چكيده به لاتين
Today, advances in the use of renewable energy sources, as well as a significant increase in electricity demand, have made DC high voltage power systems have a special place in AC power systems. These networks are integrated with AC power systems for purposes such as transmitting large amounts of electrical energy over long distances and benefits such as connecting large electrical networks to each other. Applying the operating requirements of AC/DC hybrid networks will result to inject the fault current from the DC network to the common connection point during AC disturbances. However, in order to prevent damage to the electronic power equipment used in the voltage source converter (VSC), the current flowing through the converter will be limited to the rated current. This will eventually change the converter fault behavior compared to the fault current characteristic of synchronous generators in terms of magnitude and waveform. Therefore, performance analysis of distance relays due to the different fault behavior of VSC-HVDC is great importance.
This dissertation simulates and investigates the performance of distance relays of AC power systems in presence of offshore wind farms that connected to the AC system via HVDC transmission line based on a voltage source converter (VSC). The current limit for each of the converters is set to 1.1 of the rated current to prevent damage to the electronic power equipment. A simple sample system, an IEEE standard 5-bus and 39-bus system is simulated in PSCAD / EMTDC and DIGSILENT software, and the impedance measured by the primary and backup relays in each is discussed. Various factors such as common connection point or VSC installation point, fault resistance, converter current limit, SIR changes, AC reference voltage and finally gain changes in VSC controllers to reduce the effect of the converter on the fault current are also considered.