Renewable energy capacity surges, threatening grid safety! Can grid-forming technology offer a solution?

Balancing the two major goals of energy transition and grid safety under China's rapidly growing renewable energy capacity is a major challenge.

 

In the process of building a new power system based primarily on renewable energy, the "dual-high" characteristics will become more prominent. Especially in the Northwest region with its weak grid, the existing weak support characteristics of renewable energy will exacerbate problems such as weak inertia and weak damping in the system. However, China's resource endowment and energy demand mean that the scale of west-to-east and north-to-south power transmission still needs to be further expanded. When renewable energy development and grid safety are difficult to reconcile, grid-forming technology has become the key to breaking the deadlock in the industry.

 

 

 

Renewable energy development and

Technological iteration behind grid safety

 

 

Although domestic renewable energy development is currently facing a "painful period" of policy adjustments, renewable energy remains the main force in the construction of a new power system. Many industry experts believe that Document No. 136 marks the beginning of renewable energy's transition to a dominant energy source.

 

Taking the Northwest region as an example, relevant personnel from the Electric Power Planning and Design Institute pointed out that during the 14th Five-Year Plan period, more than 100 GW of new renewable energy capacity will still be added for "west-to-east power transmission"; in April this year, the National Forestry and Grassland Administration approved the "Planning for Photovoltaic Desertification Control in the Three-North Desert, Gobi, and Arid Regions (2024-2030)", allocating 200,000 square kilometers of usable land for photovoltaic desertification control, with a theoretical installed capacity of nearly 1000 GW.

 

 

It is foreseeable that the Northwest region will remain the main force in China's renewable energy growth for some time to come. However, if the current weak support problem of renewable energy to the power grid is not solved, the contradiction between the continuously declining utilization rate of renewable energy and grid safety will become increasingly prominent.

 

For the power grid, the "stability" of voltage and frequency is the prerequisite for its safe operation, and the "balance" between power generation and power consumption is its fundamental task. Traditional thermal power and hydropower units, due to their mechanical inertia during operation, make the frequency of the power system they dominate less susceptible to disturbances in the network. However, with the increasing proportion of renewable energy installations, its intermittent and fluctuating nature challenges the stability of the grid's voltage and frequency.

 

In grid cognition, in addition to weak support characteristics, wideband negative damping characteristics and low anti-interference ability are also typical shortcomings of current grid-connected renewable energy generation. To ensure stable grid operation, "limiting generation" of renewable energy has become the preferred method under specific conditions.

 

The rapid increase in renewable energy capacity urgently requires the industry to find answers at the technical level to solve this problem. The emergence of grid-forming technology provides a powerful solution.

 

Generally speaking, the stable operation of grid-connected equipment relies on the stable frequency and voltage provided by the power grid, requiring high voltage quality and a relatively slow response to disturbances in the grid due to lag. In extreme cases, grid-connected equipment will disconnect to protect itself; while grid-forming equipment connects to the grid in a manner that simulates the operation of a synchronous machine, providing voltage and frequency support to the grid when faults or disturbances occur, thereby improving the strength of the local grid.

 

 

Furthermore, a stable grid can accommodate more renewable energy, greatly improving the utilization rate of renewable energy and reducing the problem of limiting generation due to safety considerations.

 

In addition, applications such as large-scale renewable energy bases, offshore photovoltaic power plants, and offshore wind farms are located in weak grid environments, making it more difficult to safely and stably transmit renewable energy. Coupled with the increasing demand for off-grid, integrated energy parks, and distributed renewable energy generation scenarios, renewable energy is gradually transitioning from supporting the grid to a new stage of independent grid formation.

 

In fact, the competent authorities have recognized this problem. Recently, the National Energy Administration, in its "Notice on Organizing and Carrying Out the First Batch of Pilot Projects for the Construction of New Power Systems," clearly pointed out that grid-forming technology is the first pilot direction. Relevant personnel from the State Grid Hebei Company also stated that preliminary research shows that the future power grid may need to be equipped with about 30% grid-forming technology.

 

 

 

Grid-forming technology: The "difficulty" lies in implementation

 

 

Grid-forming technology originates from virtual synchronous machines, first used in UPS power supplies, and has been applied internationally. In 1977, the German Solar Energy Supply Technology Institute first proposed the concept of "grid-forming control," laying the theoretical foundation; in 2016, after a large-scale power outage in Australia, renewable energy companies used grid-forming technology to support the power grid, promoting the practical application of this technology; in 2022, China began to accelerate the research and development and application of grid-forming technology. In early 2023, Chinese renewable energy equipment company Huawing Electric received the world's first grid-forming inverter certificate from the internationally renowned institution DNV.

 

It can be seen that with the increase in renewable energy installations, the importance of grid-forming technology in supporting and ensuring grid safety is becoming increasingly prominent. After realizing this, at this year's SNEC exhibition, some inverter companies launched grid-forming related products, among which Huawing Electric showcased a grid-forming solution based on wind-solar-storage synergy.

 

 

"The core of grid-forming technology is the software application within the electrical equipment, which has a certain technical threshold but is not impossible to replicate," a Huawing Electric staff member told reporters. "However, the product verification after the technical level, the review by the competent authorities, and the process of product implementation are extremely lengthy."

 

"The complexity of power sources, loads, and supply and demand conditions varies from province to province, resulting in differences in the processes faced by power grid companies when applying new technologies. Before practical application, grid-forming related products must undergo rigorous verification by local electric power research institutes," the staff member added, "How to establish a closed loop from research and development to product application is the real test."

 

From launching preliminary research work in 2019 to completing the transition from technological research and development to industrial application in 2023, Huawing Electric, with its deep technological accumulation and forward-looking industry insights, has taken the lead in completing the strategic layout of the renewable energy ecosystem, successfully building a station ecosystem that integrates the implementation and evaluation of "wind-solar-storage" full-scenario grid-forming technology, and has achieved large-scale application of grid-forming projects.

 

 

 

Huawing Electric:

Leading the grid-forming era

 

 

According to the introduction, Huawing Electric's independently developed grid-forming wind power converters cover 1.5MW~20MW doubly-fed machine types and 1MW~30MW full-power machine types; the grid-forming 320kW photovoltaic inverter independently establishes voltage and synchronizes the grid frequency, can maintain stable port voltage and frequency for a long time, and has island operation and black start capabilities; the grid-forming energy storage converter uses VSG technology, meets the 3 times 10s overload requirement, and has inertia response, damping characteristics, primary frequency regulation, and whole-station black start capabilities.

 

 

For example, in the world's first main power-type wind farm, China Green Development, together with Hevo Electric and Shanghai Jiao Tong University, jointly implemented the project, overcoming key technologies such as self-synchronous voltage source wind turbine units and station collaborative control. The project uses 3.2MW grid-forming wind power converters provided by Hevo Electric. It has passed more than 530 comprehensive tests, including steady-state, transient, grid-connected, off-grid, and black start tests, as well as station-level tests such as full-field black start, isolated grid load carrying, and in-field artificial short circuits, successfully achieving the operation of a 100MW-level entire field.

 

The first domestic main power-type photovoltaic power station also uses Hevo's 320kW grid-forming string inverters. Through the virtual synchronous generator (VSG) control strategy, it can achieve core functions such as actively supporting the grid, suppressing wide-frequency oscillations, island operation, and black start. At the same time, the on-site test uses Hevo's multi-functional grid simulation device to complete a full-dimensional test verification covering 10 major items, 21 sub-items, and 209 test conditions, including grid-forming photovoltaic inertia response, primary frequency regulation, impedance scanning, and short-circuit ratio adaptability.

 

The first large-scale lithium-sodium hybrid energy storage station in China, which was recently connected to the grid, also uses string energy storage converters with grid-forming technology provided by Hevo Electric. It has not only completed grid-forming grid-connected/off-grid full-condition tests but also pioneered station-level multi-unit collaborative black start. The "40MWh high and low-rate composite operation grid-forming sodium-ion battery energy storage system" applied in this project has made major breakthroughs in three aspects: large-capacity power-type sodium-ion batteries, high-efficiency and strong overload grid-forming energy storage converters, and high and low-rate composite operation system integration. According to authoritative appraisal, the product performance indicators have reached the international leading level.

 

 

By the end of April this year, China's installed capacity of new energy sources has exceeded 1500GW. According to relevant data from the National Energy Administration, China's new energy installed capacity will maintain a growth rate of 200GW/year+. The local grids composed of water, wind, solar, thermal, and nuclear power sources will become increasingly complex. On the road to a new power system dominated by new energy sources, grid-forming technology is expected to become a "moat" for grid security.