Page 57 - Mathematical Models and Algorithms for Power System Optimization

Daily Economic Dispatch Optimization With Pumped Storage Plant 47

assumption that pumped storage and thermal power investment is 3500yuan/kW, the
total investment for the pumped storage plant of 1200MW is 4.2 billion yuan, which
means the investment for a thermal power plant of 2000MW installed capacity can be
deferred.
3. Reliability benefit: assuming that system outage loss is 10,000yuan/MWh, the power
failure ratio of pumped storage units is less than that of thermal power units. If the
forced interruption ratio of pumped storage units is 0.1%, and that of thermal power
units is 0.39%, energy generated by pumped storage units during peak load period is
5000MWh, so that the reliability benefit per day shall be
Reliability benefit ¼ 0:39% 0:1%Þ 5000 10;000 ¼ 145;000yuan
ð
Accordingly, the reliability benefit per year (operating for 200 days per year) shall be 29 million
yuan (145,000 200).

2.7 Conclusion

A new approach based on mixed-integer programming is proposed for the daily economic
operation planning problem for a multiarea system with hydrothermal plants and a pumped
storage plant. The special treatments for integer variables and virtual cost are effective for
practical problems. The optimization problem can be solved by a standard mixed-integer
programming method or by an approximation method.
The testing system is a large-scale system, where the installed capacity of thermal power units is
10,315MW, hydropower units 924MW, and pumped storage units 1200MW. In the practical
test system, the maximum peak-valley difference was 2650MW before optimization, reduced
to 575MW after optimization. Thus, the proposed optimization model can effectively reduce
the peak-valley difference.

The calculation results show that the approach proposed can be successfully shift the peak of
the load curve through a pumped storage plant, so that the operation condition of the whole
power system can be greatly improved. Whether it is from the reduction of startups and
shutdowns costs of thermal power units or the benefits created by the difference in peak-to-
valley electricity prices, the economic benefits are very substantial.

The main characteristics of the proposed approach are summarized as follows:

(1) The proposed mixed-integer programming model can be directly solved by the mixed-
integer programming method, or approximately solved by the linear
programming method.
(2) It can create validity testing among the basic operating constraints, so as to ensure a
feasible solution in the optimization calculation.