The Formation Principle And The Limitation Of The Harmonic In The Gaode Transformer Substation

With the development of national economy, the high power quality is needed. At the same time, a lot of large capacity nonlinear, impactive and unbalanced loads are used more and more in the power system, so the harmonic waves which do harms to the power system quality are increasing. The employing D-STATCOM in the power grid, which can compensate reactive power and limit the voltage distortion, is an effective way to improve power quality. So the study on the industrialization of D-STATCOM is an important trend of DFACTS nowadays. This paper focuses on the industrialization of D-STATCOM and optimal design for reducing equipment power loss.First, the formation principle of harmonic is analyzed in detail, then the harmonics of a operating transformer substation in Gaode district , A region in the city of Beihai, are measured and analyzed carefully, and according to the reality condition, a D-STATCOM was used to limit the harmonic distortion in this transformer substation.First, an equivalent system for the three lines three phases system was established, the a-b-c direct generating pulses algorithm was presented. The load currents were measured, then according to the Instantaneous Reactive Theory, the system reference current being compensated w as c alculated, so the expected current of D-STATCOM was obtained from difference of the reference current and load current, as a consequence, the expected voltage of D-STATCOM was obtained, the desired pulse sequences were calculated under the a-b-c axis.This algorithm simplifies the complexity of the SVPWM, avoiding the influence of the system unbalance, so the measuring was realized easily. This is good for the digital control system. The experiment results show that it can limit the harmonic distortion effectively.The optimization of design of reactor and pulse sequences were also presented to reduce equipment losses.Some simulation and testing experiment of D-STATCOM was done in the Petrochemical factory, which is the main harmonic source in the Gaode transformer substation .Experiment results show that power qualities were improved due to the reactive compensation and the limitation of the harmonic distortion, and the D-STATCOM could be used practically in the industry, it meets the specification of national standard, it can be industrial applied basically.