The design features a two-channel string inverter with full bidirectional power. It combines PV inputs and battery storage and supports up to 10kW output.
As demand for photovoltaic systems rises, inverters are becoming increasingly crucial in making solar energy more accessible for residential use and advancing the transition to renewable energy. String inverters, known for their modularity, low cost-per-watt, and easy scalability to achieve higher power levels, are particularly well-suited for the single-phase market. Hybrid string inverters enhance this setup by adding energy storage capabilities, maximizing power utilization from photovoltaic inputs, and providing an alternative means to supply the grid during nighttime or periods of low sunlight. These inverters integrate photovoltaic panel power point tracking with an inverter stage and bidirectional functionality to incorporate a battery stage, necessitating higher power density and efficiency. Gallium Nitrate (GaN) Field-Effect Transistors (FETs) significantly enhance these systems by supporting high switching frequencies that allow for smaller electromagnetic interference (EMI) filters and heat sinks, thus making the systems more compact and lightweight while improving the design’s form factor.
The reference design from Texas Instruments (TI) demonstrates the implementation of a two-channel single-phase string inverter with fully bidirectional power flow, combining photovoltaic input functionality with a Battery Energy Storage System (BESS) that supports a wide range of battery voltages. It includes two string inputs, each capable of supporting up to 10 photovoltaic (PV) panels in series, and one port for an energy storage system that accommodates battery stacks from 50V to 500V. The system can deliver up to 10kW from the string inputs to the BESS. The configurable DC-AC converter is designed to supply up to 4.6kW to a single-phase grid at 230V. Control over the three power stages is managed through a single C2000 MCU.
Applications of this technology include string inverters and power conversion systems (PCS). These are critical components in transforming and regulating electrical power for various uses. String inverters efficiently convert the direct current (DC) produced by photovoltaic (PV) panels into alternating current (AC) suitable for residential and commercial grids. At the same time, power conversion systems manage the flow and quality of electricity, ensuring compatibility and stability in energy systems.
The features of this system encompass a bidirectional DC/DC stage that can be configured for a wide range of battery voltages and a configurable DC/AC stage that supports various modulation schemes, including HERIC, H-Bridge Unipolar, and Bipolar. The system achieves a 2× improvement in power density, enhancing the portability of solar inverters with a density of 2.5kW/L, making them lighter and easier to install. It also boasts low total losses of less than 2%, which maximizes solar energy capture and improves the efficiency of battery energy storage. The control of the entire board is managed through a unique MCU, optimizing costs as the MCU ground. This configuration allows non-isolated drives on all GaN devices to streamline the design and reduce complexity.
TI has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
