Introduction
During recent national policymaking meetings, Ruan Qiantu, chairman and party secretary of State Grid Fujian Electric Power, noted that new-type power systems are a key platform for building a modern energy system and supporting carbon peak and carbon neutrality goals. Achieving a basically completed new power system by 2035 requires addressing several emerging challenges.
Challenges Facing New Power Systems
First, renewable energy curtailment pressure is rising. One issue is a lack of coordinated planning for project development. Renewable projects have much shorter construction cycles than many power generation and grid projects. Without synchronized planning, commissioning, and market-based consumption mechanisms, wind and solar generation are prone to curtailment. A second issue is limited local grid hosting capacity. Distributed photovoltaics have grown explosively, and some regions have no remaining connection capacity. For example, in Fujian Province, distributed PV capacity is expected to exceed 15 GW by 2025, far above the previously planned limit of 8 GW; in a 2023 assessment of distributed PV grid connection capacity, 4 of 10 pilot counties reported zero available new connection capacity.
Second, ensuring power supply reliability is becoming more difficult. At peak times, effective renewable generation capacity can be insufficient. Renewables now account for most new installed generation capacity, but their seasonal distribution is uneven and their peak capability is limited. For example, on the highest-load day in Fujian in 2022, installed wind capacity exceeded 7 GW, but wind output during peak load was only 2.7% of installed capacity. Extreme weather events such as heavy rain, floods, typhoons, and ice storms have increased in frequency and intensity, reducing renewable output and posing risks to grid infrastructure and equipment.
Third, the effective cost of using renewable energy is rising. Grid-parity generation does not guarantee parity in utilization. Balancing renewable output variability and ensuring consumption require additional costs for source regulation and grid reinforcement. Estimates indicate that by 2025, additional grid reinforcement and related costs could reach 0.20 CNY/kWh, bringing the terminal utilization cost of renewables to about 0.54 CNY/kWh, roughly 0.14 CNY/kWh higher than the benchmark coal price.
The Role of Silicon Carbide
Power electronics represented by silicon carbide (SiC) show significant potential. As a third-generation semiconductor material, SiC has advantages under decarbonization goals. Industry estimates project that electric energy could surpass coal as the largest final energy form before 2025, with end-use electrification rates reaching 50% by 2050, making electricity increasingly central. In this context, China has set targets for carbon peak by 2030 and carbon neutrality by 2060.
Projections suggest that in 2024, newly commissioned generation capacity will exceed 300 million kW (300 GW), and cumulative renewable generation capacity will for the first time surpass coal-fired capacity. Driven by rapid renewable growth, total installed generation capacity may reach 3.25 billion kW (3,250 GW) by the end of 2024, a year-on-year increase of 12%. Grid-connected wind and solar could reach 530 million kW (530 GW) and 780 million kW (780 GW) respectively, with combined wind and solar capacity exceeding coal capacity and accounting for about 40% of total installed capacity.
Such rapid growth of renewables creates several technical challenges for power systems. First, solar and wind are variable, intermittent, and uncertain, producing characteristic "duck curve" load profiles. For example, in California, solar output drops after sunset while residential demand rises, creating large ramping and peak-valley differences that complicate supply-demand balance. Second, high renewable penetration places severe demands on grid ramping, frequency regulation, and voltage control. Third, generation-side and load-side roles swap frequently as renewable output fluctuates, complicating operation, power flow distribution, and emergency response. Fourth, electric vehicle charging and vehicle-to-grid behavior introduce strong spatiotemporal uncertainty. Fifth, distribution networks are transitioning from passive, unidirectional systems to active networks due to distributed PV and storage. Sixth, high penetration of power-electronic equipment reduces system inertia and damping and can introduce wide-band oscillations. Seventh, some loads exhibit inverse frequency characteristics. In new power systems, renewable integration, AC-DC power transfer and flexible interconnection, bidirectional power flow in distribution and consumption-side converters, and devices needed for grid stability such as energy storage, harmonic mitigation, and reactive power compensation all rely on power electronic converters.
The widespread integration of power electronic devices will substantially change the electrical characteristics of power systems. Harmonics and reactive power generated by power electronic devices can negatively affect power quality, power factor, and grid stability. In this context, the advantages of SiC become prominent. As noted by industry experts, power semiconductors are a "necessary" element for new power systems rather than a "special need." Applications with large SiC potential include wind farm converters, PV inverters, energy storage PCS, and EV charge/discharge systems (V2G). Introducing SiC power devices supports the development of a more flexible and power-electronic-driven grid.
Key Application Scenarios
Solid-State Transformers
With the continuous development of distributed generation and smart grid technologies, solid-state transformers (SSTs) are becoming a key energy conversion unit, combining power electronic converters and high-voltage transformers. Compared with traditional transformers, SSTs can offer smaller size, higher power quality, higher conversion efficiency, and more stable operating performance, which helps address limitations of conventional transformers in modern grids.
Power switch device blocking voltage depends closely on drift region and base region length and resistivity. SiC-based power devices can operate at much higher temperatures and support much higher breakdown fields. Using SiC for high-voltage power switches allows for lower required resistivity and shorter drift or base regions, enabling significant increases in operating frequency.
Flexible AC/DC Transmission
Flexible AC transmission systems are among the advanced technologies for alternating-current grids. SiC power electronic devices can achieve precise and efficient control of system voltage, power flow, and transmission quality while reducing transmission losses.
Flexible DC transmission, based on voltage-source converters (VSC-HVDC), comprises converter stations and DC transmission lines. It is considered a highly flexible and adaptive next-generation transmission technology and is an important tool for supporting energy transition and the construction of new power systems.
Future grids will need to integrate large amounts of distributed clean generation and storage, demanding stronger and more flexible regulation, control, and transmission route options. Existing high-voltage AC connection technologies cannot fully meet these needs, so extensive adoption of flexible AC/DC transmission in transmission and distribution networks is required. This provides a substantial application area for SiC materials and devices.
Currently, high-voltage transmission modes include AC, conventional DC, and flexible DC. Conventional DC offers benefits over AC, such as lower conductor costs and improved delivery efficiency, but has drawbacks including lower control flexibility and the need for significant filtering, making it less suitable for wind farms and urban distribution networks. Flexible DC transmission can reduce land use compared with conventional DC, with estimates suggesting up to 20% land savings in converter/filter areas.
Market analysts predict that the high-voltage DC transmission market will grow significantly, driven mainly by demand for flexible DC technology. Projections suggest market expansion from US$8.2 billion in 2018 to US$12.3 billion in 2024, with a compound annual growth rate of about 6.9%. The converter station market is also expected to grow, with estimates of about US$3.94 billion by 2025 and a CAGR close to 11% for 2020-2025.
Static Synchronous Compensators (STATCOM)
New power systems dominated by renewables exhibit high uncertainty, low inertia, weak disturbance rejection, and strong nonlinearity. Their fast dynamic response characteristics and large scale create new challenges for voltage stability and require improved reactive power compensation systems.
As energy demand grows, the power transmission sector must expand and improve efficiency to match socioeconomic development. Increasing generation must be accompanied by reduced transmission losses and lower operating costs, which drives the need for high-performance, flexible, and resilient power-electronic reactive power compensation systems.
In power systems, STATCOMs are used for power flow control, reactive power compensation, and enhancing system stability. Based on two-level voltage-source converters (VSC), STATCOMs offer compact size, fast response, and continuously adjustable output. However, they require high-voltage, high-power power electronic devices, and current silicon devices are often inadequate for large-capacity transmission systems.
Figure: A novel D-STATCOM voltage control method and process (source: intellectual property bureau)
Currently, STATCOMs typically use fully controlled devices such as GTO, IGBT, and IGCT. For example, IGCTs can reach 6.5 kV and conduct currents up to 4000 A, but voltage and current ratings in transmission systems are still limited, requiring multilevel topologies or series device stacking to achieve higher withstand voltages. Successful development of high-voltage SiC IGBTs, GTOs, and similar devices could greatly simplify STATCOM architectures and, thanks to higher switching frequencies, improve power quality. Transformerless STATCOM structures are likely to see wider adoption in applications involving wind and solar generation.
Given the "double-high" characteristics of new power systems and the stochastic, fluctuating, and dispersed nature of renewable generation, power-side variability and load-side uncertainty both increase. This raises pressure on system power balance and exacerbates voltage control issues, making research into high-performance power-electronic reactive compensation systems for voltage regulation important.
Device Classes and Deployment Outlook
SiC devices used in new power systems fall into two main categories. One category is medium- and low-voltage SiC MOSFETs covering roughly 1200 V to 6500 V. These devices are mainly used in distribution networks, such as PV inverters for distributed generation and energy storage PCS. Demand for these devices will expand as distribution networks become active and AC/DC connections require flexible power electronic converters. Domestic 3300 V SiC devices are expected to enter mass applications in the distribution network. In transmission systems, large-capacity conversion equipment will create space for SiC devices rated at tens of kilovolts and kiloamperes to replace silicon devices.
Under decarbonization goals, building new power systems still faces many challenges. Power electronic technology is a key means of addressing these challenges, and the grid will trend toward flexible, power-electronic-based architectures. Various power electronic devices will play critical supporting roles across all layers of renewables-dominated power systems, and SiC devices will be widely promoted and deployed to help the grid become more flexible and power-electronic centric.
However, SiC devices for grid applications must still overcome issues such as harmonics and reactive power generated during operation, which can adversely affect power quality, power factor, and grid stability. Cost competitiveness must also improve. Progress is needed across the SiC industry chain, including large-diameter, high-quality substrates and epitaxial materials, chip current density improvements, high-voltage insulation packaging technologies, and application-level development. Currently, SiC device deployment remains at an experimental and exploratory stage, and application iteration and industry dialogue are required to accelerate the productization of SiC power electronic devices.
