Page 56 - Mathematical Models and Algorithms for Power System Optimization

46 Chapter 2

Generated output (MW)

Time period (h)
System output after pumped
storage optimization
System output before pumped
storage optimization
Average system output
Fig. 2.14

Optimization calculation results of system output upon daily economic dispatch.

pumped storage plant not only reduces the number of startups and shutdowns of the
thermal power units but also reduces the startup pressure during peak load, improving
the technical economic efficiency of thermal power units. Thus, from both the
perspectives of reducing the startup and shutdown cost of thermal power units and creating
economic benefits from the difference between peak-valley electricity tariffs, the
optimization calculation results can contribute to considerable overall technical and
economic benefits.
(8) Analysis of benefits from optimized operation of the pumped storage plant: according to
electricity tariff benefit and peak load shaving benefit, economic benefits from optimized
operation of the pumped storage plant are briefly summarized as follows:
1. Electricity tariff benefit: Based on peak price of 0.6yuan/kWh and valley price of
0.3yuan/kWh, power generated by the test system in the peak period was 5000MWh
and in the valley period 7500MWh on the day.

Total electricity tariff benefit ¼ 5000 0:6 7500 0:3Þ 1000 ¼ 900;000yuan
ð
Based on the maximum load hours of 4800h (i.e., 200 days per year), the benefits per year
shall be 180 million yuan (200 900,000yuan). Even if including operating cost, the
investment can still be recovered within several years.
2. Peak shaving benefit: the original peak load was 7000MW and the present peak load
is 5244MW, peak shaving by approximately 1756MW. If load shaving of such scale
was realized by standby thermal power units, 2000MW thermal power units could be
installed. In other words, peak load shifting helps defer investment. Based on the