Papers by Keyword: PSCAD/EMTDC

Abstract: This paper proposes a new technique of using discrete wavelet transform (DWT) and back-propagation neural network (BPNN) based on Clarke’s transformation for fault classification and detection on a single circuit transmission line. Simulation and training process for the neural network are done by using PSCAD / EMTDC and MATLAB. Daubechies4 mother wavelet (DB4) is used to decompose the high frequency components of these signals. The wavelet transform coefficients (WTC) and wavelet energy coefficients (WEC) for classification fault and detect patterns used as input for neural network training back-propagation (BPNN). This information is then fed into a neural network to classify the fault condition. A DWT with quasi optimal performance for preprocessing stage are presented. This study also includes a comparison of the results of training BPPN and DWT with and without Clarke’s transformation, where the results show that using Clarke transformation in training will give in a smaller mean square error (MSE) and mean absolute error (MAE). The simulation also shows that the new algorithm is more reliable and accurate.

Abstract: As the main types of parallel FACTS devices, the basic function of SVC and STATCOM is to realize the dynamic compensation of reactive power and maintain system voltage stability. However, when new control strategies are added to them .Both of them can suppress SSO effectively. Based on IEEE first benchmark model, this paper established simulation model by PSCAD/EMTDC. The effects of suppressing SSO by SVC/STATCOM are verified with time domain simulation, and the comparative analyses are carried out on the effects of suppressing SSO by SVC and STATCOM.

Abstract: To explore the self-excitation risks in weak interconnection power grid from the wind power flow, a vector control model of variable speed wind turbine based on doubly fed induction generator (DFIG) is established using electromagnetic transient simulation software PSCAD/ EMTDC. Start from the basic circuit model, the self-excitation phenomenon is analyzed with wind power integration. Simulation results show that the effect of wind power integration on the self-excitation risk is mainly determined by DFIG’s operation method, and wind power integration will affect self-excitation engineering judgment method at the same time. When DFIG works in phase late operation or has no reactive power exchange with the main power grid, cutting the wind turbine after broken thread quickly can restrain the worsening trend to a certain extent. However cutting the wind turbine after broken thread when DFIG works in phase advance operation may cause a voltage jump of the hydraulic synchronous generator in parallel with the wind turbine.

Abstract: There is not a component which can implement the algorithm of space vector pulse width modulation (SVPWM) in the PSCAD/EMTDC. The principle of SVPWM is explained firstly. Then the creating process of the self-defined component and the program flowchart of SVPWM are presented. The algorithms of the subroutine are also discussed in detail. Finally, the simulation is performed by using the self-defined component in the system. Simulation results demonstrate the correctness and validity of the inverter and self-defined component.

Abstract: In this paper, it uses PSCAD/EMTDC to build simulation system of STATCOM (Static Synchronous Compensator). According to the principle of coordinate transformation and the theory of instantaneous reactive power, it creates self-defined components in PSCAD/EMTDC. The working principle of the system is explained fistly.Then the theory of instantaneous reactive power and the diagram of simulation system is presented. Each functional module is also discussed in detail. Through the simulation test, it emphatically analyzes real-time tracking ability of the system when the capacitive and inductive loads are added. In this way, correctness and validity of the system has been proved.

Abstract: When the HVDC works in mono-polar operation or bipolar unbalanced operation, DC flows through the neutral point and causes DC bias magnetic of transformer around HVDC grounding electrode, which influences the operation security of transformers. Beside highly saturated core, it also causes the distortion of exciting current, increasing harmonics and leakage magnetic flux, and thus the losses, which in turn results in the structures of transformer overheating and insulation aging. Based on the principle of transformer DC bias magnetic and UMEC of transformer in PSCAD/EMTDC, electromagnetic transient simulation platform of transformer DC bias magnetic is built. Considering the effect of DC bias magnetic on different structure of transformer, three kinds of typical transformer that has been widely applied are selected including three-phase three-limb transformer, three-phase five-limb transformer, three-phase bank transformer. After comparing the differences between these three kinds of transformer, related parameters are set such as the core structure and mode of winding connection and so on.

Abstract: Continuous co-phase traction power supply system is the major change of the traction power supply. It is important to analyze the transient response characteristics of overhead contact line for the traction substation feeder protection. This article introduces the main structure of continuous co-phase traction power supply system and the control strategy of traction substation. Meanwhile, transient responses of overhead contact line in the earth short circuit are studied, including metallic earth short circuit and non-metallic earth short circuit (high resistance ground). In the PSCAD/EMTDC electromagnetic transient simulation environment, the effects on the system and the recovery process are studied which the fault occurred in the output interface of traction substation and occurred in overhead contact line.

Abstract: In this paper, the series converters of Distributed Power Flow Controller are the main object of study. Its mechanism of suppressing power system oscillations is studied by theoretical analysis and formula derivation, which relies on a single-machine infinite-bus power system, installed the series converters. Then based on the mechanism, adopting the classic PI control and the damping controller, designed the transient stability control loop for the series converters. Finally, simulations performed by PSCAD/EMTDC, the results show that DPFC device can effectively suppress oscillation and improve system stability.

Abstract: This paper introduces the topology and working principle of modular multilevel converter, simplifying its equivalent circuit before obtaining virtual equipotential. On the ground of the theoretical model of equivalent circuit, MMC-HVDC could adapt the same control strategy as the traditional method. So, on the platform of PSCAD/EMTDC, an eleven level MMC Dual-infeed HVDC system is established and nearest level modulation is adopted as its control strategy to sort voltage sharing of the modules. Experimental results prove the validity of the proposed model.

Abstract: Power generation becomes a main way of using new energy. However, the access of distributed generation(DG) causes the ordinary protection system develop a series of problems. In this paper, the structure of distribution network with DG is introduced firstly.Secondly,it is analysed that the effect that DG brings to distribution network protection, and then a new protection scheme of distribution network with DG is put forward. The segment I, II of direction three-current protection on the line which is at the upstream of DG, and the next line’s segment I, II consists of a simple communication unit. Through the comprehensive judgment of two protections’ action results, fault can be isolated in minimum range quickly and accurately. Finally, the correctness and feasibility of the new protection principle are verified by simulating a 10KV distribution system.