What Is a Solar Controller?

The solar controller is called the solar charge-discharge controller, which is an automatic control device used in a solar power generation system to control the multi-channel solar battery array to charge the battery and the battery to supply power to the solar inverter load. It regulates and controls the charge and discharge conditions of the battery, and controls the power output of the solar cell module and the battery to the load according to the power demand of the load. It is the core control part of the entire photovoltaic power supply system.

Chinese name: Solar Controller
Foreign name: Controller of Photovoltaic Power Systems

Full name: Solar charge and discharge controller
operating system: The Sun can generate system

Solar controller introduction

The solar control system consists of solar panels, batteries, controllers and loads.

The solar controller is a device used to control the photovoltaic panel to charge the battery and provide a load control voltage for voltage sensitive equipment. It regulates and controls the charge and discharge conditions of the battery, and controls the power output of the solar cell module and the battery to the load according to the power demand of the load. It is the core control part of the entire photovoltaic power supply system. ^[1] It is designed for the power supply system of communication or monitoring equipment in remote areas. The controller's charge control and load control voltages are fully adjustable and can display battery voltage, load voltage, solar array voltage, charging current and load current. ^[2]

Almost all solar power systems that use battery power require a solar charge-discharge controller. The role of the solar charge and discharge controller is to regulate the power, the power delivered from the solar panel to the battery. Battery overshoot, at least significantly reduces battery life, from the worst damage to the battery until it can no longer be used normally. ^[3]

The solar controller uses a high-speed CPU microprocessor and a high-precision A / D analog-to-digital converter. It is a microcomputer data acquisition and monitoring control system. Not only can the current working status of the photovoltaic system be quickly and real-timely collected, the working information of the PV station can be obtained at any time, but the historical data of the PV station can be accumulated in detail, which provides an accurate and accurate way to evaluate the rationality of the PV system design and the reliability of the system component quality Sufficient basis. In addition, the solar controller also has a serial communication data transmission function, which can centrally manage and remotely control multiple photovoltaic system substations.

Solar controllers usually have 6 nominal voltage levels: 12V, 24V, 48V, 110V, 220V, 600V.

At present, the controller develops to multiple functions, and there is a tendency to integrate the traditional control part, inverter and monitoring system.

Solar controller role

The most basic function of the solar charge and discharge controller is to control the battery voltage and open the circuit, and also to stop the battery charging when the battery voltage rises to a certain level. Older controllers mechanically complete the opening or closing of control circuits, stopping or starting the power delivered by the power supply to the battery.

Controllers are used in most photovoltaic systems to protect the battery from overcharging or overdischarging. Overcharging may cause the electrolyte in the battery to vaporize and cause malfunctions, while overdischarging may cause premature battery failure. Overcharge and over discharge may damage the load. Therefore, the controller is one of the core components of the photovoltaic power generation system and the main part of the Balance of System (BOS).

In simple terms, the role of solar controllers can be divided into:

1. Power adjustment function;

2. Communication function: 1 Simple indication function 2 Protocol communication function such as RS485 Ethernet, wireless and other forms of background management;

3. Perfect protection function: electrical protection reverse connection, short circuit, over-current, etc. ^[3]

Solar controller principle

Solar panel is a photovoltaic device (the main part is semiconductor material), and it will generate electricity by photoelectric effect after being irradiated with light. Due to the properties and limitations of materials and light, the current generated by them is also a wavy curve. If the generated current is directly charged into the battery or directly supplies power to the load, it will easily cause damage to the battery and load, causing serious damage Reduced their life. Therefore, we must first send the current to the solar controller, digitally adjust it with a series of dedicated chip circuits, and add multi-level charge and discharge protection. At the same time, our company s unique control technology "Adaptive three-stage charging mode (Figure 1) "to ensure the safety and service life of the battery and load. When power is supplied to the load, the current of the battery is also allowed to flow into the solar controller, and after it is adjusted, the current is sent to the load. The purpose of this is: one is to stabilize the discharge current; the other is to ensure that the battery is not over-discharged; the third is to perform a series of monitoring and protection on the load and the battery.

If you want to use AC power equipment, you also need to add an inverter before the load to invert to AC. ^[4]

Main features of solar controller

1.Using single-chip microcomputer and special software to realize intelligent control;

2. Accurate discharge control using battery discharge rate characteristics correction. The end-of-discharge voltage is a control point modified by the discharge rate curve, which eliminates the inaccuracy of pure voltage control over-discharge, which is consistent with the inherent characteristics of the battery, that is, different discharge rates have different end-voltages;

3. It has full-automatic control such as overcharge, overdischarge, electronic short circuit, overload protection, unique anti-reverse connection protection; the above protection will not damage any components and will not burn insurance;

4. The series PWM charging main circuit is adopted, which reduces the voltage loss of the charging circuit by nearly half compared with the charging circuit using a diode, and the charging efficiency is 3% -6% higher than that of non-PWM, which increases the power consumption time; the improvement of over-discharge recovery Charging, normal direct charging, and float charging automatic control methods make the system have a longer service life; meanwhile, it has high-precision temperature compensation;

5.Intuitive LED luminous tube indicates the current battery status, let users know the usage status;

6. All controls use industrial-grade chips (only for industrial controllers with I), which can run freely in cold, high-temperature and humid environments. The crystal timing control is used at the same time, and the timing control is accurate;

7, canceled the potentiometer adjustment control set point, and used the E-side memory to record the working control points to digitize the settings, eliminating the control point errors due to potentiometer vibration deviation, temperature drift, etc. reduce accuracy and reliability Sexual factors

8. Using digital LED display and settings, all settings can be completed with one-click operation. The extremely convenient and intuitive function is to control the working status of the entire system and to protect the battery from overcharge and overdischarge. In places with large temperature differences, qualified controllers should also have the function of temperature compensation. Other additional functions such as light-controlled switches and time-controlled switches should be optional for the controller. ^[5]

Solar controller mode

1. Pure light control mode: When there is no sunlight, the light intensity drops to the starting point. After the controller delays for 10 minutes to confirm the start signal, the load is turned on according to the set parameters and the load starts to work; when there is sunlight, the light intensity rises to start Point, the controller delays the output for 10 minutes after confirming the shutdown signal, and the load stops working.

2. Light control and time control mode: The startup process is the same as that of pure light control. When the load works until the set time, it will automatically turn off. The set time is 1 to 14 hours.

3. Manual mode: In this mode, the user can control the opening and closing of the load through the keys, regardless of whether it is day or night. This mode is used for some special loads or debugging.

4. Debug mode: It is used for system debugging. The load is turned off when there is a light signal, and the load is turned on without a light signal. It is convenient to check the correctness of system installation during installation and debugging.

5. Normally open mode: The load is always in the output state when it is powered on. This mode is suitable for loads that require 24-hour power supply.

Solar controller classification

Popular solar controllers on the market include general solar controllers, PWM solar controllers and MPPT solar controllers.

The ordinary solar controller is the first generation technology. The working principle is to directly hang the output of the solar panel to the battery port. When the battery is sufficient, it will be disconnected. Because of the internal resistance of the battery, it is difficult to fill the battery, and the solar panel It is not fully utilized, and the charging conversion efficiency is only 70 to 76%, which has been eliminated by the market and basically few people use it.

The PWM solar controller is the second generation technology, and it is currently the most widely used on the market. The working method is PWM control. Compared with ordinary solar controllers, it has improved a lot. It can solve the problem of battery dissatisfaction. The charging conversion efficiency is 75 ~ 80% , But solar panels are not fully utilized.

MPPT solar controller is the third-generation technology, the highest-end solar controller. MPPT solar controller refers to a solar controller with "Maximum PowerPoint Tracking" function. It is an upgraded product of the PWM solar controller. MPPT solar controller can detect the voltage and current of the solar panel in real time and continuously track the maximum Power (P = U * I), so that the system always charges the battery with the maximum power, MPPT tracking efficiency is 99%, the entire system power generation efficiency is as high as 97%, and the battery has excellent management, divided into MPPT charging, constant Voltage equalization charging and constant voltage floating charging. With the advancement of technology and energy conservation, the trend of MPPT solar controller replacing traditional PWM solar controller is irreversible. ^[6]

Solar controller function

The new solar controller has the following main functions:

1. Overcharge protection: When the charging voltage is higher than the protection voltage, the battery is automatically shut down to charge the battery. After that, when the voltage drops to the sustaining voltage, the battery enters the floating charge state. When it is lower than the recovery voltage, the floating charge is closed and the battery is in the uniform charging state. .

2. Over-discharge protection: When the battery voltage is lower than the protection voltage, the controller automatically turns off the output to protect the battery from damage; when the battery is recharged, it can automatically restore power.

3. Load over-current and short-circuit protection: After the load current exceeds 10A or the load is short-circuited, the fuse is blown, and it can continue to be used after replacement.

4. Over-voltage protection: When the voltage is too high, the output is automatically turned off to protect the appliance from damage.

5, with anti-recharge function: using Schottky diodes to prevent batteries from charging solar cells.

6, with lightning protection function: When a lightning strike occurs, the varistor can prevent lightning strikes and protect the controller from damage.

7. Reverse polarity protection of solar cell: The polarity of the solar cell "+" "-" is reversed, and it can be used again after correction.

8. Reverse battery protection: The battery + and - are connected in reverse polarity, and the fuse is blown. It can be used after replacement.

9. Battery open circuit protection: In case the battery is open circuit, if the solar battery is normally charged, the controller will limit the voltage across the load to ensure that the load is not damaged. If the battery is not charged at night or the solar battery is not charged, the controller Without electricity, nothing will happen.

10. With temperature compensation function. ^[7]

11. Self-inspection: When the controller is affected by natural factors or improper operation, it can let the controller self-inspect, let people know whether the controller is intact, reduce a lot of unnecessary man-hours, and create conditions for winning project quality and duration. .

12. Recovery interval: It is the recovery interval for overcharge or over-discharge protection to avoid the working resistance of the load caused by the line resistance or the self-recovery characteristics of the battery.

13. Temperature compensation: monitor the temperature of the battery, and amend the charge and discharge values to make the battery work in an ideal state.

14, light control: mostly used for automatic lighting, when the environment is bright enough, the controller will automatically turn off the load output; and when the environment is dark, it will automatically turn on the load to achieve the function of automatic control. ^[2]

Solar controller installation and precautions

1. Open the package and fix it in a suitable position (please avoid direct sunlight and humid places).

2. Connect the battery lead first (in order to prevent the automatic identification function from error), and wait for the controller to complete the identification process (after the level indicator indicates the battery power), and then connect the solar cell lead, and finally the Connect the load line in the case.

3. In order to use it safely, do not make the load too large or increase the solar panel too much; use a power source such as a power generator instead of the solar cell to charge the battery.

4. When charging, remove the solar panel, the charging current should not be too large.

4. Pay attention to the positive and negative terminals of the battery. ^[2]

Common faults and troubleshooting of solar controller

1.The load is not working

(1) During the day, the controller has light control.

(2) The battery is low.

(3) Whether the wiring is correct.

(4) Remove all wires, repeat the above installation process, and let the controller re-identify.

2. It can be used for the first few days and will not work after a few days

(1) The solar cell wiring is incorrect.

(2) The solar cell is not connected well.

3.Cannot be light controlled

(1) The solar cell wiring is incorrect.

(2) This function is not set, please reset it.

4. It works when it is turned on. It cannot be controlled by light or time.

(1) This function is not set, please reset it.

(2) The ambient light of the solar panel is strong enough.

5, work instructions flashing

The load has a short circuit or is too heavy. ^[2]

Solar controller protection mode

1. Direct charge protection point voltage: Direct charge is also called emergency charge, which belongs to fast charging. Generally, when the battery voltage is low, the battery is charged with high current and relatively high voltage. However, there is a control point, also called protection. The point is the value in the table above. When the battery terminal voltage is higher than these protection values during charging, direct charging should be stopped. The voltage of the direct charge protection point is generally the "overcharge protection point" voltage. When charging, the battery terminal voltage cannot be higher than this protection point, otherwise it will cause overcharge and damage the battery.

2. Voltage of uniform charge control point: After the direct charge is completed, the battery is generally left for a period of time by the charge and discharge controller to allow its voltage to fall naturally. When it falls to the "restoration voltage" value, it will enter the uniform charge state. Why design equal charge? That is, after the direct charging is completed, there may be some batteries "behind" (the terminal voltage is relatively low). In order to pull these individual molecules back, so that all the battery terminal voltages are uniform, it is necessary to use a high voltage with moderate Charge for a short while, it can be seen that the so-called uniform charging, that is, "equilibrium charging". The average charging time should not be too long, generally several minutes to ten minutes. Setting the time too long is harmful. For small systems equipped with a two-cell battery, charging is not significant. Therefore, the street lamp controller generally does not have equal charging, and there are only two stages.

3. Floating charge control point voltage: Generally, after the charging is completed, the battery is also left for a period of time to allow its terminal voltage to fall naturally. When it drops to the "maintenance voltage" point, it enters the floating charge state, similar to "trickle" "Charging with low current" (that is, charging with a small current), charging the battery as soon as the voltage is low, charging it as low as possible, so as to prevent the battery temperature from rising continuously, which is very good for the battery. , Because the internal temperature of the battery has a great impact on charge and discharge. In fact, the PWM method is mainly designed to stabilize the battery terminal voltage. By adjusting the pulse width, the battery charging current is reduced. This is a very scientific charging management system. Specifically, when the remaining capacity (SOC) of the battery is more than 80% in the later stage of charging, the charging current must be reduced to prevent excessive outgassing (oxygen, hydrogen, and acid gas) due to overcharging.

4. Over-voltage protection termination voltage: This is easier to understand. The battery discharge cannot be lower than this value, which is a national standard. Although battery manufacturers also have their own protection parameters (enterprise standard or line standard), they still have to move closer to the national standard. It should be noted that for safety reasons, the voltage of the 12V battery over-discharge protection point is generally artificially added with 0.3v as a temperature compensation or zero drift correction of the control circuit. In this way, the voltage of the 12V battery over-discharge protection point is 11.10v, The over-discharge protection point voltage of the 24V system is 22.20V.

Solar controller related options

Solar controller protection voltage

Some customers often find that after a certain period of solar street lights, especially after continuous rainy days, the street lights will not turn on for several days or even many days, the battery voltage is normal, and the controller and lights are not faulty.

This problem has puzzled many engineering companies. In fact, this is a problem of the voltage value of "exiting undervoltage protection". The higher the value is set, the longer the recovery time after undervoltage, which causes it to fail to light for many days. light.

Solar controller current output

Due to its own characteristics, LEDs must be constantly or current-limited by technical means, otherwise they cannot be used normally. Common LED lamps use an additional drive power supply to achieve constant current to the LED lamps, but this driver accounts for about 10% -20% of the total lamp power, such as a theoretical 42W LED lamp, plus The actual power after driving may be around 46-50W. When calculating the power of the battery board and the capacity of the battery, an additional 10% -20% must be added to meet the power consumption caused by the drive. In addition, adding more drivers will create a link that causes a fault. The industrial controller uses software to perform constant current without power consumption, high stability, and reduced overall power consumption.

Solar controller output period

Ordinary controllers can only be set to shut down for a few hours, such as 4 hours or 8 hours after the light is turned on, which can no longer meet the needs of many customers. The industrial controller can be divided into 3 periods, and the time of each period can be set arbitrarily. Depending on the use environment, each period can be set to the off state. For example, some factories or scenic areas are closed at night, and the second time period (late night) can be closed, or the second and third time periods can be closed to reduce the use cost.

Solar controller output power

Among the lamps for solar applications, LED lamps are the most suitable to achieve different power output by pulse width adjustment. While limiting the pulse width or current, the duty cycle of the entire output of the LED light is adjusted. For example, a single 1W LED 7 string of 5 and a total of 35W LED lights, discharge at night, can be performed at night and early morning Power adjustment, such as 15W in the middle of the night and 25W in the early morning, and lock the current, so that it can meet the night's lighting, and save the cost of battery panels and batteries. It has been proved through long-term tests that the LED lamp with pulse width adjustment mode generates much less heat, which can prolong the service life of the LED.

In order to achieve the purpose of saving electricity at night, some lighting factories have made the interior of the LED lamp into two power sources, and turned off one power source at night to reduce the output power by half. However, it has been proved that this method will only cause half of the light sources to emit light first. Decay, inconsistent brightness, or early damage to a light source.

Solar controller line loss compensation

Automatic compensation is given according to different wire diameters and wire lengths. Line loss compensation is actually very important in low-voltage systems, because the voltage is low and the line loss is relatively large. If there is no corresponding line loss voltage compensation, the voltage at the output end may be much lower than the input end, which will cause the battery to advance. Under voltage protection, the actual application rate of battery capacity is discounted. It is worth noting that, when using low-voltage systems, in order to reduce the line loss voltage drop, try not to use too thin cables, and the cables should not be too long.

Solar controller cooling

In order to reduce costs, many controllers do not consider heat dissipation. In this way, when the load current is large or the charging current is large, the heat increases and the internal resistance of the field tube of the controller is increased, which causes the charging efficiency to decrease significantly. It is greatly reduced or even burned, especially the outdoor ambient temperature in summer is very high, so a good heat dissipation device should be essential for the controller.

Solar controller charging mode

The charging mode of the conventional solar controller is a three-stage charging method copied from the utility charger, that is, three stages of constant current, constant voltage, and floating charging. Because the energy of the mains power grid is infinite, if the constant current charging is not performed, it will directly cause the battery to burst and damage, but the solar panel light system has limited power. Therefore, it is not possible to continue to use the constant current charging method of the mains controller. Scientifically, if the current generated by the battery board is greater than the current limited by the first stage of the controller, then the charging efficiency will be reduced. The MCT charging method is to track the maximum current of the battery board without causing waste. By detecting the battery voltage and calculating the temperature compensation value, when the battery voltage is close to the peak value, the pulsed trickle charging method is adopted, which can fully charge the battery. It also prevents the battery from overcharging.