CN202261081U - Solar photovoltaic grid-connected and grid-disconnected hybrid power generating system - Google Patents

Abstract

The utility model relates to a solar photovoltaic grid-connected and off-grid hybrid power generation system, comprising: a controller, a solar cell square array, a battery pack, a DC emergency load, a grid-connected inverter, etc., and is characterized in that the controller includes: an operating mode Control unit (201), maximum power point tracker, medium-voltage DC bus (202), DC step-down converter, low-voltage DC bus (203), charge and discharge controller, emergency output switching relay J1, etc., solar cell square array output Most of the DC power is converted into AC power through the grid-connected inverter and sent to the public distribution network; a small part is provided to the DC emergency load and battery pack through the DC step-down converter and the low-voltage DC bus (203). When the voltage of the low-voltage direct-current bus (203) is outside the normal range, the battery pack supplies energy to the direct-current emergency load. The grid-connected and off-grid hybrid power generation system improves system efficiency and annual power generation time, and has a good application prospect.

Description

Solar photovoltaic grid-connected and off-grid hybrid power generation system

technical field

The invention relates to an application of solar photovoltaic power generation, in particular to a hybrid photovoltaic power generation system capable of mainly generating electricity connected to the grid and simultaneously generating electricity off the grid. the

Background technique

Solar photovoltaic power generation can replace and reduce the use of limited and non-renewable coal, oil, natural gas and other primary fossil energy and the secondary energy converted from it. Promoting the application of solar photovoltaic power generation is of great significance to reducing the consumption of fossil energy and optimizing the energy structure. the

Solar photovoltaic power generation does not emit pollutants that damage the atmosphere and the ecological environment, and is a clean and green energy that is in harmony with the ecological environment on which human beings depend. Promoting the application of solar photovoltaic power generation can reduce the emission of pollutants such as CO2, SO2 and particulate matter, and play a great role in reducing air pollution and protecting the ecological environment. the

At present, known solar photovoltaic power generation systems can be divided into grid-connected power generation systems and off-grid power generation systems according to different operating modes of the systems. the

The solar photovoltaic grid-connected power generation system consists of a solar cell array, a grid-connected inverter and a public distribution network. The solar energy is converted into DC power through the solar cell array, and then the DC power is converted into AC power through the grid-connected inverter, and its current has the same frequency and phase as the public distribution network voltage. The solar photovoltaic grid-connected power generation system can work in areas with public grids, and it does not require energy storage devices. the

The solar photovoltaic off-grid power generation system generally consists of a solar cell array, a DC/DC converter, a charge and discharge controller, a battery pack, and an off-grid inverter. The solar cell square array converts the received solar energy into DC electric energy, realizes maximum power point tracking through the control of the DC/DC converter, and then stores the output electric energy of the photovoltaic array in the battery pack, and the battery pack transfers the energy through the charge and discharge controller. Provided to DC loads or transformed into AC power by DC/AC inverters to supply AC loads. The solar photovoltaic off-grid power generation system is an electricity solution that can adapt to areas without electricity. the

However, for the grid-connected power generation system, when the distribution network fails, in order to prevent the island effect, the grid-connected inverter will not be allowed to work, and the convertible electric energy of the solar cell array will not be used; while for off-grid In the power generation system, when the battery pack is fully charged and there is no electrical load, the solar cell array will not be able to generate electricity because there is no output load, and the convertible electric energy of the solar cell array will not be utilized.

Aiming at the shortcomings of single solar photovoltaic grid-connected power generation system and off-grid power generation system, in order to improve the utilization rate of solar cell arrays under various complex operating conditions, the invention of "solar photovoltaic grid-connected and off-grid hybrid power generation system" is disclosed. the

The solar photovoltaic grid-connected and off-grid hybrid power generation system can be applied to solar grid-connected power generation systems integrated with buildings, household solar roof power generation systems, etc. the

Contents of the invention

The purpose of the present invention is to design a solar photovoltaic grid-connected and off-grid hybrid power generation system in order to make full use of the power generation capacity of the solar cell array and improve the reliability of power supply for users' emergency loads. the

The solar photovoltaic grid-connected and off-grid hybrid power generation system is composed of a solar cell array, a controller, a battery pack, a DC emergency load, a grid-connected inverter, and a public distribution network. The output terminal of the solar cell square array is connected to the input terminal of the controller. The controller has three outputs, the first output of which is connected to the DC emergency load; the second output of which is connected to the battery pack; The inverter is connected to the public distribution network, and the solar photovoltaic grid-connected and off-grid hybrid power generation system is characterized by a controller, including: an operation mode control unit (201), an anti-current backflow diode D3, a maximum power point tracker, and a medium-voltage DC bus ( 202), DC step-down converter, low-voltage DC bus (203), charge and discharge controller, emergency output switching relay J1, the input end of the controller is connected to the input end of the maximum power point tracker through the anti-current backflow diode D3, said The output terminal of the maximum power point tracker is connected to the medium-voltage DC bus (202), and the medium-voltage DC bus (202) is connected to the third output of the controller; The device is connected to the low-voltage DC bus (203), and the low-voltage DC bus (203) is connected to the first output of the controller through the normally open contact of the emergency output switching relay J1, and the low-voltage DC bus (203) is also connected to the charging and discharging control The input of the charge and discharge controller has two outputs, the first output of which is connected to the first output of the controller through the normally closed contact of the emergency output switching relay J1, and the second output of which is connected to the first output of the controller Two outputs. The solar cell array converts the received solar energy into DC power, and realizes its maximum power point tracking by controlling the DC/DC converter in the controller. Most of the DC power is provided to the input of the grid-connected inverter through the medium-voltage DC bus in the controller, and the DC power is converted into AC power that meets the grid-connected conditions and sent to the public distribution network through the grid-connected inverter; Part of the DC power is provided to the low-voltage DC bus (203) through the medium-voltage DC bus (202) and the DC step-down converter in the controller, and the low-voltage DC bus (203) provides part of it to the DC emergency load, and the other part is stored in the battery group. When the voltage of the low-voltage DC bus (203) in the controller is outside the normal working range, the battery pack supplies energy to the DC emergency load through the charging and discharging controller in the controller, so as to always ensure reliable power supply of the DC emergency load. the

The solar photovoltaic grid-connected and off-grid hybrid power generation system has the function of grid-connected and off-grid hybrid power generation, mainly for grid-connected power generation, and can also generate off-grid power generation. Even when the distribution network fails, in order to prevent the island effect, the grid-connected inverter is not allowed to work, but the DC power converted by the solar cell array can still pass through the medium-voltage DC bus and DC step-down conversion in the controller. The inverter is used by the DC emergency load and the battery pack, which improves the utilization rate of the solar battery and ensures the reliable power supply of the DC emergency load. the

The solar photovoltaic grid-connected and off-grid hybrid power generation system reduces the power conversion link and improves system efficiency; the solar photovoltaic grid-connected and off-grid hybrid power generation system effectively improves the system's annual power generation time and increases the system's annual power generation. The solar photovoltaic grid-connected and off-grid hybrid power generation system effectively utilizes the clean energy provided by the solar cell array under various complex operating conditions, and has a good application prospect. the

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. the

Figure 1 is a schematic diagram of a solar photovoltaic grid-connected and off-grid hybrid power generation system. the

Figure 2 is a schematic diagram of a controller in a solar photovoltaic grid-connected and off-grid hybrid power generation system. the

Fig. 3 is a relay control flowchart of the operation mode control unit (201) in the controller. the

Detailed ways

1. Circuit topology of solar photovoltaic grid-connected and off-grid hybrid power generation system

In Fig. 1, the composition and connection of the solar photovoltaic grid-connected and off-grid hybrid power generation system are described. The output terminal of the solar cell square array is connected to the input terminal of the controller, and the controller has three outputs, the first output of which is connected to a DC emergency load (such as power LED lighting load, mobile electrical charger, etc.); The output is connected to the battery pack; its third output is connected to the input of the grid-connected inverter, and the output of the grid-connected inverter is connected to the public distribution network. the

In Fig. 2, the composition and internal connection of the key component-controller in the solar photovoltaic grid-connected and off-grid hybrid power generation system are described. the

The composition of the controller is: operation mode control unit, anti-current backflow diode D3, maximum power point tracker, medium voltage DC bus (202), DC step-down converter, low voltage DC bus (203), charge and discharge controller, emergency Output switching relay J1. the

The internal connection of the controller is: the input end of the controller is connected to the input end of the maximum power point tracker through the anti-current backflow diode D3, and the output end of the maximum power point tracker is connected to the medium voltage DC bus (202), and the middle voltage The high-voltage DC bus (202) is connected to the third output of the controller; the medium-voltage DC bus (202) is also connected to the low-voltage DC bus (203) through a DC step-down converter, and the low-voltage DC bus (203) is connected to the emergency output The normally open contact of the switching relay J1 is connected to the first output of the controller, and the low-voltage DC bus (203) is also connected to the input of the charge-discharge controller. The charge-discharge controller has two outputs, the first output of which is The normally closed contact of the emergency output switching relay J1 is connected to the first output of the controller, and its second output is connected to the second output of the controller. the

In Fig. 2, the composition of the operating mode control unit (201) in the controller is also described. It includes: a solar cell square array voltage sampling circuit, a low-voltage direct current bus (203) voltage sampling circuit and a microcontroller MCU. the

The rated value of the voltage of the medium-voltage DC bus (202) is adapted to the input of the grid-connected inverter. the

The rated value of the voltage of the low-voltage DC bus (203) is adapted to the rated value of the DC emergency load. the

The DC step-down converter adopts a BUCK DC conversion circuit, and the duty cycle of the switching device is determined according to the ratio of the voltage of the low-voltage DC bus (203) to the rated value of the voltage of the medium-voltage DC bus (202). In the DC step-down converter During the working period, the duty cycle of the switching device is always fixed, and the output and input DC voltage transformation ratio is also constant. the

The charge and discharge controller uses power MOSFET as the main switching device, microcontroller MCU as the control circuit, controls the charging peak current, fully disconnects the charging circuit and undervoltage disconnects the discharging circuit. the

The grid-connected inverter uses a full-bridge inverter circuit as the main circuit, and a digital signal processor DSP as the control circuit. It has an output power automatic adjustment function during operation, so that the medium-voltage DC bus voltage is within the working range. the

2. Energy management of solar photovoltaic grid-connected and off-grid hybrid power generation systems

In order to achieve the goal of making full use of the electric energy converted by the solar cell array, the energy management strategy of the solar photovoltaic grid-connected and off-grid hybrid power generation system is a multi-objective coordinated control strategy, which consists of the operation mode control unit, the maximum power point tracker, the charging and discharging The controller and the grid-connected inverter are jointly completed, and the specific implementation method is as follows:

The control goal of the maximum power point tracker is to automatically realize the maximum power output of the solar cell array when the solar radiation intensity, ambient temperature, and load conditions change;

The charge and discharge controller controls the charging peak current, disconnects the charging circuit when it is fully charged and disconnects the discharging circuit when it is undervoltage;

The grid-connected inverter has an automatic output power adjustment function during operation, so that the voltage of the medium-voltage DC bus (202) is within the working range;

The control target of the operation mode control unit (201) is to simultaneously send the DC power converted by the solar cell square array to the grid-connected inverter and to the low-voltage DC bus (203) through the step-down converter, and then to the low-voltage DC bus (203). For DC emergency loads and batteries. Under the condition of not having grid-connected operation, the solar photovoltaic grid-connected and off-grid hybrid power generation system can still provide clean energy for DC emergency loads. the

The energy management strategy of the operating mode control unit (201) in the solar photovoltaic grid-connected and off-grid hybrid power generation system is illustrated in FIG. 3 . the

The operation mode control unit (201) detects the low-voltage DC bus voltage Vdc, calculates the average value within a certain period of time, and according to the average value, drives the switch tube S1 in a level mode to determine the energization state of the coil of the relay J1, and controls the relay J1 The state of the contacts determines the source of the emergency output. the

When the low-voltage DC bus (203) voltage Vdc_min<Vdc<Vdc_max, the S1 terminal of the operation mode control unit (201) outputs a high level, the normally open contact of the emergency output switching relay J1 is closed, the normally closed contact is opened, and the emergency The output electric energy comes from the low-voltage DC bus (203), that is, the real-time power generation from the solar cell array; when the voltage of the low-voltage DC bus (203) Vdc<Vdc_min or Vdc>Vdc_max, the S1 terminal output of the operation mode control unit (201) is low Level, the normally open contact of the emergency output switching relay J1 is open, the normally closed contact is closed, and the electric energy of the emergency output comes from the output of the charge and discharge controller, that is, from the energy storage of the battery pack. the

Claims (8)

1. a solar photovoltaic grid-connection is from the net hybrid power system; It is characterized in that: comprising: controller, solar cell array, batteries, direct current emergency load, combining inverter, public power distribution network; The input of the output termination controller of solar cell array; Said controller has three tunnel outputs, and its first via output connects the direct current emergency load; Its second tunnel output connects batteries; Its Third Road output connects public power distribution network through combining inverter; Solar photovoltaic grid-connection is characterised in that controller from the net hybrid power system; Comprise: operational mode control unit (201), anti-electric current pour in down a chimney diode D3, MPPT maximum power point tracking device, middle straightening stream bus (202), DC decompression converter, low-voltage direct bus (203), charging-discharging controller, emergent output transfer relay J1; The input of controller pours in down a chimney the input that diode D3 connects the MPPT maximum power point tracking device through anti-electric current; Straightening stream bus (202) in the output termination of said MPPT maximum power point tracking device, said middle straightening stream bus (202) connects the Third Road output of controller; Straightening stream bus (202) also connects low-voltage direct bus (203) through the DC decompression converter in said; Said low-voltage direct bus (203) connects the first via output of controller through the normally opened contact of emergent output transfer relay J1; Said low-voltage direct bus (203) also connects the input of charging-discharging controller; Said charging-discharging controller has two tunnel outputs; Its first via output is exported through the first via that the emergent normally-closed contact of exporting transfer relay J1 connects controller, and its second tunnel output connects the second tunnel output of controller.

2. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system, and its characteristic also is operational mode control unit (201), comprising: solar cell array voltage sampling circuit, low-voltage direct busbar voltage sample circuit and microcontroller MCU.

3. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system; Its characteristic also is operational mode control unit (201), when low-voltage direct busbar voltage Vdc_min＜Vdc＜Vdc_max, and the S1 of control unit (201) end output high level; The normally opened contact of emergent output transfer relay J1 is closed; Normally-closed contact breaks off, and the electric energy of emergent output is from the low-voltage direct bus, promptly from the real-time generating of solar cell array; When low-voltage direct busbar voltage Vdc＜Vdc_min or Vdc＞Vdc_max; The S1 end output low level of control unit (201); The normally opened contact of emergent output transfer relay J1 breaks off; Normally-closed contact is closed, and the electric energy of emergent output is from the output of charging-discharging controller, promptly from the energy storage of batteries.

4. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system, and the rated value of straightening stream bus (202) voltage and the input of combining inverter adapted during its characteristic also was.

5. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system, and its characteristic is that also the rated value of low-voltage direct busbar voltage (203) and the rated value of direct current emergency load adapt.

6. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system; Its characteristic also is DC decompression converter using BUCK DC transfer circuit; Ratio according to low-voltage direct bus (203) voltage and middle straightening stream bus (202) voltage rating; Confirm the duty ratio of its switching device, fix all the time that its output input direct voltage no-load voltage ratio also is constant in the duty ratio of said its switching device of DC decompression converter duration of work.

7. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system; Its characteristic is that also it is main switching device that charging-discharging controller uses power MOSFET; Microcontroller MCU is a control circuit; Control charging peak current breaks off charge circuit and breaks off discharge loop when under-voltage when being full of.

8. solar photovoltaic grid-connection as claimed in claim 1 is from the net hybrid power system; Its characteristic is that also combining inverter uses full-bridge inverter circuit to be main circuit; Digital signal processor DSP is a control circuit; Run duration has the automatic regulatory function of power output, and straightening stream bus (202) voltage is in working range in making.

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