CN202888869U - MPPT (Maximum Power Point Tracking) photovoltaic charge and discharge controller using fuzzy algorithm - Google Patents

Abstract

The utility model discloses an MPPT photovoltaic charging and discharging controller using a fuzzy algorithm, which comprises a solar cell array and a storage battery group. A controller is connected between the solar cell array and the storage battery group, and a load is connected to the controller. circuit, the controller includes an MPPT controller and a DC-DC conversion circuit, the MPPT controller is powered by the battery pack, and is used to detect the voltage and current of the solar cell array and control the DC-DC conversion circuit; the solar battery array converts a suitable voltage through the DC-DC conversion circuit to supply the storage battery pack. The utility model uses the improved MPPT algorithm of fuzzy control, and the fuzzy control method has better dynamic and steady-state performance than fuzzy control. The output power of the photovoltaic array has a maximum output power point with the increase of the output voltage.

Description

A MPPT Photovoltaic Charge-Discharge Controller Using Fuzzy Algorithm

technical field

The utility model relates to a photovoltaic charging and discharging controller of power electronic technology, in particular to an MPPT independent photovoltaic charging and discharging controller using a fuzzy algorithm. the

Background technique

With the increasingly prominent energy issues and environmental issues, solar energy as a clean energy source has been paid more and more attention. In recent years, the research and application of solar photovoltaic power generation has grown by leaps and bounds, and has become a research hotspot in new energy sources. The main factors restricting the development of solar photovoltaic power generation systems are high manufacturing costs and low conversion efficiency. the

In a photovoltaic system, it is usually required to keep the output power of the photovoltaic cell at the maximum, that is, to make the photovoltaic cell work at the maximum power point, so as to improve the conversion efficiency of the photovoltaic cell. MPPT is a process of continuous measurement and adjustment to achieve the optimum. It does not need to know the precise mathematical model of the photovoltaic array, but constantly changes the setting values of the controllable parameters during the operation, so that the current operating point gradually moves towards the peak power point. close to make the photovoltaic system operate near the peak power point. the

MPPT is essentially an optimization process. By measuring voltage, current and power, comparing the relationship between them, determining the positional relationship between the current operating point and the peak point, and then controlling the current (or voltage) to move to the current operating point and the peak power point, and finally controlling the current (or voltage) ) swing back and forth within a certain range around the peak power point. the

The MPPT controller designed by the fuzzy control algorithm can track the maximum power point of the photovoltaic array stably and efficiently; at the same time, in the case of disturbance of system parameters such as sunlight intensity and ambient temperature, it can quickly find a new operating point and keep the system stable. The simulation shows that the controllers of the perturbation and observation method and the conductance incremental method show good dynamic characteristics. The solar power generation system using the MPPT controller will increase the efficiency by 50% compared with the traditional one, but according to the actual test, due to the influence of the surrounding environment and various energy losses, the final efficiency can also be increased by 20%-30%. the

Utility model content

The purpose of the utility model is to overcome the above problems existing in the prior art, and to provide an MPPT independent photovoltaic charging and discharging controller using a fuzzy algorithm. the

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the utility model is realized through the following technical solutions:

A MPPT photovoltaic charging and discharging controller using fuzzy algorithm, including a solar cell array and a battery pack, a controller is connected between the solar cell array and the battery pack, the controller is connected to a load circuit, and the control The device includes an MPPT controller and a DC-DC conversion circuit, the MPPT controller is powered by the storage battery pack, and is used to detect the voltage and current of the solar cell array and control the DC-DC conversion circuit; the solar energy The battery array converts a suitable voltage through the DC-DC conversion circuit to supply the storage battery pack.

Further, the MPPT controller is also connected with a display module. the

The beneficial effects of the utility model are:

The utility model utilizes an improved MPPT algorithm of fuzzy control, and generates fuzzy control rules from measured data by means of artificial neural network method. Compared with the perturbation and observation method and the conductance increment method, the fuzzy control method has better dynamic and steady-state performance than the fuzzy control method. The output power of the photovoltaic array has a maximum output power point with the increase of the output voltage.

The above description is only an overview of the technical solution of the utility model. In order to understand the technical means of the utility model more clearly and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiment of the utility model with accompanying drawings. back. The specific embodiment of the utility model is given in detail by the following examples and accompanying drawings. the

Description of drawings

The drawings described here are used to provide a further understanding of the utility model and constitute a part of the application. The schematic embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute improper limitations to the utility model. In the attached picture:

Figure 1 Composition of photovoltaic power generation system;

Figure 2 MPPT control system block diagram;

Figure 3 SCM system diagram;

Figure 4 LCD1602 display interface circuit;

Figure 5 voltage detection circuit;

Figure 6 Current detection circuit;

Figure 7 AD circuit;

Figure 8 Boost conversion circuit;

Figure 9 The overall design block diagram of the system software;

Figure 10 Flowchart of the fuzzy controller.

Explanation of symbols in the figure: 1. solar cell array, 2. controller, 201. MPPT controller, 202. DC-DC conversion circuit, 203. display module, 3. battery pack, 4. load circuit. the

Detailed ways

The utility model will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. the

Referring to Fig. 1, a MPPT photovoltaic charging and discharging controller using a model lake algorithm includes a solar cell array 1 and a storage battery pack 3, a controller 2 is connected between the solar cell array 1 and the storage battery pack 3, The controller 2 is connected with a load circuit 4, and the controller 2 includes an MPPT controller 201 and a DC-DC conversion circuit 202, and the MPPT controller 201 is powered by the storage battery pack 3 for detecting the solar cell The voltage and current of the array 1 are controlled, and the DC-DC conversion circuit 202 is controlled; the solar battery array 1 converts a suitable voltage through the DC-DC conversion circuit 202 to supply the battery pack 3 . the

Further, the MPPT controller 201 is also connected with a display module 203 . the

1. Introduction to Photovoltaic System

The composition of the photovoltaic power generation system is related to the load. Both the DC load and the AC load include photovoltaic arrays, battery packs, and control circuits. The system structure is shown in Figure 1. If the load of the photovoltaic system is a DC load without an inverter circuit, it can be directly connected to the battery, and the output voltage of the battery is boosted (down) and then supplied to the load. This type of system is simple in structure and low in cost. Due to the different DC voltages of the loads, it is difficult to achieve standardization and compatibility of the system, especially for domestic electricity, where the load is mainly AC, and it is also difficult for the DC system to realize grid-connected operation. Therefore, AC photovoltaic inverter power supply is gradually replacing DC photovoltaic power supply. The main difference between the AC photovoltaic inverter power supply system and the DC photovoltaic power supply system is that an inverter is added between the load and the battery, and the inverter undertakes the function of converting DC voltage into AC voltage.

2. Control system block diagram

Photovoltaic power generation system is such a strongly nonlinear system, and it is difficult to describe photovoltaic cells with precise mathematical models. Therefore, fuzzy control methods are tried to track the maximum power point of solar cells. The independent photovoltaic system mainly uses solar photovoltaic arrays to convert solar energy into electrical energy, and uses DC-DC conversion circuits to convert appropriate voltages for DC loads. Since the output of the solar cell is unstable, in order to obtain continuous electric energy, sometimes a battery module is added to stabilize the voltage and current. In order to ensure that the output of the entire photovoltaic system is at the maximum power point and improve the utilization rate of solar cells, an MPPT controller based on the model lake algorithm is designed so that the system is always at the maximum power point. The block diagram of the MPPT control system is shown in Figure 2.

3. SCM minimum system design. the

This system design selects STC90C54AD series single-chip microcomputer, which is a new generation of super/high-speed/low-power single-chip microcomputer launched by Hongjing Technology. The instruction code is fully compatible with the traditional 8051 single-chip microcomputer. 12 clocks/machine cycle and 6 clocks/machine cycle can be selected arbitrarily , Internally integrated MAX810 dedicated reset circuit, when the clock frequency is below 12MHz, the reset pin can be directly grounded. The system power supply is provided by a 3-terminal integrated voltage regulator 7805 and an external filter capacitor. The electrolytic capacitor of the power-on reset circuit is 22μF, the resistor is 10k, and a button is connected to both ends of the electrolytic capacitor. Choose 12MHz for the external crystal oscillator, and connect two 30pF trimming capacitors in parallel at both ends. Connect the EA pin to a high voltage to select the internal program memory. The minimum system circuit of the one-chip computer is shown in Fig. 3 . the

4. LCD display circuit design

The information that this system needs to display mainly includes real-time voltage value, current value, power value, duty cycle and so on.

The commonly used outputs of single-chip microcomputers mainly include LED light-emitting diodes, digital tubes, and LCD liquid crystal displays. LCD display has the advantages of high display quality, digital interface, convenient control, small size, light weight, and low power consumption, making it widely used in embedded systems. This system adopts LCD display output, and the display chip is LCD1602. the

LCD1602 is a display with a digital interface. When using it, you only need to set the command word to make it in the corresponding working mode, and then send the ASCII code of the character to be displayed to the chip. Therefore, the P0 port is selected as the parallel data line in the circuit design, because there is no pull-up circuit inside the P0 port, so it needs to connect an external resistor to enable it to output high voltage. The control pins use three ports of the P2 port: P2.7 is connected to the RST pin of the LCD, P2.6 is connected to the R/W pin of the LCD, and P2.5 is connected to the E pin of the LCD. The specific circuit is shown in Figure 4. the

5. Current and voltage detection circuit design

When the system is running, it is necessary to detect the voltage and current values of the solar photovoltaic array in real time for corresponding control. Although both voltage and current are electric quantities, the single-chip microcomputer system still cannot directly handle them. Therefore, it is necessary to convert the current signal into a voltage signal first, and then convert the voltage signal to the acceptable range of the single-chip system AD conversion chip, generally 0~5V. The voltage measurement circuit is composed of a resistor and an operational amplifier. By adjusting the resistor R, it is in the corresponding measurement range. The voltage detection circuit is shown in Figure 5.

Current sensing is achieved using the ACS712 with a precision low bias linear Hall sensor circuit with a copper current path close to the surface of the die. Current applied through this copper current path generates a magnetic field that is sensed by the integrated Hall IC and converted into a proportional voltage. Device accuracy optimization is achieved by placing the magnetic signal close to the Hall sensor. The precise, proportional voltage is provided by a chopper-stabilized, low-bias BiCMOS Hall IC that is factory programmed for precision. The output of the device has a positive slope (>VIOUT(Q)) when current is rising through the primary copper current path (from pins 1 and 2, to pins 3 and 4) used as the current sensing path. The internal resistance of this conduction path is typically 1.2 mΩ, resulting in low power dissipation. The thickness of the copper wire allows the device to operate under overcurrent conditions of up to 5×. The terminals of the conductive path are electrically isolated from the sensor pins (pins 5 to 8), and the current sensing circuit is shown in Figure 6. The voltage and current detection output signals are respectively sent to the 0 channel and 1 channel of the AD conversion chip for AD conversion and input to the single chip microcomputer for control. the

6. AD conversion circuit

The single-chip microcomputer can only process digital signals, but the voltage signal quantity of the actual system is an analog quantity, so AD conversion must be carried out. TI's TLC2543 is selected to realize AD conversion, which is a 12-bit serial, 11-channel, high-speed AD conversion chip. When connecting specific circuits, select channel 0 as the input of the voltage signal, and channel 1 as the input of the current signal. There are four main serial interface lines of the TLC2543 chip. The specific connection method is that the clock signal CLOCK is connected to the microcontroller P10, the serial data input terminal DIN is connected to the microcontroller P11, the serial data output terminal DOUT is connected to the microcontroller P12, and the chip selection signal CS2543 is connected to the microcontroller P13. Only 4 wires are used to connect the TLC2543 and the MCU, and the reference voltage is the MCU system power supply +5V. The specific circuit is shown in Figure 7.

7. Boost conversion circuit

The DC-DC circuit of the system uses a Boost circuit. In order to realize the maximum power tracking control of the system, it is necessary to adjust the turn-on and cut-off time of the system switch tube, that is, to change the size of the duty cycle D. The single-chip microcomputer system calculates the size of D through the internal control algorithm according to the real-time data on site, and realizes the control of the system through the method of pulse width modulation PWM. The pulse output adopts P22 output. In order to reduce the interference of the conversion circuit to the single-chip microcomputer system, photoelectric isolation is carried out at the pulse output. The specific circuit is shown in Figure 8.

8. System software description

The single-chip system program is mainly divided into two parts, namely the main program and the interrupt service program. It is very important for the whole system to divide the two parts of the program reasonably. The system software mainly includes system initialization, AD sampling, fuzzy control, pulse width modulation output, and display output. The overall design of the system software is shown in Figure 9.

In the conception of this system, the main program mainly completes the system initialization program, real-time data sampling, fuzzy controller design, and display program design. Calculate the system duty ratio output through fuzzy control, apply the regular interrupt timer T0, complete the PWM signal conversion, and set its interrupt priority as high. The core of MPPT control is the design of fuzzy controller, and the fuzzy control function diagram is shown in Figure 10. the

The above descriptions are only preferred embodiments of the utility model, and are not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model. the

Claims (2)

1. MPPT photovoltaic charge/discharge controller that utilizes fuzzy algorithmic approach, comprise solar battery array (1) and batteries (3), be connected with controller (2) between described solar battery array (1) and the described batteries (3), described controller (2) is connected with load circuit (4), it is characterized in that: described controller (2) comprises MPPT controller (201), DC-DC translation circuit (202), described MPPT controller (201) is powered by described batteries (3), for detection of voltage and the electric current of described solar battery array (1), and control described DC-DC translation circuit (202); Described solar battery array (1) goes out suitable voltage by described DC-DC translation circuit (202) conversion and supplies with described batteries (3).

2. the MPPT photovoltaic charge/discharge controller that utilizes fuzzy algorithmic approach according to claim 1, it is characterized in that: described MPPT controller (201) also connects a display module (203).

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