WO2018072406A1

WO2018072406A1 - Photovoltaic system and control method therefor

Info

Publication number: WO2018072406A1
Application number: PCT/CN2017/080123
Authority: WO
Inventors: 娄贺伟; 刘克勤; 李建华; 张雪芬
Original assignee: 珠海格力电器股份有限公司
Priority date: 2016-10-21
Filing date: 2017-04-11
Publication date: 2018-04-26
Also published as: CN106300428A

Abstract

A photovoltaic system and a control method therefor. The photovoltaic system comprises a photovoltaic battery assembly (1), a converter unit (3), a first switch (4), a second switch (5), and a switch power supply (6). An output end of the photovoltaic battery assembly (1) is connected to a first end of the converter unit (3) by means of the first switch (4); a second end of the converter unit (3) is connected to a power grid (9) by means of the second switch (5). The switch power supply (6) is provided with a direct current power branch (61) and an alternating current power branch (62). A power outlet point of the direct current power branch (61) is located between the photovoltaic battery assembly (1) and the first switch (4); and a power outlet point of the alternating current power branch (62) is located between the second switch (5) and the power grid (9). The photovoltaic system can reduce standby loss of a system, improve safety and reliability of the system, and guarantee the service life of the photovoltaic battery assembly.

Description

Photovoltaic system and control method thereof

Technical field

The invention relates to the field of photovoltaic technology, and in particular to a photovoltaic system and a control method thereof.

Background technique

In the traditional sense, the photovoltaic system is often designed with the traditional inverter as its original shape, and its switching power supply is directly taken from the DC bus of the converter. In the case that the air conditioner is not turned on and the photovoltaic cell assembly does not satisfy the power generation condition (ie, no energy output), in order to ensure the detection function of the system, the DC bus is always charged (high voltage or mains), and the converter needs to be always operated. Keep the DC bus voltage stable at a fixed value.

This kind of photovoltaic system has at least the following defects: when the air conditioner is in standby, the power consumption of the whole system is large, causing unnecessary waste of electric energy; the safety requirements of the system cannot be met, and the system is inconvenient to be repaired, and the second is not disconnected. In the case of a switch, there is a risk of electric shock when the air conditioning unit or the photovoltaic cell module is inspected; the photovoltaic cell component is susceptible to the impact of the DC bus voltage and affects the life.

Summary of the invention

Based on the above state of the art, it is a primary object of the present invention to provide a photovoltaic system that solves at least one of the aforementioned drawbacks.

The above objectives are achieved by the following technical solutions:

A photovoltaic system comprising a photovoltaic cell assembly, a current conversion unit, a first switch, a second switch, and a switching power supply, wherein

The output end of the photovoltaic cell assembly is connected to the first end of the converter unit via a first switch,

The second end of the converter unit is connected to the power grid via the second switch.

The switching power supply has a DC power take-off branch and an AC power take-off branch, wherein a power take-off point of the DC power take-off branch is between the photovoltaic cell component and the first switch, and the AC power is taken The power take-off point of the branch is located between the second switch and the grid.

Preferably, a photovoltaic detection unit is further disposed between the photovoltaic cell assembly and the first switch for detecting a state of the photovoltaic cell assembly.

Preferably, a control system is further included, the control system being electrically powered by the control output of the switching power supply and for outputting a control signal to control the first switch and the second switch.

Preferably, the control system is coupled to the converter unit to detect and control the converter unit.

Preferably, the first end of the converter unit is directly connected to its DC bus.

Preferably, the switching power supply comprises a transformer, and the DC power take-off branch and the AC power take-off branch of the switching power supply are connected to a common power bus, the power bus is connected to the primary side of the transformer, and the output of the switching power supply is controlled. Electricity is output by the secondary side of the transformer.

Preferably, the converter unit comprises a three-phase bridge circuit, the three-phase bridge circuit comprises a three-phase bridge arm, each phase bridge arm comprises two power switching devices with anti-parallel diodes, the two power switches The devices respectively constitute an upper arm and a lower arm of the phase bridge arm, and a connection point between the upper arm and the lower arm of each phase bridge arm is used to connect the second switch.

Preferably, the photovoltaic system is a three-phase photovoltaic system, and the three-phase lines of the three-phase power grid are respectively connected to the connection point between the upper arm and the lower arm of each phase bridge arm via the second switch;

Alternatively, the photovoltaic system is a single-phase photovoltaic system, and the two lines of the single-phase power grid are respectively connected to the connection point between the upper arm and the lower arm of any two-phase bridge arm via the second switch.

Preferably, the device further includes an electrical device connected to the first end of the converter unit.

Preferably, the electrical equipment is an air conditioning unit.

Another object of the present invention is to provide a control method for a photovoltaic system according to the foregoing, comprising the steps of: controlling the first switch and the second switch according to a state of the photovoltaic cell assembly and/or a state of the power grid Opening and closing status.

Preferably, the first switch is turned off when the photovoltaic cell assembly does not satisfy the power generation condition.

Preferably, the second switch is turned off when the powered device of the photovoltaic system is not operating;

Alternatively, the second switch is controlled to close when the electrical equipment of the photovoltaic system needs to be operated.

Preferably, when the photovoltaic cell assembly meets a power generation condition, the first opening and closing is controlled And simultaneously controlling the second switch to close.

Preferably, when the power grid of the photovoltaic system needs to be operated and the power generation amount of the photovoltaic battery component is greater than the power consumption of the power consumption device, the first switch is controlled to be closed and controlled at the same time. The second switch is open.

The photovoltaic system and the control method thereof of the present invention, since the switching power supply adopts a dual power take-off mode, and correspondingly sets a DC side switch (first switch) and an AC side switch (second switch), and corresponding detection and control logic, at least It has the following beneficial effects: (1) can reduce the standby loss of the photovoltaic system; (2) can increase the safety and reliability of the photovoltaic system; (3) can guarantee the service life of the photovoltaic module.

DRAWINGS

Hereinafter, a photovoltaic system and a control method therefor according to the present invention will be described with reference to the accompanying drawings. In the picture:

1 is a schematic diagram of a photovoltaic system in accordance with a preferred embodiment of the present invention;

2 is a schematic diagram of a switching power supply in a photovoltaic system of the present invention.

detailed description

In order to solve the problems of the photovoltaic system in the conventional sense mentioned in the background section, the present invention provides a photovoltaic system.

As shown in FIG. 1, the photovoltaic system of the present invention comprises a photovoltaic cell assembly 1, an air conditioning unit 2, a current conversion unit 3, a first switch 4, a second switch 5, and a switching power supply (preferably a high voltage power switch) 6, wherein

An output end of the photovoltaic cell module 1 is connected to a first end (left end in the figure) of the current conversion unit 3 via a first switch 4, and the first switch may also be referred to as a DC side switch.

The second end of the current conversion unit 3 (the right end in the figure) is connected to the power grid 9 via the second switch 5, and the second switch may also be referred to as an AC side switch.

The switching power supply 6 has a DC power take-off branch 61 and an AC power take-off branch 62, wherein the power take-off point of the DC power take-off branch 61 is located between the photovoltaic cell assembly 1 and the first switch 8 (ie located on the front side of the first switch), the power take-off point of the AC power take-off branch 62 is located between the second switch 5 and the grid 9 (ie on the rear side of the second switch).

The switching power supply 6 is mainly used for outputting control power to supply power to control and detection in the system.

The photovoltaic system of the invention preferably further comprises an electrical device, in particular an air conditioning unit 2, which is connected to the first end of the converter unit 3. Thus, the photovoltaic system of the present invention constitutes a photovoltaic air conditioning system.

Since the switching power supply of the present invention adopts a dual power take-off mode, and is provided with the first switch 4 and the second switch 5, the two power take-off points of the switching power supply 6 are respectively located at the front side of the first switch 4 and the second switch 5 On the rear side, the opening and closing states of the first switch 4 and the second switch 5 do not affect the power take-off of the power take-off point. Therefore, when the air conditioner is in standby, both the first switch 4 and the second switch 5 can be disconnected, so that the inverter 3 is completely powered off, and the DC bus is no longer charged, so that the standby power consumption of the entire system can be significantly reduced.

At the same time, when the first switch 4 and the second switch 5 are both disconnected, when the air conditioning unit 2 or the photovoltaic unit 1 is inspected, the risk of electric shock can be effectively avoided, and the safety of the system is improved.

In addition, in the case where the photovoltaic cell module 1 does not generate electricity, that is, in the case where the air conditioning unit 2 is powered only by the grid 9, the photovoltaic system of the present invention can also disconnect the first switch 4, thereby cutting off the converter unit 3 and the photovoltaic The connection between the battery modules 1 can thereby avoid the influence of the DC bus voltage on the life of the photovoltaic cell assembly 1 in order to extend the service life of the photovoltaic cell assembly 1.

Preferably, the photovoltaic system of the present invention further comprises a photovoltaic detection unit 8 disposed between the photovoltaic cell assembly 1 and the first switch 4 for detecting the state of the photovoltaic cell assembly 1. The photovoltaic detecting unit 8 can detect state information such as the initial voltage and the line polarity of the photovoltaic cell component 1, for example, after initial assembly and after power-on after line maintenance, so as to avoid system damage. The photovoltaic detection unit 8 can employ prior art detection means.

Preferably, the photovoltaic system of the present invention further includes a control system 7 that is electrically powered by the control output of the switching power supply and that is used to output a control signal to control the first switch 4 and the second switch 5 . For example, the control system 7 can make specific control actions according to the state of the photovoltaic cell assembly 1 and the state of the power grid 9, such as controlling the opening and closing of the first switch 4 and/or the second switch 5, and the like.

For example, the output of the photovoltaic detection unit 8 can be connected to the control system 7 to transmit a photovoltaic detection signal into the control system 7 in order to make a phase according to the state of the photovoltaic module 1 The control action should be.

Preferably, the control system 7 is connected to the converter unit 3 in order to detect and control the converter unit 3. For example, the control system 7 acquires the detection signal of the converter unit 3 for determining the state of the voltage, current, etc. of the photovoltaic cell module 1 and the state of the grid 9, and then issuing a corresponding control signal for controlling the converter unit 3 so that The voltage is adjusted, the harmonic components are reduced, and the like, so that the voltage of the DC bus of the converter unit 3 meets the requirements.

Further, the control system 7 can determine whether the photovoltaic cell module 1 satisfies the power generation condition and whether the power generation amount can meet the operation requirement of the air conditioning unit 2 or the like according to the detection signal from the converter unit 3, so as to timely control the first switch 4 Opening and closing.

Preferably, the first end (left end in the figure) of the current conversion unit 3 is directly connected to its DC bus. Therefore, the air conditioning unit 2 is powered on the DC bus. When the first switch 4 is closed, the DC take-off branch 61 of the switching power supply 6 is also equivalent to taking power on the DC bus.

Figure 2 shows a schematic diagram of a preferred embodiment of the switching power supply 6 of the present invention. Preferably, the switching power supply 6 comprises a transformer 64, and the DC power take-off branch 61 and the AC power take-off branch 62 of the switching power supply 6 are connected to a common power bus 63, which is connected to the primary side of the transformer 64. The secondary side of the transformer 64 is used to output the control power.

As shown in FIG. 2, diodes are respectively connected to the two power take-off paths of the DC power take-off branch 61 to ensure the polarity of the DC power take-off branch 61, so as to avoid voltage caused by the reverse connection of the photovoltaic module 1 Reverse damage to subsequent control systems and the like.

As shown in FIG. 2, the AC power take-off branch 62 includes a full-wave rectifier bridge composed of four diodes, and the two output ends of the full-wave rectifier bridge are connected to the power bus 63 according to the polarity, thereby ensuring that it is taken from the grid side. Electricity meets the polarity requirements. When the power grid 9 is a three-phase power grid, the AC power take-off branch 62 can take power between any two phases.

Preferably, as shown in the structure in the dashed box in FIG. 1, the converter unit 3 comprises a three-phase bridge circuit, the three-phase bridge circuit comprises a three-phase bridge arm, each phase bridge arm comprising an anti-parallel diode Two power switching devices respectively constitute an upper arm and a lower arm of the phase bridge arm, and a connection point between an upper arm and a lower arm of each phase bridge arm is used to connect the second switch 5.

Preferably, as shown in FIG. 1, the power grid 9 is a three-phase power grid, and thus the photovoltaic system is a three-phase photovoltaic system, and the three-phase lines of the three-phase power grid are respectively connected to the upper arm and the lower arm of each phase bridge arm via the second switch 5 The connection point between the arms.

Alternatively, the grid 9 can also be a single-phase grid. In this case, the photovoltaic system is a single-phase photovoltaic system, and the two lines of the single-phase grid can be connected to any two phases of the converter unit 3 via the second switch 5 respectively. The junction between the upper and lower arms of the bridge arm.

Based on the above work, another aspect of the present invention provides a control method of the photovoltaic system described above, comprising the steps of: controlling the first switch according to a state of the photovoltaic cell component 1 and/or a state of the power grid 9. 4 and the opening and closing state of the second switch 5.

By controlling the opening and closing states of the first switch 4 and the second switch 5, it is possible to conveniently achieve the goals of reducing system standby power consumption, improving system safety and reliability, and prolonging the service life of the photovoltaic cell module.

The determination of the state of the photovoltaic cell module 1 and the determination of the state of the grid can be made by the control system 7 based on the detection signal from the converter unit 3.

Preferably, the control method further includes controlling the first switch 4 to be turned off when the photovoltaic cell assembly 1 does not satisfy the power generation condition. This protects the photovoltaic cell module 1 from the grid side voltage and ensures the lifetime of the photovoltaic cell module 1.

Further, in the case where the first switch 4 is turned off, the control strategy for the second switch 5 is determined according to whether the air conditioning unit 2 is operating.

Specifically, in a case where the air conditioning unit 2 is not operating, the second switch 5 is controlled to be turned off. That is, the connection between the photovoltaic cell module 1 and the converter unit 3 and the connection between the converter unit 3 and the grid 9 are simultaneously disconnected. At this time, the photovoltaic system is in a standby state, the DC bus is not charged, and the switching power supply 6 Take power from the AC grid 9 to ensure that the system's various detection functions are normal. This control method can reduce the standby power consumption of the system and increase the security of the system.

Alternatively, the second switch 5 is controlled to be closed when the air conditioning unit 2 needs to be operated. That is, while disconnecting the connection between the photovoltaic cell module 1 and the converter unit 3, the connection between the converter unit 3 and the grid 9 is maintained, so that the air conditioner unit 2 is powered by the grid 9, and the air conditioner unit can be ensured. normal operation.

Preferably, the control method further comprises: when the photovoltaic cell assembly 1 satisfies a power generation condition, controlling the first switch 4 to be closed while controlling the second switch 5 to be closed unless the power grid 9 is powered off.

In the case of controlling the closing of the first switch 4, the operating modes of the entire system include the following two types:

Mode 1: The air conditioning unit 2 does not operate, or the air conditioning unit 2 needs to operate and the photovoltaic power The power generation amount of the pool assembly 1 is greater than the power consumption of the air conditioning unit 2, and at this time, controlling the second switch 5 to close, the excess electric energy emitted by the photovoltaic cell assembly 1 can be fed to the power grid. In this mode, mainly the photovoltaic cell module 1 supplies power to the air conditioning unit.

Mode 2: The air conditioning unit 2 needs to be operated but the power generation amount of the photovoltaic battery unit 1 cannot meet the energy consumption of the air conditioning unit 2. At this time, the second switch 5 is controlled to be closed, and the power can be taken from the power grid 9 to maintain the air conditioning unit 2 Running. In this mode, the air conditioner unit is powered by the grid 9 and the photovoltaic unit 1 together.

Preferably, the control method further comprises: when the power grid 9 is powered off, when the air conditioning unit 2 needs to operate and the power generation amount of the photovoltaic battery assembly 1 is greater than the energy consumption of the air conditioning unit 2, the first switch 4 is controlled to be closed. At the same time, the second switch 5 is controlled to be disconnected. At this time, the photovoltaic unit is used to supply power to the air conditioning unit, and at the same time, the connection between the system and the power grid 9 is disconnected to avoid impact on the power grid 9 or to endanger the personal safety of the personnel who inspect the power grid 9.

In summary, the photovoltaic system and the control method thereof of the present invention have a dual power take-off mode, and correspondingly set a DC side switch (first switch) and an AC side switch (second switch), corresponding to corresponding detection and control Logic, at least has the following beneficial effects:

(1) can reduce the standby loss of the photovoltaic system;

(2) can increase the safety and reliability of the photovoltaic system;

(3) The service life of photovoltaic modules can be guaranteed.

It will be readily understood by those skilled in the art that the above various preferred embodiments can be freely combined and superimposed without conflict.

The above-described embodiments are to be considered as illustrative and not restrictive. Modifications or substitutions are intended to be included within the scope of the appended claims.

Claims

A photovoltaic system includes a photovoltaic cell assembly, a current conversion unit, a first switch, a second switch, and a switching power supply, wherein

The output end of the photovoltaic cell assembly is connected to the first end of the converter unit via a first switch,

The second end of the converter unit is connected to the power grid via the second switch.

The switching power supply has a DC power take-off branch and an AC power take-off branch, wherein a power take-off point of the DC power take-off branch is between the photovoltaic cell component and the first switch, and the AC power is taken The power take-off point of the branch is located between the second switch and the grid.
The photovoltaic system of claim 1 further comprising a photovoltaic detection unit disposed between the photovoltaic module and the first switch for detecting a state of the photovoltaic module.
A photovoltaic system according to claim 1, further comprising a control system electrically powered by the control output of said switching power supply and for outputting a control signal for controlling said first switch and said second switch .
The photovoltaic system of claim 3 wherein said control system is coupled to said converter unit for detecting and controlling said converter unit.
The photovoltaic system of claim 1 wherein the first end of the converter unit is directly coupled to its DC bus.
The photovoltaic system according to claim 1, wherein the switching power supply comprises a transformer, and the DC power take-off branch and the AC power take-off branch of the switching power supply are connected to a common power bus, and the power bus is connected to the original of the transformer. The control power outputted by the switching power supply is output by the secondary side of the transformer.
A photovoltaic system according to any one of claims 1 to 6, wherein said converter unit comprises a three-phase bridge circuit, the three-phase bridge circuit comprising three-phase bridge arms, each phase bridge arm comprising two power switching devices having anti-parallel diodes, the two power switching devices respectively forming an upper arm of the phase-bridge arm And a lower arm, a connection point between the upper arm and the lower arm of each phase bridge arm for connecting the second switch.
The photovoltaic system according to claim 7, wherein the photovoltaic system is a three-phase photovoltaic system, and the three-phase lines of the three-phase power grid are respectively connected to the connection point between the upper arm and the lower arm of each phase bridge arm via the second switch ;

Alternatively, the photovoltaic system is a single-phase photovoltaic system, and the two lines of the single-phase power grid are respectively connected to the connection point between the upper arm and the lower arm of any two-phase bridge arm via the second switch.
A photovoltaic system according to any one of claims 1 to 6, further comprising an electrical device connected to the first end of the converter unit.
The photovoltaic system of claim 9 wherein said powered device is an air conditioning unit.
A method of controlling a photovoltaic system according to any one of claims 1 to 10, comprising the step of controlling the opening and closing state of the first switch and the second switch according to a state of the photovoltaic cell assembly and/or a state of the power grid .
The control method according to claim 11, wherein said first switch is turned off when said photovoltaic cell assembly does not satisfy a power generation condition.
The control method according to claim 12, wherein the second switch is turned off when the powered device of the photovoltaic system is not operating;

Alternatively, the second switch is controlled to close when the electrical equipment of the photovoltaic system needs to be operated.
The control method according to claim 11, wherein when said photovoltaic cell module is full In the case of a sufficient power generation condition, the first switch is controlled to be closed while the second switch is controlled to be closed.
The control method according to claim 11, wherein when the power grid is powered off, when the power consumption device of the photovoltaic system needs to be operated and the power generation amount of the photovoltaic battery module is greater than the power consumption of the power consumption device, control The first switch is closed while controlling the second switch to open.