the fire. They can only wait for all the modules to burn out before disaster relief, causing property damage or threatening personal safety.

Based on safety considerations, Italian safety cautions that firefighters are absolutely not allowed to carry out fire extinguishing operations when the building is under voltage; Germany is also the first to implement fire safety standards and also expressly stipulates that in the photovoltaic power generation system, the inverter and the components are connected. In addition, the German insurance company also has clear regulations that no compensation will be paid for the personal injury caused by the photovoltaic power station during the fire extinguishing process; the American Fire Protection Association has revised the National Electrical Code, requiring residential use In the photovoltaic power generation system of 10000000000000000: In the event of an emergency, the maximum voltage of the DC terminal shall not exceed 80V after the AC grid-connected port of the photovoltaic power generation system is disconnected.

The laws and regulations of supporting safe electricity use in European and American countries have been extended to the field of photovoltaic power generation. Taking the National Electrical Code (NEC) NEC2017--690.12(B) as an example, it requires photovoltaics installed on the roof or on the building. The system must have a fast shut-off function; the speed of shut-off and the voltages in the photovoltaic array, between the external conductors and between the conductors and the ground are required after shut-off, and the specific requirements are within 30 seconds after the quick-shut-off device is activated. , PV array within 1 meter range: voltage ≤ 30V, PV array within 1 foot (30.5 cm) range: voltage ≤ 80V.

In order to meet the requirements of the above NEC2017--690.12(B), the photovoltaic system needs to have a fast shutdown function at the module level. In the prior art, in order to realize the fast shutdown function at the component level, the shutdown controller needs to continuously send a heartbeat communication signal, or the shutdown control module located on the DC bus needs to send a periodic excitation pulse source; these two schemes In the PV inverter system, not only the corresponding sending module needs to be added, but also the additional receiving module needs to be set in the PV module switch-off or power optimizer, because the above fast turn-off device relies on the power carrier communication (PLC) , Subject to the attenuation of the signal transmission of the power carrier communication, the number and length of the PV module strings each set of quick shutdown devices act on is limited, which not only increases the cost of the PV system and the self-consumption of the system, but also increases more The fault point of the signal source sending and receiving module.

Due to the existence of the above problems, it is inevitable to face problems such as high cost and reliability when achieving photovoltaic module level shutdown. At the same time, the simple shutdown function will generate the self-consumption of the circuit breaker, so it is currently difficult to commercialize in China. The application of photovoltaic power generation in China has led to the hidden danger of production safety in my country's photovoltaic power generation industry.

Utility model content

In order to solve the defects existing in the prior art, the main purpose of the present invention is to provide a fast shutdown system for photovoltaic grid-connected power generation. On the one hand, the utility model realizes the reduction of the heartbeat or periodic excitation pulse signal source receiving module in the photovoltaic switch and the power optimizer, and the signal source sending module in the photovoltaic inverter system. The module-level shutdown of the photovoltaic system reduces the voltage inside and outside the photovoltaic array to a safe range in a very short period of time. On the other hand, the utility model can be used with simple steps and reliable implementation. After the fault is removed, photovoltaic power generation can be restored conveniently and expressly, and when applied to a photovoltaic power optimizer, it can also provide shielding and power generation loss recovery for photovoltaic systems. And to prevent module hot spots and DC arc fault points, it solves the problem that the current photovoltaic module-level shutdown is difficult to commercialize on a large scale.

In order to achieve the above object, the utility model adopts the following technical scheme:

The utility model provides a fast shutdown system for photovoltaic grid-connected power generation, which is arranged in the photovoltaic grid-connected power generation system and includes a photovoltaic series body connected in series by a plurality of photovoltaic units. The rapid shutdown system includes a photovoltaic unit output side. The short-circuit shut-off circuit, and the DC bypass circuit arranged on the output side of the photovoltaic series body, the output ends of many of the short-circuit shut-off circuits are connected in series as the output end of the photovoltaic series body;

The short-circuit shut-off circuit includes a first switch element, a second switch element, an energy storage element, a first control module and a first auxiliary power supply; the first switch element and the second switch element are connected to the photovoltaic unit and the photovoltaic series body On the connection loop of the , if any one of the first switch element and the second switch element is turned off, the connection between the photovoltaic unit and the photovoltaic series body is disconnected; the energy storage element is connected to the first switch element and the second switch element In between, the conduction of the first switch element can connect the photovoltaic unit and the energy storage element, and the conduction of the second switch element can connect the energy storage element and the photovoltaic series body; the first auxiliary power source is electrically connected to the output of the photovoltaic unit. The first control module is connected to the first switching element and the second switching element by switching signal control, and the first control module can perform short-circuit detection; the DC bypass circuit includes The third switching element and the resistive element connected in series are connected in parallel on the output side of the photovoltaic series body; the DC bypass circuit further comprises a second control module (H), the second control module (H) is controlled to be connected to The third switch element.

The working principle of the technical solution is as follows: after the third switching element is turned on, each first auxiliary power supply is turned off at least because the voltage is lower than the operating requirement, so that any one of the first switching element and the second switching element is turned off, and disconnecting the connection between the photovoltaic unit and the photovoltaic series body; at least when the first auxiliary power supply is restarted due to the DC bypass circuit, the first control module separately controls the conduction of the first switching element and the second switching element respectively , so that the energy storage element is connected to the photovoltaic series body after taking power from the photovoltaic unit, and it is obtained and judged according to the change of the electrical parameters of the energy storage element whether the short-circuit condition is met. Disconnection of the tandem.

In the above fast shutdown system, optionally, the third switch element is a normally closed switch element, and the DC bypass circuit further includes a second control module and a second auxiliary power supply, and the second auxiliary power supply takes power Connected to the output side of the inverter system or the DC combiner box, the second auxiliary power supply is connected to the second control module for power supply, and the second control module is controlled to be connected to the third switch element.

In the above-mentioned quick shutdown system, optionally, the DC bypass circuit further includes a manual switch element, and the manual switch element can control the conduction of the third switch element.

The above-mentioned quick shutdown system, optionally, the short-circuit shutdown circuit is configured in a photovoltaic power optimizer, and the optimizer includes a power conversion module, a control module and an auxiliary power supply, and the first control module is used as a power source of the optimizer. a control module, the first auxiliary power supply is used as the auxiliary power supply of the optimizer, and the first switching element, the second switching element and the energy storage element are arranged on the positive and negative loops of the power conversion module; when the optimizer is running normally , the first control module sets the electrical parameters at the output of the photovoltaic unit at the maximum power point, and when the optimizer starts, the first control module controls the first switching element, the second switching element and the energy storage element to perform short circuit detection.

In the above-mentioned fast shutdown system, optionally, the power conversion module is a Buck-type or Boost-type or Boost-Buck-type DC chopper circuit with an output capacitor; the output capacitor is used as an energy storage element of the short-circuit shutdown circuit;

During the short-circuit test, the first control module obtains electricity by separately collecting and recording the output capacitor conducting to the photovoltaic unit, and the output capacitor conducting the voltage parameter of the power acquisition system, so as to obtain the voltage parameters used to determine whether the short-circuit condition is satisfied. Conditional voltage parameter differences.

Above-mentioned fast shut-off system, optional, described power conversion module is Buck type or Boost type or Boost-Buck type DC chopper circuit with input capacitance and output capacitance;

During the short-circuit test, the first control module obtains the difference in voltage parameters for judging whether the short-circuit condition is met by collecting the difference in voltage parameters between the input capacitor and the output capacitor when the output capacitor is turned on to the power acquisition system. .

In the above fast shutdown system, optional, the first switching element is used as a switching element connected in series on the positive or negative loop in the DC chopper circuit, and the second switching element is connected in series with the output of the DC chopper circuit The switch elements on the positive or negative loop between the terminal and the output terminal of the optimizer, at least one of the first switch element and the second switch element is a normally open switch element.

In the above fast shutdown system, optionally, the power conversion module is a step-down Buck DC chopper circuit, which includes an input capacitor, a switching element serving as the first switching element, an inductor, and an energy storage device. The output capacitor of the component; the first switching element, the inductor and the second switching element are sequentially connected in series to the positive circuit of the DC chopper circuit, and the positive and negative circuits of the input capacitor are connected in parallel to the input end of the power conversion module and the first switch between components, the positive and negative electrodes of the output capacitor are connected in parallel between the inductor and the second switching component.

In the above-mentioned fast shutdown system, optionally, the energy storage element is a capacitive element connected in parallel with the positive and negative connection loops of the photovoltaic single and the photovoltaic series body, and the first control module obtains and obtains and according to the voltage parameter of the capacitive element It is judged whether the short-circuit condition is satisfied by the difference before and after taking electricity from the photovoltaic unit and connecting to the photovoltaic series body.

In the above-mentioned rapid shutdown system, optionally, the first control module includes a control unit for controlling the operation of the short-circuit shutdown circuit, a collection unit, an arithmetic unit, a judgment unit, a count unit, and a drive unit;

The control unit is used for controlling the second switching element to be kept off, and then controlling the first switching element to be turned on, so that the energy storage element obtains power from the photovoltaic unit, and controlling the first switching element to be turned off, and then controlling the second switching element Conduction, so that the energy storage element is connected to the power acquisition system;

The collection unit is used to collect the electric parameter information of the energy storage element in the acquisition of electric power and included in the electric power acquisition system;

The computing unit is used to obtain the difference of the electrical parameter information in the power state and the access system state;

The judging unit is used for judging the electrical parameter information parameters, and driving the control unit to perform corresponding operations;

When it is determined that there is no short circuit, the control unit controls the first switching element and the second switching element to be turned on at the same time with the switching value; when it is determined that the short circuit is determined, the first switching element and the second switching element are controlled with the switching value. If it is judged as not confirming the short circuit, the control unit will perform short circuit detection again after delaying the set time;

The counting unit measures the number of executions of the first control unit performed because the short-circuit is not confirmed, and determines that the short-circuit is confirmed when the preset number of times is exceeded;

The driving unit controls the turn-off and turn-on of the first switching element and the second switch with driving power according to the switching quantity control command.

Compared with the prior art, the beneficial effects of the present utility model are as follows:

(1) The utility model short-circuits the photovoltaic series body or connects the resistance in parallel through the DC bypass circuit to reduce the voltage, so that the auxiliary power supply in the photovoltaic module equipped with the short-circuit cut-off circuit is stopped at least because the voltage is lower than the cut-off voltage, and the short-circuit is at the same time. The switch element of the shut-off circuit automatically disconnects the photovoltaic modules and the photovoltaic series connection to achieve rapid shutdown; at the same time, after the auxiliary power is restarted after the disconnection, the control module of the short-circuit shutdown circuit will first maintain the photovoltaic modules and photovoltaics. The connection of the series body is disconnected, and the short-circuit detection is carried out by using the principle that the energy storage element will produce electrical parameter changes in the presence of a short circuit; during the detection process, the photovoltaic modules and the power acquisition circuit are kept disconnected to ensure that the photovoltaic modules are not correct before the short-circuit is removed. External output power; when the circuit is turned off due to short-circuit caused by other reasons, it will automatically restart after short-circuit detection to realize the intelligence of the photovoltaic grid-connected system; the process of rapid shutdown does not need to be set in the circuit breaker or optimizer for The heartbeat or periodic excitation pulse signal of the communication reduces the setting of the receiving module and the sending module, reduces the cost, and can realize the rapid shutdown of the photovoltaic power generation system to the photovoltaic modules with high reliability, and the photovoltaic power generation system can be quickly turned off in a very short time. The voltage inside and outside the array is reduced to a safe range, meeting the safety regulations of NEC2017-690.12(B); only a small amount of power from the energy storage element is used for testing, the measurement process is safe and reliable, and will not cause a burden to the system.

(2) The third switch element of the present invention is a normally closed switch element. When the inverter system is in normal operation, it is necessary to control the third switch element to be turned off to maintain the operation. , the third switch element is self-conducting due to the shutdown of the second auxiliary power supply, and then cooperates with the short-circuit shut-off circuit to quickly disconnect each photovoltaic module from the system. At the same time, the resistance element can reduce the output voltage of the photovoltaic string to a safe range At the same time, it quickly consumes the power of the inverter input capacitor and various energy storage devices in the photovoltaic string to improve the safety of the photovoltaic power generation system after shutdown.

(3) The utility model can configure the short-circuit cut-off circuit in the photovoltaic power optimizer. On the one hand, the photovoltaic power optimizer can make the photovoltaic modules operate at the maximum power point, improving the efficiency of power generation; on the other hand, the short-circuit cut-off circuit can During shutdown and startup, the control module of the optimizer is used for acquisition, calculation, judgment and control, and the switching elements and energy storage elements in the power conversion module of the optimizer can also be used. Compared with the Buck-type topology The optimizer is equivalent to adding a second switch element at the output end of the power conversion module, which makes the short-circuit cut-off circuit simple in structure, easy to implement, and greatly improves the safety and reliability of power generation on the basis of local cost. Compared with the traditional switch-off and optimizer, the dedicated receiver module and transmitter module are also reduced, which reduces the manufacturing cost of the power generation system.

The utility model will be further described below in conjunction with the accompanying drawings.

Description of drawings

1 is a schematic structural diagram of a quick shutdown system according to an embodiment of the present invention;

2 is a schematic structural diagram of a short-circuit shutdown circuit according to an embodiment of the present invention;

3 is a schematic structural diagram of a photovoltaic power optimizer configured with a short-circuit shutdown circuit according to an embodiment of the present invention;

4 is a schematic structural diagram of a short-circuit turn-off control structure of a first control module according to an embodiment of the present invention;

5 is a schematic structural diagram of a power conversion control structure of a first control module according to an embodiment of the present invention;

6 is a schematic structural diagram of a photovoltaic inverter system configured with a DC bypass circuit according to an embodiment of the present invention.

Detailed ways

In order to better illustrate the purpose, technical solutions and advantages of the present invention, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the present utility model, but are not intended to limit the scope of the present utility model.

As shown in FIG. 1 , it is a photovoltaic grid-connected power generation rapid shutdown system according to an embodiment of the present invention, which is configured in the photovoltaic grid-connected power generation system, and includes a photovoltaic series body connected in series by many photovoltaic units. In this embodiment, the photovoltaic unit is a photovoltaic module A. In other implementations, it can also be a photovoltaic string B containing a plurality of photovoltaic modules A, or a series of photovoltaic cells in a photovoltaic module A. The body corresponds to the photovoltaic string B in this embodiment. The fast shutdown system includes a short-circuit shutdown circuit E4 and a DC bypass circuit P.

Referring to Figure 1, the output side of the photovoltaic module A is connected with a short-circuit shut-off circuit E4, and the output ends of the many short-circuit shut-off circuits E4 are connected in series as the output end of the photovoltaic string B. The number of photovoltaic modules A is multiple, and the number of A-1, A-2, . E-1, E-2, . The terminal is connected to the photovoltaic inverter system J. In other embodiments, the photovoltaic string B can also be connected to the input end of the DC combiner box, and the output end of the DC combiner box is connected to the inverter system J. The DC bypass circuit P is configured on the output side of the photovoltaic string B, and is specifically configured in the inverter system J in this embodiment, and may also be configured in a DC combiner box in other embodiments. The short-circuit shut-off circuit E4 can be configured to operate at the output end of the photovoltaic module A alone or in the power optimizer E.

Specifically, in this embodiment, the short-circuit shut-off circuit E4 includes a first switching element S1, a second switching element S2, an energy storage element C, a first control module E2, and a first auxiliary power source E3. The first switching element S1 and the second switching element S2 are connected in series on the positive circuit connecting the photovoltaic module A and the photovoltaic string B, and the turning off of the first switching element S1 and the second switching element S2 can disconnect the power generation of the photovoltaic module A loop. In this embodiment, the energy storage element C is a capacitive element R that is connected in parallel on the communication loop and located between the first switching element S1 and the second switching element S2. In other embodiments, the energy storage element C may also be an inductance, and whether the external circuit is short-circuited is determined by measuring the current or energy storage condition of the inductance. When the first switching element S1 is turned on, the capacitive element R is connected with the photovoltaic assembly A; when the second switching element S2 is turned on, the capacitive element R is connected with the photovoltaic string B. The first auxiliary power source E3 is connected in parallel to the positive and negative loops of the output end of the photovoltaic module A, and the first switching element S1 and the second switching element S2 are normally open switching elements. When a short circuit occurs and the positive and negative loop voltages are lower than the voltage of the first auxiliary power source E3, the first control module E2 stops running, the first switching element S1 and the second switching element S2 are turned off, so that the photovoltaic module A is turned off. The connection circuit of the connected PV string B is disconnected. After the first switching element S1 and the second switching element S2 are turned off, the first auxiliary power source E3 will be isolated from the short-circuit condition of the external circuit, and the power drawn from the photovoltaic assembly A will be resumed. The first control module E2 separately controls the conduction of the first switching element S1 and the second switching element S2, so that the capacitor is connected to the power acquisition system after drawing electricity from the photovoltaic module A, and the acquisition is obtained and judged according to the difference of the voltage parameters between the two ends of the capacitor Whether the short-circuit condition is met, the first switching element S1 and the second switching element S2 are turned on at the same time only after it is determined that the short-circuit condition is not met, and the connection between the photovoltaic unit and the photovoltaic string B is restored. The short-circuit cut-off circuit E4 of the present invention, on the one hand, utilizes the first switching element S1 and the second switching element S2 to automatically turn off and perform short-circuit protection when a short circuit occurs in the power acquisition system; The on-off control of the device S1 and the second switching device S2 is performed, and the energy storage element C is used to test whether the external circuit is short-circuited.

Referring to FIGS. 1 and 6 , in conjunction with the short-circuit shut-off circuit E4, the DC bypass circuit P of the present invention is configured in the photovoltaic inverter system J, which includes a third switching element S3, a resistive element, a second control module H, a second Auxiliary power supply Q and manual switch K. The photovoltaic inverter system J includes a boost conversion circuit J1 and an inverter circuit J2. The conversion circuit J1 is connected to each photovoltaic string B, obtains the power at the output end of the photovoltaic string B and converts it into another electric parameter and outputs it to the inverter circuit J2. The inverter circuit J2 inverts the DC power to AC power and parallels the grid. supply. The third switching element S3 and the resistance element are connected in series with each other, and the output end thereof is connected in parallel with the input end of the conversion circuit J1. Specifically, in this embodiment, the third switching element S3 is a P-type normally-closed field effect switch tube M3, and in other embodiments, it may also be a normally-closed relay or other normally-closed fully-controlled semiconductor switching elements.

It should be noted that the resistance element is a power resistor, and its resistance value is small, so that when it is connected to the photovoltaic string B in a loop, not only the first auxiliary power supply E3 is lower than the off voltage, but also the photovoltaic group can be reduced. The output voltage of string B is reduced to within the safety requirements, and at the same time, the power of the input capacitor of the conversion circuit can be quickly consumed, and the power of each output capacitor in the photovoltaic string B can be quickly consumed to further ensure the safety of the system after shutdown.

It should be noted that the input end of the second auxiliary power supply Q is connected to the AC side of the inverter system J, the output end of the second auxiliary power supply Q is connected to the second control module H for power supply, and the second control module H is controlled to be connected to the third control module H. The switching element S3, the conversion circuit J1 and the inverter circuit J2, the second control module H is input and connected with a manual switching element K. The manual switch element K is an emergency shutdown button. When the manual switch K is actively pressed, the second control module H controls the switch in the inverter circuit J2 to turn off, so that the inverter system J stops running, and the connection between the inverter system J and the power grid is cut off, and the second The auxiliary power supply Q will be shut down, further shutting down the second control module H, and the third switching element S3 will remain on due to the loss of driving, so as to quickly shut down each photovoltaic module A in an emergency. When the inverter system J is shut down due to other reasons, the second auxiliary power source Q will be turned off due to the loss of power, and the second control module H will be turned off, and the third switching element S3 will be further turned on without driving, so as to realize the rapid operation in emergency. Turn off each PV module A.

It can be understood that, in conjunction with other factors other than the short-circuit of the non-DC bypass circuit P, the short-circuit shut-off circuit E4 disconnects the photovoltaic module A, which can be automatically activated after short-circuit detection. After the first switching element S1 and the second switching element S2 are turned off, the first auxiliary power source E3 will be isolated from the short-circuit condition of the external circuit, and the power drawn from the photovoltaic assembly A will be resumed. The first control module E2 separately controls the conduction of the first switching element S1 and the second switching element S2, so that the capacitor is connected to the power acquisition system after drawing electricity from the photovoltaic module A, and the acquisition is obtained and judged according to the difference of the voltage parameters between the two ends of the capacitor Whether the short-circuit condition is met, each short-circuit cut-off circuit E4 keeps the photovoltaic module A and the photovoltaic string B disconnected before confirming that the short-circuit condition is not met, and turns on the first switching element S1 and the second switching element S1 at the same time only after confirming that the short-circuit condition is not met. The switch S2 restores the connection between the photovoltaic unit and the power acquisition system.

As a feature of the embodiment of the present invention, the fast shutdown system including the short-circuit shutdown circuit E4 and the DC bypass circuit P can meet the requirements of safety regulations 690.12(B) in the face of emergency active shutdown and fault sudden shutdown. requirements, and can realize the automatic shutdown of the photovoltaic array, and reduce the voltage of the photovoltaic string B to the safety requirements, and in the face of the shutdown of the photovoltaic module A caused by other factors that are not short-circuit, the short-circuit shutdown circuit E4 can operate again. After short-circuit detection, automatic startup is realized, and there is no need to establish communication between PV module A and the central control. In general, a simple and low-cost circuit structure is used to realize the fast shutdown and safe self-start of PV module A by the PV grid-connected power generation system.

As shown in FIG. 2 , it is a photovoltaic power optimizer E configured with the short-circuit shut-off circuit E4 according to an embodiment of the present invention, and the optimizer E includes a power conversion module E1 , a control module and an auxiliary power supply. It can be understood that when the short-circuit shutdown circuit E4 is configured in the photovoltaic power optimizer E, the control module and the auxiliary power supply can be shared with the optimizer E to simplify the circuit structure and reduce the hardware cost. In this embodiment, in the short-circuit shutdown circuit E4, the first control module E2 is used as the control module of the optimizer E, the first auxiliary power supply E3 is used as the auxiliary power supply of the optimizer E, the first switching element S1, the second switching element S2 and the energy storage element C are arranged on the positive and negative loops of the power conversion module E1; when the optimizer E is running normally, the first control module E2 sets the electrical parameters at the output end of the photovoltaic module A at the maximum power point, and starts the optimizer E. , the first control module E2 controls the first switching element S1 , the second switching element S2 and the energy storage element C to perform short circuit detection. Wherein, the power conversion module E1 may be a Buck-type, Boost-type or Boost-Buck-type DC chopper circuit.

As shown in FIG. 3 is a specific buck step-down photovoltaic power optimizer E equipped with the short-circuit cut-off circuit E4. Based on the circuit structure of the optimizer E in FIG. 2, the structure of the DC chopper circuit has The switching element and the capacitor, the short-circuit shut-off circuit E4 and the optimizer E may also share the first switching element S1 and the capacitive element R.

The power conversion module E1 includes an input capacitor C1, a first switch M1, an inductor L, a freewheeling diode D1, an output capacitor C2, a second switch M2 and a bypass diode D2. The first switch tube M1, the inductor L and the second switch tube M2 are serially connected to the positive path PV+ of the DC chopper circuit in sequence. More specifically, the first switch M1 and the second switch M2 are n-type normally-on switch field effect transistors. In other embodiments, the first switch M1 and the second switch M2 may also be other fully controlled transistors. turning tube. The sources of the first switch M1 and the second switch M2 are connected towards the output side of PV+, the drains of the first switch M1 and the second switch M2 are connected towards the input side of PV+, and the first switch M1 and the second switch M2 are connected towards the input side of PV+. The gates of the switching transistors M2 are respectively connected to the first control module E2. The auxiliary capacitor and the input capacitor C1 are respectively connected in parallel on the positive path PV+ and the negative path PV- of the DC chopper circuit, and are located between the input end of the DC chopper circuit and the second switch tube M2. The anode of the freewheeling diode D1 is connected to the negative circuit PV-, the cathode of the freewheeling diode D1 is connected to the positive circuit PV+, and is located between the first switch tube M1 and the inductor. The output capacitor C2 is connected in parallel on PV+ and PV- of the DC chopper circuit, and is located between the inductor L and the second switch tube M2. The bypass diode D2 is connected in parallel on PV+ and PV- of the DC chopper circuit, and is located between the second switch tube M2 and the output end of the DC chopper circuit. The input capacitor C1 and the output capacitor C2 are used for filtering of the chopper circuit, the first switch M1 controls the chopper conversion of the inductor L by the photovoltaic assembly A, and the freewheeling diode D1 is used to maintain the output level.

It should be noted that the first switch tube M1 constitutes a component of the Buck-type DC chopper circuit, which can be used to control the power conversion of the DC chopper circuit with a pulse modulation signal (pulse width modulation PWM or pulse frequency modulation PFM), and at the same time as a short circuit. The first switching element S1 of the shut-off circuit E4; the output capacitor C2 is used as the energy storage element C of the short-circuit shut-off circuit E4; the second switch tube M2 is added on the output side of the DC chopper circuit as the second switch of the short-circuit shut-off circuit E4 Piece S2. Among them, the short-circuit shutdown circuit E4 and the DC chopper circuit have common components, so as to simplify the circuit of the photovoltaic power optimizer E. Wherein, when the bypass diode D2 is in the off state as the optimizer E, the current of the photovoltaic string B can be turned on through the bypass diode D2.

It should be noted that there are differences in the electrical parameters of the energy storage element C in the two control states of the switching element. On the one hand, in the two control states, the voltage parameters of the output capacitor C2 when it is connected to the photovoltaic module A are collected and recorded respectively, and compared with the voltage parameters of the output capacitor C2 when it is connected to the photovoltaic string B to obtain The voltage difference of the output capacitor C2 during the short-circuit test. On the other hand, the input end of the DC chopper circuit is provided with a filtered input capacitor C1 to prevent the fluctuating current of power conversion from affecting the photovoltaic module A in the reverse direction. When the output capacitor C2 is connected to the photovoltaic string B, the And compare the voltage parameters of the input capacitor C1 and the output capacitor C2 to obtain the voltage difference of the output capacitor C2 during the short-circuit test. In the latter scheme, the process of output storage can be reduced, and the error of before and after measurement can be reduced at the same time.

As shown in Figures 4 and 5, it is a structural diagram of the first control module E2 according to the embodiment of the present invention. The first control module E2 includes a control unit 21 , a collection unit 22 , an arithmetic unit 23 , a judgment unit 24 , a counting unit 25 , a driving unit 26 and a communication unit 27 . Among them, the acquisition unit 22 can collect the current parameter Ipv and the voltage parameter Vpv at the input end of the power conversion module, and the output capacitor C2, that is, the voltage parameter Vout at the output end of the power conversion module. It is realized by processing it into an operable electrical signal by a processor. The operation unit 23 may be arranged in the processor to perform operations on the collected electrical parameters. The judging unit 24 may be provided in the processor, and judge the short-circuit condition or the current power condition according to the operation result. The control unit 21 can be set in the processor, including performing corresponding short-circuit detection control under triggering operating conditions, such as initial startup after power is supplied, and also performing corresponding control operations according to the judged structure. The counting unit 25 can be set in the processor to measure a certain result of the judgment unit 24, or to measure a certain operation of the control unit 21, and output the result when the set counting limit is reached, or clear under the set condition . The communication unit 27 can be Zibee or WIFI or Bluetooth wireless communication, and the inverter system J or the DC combiner box is configured with a second control module H, and the second control module H is configured with a communication device matching the optimizer E. The first control module E2 can alarm the second control module H via the communication unit 27 when the short-circuit fault occurs.

4, in the control process of restarting the optimizer E after the short-circuit test, specifically, the control unit 21 is used to control the second switch tube M2 to keep off, and then control the first switch tube M1 to turn on, so that the output The capacitor C2 obtains power from the photovoltaic unit, and controls the first switch M1 to be turned off, and then controls the second switch M2 to be turned on, so that the output capacitor C2 is connected to the power acquisition system; the acquisition unit 22 is used to collect the output capacitance C2 is acquiring power and taking into account the voltage parameter information of the power acquisition system; the arithmetic unit 23 is used to acquire the voltage parameter information difference between the power state and the access system state; the judging unit 24 is used to judge the voltage parameter information parameter , and drive the control unit 21 to perform the corresponding operation; when the control unit 21 determines that there is no short circuit, the control unit 21 controls the first switch M1 and the second switch M2 to be turned on at the same time with the switching quantity; The switch quantity controls the turn-off of the first switch tube M1 and the second switch tube M2. When it is determined that the short-circuit is not confirmed, the control unit 21 performs short-circuit detection again after a delay of the set time; the counting unit 25 does not confirm the short circuit. The number of executions performed by the first control unit 21 is measured, and when the preset number of times is exceeded, it is determined that the short circuit is determined; the driving unit 26 controls the turn-off and conduction of the first switch tube M1 and the second switch with driving power according to the switch quantity control command. The communication unit 27 issues an alarm to the second control module H after it is determined that the short circuit is confirmed.

5 , in the control process of power conversion when the optimizer E is running normally, specifically, the collection unit 22 is used to collect the voltage and current parameters of the output end of the photovoltaic unit; the calculation unit 23 is used to calculate the power parameters from the voltage and current parameters. The judging unit 24 is used for judging the change characteristic of the power parameter, and drives the control unit 21 to perform the corresponding operation; the control unit 21 is used for outputting the pulse modulation signal according to the change of the power parameter; The switching element of the power conversion module E1 is controlled to operate, so as to set the electrical parameter of the output terminal of the photovoltaic unit at the maximum power point.

It is worth noting that the short-circuit shut-off circuit E4 of the present invention has a restart function after short-circuit detection, and the short-circuit shut-off circuit E4 is disconnected in the face of the DC bypass circuit P being in a conducting state. The detection step will obtain the result of shutting down the optimizer E. In this case, after the cause of the rapid shutdown is eliminated, the optimizer E is restarted after the second control module H actively sends a startup instruction. In the face of short-circuit faults such as parallel arcing factors, without manual switching element K or AC side disconnection, the optimizer E will automatically shut down and shut down for failing to pass the short-circuit test. In the face of the shutdown after dark and the next morning, the auxiliary power supply reaches the starting voltage for the first time, and the optimizer E will successfully pass the short-circuit detection and automatically turn on. When the operation of the optimizer E is interrupted due to other non-short-circuit faults such as overcurrent, the optimizer E will be able to restart operation through short-circuit detection. In general, safe self-starting is realized through the short-circuit shut-off circuit E4, and on the basis of reducing the communication hardware settings, the fast shut-off of the photovoltaic module A is realized.

The above embodiments mainly describe the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention The new model will also have various changes and improvements, which all fall within the scope of the claimed invention.

Claims

A fast shutdown system for photovoltaic grid-connected power generation, which is configured in the photovoltaic grid-connected power generation system, which includes a photovoltaic series body connected by a plurality of photovoltaic units in series, and is characterized in that the rapid shutdown system includes a short circuit configured on the output side of the photovoltaic unit. A shut-off circuit (E4), and a DC bypass circuit (P) disposed on the output side of the photovoltaic series body, the output ends of many of the short-circuit shut-off circuits (E4) are connected in series as the output ends of the photovoltaic series body;

The short-circuit shut-off circuit (E4) includes a first switch element (S1), a second switch element (S2), an energy storage element (C), a first control module (E2) and a first auxiliary power supply (E3); The first switching element (S1) and the second switching element (S2) are connected to the connection loop between the photovoltaic unit and the photovoltaic series body, and the connection between the first switching element (S1) and the second switching element (S2) is is disconnected, the connection between the photovoltaic unit and the photovoltaic series body is disconnected; the energy storage element (C) is connected between the first switching element (S1) and the second switching element (S2), and the first switching element (S1) The conduction can connect the photovoltaic unit and the energy storage element (C), and the conduction of the second switch element (S2) can connect the energy storage element (C) and the photovoltaic series body; the first auxiliary power supply (E3) is electrically connected to The output end of the photovoltaic unit is connected to the first control module (E2) for power supply, and the first control module (E2) is controlled and connected to the first switching element (S1) and the second switching element (S2) by a switch signal, and the The first control module is capable of short circuit detection;

The DC bypass circuit (P) includes a third switching element (S3) and a resistance element connected in series, which are connected in parallel at the output side of the photovoltaic series body; the DC bypass circuit (P) further includes a second control module (H), the second control module (H) is controlled and connected to the third switch element (S3).
The fast shutdown system according to claim 1, characterized in that, the third switching element (S3) is a normally closed switching element, and the DC bypass circuit (P) further comprises a second auxiliary power supply (Q) , the second auxiliary power supply (Q) is connected to the output side of the inverter system (J) or the DC combiner box, and the second auxiliary power supply (Q) is connected to the second control module (H) for power supply.
The quick shutdown system according to claim 1, characterized in that, the DC bypass circuit (P) further comprises a manual switch element (K), and the manual switch element (K) can control the third switch element (S3) ) is turned on.
The fast shutdown system according to claim 1, characterized in that, the short-circuit shutdown circuit (E4) is configured in a photovoltaic power optimizer (E), and the optimizer (E) includes a power conversion module (E1), a control module and auxiliary power supply, the first control module (E2) is used as the control module of the optimizer (E), the first auxiliary power supply (E3) is used as the auxiliary power supply of the optimizer (E), and the first auxiliary power supply (E3) is used as the auxiliary power supply of the optimizer (E). A switching element (S1), a second switching element (S2) and an energy storage element (C) are arranged on the positive and negative loops of the power conversion module (E1).
The fast shutdown system according to claim 4, wherein the power conversion module (E1) is a Buck-type or Boost-type or Boost-Buck-type DC chopper circuit with an output capacitor (C2); the output The capacitor (C2) acts as an energy storage element (C) for the short circuit shut-off circuit (E4).
The fast shutdown system according to claim 4, wherein the power conversion module (E1) is a Buck-type or Boost-type or Boost-Buck-type DC chopper having an input capacitor (C1) and an output capacitor (C2). wave circuit.
The fast shutdown system according to claim 4, characterized in that, the first switching element (S1) is used as a switching element connected in series on the positive or negative loop in the DC chopper circuit, and the second switching element (S1) S2) is a switching element connected in series between the output end of the DC chopper circuit and the output end of the optimizer (E) on the positive or negative loop, at least one of the first switching element (S1) and the second switching element ( S2) is a normally open switch element.
The fast shutdown system according to claim 4, characterized in that, the power conversion module (E1) is a step-down Buck DC chopper circuit, which comprises an input capacitor (C1) as the first switching element ( S1) switching element, inductor (L), output capacitor (C2) as said energy storage element (C); said first switching element (S1), inductor (L) and second switching element (S2) ) are sequentially connected in series to the positive circuit of the DC chopper circuit, the positive and negative circuits of the input capacitor (C1) are connected in parallel between the input end of the power conversion module (E1) and the first switching element (S1), and the output capacitor ( C2) The positive and negative electrodes are connected in parallel between the inductor (L) and the second switching element (S2).
The fast shutdown system according to claim 1, wherein the energy storage element (C) is a capacitive element (R) connected in parallel to the positive and negative connection loops of the photovoltaic single and the photovoltaic series body, and the first A control module (E2) obtains and judges whether the short-circuit condition is satisfied according to the difference of the voltage parameter of the capacitive element (R) before and after taking electricity from the photovoltaic unit and connecting to the photovoltaic series body.