Application of IGBT Drive Power Supplies in Photovoltaic Inverters
CONTENT:
Inverters are one of the most important pieces of equipment in a solar energy system. These devices are used to convert the DC electricity generated by a solar panel into AC electricity, which the electrical grid uses. A PV inverter's tasks vary and include conversion efficiency, power optimization, energy monitoring, and temperature management.
IGBT drivers can be used in a wide range of applications. As part of this introductive series, we will review more information about their applications in photovoltaic inverters and some of the challenges most often associated with this technology.
The Challenges of Using IGBT Technology in Power Modules
IGBT drivers are at the heart of IGBTs, as they generate gate signals used to turn on and off the IGBT according to the command signals from the control circuit. IGBT gate drivers also usually provide the electrical isolation which is often needed between the control circuit and the power stage.
IGBTs are usually recognized for their high-voltage and high-current characteristics. For this reason, they are often used as switching devices in AC/DC inverters circuits for motor drive systems, uninterruptible power supplies, and other applications. IGBTs are also often found in solar inverters, where they perform the key function of converting DC from solar cells to the AC required by various electrical equipment.
Regardless of their specific applications, IGBTs generally contribute to high efficiency and space-saving in the circuits. In addition, IGBT drive power supplies provide reliable electrical isolation so that the control system can not be affected by the interference often caused by IGBT.
However, despite the several advantages, there are still some challenges to consider concerning the application of IGBT technology in power modules. One of the most prominent challenges is that power semiconductors are becoming increasingly thinner, smaller, and faster. Employing faster IGBTs complicates their design in power modules. Designers also have to strike the right balance between switching speed, switching loss, and the overall electromagnetic compatibility for the power-converting system. Therefore, designers should consider the specific performance characteristics required by drive power supplies providing gate drive power for IGBTs.
Besides the more general advantages and disadvantages of IGBT gate drivers, the challenges and benefits associated with their employment can also slightly vary according to their actual application. Among the many applications, IGBT drivers are becoming even more important when used in solar power equipment. Below we will review some of the main benefits and challenges associated with using IGBT drivers in PV applications.
The Challenges of Employing IGBT Drive Power Supplies for Photovoltaic Applications
A growing trend in the PV industry is to make PV power plants more cost-effective by employing a higher maximum DC voltage. However, as solar inverters move from 1000V to 1500V, they can also potentially become more unstable because of this voltage jump. It is also worth mentioning that the inverter is still often considered the weakest link in modern photovoltaic systems.
By considering all of these aspects, engineers can rely on the help of solar inverter IGBTs to limit the risk of inverter failure. However, there also have two main challenges to IGBT drive power supplies, which are high isolation and CMTI:
1. High isolation
The bus voltage of the photovoltaic system is very high, and the voltage range is 1000V-1500V. Both ends of the IGBT drive power supply in the photovoltaic inverter will bear this high voltage, so the IGBT drive power supply must be the reinforced insulation, and the isolation voltage should be high.
On the other hand, the high voltage at both ends of the driving power supply exists for a long time. Therefore, to ensure the reliability of the driving power supply, it is best to pass the partial discharge test verification, and the partial discharge voltage should meet the requirements of more than 1500V.
2. CMTI
The IGBT is a high-frequency PWM operation, and the system will have a high-frequency common-mode transient voltage. Therefore, special attention needs to be paid to the indicator CMTI, the abbreviation of Common mode transient immunity. For IGBT, CMTI usually needs to meet 30Kv/us. If the CMTI of the driving power supply does not reach 30Kv/us, the common-mode transient voltage may interfere with the IGBT driving signal. As a result, the drive signal will be wrong, lost, and delayed, so the IGBT cannot work normally. More serious, it may break down the driving power supply, resulting in insulation failure and system safety risks.
MORNSUN's Power Supply Solutions
As mentioned above, PV systems currently often operate at a voltage of 1500V. This change in operation voltage for PV systems requires the employment of power supplies designed precisely for this application and this new standard.
In fact, MORNSUN has designed a series of power supplies with a simplified and more efficient design to lower the operating costs associated with PV systems. Consider, for example, the MORNSUN QAxx3-xxxxR3, a series of DC/DC converters designed specifically for 1700V or lower IGBT gate drivers.
This series of DC/DC converters for IGBT drivers have all reinforced insulation. The isolation voltage reaches 5kVAC, and the partial discharge voltage reaches 1700V, which meets the high isolation requirements of photovoltaic inverter IGBT applications. In addition, the CMTI is as high as 200Kv/us, which also meets the requirements of photovoltaic inverter IGBT applications. On the other hand, the mode of common ground outputs is adopted internally for better energy provision of IGBT turn-on and turn-off. In addition, output short-circuits protection and self-recovery capabilities are also provided.
We also provide QAxx3C-R3 Serious, a DC-DC module power supply designed for SiC MOSFET driver requiring two sets of isolation power supplies.
The MORNSUN DC/DC converters for IGBT drivers can help designers realize the reliable, safe electrical isolation between the power semiconductor and the control circuit. They will be key to getting evaluation platforms designed quickly by freeing designers up to focus on the other aspects of their design.
Contact us to request more information about our solutions for IGBT drive DC/DC converters for solar inverter applications or other systems. We will be glad to support you in your selection and reply to all of your questions.
