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To decrease the initial investment of the compensation system in distribution networks, this paper proposes a cascaded distribution static synchronous compensator (DSTATCOM) integrated with D-y connection distribution transformer for reactive power compensation. The cascaded H-bridge DSTATCOM is connected to a group vertex-taps on the primary windings of the D-y connection distribution transformer,...
When faults or disturbance occurs in AC/DC hybrid complex power grid, there have happened many generator, transformer and transmission line differential protection maloperation accidents caused by current transformer (CT) saturation, which seriously threaten the safe and stable operation of grid. As the analytical analysis of CT transient characteristics is very complex, it is urgent to develop the...
For the construction of the smart grid, protection needs to be accurately measured, and the current transformer needs to correctly transfer the transient process. The transient process of nonlinear ferromagnetic elements mainly includes the transformer inrush current and CT saturation. Differential protection misoperation is rarely caused by a single factor. It involves the coupling effect between...
Urban power grid is a typical load center. According to the operational characteristics and structure of urban power grid, a complete set of urban grid operation risk index system where the calculation methods of each affiliated index is given, is proposed from the point of equipment direct loss, grid structure integrity failure, grid security margin and power grid load loss. On this basis, the paper...
Traditional automatic bus transfer methods have difficulty in correctly telling whether it is short-circuit fault or incoming line tripping by security and stability control devices which leads to bus voltage losing. It may cause automatic bus transfer device incorrect operation or refusing action, which effects the stable operation of the power system and reliability of power supply. This paper proposes...
Under the existing 3/2 connection mode, the incompletion between the configuration of the protection and transformer leads to the existence of the dead zone. When the fault occurs in the dead zone, line protection and breaker failure protection are generally matched with each other to achieve the complete isolation of the fault. This approach will make the scope of the circuit breaker to expand, and...
Natural disasters may wreak havoc on overhead transmission lines and cause communication outage of pilot protection. This paper proposes a communication channel reconstruction method based on wireless sensor network (WSN) modules of monitoring system. To meet the needs of pilot protection's time delay, a novel routing protocol for WSN is proposed based on GPS. It has three stages including route list...
This paper proposes a practical connection approach for distribution static synchronous compensator (DSTATCOM). DSTATCOM is connected to the system through a center-tapped distribution transformer for reactive power compensation. The voltage stress is reduced by half and the number of the cascaded cells is decreased. The mathematical model of the system is established referring to the autotransformer...
Comparing to the traditional generator, wind turbines have special short circuit current traits, which gives rise to many new problems in power system's protection control. Traditional protection methods can't meet the requirement of the safe operation of the power system. This paper firstly analyzes the double feed induction generator. Then for the typical wind farms, the effect of the collective...
This paper proposes a comprehensive compensation strategy for DSTATCOM which is suitable for both reactive power compensation and harmonic elimination in distribution network. The DSTATCOM is connected with the transformer taps on the high voltage (HV) windings and the transformer adopts the Dyn11 connection group. Firstly, according to the converter model, the decoupled control strategy is presented...
This paper deals with a novel control method for D-STATCOM with LCL filter. LCL filter can effectively attenuate high frequency harmonic of compensation current. By taking the energy dissipation properties of STATCOM with LCL filter into consideration, this paper proposes passivity based control method with Euler-Lagrangian (EL) model and damping injection. The stability of the controllers is analyzed...
This paper presents a novel cascaded multilevel converter (CMC)-based distribution-type STATCOM integrated with distribution transformer for medium voltage application. The star-connected, n-level CMC is connected to the winding taps on the primary windings of the transformer to achieve voltage stress reduction and maintain a flexible connection voltage level. Taking full use of the spare capacity...
In the typical HVDC power system, the current transformers (CTs) between the Y-delta converter transformer and the converter bridge is located in the delta-winding of the transformer. Under such condition, the measuring current of these CTs includes the zero-sequence circulating current of the delta-winding. In the case of the adjacent transformer energization or the fault of AC system, the zero-sequence...
This paper analyses the mechanism of the sympathetic inrush current of the converter transformer of the HVDC transmission system. The impacting factors of the sympathetic inrush current, including the system impedance, the closing angle and the initial remnant flux of the incoming transformer, and the operating condition of the HVDC system and so on, are analysed utilizing on the PSCAD/EMTDC soft...
This paper has carried out a research on the user-defined modeling of the trigger control module of HVDC converter based on ADPSS/ETSDAC simulation platform is carried out in this paper. A detailed digital simulation model is also constructed. Firstly, an electromagnetic transient simulation model of the HVDC primary system is put up on the ADPSS/ETSDAC simulation platform. On this basis, user-defined...
Combining switching characteristics of power electronic devices and state transitions in carrier phase-shifted SPWM (CPS-SPWM), this paper uses graphic Stateflow toolbox of Matlab/Simulink to design the process of CPS-SPWM. Then it is applied to STATCOM which is integrated with distribution transformer (DT-STATCOM) for PWM signal generation. Simulation results are presented to prove that the method...
This article use adjustment dead zone, difference coefficient, lag time, stable time and contribution rate to construct the primary frequency index system and use WAMS data to analyze the generator primary frequency index calculation methods. At last, this paper uses the analytical hierarchy process (AHP) and entropy weight comprehensive evaluation methods to evaluate the generator primary frequency...
Due to the absence of the effective identification and coping approaches of the sympathetic inrush current, the mal-operation of differential protection may be occasionally caused by sympathetic inrush current. In order to address this issue, the features of the sympathetic inrush current and the influence of the sympathetic inrush current on the differential protection are analyzed in detail in this...
The analysis of the current transformer transient saturation characteristic and its impact on differential current protection is an urgent problem to be solved. A simulation platform for analyzing the transient characteristic of the current transformer is introduced in this paper. The actual operating scene can be constructed in this platform in order to perform the complex transient process of power...
Current differential protection is the main protection of transmission lines including multi-circuit lines, whose sensitivity and reliability is mainly affected by the distributed capacitive current, especially with the widespread application of segment parallel transmission lines, the relationship of the electrostatic coupling between the circuits is more complicated, which makes the distributed...
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