Design of Photovoltaic/Wind Energy Complementary DC Operating Power Supply System
1. Overall Architecture of PV/Wind Energy Complementary DC Operating Power Supply System
1.1 Energy Collection Layer: PV and Wind Energy Acquisition
PV Module Configuration: Select high-efficiency monocrystalline silicon PV modules with photoelectric conversion efficiency ≥24%, adapting to different light intensity conditions. The module power is determined according to local solar radiation resources and load demand, generally 200W~400W per piece. For outdoor scenarios, adopt anti-reflection, anti-aging, and dust-proof coated modules, and install them with an optimal inclination angle (calculated based on local latitude, generally 30°~45°) to improve power generation efficiency. The PV array is connected in series-parallel combination to match the rated voltage of the system.
Small Wind Turbine Configuration: Select horizontal-axis wind turbines for medium and high wind speed areas, and vertical-axis wind turbines for low wind speed and turbulent wind areas, with rated power ranging from 1kW~10kW. The turbine is equipped with a wind speed sensor and a yaw control system, which can automatically start at wind speed ≥3m/s, stop at wind speed ≥25m/s, and adjust the direction to face the wind, ensuring safe and efficient power generation. The generator adopts permanent magnet synchronous type, with high power density and conversion efficiency ≥90%.
1.2 Power Conversion Layer: Energy Conversion and Regulation
MPPT Controller: Configure a dedicated maximum power point tracking (MPPT) controller for the PV array, with tracking efficiency ≥99%. It dynamically adjusts the working parameters of the PV array according to light intensity and temperature changes, ensuring that the PV system operates at the maximum power point at all times, improving energy utilization by 15%~20% compared with traditional controllers. The controller supports parallel operation to adapt to large-capacity PV arrays.
Wind Energy Rectifier Module: Convert the AC power output by the wind turbine into DC power through a three-phase full-bridge rectifier. The module is equipped with a voltage stabilization circuit and a filter circuit, which can suppress voltage fluctuations caused by wind speed changes, ensuring that the output DC voltage ripple coefficient ≤0.5%. It also has overcurrent, overvoltage, and overtemperature protection functions.
DC/DC Converter: Uniformly adjust the DC power output by PV and wind energy to the rated voltage of the system (110V or 220V DC). The converter adopts bidirectional design, which can not only convert and boost the energy of new energy sources but also realize the charging and discharging control of the energy storage system, with conversion efficiency ≥98.5% under full load.
1.3 Energy Storage Layer: Energy Storage and Backup
Energy Storage Battery Selection: Adopt lithium iron phosphate (LFP) batteries with high safety, long cycle life (≥6000 cycles), and high energy density. The battery pack voltage is matched with the system rated voltage, and the capacity is determined according to the load power and backup time requirements—generally ensuring 8~24 hours of continuous power supply for critical loads. The battery pack is equipped with a dedicated battery management system (BMS) to monitor battery voltage, temperature, SOC (State of Charge), and internal resistance in real time, realizing balanced charging and discharging and preventing thermal runaway.
Auxiliary Energy Storage (Optional): For scenarios with high stability requirements, configure flywheel energy storage as auxiliary backup. Flywheel energy storage has fast response speed (millisecond level) and long service life, which can make up for the short-term power gap caused by sudden changes in wind speed or light intensity, further improving the stability of the system.
1.4 Control & Distribution Layer: Intelligent Control and Power Distribution
Central Control Unit (CCU): Adopt DSP digital control chip and embedded system, integrating PV/wind energy coordination control, energy storage charging/discharging control, and load management functions. It realizes real-time data collection and analysis of each module, and dynamically adjusts the power supply ratio of PV, wind energy, energy storage, and mains (backup) through intelligent algorithms.
DC Distribution Screen: Distribute the stable DC power to various operating loads (such as relay protection devices, monitoring equipment, and actuators) through separate loops. Each loop is equipped with DC circuit breakers and fuses for overcurrent and short-circuit protection. The distribution screen adopts top-in and top-out wiring mode, with insulated busbars (brown for positive pole, blue for negative pole) to ensure safe operation. The maximum voltage drop of the screen under full load shall not exceed 1V.
Intelligent Monitoring System: Realize real-time monitoring of PV power generation, wind power generation, battery SOC, load status, and equipment operating parameters through RS485/Modbus communication protocol. The system supports remote monitoring, fault alarm, and parameter adjustment, and can generate energy consumption statistics and power generation reports, providing data support for system operation and maintenance.
2. Core Design Points of the Complementary System
2.1 PV/Wind Energy Complementary Matching Design
Resource Assessment: Conduct a one-year on-site investigation of local solar radiation, wind speed, and seasonal changes. For areas with sufficient sunlight in summer and abundant wind in winter, the PV/wind capacity ratio is generally 1.2~1.5:1; for areas with balanced light and wind resources, the ratio is 1:1.
Power Matching Calculation: The total installed capacity of PV and wind energy shall be ≥1.5 times the rated load power, considering the power loss of conversion modules and transmission lines. The energy storage capacity shall be calculated according to the maximum continuous no-energy generation time (such as 3 days of continuous cloudy and windless weather) to ensure load supply.
2.2 Energy Storage System Matching Design
Capacity Matching: The energy storage capacity is determined by the formula: E = P_load × T_backup × K_factor, where P_load is the rated load power, T_backup is the required backup time, and K_factor is the safety factor (1.2~1.5). For example, for a 10kW load requiring 24 hours of backup, the energy storage capacity shall be ≥10×24×1.2=288kWh.
Charging/Discharging Strategy: Set the charging/discharging threshold of the battery pack through BMS: when the battery SOC ≥90%, stop charging and feed surplus energy to the grid (subject to local policy); when SOC ≤20%, start mains backup power supply to avoid over-discharging and extend battery life.
2.3 Safety Protection Design
Overvoltage/Undervoltage Protection: When the DC busbar voltage exceeds the rated range (±10%), the CCU immediately cuts off the connection between new energy sources and the busbar, and switches to energy storage or mains backup.
Lightning Protection Design: Install a DC surge protector (SPD) at the input end of PV arrays, wind turbines, and distribution screens, with a protection level of ≥20kA. The entire system adopts a unified grounding system, with grounding resistance ≤4Ω, to prevent lightning damage to equipment.
Insulation Monitoring: Configure an insulation monitoring device to real-time monitor the insulation resistance between the DC busbar and ground. When the resistance is lower than 2MΩ, an alarm is issued immediately, and the faulty loop is isolated to avoid short circuit.
Weather Adaptation Protection: The wind turbine is equipped with a storm protection device, which can automatically fold the blades when the wind speed exceeds the limit; the PV modules adopt IP67 protection level, adapting to rain, snow, and dust environments.
2.4 Wiring and Cabling Design
The wiring of PV arrays and wind turbines shall adopt flame-retardant shielded cables (complying with YD/T 1173—2001) to reduce electromagnetic interference and ensure transmission safety. The cross-sectional area of cables shall be selected according to the current-carrying capacity, with a voltage drop ≤3%.
Cables between outdoor equipment and indoor distribution screens shall be laid through cable trenches or protective pipes, avoiding direct exposure to sunlight. The connection points shall be wrapped with waterproof insulation tape to prevent water ingress.
The DC distribution screen shall be installed in a dry, well-ventilated area, with a distance of ≥50cm from surrounding objects to facilitate heat dissipation and maintenance.
3. Intelligent Control Strategy of the Complementary System
3.1 Local Control Strategy
MPPT Control: The PV MPPT controller tracks the maximum power point in real time, and the wind energy controller adjusts the turbine speed according to wind speed to maximize power generation efficiency.
Battery Charging/Discharging Control: The BMS adopts constant current-constant voltage (CC-CV) charging mode to avoid overcharging; during discharging, it adjusts the discharge current according to the load demand, ensuring battery stability.
3.2 Centralized Scheduling Strategy
New Energy Priority Mode (Normal Condition): When PV and wind energy power generation is sufficient, prioritize using new energy to supply power to loads, and charge the energy storage system with surplus energy. The CCU dynamically adjusts the power distribution ratio to keep the battery SOC between 30%~80%.
Energy Storage Supplementary Mode (Insufficient New Energy): When PV/wind energy power generation is less than the load demand, the energy storage system discharges to supplement the power gap, ensuring stable load power supply. The CCU adjusts the discharge rate according to the battery SOC to avoid over-discharging.
Mains Backup Mode (New Energy and Energy Storage Insufficient): When the battery SOC drops to 20%, the CCU automatically switches on the mains backup power supply (through a bidirectional inverter), ensuring continuous power supply for critical loads. Mains power also charges the energy storage system until SOC reaches 50%.
Fault Handling Mode: When PV, wind energy, or energy storage system fails, the CCU immediately isolates the faulty module, and adjusts the remaining energy sources to supply power to loads, ensuring that the fault does not affect the overall system operation.
4. Typical Application Case
4.1 Rural Substation PV/Wind Complementary DC Operating Power Supply System
System Configuration: 5kW PV array (20 pieces of 250W monocrystalline silicon modules), 3kW horizontal-axis wind turbine, 100kWh lithium iron phosphate battery pack, 5kW bidirectional DC/DC converter, and 110V DC distribution screen. The PV/wind capacity ratio is 1.67:1, adapting to the local climate characteristics of sufficient sunlight in summer and strong wind in winter.
Application Effects: The system realizes annual power generation of about 12,000 kWh, with a new energy utilization rate of 85%. It supplies power to substation relay protection devices, monitoring systems, and lighting loads (total rated power 2kW), and the energy storage system provides 24 hours of backup power. The system reduces carbon emissions by about 9.6 tons per year compared with traditional mains power supply, and the annual power cost is reduced by more than 8,000 yuan. During extreme weather such as sandstorms and blizzards, the system switches to energy storage and mains backup mode, ensuring stable operation of the substation.
5. Operation and Maintenance and Optimization Suggestions
5.1 Daily Operation and Maintenance
Clean PV modules quarterly to remove dust, bird droppings, and other debris, ensuring photoelectric conversion efficiency. Check the wind turbine blades and yaw system semi-annually for wear and looseness.
Monitor the battery SOC, temperature, and internal resistance through the BMS monthly, and perform balanced charging when the voltage difference between battery cells exceeds 0.1V. Replace aging battery modules when the capacity decays to 80% of the rated capacity.
Test the insulation resistance and grounding resistance of the system annually, and calibrate the MPPT controller and monitoring equipment to ensure measurement accuracy.
5.2 Optimization Suggestions
Intelligence Upgrade: Introduce AI algorithms to predict PV/wind energy power generation and load demand in the next 24 hours, optimizing the scheduling strategy and improving energy utilization.
New Energy Integration: Connect the system to the local microgrid, realizing surplus energy grid-connected power generation and improving the economic benefits of the system.
Material Upgrade: Adopt high-efficiency PV modules and wind turbines with higher conversion efficiency, and use graphene batteries to improve energy storage density and cycle life.