IEEE Power & Energy Magazine - November/December 2015 - 44

Sound policy measures and industry management mechanisms
are key factors that determine the actual effectiveness
of renewable energy integration.

from the high minimum output of coal-fired generators can
be reduced from 8.1% to less than 2% (see Figure 3). The
overall wind curtailment rate in the northeast China power
grid could then be reduced to 7.4% from 13.7%, under the
existing conditions of the system.
Analysis results also showed that, for a specific power
system, as the minimum output of coal-fired generation
decreases, the effect of its benefit on reducing wind curtailment will also decrease. Take the northeast China power grid
in 2013 as an example again. When the minimum output of
coal-fired generators is decreased by fewer than four percentage points on the current basis, the reduced wind curtailment
on average would be 0.93 percentage points per percent of
the minimum output decrease. When the minimum output of
coal-fired generators is decreased by more than four percentage points, the reduced wind curtailment on average is only
0.65 percentage points. Besides, from a cost benefit point of
view, with the benefit reduction of decreasing the minimum
output of coal-fired generators, the operation cost on wear
and tear of coal-fired units will increase and the heat rate
decrease. Further analysis is obviously needed in terms of
a reasonable minimum output of coal-fired generation, to

of which 50% is combined heat and power (CHP). As there
is no auxiliary equipment such as electric heat boilers and
heat storage, the regulating range of CHP during the heating
season is only 10-20%, which limits its capability to integrate wind in the system. In some provinces such as Jilin,
the minimum output of the online generators is even higher
than the minimum load of the system, resulting in great difficulties for wind power integration in some periods. But if
reasonable technical and policy measures are put in place,
the capability of the local system to integrate wind can
be enhanced.
Take the northeast China power grid as an example. The
grid-connected wind energy generated in 2013 in the northeast China power grid was 37.2 TWh, and the wind energy
curtailed was 5.9 TWh. The annual curtailment rate was
13.7%. Among the total curtailment, 59% (or 8.1 percentage points of the curtailment rate) was due to the operation
limitation of the CHP units. If technical and policy measures were taken to decrease the current minimum output
of coal-fired generators (which is on average 46% for conventional coal-fired generators and 85% for CHP units) by
eight percentage points, then wind curtailment resulting

Wind Curtailment Rate (%)

13.7%
12.6%
12

11.7%

3.7%
8.1%

6.1%

10.8%

5.1%

10%

2.6%
4.4%

9.2%

8.6%

3.6%

7.9%

7.4%

2.3%

1.8%

5.6%

4
5.6%
0

5.6%

0
1
2
3
4
5
6
7
8
Reduction of the Minimum Output of Coal-Fired Generation from Its Current Level (%)
Curtailment Resulting from High Minimum Output of Conventional Generation
Curtailment Resulting from Transmission Constraints
Total Curtailment

figure 3. The variation of wind curtailment with the reduction of the minimum output of coal-fired generators.
44

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