The global energy system is undergoing a very profound change at this moment. Traditional power grids that rely on fossil fuels are now difficult to cope with the challenges of the climate crisis and energy security.
The core role of power electronics
Efficient conversion and control of electric energy is achieved with the help of precision semiconductor devices, such as IGBTs and silicon carbide modules. Power electronics technology provides key hardware support for the decarbonization of the energy system. Through it, the power generated by intermittent renewable energy sources such as wind energy and solar energy can be effectively integrated into the existing power grid.
In particular, power electronic converters can convert the alternating current generated by wind turbines with changing frequencies into stable electrical energy that is strictly synchronized with the frequency of the grid. In a photovoltaic system, an inverter converts the DC output of the photovoltaic panels into AC power that can be connected to the grid. Without these core equipment, large-scale renewable energy grid integration would not be possible.
New challenges of grid inertia
As traditional coal-fired and gas-fired generator sets are largely replaced by power electronic equipment, the power grid is facing the serious problem of declining inertia. The huge rotating mass of traditional synchronous generator sets itself can buffer power fluctuations and maintain frequency stability. Renewable energy sources connected to the grid through converters do not have this physical inertia.
If the grid inertia is reduced, it will directly lead to an acceleration of the system frequency change, thereby reducing the tolerance to faults and power fluctuations. This increases the risk of large-scale power outages and becomes a technical bottleneck that high-proportion renewable energy grids must solve. Especially after events such as the Texas blackout in the United States in 2021, this issue has received extra attention.
Solutions based on power electronics
To address the problem of missing inertia, researchers have proposed solutions based on power electronics, such as "virtual synchronous machine" and "virtual inertia". Virtual synchronous machine technology simulates the operating characteristics and external response of a synchronous generator by improving the control algorithm of the converter. For example, the rocking equation of the rotor can be simulated to provide frequency support capabilities to the converter.
Another solution is to configure an energy storage system with fast response characteristics, such as lithium-ion batteries or flywheel energy storage, and to use power electronic equipment to implement control. Once the grid frequency fluctuates, this energy storage system can release or absorb power within a millisecond-level time range and actively provide frequency adjustment services. In effect, it is equivalent to increasing the inertia of the grid.
The architectural evolution of new power grids
In the future, the power grid will transform into a "no-rotation" or "low-rotation" power electronic power grid. The key part of this power grid is a network composed of many distributed converters. The operation of this network relies on communication and collaborative control. For example, we can build a "cellular" power grid architecture like the one demonstrated in Germany, dividing the power grid into many microgrid cells that can operate in a self-consistent manner.
Inside each microgrid cell, power generation and load can achieve an instant balance, and with the help of a flexible connection between the power electronic interface and the main grid, the flexibility of the grid can be greatly improved. When the main grid fails, a single cell can operate independently from the main grid, thus ensuring that key loads can continue to enjoy power supply, and the reliability of power supply has been significantly improved.
Singapore’s cutting-edge research practices
Nanyang Technological University is located in Singapore. It is at the forefront of the world and plays a leading role in related scientific research fields. Within its School of Electrical and Electronic Engineering, there is a specific research institution called the "Institute of Power Electronics and Applications in Smart Grids", which focuses on how new energy can be integrated into the power grid and how to effectively control it. In the field of distributed energy cluster control and DC microgrid stability, the team has obtained progress results that are of practical significance and can be effectively implemented.
For example, that institute has specially developed plug-and-play photovoltaic grid-connected devices for use in tropical urban environments, and then carefully studied the reliability of power electronic equipment under conditions of high humidity and high salt spray. These related studies are closely related to the specific actual situation of Singapore due to its small land area and reliance on energy imports. The purpose is to improve the resilience and efficiency of the urban energy system.
Prospects for future research directions
To achieve a completely clean and flexible future power grid, we still need to continue to explore multiple technical paths. First, it is necessary to develop more intelligent "grid-forming" converters so that they can build the grid voltage and frequency by themselves like traditional generators, rather than relying on the support of the existing grid. This will be the basis for achieving a 100% converter grid.
First, research on the application of wide bandgap semiconductor devices in power grids has been strengthened. Materials such as silicon carbide can make converters more efficient, smaller in size, and faster in response. At the same time, it is necessary to build a stability analysis theory and standard system suitable for the new power grid, so as to provide reliable technical specifications and safety guarantees for the global energy transformation.
In your opinion, what is the biggest technical obstacle to ensuring the stable operation of the power grid in the transition to a high proportion of renewable energy? Welcome to share your opinions and insights in the comment area. If you find this article helpful, please like it to support it.
