1. Battery Lifespan

　　At Wind-Solar Hybrid Power Generation In the system, power generation and load cannot be synchronized. When power generation falls short of demand, it becomes necessary to supply additional electricity—this is where batteries come in. However, due to the unpredictable nature of wind and solar resources, there’s often an imbalance between power output and electricity consumption. Moreover, power generation is heavily influenced by weather conditions. If the weather turns unfavorable, the battery pack may quickly deplete its stored energy, ultimately shortening the battery’s lifespan. On top of that, batteries involve relatively high upfront investment costs, and replacing them can significantly increase operational expenses. Therefore, extending the lifespan of the battery is essential, and the following solutions can help address this issue:

　　(1) Continuous Float Charging Method. The battery pack operates in three modes: cyclic charge-discharge, continuous float charging, and periodic float charging. In the continuous float-charging mode, the batteries remain charged for an extended period—typically 2 to 3 times longer than during cyclic charging. However, if the batteries are left in a float-charging state for too long, the activity of free substances in the electrolyte can decline, leading to voltage instability. Therefore, it’s necessary to apply a small overcurrent pulse of 1 to 3 hours to rebalance the batteries and counteract this adverse effect.

　　(2) A new type of charging control system. The charging process for batteries is nonlinear, and charging overshoot can be effectively managed through intelligent control methods, such as fuzzy logic and adaptive control techniques. Smart charging not only meets the protection requirements against overcurrent and overdischarge but also ensures timely replenishment of power. Fuzzy control, in particular, helps minimize errors in current regulation.

　　2. Fan Speed Limit Protection

　　Small-scale off-grid systems rely on high-wind-speed protection mechanisms when the wind turbine’s input exceeds the combined capacity of system consumption and energy storage. At this point, it becomes essential to reduce the turbine’s absorption of wind energy to prevent it from spinning too fast. Currently, the primary method for limiting turbine speed is mechanical speed-limiting protection; however, this type of safeguard suffers from low reliability—both due to improper design and inherent limitations. Wind conditions in nature are highly complex, with turbulence being the most prominent feature, often causing frequent and unpredictable fluctuations in wind speed. No mechanical device can respond swiftly enough to these real-time changes, leading to prolonged wear and tear over time. This, in turn, diminishes the coordination between components, resulting in delayed or ineffective protection actions—and in severe cases, even causing turbine overload and vibration. To address these challenges, magnetic-electric speed-limiting devices can be employed to subtly reduce the wind turbine’s energy capture efficiency, effectively slowing down the rotor while ensuring a more reliable and secure protective response.

　　3. Accuracy of System Performance

　　Typically, people are more enthusiastic about developing a straightforward design approach for photovoltaic systems and their complementary power generation systems, yet they often overlook the accuracy of system performance predictions. Some studies have focused on how meteorological characteristics influence system performance, simulating system behavior and exploring the relationship between time-dependent parameters and system configurations. However, the mathematical models used in these simulations tend to be overly simplistic, and loads are usually assumed to remain constant—limitations that significantly narrow the applicability of the derived formulas. Moreover, there is a clear need to refine the characterization components used to determine system operating conditions, as well as to enhance the mathematical models designed to accurately assess real-world wind and solar energy resources.