The efficiency of solar inverters is closely related to heat management - when the internal power devices (such as IGBT, MOSFET) of the inverter have high temperatures, it can cause increased conduction losses, switching losses, and even trigger overheating protection shutdown. Therefore, scientific heat dissipation design is the core measure to improve the efficiency and prolong the service life of inverters. The following provides a detailed introduction to feasible heat dissipation management solutions from four dimensions: optimization of heat dissipation structure, upgrading of heat dissipation materials, intelligent temperature control strategy, and system integration design:
1、 Optimize heat dissipation structure: reduce heat transfer resistance
The core goal of the heat dissipation structure is to construct a low resistance channel for "device heat generation → internal conduction → external dissipation", reducing the accumulation of heat inside the inverter. Common optimization directions include:
1. Reasonable layout of internal components
The layout of the internal heat source (power module, inductor, transformer) and heat dissipation components (radiator, fan) of the inverter directly affects the heat dissipation efficiency, and the principle of "heat source close to the heat dissipation end and avoiding heat superposition" should be followed:
Concentrated arrangement of heat sources: Concentrate the main heat generating components such as IGBT modules and rectifier bridges (accounting for 60% -80% of the total heat generation) in the area near the heat sink to shorten the heat conduction path;
Avoid thermal interference: Keep temperature sensitive components such as capacitors and control circuit boards away from heat sources (such as distance ≥ 5cm from power modules), while avoiding "thermal superposition" between heat sources (such as inductors and transformers not arranged adjacent to each other);
Reserved ventilation gap: Adequate gap (usually ≥ 10mm) should be reserved in the internal air duct to ensure smooth flow of cold air through the heat source area and avoid the formation of "dead zones" (local high temperatures caused by stagnant air).
2. Upgrade the radiator design
The radiator is the core component of passive heat dissipation in inverters, and its structural optimization can significantly improve the heat dissipation capacity
Adopting profile/plug-in heat sink: Compared with traditional flat heat sinks, profile heat sinks (such as aluminum alloy extruded) have denser heat dissipation fins and larger surface area (heat dissipation area can be increased by 30% -50%), and the fin direction is consistent with the air duct, reducing wind resistance;
Optimize fin parameters: The spacing between fins should match the wind speed of the air duct (when the wind speed is 1-3m/s, the optimal spacing is 8-12mm) - a spacing that is too small is prone to dust accumulation and blockage, while a spacing that is too large will result in insufficient heat dissipation area; The height of the fins should be controlled between 30-80mm (excessively high will increase wind resistance, while excessively low will limit heat dissipation capacity);
Localized enhanced heat dissipation: In the "hotspot area" where the IGBT module contacts the heat sink, a "convex design" (locally thickening the heat sink base) is adopted to reduce the contact thermal resistance (thermal resistance can be reduced by 15% -20%).
3. Optimize air duct design (forced air cooling scenario)
For medium to high power inverters (≥ 50kW), forced air cooling is the mainstream solution, and the air duct design needs to achieve "smooth air path and uniform air volume":
Forward rear/side inlet/side outlet air duct: adopts a "one-way air duct" (to avoid air backflow), the inlet is equipped with a dust-proof net (to reduce the decrease in heat dissipation efficiency caused by dust accumulation), and the outlet avoids direct sunlight;
Design of diversion structure: Add diversion plates in the air duct to guide the cold air to flow through the main heat sources such as IGBT and transformer first, avoiding "ineffective ventilation" (direct discharge of cold air without contact with the heat source);
Sealing optimization: Ensure a good seal between the air duct and the inverter casing (such as using sponge sealing strips) to prevent external hot air from infiltrating, while avoiding internal cold air leakage (leakage rate should be controlled within 5%).
2、 Upgrading heat dissipation materials: improving heat conduction efficiency
The thermal conductivity of heat dissipation materials directly determines the speed of heat transfer from the "device" to the "heat sink" and then to the "environment". The key material upgrade directions are as follows:
1. Thermal conductive material between power devices and heat sinks
The thermal conductivity of traditional thermal pads/silicone grease is relatively low (1-3W/(m · K)), which cannot meet the heat dissipation needs of high-power devices. They can be replaced with:
High thermal conductivity gasket: such as graphene thermal conductivity gasket (thermal conductivity 10-20W/(m · K)), metal based thermal conductivity gasket (such as copper based gasket, thermal conductivity 300+W/(m · K)), pay attention to the compression amount of the gasket (usually 5% -15%), ensure a tight fit with the device and heat sink (contact thermal resistance ≤ 0.1 ℃· cm ²/W);
Phase change thermal conductive material: When the temperature reaches the phase change point (such as 50-70 ℃), it changes from solid to liquid, filling the small gap between the device and the heat sink. The contact thermal resistance can be reduced to below 0.05 ℃· cm ²/W, suitable for high-temperature devices such as IGBT.
2. Upgrade of radiator substrate
Traditional heat sinks often use 6063 aluminum alloy (with a thermal conductivity of 201W/(m · K)), which can be upgraded to materials with higher thermal conductivity:
High thermal conductivity aluminum alloy: such as 6061-T6 (thermal conductivity 230W/(m · K)), or alloys with added copper and zinc (thermal conductivity 250+W/(m · K)), can increase heat dissipation capacity by 15% -25% under the same volume;
Copper aluminum composite radiator: The radiator base is made of copper (with a thermal conductivity of 401W/(m · K)), and the fins are made of aluminum alloy (to reduce costs). Through brazing or friction welding composite, it balances high thermal conductivity and lightweight (reducing weight by 40% compared to pure copper radiators).
3. Shell and heat dissipation coating
The inverter casing not only provides protection, but also assists in heat dissipation:
Using thermal conductive shell materials, such as aluminum alloy shell (instead of plastic shell), the thermal conductivity is increased by more than 1000 times, and internal heat can be conducted to the environment through the shell;
Spray heat dissipation coating: Spray a high emissivity coating (such as ceramic based coating, emissivity ≥ 0.9) on the outer surface of the shell to enhance heat dissipation through "thermal radiation" (especially in windless environments, the proportion of radiative heat dissipation can be increased to 30%).
1. Multi temperature point linkage control
Install NTC thermistors or thermocouples at key locations inside the inverter (IGBT module, transformer, inductor) to collect real-time temperature data and control the cooling equipment according to a "grading strategy":
Low temperature range (T ＜ 40 ℃): Turn off the fan and rely solely on passive heat dissipation (radiator+casing) to reduce fan energy consumption;
Medium temperature range (40 ℃≤ T ＜ 60 ℃): Start the fan and run it at low speed (such as 1000-1500rpm) to maintain temperature stability;
High temperature range (T ≥ 60 ℃): The fan runs at high speed (such as 2000-3000rpm). If the temperature continues to rise to the protection threshold (such as 85 ℃), the fan will operate at a reduced power output to avoid overheating and shutdown.
2. Load prediction type temperature control
In combination with the "intermittent" characteristics of solar power generation (such as strong light at noon, high load, low load in the morning and evening), the cooling strategy is adjusted in advance by the following ways:
Light/power prediction: Based on the historical power generation data and weather forecast of the inverter, predict the output power for the next 1-2 hours, and start the fan in advance (if the predicted power will rise to 80% of the rated value, start the fan 5 minutes in advance) to avoid sudden temperature rise;
Dynamic PID regulation: PID (proportional integral derivative) algorithm is used to adjust the fan speed based on the temperature change rate (not just the temperature value), avoiding "frequent start stop" (prolonging the fan life), while quickly responding to temperature fluctuations.
3. Fault self diagnosis and heat dissipation protection
When the cooling system malfunctions (such as a stuck fan or blocked air duct), the protection mechanism should be triggered in a timely manner to avoid component damage:
Fan fault detection: The fan speed is detected by a Hall sensor. If the speed is lower than the set value (such as 50% of the rated speed), an alarm is triggered and the fan is switched to the backup fan (a high-power inverter can be designed with dual fan redundancy);
Air duct blockage detection: The air duct resistance is detected by the pressure difference sensor between the inlet and outlet. If the pressure difference exceeds the threshold (such as 100Pa), an alarm will prompt "Clean the dust net";
Overheating and derating/shutdown: If the temperature continues to exceed the safe threshold (such as IGBT temperature ≥ 90 ℃), gradually reduce the inverter output power (derating by 10% for every 5 ℃ increase) until the temperature drops; If the temperature rises to the limit value (such as 100 ℃), the shutdown protection will be triggered.
