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A simplified power flow calculation method for distribution network with distributed generation is proposed in this paper. Based on loop analysis method, this proposed calculation method can theoretically transform the complex power flow equations into linear algebraic equations. In addition, node voltages of PV-type and PQ(V)-type distributed generation are calculated by calculating and correcting...
With the high penetration of distributed generation (DG), the power quality, protection and control of the distribution networks will be affected. This paper mainly studies the impacts of DG on both voltage and line loss. To quantitatively evaluate the impacts, a set of quantification indices are adopted. To take comprehensive evaluation of the impacts, a principal component analysis (PCA) method...
This paper theoretically analyzes the frequency spectrum characteristics of the single-phase ground fault in a Petersen-coil grounded distribution network. Different equivalent circuits are analyzed for faults with low transition resistances and with high transition resistances, separately. The analysis concludes that the system makes a transition from an under-damped state to a damping state, and...
The traveling wave protection performance of traditional DC transmission line can be influenced by fault conditions, so this paper proposes a traveling wave based directional pilot protection method. Analysis shows, for an internal DC line fault, that the forward traveling wave is less than the backward traveling wave at two ends of the proposed line within a short time of post-fault; but in the case...
Using the characteristic difference of transient energy, a transient energy based directional unit protection is proposed. Assuming the positive direction of current is from DC busbar to DC line, for an internal line fault, the detected transient energies on both ends of the line are all negative, which denote the positive direction fault. When an external fault occurs, the transient energy on one...
To solve the problems related to configuration and principle of backup protection in conventional substations, a new scheme of Substation-area Differential Backup Protection (abbr. SDBP) oriented to intelligent substations is proposed by this paper. The new scheme takes the whole substation and all connected transmission lines as an object to be protected. Through defining four types of differential...
With the integration of DG, the power flow direction of distribution grid may be changed from single to bidirectional. In this situation, the conventional current protection scheme faces the extreme challenge, even does not meet the requirement of distribution grid with DG. Therefore, this paper proposes a directional pilot protection method to protect the upstream line of DG. Using the fault components...
Micro-grid is suitable for popular utilization of distributed renewable energy generations. It can save grid-connected photovoltaic inverter and some rectifiers for DC loads when connecting photovoltaic generation to local loads by DC micro-grid, and the energy use efficiency increases dramatically. This paper proposed a multiple hierarchical DC micro-grid based on photovoltaic generations. The photovoltaic...
Using propagation characteristics of travelling wave, an extra high speed busbar protection technique is proposed. If a fault occurs on the transmission line, the forward and backward travelling waves will be generated. When a fault occurs on the busbar, the detected initial travelling waves on all lines connected to this busbar will come from their backs, which are positive direction travelling waves...
110kV Pingyin substation of Shandong Electric Power Corporation has reconstructed recently under the requirements of typical intelligent substation. Different from implementing new intelligent substations, intelligent reconstruction of conventional substation faces much more technical and economic issues. The project adopts three-layer network architecture, including process level, bay level and station...
This paper proposes an extra high-speed busbar protection technique according to the propagation theory of traveling wave. When the fault occurs on the busbar, the detected initial traveling waves on all connected lines will come from their back, which are defined as positive direction traveling waves. While a fault occurs on any one of these lines, the detected initial traveling waves on all healthy...
Considering future smart distribution grid (SDG), the protection and control technology of traditional distribution networks is facing new opportunities and challenges. This paper proposes a Multi-Agent System (MAS) based protection and control method for smart distribution grid. The MAS is consist of intelligent distributed terminal (IDT), control master and communication network. Each IDT is regarded...
Intelligent substation is the most important aspect of Smart Grid constructing. There are many problems during intelligent reconstruction of conventional substation, one of which is to add a variety of secondary equipments. To address this problem, the paper puts forward two distributed configuration schemes of secondary devices using the IED with integrated functions of process level and bay level...
The complete digital relays are used increasing widely in recent years, where the traditional analog, hardwired and interface have been replaced by non-conventional instrument transformers and the digital communication link (process bus) based on IEC 61850-9-2 standard. It is shown that these new techniques will make a strong impact on relay performance testing. General methods of testing protective...
A set of scheme of directional unit protection based on travelling wave integral is designed. For main components in this scheme, such as fault phase selection component, fault direction discrimination component, lightning stroke and circuit breaker operation verification, etc., the theoretical analysis and criterion construction and simulation test are all carried out. Simulation data demonstrate...
Distribution network feeders are very different from transmission lines due to more complex structures and more branches. The phase-to-ground faults in distribution network will induce larger transition resistance than in transmission lines. The traditional single-phase-to-ground fault location methods for transmission lines are no longer suitable for the distribution feeders due to the transition...
Lightning stroke on line may lead to mal-operation of relay protection, possibly invades substation, and further results in over-voltage of system. A S-transform based method for monitoring and identifying lightning inrush in substations is proposed in this paper. By monitoring busbar voltage signals in real-time, the waveform characteristics of transient voltage signals in both time domain and frequency...
This paper presents the dead-time elimination scheme for modulating neutral-point-clamped inverter. Unlike the dead-time compensation methods reported for mitigating negative effects induced by dead-time insertion, the proposed scheme simply separates each pair of switches by treating every switch independently and triggers the corresponding switches per phase according to the judged current direction...
The variable dc voltage generated by photovoltaic (PV) array can be harnessed as much as possible through the well-known two-stage inversion in grid-tied configuration, where the controlled dc-link voltage can be maintained stably to ensure the desired low harmonic ac output. Traditionally, the front-end dc Boost converter generally operates to track the maximum power point (MPP) of PV array by directly...
For the digital substation based on IEC61850 communication standards, this paper presents a novel scheme of distributed busbar protection. According to the technical characteristics of digital substation, the configuration of distributed busbar protection without central unit is constructed; the requirements of data communication between merging units (MU) and distributed busbar protection units are...
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