A digital modular protection for wind energy conversion systems with battery storage
University of New Brunswick
During the past few decades, there has been a substantial increase in the global installed wind energy capacity that is driven by growing demands for clean and sustainable energy sources. This has triggered rapid advancements in the technologies employed for wind energy conversion systems (WECS) to ensure reliable and stable integration into power systems. Increasing numbers of interconnected WECSs have created several challenges that can adversely impact the operation, control, and stability of the power system. These challenges have been addressed by several industrial codes aiming to minimize the possible impacts of interconnecting WECSs to their host power systems. The focus of such codes is to satisfy the requirements of cottage and frequency stability under the intermittent power production by WECSs. Industrial codes have also identified the deployment of energy storage systems (ESSs) to mitigate variations in power injected by WECSs. Control and protection of ESSs must ensure reliable operation, where response to any undesired even test be initiated with minimum disruption in the power injected to the host power system. The technologies utilized in WECSs are heavily dependent on power electronic converters (PECS) to facilitate extracting power for the wind, and to regulate the power injected to the host power system. On one hand, standardized designs of PECs require featuring them with built-in protection to limit the current flow and attenuate voltage transients across the switching elements. On the other hand, the controllers employed in WECSs and their ESSs operate PECs to meet the requirements of voltage and frequency stability as per the industrial codes. Built-in protection and controller actions can result in non-conventional behaviors of fault currents, this complicating the detection of faults involving a WECS and/or its ESS. A common protection practice for WECS and ESS is to coordinate the responses of multiple protective devices used in WECSs and their ESSs. The main challenge for the coordinated protection in WECSs with ESSs, is due to the use of several PECs, which can alter fault currents. In addition, conventional protective devices suffer limited accuracy in detecting faults involving PECs, where ineffective coordination can result in mal-function of protective devices. This research work aims to develop, implement, and test a new method for managing the responses of multiple protective devices employed in a WECS with ESSs. The proposed method is based on deploying multiple digital protective devices, each of which provides protection to a specific component in the WECS and its ESS. Each protective device is featured with phaselet-based fault detection, which can offer accurate, fast, and reliable detection of faults. The use of the a phaselet-based digital protective devices can help implement a reliable management of protection responses to isolate the faulty component(s). The proposed management of protection responses is called the digital modular protection, which is developed to have its outputs as signals to operate circuit breakers in different parts of the protected WECS and its ESS. The digital modular protection is implemented for performance testing on a WECS that has a battery-bank style storage system. Performance tests are conducted for various fault and non-fault events. Test results demonstrate accurate, fast, and reliable responses for fault and non-fault events with negligible sensitivity to the type and/or location of faults.