4 The Transition of China’s Power System
155
load and new energy output) operation scenario with a high percentage of renewable
energy in the grid, and the shaded part means the uncertainty range. In this case,
if the traditional operation mode is still being used, load shedding will occur in
multiple timeslots, as shown in the red dotted line in the figure, which not only
reduces the economic efficiency of power system operation, but also impedes healthy
development of renewable energy.
When a high uptake of renewable energy is fed to the grid, three obvious changes
emerged: (1) Steep ramping in the system was found at certain timeslots, widening
the peak-valley gap, which means a substantial increase in flexibility demand; (2)
Renewable energy replaces most of traditional units output, thus reducing the regulation capacity of conventional power supply (flexible supply); (3) The failure of the
traditional power balance mode means the output range of traditional power supply
can’t completely cover the net load area, resulting in inflexibility at certain timeslots,
and a subsequent load shedding or loss of renewable energy. The current operation
rules of power system put safety at the center, thus leaving no choice but load shedding. Under this circumstance, in the future when a high proportion of renewable
energy power is fed to the grid, the coordinated development of generation, grid and
load based on flexible balance will be inevitable.
Power flexibility measures mainly include five aspects: power flexibility transformation, energy storage, demand response, power grid expansion planning and
flexibility market mechanism. The first four seek to improve flexibility from the
technical perspective; the last one aims to incentivise flexibility from a market point
of view. IRENA conducted a study on the cost of flexible resources for a multi-energy
system, and the results are shown in Fig. 4.25.
Now, varied measures in generation, grid, load and storage of China’s power
system have been actively deployed, with fruitful results. Some parts of northern
China have conducted flexibility modification of thermal power units, demonstration of large-scale energy storage in power grid, and ultra-high voltage direct currents
project, among others. Jiangsu province has piloted demand response and coordination of generation, grid and load, alleviating wind and solar curtailment to some
extent. But it should be noted that renewable power at the present still accounts for a
small percentage in the grid. Should it continues growing to extremely high proportion (e.g. 80% or even 100% at certain timeslots), the power system will be troubled
by close to zero or even negative net load. Due to the volatility of renewable energy
output, the resource potential to solve flexibility problems within the power system
will reach its limits. Therefore, in order to further reduce wind and solar curtailment through flexible resource planning in a more economic, efficient and holistic
manner, and accommodate the future high uptake of renewable power in the grid,
other forms of energy system should be introduced. The integration of other forms
of energy and electricity should be utilized to study the way multi-energy integration
improves system flexibility based on their physical mechanism. By doing so, the
flexible balance of supply and demand of the power system could be addressed in
the broader context of energy system, which would enable the move towards the
electricity-predominant new generation of energy system—the energy internet.
155
load and new energy output) operation scenario with a high percentage of renewable
energy in the grid, and the shaded part means the uncertainty range. In this case,
if the traditional operation mode is still being used, load shedding will occur in
multiple timeslots, as shown in the red dotted line in the figure, which not only
reduces the economic efficiency of power system operation, but also impedes healthy
development of renewable energy.
When a high uptake of renewable energy is fed to the grid, three obvious changes
emerged: (1) Steep ramping in the system was found at certain timeslots, widening
the peak-valley gap, which means a substantial increase in flexibility demand; (2)
Renewable energy replaces most of traditional units output, thus reducing the regulation capacity of conventional power supply (flexible supply); (3) The failure of the
traditional power balance mode means the output range of traditional power supply
can’t completely cover the net load area, resulting in inflexibility at certain timeslots,
and a subsequent load shedding or loss of renewable energy. The current operation
rules of power system put safety at the center, thus leaving no choice but load shedding. Under this circumstance, in the future when a high proportion of renewable
energy power is fed to the grid, the coordinated development of generation, grid and
load based on flexible balance will be inevitable.
Power flexibility measures mainly include five aspects: power flexibility transformation, energy storage, demand response, power grid expansion planning and
flexibility market mechanism. The first four seek to improve flexibility from the
technical perspective; the last one aims to incentivise flexibility from a market point
of view. IRENA conducted a study on the cost of flexible resources for a multi-energy
system, and the results are shown in Fig. 4.25.
Now, varied measures in generation, grid, load and storage of China’s power
system have been actively deployed, with fruitful results. Some parts of northern
China have conducted flexibility modification of thermal power units, demonstration of large-scale energy storage in power grid, and ultra-high voltage direct currents
project, among others. Jiangsu province has piloted demand response and coordination of generation, grid and load, alleviating wind and solar curtailment to some
extent. But it should be noted that renewable power at the present still accounts for a
small percentage in the grid. Should it continues growing to extremely high proportion (e.g. 80% or even 100% at certain timeslots), the power system will be troubled
by close to zero or even negative net load. Due to the volatility of renewable energy
output, the resource potential to solve flexibility problems within the power system
will reach its limits. Therefore, in order to further reduce wind and solar curtailment through flexible resource planning in a more economic, efficient and holistic
manner, and accommodate the future high uptake of renewable power in the grid,
other forms of energy system should be introduced. The integration of other forms
of energy and electricity should be utilized to study the way multi-energy integration
improves system flexibility based on their physical mechanism. By doing so, the
flexible balance of supply and demand of the power system could be addressed in
the broader context of energy system, which would enable the move towards the
electricity-predominant new generation of energy system—the energy internet.