Cost-Effective Wind-Solar Hybrid Solution: Buck-Boost Converter & Smart Charging Reduce System Cost

Abstract​

This solution proposes an innovative high-efficiency wind-solar hybrid power generation system. Addressing core shortcomings in existing technologies—such as low energy utilization, short battery lifespan, and poor system stability—the system employs fully digitally controlled buck-boost DC/DC converters, interleaved parallel technology, and an intelligent three-stage charging algorithm. This enables Maximum Power Point Tracking (MPPT) over a wider range of wind speeds and solar irradiation, significantly improving energy capture efficiency, effectively extending battery service life, and reducing the overall system cost.

​1. Introduction: Industry Pain Points & Existing Deficiencies​

Traditional wind-solar hybrid systems suffer from significant drawbacks that limit their widespread application and cost-effectiveness:

• ​Narrow Voltage Input Range:​​ Systems typically use simple buck converters, which can only charge the battery when the voltage generated by the wind turbine or solar panels exceeds the battery voltage. Under low wind or weak light conditions, the generated voltage is insufficient, leading to wasted renewable energy.
• ​Severe Energy Waste:​​ When wind or solar energy is abundant, traditional systems often use resistive braking (dummy loads) to dissipate excess electrical energy as heat to prevent battery overcharging, resulting in significant energy waste.
• ​Short Battery Lifespan:​​ Due to the aforementioned insufficient energy capture and imperfect overcharge protection mechanisms, batteries often remain in a state of undercharge or overcharge, drastically reducing their cycle life and increasing maintenance costs.
• ​Low Control Precision & Poor Stability:​​ Most systems employ simple control strategies, lacking precise voltage and current regulation, leading to unstable power quality. To ensure reliable load operation, larger capacity generation and storage equipment are often required, increasing initial investment.

​2. Core Components of the Solution​

This system consists of 11 core components working synergistically to form an intelligent, efficient energy capture, storage, and distribution network.

​3. Core Technical Advantages​

​3.1 Buck-Boost DC/DC Converter with Wide Input Voltage Range​

• ​Core Technology:​​ Both wind and solar converters utilize a Buck-Boost DC/DC topology.
• ​Pain Point Solved:​​ Overcomes the voltage limitations of traditional buck converters.
• ​Low Input Voltage (Boost Mode):​​ When wind speed is below rated value (rpm < ω₀) or light is insufficient, and generated voltage is below battery voltage, the converter automatically operates in Boost mode to raise the voltage for charging.
• ​High Input Voltage (Buck Mode):​​ When wind/solar resources are abundant and generated voltage exceeds battery voltage, the converter automatically switches to Buck mode for charging.
• ​Two Implementation Schemes:​​
• ​Cascaded Buck-Boost DC/DC:​​ Uses 2 power switches for separate boost/buck control; offers high precision, suitable for high-performance scenarios.
• ​Basic Buck-Boost DC/DC:​​ Uses 1 power switch controlled by a single PWM duty cycle (<50% Buck, >50% Boost); simpler structure, lower cost.

​3.2 Interleaved Parallel Control (Key Innovation)​​

• ​Technical Principle:​​ The digital controller drives the PWM signals for two parallel DC/DC converters with a 180-degree phase shift, unlike traditional in-phase parallel operation.
• ​Technical Effects:​​
• ​Reduced Ripple:​​ Output current ripples cancel each other, significantly reducing the peak-to-peak value of the total ripple current, providing cleaner, more stable DC power to the load.
• ​Doubled Frequency, Reduced Losses:​​ The ripple frequency of the total output current becomes twice the switching frequency of a single converter, allowing the use of a lower switching frequency to meet ripple requirements, thereby reducing switching losses and improving overall system efficiency.

​3.3 Intelligent Three-Stage Charging Mode​

The digital controller dynamically adjusts the charging strategy based on the battery's State of Charge (SOC), achieving an optimal balance between efficiency and protection:

​3.4 Fully Digital Intelligent Control​

Centered on a high-performance MCU or DSP, the system collects real-time voltage and current data from the wind turbine, solar panels, and battery. Using embedded algorithms, it:

• Performs real-time MPPT calculations to ensure optimal energy capture.
• Intelligently determines and switches charging modes.
• Precisely generates PWM signals to drive the converters and implement interleaved control.

​4. Benefits and Scalability​

​4.1 Core Technical Benefits​

1. ​Greatly Enhanced Resource Utilization:​​ The wide input voltage range allows the system to harness low-grade energy (e.g., light breezes, dawn/dusk weak light) that traditional systems cannot capture, significantly broadening the usable range of wind and solar energy.
2. ​Significantly Improved System Efficiency:​​ The MPPT algorithm ensures generating units operate at their optimal power point. Combined with reduced losses from interleaving technology, the overall system energy efficiency far exceeds that of traditional solutions.
3. ​Substantially Extended Battery Life:​​ The intelligent three-stage charging algorithm effectively prevents overcharging and deep discharge, increasing battery cycle life by over 50% and significantly reducing maintenance and replacement costs.
4. ​Reduced Comprehensive System Cost:​​ Enhanced power supply stability eliminates the need for over-sizing generation and storage capacity for reliability, reducing initial investment.
5. ​High Output Power Quality:​​ Interleaving technology provides low-ripple, highly stable DC output, protecting sensitive loads and improving power supply quality.

​4.2 Flexible Capacity Expansion Scheme​

The system offers excellent scalability for flexible capacity increases based on demand:

• ​Component-Level Expansion:​​ The inputs of two DC/DC converters can be connected in parallel to the same solar panel or wind turbine. The digital controller provides unified interleaved control, doubling the peak output power for that particular source (solar or wind).
• ​System-Level Expansion:​​ Expanded solar and wind power units are connected in parallel on the DC bus to easily supply power to larger battery banks and loads. All control units are interconnected via communication interfaces (e.g., CAN bus) for centralized monitoring and management.