Photovoltaic inverter regulation and control system

Abstract

The invention belongs to the technical field of photovoltaic power generation, and relates to a photovoltaic inverter regulation and control system. An electric parameter acquisition module is used for acquiring output electric parameters of a photovoltaic inverter in real time; the MCU is used for receiving an output electric parameter of the photovoltaic inverter and outputting a first control signal when the output electric parameter is greater than 120% of a rated grid-connected electric parameter; when the output electric parameter is smaller than 105% of the rated grid-connected electric parameter, a second control signal is output; when the output electric parameter is greater than 130% of the rated grid-connected electric parameter, outputting a third control signal; the flexible control module is used for controlling the generated power of the photovoltaic inverter to be reduced in a preset proportion based on the first control signal; controlling the generation power of the photovoltaic inverter to increase in a preset proportion based on the second control signal; and the rigid control module is used for controlling a grid-connected switch arranged between the photovoltaic inverter and the power grid to be switched off based on the third control signal, and second-level regulation and control of the photovoltaic inverter are realized by monitoring operation parameters of the photovoltaic inverter.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a photovoltaic inverter control system. Background Art

[0002] In order to achieve energy transformation, distributed photovoltaic power sources are connected to the power grid in large quantities. They use photovoltaic modules to convert solar energy into DC power, and then use photovoltaic inverters to convert the DC power generated by photovoltaic modules into AC power of the mains frequency and input it into the power grid. Since the output voltage and output current of photovoltaic modules will change with the change of light intensity, when the light is strong, the voltage, current and output power of photovoltaic modules will increase, and when the light is weak, the voltage, current and output power of photovoltaic modules will decrease. Therefore, the output voltage and output power of photovoltaic inverters will also increase or decrease accordingly.

[0003] When the output voltage of the photovoltaic inverter is too large, the photovoltaic inverter should be stopped from being connected to the grid. If it is not controlled, it will not only cause damage to the photovoltaic inverter, but may even cause electric shock hazards and safety accidents. When the output voltage of the photovoltaic inverter is too small, the photovoltaic system cannot fully utilize the electricity generated by the photovoltaic components, the power generation efficiency is reduced, and it cannot meet the needs of the power grid, increasing the burden on the power grid and reducing the power supply capacity of the power grid. Therefore, it is necessary to monitor the output voltage of the photovoltaic inverter and adjust its operating parameters so that its output voltage meets the needs of the power grid, thereby ensuring power safety and the power generation efficiency of the power grid.

[0004] Some PV inverter manufacturers can obtain operating parameters such as the output voltage of the PV inverter through a 4G communication stick, but the manufacturers can usually only obtain the operating parameters and cannot adjust the operating parameters of the PV inverter. At present, the control of PV inverters is based on the master station dispatching system in the power grid. A master station dispatching system usually corresponds to multiple substations. Each substation acquisition terminal reads the user meter and sends the collected data to the master station dispatching system for judgment. The master station dispatching system sends control instructions to each substation terminal based on the judgment result. The substation terminal sends the control instructions to the inverter controller through the substation communication. The inverter controller adjusts the power generation of the PV inverter through buses such as 485 / 232. Although this control method can realize the control of the PV inverter, the substation terminal reads the meter and sends it to the master station dispatching system, and then the substation terminal transmits the instructions issued by the master station dispatching system to the inverter controller. When the PV inverter When the output voltage of the inverter is too large, the signal transmission link in the entire regulation process is long, and the power generation power of the photovoltaic inverter cannot be quickly regulated, resulting in a reverse overload in the substation or the reverse voltage of the photovoltaic grid-connected user exceeding the upper limit, thereby making the grid voltage unstable or damaging the photovoltaic inverter; in addition, in order to ensure the independence and safety isolation of the grid-connected switch set between the grid and the photovoltaic inverter, the master station dispatching system is often unable to directly connect to the interface of the grid-connected switch, nor can it directly control the state of the grid-connected switch. Therefore, even when the output voltage of the photovoltaic inverter is too high, the existing photovoltaic inverter regulation method can only control its power generation power to decrease through the master station dispatching system, and cannot directly prohibit the photovoltaic inverter from being connected to the grid.

[0005] In summary, the existing photovoltaic inverter control method has the problem that the signal transmission link is long and the photovoltaic inverter cannot be controlled in real time. Even when the output voltage of the photovoltaic inverter is too high, it can only control the power generation power of the photovoltaic inverter and cannot directly prohibit the photovoltaic inverter from being connected to the grid. Summary of the invention

[0006] To this end, the technical problem to be solved by the present invention is to overcome the problem that the signal transmission link of the photovoltaic inverter control method in the prior art is long, the photovoltaic inverter cannot be controlled in real time, and even when the output voltage of the photovoltaic inverter is too high, only the power generation power of the photovoltaic inverter can be controlled, and the photovoltaic inverter cannot be directly prohibited from being connected to the grid.

[0007] In order to solve the above technical problems, the present invention provides a photovoltaic inverter control system, which is arranged in a waterproof housing and includes:

[0008] An electrical parameter acquisition module, whose input end is connected to the photovoltaic inverter, is used to collect the output electrical parameters of the photovoltaic inverter in real time;

[0009] MCU, connected to the output end of the electrical parameter acquisition module, for receiving the output electrical parameter of the photovoltaic inverter, and when the output electrical parameter is greater than 120% of the rated grid-connected electrical parameter, outputting a first control signal to the flexible control module; when the output electrical parameter is less than 105% of the rated grid-connected electrical parameter, outputting a second control signal to the flexible control module; when the output electrical parameter is greater than 130% of the rated grid-connected electrical parameter, outputting a third control signal to the rigid control module;

[0010] a flexible control module, connected to the MCU and the photovoltaic inverter, configured to receive a first control signal and a second control signal sent by the MCU, and control the power generation of the photovoltaic inverter to decrease at a preset ratio based on the first control signal, and control the power generation of the photovoltaic inverter to increase at a preset ratio based on the second control signal;

[0011] A rigid control module is connected to the MCU and the grid-connected switch, and is used to receive a third control signal sent by the MCU, and control the grid-connected switch to disconnect based on the third control signal; wherein the grid-connected switch is arranged between the photovoltaic inverter and the power grid.

[0012] Preferably, after the rigid control module controls the grid-connected switch to be disconnected based on the third control signal, the rigid control module further comprises:

[0013] When the output electrical parameter of the photovoltaic inverter is less than or equal to 130% of the rated grid-connected electrical parameter or the disconnection time of the grid-connected switch is equal to the preset time, the MCU outputs a fourth control signal to the rigidity control module so that the rigidity control module controls the grid-connected switch to close based on the fourth control signal.

[0014] Preferably, the rigidity control module comprises:

[0015] A motor drive chip, wherein the first input end thereof serves as the first input end of the rigid control module, the second input end thereof serves as the second input end of the rigid control module, the first output end thereof serves as the first output end of the rigid control module, and the second output end thereof serves as the second output end of the rigid control module; the first input end of the rigid control module is connected to the first I / O port of the MCU, the second input end of the rigid control module is connected to the second I / O port of the MCU, and the first output end and the second output end of the rigid control module are both connected to the grid-connected switch; when the MCU outputs a third control signal in which the first I / O port is high and the second I / O port is low, outputting a forward current to control the grid-connected switch to be disconnected; when the MCU outputs a fourth control signal in which the first I / O port is low and the second I / O port is high, outputting a reverse current to control the grid-connected switch to be closed;

[0016] A resistor parallel circuit, whose input end is connected to the current detection input end of the motor drive chip and whose output end is grounded;

[0017] The capacitor parallel circuit has an input end connected to the power supply voltage input end of the motor drive chip and an output end connected to the ground.

[0018] Preferably, the flexible control module includes:

[0019] An RS485 chip, whose receiver output end is connected to the third I / O port of the MCU, whose receiver output enable end and driver output enable end are connected to the fourth I / O port of the MCU, and whose driver input end is connected to the fifth I / O port of the MCU; when the driver output enable end is at a high level, the first control signal or the second control signal sent by the MCU is received through the driver input end; when the receiver output enable end is at a low level, the first control signal or the second control signal is sent to the first output end and the second output end of the RS485 chip through the receiver output end;

[0020] A first transient voltage suppression diode, whose anode is connected to the first output terminal of the RS485 chip as the first output terminal of the flexible control module, the first output terminal of the flexible control module is connected to the input terminal of the photovoltaic inverter, and whose cathode is grounded;

[0021] A second transient voltage suppression diode, an anode of which is connected to the second output terminal of the RS485 chip, and a cathode of which is grounded;

[0022] a solid-state discharge tube, one end of which is connected to the anode of the first transient voltage suppression diode, and the other end of which is connected to the anode of the second transient voltage suppression diode;

[0023] A thermistor, one end of which is connected to the second output end of the RS485 chip, and the other end of which serves as the second output end of the flexible control module, and the second output end of the flexible control module is connected to the input end of the photovoltaic inverter.

[0024] Preferably, the flexible control module further includes:

[0025] A first resistor, one end of which is connected to the first output terminal of the RS485 chip, and the other end of which is grounded;

[0026] A second resistor, one end of which is connected to the second output end of the RS485 chip, and the other end of which is grounded;

[0027] A third resistor has one end connected to the first output end of the RS485 chip, and the other end connected to the anode of the first transient voltage suppression diode.

[0028] Preferably, the electrical parameter acquisition module includes a voltage acquisition submodule and a current acquisition submodule.

[0029] Preferably, the voltage acquisition submodule includes:

[0030] A voltage divider circuit, an input end of which is connected to an output end of the photovoltaic inverter;

[0031] A first sampling circuit, whose input end is connected to the output end of the voltage divider circuit and whose output end is grounded;

[0032] The first filter circuit has an input end connected to the output end of the voltage divider circuit, and an output end connected to the MCU.

[0033] Preferably, the current acquisition submodule includes:

[0034] A three-phase current transformer, whose input end is connected to the output end of the photovoltaic inverter;

[0035] A second sampling circuit, whose input end is connected to the positive output end of the three-phase current transformer and whose output end is grounded;

[0036] A second filter circuit, whose input end is connected to the positive output end of the three-phase current transformer, and whose output end is connected to the MCU;

[0037] A third sampling circuit, whose input end is connected to the negative output end of the three-phase current transformer and whose output end is grounded;

[0038] The third filtering circuit has an input end connected to the negative output end of the three-phase current transformer and an output end connected to the MCU.

[0039] Preferably, the model of the MCU is HC32F4A0 / DHC32FS6.

[0040] Preferably, the waterproof grade of the waterproof housing is IP65.

[0041] The photovoltaic inverter control system provided in the present application is arranged in a waterproof housing, and the output electrical parameters of the photovoltaic inverter are collected in real time through the electrical parameter collection module. When the output electrical parameters are greater than 120% of the rated grid-connected electrical parameters, it indicates that the current power generation power of the photovoltaic inverter is relatively high, and the MCU sends a first control signal to the flexible control module, and controls the power generation power of the photovoltaic inverter to be reduced according to a preset ratio through the flexible control module; when the output electrical parameters are less than 105% of the rated grid-connected electrical parameters, it indicates that the current power generation power of the photovoltaic inverter is low, and the MCU sends a second control signal to the flexible control module to control the power generation power of the photovoltaic inverter to increase according to a preset ratio to improve the power generation efficiency; when the output electrical parameters are greater than 130% of the rated grid-connected electrical parameters, it indicates that the current power generation power of the photovoltaic inverter is too high, and the MCU sends a third control signal to the rigid control module, and directly controls the grid-connected switch to be disconnected through the rigid control module, prohibiting the photovoltaic inverter from being connected to the grid, thereby protecting the safe and stable operation of the power grid. This application designs an integrated control system for each photovoltaic inverter, which can monitor the operating parameters of the photovoltaic inverter in real time and control the photovoltaic inverter in seconds. It can also directly change the state of the grid-connected switch through a rigid control module, thereby prohibiting the photovoltaic inverter from being connected to the grid when the output voltage of the photovoltaic inverter is too high, while ensuring the power generation efficiency of the photovoltaic inverter and the operating safety of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0043] Figure 1 A schematic diagram of the photovoltaic inverter control system structure provided for this application;

[0044] Figure 2 The schematic diagram of the three-phase voltage acquisition circuit provided in this application; wherein, Figure 2 (a) is the schematic diagram of the A phase voltage acquisition circuit principle. Figure 2 (b) is the schematic diagram of the B-phase voltage acquisition circuit principle. Figure 2 (c) is a schematic diagram of the C-phase voltage acquisition circuit principle;

[0045] Figure 3 The schematic diagram of the three-phase current acquisition circuit provided in this application; wherein, Figure 3 (a) is the schematic diagram of the A-phase current acquisition circuit principle. Figure 3 (b) is the schematic diagram of the B-phase current acquisition circuit principle. Figure 3 (c) is a schematic diagram of the principle of the C-phase current collection circuit;

[0046] Figure 4 A schematic diagram of the circuit principle of the MCU provided for this application;

[0047] Figure 5 A schematic diagram of the circuit principle of the flexible control module provided for this application;

[0048] Figure 6 A schematic diagram of the rigidity control module circuit provided for this application;

[0049] Figure 7 A schematic diagram of the output voltage regulation results of the photovoltaic inverter provided in this application. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0051] With the increasing application of photovoltaic power generation, in order to improve the power generation efficiency of photovoltaic inverters and ensure the safe and stable operation of the power grid, in recent years, the power grid and photovoltaic users have gradually begun to pay attention to the regulation of photovoltaic inverters. At present, centralized regulation is adopted for the regulation of photovoltaic inverters, that is, the power generation power of photovoltaic inverters is adjusted through the master station dispatching system. In the power grid architecture, there are management systems, collection front ends, etc., which are collectively referred to as master station dispatching systems. A master station dispatching system corresponds to multiple substations. When regulating photovoltaic inverters, each substation collection terminal reads the user meter and sends the collected data to the master station dispatching system for judgment. The master station dispatching system sends the control instructions to each substation terminal based on the judgment results. The substation terminal sends the control instructions to the inverter controller through the substation communication. The inverter controller adjusts the power generation power of the photovoltaic inverter through buses such as 485 / 232.

[0052] However, the data transmission link is relatively long during the regulation process. Although the current HPLC transmission speed is relatively fast, it can only guarantee a collection frequency of 5 minutes, and the photovoltaic inverter cannot be regulated in real time. This may cause the station area to be overloaded in reverse or the voltage of the photovoltaic grid-connected user to exceed the upper limit, thereby making the grid voltage unstable or damaging the photovoltaic inverter.

[0053] In addition, a grid-connected switch is usually installed between the power grid and the photovoltaic inverter. As the physical interface between the power grid and the photovoltaic system, the design of the grid-connected switch needs to meet the requirements of independence and safety. Therefore, the master station dispatching system cannot directly connect to the grid-connected switch, nor can it directly control the state of the grid-connected switch. The closing or disconnection of the grid-connected switch needs to be determined by a special control system or operator according to the state and demand of the power grid. This also leads to the fact that the existing photovoltaic inverter control method can only control the power generation power of the photovoltaic inverter. When the output voltage of the photovoltaic inverter is too high, such as when a severe overvoltage occurs, only controlling the power generation power of the photovoltaic inverter may cause damage to the photovoltaic inverter and even affect the safe operation of the power grid.

[0054] Based on the above problems, the present application designs an integrated photovoltaic inverter control system for each photovoltaic inverter. The photovoltaic inverter control system is directly connected to the photovoltaic inverter and can collect the output electrical parameters of the photovoltaic inverter in real time. By comparing the output electrical parameters of the photovoltaic inverter with the rated grid-connected electrical parameters, the power generation power and grid-connected status of the photovoltaic inverter are adjusted in real time based on the comparison results. There is no need to collect operating parameters or issue control instructions through the main station dispatching system, thereby realizing on-site second-level control of the photovoltaic inverter.

[0055] See also Figure 1 , Figure 1 The figure shows a schematic diagram of a photovoltaic inverter control system provided by the present application. The system is arranged in a waterproof housing and specifically includes:

[0056] An electrical parameter acquisition module 10, whose input end is connected to the photovoltaic inverter, is used to collect the output electrical parameters of the photovoltaic inverter in real time;

[0057] MCU20 is connected to the output end of the electric parameter acquisition module, and is used to receive the output electric parameter of the photovoltaic inverter, and when the output electric parameter is greater than 120% of the rated grid-connected electric parameter, output a first control signal to the flexible control module; when the output electric parameter is less than 105% of the rated grid-connected electric parameter, output a second control signal to the flexible control module; when the output electric parameter is greater than 130% of the rated grid-connected electric parameter, output a third control signal to the rigid control module;

[0058] The flexible control module 30 is connected to the MCU and the photovoltaic inverter, and is used to receive a first control signal and a second control signal sent by the MCU, and control the power generation of the photovoltaic inverter to decrease at a preset ratio based on the first control signal, and control the power generation of the photovoltaic inverter to increase at a preset ratio based on the second control signal;

[0059] The rigid control module 40 is connected to the MCU and the grid-connected switch, and is used to receive a third control signal sent by the MCU and control the grid-connected switch to disconnect based on the third control signal; wherein the grid-connected switch is set between the photovoltaic inverter and the power grid.

[0060] Specifically, according to industry standards, when the output electrical parameters of the photovoltaic inverter are greater than 120% of the rated grid-connected electrical parameters, it means that the photovoltaic inverter is slightly over-voltaged; when its output electrical parameters are less than 105% of the rated grid-connected electrical parameters, it means that the output power of the photovoltaic inverter is low; when its output electrical parameters are greater than 130% of the rated grid-connected electrical parameters, it indicates that the photovoltaic inverter is severely over-voltaged; in a specific example of the present application, when the collected output electrical parameters are voltage signals, 120% of the rated grid-connected voltage is 255V, 105% of the rated grid-connected voltage is 235V, and 130% of the rated grid-connected voltage is 275V.

[0061] Preferably, considering that photovoltaic inverters are usually installed outdoors, the photovoltaic inverter control system is installed in a waterproof casing with a waterproof grade of IP65, which can not only effectively prevent water droplets from entering, but also withstand low-pressure water jets from any angle, ensuring that the equipment can still operate normally in a humid or rainy environment. At the same time, the IP65 waterproof casing can also effectively prevent external dust from invading, ensure the internal cleanliness of the equipment, and reduce equipment failures and damages caused by dust.

[0062] The present application designs an integrated control system for each photovoltaic inverter, which can collect the output electrical parameters of the photovoltaic inverter in real time. The MCU compares the collected output electrical parameters with the rated grid-connected electrical parameters. When the photovoltaic inverter is slightly over-voltage (the output electrical parameters are greater than 120% of the rated grid-connected electrical parameters), the MCU outputs a first control signal to the flexible control module, and the flexible control module controls the photovoltaic inverter to reduce its power generation according to a preset ratio; when the photovoltaic inverter has a low power generation efficiency (the output electrical parameters are less than 105% of the rated grid-connected electrical parameters), the MCU outputs a second control signal to the flexible control module, and controls the photovoltaic inverter to increase its power generation according to a preset ratio to ensure its power generation; when the photovoltaic inverter is severely over-voltage (the output electrical parameters are greater than 130% of the rated grid-connected electrical parameters), the MCU outputs a third control signal to the rigid control module, controls the grid-connected switch to be disconnected, and prohibits the photovoltaic inverter from being connected to the grid.

[0063] The present application can not only monitor the operating parameters of the photovoltaic inverter in real time and regulate the photovoltaic inverter in seconds, but also directly change the state of the grid-connected switch through the rigid control module, thereby prohibiting the photovoltaic inverter from being connected to the grid when the output voltage of the photovoltaic inverter is too high, while ensuring the power generation efficiency of the photovoltaic inverter and the operational safety of the power grid.

[0064] Optionally, in some embodiments of the present application, the electrical parameter acquisition module 10 includes a voltage acquisition submodule and a current acquisition submodule;

[0065] Specifically, the voltage acquisition submodule includes:

[0066] A voltage divider circuit, an input end of which is connected to an output end of the photovoltaic inverter;

[0067] A first sampling circuit, whose input terminal is connected to the output terminal of the voltage divider circuit and whose output terminal is grounded;

[0068] The first filter circuit has an input end connected to the output end of the voltage divider circuit, and an output end connected to the MCU.

[0069] Optionally, in some embodiments of the present application, the voltage divider circuit is composed of multiple resistors connected in series, the first sampling circuit is a high-precision sampling resistor, and the first filtering circuit is composed of a resistor and a capacitor, wherein one end of the resistor in the first filtering circuit serves as the input end of the first filtering circuit, and the other end is connected to the positive pole of the capacitor as the output end of the first filtering circuit, and the negative pole of the capacitor is grounded.

[0070] like Figure 2 The schematic diagram of the circuit principle for collecting the three-phase voltage of the photovoltaic inverter provided by the present application is shown as follows: Figure 2 (a) Figure 2 (b) and Figure 2 As shown in (c), they are schematic diagrams of the circuit principles for collecting the A-phase, B-phase and C-phase voltages of the photovoltaic inverter. Figure 2 Taking (a) in the figure as an example, the A-phase voltage of the photovoltaic inverter passes through the voltage divider resistors R1~R6, passes through the high-precision sampling resistor R7, and then enters the single-ended sampling input port after filtering by the filter circuit composed of R8 and C1 to obtain the A-phase sampling voltage value of the photovoltaic inverter.

[0071] Specifically, the current acquisition submodule includes:

[0072] A three-phase current transformer, whose input end is connected to the output end of the photovoltaic inverter;

[0073] A second sampling circuit, whose input end is connected to the positive output end of the three-phase current transformer and whose output end is grounded;

[0074] A second filter circuit, whose input end is connected to the positive output end of the three-phase current transformer, and whose output end is connected to the MCU;

[0075] A third sampling circuit, whose input terminal is connected to the negative output terminal of the three-phase current transformer and whose output terminal is grounded;

[0076] The third filtering circuit has an input end connected to the negative output end of the three-phase current transformer and an output end connected to the MCU.

[0077] like Figure 3 The following is a schematic diagram of the circuit principle for collecting the three-phase current of the photovoltaic inverter provided by the present application. Figure 3 (a) Figure 3 (b) and Figure 3 As shown in (c), they are schematic diagrams of the circuit principles for collecting the A-phase, B-phase and C-phase currents of the photovoltaic inverter. Figure 3 Taking (a) in the figure as an example, the A-phase current of the photovoltaic inverter is converted into a secondary current through a three-phase current transformer. The secondary current passes through a symmetrically placed high-precision sampling resistor R 25 and R 26 , and then through R 27 The filter circuit composed of C4 filters the current and enters the differential sampling input port to obtain the A-phase sampling current value of the photovoltaic inverter.

[0078] Furthermore, if Figure 4 Shown is a schematic diagram of the MCU provided in this application. As shown in the figure, the model of the MCU in this application is HC32F4A0 / DHC32FS6.

[0079] Optionally, in some embodiments of the present application, the flexible control module may be an inverter controller, which receives a control signal sent by the MCU and converts the control signal into a signal that the photovoltaic inverter can receive, thereby regulating the power generation power of the photovoltaic inverter.

[0080] However, inverter controllers and photovoltaic inverters produced by different manufacturers may have the following problems: 1. Physical interface mismatch, resulting in the inability to properly connect or communicate between devices; 2. Inconsistent communication protocols, resulting in the inverter controller being unable to read the status data of the photovoltaic inverter or unable to send control instructions; 3. Technical specifications do not match, such as the voltage range, current size or power level of the two are different, resulting in the equipment not being able to work properly or causing safety problems.

[0081] Based on the above problems, preferably, the flexible control module in the embodiment of the present application is implemented using a 485, 232 or TTL communication circuit. When the photovoltaic inverter is controlled using a 485, 232 or TTL communication circuit, the MCU only needs to send specific parameter values ​​to the photovoltaic inverter, and the photovoltaic inverter can work according to the received parameter values.

[0082] Specifically, Figure 5 The figure shows a schematic diagram of the circuit principle of the flexible control module provided by the present application, which specifically includes:

[0083] The RS485 chip has a receiver output end connected to the third I / O port of the MCU, a receiver output enable end and a driver output enable end connected to the fourth I / O port of the MCU, and a driver input end connected to the fifth I / O port of the MCU; when the driver output enable end is at a high level, the first control signal or the second control signal sent by the MCU is received through the driver input end; when the receiver output enable end is at a low level, the first control signal or the second control signal is sent to the first output end and the second output end of the RS485 chip through the receiver output end;

[0084] A first transient voltage suppression diode, whose anode is connected to the first output terminal of the RS485 chip as the first output terminal of the flexible control module, the first output terminal of the flexible control module is connected to the input terminal of the photovoltaic inverter, and whose cathode is grounded;

[0085] A second transient voltage suppression diode, an anode of which is connected to the second output terminal of the RS485 chip, and a cathode of which is grounded;

[0086] A solid-state discharge tube, one end of which is connected to the anode of the first transient voltage suppression diode, and the other end of which is connected to the anode of the second transient voltage suppression diode;

[0087] The thermistor has one end connected to the second output end of the RS485 chip and the other end serving as the second output end of the flexible control module. The second output end of the flexible control module is connected to the input end of the photovoltaic inverter.

[0088] Preferably, the flexible control module further includes:

[0089] A first resistor, one end of which is connected to the first output terminal of the RS485 chip, and the other end of which is grounded;

[0090] A second resistor, one end of which is connected to the second output terminal of the RS485 chip, and the other end of which is grounded;

[0091] A third resistor has one end connected to the first output end of the RS485 chip, and the other end connected to the anode of the first transient voltage suppression diode.

[0092] This application uses 485 communication circuit to realize the control command transmission between MCU and photovoltaic inverter, which has high flexibility and scalability. Data interaction can be realized even between MCU and photovoltaic inverter produced by different manufacturers, which reduces the difficulty of system integration and reduces the additional cost caused by compatibility issues between equipment of different manufacturers.

[0093] Specifically, the grid-connected switch arranged between the photovoltaic inverter and the grid may be a miniature circuit breaker or a molded case switch. When the grid power is above 60kW, the grid-connected switch is a molded case switch, and when the grid power is within 60kW, the grid-connected switch is a miniature circuit breaker.

[0094] Optionally, after the rigid control module controls the grid-connected switch to disconnect based on the third control signal, the method further includes:

[0095] When the output electrical parameter of the photovoltaic inverter is less than or equal to 130% of the rated grid-connected electrical parameter or the grid-connected switch is disconnected for a period of time equal to a preset period of time, the MCU outputs a fourth control signal to the rigid control module so that the rigid control module controls the grid-connected switch to close based on the fourth control signal.

[0096] For example, when the preset control strategy is met, the MCU can send a fourth control signal to control the grid-connected switch to close, so that the photovoltaic inverter is normally connected to the grid; the preset control strategy can be that the output electrical parameters of the photovoltaic inverter are restored to the normal electrical parameter range that can be connected to the grid, or the grid-connected switch between the photovoltaic inverter and the power grid is disconnected for a preset time.

[0097] In the existing photovoltaic inverter control method, only flexible regulation of the photovoltaic inverter's power generation can be achieved, that is, only regulation of the photovoltaic inverter's power generation can be achieved. However, when the output electrical parameters of the photovoltaic inverter are greater than 1.3 times the rated grid-connected electrical parameters, that is, when a serious overvoltage occurs, only regulating the photovoltaic inverter's power generation may cause damage to the photovoltaic inverter and even affect the safe operation of the power grid.

[0098] Based on this, the rigid control module provided in the present application directly controls the grid-connected switch between the photovoltaic inverter and the power grid to be disconnected when the photovoltaic inverter is severely over-voltaged, prohibiting the photovoltaic inverter from being connected to the grid. When the output electrical parameters of the photovoltaic inverter are restored to the grid-connected range, the grid-connected switch is controlled to be closed, so that the photovoltaic inverter is connected to the grid, thereby ensuring the safe operation of the power grid to a great extent.

[0099] Specifically, the rigidity control module 40 provided in the present application specifically includes:

[0100] A motor drive chip, wherein the first input end thereof serves as the first input end of a rigid control module, the second input end thereof serves as the second input end of the rigid control module, the first output end thereof serves as the first output end of the rigid control module, and the second output end thereof serves as the second output end of the rigid control module; the first input end of the rigid control module is connected to the first I / O port of the MCU, the second input end of the rigid control module is connected to the second I / O port of the MCU, and the first output end and the second output end of the rigid control module are both connected to the grid-connected switch; and when the MCU outputs a third control signal in which the first I / O port is high and the second I / O port is low, outputs a forward current to control the grid-connected switch to be disconnected; and when the MCU outputs a fourth control signal in which the first I / O port is low and the second I / O port is high, outputs a reverse current to control the grid-connected switch to be closed;

[0101] A resistor parallel circuit, whose input end is connected to the current detection input end of the motor drive chip and whose output end is grounded;

[0102] The capacitor parallel circuit has an input end connected to the power supply voltage input end of the motor drive chip and an output end connected to the ground.

[0103] For example, Figure 6 As shown, in a specific example of the present application, the resistor parallel circuit includes two resistors R 37 and R 38 , the capacitor parallel circuit includes 4 capacitors C 10 ~C 13 The model of the motor drive chip is SA8870. The two input terminals of the chip are connected to the two I / O ports of the MCU as the first input terminal and the second input terminal of the rigid control module respectively. The two output terminals of the chip are connected to the grid-connected switch as the first output terminal and the second output terminal of the rigid control module. The logic of controlling the grid-connected switch to be closed or disconnected based on the control signal sent by the MCU is shown in Table 1:

[0104] Table 1

[0105] IN1 IN2 OUT1 OUT2 Description 0 0 High-Z High-Z Motor does not rotate 0 1 L H Reverse current 1 0 H L Forward Current 1 1 L L Not working

[0106] The control signal controls the high / low level of the input pin of the motor driver chip, so that the motor driver chip outputs forward / reverse current, drives the motor in the device to rotate forward or reverse, and thus controls the grid-connected switch to open or close.

[0107] In order to verify the effectiveness of the photovoltaic inverter control system provided by the present application, the present application embodiment also provides a schematic diagram of the result of using the system to control the output voltage of the photovoltaic inverter, such as Figure 7As shown, the horizontal axis in the figure represents the light intensity, the vertical axis represents the output voltage of the photovoltaic inverter, and the three curves in the figure are the output voltage change curves of phase A, phase B and phase C of the photovoltaic inverter respectively. It can be seen from the figure that as the sunlight increases, the actual output power of the photovoltaic inverter gradually increases, and its output voltage continues to rise to 236V. By using the photovoltaic inverter control system provided by the present application to continuously adjust its power generation power, its output voltage no longer increases, but gradually stabilizes at around 235V, ensuring the safety of the photovoltaic inverter being connected to the grid.

[0108] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A photovoltaic inverter control system, characterized in that: Set in a waterproof housing, comprising: An electrical parameter acquisition module, whose input end is connected to the photovoltaic inverter, is used to collect the output electrical parameters of the photovoltaic inverter in real time; MCU, connected to the output end of the electrical parameter acquisition module, for receiving the output electrical parameter of the photovoltaic inverter, and when the output electrical parameter is greater than 120% of the rated grid-connected electrical parameter, outputting a first control signal to the flexible control module; when the output electrical parameter is less than 105% of the rated grid-connected electrical parameter, outputting a second control signal to the flexible control module; when the output electrical parameter is greater than 130% of the rated grid-connected electrical parameter, outputting a third control signal to the rigid control module; a flexible control module, connected to the MCU and the photovoltaic inverter, configured to receive a first control signal and a second control signal sent by the MCU, and control the power generation of the photovoltaic inverter to decrease at a preset ratio based on the first control signal, and control the power generation of the photovoltaic inverter to increase at a preset ratio based on the second control signal; A rigid control module is connected to the MCU and the grid-connected switch, and is used to receive a third control signal sent by the MCU, and control the grid-connected switch to disconnect based on the third control signal; wherein the grid-connected switch is arranged between the photovoltaic inverter and the power grid.

2. The photovoltaic inverter control system according to claim 1, characterized in that: After the rigid control module controls the grid-connected switch to be disconnected based on the third control signal, the rigid control module further includes: When the output electrical parameter of the photovoltaic inverter is less than or equal to 130% of the rated grid-connected electrical parameter or the disconnection time of the grid-connected switch is equal to the preset time, the MCU outputs a fourth control signal to the rigidity control module so that the rigidity control module controls the grid-connected switch to close based on the fourth control signal.

3. The photovoltaic inverter control system according to claim 2, characterized in that: The rigidity control module comprises: A motor drive chip, wherein the first input end thereof serves as the first input end of the rigid control module, the second input end thereof serves as the second input end of the rigid control module, the first output end thereof serves as the first output end of the rigid control module, and the second output end thereof serves as the second output end of the rigid control module; the first input end of the rigid control module is connected to the first I / O port of the MCU, the second input end of the rigid control module is connected to the second I / O port of the MCU, and the first output end and the second output end of the rigid control module are both connected to the grid-connected switch; when the MCU outputs a third control signal in which the first I / O port is high and the second I / O port is low, outputting a forward current to control the grid-connected switch to be disconnected; when the MCU outputs a fourth control signal in which the first I / O port is low and the second I / O port is high, outputting a reverse current to control the grid-connected switch to be closed; A resistor parallel circuit, whose input end is connected to the current detection input end of the motor drive chip and whose output end is grounded; The capacitor parallel circuit has an input end connected to the power supply voltage input end of the motor drive chip and an output end connected to the ground.

4. The photovoltaic inverter control system according to claim 1, characterized in that: The flexible control module comprises: An RS485 chip, whose receiver output end is connected to the third I / O port of the MCU, whose receiver output enable end and driver output enable end are connected to the fourth I / O port of the MCU, and whose driver input end is connected to the fifth I / O port of the MCU; when the driver output enable end is at a high level, the first control signal or the second control signal sent by the MCU is received through the driver input end; when the receiver output enable end is at a low level, the first control signal or the second control signal is sent to the first output end and the second output end of the RS485 chip through the receiver output end; A first transient voltage suppression diode, whose anode is connected to the first output terminal of the RS485 chip as the first output terminal of the flexible control module, the first output terminal of the flexible control module is connected to the input terminal of the photovoltaic inverter, and whose cathode is grounded; A second transient voltage suppression diode, an anode of which is connected to the second output terminal of the RS485 chip, and a cathode of which is grounded; a solid-state discharge tube, one end of which is connected to the anode of the first transient voltage suppression diode, and the other end of which is connected to the anode of the second transient voltage suppression diode; A thermistor, one end of which is connected to the second output end of the RS485 chip, and the other end of which serves as the second output end of the flexible control module, and the second output end of the flexible control module is connected to the input end of the photovoltaic inverter.

5. The photovoltaic inverter control system according to claim 4, characterized in that: The flexible control module also includes: A first resistor, one end of which is connected to the first output terminal of the RS485 chip, and the other end of which is grounded; A second resistor, one end of which is connected to the second output end of the RS485 chip, and the other end of which is grounded; A third resistor has one end connected to the first output end of the RS485 chip, and the other end connected to the anode of the first transient voltage suppression diode.

6. The photovoltaic inverter control system according to claim 1, characterized in that: The electrical parameter acquisition module includes a voltage acquisition submodule and a current acquisition submodule.

7. The photovoltaic inverter control system according to claim 6, characterized in that: The voltage acquisition submodule comprises: A voltage divider circuit, an input end of which is connected to an output end of the photovoltaic inverter; A first sampling circuit, whose input end is connected to the output end of the voltage divider circuit and whose output end is grounded; The first filter circuit has an input end connected to the output end of the voltage divider circuit, and an output end connected to the MCU.

8. The photovoltaic inverter control system according to claim 6, characterized in that: The current acquisition submodule comprises: A three-phase current transformer, whose input end is connected to the output end of the photovoltaic inverter; A second sampling circuit, whose input end is connected to the positive output end of the three-phase current transformer and whose output end is grounded; A second filter circuit, whose input end is connected to the positive output end of the three-phase current transformer, and whose output end is connected to the MCU; A third sampling circuit, whose input end is connected to the negative output end of the three-phase current transformer and whose output end is grounded; The third filtering circuit has an input end connected to the negative output end of the three-phase current transformer and an output end connected to the MCU.

9. The photovoltaic inverter control system according to claim 1, characterized in that: The model of the MCU is HC32F4A0 / DHC32FS6.

10. The photovoltaic inverter control system according to claim 1, characterized in that: The waterproof grade of the waterproof housing is IP65.

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