Eric returns to his hometown every year. Just last year, he saw new rows of solar photovoltaic panels erected on the roof of his hometown. He immediately realized that the villagers could bring certain benefits from it. Technologist, he was relieved. In fact, Eric’s hometown is a small wave in the photovoltaic power generation (ie solar energy) that is in full swing across the country.

According to the website of the National Energy Administration, my country will add about 53 million kilowatts of photovoltaic power generation grid-connected installed capacity in 2021, ranking first in the world for nine consecutive years. By the end of 2021, the grid-connected installed capacity of photovoltaic power generation will reach 306 million kilowatts, surpassing the 300 million kilowatt mark, ranking first in the world for seven consecutive years.

Looking back on the development of the past 20 years, although the photovoltaic market has also gone through different stages such as the start-up period, the adjustment period, the gestation period and the rapid development period, the total installed capacity has always been rising. There is no doubt that the benefits of photovoltaics are inexhaustible and zero pollution. However, with the continuous development of the industry, there are also some pain points that need to be solved urgently, including cost, efficiency, intelligence, reliability, etc.

The inverter is the core power electronic device of the photovoltaic power generation system, just like the heart of the entire photovoltaic system, its function is to convert the variable DC voltage generated by the photovoltaic modules into the AC frequency of the mains frequency. The chip is the core component of the inverter, so a series of pain points faced by the photovoltaic industry are also innovations being practiced by the chip industry. “Renewable energy sources, including solar energy, are highly dynamic and uncontrollable because they are completely dependent on the natural environment, which brings more challenges to system design,” Eric pointed out.

A higher power inverter means more components, and at the same time there will be power paralleling, which will bring further challenges to the system design, requiring low output distortion, highly accurate voltage and current analog measurement, high Efficiency and power density as well as real-time communication and monitoring features. So what products and technologies can provide competitive solutions for photovoltaic inverter systems?

Smart Brain – Controller

Photovoltaic inverters generally have two power conversion stages, one is a DC-to-DC boost process, and the other is a DC-to-AC inverter process. All these depend on the controller for processing, sensing and control. The controller is the brain of the entire inverter. In order to meet the challenges brought by high dynamics to the system, the selection of the controller becomes the key. As early as the start of China’s photovoltaic market, TI’s C2000 real-time microcontroller (MCU) has been widely used in photovoltaic inverters with its accumulation in the field of power electronic control. Over the years, it has been continuously improved in all aspects, integrating more real-time control analog peripherals while improving the performance of the chip.

In terms of processing, C2000 MCU has a heterogeneous computing architecture composed of multiple processor cores such as ultra-high-performance C28 digital signal processor, hardware algorithm accelerator, CLA (control law accelerator) and CLB (configurable logic block), so as to maximize processing performance. For sensing, multiple parallel ADC modules support a resolution of up to 16 bits and a sampling rate of up to 3.46MSPS, which can accurately measure and monitor the current and voltage of each part of the system. In addition, it also includes rich peripherals such as comparators and DACs. . For the control side, a multi-channel PWM controller with 150ps precision can quickly drive various power conversion devices, even wide bandgap devices based on SiC or GaN.

Reliable Immune Tissue-Signal Chain Isolation

Inverter systems support voltages ranging from a few volts to hundreds of volts. To ensure signal integrity in high-voltage complex environments, isolation devices like human immune tissue are required to reliably isolate potential damage from high-voltage to low-voltage, or to isolate noise resulting in measurement inaccuracy. TI’s digital isolator technology is based on a proprietary silicon dioxide (SiO2) insulating gate, which has many advantages such as ultra-high operating voltage, ultra-high reliability, and high-speed transmission support. Compared with optocoupler solutions, it has longer life and power lower and more compact.

In particular, for the closed-loop control logic of the inverter, it is necessary to sample the voltage and current signals in the high-voltage and high-power system in order to accurately convert the power and ensure that the system can operate reliably at any time. To this end, TI extensively integrates digital isolation technology with its signal chain and power products, enabling higher levels of integration. For example, the reinforced isolation amplifier AMC3302 with integrated DC/DC converter, a single chip realizes the acquisition of the output current signal. Compared with the sensor based on the Hall magnetic effect, it has higher precision, smaller circuit size, and anti-electromagnetic interference. and common mode interference ability is stronger, and the scalability is stronger.

Strong Muscles – Drive and Power Devices

The essence of power conversion is to achieve different voltage changes through the switch of the power tube, just like the muscles and bones of the human body are performing a power supply change process under the command of the brain, so the more robust power devices and corresponding drives are inverters. It is an important manifestation of the efficiency and reliability of the device.

Higher input voltage and smaller passive components are becoming the key development direction of photovoltaic inverters. The former can reduce losses and make power devices smaller, while the latter requires higher switching rates of power devices. To meet the challenges of higher operating voltages and switching speeds, wide bandgap semiconductors such as SiC and GaN can be employed. For example, TI’s GaN FET with integrated driver, protection and temperature reporting can not only improve overall conversion efficiency, reduce system cost, but also enable smaller, lighter and more reliable inverters.

Although wide-bandgap semiconductors have appeared, traditional power devices are still the mainstream of the inverter market. In fact, no matter what kind of power device, a corresponding gate driver is required, and the driver can be simple or complex. Since the power device is the most easily damaged part of the inverter, the intelligent driver with integrated Miller clamp, split output, under-voltage lockout (UVLO), and temperature protection can escort the power device to operate for a long time.

Additionally, noise in the circuit, whether it is power supply ripple or gate ringing, can cause power devices to operate incorrectly and reduce reliability. TI’s smart gate drivers with integrated isolation and protection can effectively isolate noise and other potential high voltage hazards, and can easily adapt to a variety of power devices.

Smart and more

At present, new inverters or combiner boxes generally support mobile phone remote monitoring, which facilitates monitoring and maintenance. TI offers a variety of wired or wireless connectivity processors to meet intelligent connectivity needs, including wireless communication technologies such as Wi-Fi, Wi-Sun, ZigBee, and wired technologies such as Ethernet, CAN, and RS485. In addition, these processors also support a rich HMI to further enhance the operating experience.

For photovoltaic systems that operate for decades, the lifetime and supply continuity of semiconductor devices are reliable guarantees for system stability. TI’s product life cycle is usually 10 to 15 years, and the service life can usually be extended. At the same time, in order to achieve high-quality production, TI has established a comprehensive quality management system since 1985, and it has become a necessary tool in TI’s production process. A commitment to product longevity and continuity of supply, as well as a commitment to product quality, has always been the place where partners recognize TI the most.

In addition to product performance and quality, development support is a user concern, and this is where TI excels. Taking C2000 as an example, TI provides a complete digital power software development kit for photovoltaic and other power fields, including comprehensive software infrastructure, tools and documents, aiming to shorten the development time of digital power system based on C2000 MCU to a greater extent.

In terms of development kits and reference designs, TI launched a solar micro-inverter development kit for string and micro-inverters in 2014. The C2000 solar micro-inverter development kit based on TI’s F28003x MCU enables designers to understand a This is a fully suitable MCU and systematically solves application challenges by breaking down the development process into manageable parts. Users can initially evaluate designs through a simple graphical interface without diving head-first into code development. When ready to delve further, detailed theory-based documentation guides the user through progressively progressive software and hardware implementations through the incremental construction of solar microinverters from open-loop to closed-loop operation.

Currently, C2000 MCU-based reference designs can quickly implement multiple functions including MPPT, inverter, arc detection, and rapid shutdown (RSD).

sustainable future

“The breadth of TI’s products and its attention to vertical fields determine that TI will serve the technological development of various industries, and the photovoltaic market is the best example.” Eric said that TI has always communicated closely with customers in the industry, and has always communicated with customers in the industry. Demand is transformed into product and solution innovation, and the localization team is synchronized with customers, so that new solutions can be selected faster after they come out. “TI has been serving many domestic inverter customers, and we know that only if the customer’s solution is competitive can the industry be competitive, so as to continuously promote the development of the market.”

The concept of sustainable development is now deeply rooted in the hearts of the people, both technological innovation and market capacity are rapidly rising, and Eric is getting busier and busier as a result. From rural areas to cities, from residential buildings to industrial parks, as blue roofs are built in rows, it proves that more and more photovoltaics are playing a role. At this point, he became more convinced that the job had far-reaching value and was already aligned with TI’s vision. That is, through TI’s products and services, to help the renewable energy industry innovate and help the new journey of sustainable development, so as to create a cleaner and more sustainable future for all.

Reviewing Editor: Peng Jing

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