Search

The commission of QINGYU HVDC brings a large amount of clean power to Henan province, which increases the flexibility of the system operation and the complexity of the ACDC system operation. The strong HVDC and weak AC contradiction of the power grid is prominent, which is prone to commutation failure and threatens the safe and stable operation of the power grid. Aiming at continuous commutation failure of “strong HVDC and weak AC” receiving-end system, the paper analyzes the mechanism of commutation failure and the influence of control strategy on transient characteristics of multi-fed DC system, and proposes an improved VDCOL control strategy to effectively reduce the probability of continuous commutation failure and improve the recovery speed.

With the continuous development of power grids, the scale of supercomputing clusters has also gradually increased to carry a large number of power system simulation calculations, and the problem of high energy consumption has appeared. To solve this problem, we propose a container virtualization-based supercomputing cluster for power system. We analyze the impact of containers on power simulation calculations and compare the energy consumption effects of various container scheduling and migration algorithms on clusters. Experiments show that compared to virtual machines with hypervisor, which consumes massive resources and reduces performances by 28.4%, the performance degradation of container on power simulation calculation is 1.3%, which can be ignored. The energy consumption of load-concentration or resource-and-load-balance container scheduling algorithms is up to 4.0% lower and at least 2.2% lower than other algorithms. In container migration, the method combining autoregressive model with most-correlation and resource-andload-balance algorithms is better than other methods, which not only minimizes energy consumption, but also has lowest number of migrations and SLA violations. Experiments verify the feasibility and advantages of container migration in power system computing clusters.

The inrush current generated in the process of no-load closing of transformer is not only prone to misoperation of transformer relay protection, but also has adverse effects on transformer equipment and power grid. This includes adverse effects on the commutation process of the High Voltage Direct Current (HVDC) transmission system. The main manifestation is the influence of harmonic voltage and fundamental voltage changes caused by inrush current on the commutation process of inverter’s AC bus. In serious cases, it may lead to commutation failure of the HVDC system or even the continuous commutation failure. In this paper, at first, the influence mechanism of commutation failure of HVDC system caused by inrush current is discussed. On this basis, multi-principal elements model analysis method is proposed to analyze the distortion of the inverter’s AC bus voltage when the no-load transformer is closed at different positions. In this paper, the DC system model is built in PSCAD/EMTDC. For the built model, the no-load closing operation is carried out at different positions of the AC grid, and the influence degree of the bus voltage of the converter station caused by each harmonic wave is calculated, and is characterized the risk of commutation failure. In addition, the relevant measurements to suppress the inrush current are simulated and analyzed. It is of great significance to further ensure the safe and stable operation of the power grid.

In this paper, it is focused on test and assessment of low voltage ride through characteristics of electrochemical energy storage system. Based on the national standard GB/T 36547-2018: technical rule for electrochemical energy storage system connected to power grid, this paper proposes a test and evaluation method for the low voltage ride through characteristics of EESS, and carries out a case analysis based on test data of experimental system to verify the feasibility and effectiveness of the method.

With the addition of new distributed energy sources, a new and more accurate load model need to be established. Based on MATLAB/Simulink, this paper researches on the modeling and simulating of photovoltaic power generation system and battery energy storage and their equivalent model. First, a detailed model of the photovoltaic system is built. Boost circuit and MPPT control are selected on the DC side of photovoltaic power generation system. The double closed loop control method of current internal loop and external voltage loop is used for grid inverter control. The model is improved considering the capability of LVRT (low voltage ride through). Based on the above precise models, the model is equaled. The equivalent transfer function is calculated by the grid connected control loop, so the model is simplified. The battery energy storage module establishes a general mathematical model based on the charging and discharging principle. Charge and discharge are controlled through the DC/DC converter. And it is connected to the power grid after inverting and filtering. The common PQ control are selected in the inverter control mode. According to the same principle, the energy storage model is equaled. Finally, based on the traditional load model, the above load model is added to set up a new generalized integrated load model. And the actual model is replaced to build up an equivalent model. The equivalent model is compared with the actual model to verify the equivalent description ability.