CN102364810A - A control method and controller for multi-stage absorption of solar photovoltaic cell electric energy - Google Patents

Abstract

The invention discloses a control method and a controller, which can efficiently utilize electric energy generated by a solar photovoltaic cell in different illumination weathers. A system consists of the solar photovoltaic cell, a singlechip, a plurality of stages of storage batterybatteries, a plurality of DC-DC (Direct Current) boosting charging circuits, a voltage current detection circuit, a relay, a driving circuit of the relay and a PWM (Pulse-Width Modulation) photoelectrical coupling and pulse output circuit. The singlechip is driven by software; an output voltage and an output current of the solar photovoltaic cell and a voltage of each stage of storage battery, which are input into IO (Input Output) ports, are detected; an electric power generated by the solar photovoltaic cell and the electric quantity storage condition of each stage of storage battery are obtained according to the voltages and the current; and the relay is controlled to switch the circuits and a PWM is controlled to output a signal to realize various working conditions of adsorption and transmission of electric energy, so that the circuits are controlled to efficiently utilize the electric power generated by the solar photovoltaic cell in all weathers. Few cheap devices are adopted. The technical barriers of utilization of electric energy of the solar photovoltaic cell under different illumination conditions and application of MPPT (Maximum Power Point Tracking) are overcome. The control method and the controller have high cost performance and have wide application prospect.

Description

A control method and controller for multi-stage absorption of solar photovoltaic cell electric energy

technical field

The invention belongs to the technical field of solar energy utilization, and relates to a method for controlling electric energy of multi-stage absorption of solar photovoltaic cells and a controller thereof.

technical background

my country's solar energy resources are very rich, and the potential for development and utilization is very large. More than two-thirds of the country's annual sunshine is more than 2,000 hours, and the annual average radiation is about 5,900 MJ/square meter, which belongs to the area with good solar energy utilization conditions. According to the "Renewable Energy Medium and Long-term Development Plan", by 2020, my country will strive to make the installed capacity of solar power generation reach 1.8GW (million kilowatts), and by 2050 it will reach 600GW (million kilowatts). According to the prediction of China Electric Power Academy, by 2050, China's installed capacity of renewable energy will account for 25% of the country's installed capacity of electricity, of which photovoltaic power generation installed capacity will account for 5%. At present, my country's installed capacity of solar power generation is only 65,000 kilowatts. In the next 15 years, the compound growth rate of my country's solar energy installed capacity will be as high as 25%, and the total investment in solar power generation will be 95 billion yuan. The development space of the solar power generation industry is huge, and the use of solar power generation in my country is still in its infancy.

At present, the technical difficulties in using solar photovoltaic power generation are mainly: 1) the efficiency of solar photovoltaic cells is low; . As a result, the application cost is very high (the electricity price is very high), and the power supply is unreliable, so the application is limited. The first two difficulties are mainly solved by the development of materials and battery technology. The present invention does not involve these technologies. The third difficulty is mainly solved by circuit control technology. It solves how to maximize the efficiency under the existing conditions. Make good use of solar photovoltaic power generation. In order to use solar photovoltaic power generation, people usually use solar photovoltaic cells to charge a battery with a certain capacity and voltage, and then invert the DC power of the battery into AC or go online or directly use it for the load. Since the electric power of solar photovoltaic cells will change with the light, in order to efficiently utilize the electric energy of solar photovoltaic cells under all-weather light, two problems need to be solved. One is to perform MPPT (Maximum Power Point Tracking) when the light intensity is high Tracking); the second is when the light is lower than a certain intensity and the aforementioned utilization method cannot be completed, the utilization of solar photovoltaic cell electric energy. Both of these problems will depend on control technology to solve.

Contents of the invention

The technical problem to be solved by the present invention is to provide a kind of control method and controller that can realize the utilization even when the power of solar photovoltaic power generation is low, and can effectively perform MPPT when the power generation power is high, and is easy to implement, low in cost, Complete tasks efficiently.

Technical solution of the present invention is as follows:

A multi-stage controller for absorbing electric energy of solar photovoltaic cells is characterized in that a solar photovoltaic cell, a single-chip microcomputer, a 3-stage storage battery, 2 DC-DC boost charging circuits, a voltage and current detection circuit, a relay switching circuit, a PWM photoelectric Composed of coupling and pulse output circuits; the 4 IO ports of the single-chip microcomputer are used as AD conversion input ports, and the 4 IO ports respectively detect the voltage Uo of the solar photovoltaic cell, the output current Io of the solar photovoltaic cell, and the voltage on the battery BT2 and BT3;

The 2 IO ports of the microcontroller control 2 channels of PWM signals (PWM1, PWM2), which respectively control the switching tubes of the two DC-DC boost charging circuits through the photoelectric coupling and pulse output circuits to boost the battery BT2 and BT3 Charge and perform MPPT;

The 2 IO ports of the microcontroller are connected to 2 photocouplers to control the two relays J1 and J2 to switch the boost circuit, so as to realize the transmission of electric power from the solar photovoltaic cell to the storage battery under different light intensities, and effectively absorb the power of the solar photovoltaic cell. Electric power, or transmission from the front-stage battery to the rear-stage battery.

Described single-chip microcomputer is ATMega AVR series single-chip microcomputer.

A control method for multi-level absorption of solar photovoltaic cell electric energy, using the above-mentioned multi-level absorption of solar photovoltaic cell electric energy controller, its working state is as follows:

State 1: When the circuit starts, the solar photovoltaic battery should continuously charge the storage battery BT1. When its voltage reaches 2.7 volts or more, the single-chip microcomputer starts to work, and the single-chip microcomputer controls the solar photovoltaic battery voltage U _O , current I _O , and the voltage of the storage battery BT2 and BT3 to test;

State 2: When the battery BT3 loses power, the single-chip microcomputer starts PWM2 output, starts the DC-DC boost charging circuit, tries to charge the battery BT3 through the solar photovoltaic cell, and monitors the output power change of the solar photovoltaic cell at the same time. If the electric power increases, then Carry out MPPT control to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to directly charge the battery BT3, and then enter the state 3;

State 3: When the battery BT3 is running low, check whether the battery BT2 is running low. If the battery BT2 is not running low, the microcontroller starts the relay J2, and starts PWM2 with the maximum pulse width to charge the battery BT3 through the battery BT2, so that the electric power is transferred from the battery BT2 to the battery. The battery BT3 transmits; when the battery BT2 loses power, it enters state 4;

State 4: When the battery BT2 loses power, start the breaker J1, start the PWM1 output, and make the DC-DC boost charging circuit work, try to charge the battery BT2 through the solar photovoltaic cell, and monitor the output power of the solar photovoltaic cell at the same time. , if the electric power increases, MPPT control is performed to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to charge the battery BT2 directly, and enters state 5;

State 5: At this time, the solar photovoltaic cell cannot charge the batteries BT2 and BT3 due to weak light and low output power, and directly charges the battery BT1 to maintain the work of core devices such as single-chip microcomputers. When both batteries BT2 and BT3 continue to lose power for a specified period of time, the single-chip microcomputer sends out a warning signal, prompting to use commercial power for charging, and the working state returns to state 1.

The above-mentioned solution is a solution for a three-stage battery, and the method of increasing the number of battery stages is as follows (see the accompanying drawing):

1. The first stage battery BT1 and the last stage battery BTn remain unchanged.

2. The added batteries are intermediate stages such as BT2 to BTn-1, and their voltage and battery capacity increase step by step.

3. For each additional intermediate storage battery, a DC-DC step-up circuit, two relay control circuits and a resistor divider circuit for detecting the voltage of the intermediate storage battery need to be installed. Occupy one MCU IO port to output PWM wave to control the DC-DC boost circuit, occupy two MCU IO ports to control two relays, and occupy one MCU AD conversion input terminal to detect the intermediate battery voltage.

4. Increasing the maximum number of intermediate storage battery stages is limited by the number of AD conversion input terminals and the number of IO ports of the single-chip microcomputer.

The invention includes a solar photovoltaic cell, a single-chip microcomputer, multi-stage batteries, multiple DC-DC boost charging circuits, voltage and current detection circuits, relay switching circuits, PWM photoelectric coupling and pulse output circuits and their connecting lines (see the manual Figure), programming flow chart, and application examples. In the present invention, the efficient utilization control method for solar photovoltaic cells is embodied in the use of multiple storage batteries with different voltages. When the solar photovoltaic cells change in intensity of light, different charging circuits are started to absorb the power of the solar photovoltaic cells. At the same time, MPPT tracking is also used during charging to make full use of photovoltaic power. The capacity and voltage of the last-stage battery are the largest, and it supplies power to the load, while the capacity and voltage of the intermediate batteries decrease step by step, and they absorb photovoltaic power when the photovoltaic power is low. And can provide charging power step by step backward, that is, relay charging can be realized. Therefore it is similar to the water supply method of lifting water step by step.

Beneficial effect:

The invention adopts multi-stage accumulators and a relatively simple circuit to solve the problem of efficiently utilizing the electric energy of solar photovoltaic cells. It has the characteristics of convenient and reliable application, and is easy to program and implement. It is especially suitable for solar energy utilization of electric bicycles, reducing dependence on mains power and increasing mileage. Therefore, implementing the present invention has great cleaning and environmental protection significance, and has very wide application prospects.

Description of drawings

Fig. 1 is a schematic diagram of the energy flow of solar photovoltaic cells and the electric energy between the storage batteries of all levels in the present invention. to the last stage storage battery; Fig. 2 is the control circuit diagram of electric energy absorption composed of 3-stage storage batteries of the present invention, among which BT0 is a solar photovoltaic cell, BT1 and BT2 are intermediate storage batteries, and BT3 is the last storage storage battery, which finally sends power supply to the load.

Fig. 3, Fig. 4, Fig. 5 are software design flow charts, Fig. 3 is a main program flow chart of the single-chip microcomputer mainframe, Fig. 4, Fig. 5 are work flow charts of subroutines for absorbing electric energy of batteries at all levels respectively.

Detailed ways

The technical scheme of the present invention and working process will be further described below in conjunction with accompanying drawing with specific embodiment, but protection scope of the present invention is not limited to this:

Example 1

Referring to Fig. 2, a multi-stage controller for absorbing electric energy of solar photovoltaic cells is characterized in that a solar photovoltaic cell, a single-chip microcomputer, a 3-stage storage battery, 2 DC-DC boost charging circuits, a voltage and current detection circuit, and a relay switching circuit, PWM photoelectric coupling and pulse output circuit; the 4 IO ports of the single chip microcomputer are used as AD conversion input ports, and the 4 IO ports respectively detect the voltage Uo of the solar photovoltaic cell, the output current Io of the solar photovoltaic cell, and the voltage on the battery BT2 and BT3 ;

The 2 IO ports of the microcontroller generate 2 PWM signals (PWM1, PWM2), which respectively control the MOS switches of the two DC-DC boost charging circuits through the photocoupling and pulse output circuits to boost the batteries BT2 and BT3. Voltage charging, and MPPT;

The 2 IO ports of the MCU are connected to 2 photocouplers to control the two relays J1 and J2 to switch the boost circuit so that under different sunlight, the electric power can be transmitted from the solar photovoltaic cell to the battery, effectively absorbing solar photovoltaic Battery electric power, or transmitted from the front battery to the rear battery.

Described single-chip microcomputer is ATMega AVR series single-chip microcomputer.

A control method for multi-stage absorption of solar photovoltaic cell electric energy, using the aforementioned multi-stage solar photovoltaic cell electric energy absorption controller, its working state is as follows:

State 1: When the circuit starts, the solar photovoltaic battery should continue to charge the battery BT1, let its voltage reach above 2.7 volts, and make the single-chip microcomputer start to work. to test;

State 2: When the battery BT3 loses power, the single-chip microcomputer starts PWM2 output, starts the DC-DC boost charging circuit, tries to charge the battery BT3 through the solar photovoltaic cell, and monitors the output power change of the solar photovoltaic cell at the same time. If the electric power increases, then Carry out MPPT control to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to directly charge the battery BT3, and then enter the state 3;

State 3: When the battery BT3 is in power loss, check whether the battery BT2 is in power loss. If the battery BT2 is not in power loss, the single-chip microcomputer starts the relay J2, and starts PWM2 with the maximum pulse width, and charges the battery BT3 through the battery BT2 to realize the electric power from the battery BT2. Send to BT3; when the battery BT2 loses power, enter state 4;

State 4: When the battery BT2 loses power, start the relay J1 and start the PWM1 output to make the DC-DC boost charging circuit work, try to charge the battery BT2 through the solar photovoltaic cell, and monitor the output power of the solar photovoltaic cell at the same time. If the electric power increases, perform MPPT control to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to charge the battery BT2 directly, and enters state 5;

State 5: At this time, the solar photovoltaic cell cannot charge the battery BT2 and BT3 due to weak light and low output power. It can directly charge and use the battery BT1 to maintain the work of core devices such as the single-chip microcomputer. The batteries BT2 and BT3 are both If the power loss continues for a specified period of time, the microcontroller will send out a warning signal, prompting to use the mains power to charge, and the working state will return to state 1.

1. The main program

The operation process of the main program of the single-chip microcomputer shown in Figure 2 has been running after the system starts.

2. Subroutine

The storage batteries at all levels absorb electric energy and operate according to the flow shown in Figure 3 and Figure 4. Among them, Figure 4 is the working process of the last level battery, and Figure 3 is the working process of the second level battery.

If there are more than 3 levels in the system, these additional storage battery processes should be operated according to Figure 4.

Practical effect:

Apply this technology to an experiment on an electric bicycle. The original 48V battery of the electric bicycle is used as the last stage battery, and a second stage battery is added in the middle. The voltages are 2.8V and 9V respectively. The nominal power of the solar photovoltaic cell is 50W, and the open circuit voltage The 21.4V short-circuit current is 3.31A. After adding the circuit of the present invention, in summer with strong sunlight, solar photovoltaic power is used to charge. On average, a single person rides a mileage of less than 20 kilometers per day, basically without charging from the mains.

Claims (2)

1. A multi-stage absorbing solar photovoltaic cell electric energy controller is characterized in that a solar photovoltaic cell, a single-chip microcomputer, 3-stage storage battery, 2 DC-DC boost charging circuits, voltage and current detection circuit, relay switching circuit, PWM Composed of photoelectric coupling and pulse output circuits; the 4 IO ports of the single chip microcomputer are used as AD conversion input ports, and the 4 IO ports respectively detect the solar photovoltaic cell voltage Uo, the output current Io of the solar photovoltaic cell, the upper voltage of the battery BT2, and the upper voltage of the battery BT3 ; The 2 IO ports of the microcontroller generate 2 PWM signals (PWM1, PWM2), which respectively control the switch tubes of the 2 DC-DC boost charging circuits through the photoelectric coupling and pulse output circuits to boost the battery BT2 and BT3 Charge and perform MPPT; The 2 IO ports of the microcontroller are connected to 2 photocouplers to control the two relays J1 and J2 to switch the boost circuit, so as to realize the transmission of electric power from the solar photovoltaic cell to the storage battery under different light intensities, and effectively absorb the power of the solar photovoltaic cell. Electric power, or transmission from the front battery to the back battery; Described single-chip microcomputer is ATMega AVR series single-chip microcomputer. 2. A control method for multi-stage absorption of solar photovoltaic cell electric energy, adopting the multi-stage absorption solar photovoltaic cell electric energy controller described in right 1, its working state is as follows: State 1: When the circuit starts, the solar photovoltaic battery should continue to charge the battery BT1, let its voltage reach above 2.7 volts, and make the single-chip microcomputer start to work. to test; State 2: When the battery BT3 loses power, the single-chip microcomputer starts PWM2 output, starts the DC-DC boost charging circuit, tries to charge the battery BT3 through the solar photovoltaic cell, and monitors the output power change of the solar photovoltaic cell at the same time. If the electric power increases, then Carry out MPPT control to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to directly charge the battery BT3, and then enter the state 3; State 3: When the battery BT3 is running low, check whether the battery BT2 is running low. If the battery BT2 is not running low, the microcontroller starts the relay J2, and starts PWM2 with the maximum pulse width to charge the battery BT3 through the battery BT2, so that the electric power is transferred from the battery BT2 to the battery. The battery BT3 transmits, when the battery BT2 loses power, it enters state 4; State 4: When the battery BT2 loses power, start the relay J1 and start the PWM1 output to make the DC-DC boost charging circuit work, try to charge the battery BT2 through the solar photovoltaic cell, and monitor the output power of the solar photovoltaic cell at the same time. , if the electric power increases, MPPT control is performed to find the maximum power output point for continuous charging; if the electric power does not increase, it is considered that the output power of the solar photovoltaic cell is not enough, and it is not suitable to charge the battery BT2 directly, and enters state 5; State 5: At this time, the solar photovoltaic cell cannot charge the batteries BT2 and BT3 due to weak light and low output power, and directly charges and utilizes the battery BT1 to maintain the work of core devices such as single-chip microcomputers. When the batteries BT2 and BT3 are both If the power loss continues for a specified period of time, the microcontroller will send out a warning signal, prompting to use the mains power to charge, and the working state will return to state 1.

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