Technical requirements for performance evaluation and conformity assessment of DC collector systems for offshore wind farms

As a new transmission schemes, DC (Direct Current) grid-connected technology has many technical problems to be solved. Among them, in the case of offshore wind power DC transmission system, the transmission capacity is reduced and the active power regulation at the power supply terminal is slow, which will lead to the increase of the system voltage at the sending terminal and threaten the safe operation of the converter and offshore wind turbines at the sending terminal. Aiming at the transient overvoltage problem of traditional DC transmission system, many research results have been obtained and many measures have been put forward. For example, fast cut-off filter, additional control of DC control system, sacrificial arrester and large-capacity arrester are used to improve the voltage level of equipment. However, for offshore wind power transmission system, this problem is still in the preliminary research stage. Compared with the traditional DC transmission system, offshore wind power transmission system has its unique characteristics. Offshore wind turbines have reactive power regulation ability, and the transmission end of flexible direct drive system does not need to install filters, so the converter of flexible direct drive system responds faster. Therefore, it is necessary to master the data analysis technology of the evaluation index system of the DC collector system of offshore wind farms, and integrate the analytic hierarchy process, fuzzy comprehensive evaluation method and Hopfield network evaluation method, and put forward a comprehensive evaluation method of system performance combining multi-dimensional characteristic parameters to form a qualified evaluation scheme.