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In recent years, with development of smart grid and proposing of energy internet, fiber optic current transformer (FOCT) also develops rapidly, and becomes the main direction of current transformer. The transient performance of FOCT is to measure the transient process of power system accurately. However, researchers often ignore the transient performance, or can't simulate the actual transient situation...
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 introduces an analytical method of DC trip accident in Nan'ao VSC-MTDC Project. The inductive method is used to sum up the relevant factors, and then the possible fault causes are eliminated by deduction method, then assume the fault was caused by Valve control system. The correctness of the method and conclusion is verified by simulation experiments. The analysis can be used as a reference...
With the worldwide realization and application of High Voltage Direct Current (HVDC), the additional effects of HVDC transmission technology on power system have caused extensive concern. The DC magnetic bias caused by HVDC may exacerbate the saturation degree of the current transformer (CT) during the external fault, which probably leads to the mal-operation of the transformer differential protection...
Converter valve is the key equipment in HVDC project, and its performance has a tremendous influence on the reliability, stability and efficiency of the whole power system. Thyristor level unit is the basic unit of HVDC converter valve, so each thyristor level unit needs to be tested routinely before the operation of the power system, which results in huge workloads and high costs. At present, there...
The paper presents a comparative study of damping control function of coordinated designed multiple damping controllers which are added to two different types of the UPFC — phase angle controlled and vector controlled UPFC. Firstly in the paper, an introduction is presented to illustrate the structure and operational principle of phase angle controlled and vector controlled UPFC. Secondly, two main...
This paper conducts an in-depth study on the damping characteristics of the damping controller added on the UPFC when two different control strategies are applied (vector control strategy and phase angle control strategy). Firstly, the structure of the UPFC and the principle of the vector and phase angle control strategy are presented in this paper. Then the linearized model of the system with a UPFC...
The most important feature of the Unified Power Flow Controller UPFC is its multi-control functions to maintain the voltage and to regulate power flow at the substation where it is installed. There might exist dynamic interactions among the multiple control functions of the UPFC which could impose difficulty in the design of the control algorithm. This has been investigated previously for a phase-angle...
DC circuit breakers (DCCB) are critical for reliable operation of High Voltage Direct Current (HVDC) networks and for DC fault isolation in a timely manner in order to allow continued power transmission on the healthy parts of a network following fault clearance. Previous studies show that the speed requirement for DCCBs to clear DC faults, and the critical fault clearing time of individual DCCBs...
This article summarizes the proposing and development of DC-DC autotransformer (DC AUTO), a new type of DC-DC converter. The prior art of DC AUTO is firstly described, and then the development of DC AUTO and its supported technologies are summarized. Analogy between AC autotransformer and DC AUTO is investigated. The converter cost and power loss ratio of DC AUTO with bidirectional DC fault isolating...
The quality of power system operating need to assess maturity of small oscillation stability issues of regional power grid thoroughly, analysis level of operating, controller installation allocating and parameter optimization scheme from different develop stage of regional power grid accurately. The assessment scheme is based on damping torque analysis of real large scale power system. Small oscillation...
In order to realize the detection of internal defect in composite insulator, we presented a non-destructive testing method based on microwave, which utilizes the micro wave's refraction and reflection features on the interfaces of different dielectrics. Based on electromagnetic field theory, analysis of the reflected signal amplitude under different conditions were made, which proves the feasibility...
This paper has focused on the ±10 kV/1 kA medium voltage DC distribution system simulation and analysis. Firstly, parameters and the topology of the middle-voltage DC system simulation model is proposed. Then, with the application of DC circuit breaker, the interpoles fault transient situations of DC system are analyzed in PSCAD/EMTDC. Finally, the influence of various system parameters is discussed...
Multi-terminal Voltage-Sourced Converter (VSC) High Voltage Direct Current (HVDC) transmission is expected to play a key role in future power transmission grids. Compared with AC transmission, DC transmission is more vulnerable to faults due to the lower DC side impedances and sensitive power electronics used in the converters. DC protection issues must be solved before any multi-terminal VSC-HVDC...
This paper presents an optimal reactive power control in isolated modular DC/DC converter (IMDCC) system based on theoretical and simulated discussions. The system configuration ties two DC grids by using two modular multilevel converters (MMCs) via an AC transformer, which causes the reactive power consuming and will affect the transferrable active power. Then the discussions conclude that the maximum...
The helicopter live-line work is one of the most important technical measures adopted in the technical field of operation and maintenance on the electric transmission lines. In order to provide technical parameters and to ensure its safety for helicopter live-line work on 1000 kV transmission lines, the typical working conditions of actual operation was arranged with full-scale simulated helicopter...
In this paper, a control strategy of STATCOM for suppressing subsynchronous oscillation (SSO) is proposed. The torsional vibration signal is firstly filtered through bandpass filter with low phase shift so that each torsional mode of the shaft system can be extracted. Afterwards, the phases of the extracted signals are respectively compensated and the amplitudes are amplified. In the end, the treated...
Aiming at non-parallel AC/DC systems, this paper studies the mechanism in system structure for HVDC power modulation to suppress low frequency oscillation. Through the equivalent circuit analysis of a typical non-parallel AC/DC system, the key factor that influences the HVDC modulation effectiveness is revealed. The paper introduces the extended residue ratio as the selection rule for the input signal...
The hybrid reactive compensation is expected to be applied in UHV transmission lines in the future, and its mutual influence with power grid is urgent to be studied. Considering the influence of the ground stray capacitance of the series compensation devices, the disposal scheme, and the installation position et al., the influence to the out-of-phase fault by the hybrid reactive compensation was computational...
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