Table 1 Boundary condition of renewable energy accommodation capacity in “Three North” region of China in 2020

1. System reserve capacity

Max {5% of the maximum load, the maximum capacity of a single unit (or one polar of DC system)}. Participation in power balance of wind and PV power in accordance with the forecast value minus the installed capacity of 20%.

2. Units starting mode

Units start and stop with the minimum cycle once a week.

3. The maximum and minimum technical output selection of thermal power units

Arrangement according to actual operation of units, while that cannot get the actual situation according to following arrangements:

(1) The maximum technical output under the gas condenser condition:According to unit rated capacity.

(2) The minimum technical output under the gas condenser condition:Calculation as 60% of the rated capacity of over 200 MW, and heating units are considered in the early stage, middle stage and final stage of heating period.

4. Load data

Load curve of one year is based on historical load curve, considering a certain rate of load forecast growth, as the based data of renewable energy accommodation ability assessment.

5. Constraint conditions with hydro-power participation in balance

The maximum and minimum technical output of hydro-power is determined according to the actual operation requirements, and the utilization hours per year in accordance with the average level of nearly 3 years.

6. Annual renewable energy utilization hours with no obstruction

Estimates in accordance with average resources over the past 3 years are calculated, simultaneously taking into account floating 10% for sensitivity analysis.

7. Normalized sequence of renewable energy

Renewable energy output is returned to original condition or shape on the basis of obstruction, and then formed a normalized sequence.

8. Treatment principle of tie-lines

Tie-lines are treated according to their historical operation reality.