Explore the expertise in solar energy, from system controllers and power regulating units to DC optimizers and built-in DC. By breaking down their concepts one by one, truly understand and apply these terms.

system controller Introduction

Within a PV system, the system controller mainly refers to the device used to control and manage battery charging and discharging to ensure the health of the battery and prolong its life. The most common system controller is the charge controller.

System controller Principle

The basic function of the charge controller is to prevent the battery from overcharging. When solar panels generate electrical energy (DC) and store it in the battery, the charge controller monitors the battery's voltage.

When the voltage reaches a certain value, it will reduce the energy flow into the battery, aiming to protect the battery and prevent overcharging. Likewise, when the battery voltage is below a certain value, it will also induce current into the battery, ensuring that the battery can supply power when there is no sunshine or insufficient light.

System Controller Application in PV systems

There's a type of charge controller called the Maximum Power Point Tracker (MPPT), which is a more advanced charge controller. The MPPT controller can monitor the power of the solar panels in real-time and "track" the maximum power point by adjusting the input voltage, allowing the solar panels to always operate at the maximum power, thereby improving the efficiency of the entire system.

In short, the system controller plays a very crucial role in the PV system and is a key component in maintaining a stable system operation.

Part 2: Power regulating unit

The Power Conditioning Unit, abbreviated as PCU, is a critical component used in many electrical and electronic systems. The main function of the PCU is to ensure the quality and stability of the output power to meet the specific needs of the application system.

Key functions of the PCU may include:

DC-AC Inversion: It converts the direct current produced from batteries or solar panels to alternating current.

Frequency Regulation: It ensures that the frequency of the output power matches the grid frequencies.

Voltage Regulation: It ensures that the voltage of the output power is within a safe and effective range.

Power Factor Correction: It minimizes the total harmonic distortion of the system.

Power regulating unit

In PV systems, the Power Conditioning Unit typically includes some key components like an inverter (which converts DC to AC), and some potential protection and management devices, such as circuit breakers, emergency stop switches, battery management systems, etc.

Part 3:Current Transformer Principle

Capacity experiment of the balcony solar power station

A Current Transformer (CT) is crucial for the proper operation of the entire system. CT has polarity, so the correct connection is also crucial.

Current transformers usually have a primary coil and a secondary coil. The primary coil, or marked as "P1", is connected to the measured main current circuit. The secondary coils are "S1" and "S2", used for output line connections to loads or measuring equipment.

Current Transformer

Current Transformer in PV system

In PV systems, CT are typically used to monitor the working current of various circuits and whether protective devices can work normally.

The Current Transformer is frequently used in the inverters of PV systems. The Inverter is one of the most important power electronic devices in a PV system. Its primary task is to convert direct current from solar panels into alternating current, which we use in our daily life. The primary function of the current transformer here is to measure current and provide current protection.

For instance, in a grid-connected PV system, when the system is connected to the electric network, current transformers can be used to monitor the current between the grid and inverters, thereby preventing overly high currents that could affect the stable operation of the electric network.

Part 4: SMA energy meter

The SMA Energy Meter is a high-performance measurement solution used for intelligent energy management in PV systems with SMA devices. The SMA Energy Meter can accurately calculate and balance power parameters.

Here are the main features of the SMA Energy Meter:

Precision Measurement: The SMA Energy Meter can accurately calculate and balance household energy use measurements, including real-time consumption and energy fed back into the grid.

Intelligent Energy Management: When used with SMA's smart PV system devices, it can achieve intelligent energy management and improve the self-sufficiency rate of energy.

Fast Communication: It provides fast data exchange between various connected devices based on high-speed Ethernet communication.

Flexible Compatibility: It can be used with a variety of SMA devices, including Sunny Home Manager and Sunny Island.

Easy Installation: It's easy to install and can quickly connect to the home energy system.

SMA energy meter in PV system

The SMA Energy Meter is primarily installed in the distribution box of the PV system. It is an energy measurement device that can accurately record the amount of energy consumers purchase from the public grid, its further distribution to various consumption devices, and the local supply number generated by the PV power system.

Balcony PV systems are usually smaller systems, such as Stecker-PV or Mini-PV systems, which are directly connected to your residential socket to generate power. For these types of systems, an SMA Energy Meter may not necessarily be required. As for systems of this scale, an SMA Energy Meter might be overly complicated.

Battery clipping

Part 5: Battery Clipping

Battery clipping, also known as solar clipping, is not a physical component, but rather a process that occurs within a photovoltaic system. Battery clipping is a phenomenon that occurs when the power provided by solar panels exceeds the capacity that the inverter can handle.

This is primarily explained as follows: When solar panels generate an abundance of electricity due to ample sunlight and the rated AC power output of the inverter reaches its limit, the inverter will cut off some of the DC input, i.e., start "clipping", to prevent overload. Thus, "clipping" occurs between the inverter and the solar panels when the power generated by the panels surpasses the inverter's handling capacity.

Battery Clipping in PV system

In PV systems, "Battery Clipping" or "Inverter Clipping" is a phenomenon that occurs within an inverter. This is because the inverter's role is to convert the Direct Current (DC) generated by the solar panels into Alternating Current (AC), while also managing the power harnessed from the solar modules.

While this situation might sound disadvantageous, it is often seen as a good thing. This is because the entire PV installation generates the maximum amount of power during the sunniest hours, which might exceed the inverter's maximum power, but this is a temporary situation. In most of the time, the panels will not have enough radiation, and will not exceed the inverter's maximum power. Therefore, the advantage is that brief output limitations do not significantly alter the overall generation of solar power.

Part 6: DC arc

DC Arcing, also known as Direct Current Arc Faults, is a severe power problem that occurs in power systems, especially in DC systems, such as PV systems.

DC Arcing is a phenomenon that occurs in PV systems, particularly when the system voltage exceeds 80 volts. They can generate enough heat to start fires. DC arcs are caused by discontinuity in the DC current due to grounding faults, poor contact, line shorts, or equipment faults, resulting in arcing in the air or other mediums.

Solving the problem of DC Arcing in PV systems:

  • Review and Inspect System Design: Check the entire PV system design, including string configurations, cable sizes, grounding methods, etc. Improper design, such as excessively long lines or insufficient wire diameter, may lead to DC arcing.
  • Optimize Installation Process: Use good engineering practices to reduce incorrect wiring, loose joints, and inappropriate protective device issues. This includes using the correct accessories, such as DC circuit protectors with lateral protective sheaths and load disconnect devices.
  • Regular Inspection and Preventive Maintenance: PV systems should be regularly and thoroughly examined to identify and resolve potential problems, such as corrosion, hot spots, or wire breakage. These can all lead to DC arcing.
  • Use of Arc Fault Circuit Interrupters: Arc fault detectors or DC arc circuit breakers can detect and isolate potential DC arcs. Many PV inverters and combiner boxes have integrated this type of device. This is a passive protection measure that can immediately cut off power after a fault occurs, thus preventing further extension of the arc.
DC arc

Part 7: DC optimizer

A DC Optimizer is a module-level power electronic device that can optimize the direct current voltage of PV modules, thereby maximizing the energy output of the entire PV array.

In a traditional PV system, as all PV modules are connected in series, the performance of one module can affect the output of the whole string. A DC optimizer can eliminate this effect, allowing every PV module to independently yield its best performance and reduce the mismatch impact of PV modules. A DC optimizer is usually installed on each PV module.

Adding a DC optimizer between the PV module and the inverter can prevent the entire system from lagging due to the decreased performance of a module, while also tracking the performance of each module. It responds to changes in module ageing, pollution, and shadow shading, maximizing overall system benefits.


Part 8: Built In DC

In PV systems, "Built-in DC" likely refers to built-in direct current power sources or devices. Solar panels, the core components of a PV system, produce direct current (DC) through the PV effect, which is a significant reason why solar energy is a DC power source.

One possible application scenario is the energy storage devices used in grid-connected PV systems. Such devices usually have built-in DC-AC (Direct Current to Alternating Current) power inverters, and some are equipped with Maximum Power Point Tracking (MPPT) charge controllers. They can directly convert the DC generated by solar panels into AC (Alternating Current) used for household appliances. They can also store electricity for reserves and provide a stable power supply during power outages or other situations.

In PV systems, the built-in power source usually refers to the solar panels as they convert solar energy into electrical energy or direct current (DC) via PV effect. Devices like DC optimizers and inverters process this current for optimizing and utilizing the electrical energy.

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