Distributed renewable energy sources such as wind, solar, and small hydropower of the new distribution network are mainly connected to the grid through distribution lines, which are susceptible to lightning overvoltag...
详细信息
Traveling wave differential protection (TWDP) is based on the traveling wave (TW) propagation characteristics of the physical transmission line and therefore holds unique advantages in the protection of long-distance ...
详细信息
Traveling wave differential protection (TWDP) is based on the traveling wave (TW) propagation characteristics of the physical transmission line and therefore holds unique advantages in the protection of long-distance transmission lines. This paper proposes a practical time-domain TWDP scheme specifically designed for high-voltage direct-current (HVDC) lines and provides both theoretical analysis and field validation. A TWDP device, named TP-03, was developed and underwent laboratory testing. The developed protection device 1) can stay valid under a maximum fault impedance of up to 1000 Omega under the rated +/- 1100 kV voltage level;2) has an operation time of less than 30 ms even with a communication delay of 20 ms. In October 2020, TP-03 devices were first deployed on the Changji-Guquan UHVDC transmission project, which is the highest voltage (+/- 1100 kV), longest distance (3284 km), and largest capacity (rated 12100 MW) transmission project in the world. During its operation, the devices functioned correctly in several internal faults and external disturbance events. This work represents the first field validation of HVDC TWDP and bridges the gap between theoretical research and real-world applications. It confirms that TWDP can serve as the main protection for ultra-long-distance HVDC lines, setting a benchmark for future projects.
Magnetic flux leakage, as a basic physical parameter in power transformer, can be utilized to characterize the status of the winding. And the DC biasing, as a common abnormal operation condition, is caused by solar st...
详细信息
The power system restoration control has a higher uncertainty level than the preventive control of cascading failures. In order to ensure the feasibility of the decision support system of restoration control, a decisi...
详细信息
The power system restoration control has a higher uncertainty level than the preventive control of cascading failures. In order to ensure the feasibility of the decision support system of restoration control, a decision support framework for adaptive restoration control of transmission system is proposed, which can support the coordinated restoration of multiple partitions, coordinated restoration of units and loads, and coordination of multi-partition decision-making process and actual restoration process. The proposed framework is divided into two layers, global coordination layer and partition optimization layer. The upper layer partitions the transmission system according to the power outage scenario, constantly and dynamically adjusts the partitions during the restoration process, and optimizes the time-space decision-making of inter-partition connectivity. For each partition, the lower layer pre-selects restoration targets according to the estimated restoration income, optimizes the corresponding restoration paths, and evaluates the restoration plans according to the expected net income per unit of power consumption. During the restoration process, if the restoration operation such as energizing the outage branch fails, the current restoration plan will be adaptively switched to the sub-optimal one or re-optimized if necessary. The framework includes two operation modes, i.e., the on-line operation mode and training simulation mode, and provides an information interaction interface for collaborative restoration with related distribution systems. The effectiveness and adaptability of the proposed framework is demonstrated by simulations using the modified IEEE 118-bus system.
Recent years, modular multilevel converter (MMC) is one of the most promising topologies applied to high voltage direct current transmission (HVDC). In order to solve the circulating currents caused by structural defe...
详细信息
Recent years, modular multilevel converter (MMC) is one of the most promising topologies applied to high voltage direct current transmission (HVDC). In order to solve the circulating currents caused by structural defects of MMC, a fuzzy adaptive PI circulating current suppressing controller is proposed based on mathematical model of MMC and functioning fuzzy subset inference method: The fuzzy number is calculated according to the error of system state, error variation, membership function and fuzzy control rules; The center of gravity method is used for defuzzification, and finally the PI parameters are modified. Finally, the PSCAD/EMTDC simulation model with fuzzy adaptive PI controller is established. The results show that the fuzzy adaptive PI circulating current suppressing controller is effective for MMC-HVDC.
Conventional transmission line distance protection approaches are subject to malfunction under reverse fault-induced current transformer(CT) saturation for the typically employed breaker-and-a-half configuration. This...
详细信息
Conventional transmission line distance protection approaches are subject to malfunction under reverse fault-induced current transformer(CT) saturation for the typically employed breaker-and-a-half configuration. This paper addresses this issue by proposing a new distance protection approach that combines the blocking and unblocking criteria of distance protection based on the values of incomplete differential current,operation voltage, and current harmonic content. The proposed approach is verified by theoretical analysis, dynamic simulation testing, and field operation to ensure that the obtained distance protection is reliable and refrains from operating unnecessarily under reverse fault-induced CT saturation in the breaker-and-ahalf configuration. Meanwhile, the proposed approach is demonstrated can operate reliably when forward faults occur or various reverse faults are converted to forward faults.
The introduction of power electronic converters has changed the fault characteristics of the traditional power grid. It is difficult for traditional differential protection to meet the protection needs, prone to sensi...
详细信息
The conventional security constraint unit commitment plan is difficult to adapt to the uncertainty of high proportion of renewable energy output, and is easy to cause risks to the real-time power supply-demand balance...
The conventional security constraint unit commitment plan is difficult to adapt to the uncertainty of high proportion of renewable energy output, and is easy to cause risks to the real-time power supply-demand balance and the security of power system operation. Aiming at the requirements of optimization and decision-making for high proportional renewable energy provincial power grid day-ahead scheduling, this paper analyzes the optimization decision-making process of day-ahead scheduling planning considering uncertainties of renewable energy, and proposes a renewable energy output scenario set generation method based on renewable energy power forecast and forecast error probability distribution. A day-ahead stochastic unit commitment optimization model and algorithm considering the uncertainty of renewable energy and power system operation risk is established. The effectiveness and practicability of the proposed method are verified based on the day-ahead actual operation data of a provincial power grid.
The volatility and uncertainty of wind power bring severe challenges to the power system, and the modeling of multi-wind farm output scenarios considering the uncertainty of wind power is of great significance in powe...
The volatility and uncertainty of wind power bring severe challenges to the power system, and the modeling of multi-wind farm output scenarios considering the uncertainty of wind power is of great significance in power system dispatching decision-making. Especially for area/ province with abundant wind power resources, where the reliability of the dispatching plan can be strongly affected by the volatility of large amount of wind power. In this paper, a practical method of generating probabilistic scenarios for day-ahead wind power output is proposed for provincial power grid with high proportion of wind power. Firstly, the K-Shape clustering algorithm is used to cluster the wind farm stations, and then the output scenario are generated by using the total wind power forecast value and forecast error probability distribution characteristics of each aggregated station. After arrangement and combination of the aggregated stations’ scenes, the scenario minimization based on probability distance was conducted for clustering reduction to obtain the typical output scenes, and then the typical output scenes were assigned to each station according to the forecast value of the station to obtain the probability output scenes of each station. It is verified by actual power grid data that the scenarios generated by this method can combine with wind power predictions to well depict the random fluctuation of multi-wind farms output and has a good application prospect in the practice of day-ahead dispatching decision making.
In the construction of clean and low-carbon community energy management systems, the challenges of the new era of low-carbon community development lie in monitoring and utilizing the massive panoramic information obta...
详细信息
暂无评论