Solar Photovoltaic Technology Basics: The Innovative MLPE Application
Date: 2024-12-12Photovoltaic power is gradually becoming an important force in the transformation of the global energy structure, and the efficiency and safety of PV systems have become the focus of the industry. Module Level Power Electronics (Hereinafter referred to as MLPE) technology is emerged as the times require, bringing revolutionary changes to the system.
By embedding power electronic equipment at the PV module level, MLPE technology achieves refined control and management of the modules. It can improve the power generation efficiency and enhance the safety and reliability of the PV system. The key products of Rapid Shutdown, Optimizer and Microinverter, are gradually becoming an indispensable and important part of the system.
Safety Hazards of PV Systems
Traditional string or centralized inverter systems have significant safety hazards due to the use of high DC voltage (DC1000V/1500V), which mainly include:
1. Fire Risk: Contact detachment, device aging, insulation rupture and poor grounding may cause arcing. Once a fault arc occurs, the flame is difficult to extinguish, and DC voltages of up to several thousand volts may still exist in the system. According to statistics, more than half of power station fire are related to DC arc fault.
2. Electric Shock Hazard: In the daily operation or maintenance of power stations, operators may face the risk of electric shock. When a fire breaks out, PV modules exposed to sunlight may continuously generate high voltages, not only exacerbating the fire, but also restricting the rescue and firefighting operations of the firefighters.
3. Hot spot Effect: Certain areas of the PV panels cannot function properly due to shading, defects or malfunctions. This can lead to overheating in those regions, forming hot spots and potentially causing fires.
4. PID Effect: Potential Induced Degradation (PID), also known as a solar yield killer, is an undesirable performance deterioration induced by the high voltage electricity, which may significantly reduce the output power of PV modules and affect the efficiency of the system.
Requirements and Regulations for PV System Safety
Manycountries around the world have established standards that address PV system safety, such as the United States, Canada, Thailand, Philippines, Germany, Australia and other countries. Specific standards include the United States National Electrical Code (NEC), Canadian Electrical Code 2021, Thailand Electrical Code: Solar Rooftop Power Supply Installations 2022, Philippines PEC 690.12, and other countries require that the PV modules should be installed with a rapid shutdown switch, and within 30s after the rapid shutdown device is started, the voltage within the boundary range (PV matrix 305mm) must be reduced to below 80V. In addition to that, VDE-AR-E 2100-712 (Germany) and AS/NZS 5033 (Australia) stipulate that a shutdown device should be added in PV systems. If the inverter is turned off or the power grid fails in a PV system, the rapid shutdown device must to ensure that the DC voltage is reduced to below 120V to minimize system risks.
MLPE Solutions for PV Systems
To address the above challenges, PROJOY has launched Module Level Power Electronics (MLPE) PV products, including rapid shutdown switches, optimizers, microinverters, which aim to enhance the safety and efficiency of PV systems, providing a safeguard for the safety of PV systems.
Currently, MLPE mainly the following three solutions:
1. String Inverter + Rapid Shutdown
This solution enhances system safety and facilitates maintenance based on the series connection of PV modules. The advantages are as follows:
① Rapid Shutdown: In emergency situations, quickly disconnecting the connections between photovoltaic modules can significantly reduce the risk of electric shock. PROJOY PEFS-PL series enables shutdown through a dedicated control box or AC power disconnection. Within 1 second, it can cut off the DC current between each module, providing a safe rescue environment for firefighters.
②Easy Maintenance: Rapid shutdown device allows operators to perform maintenance quickly and safely without shutting down the entire PV system. PROJOY rapid shutdown solution features a simple cable layout, requiring less expertise from on-site personnel, thus reducing installation costs and time.
③ Localized Isolation: When a fault occurs, the fault area can be isolated to ensure that other modules can continue generating power. PROJOY rapid shutdown is equipped with advanced bypass function. Once a fault is detected, the device can quickly isolate the fault area without affecting other modules, improving the reliability and stability of the system.
④DC24V Control: As a pioneer in the industry to apply DC24V control technology to rapid shutdown devices, PROJOY rapid shutdown can effectively eliminates interference problems and improves the overall anti-interference performance of the system.
String inverters combined with shutdown devices offer a cost-effective solution, making them ideal for commercial and industrial power plants that require a balance between cost and safety. It is especially popular in countries with mandatory regulations, such as the United States, Canada, Thailand, Philippines, Germany, Australia, etc.
2. String Inverter + Optimizer
In addition to rapid shutdown function, this solution also enables module level monitoring to quickly locate faults and increase the power generation of the PV system. The advantages are as follows:
①Maximum Power Point Tracking (MPPT): Track power individually for each module to improve power generation efficiency. The maximum power of PROJOY PEOP series optimizer can reach 1400W and support two 700W modules.
②Fault Diagnosis: Equipped with monitoring and diagnostic capabilities, PROJOY PEOP series optimizer enables quick problem identification. Integrated with PROJOY intelligent cloud platform, it provides module-level real-time monitoring, precise risk alerts, and fault location for power plants. Additionally, it supports remote shutdown and over-temperature protection, ensuring immediate disconnection when necessary.
④ High flexibility: adapt to irregular module layout and reduce efficiency loss. It is worth mentioning that the maximum communication distance of PROJOY optimizer is 150meters, which is convenient for on-site deployment and adapts to the mainstream modules in the market. This provides a distance advantage that surpasses most similar products on the market. The product offers optional clamp or screw-hole installation methods, allowing flexible on-site installation based on specific requirements. This adaptability enhances efficiency, making installation and maintenance more convenient and providing significant benefits to customers.
Since the optimizer integrates MPPT, the cost of this solution is relatively higher than shutdown switch solution. Currently, it is mostly used in complex rooftop PV systems, power stations with complex layouts (eg. Multi-direction installation, multi-specification modules), high temperature or high humidity environments, I&C project, and old system renovation, etc.
3. Microinverter
The microinverter adopts a fully parallel circuit design, and there is no voltage superposition between modules, which fundamentally overcomes the high-voltage risks associated with string systems. The advantages are as follows:
① High Safety: Fundamentally eliminate the risk of fire caused by high voltage DC. PROJOY PSOL series microinverter can link up to six solar panels. The PSOL-MS3300 in particular, has an operating voltage range of 16V to 60V, a maximum input voltage of 60 V, and a maximum input current of 18A. It features a maximum output of 3.3 kW and a maximum output current of 16.5 A.
② High Efficiency: Independent MPPT ensures maximum power output of each module under various conditions. With microinverters, the PV system will continue performing efficiently even if one module isn't producing as much electricity as the others. For example, the efficiency of PROJOY PSOL microinverters can reach 97.2% and the California Energy Commission (CEC) efficiency is 96.7%.
③ Intelligent Monitoring: Monitor module status in real time to quickly discover and solve problems. PROJOY offers a real-time monitoring system called M-cloud V2, simply download the M-cloud V2 app via a smart phone, or sign in the M-cloud V2 Portal on a computer, you will be able to visually compare how each module is performing independently, and quickly identify if a particular panel or micro inverter is failing.
④Flexible Installation: Suitable for various distributed PV systems to reduce the risk of system failure. PROJOY microinverters are affixed to the back of every module and maximize the output of each module independent of the production of any neighboring module, making them suitable for various installation conditions. Moreover, if you consider to expand your rooftop solar system in the future, simply add another pair of PROJOY micro inverter to your existing solar array and that’s it.
⑤ High Reliability: Comparing with string inverters, Microinverters have longer lifespan in general. For instance, PROJOY microinverters are built to last up to 25 years, featuring with IP67 high level of dust-proof and waterproof, no fan design and good heat dissipation. The company offers a minimum 12-year warranty, including the communication module.
⑥ Quiet and No Interference: The microinverter adopts a fan-less design and operates with zero noise. Meanwhile, its electromagnetic compatibility complies with home appliance standards, ensuring harmonious coexistence with other devices and improving safety and reliability.
Since microinverter can perform maximum power point tracking individually for each PV module, it is ideal for residential rooftop PV systems, especially on roofs with shading or complex layouts. In addition, it also performs well in industrial and commercial applications, improving system power generation efficiency and providing real-time monitoring to facilitate management and operation. Moreover, it functions well even in high-temperature and high-humidity environments.
Although microinverters are not typically the most expensive component of a PV system installation, it is to be expected that higher efficiency microinverters may come with higher price tag. However, it can be worth it as the device is safer and more flexible to use, along with the longer warranty, making the device much more cost effective. At present, microinverters have been widely applied in various scenarios around the world, such as balcony PV systems in Germany and Italy, rooftop PV systems in France, the Netherlands and the United States, etc.
With the continuous development and application of module-level power electronics (MLPE), the PV industry is ushering in a profound technological innovation. Rapid shutdown, optimizer and microinverter, as the core of this technology, can not only help improve the safety and efficiency of PV systems, but also lead the industry to become more efficient, smarter, and greener.