Design of power supply system integrating solar energy, wind energy and city electricity

The use of solar energy, wind energy, and market electricity to form a three-in-one power supply system for energy-saving LED power supply is a new power supply system with high cost performance. Wind energy and solar energy have natural complementary advantages. The sun is strong during the day and the wind is strong at night; the sunshine is good in summer and the wind is weak; the wind is strong in winter and the sunshine is less. When the natural wind energy and light energy are very weak, the market electricity is started as a backup power supply to ensure that the load can work stably in a long-term and reliable state.

1 Composition of the lighting system
This system is mainly composed of a power supply system, a control system, a battery, an LED load, an inverter, etc., as shown in Figure 1.

1.1 Power supply part
The power supply part is mainly composed of one or more wind turbines (including wind turbine controller), solar photovoltaic panels (including photovoltaic panel controller), and 220 V mains electricity.
1) Wind turbines use wind turbines to convert electrical energy into mechanical energy, and then convert mechanical energy into electrical energy through wind turbines. Through the control of the controller, one is to directly supply electrical energy to DC load LED lights or supply AC loads through DC/AC inverters, and the other is to charge the battery pack with excess electrical energy. The output power of the wind turbine is

Where: R is the radius of the wind rotor blade; V is the wind speed; CP is the wind energy utilization coefficient, and the maximum value is 0.593.
The wind rotor blades are divided into fixed pitch and variable pitch. In the wind speed range below the rated wind speed, the CP of the fixed pitch wind turbine cannot reach the optimal value, and the output power is low; after exceeding the rated wind speed, the CP will also deviate from the optimal value, and the output power will decrease; only at the rated wind speed, the CP has the optimal value, so that the output power is maximized. For variable pitch wind turbine, the CP can be maximized by adjusting the pitch angle at startup, and the output power is large; after exceeding the rated wind speed, the CP is kept at the best by adjusting the pitch angle, and the output power is kept at the rated value. 2) Photovoltaic power generation uses the photovoltaic effect of solar panels to convert light energy into electrical energy. After the control of the control center, the battery pack is charged, and the electrical energy is directly supplied to the DC load LED lamp or to the AC load through the DC/AC inverter. The ideal PN junction solar photovoltaic cell IV equation is:

Where: IS, VS are the output current and output voltage of the photovoltaic cell; IN, I0 are the short-circuit current and PN junction reverse saturation current of the photovoltaic cell; K is the Bohr constant, K=1.38x10-23J/K; T is temperature; q is the amount of electron charge, q=1.6x10-19C.
Under certain temperature and sunshine conditions, the output power of the photovoltaic cell has a maximum value. During the power generation process, the internal resistance of the battery is not only affected by the intensity of sunshine, but also by the ambient temperature and load. In order to obtain the maximum power during photovoltaic power generation, the size of its own impedance must be constantly changed to achieve the best match between the photovoltaic array and the load, achieve high current and high voltage output, and improve the efficiency of system power generation.
3) 220 V mains The introduction of 220 V mains is to supply power to the load more reliably and stably. When the power supply of solar photovoltaic cells and wind turbines is insufficient, the mains is started as the last power supply to ensure the power supply of the load through the control of the controller.
1.2 Control part
1) Function of the control circuit
The control part is the core content of this circuit. Through the controller, the connection and combination of various parts of the power system and the automatic control of the charging of the battery pack are completed. The device can continuously switch and adjust the working state of the battery pack according to the intensity of sunshine, the size of wind and the change of load. On the one hand, the adjusted electric energy is directly sent to the DC load or sent to the AC load through the inverter; on the other hand, the excess electric energy is sent to the battery pack for storage. When the photovoltaic power generation and wind turbine power generation cannot meet the load power, the controller transfers the power in the battery pack to the load; when the power in the battery pack is also insufficient, the controller finally uses 220 V mains as the power supply. In this way, the power supply system can alternately operate under various working conditions such as charging, discharging or floating power, thereby ensuring the continuity and stability of the load power supply system using wind, light and mains as complementary power sources.
2) Control process of control circuit
The control process of the wind, light and mains complementary power supply system is relatively complex. The industry uses process control technology to monitor and intelligently manage the operating conditions of the system. According to the characteristics of the system, the field control layer realizes the control of various sensors, transmitters and actuators and the field data acquisition process. The intelligent monitoring system is divided into two layers: the bottom layer is a monitoring layer based on a microprocessor chip, which is responsible for optimizing the operation of a single device and setting parameters. At the same time, it has the ability to communicate with the upper layer; the upper layer is a coordination management layer based on a microcomputer, which is mainly used for field
data processing, and at the same time handles the coordination control and grid-connected power supply problems when multiple power supplies are running in parallel.
①The main function of the monitoring layer: mainly to detect the system status, such as wind speed, solar radiation intensity, battery voltage, load requirements and other operating parameters. The energy management layer is responsible for the system and power supply mode switching and load control issues. The communication control realizes communication with the upper management system, provides the operation and equipment parameters required by the system, and changes the system's operating conditions according to instructions.
②The main function of the coordination management layer: to realize communication, including communication with the underlying monitoring layer, obtain operating parameters and send control instructions to the monitoring layer to adjust the system's operating conditions. The data system is the basis for the operation of the upper coordination management layer. It obtains the operating parameters and equipment status of the power supply system through communication with the underlying monitoring layer; the coordination control layer monitors the system's operating parameters and flexibly adjusts the operating conditions of each device in order to achieve the best.
1.3 Battery pack
The battery pack plays a dual role in energy regulation and load balancing in this system. It converts the electrical energy output by wind turbines and solar cells into chemical energy and stores it for use when there is insufficient electricity. Among the commonly used batteries, there are mainly aluminum acid batteries, alkaline nickel batteries and iron nickel batteries. Among them, aluminum acid batteries are inexpensive, reliable, safe, and have been widely used due to continuous technological progress and improvement.
1.4 Inverter It
consists of one or several inverters. Its function is to convert the DC power in the battery pack into standard 220 V AC power. It also has an automatic voltage stabilization function, which can improve the quality of power supply of the wind-solar hybrid power generation system and ensure the normal use of AC load equipment.
1.5 LED load
LED lamp (Light Emitting Diode), that is, light emitting diode. It is a semiconductor light-emitting device. It uses solid semiconductor chips as light-emitting materials. When a forward voltage is applied to both ends, it directly emits red, yellow, green, cyan, orange, purple, and white light. Compared with traditional light sources, LED lamps have the following characteristics:
1) Multi-changeable LED light sources can use the short time of LED and the principle of red, green, and blue three primary colors to achieve multiple changes in color and pattern under the control of computer technology. It is a "dynamic light source" that can be controlled at will.
2) Long life LED light source has no filament, low working voltage, and can reach 50,000 to 100,000 hours of service life, that is, 5 to 10 years.
3) Environmentally friendly There are no harmful elements in production, no harmful substances in use, and no radiation.
4) High-tech Compared with traditional light sources, LED light sources integrate high-tech such as computers, networks, and embedded systems, and have the characteristics of online programming, unlimited upgrades, and flexibility.

2 Working principle of the circuit
Wind turbines convert wind energy into electrical energy, and solar panels convert light energy into electrical energy. Under the action of the controller, these two types of electrical energy can power the load on the one hand. The DC load LED lamp can directly obtain the drive of DC power, and the AC load obtains the drive of AC power after converting DC power into AC power through the inverter: On the other hand, the controller charges the battery with excess power from the wind turbine and solar panels, and the battery converts this power into chemical energy and stores it for use when the wind and solar generators are insufficient.
When the wind and solar generators are not generating enough electricity, the controller will call on the backup power stored in the battery pack to continue to provide power to the load; when the power in the battery pack is also insufficient, the controller will open the 220 V mains power channel as the power supply for the load to ensure that the load can work normally under any circumstances
.
This new power supply system is introduced through the decoration example of a Dong ethnic group wind and rain bridge scenic spot with ethnic characteristics in Jinping County, Guizhou Province. In the actual project, a channel power amplifier is added between the LED load and the controller, and the other parts are the same as Figure 1. Since the system has been used, about 95% of the power comes from wind energy and solar energy in summer, and the city power is rarely used. It works from 18:00 in the afternoon to 6:00 in the morning of the next day. The main parameters of the square circuits used in the project are as follows.
3.1 Solar cell group
Main technical parameters: nominal power: 40 W; peak voltage: 17.35 V; peak current: 2.3 A; open circuit voltage: 21.88 V; short circuit current: 2.46 A; size:
668x454x35 mm;
3.2 Wind turbine
Main technical parameters: model FD1.5-350; wind rotor diameter/m: 1.5; number of blades: 3; blade material: fiberglass composite resin; speed limit mode: automatic sideways; cut-in wind speed/(m/s): 1.5; rated wind speed/(m/s): 5; cut-out wind speed/(m/s): 15; high wind speed resistance/(m/s): 30; rated output power/W: 350; maximum output power/W:
500; output voltage/V: 24 V (DC); control mode: electronic control; generator speed / (dmin): 450; tower height / m: 6; mass / kg: 100; battery: N120 × 2 (120 Ah).
3.3 Battery pack
Main technical parameters: rated voltage: DC24 V; capacity: 400 Ah; floating charge: 20 ~ 50Ah; overcharge time: 1 hour; ambient temperature: about 25℃; life: 5 years.
3.4 Switching power supply
Main technical parameters: Input voltage range: 85~265 VAC; Input frequency range: 47~63 Hz; Output voltage: DC24V; Output power: 1 100; Efficiency: >75% (typical value); Linear adjustment rate: ≤0.5%; Load adjustment rate: ≤1%; Ripple and noise: ≤1%V; Output voltage adjustment range: ±10% (main circuit); Output overload protection: 105%~150%; Output overvoltage protection: 115%~150%; Insulation resistance: ≥100 MΩ (500 VDC); Working environment temperature: -10~60℃.
3.5 Controller
Main technical parameters: wind turbine rated power: 300 W; solar power: 300 W; battery rated voltage/V: 24 V; control mode: PWM; display mode: LED; working environment temperature: -10～55℃; working environment humidity: 0～90%; protection type: overcharge protection, reverse connection protection, solar anti-reverse charge protection, automatic unloading protection.
3.6 Load LED
The load LED lamp is 900 W (5050 type soft light strip). Main technical parameters: working voltage: 24 V; power supply efficiency>95%; power factor>0.95; total harmonic distortion<20%; LED luminous efficiency 90~100 lm/W; LED luminous flux/lm: 16300; lamp luminous flux/lm: 15 420; lamp efficiency>94% color temperature/K: 4 000~6 500 K; asymmetric light distribution curve; rectangular light spot; junction temperature/Tj: 80℃; system thermal resistance (Rja): 10 K/W; color rendering index: Ra>80; working temperature: -30~40℃; storage temperature: 10~75℃; service life>50 000 hours; protection level IP65.
3.7 RP306 three-channel power amplifier
Main technical parameters: DC power input: 24 V; input/output channels: 3; power output: 5 A 24 V 360 W per channel; size: 365x39x26 mm.
3.8 CT308-RF multi-function LED display controller
Main technical parameters: DC power input: 24 V; input/output channels: 3; power output: 5 A 24 V 400 W per channel; remote control distance: 50 m; size: 211x30x25 mm.

4 Conclusion
Wind energy and solar energy are both clean energy. With the improvement of photovoltaic power generation technology and wind power generation technology, the foundation has been laid for the promotion and application of wind-solar complementary power generation systems. Using wind energy, light energy and a small amount of AC power to cooperate to form a three-in-one excitation power supply is more conducive to promoting the construction of a resource-saving and environmentally friendly society.