| In recent years, Direct Current (DC) transmission technique has been developing rapidly at home and abroad with its advantages increasingly apparent in long distance transmission, grid connection, and flexible scheduling. With the continued improving of environmental awareness, environmental impact will be the key issue that must be taken into consideration of Ultra High Voltage (UHV) DC transmission engineering. And noise pollution neglected in the past has become a major problem that had to be settled in construction planning of UHVDC transmission engineering. Therefore the research in equipment noise of DC converter station is of great significance in ensuring the interests of people and guaranteeing the planning, construction and operation of DC transmission engineering. As the field measurement of sound level should be conducted after the completion of the project construction when noise reduction and the related transformation is costly, it is very important to evaluate the noise level by calculation in project designing.Through testing analysis and research on noise radiation characteristics of major equipment in DC converter station as well as the analysis of common foreign software for noise prediction, this dissertation establishes the database for weighted noise spectrum data of major equipment in DC converter station and acoustic model adapted to calculate audible noise of High Voltage (HV) DC converter station, and makes profound research on the core algorithm and relevant issues in the development and realization of the noise prediction and computation system, thus proposing a specialized noise prediction software with independent intellectual property right and adapted for HVDC converter station. The dissertation finally compares the prediction of the proposed software with the field measurement and the predictions of a number of foreign environmental noise software, which proves the proposed software to be of the same level in precision and practicability as the foreign software.The main work in this dissertation is listed as follows:Firstly, the dissertation introduces the causes of noise generation of major noise source equipment in HVDC converter station. Then, through testing analysis and research on noise radiation characteristics of major equipment in DC converter station, this dissertation separates and revises the superposed noises in the complex sound field of Alternating Current (AC) filter field, and then establishes the database for weighted noise spectrum data of major equipment in DC converter station, which provides important reference data for noise prediction and computation in HVDC converter station and the database establishment of the prediction system. Furthermore, it compares various calculation and measurement methods for sound power determination of major equipment noise in converter station with their respective advantages and disadvantages and puts forward a simple method for measuring the sound power of capacitor.Secondly, it discusses the common algorithm strategies of foreign noise prediction software, proposes the equal-angle scanline algorithm, and researches into the related problems of computational geometry encountered in the algorithm. In addition, through the research on the form of simulated acoustic model of major sound source equipment in the converter station, it simplifies the modeling form of acoustic model without affecting the computation precision, thus providing an important foundation for rapidly and precisely establishing the computational model of audible noise in HVDC converter station.Thirdly, it focuses on the important issues associated with the core algorithm in the noise prediction and computation system. With respective study on problems such as attenuation by barrier, directivity correction, the dissertation improves the commonly used vertical line source algorithm which makes the calculation of vertical line source more accurate and reasonable. It further discusses and researches certain strategies in improving computational efficiency, thus increasing the computing speed of the software.Fourthly, the dissertation describes the development of each system function and related issues according to the main functional modules of the noise prediction and computation system. Additionally, it adds several practical functions such as noise decomposition for converter station to enhance the practicability and researches into the fault tolerance measures of the software.Lastly, based on the computation of the actual cases by the software and similar foreign noise prediction software, it compares the computational noise profiles of the converter station and its surrounding areas and the detailed computational results of noise level at specified points, so as to evaluate the computational precision of the core algorithm of the software, and to provide a basis for further improvement. |
