PowerTech Green Line 1000 is proving its worth in China’s largest test wind farm
The Chinese wind power market has expanded rapidly in recent years, and extensive work is being done to develop grid feed-in regulations for wind turbines and their feasibility in the field. As renewable energy production continues to grow, the technological requirements for renewable energies are also rising. Renewable energies also have to face the same tasks as classic power plant units: demand-based energy generation, security of supply and grid support. The Chinese authorities have already taken inadequate wind farms out of service as a result. PowerTech reactive power converters offer a cost-effective, easy-to-integrate retrofit solution even for this market.
While coal dominated power generation in China for decades, the Chinese government is now increasingly focusing on wind energy as a clean and economical alternative. For the first time in 2010, China became the country with the highest installation rate of new wind turbines – in total, over 14,000 MW of capacity was installed. The country is currently the international leader with over (40,000 MW) 211 GW (as of 2018) of wind turbines installed.
Test centre in Zhangbei

One way to solve the current challenges in the Chinese wind power industry is the wind turbine test centre opened in January 2010. The National Wind Power Integration Research and Test Center (NWIC), located in Zhangbei province, offers a specialised environment for research and development, test sequences, training courses and professional education. The largest test park in the country is organised and controlled by the China Electric Power Research Institute (CEPRI), a subsidiary of the State Grid Corporation of China (SGCC). The institute was founded in 1951 and is headquartered in northern Beijing. Its main task is research and development on all aspects of energy supply in China.
The Zhangbei test park is designed for extensive prototype testing of wind turbines as well as for the typical grid connection tests (grid codes). All the necessary requirements are set up at the central feed-in point. This includes a low-voltage ride through (LVRT) system, grid simulators with a capacity of 6 MW and an energy storage system with an output of 2.5 MW.
Research into grid compatibility
In cooperation with one of the top 10 wind turbine manufacturers, extensive tests are being conducted at the Zhangbei test park to establish whether the turbines can feed reactive power into the grid as specified by the grid codes. Further tests are also underway to check the frequency control requirements to support grid stability as well as grid-stabilising properties of the wind turbines if certain faults arise in the power system.
As a long-standing supplier and technology partner, PowerTech Converter is contributing its Green Line 1000 – a reactive power converter that meets the demand of grid operators for providing a reactive current during a temporary voltage drop at the wind turbine. More than 130 MW of wind power capacity has already been fitted with PowerTech’s Green Line 1000.
LVRT requirements fully satisfied
The Green Line 1000 is connected on the 690 V side parallel to the wind generator of the respective system. It consists of a pulsed IGBT converter with an intermediate voltage circuit. When nominal conditions exist on the grid side, the inverter operates in stand-by mode. In the event of a line-side voltage drop, it switches into active mode and supplies an adjustable reactive current of up to 2500 A.
Following the grid feed-in regulations tested in Zhangbei, the Green Line 1000 starts feeding reactive current into the grid when the grid voltage drops below 90 percent of the nominal voltage. The reactive current volume increases in linear proportion to the extent of the line voltage dip, and up to an adjustable value. This means that all common LVRT requirements are fully met: Balanced grid dips are controlled up to 15 percent of the line voltage – unbalanced dips even up to 0 percent of the line voltage. It is able to ride through several consecutive line voltage dips. The DCU control unit developed by PowerTech independently and intelligently detects and handles each of these incidents.
Well over 100 grid voltage dips were carried out at the Zhangbei test park. The Green Line 1000 worked perfectly in ever case. Given the harsh climatic conditions in Zhangbei, the fact that no thermal or electrical problems occurred is a great triumph for PowerTech and proof for the wind turbine manufacturer that their own turbines are already able to comply with the defined grid quality standards in line with international grid feed-in regulations.