The Harmonic Compensation On AC Side Of HVDC

This paper studies the harmonic compensation on AC side of HVDC system. The main contents are as the follows:1. The harmonic characteristics of FIVDC system and the shortcomings of the passive filters (PF) currently used on AC side of HVDC are analyzed briefly.2. A FIVDC model based on the CIGRE HVDC benchmark model is built.3. The principles and characteristics of active power filters (APF) are analyzed, and based on that the hybrid active power filters (HAPF) are introduced.4. The harmonic detection theories of APF are analyzed. The p-q theory and the ip-iq theory are simulated and compared with each other by the simulation program of PSCAD/EMTDC. The conclusion is: The ip-iq theory is more precise than the p-q theory on the steady state, but it reverses in the transient state.5. The principle of pulse width modulation (PWM) is analyzed. A PWM circuit model is set and its characteristics are simulated by PSCAD/EMTDC.6. A HAPF model is established by PSCAD/EMTDC, and a series of simulations are carried out. The conclusions are: 〤ompared with PF, the filtering performance is improved obviously with HAPF . 〢fter improving the modulation performance of PWM circuit, the filtering performance of HAPF can be improved further.(3)Although the p-q theory is much more precise than the ip-iq theory, but it is not important in improving the filtering performance of parallel HAPF.7. Further study is performed on the principle of HAPF. A new HAPF is proposed, and the filtering performance of HAPF is also analyzed theoretically. The results indicate that the harmonics can be filtered further, and the resonance between passive filter and system impedance can be eliminated completely.The studies presented in this thesis is useful to Power Grid Companies to improve electric quality and is also useful to power equipment manufactures to develop their products.