The efficiency of solar inverters directly affects the overall power generation and economy of photovoltaic power generation systems. Improving its efficiency requires comprehensive optimization from multiple dimensions such as circuit design, component selection, heat dissipation management, and control strategies. The following are specific methods for improvement:
1、 Optimize circuit topology structure
Circuit topology is the foundation of inverter efficiency, and a reasonable structure can reduce energy loss:
Adopting high-frequency design
High frequency transformers and inductors have smaller volumes, which can reduce magnetic core losses (such as eddy current losses and hysteresis losses), while also reducing parasitic parameters (resistance, capacitance) in the circuit and reducing reactive power consumption.
For example, high-frequency isolated inverters (such as LLC resonant topology) can increase efficiency by 2% -5% compared to traditional power frequency transformer topologies.
Select efficient topology type
Single phase low-power inverters can adopt push-pull, half bridge, or full bridge topologies to avoid unnecessary switching actions; High power three-phase inverters commonly use three-level topologies (such as NPC topologies), which have low voltage stress on the switching tubes and low switching losses.
Transformer free topology (non isolated type) can reduce magnetic core losses, but safety measures such as insulation design need to be taken, making it suitable for cost sensitive scenarios.
Reduce energy conversion steps
For example, string inverters directly invert the DC voltage of photovoltaic panels into AC, reducing losses in the combiner link compared to centralized inverters; Micro inverters (component level) avoid efficiency losses caused by string mismatch.
2、 Improve the performance of power devices
Power devices (such as IGBT and MOSFET) are the core of inverters, and their losses account for 30% -50% of the total losses:
Select low loss components
Priority should be given to wide bandgap semiconductor devices such as SiC MOSFETs and GaN HEMTs. Compared to traditional silicon-based devices (IGBTs), they have lower on resistance and faster switching speed, which can reduce on and off losses (especially under high-frequency conditions) and increase efficiency by 1% -3%.
For example, the switching loss of SiC devices is only 1/10 of that of silicon-based IGBTs, making them suitable for high temperature and high frequency environments.
Optimize device parameter matching
Select devices with appropriate voltage and current specifications based on the power level of the inverter to avoid excessive conduction losses caused by "pulling a cart with a big horse" or efficiency degradation caused by device overload.
Paired with low on resistance freewheeling diodes (such as fast recovery diodes FRD) to reduce reverse recovery losses.
3、 Improve control and modulation strategies
By optimizing algorithms, reduce switch actions and reactive power losses, and improve dynamic response efficiency:
Optimize PWM modulation technology
Using space vector pulse width modulation (SVPWM) instead of traditional sine pulse width modulation (SPWM) can improve the utilization rate of DC voltage by about 15%, reduce the number of switching times, and lower switching losses.
Introducing soft switching technologies such as zero voltage switching (ZVS) and zero current switching (ZCS) to enable switching transistors to switch at zero voltage or current, almost eliminating switching losses (especially suitable for high-frequency inverters).
Dynamically adjust the working mode
Automatically switch to intermittent working mode (such as variable frequency control) during light load to reduce ineffective actions of the switch tube; Maintain high-frequency stable output during overload, balancing efficiency and stability.
By combining maximum power point tracking (MPPT) algorithm optimization (such as improved perturbation observation method and particle swarm optimization algorithm), the maximum power point of photovoltaic panels can be quickly tracked, reducing energy loss caused by changes in light/temperature (MPPT efficiency needs to reach over 99%).
4、 Enhanced heat dissipation design
The efficiency of power devices significantly decreases with increasing temperature (for example, for every 10 ℃ increase in IGBT junction temperature, the loss increases by about 10%)
Optimize the heat dissipation structure
Adopting heat pipe heat dissipation, liquid cooling heat dissipation (high-power inverter) or large-area aluminum heat dissipation fins (low-power) to increase the heat dissipation area and reduce thermal resistance (target: device junction temperature controlled below 80 ℃).
Reasonably layout components, keep devices with high heat generation (IGBT, inductor) away from sensitive components, and avoid local high temperatures.
Intelligent temperature controlled fan
The fan dynamically adjusts its speed according to the temperature of the device (such as PWM speed regulation), and stops or runs at low speed at low temperatures to reduce fan power consumption (especially suitable for household low-power inverters).
5、 Reduce auxiliary circuit losses
Although auxiliary circuits (such as drive circuits and sampling circuits) have low power consumption, the accumulated losses during long-term operation cannot be ignored:
Efficient driving circuit
Using integrated driver chips (such as IR2110) to reduce drive signal delay and distortion, and lower the power consumption of the drive circuit itself; Match the driving voltage and current with the requirements of the switching transistor to avoid over driving or under driving.
Low power sampling and protection circuit
Select high-precision and low-power current/voltage sensors (such as Hall sensors and shunt resistors) to reduce energy consumption in the sampling process; The protection circuit (overcurrent, overvoltage) adopts a fast response design to avoid additional losses in case of faults.
6、 System level optimization
Matching photovoltaic array characteristics
The input voltage range of the inverter is matched with the working voltage of the photovoltaic panel (such as a string inverter adapted to 2-4 photovoltaic panels in series), to avoid the inverter working in the low efficiency zone due to low voltage.
Multi MPPT design (such as 1 MPPT per 2-channel string) reduces mismatch losses caused by shadows and component aging (mismatch can reduce efficiency by 5% -10%).
Reduced Rating Design and Reliability
The inverter has the highest efficiency when it operates at 70% -80% of its rated power for a long time. When designing, a 10% -20% power margin is reserved to avoid efficiency decline caused by full load operation; At the same time, reliability testing (such as high and low temperature cycling, vibration testing) is conducted to reduce downtime losses caused by faults.
summarize
Improving the efficiency of solar inverters requires collaborative optimization of "hardware+software+system": wide bandgap devices and efficient topologies are used in hardware, modulation and MPPT algorithms are optimized in software, and photovoltaic characteristics are matched and heat dissipation is controlled at the system level. At present, the efficiency of mainstream inverters has reached 96% -98%. In the future, through the popularization of SiC/GaN devices and digital twin control technologies, the efficiency is expected to exceed 99%, further reducing the cost of photovoltaic power generation.
