WO2017148241A1

WO2017148241A1 - Inverter control method, device, and power generation system

Info

Publication number: WO2017148241A1
Application number: PCT/CN2017/072977
Authority: WO
Inventors: 张勇
Original assignee: 中兴通讯股份有限公司
Priority date: 2016-02-29
Filing date: 2017-02-06
Publication date: 2017-09-08
Also published as: CN107134917A

Abstract

An inverter control method, a device (1), and a power generation system. The inverter control method comprises: monitoring an input voltage of an inverter (S201); comparing the input voltage and a preconfigured stop voltage (S202); when the input voltage is less than the preconfigured stop voltage, turning off a power supply supplying power to the inverter (S203). By monitoring the input voltage of the inverter, and turning off the power supply supplying power to the inverter when the input voltage is less than the stop voltage, a control circuit of the inverter can be turned off completely. Moreover, by employing time information indicating that whether it is in the nighttime, the embodiment can further reduce local power losses during the nighttime when the inverter is unable to generate power, increasing power generation efficiency.

Description

Inverter control method, device and power generation system

Technical field

The invention relates to the field of photovoltaic power generation, and in particular to an inverter control method, device and power generation system.

Background technique

As the two most important components in the photovoltaic grid-connected power generation system, solar panels and inverters have become an important indicator for evaluating the quality of the system. Although solar energy resources are theoretically inexhaustible, due to the low radiation density of sunlight, most solar panels and conversion efficiencies are only about 10% to 20%. In this context, the conversion efficiency of photovoltaic inverters should be increased as much as possible to maximize the efficiency of the entire photovoltaic system.

Solar photovoltaic inverters generally have automatic operation and automatic shutdown function. After morning sunrise, the radiation intensity of sunlight gradually increases, and the output of solar panels increases accordingly. When the output voltage of solar panels reaches the inverter. When the input voltage is low, the inverter can be powered on automatically. The inverter's monitoring system can monitor the output of the solar panel at all times. As long as the output power of the solar panel is greater than the output power required by the inverter, the inverter can continue to operate. In the evening sunset, the output of the solar panel is gradually smaller than the output required by the inverter. The inverter can automatically shut down and enter the standby state. When it is sunrise the next morning, it will automatically turn on and run daily.

When the solar photovoltaic inverter enters the evening, the input voltage is too low and enters the standby state. At this time, the inverter can no longer generate electricity, but the control circuit of the inverter is still in a power consumption state. This part of the loss is of no value. of. In the current technology, the nighttime self-loss of the photovoltaic inverter is generally maintained at the level of 100W, and no corresponding treatment measures are taken for the power consumed in this part, so that some of the power consumption is consumed, which is compared with the photovoltaic inverter focusing on efficiency. Hard to accept. Therefore, it is more important to reduce the self-loss of the photovoltaic inverter at night.

Therefore, how to provide an inverter management method that can reduce the power consumption of a nighttime inverter is a technical problem to be solved by those skilled in the art.

Summary of the invention

The invention provides an inverter control method, device and power generation system to solve the problem that the existing inverter has unnecessary power consumption at night when working.

The invention provides an inverter control method, which comprises:

Monitor the input voltage of the inverter;

Comparing the input voltage with a preset stop voltage;

When the input voltage is lower than the stop voltage, turn off the power supply of the inverter.

Turning off the power supply of the inverter includes: turning off the power supply of the inverter through the electromagnetic coil.

Monitoring the input voltage of the inverter includes: obtaining the input voltage of the inverter by means of optocoupler isolation.

When the input voltage is lower than the stop voltage, before the inverter is turned off, the method further includes: determining whether it is in a nighttime period, and if so, turning off the inverter, and if not, turning off the inverter.

After the inverter is turned off, the method further includes: detecting whether it is in a daylight period, and if so, turning on the inverter.

The invention provides an inverter control device, comprising:

a monitoring module for monitoring an input voltage of the inverter;

Alignment module for comparing the input voltage with a preset stop voltage;

The control module is configured to turn off the power supply of the inverter when the input voltage is lower than the stop voltage.

The control module is configured to turn off the power supply of the inverter through the electromagnetic coil.

The monitoring module is used to obtain the input voltage of the inverter by means of optocoupler isolation.

When the input voltage is lower than the stop voltage, before the inverter is turned off, the control module is also used to determine whether it is in the night time period, and if so, the inverter is turned off, and if not, the inverter is not turned off.

After the inverter is turned off, the control module is also used to detect whether it is in the daytime period, and if so, turn on the inverter.

The present invention provides a power generation system including a photovoltaic panel, an inverter, and an inverter control device provided by the present invention.

The beneficial effects of the invention:

The invention provides a new inverter control method, by monitoring the input voltage of the inverter, when the voltage is lower than the stop voltage, the power supply of the inverter is turned off, and the control circuit of the inverter is completely turned off to reduce The power consumption of the inverter's control circuit at night. Further, by sampling the input voltage of the inverter and combining it with the time information at night, it can be realized that the inverter can not significantly generate power at night when the input voltage of the inverter is insufficient, and the inverter can be greatly reduced at night by this method. The loss of power generation increases the efficiency of inverter power generation.

DRAWINGS

1 is a schematic structural diagram of an inverter control apparatus according to a first embodiment of the present invention;

2 is a flowchart of a method for controlling an inverter according to a second embodiment of the present invention;

3 is a schematic structural diagram of an inverter control apparatus according to a third embodiment of the present invention;

4 is a circuit diagram of an inverter control device in a third embodiment of the present invention;

FIG. 5 is a flowchart of a method for controlling an inverter in a third embodiment of the present invention.

detailed description

The invention will now be further illustrated by way of specific embodiments in conjunction with the accompanying drawings.

First embodiment:

FIG. 1 is a schematic structural diagram of an inverter control apparatus according to a first embodiment of the present invention. In this embodiment, the inverter control device 1 provided by the present invention includes:

a monitoring module 11 for monitoring an input voltage of the inverter;

The comparison module 12 is configured to compare the input voltage with a preset stop voltage;

The control module 13 is configured to turn off the power supply of the inverter when the input voltage is lower than the stop voltage.

In some embodiments, the control module 13 in the above embodiment is used to turn off the power supply of the inverter through the electromagnetic coil.

In some embodiments, the monitoring module 11 in the above embodiment is configured to acquire an input voltage of the inverter by means of optocoupler isolation.

In some embodiments, when the input voltage is lower than the stop voltage, before the inverter is turned off, the control module 13 in the above embodiment is further configured to determine whether it is in the night time period, and if so, turn off the inverter, if not , the inverter is not turned off.

In some embodiments, after the inverter is turned off, the control module 13 in the above embodiment is further configured to detect whether it is in a daytime period, and if so, turn on the inverter.

Correspondingly, the present invention provides a power generation system including a photovoltaic panel, an inverter, and an inverter control device provided by the present invention.

Second embodiment:

FIG. 2 is a flowchart of a method for controlling an inverter according to a second embodiment of the present invention. As shown in FIG. 2, in the embodiment, the inverter control method provided by the present invention includes the following steps:

S201: monitoring an input voltage of the inverter;

S202: comparing the input voltage with a preset stop voltage;

S203: When the input voltage is lower than the stop voltage, the power supply of the inverter is turned off.

In some embodiments, the power supply for turning off the inverter in the above embodiment includes: turning off the power supply of the inverter through the electromagnetic coil.

In some embodiments, the input voltage of the monitoring inverter in the above embodiment includes: acquiring an input voltage of the inverter by means of optocoupler isolation.

In some embodiments, when the input voltage is lower than the stop voltage, before the inverter is turned off, the method in the above embodiment further includes: determining whether it is in a night time period, and if so, turning off the inverter, if not, then Do not turn off the inverter.

In some embodiments, after the method of the above embodiment is turned off, the method further includes: detecting whether it is in a daytime period, and if so, turning on the inverter.

The present invention will be further explained in conjunction with specific application scenarios.

Third embodiment:

The problem with the prior art is that the non-power circuit of the inverter is not controlled at night, and is always in the standby state, and at this time, it is impossible to generate electricity. The invention provides a method for reducing the self-loss of the inverter at night, by sampling the input voltage of the inverter and judging the state of the inverter according to the time information of the monitoring system. When the input voltage is low at night and the power cannot be generated, the control power of the inverter is cut off, and only the power supply of the monitoring system is retained. When the inverter meets the power generation condition in the morning, the monitoring system receives the power-on command and then turns on the power of the control circuit. Let the inverter start generating electricity. Using this method minimizes the self-loss of the inverter at night. At this time, the self-loss of the inverter only includes the monitoring system, and the loss of the monitoring system is relatively small, thus solving the existing A series of problems in technology.

The technical problem to be solved by the present invention is that the present invention overcomes the problem of large loss of nighttime of the photovoltaic inverter in the prior art, and controls the inverter auxiliary by sampling the input voltage of the inverter and combining with the time information at night. The input end of the power transformer can realize the control of the auxiliary power supply part of the inverter when the inverter input voltage is insufficient to generate electricity at night, and only the power supply of the monitoring part is retained. The power supply in the monitoring section is reserved to turn on the control auxiliary power supply the next morning to make the inverter work normally. By this method, the loss of the inverter when it cannot generate electricity at night can be greatly reduced, and the power generation efficiency of the inverter is improved.

As shown in FIG. 3, the inverter control device for reducing the nighttime loss of the photovoltaic inverter provided by the present invention comprises a voltage sampling circuit 31 for sampling the output voltage of the photovoltaic panel, and the main control unit 32 for controlling the output of the inverter, monitoring the inverse The monitoring unit 33 of the transformer state, the timer 34 for counting the time, the control power source 35 for supplying the voltage sampling circuit and the main control unit, the monitoring power source 36 for supplying power to the monitoring unit, and the output terminal of the voltage sampling circuit 31 are connected. To the input end of the main control unit 32, the main control unit 32 and the monitoring unit 33 are connected to each other, the output of the timer 34 is connected to the input end of the monitoring unit 33, and the output terminals of the control power source 35 are respectively connected to The voltage sampling circuit 31 and the main control unit 32, the output of the monitoring power supply 36 is connected to a monitoring unit 33, which is connected to the control power source 35.

Specifically, according to the functional module, which includes: A, the voltage sampling circuit for sampling the input voltage of the inverter in FIG. 3; B, the main control unit for controlling the output state of the photovoltaic inverter in FIG. 3; The monitoring unit for monitoring the inverter state and operating the inverter main control unit in FIG. 3; D, the timer for recording time information in FIG. 3; E, the power supply for the control unit in FIG. Control power supply (isolated from monitoring power supply, independent power supply); F, Figure 3, monitoring power supply for monitoring unit (isolated from control power supply, independent power supply); G, control power switching circuit in Figure 4, where relay K1 is used The switching switch of the control power supply, the control coil side of K1 is powered and controlled by the monitoring system. A, B, C, and D constitute the control part of the photovoltaic inverter. The auxiliary power control system composed of E, F, and G can realize the night energy saving by turning on or off the control power of the inverter. Inverter control system.

In the present invention, the voltage sampling circuit samples the output voltage of the photovoltaic panel, that is, the input voltage of the inverter, for controlling the operating state of the inverter, the main control unit is used to control the output of the inverter, and the monitoring unit is used for The operation data of the main control unit is collected, and corresponding commands are issued to the main control unit, and the timer is used to time the inverter every day. The monitoring unit can issue a corresponding command to the main control unit according to the timing information and the relevant state, and the control power source is used to supply power to the voltage sampling circuit and the main control unit, and the monitoring power supply is used to supply power to the monitoring unit. The main control unit and the monitoring unit realize communication and data exchange through optocoupler isolation.

By using the method and device provided by the present invention, compared with the prior art, in the case where the control circuit is relatively simple, The goal of reducing the nighttime loss of the photovoltaic inverter is maximized. Taking a 500 KW photovoltaic inverter as an example, when the control circuit and the power supply are turned off by the method of the present invention, the photovoltaic inverter can save at least 100 W of power consumption. With photovoltaic inverters that can't generate electricity for 10 hours at night, a PV inverter can save 1 kWh per night and save 365 kWh a year. Therefore, the present invention provides a low-cost, reliable and energy-saving way for the user, improves the power generation efficiency of the product, and enhances the competitiveness of the product.

In the present invention, as shown in FIG. 4, the specific circuit configuration of the control power supply circuit 35 is as follows:

The control power supply circuit 35 is respectively connected to the neutral line and the live line of the AC power grid through the T1 and T2 terminals, and the T1 end is connected to the input end of the power frequency transformer Tr through the contact of the relay K1, and the T2 terminal is directly connected to the power frequency transformer. The other end of the Tr input. The coil end of the relay K1 is powered by the monitoring power supply and is controlled by the monitoring unit. The control transformer Tr inputs the grid voltage of the input terminal to the rectifying and filtering circuit composed of D1 and C1 after being isolated and stepped down. The output of the rectifying and filtering circuit composed of D1 and C1 is connected to the input terminal of the DC/DC power supply module U1. The output of the DC/DC power module U1 is a DC48V power supply, the +48V terminal is named T3, and the corresponding GND terminal is named T4.

Among them, the control power source 35 is mainly used as a control auxiliary power supply part of the photovoltaic inverter, and the DC48V of the power supply output is available for the control part circuit, and the focus of the present invention lies in the control of the relay K1 in the part of the circuit. As described above, the coil of the relay K1 is controlled by the monitoring unit, and the relay K1 is a normally closed contact relay. The voltage sampling circuit is transmitted to the main control unit after sampling the input voltage of the inverter, and the main control unit transmits the voltage data to the monitoring unit through the optocoupler isolation communication after processing the sampled voltage value. The monitoring unit judges whether it is day or night according to the information of the timer. If it is nighttime and the input voltage of the inverter is lower than the limit value, the monitoring unit judges that the state is a state in which power generation cannot be performed at night, and at this time, an energy-saving control signal is issued, and the control is performed. The contact of relay K1 is open. The control power supply is cut off by the contact of the relay K1, the output DC48V is powered off, the voltage sampling circuit and the main control unit are completely powered down, and the inverter is turned off without output, achieving the purpose of nighttime energy saving.

The following is a description of the specific implementation process of the present invention from three periods of daytime normal state, nighttime energy saving state, and early morning restart. For convenience of description, the normal operating voltage range of the inverter is marked as Vmin to Vmax, and the input voltage when the nighttime inverter is stopped is marked as Vstop. The specific work process is shown in Figure 5. As shown in FIG. 5, the inverter control method includes the following steps:

S501: When the daytime is normal, the solar panel has sufficient illumination, and the input voltage of the inverter is generally Vmin~Vmax. Within the input voltage range, the main power part of the photovoltaic inverter can work normally. After the voltage sampling circuit samples the input voltage, the voltage value is transmitted to the digital signal processor in the main control unit, and the digital signal processor processes and stores the voltage value and transmits it to the monitoring unit through the optocoupler-isolated CAN communication circuit. . The monitoring unit according to the received input voltage value, combined with the timer timing information is between 6:00 and 20:00, can determine that the state is the daytime input voltage normal state, at this time, the monitoring unit pairs the relay K1 No control signal is sent. Since the relay K1 is a normally closed contact relay, the AC grid can be connected to the input end of the power frequency transformer Tr through the contact of the relay K1, the control power circuit is turned on, the output T3 and T4 terminals are DC48V voltage, and the power supply of the main control unit is normal. The inverter outputs normally.

S502-S507: At night, the inverter input voltage gradually decreases due to the gradual weakening of the solar panel illumination. When the inverter input voltage is lower than Vstop, the voltage value is transmitted to the main control unit via the sampling circuit, and the main control unit transmits the voltage value to the monitoring unit via the CAN communication circuit. The monitoring unit further determines that the state is a state in which power generation cannot be generated at night according to the information of the timer. At this time, the monitoring unit sends a control signal to the relay K1 to drive the contact of the relay K1. open. Since the contact of relay K1 is disconnected, the voltage of the AC grid cannot be connected to the power frequency transformer Tr, the control power supply is powered down, there is no DC48V output, the voltage sampling circuit and the main control unit have no power supply, the inverter is turned off without output, and the energy is saved at night. mode.

S508: In the early morning of the next day, the light gradually increases, and the input voltage of the inverter gradually increases. However, due to the power failure of the control power supply during nighttime, the voltage sampling circuit and the main control unit have no power supply. The inverter input voltage at this time. It is impossible to sample. As mentioned above, the control power supply and the monitoring power supply are separately powered independently, and the monitoring power supply is always powered down. Therefore, the timing information of the timer is always present. After the timekeeping to 6:00 am, the monitoring unit The relay K1 sends a disconnection control signal, the contact of the relay K1 is turned from off to pull-in, the control power supply starts to work, the voltage sampling circuit and the main control unit supply power normally, when the input voltage of the inverter is in the range of Vmin~Vmax , the inverter outputs normally. The control process described in this patent can be implemented as in the above process cycle.

In practical applications, the energy-saving control of the inverter needs to combine the input voltage and time of the inverter. Because the input voltage of the inverter may suddenly drop from Vmin to below Vstop during the daytime under complex weather conditions, this If the time information is not combined, controlling the inverter to be in the energy-saving mode will cause the inverter to switch on and off frequently during the day. In the present patent, the above situation is effectively avoided in accordance with the manner in which the input voltage is combined with the time information.

In addition, the normal operating input voltage range of the inverter is Vmin~Vmax, and it is in the energy-saving mode when the input voltage is lower than Vstop. The purpose of this setting is to prevent the inverter from being abnormal due to frequent switching between the normal operation mode and the energy saving mode when the inverter fluctuates around the input voltage Vmin.

The time information recorded by the monitoring unit described in this patent can be adjusted according to different application scenarios to meet the actual application of different scenarios.

In summary, through the implementation of the present invention, at least the following beneficial effects exist:

Industrial applicability

The invention relates to the field of photovoltaic power generation, which can greatly reduce the loss of the inverter when the power is not generated at night, and improve the power generation efficiency of the inverter.

The above is only a specific embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change, combination or modification to the above embodiment according to the technical essence of the present invention, All still belong to the protection scope of the technical solution of the present invention.

Claims

An inverter control method includes:

Monitoring an input voltage of the inverter;

Comparing the input voltage with a preset stop voltage;

When the input voltage is lower than the stop voltage, the power supply of the inverter is turned off.
The inverter control method according to claim 1, wherein the turning off the power supply of the inverter comprises: turning off a power supply of the inverter by an electromagnetic coil.
The inverter control method according to claim 1, wherein said monitoring said input voltage of said inverter comprises: obtaining an input voltage of said inverter by means of optocoupler isolation.
The inverter control method according to any one of claims 1 to 3, wherein, when the input voltage is lower than the stop voltage, before the inverter is turned off, the method further includes: determining whether In the night time period, if yes, the inverter is turned off, and if not, the inverter is not turned off.
The inverter control method according to claim 4, wherein after the inverter is turned off, the method further comprises: detecting whether it is in a daytime period, and if so, turning on the inverter.
An inverter control device includes:

a monitoring module configured to monitor an input voltage of the inverter;

Aligning module, configured to compare the input voltage with a preset stop voltage;

And a control module configured to turn off the power supply of the inverter when the input voltage is lower than the stop voltage.
The inverter control device according to claim 6, wherein the control module is configured to turn off a power supply of the inverter by an electromagnetic coil.
The inverter control device according to claim 6, wherein the monitoring module is configured to acquire an input voltage of the inverter by means of optocoupler isolation.
The inverter control device according to any one of claims 6 to 8, wherein, when the input voltage is lower than the stop voltage, the control module is further set to determine before the inverter is turned off. Whether it is in the night time period, if yes, the inverter is turned off, and if not, the inverter is not turned off.
The inverter control device according to claim 9, wherein, after the inverter is turned off, the control module is further configured to detect whether it is in a daylight period, and if so, turn on the inverter.
A power generation system comprising a photovoltaic panel, an inverter, and the inverter control device according to any one of claims 6 to 10.