Driven by the "dual carbon" goal, distributed photovoltaics have become an important carrier for energy transformation due to their flexible deployment advantages. As the core equipment for converting photovoltaic modules from DC to AC, micro inverters effectively solve the mismatch losses and safety issues of traditional string based solutions with module level precision control, highlighting their value in household and building integrated photovoltaics (BIPV) scenarios. With the upgrading of industry demand for high integration, high efficiency, and low cost, single-stage architecture is leading the technological revolution of micro inverters with its minimalist design and high-performance advantages.

Zhaoyi Innovation is deeply rooted in the semiconductor field and has officially launched a single-stage micro inverter solution based on high-performance GD32G553 MCU according to the hot topics in the photovoltaic industry. The solution adopts a one to one architecture and has advantages such as high efficiency, low loss, high integration, and cost optimization. It can meet users' application needs for intelligent operation and maintenance, system reliability, and other aspects in distributed photovoltaic systems, and help photovoltaic micro inverter solutions develop towards a more intelligent, integrated, and low-carbon direction.

Zhaoyi Innovations 500W Single Stage Photovoltaic Micro Inverter Solution

Realize innovation on a single level architecture

As an energy conversion device directly integrated into the back of a single or few photovoltaic modules, the core technological advantage of micro inverters lies in their unique component level maximum power point tracking (MPPT) function. This feature enables it to maximize system power generation by independently optimizing the power output of each component in scenarios with performance differences between components or local shadow occlusion. At present, it is widely used in scenarios that require high flexibility and safety, such as household distributed photovoltaic systems and building integrated photovoltaics (BIPV).

According to the different circuit structures, micro inverters are mainly divided into two architectures: two-stage and single-stage. Compared with traditional two-tier architecture, single-stage architecture has become the main direction of industry technological evolution due to its higher energy conversion efficiency, simpler BOM, and lower manufacturing costs. The 500W single-stage micro inverter solution launched by Zhaoyi Innovation adopts a single-stage one to one architecture based on GD32G5 series MCU and nano micro semiconductor bidirectional GaNFast gallium nitride power chip, which embodies the core advantages of this technology direction.

Comparison of single-stage micro inverse and two-stage micro inverse architectures

Single level architecture achieves efficiency improvement while simplifying the circuit structure by eliminating the first stage DC-DC conversion link. It is worth noting that this architecture also supports reactive THD optimization and one-to-one extension on the basis of implementing micro inverse core functions, meeting the technical requirements of different application scenarios.

The single-stage topology architecture mainly consists of a primary full bridge circuit, a transformer, a secondary half bridge circuit, and an EMI filtering circuit. By coordinating the primary phase shift control with the secondary phase shift control, the voltage at both ends of the transformer leakage inductance is adjusted, thereby controlling the magnitude of the leakage inductance current and achieving efficient power transmission control. To meet the requirements of wide voltage gain and power transmission ratio in micro inverter applications, a single modulation mode is difficult to balance the dual goals of power transmission range and efficiency optimization. The hybrid modulation mode dynamically switches modulation modes through soft switching and power transmission conditions, effectively reducing reflux power while ensuring the given power transmission target, and expanding the soft switching range, thus meeting the requirements of high-efficiency energy transmission and high-quality grid connection.

At the technical implementation level, it is easy to encounter problems such as wave loss and continuous wave during the phase shift control process. The innovative GD32G553 MCU from Zhaoyi provides a comprehensive solution to the above problems through high-precision and highly flexible high-precision timer (HRTIMER) peripherals, as well as functions such as phase shift counting reset and synchronous update between carriers. At the same time, the GD32G553 MCU has powerful computing power, flexible PWM wave generation mechanism, and abundant analog peripheral resources, meeting the strict requirements of single-stage micro inverters in wave generation, sampling, and loop control, ensuring stable operation of single-stage micro inverters under complex working conditions.

Full link control architecture and system level optimization design

Zhaoyi innovates 500W single-stage micro inverse control scheme

In the system control architecture, the GD32G553 MCU serves as the core control unit, responsible for functions such as PWM generation, signal sampling, and loop control. The secondary power conversion part adopts nano micro bidirectional BDS GaN power devices. The entire control loop is as follows: first, the maximum power point tracking (MPPT) algorithm is used to calculate the PV voltage reference value, and the dynamic tracking of the PV voltage reference value is achieved through the voltage loop controller; The results obtained from the voltage loop calculation are combined with the phase information of the grid voltage extracted by the SOGI PLL phase-locked loop and the given reactive phase information to provide current reference for the feedforward controller and current loop controller. Finally, the primary and secondary phase shift control quantities are calculated and converted into actual driving pulses through a high-precision timer module, achieving precise control of the power circuit.

In the MCU implementation process, the control algorithm mainly consists of four parts: phase-locked loop, feedforward compensation, closed-loop control, and phase shift conversion. The execution time of these parts was tested, and the results showed that the GD32G553 controller exhibited good computing performance.

Through system level optimization, the entire solution has the characteristics of high efficiency, high-quality grid connection, and high integration: at a switching frequency of 100kHz, it achieved a peak efficiency of 97.5% and a CEC weighted efficiency of 97%, with an MPPT efficiency of 99.9%; Under the condition of 500W, THD is 3.2% and PF is 0.999.

Firstly, in terms of high efficiency and low loss. All switch tubes can achieve ZVS, significantly reducing switch losses; By optimizing the hybrid modulation strategy, the soft switching range has been expanded; Reducing the reflux power and effective value of transformer current, reducing conduction losses; Simultaneously using nano BDS GaN to reduce switching losses.

Secondly, in terms of high-quality grid connection. The feedforward control of this scheme can improve the power response speed and enhance the tracking effect on the grid voltage; Closed loop Q-PR control can track AC signals without static error, improving the quality of grid connected current. At the same time, by coordinating the adjustment of phase shift control variables between the primary and secondary sides, interference free switching between modes is achieved, thereby smoothing the transformer current and grid connected current.

Finally, in terms of high integration and cost optimization. The scheme adopts the magnetic integration technology of a transformer with a single integrated inductor, achieving a reduction in the volume of magnetic components, and uses bidirectional BDS GaN to meet the demand for bidirectional switches on the AC side, further reducing the size and overall BOM cost of the scheme.

Create a rich product matrix and build a high-quality ecosystem

In the field of new energy control, Zhaoyi Innovation has built a MCU product matrix covering all scenarios, which is widely used in photovoltaic circuit breakers, optimizers, AI arc detection, energy storage ESS systems BMS、 Inverter, HMI communication monitoring and other product applications. In arc detection, optimizer Bi DC-DC、 For the industrial and commercial storage BMS and other parts, Zhaoyi Innovation also provides complete solutions for customers to use directly or for secondary development, which can significantly reduce the research and development cycle. In terms of power control, Zhaoyi Innovation has 600MHz high-frequency GD32H7 series and 216MHz GD32G5 series MCUs for customers to choose from.

The GD32G553 used in this scheme belongs to the GD32G5 series MCU of Zhaoyi Innovation. This series has excellent computing power and uses Arm?  Cortex? -M33 core, with a clock speed of up to 216MHz, built-in single precision floating-point unit (FPU), as well as hardware trigonometric function accelerator (TMU) and various other hardware acceleration units. These features significantly improve data processing speed and complex computing capabilities. At the same time, the GD32G5 series MCU can support high-precision PWM output for up to 16 channels, with a resolution of up to 145ps. It can support wave generation methods such as variable duty cycle, frequency conversion, and phase shifting.

In addition to its advantages in computing power and wave control, GD32G553 also supports four 12 bit ADC modules with a sampling rate of up to 5.3MSPS. It can support up to 42 sampling channels and efficiently collect and process signals from various sensors. At the same time, GD32G553 is equipped with 8 CMPs (on-chip comparators), which have the characteristics of fast response and flexible configuration. Its output signal can be directly connected to HRTIMER internally to achieve PWM blocking or switching.

In addition to creating high-performance products, Zhaoyi Innovation also strengthens ecological construction. The joint research and development laboratory of Zhaoyi Innovation and Nano Micro Semiconductor integrates Zhaoyi Innovation's high computing power MCU with the high-frequency and efficient GaN technology of Nano Micro Semiconductor to create intelligent and efficient digital power products, providing customers with more solution choices. At the same time, in conjunction with the ecosystem of the entire industry chain of Zhaoyi Innovation and the profound understanding of nanomicro system applications, we will accelerate our layout in fields such as AI data centers, photovoltaic inverters, energy storage systems, charging piles, and electric vehicles.

This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry

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