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The medium voltage direct current (MVDC) is a promising direction of future shipboard power system (SPS). However, one of the main limitations encountered in its development is the fault isolation of DC side. This paper reveals the evolution process of short-circuit fault in typical MVDC SPS through equivalent circuit and transient simulation. Based on the analysis of protection needs, a superconducting current-limiting switch (SCLS) topology is proposed, which includes one superconducting coupled coil and two DC circuit breakers (DCCBs). The models of SCLS is built on MATLAB/Simulink and the current limiting principle and current sharing principle of SCLS are verified. The results show that the SCLS has effective current limiting performance and fault clearing effect.

DC fault protection is the bottleneck that restricts the development of modular multilevel converter based high voltage direct current (MMC-HVDC) system. Superconducting fault current limiters (SFCL) is an ideal protection device that can significantly limit short circuit current and enhance the fault tolerance ability of MMC-HVDC system. At present, several topologies of SFCLs have been proposed, but there is no systematical study of their current-limiting characteristics in MMC-HVDC. This paper studies the development process of DC short-circuit faults in MMC-HVDC system, and analyzes its demand for fault current limiting. Then, resistive type, saturated iron core type and hybrid type SFCL are modeled and their limiting effect of critical fault current under DC pole-to-pole fault is tested. By comparison, the current-limiting characteristics of three types of SFCL are concluded. Results show that resistive SFCL has best performance in steady state, while saturated iron core SFCL has best performance in transient state. The current-limiting characteristic of hybrid type SFCL is between the other two types.

As medium voltage dc-based (MVDC) technology is widely considered in the shipboard integrated power system (IPS), the short fault protection of shipboard IPS is urgent. This paper suggests resistive type superconducting fault current limiter (R-SFCL), flux-coupling type SFCL (FC-SFCL), and a hybrid type SFCL (H-SFCL) alleviate fault current and improve the transient behaviors of shipboard MVDC IPS. All of these SFCLs are installed at the DC line. When pole to pole short fault occurs, resistive and inductive components play roles in current limiting. To evaluate these SFCLs and choose one for the system, theoretical analysis, simulation verification and experiments are done. According to the current limiting and economic cost index, H-SFCL is preferable in these SFCLs.

The resistive superconducting fault current limiter (R-SFCL) is considered as a promising protection device to restrict the DC fault current in modular multilevel converter based high voltage direct current (MMC-HVDC) system. One bottleneck of R-SFCL is that it needs to withstand an overcurrent impact during fault, which results in temperature rise and may damage superconducting coils. A shunt resistor connected in parallel with R-SFCL can reduce temperature and protect superconducting coils. However, there are few studies to quantitatively analyze the influence of shunt resistor. This paper applies a novel R-Q method to calculate the quenching resistance of R-SFCL. By combining the R-Q method and finite element method, the system simulation and electromagnetic field analysis are separated, and the calculation feasibility is greatly improved. Then, the effect of shunt resistor in reducing the temperature of R-SFCL is studied. The influence of shunt resistance to the economic and current-limiting performance of R-SFCL is discussed.

With the rapid development of the integrated power system (IPS) on shipboard, the medium voltage DC (MVDC) power distribution system has received widely attention. At present, one of the bottlenecks restricting the development of MVDC IPS for ships is the occurrence of short circuit faults. Short circuit faults not only cause extensive damage to the line hardware, but also cause a lot of losses. Therefore, how to protect system from high-amplitude short circuit fault current has become a hot research topic. In order to ensure that the MVDC IPS of the ship can still operate safely in the event of typical faults, a flux-coupling-type superconducting fault current limiter (SFCL) is applied to shipboard MVDC IPS under two typical short circuit faults. In this paper, a flux-coupling-type SFCL is conceptual and electromagnetic designed, with working principle analyzed and mathematical model established. Two typical types of short-circuit fault are selected in the shipboard MVDC IPS, and the flux-coupling-type SFCL is installed at different positions on two fault short platforms to evaluate its performance. The results show that the flux-coupling-type SFCL has effective current limiting performance on protection of shipboard MVDC IPS.

Operation of isolating switches and circuit breakers in fully enclosed gas insulated substations (GIS) produces very fast transient overvoltage (VFTO). According to IEC61321-1, VFTO contains four f...

Due to the discharge of static electricity, the force of static electricity and the phenomenon of electrostatic induction, it poses a major safety hazard for on-site operations personnel and equipm...

At present, the detection technology of non-contact ultrasonic and transient earth voltage is widely used in the partial discharge detection of switchgear. The test result is directly related to the diagnosis and evaluation of the insulation state of electrical equipment. In order to characterize the accuracy of PD detection, it is proposed to use the terminal linearity calculation to analyze the linearity of the PD detector in the frequency band. Finally, the linearity test of the UltraTEV Plus PD detector is carried out by setting up a dedicated performance test platform in the laboratory, which verifies the effectiveness of the method and reflects the minimum linearity near the resonant frequency.

The Insulated problem, which is caused by very fast transients overvoltage (VFTO) associated with the switch operation of GIS (Gas Insulated Substations), is becoming increasingly serious. According to the linear relationship between electric field intensity and the voltage of the circuit, in this paper describes a method for measurement of VFTO based on electric field measurement. To measurement of VFTO, the data, which is collected by electric field sensor on basis of the electric field change along with the voltage change in GIS switch circuits, will be used for examining the relationship between electric field intensity and the voltage of the circuit, as well as be used for seeking the experimental best-fit. Then, this paper firstly makes theoretical modeling of VFTO, make numerical simulation calculation. Meanwhile, the response characteristics and the frequency band of the electric field sensor were tested by sine sweep test and square-wave response test. Especially, the sensor has the low-f...

The accurate mathematical model of converter is very important in the process of designing high performance switch power. Nonlinear, multimodal and time-varying are the characteristics of the DC-DC converter. So it is necessary to study it in a new way. This paper presents a mathematical model of Boost converter circuit by state space average method. The closed-loop PI controller based on the Boost converter model was designed. The static and dynamic performance of the closed-loop system was tested in Simulink which demonstrated a good behavior of the system to meet the requirements of user.

Gas insulation switchgear (GIS) has been widely used in electrical power systems for decades due to its good compactness and tightness, slight impact on the environment, and long maintenance cycle. However, it has been noticed that the failures of GIS insulation due to very fast transient overvoltages (VFTOs) increases with the increase of voltage levels. In this paper, a generating system of VFTO and standard lightning impulse (SLI) was established. Using the system, the breakdown characteristics of SF 6 gas gaps under VFTO and SLI were studied. The results show that SF 6 gap has polarity effect in both quasi-uniform field and highly inhomogenous electric field. Under quasi-uniform field, the 50% breakdown voltages under VFTO and SLI with positive polarity are higher than those with negative polarity. But for the highly inhomogenous electric field, the polarity effect is remarkable and polarity reversion phenomenon is observed. When the pressure of SF 6 is lower, the 50% breakdown voltages under SLI with negative polarity are higher than those with positive polarity. Nevertheless, the 50% breakdown voltages under SLI with positive polarity are higher than those with negative polarity when the pressure of SF 6 exceeds a critical pressure. The critical pressure decreases with the increase of the electric field non-uniform factor. Based on the analysis, it is concluded that the reasons for polarity effect can be explained by the migration and proliferation of space charge.