4 The Transition of China’s Power System
105
(2) Power electronization of the power system
The new-generation power system will be characterized by the proliferation of power
electronics, the most important of which is the UHV transmission system that has
flourished in recent years. China, the global test bed for UHV transmission lines,
had built nine UHV AC and ten DC lines by June 2019 and is building another three
UHV AC and one DC lines. The total length of operating UHV lines in the country
amounted to 27,570 km, and the total transformation (conversion) capacity stood at
296.2 million kVA (kW). By the end of 2019, China’s UHV lines had delivered more
than 1.15 trillion kWh of electricity cumulatively, making tremendous contribution
to stable power supply, clean energy development, environmental improvement and
grid safety.
East and South China, the two major load centers where multiple DC transmission
terminal stations are located, are the focus of the country’s UHVDC construction
project. Technical challenges of system operation, such as the dynamic reactive power
support in handling the commutation failure to a receiving-end grid with multi-DC
lines feeding, and stable and coordinated control of sending and receiving-end in
AC-DC hybrid systems, require further research for solutions.
Furthermore, with intensified development of renewable energy in western China
and growing demand for west-east power transmission, clean power in China’s west
will be produced through the complementarity across regions and river basins of
diverse energy sources of hydro, wind and solar as well as from low-emissions
coal plants with tremendous flexibility, and transmitted over long distances to load
centers in east China, with renewables as the mainstay. The vision Zhou academician
proposed to build a DC transmission grid on top of the existing west-to-east singlephase HVDC to supply energy from the west to the load centers in the east may very
well become a reality (Zhou et al. 2013).
The demonstration project of four-terminal VSC-HVDC from Zhangbei to Beijing
(see Fig. 4.1), which began construction at the tail end of 2017, will provide China
with useful experiences for the construction of DC grids in the future.
On the other hand, with the development of renewable energy, a host of power
electronic converters such as direct drive wind turbine converters, PV power plant and
distributed PV inverters, non-hydro energy storage stations and distributed energy
storage inverters, are now connected to the grid. In additional to centralized large
wind and solar installations, more small-capacity, distributed wind and solar power
systems are being implemented. At present, wind and solar power curtailment has
hobbled the development of centralized wind and solar power in western China
while distributed wind and solar generation has witnessed substantial growth in the
central and eastern regions. Meanwhile, the ongoing poverty alleviation project by
installation of solar PV panels in poor households has also dramatically increased
the amount of power electronic equipment connected to the grid.
As a rising number of power electronic equipment of various types and voltage
levels are connected to the grid, the increasing power electronization of China’s power
system will lead to a range of challenges in such areas as operation safety, system
analysis and control, and simulation modeling and calculations. They include:
105
(2) Power electronization of the power system
The new-generation power system will be characterized by the proliferation of power
electronics, the most important of which is the UHV transmission system that has
flourished in recent years. China, the global test bed for UHV transmission lines,
had built nine UHV AC and ten DC lines by June 2019 and is building another three
UHV AC and one DC lines. The total length of operating UHV lines in the country
amounted to 27,570 km, and the total transformation (conversion) capacity stood at
296.2 million kVA (kW). By the end of 2019, China’s UHV lines had delivered more
than 1.15 trillion kWh of electricity cumulatively, making tremendous contribution
to stable power supply, clean energy development, environmental improvement and
grid safety.
East and South China, the two major load centers where multiple DC transmission
terminal stations are located, are the focus of the country’s UHVDC construction
project. Technical challenges of system operation, such as the dynamic reactive power
support in handling the commutation failure to a receiving-end grid with multi-DC
lines feeding, and stable and coordinated control of sending and receiving-end in
AC-DC hybrid systems, require further research for solutions.
Furthermore, with intensified development of renewable energy in western China
and growing demand for west-east power transmission, clean power in China’s west
will be produced through the complementarity across regions and river basins of
diverse energy sources of hydro, wind and solar as well as from low-emissions
coal plants with tremendous flexibility, and transmitted over long distances to load
centers in east China, with renewables as the mainstay. The vision Zhou academician
proposed to build a DC transmission grid on top of the existing west-to-east singlephase HVDC to supply energy from the west to the load centers in the east may very
well become a reality (Zhou et al. 2013).
The demonstration project of four-terminal VSC-HVDC from Zhangbei to Beijing
(see Fig. 4.1), which began construction at the tail end of 2017, will provide China
with useful experiences for the construction of DC grids in the future.
On the other hand, with the development of renewable energy, a host of power
electronic converters such as direct drive wind turbine converters, PV power plant and
distributed PV inverters, non-hydro energy storage stations and distributed energy
storage inverters, are now connected to the grid. In additional to centralized large
wind and solar installations, more small-capacity, distributed wind and solar power
systems are being implemented. At present, wind and solar power curtailment has
hobbled the development of centralized wind and solar power in western China
while distributed wind and solar generation has witnessed substantial growth in the
central and eastern regions. Meanwhile, the ongoing poverty alleviation project by
installation of solar PV panels in poor households has also dramatically increased
the amount of power electronic equipment connected to the grid.
As a rising number of power electronic equipment of various types and voltage
levels are connected to the grid, the increasing power electronization of China’s power
system will lead to a range of challenges in such areas as operation safety, system
analysis and control, and simulation modeling and calculations. They include: