Subsynchronous oscillation and its practical mitigation project at the Hulun Buir power plant generating for a Chinese extra-high-voltage AC and DC hybrid transmission network

摘要

In China, subsynchronous oscillation (SSO) appears continually at the Hulun Buir (HB) power plant, which is part of the extra-high-voltage (EHV) AC and DC hybrid transmission networks from the HB League power base to the Northeast. Related closely to the power delivered by the EHVDC link, these oscillations lead to fatigue accumulation, life-time reductions and even failures in the turbogenerators at the HB power plant. After a study of the oscillations, an inverse energy injection method is proposed to suppress the SSO phenomenon. According to the method, a bulk power electronic device is developed that is based on a multilevel voltage source converter to generate inverse energy. The mitigation device is implemented at the HB power plant. Field tests are conducted, and the results demonstrate that the device can depress SSO to levels that exceed the requirements, proving the effectiveness of the mitigation device.