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Patent
State Grid Corporation of China, Zhejiang Electrical Power Test and Research Institute | Date: 2017-05-24

An MMC-HVDC system and an isolation device and isolation method for a direct current of the MMC-HVDC system are provided. The isolation device includes first isolation switches, current transfer switches, input and output terminals and a direct current breaker. One terminal of the direct current breaker is grounded and the other terminal of the direct current breaker is connected to all of the first isolation switches. Each of the first isolation switches is connected to one of the input and output terminal via one of the current transfer switches. Each of the current transfer switches includes a first arrester and one of a first IGBT group and an H-bridge group connected to the first arrester in parallel. The first IGBT group includes N first IGBTs and N second IGBTs. The H-bridge group includes N H-bridge circuits connected in series to each other, and each of the H-bridge circuit includes one first capacitor and four third IGBTs. NkU_(0)/U_(1), N Z. The isolation device can isolate the MMC and multiple direct current lines from the MMC-HVDC system, and save an investment cost of a power grid.


Zhao B.,Zhejiang Electrical Power Test and Research Institute | Zhang X.,Zhejiang Electrical Power Test and Research Institute | Li P.,Zhejiang Electrical Power Test and Research Institute | Wang K.,Zhejiang Electrical Power Test and Research Institute | And 2 more authors.
Applied Energy | Year: 2014

An optimal unit sizing method is presented for stand-alone microgrids with practical system and component life-cycle considerations. The proposed method has been applied to the design and development of a real microgrid system on Dongfushan Island, Zhejiang Province, China, consisting of wind turbine generators, solar panels, diesel generators and battery storage units. A genetic algorithm (GA)-based method is used to solve the sizing optimization problem with multiple objectives including the minimization of life-cycle cost, the maximization of renewable energy source penetration and the minimization of pollutant emissions. The actual system configuration and the operating strategy are discussed in detail in this paper, as well as the operational experience regarding the unique microgrid issues observed and lessons learned that may be useful for future microgrid design and development. © 2013 Elsevier Ltd.


Wang S.-H.,Zhejiang Electrical Power Test and Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2011

Based on the length variation as a result of galloping, in this paper, the varying tensile force of conductors was calculated, and the influences of galloping amplitude, number of loops, span and sag on varying tensile force were analyzed. The results show that both the horizontal tension and the vertical component of the axial tension at the suspension point increase with the increase of the galloping amplitude, the decrease of span, and the increase of the sag. The one-loop galloping can lead to the most extensive variation range. The parity of the number of loops has great influence on the relative variation ratio. The deflection of insulator sting as a result of severe conductor galloping may greatly decrease clearance distance between the conductors and cross arm.


Wang S.-H.,Zhejiang Electrical Power Test and Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2010

Atmospheric ice deposits on transmission lines are of great danger to the security of service of electrical power system. Based on several typical severe ice accidents occurring in China, this paper summarizes and analyzes the characteristics, reasons and preventing techniques of severe ice accidents. The results show that the ice accidents occurring in China have such characteristics as large coverage area, coexistence of mechanical failures and electrical failures, etc. Overload caused by the severe icing, tensile force difference caused by asymmetrical icing or asynchronous ice shedding, ice flashovers, and conductor galloping are the main reasons for ice accidents. Anti-icing, anti-flashovers, and anti-galloping are the main technical orientation of preventing transmission lines from severe ice accidents.


Zhao B.,Zhejiang Electrical Power Test and Research Institute | Zhang X.,Zhejiang Electrical Power Test and Research Institute | Chen J.,Tianjin University
IEEE Transactions on Power Systems | Year: 2012

The paper presents an integrated microgrid laboratory system with a flexible and reliable multimicrogrid structure; it contains multiple distributed generation systems and energy storage systems and integrates with a diesel generator that serves as a back-up power source and flywheel energy storage for fast balancing to provide uninterruptible power-supply services in cooperation with the diesel generator. The microgrid system, by adopting the master-slave control strategy, can be transited flexibly between grid-connected and islanded modes and can be disconnected from the utility when a fault occurs or the power quality falls below specified standards. The developed bi-directional inverter which is applied in the system plays an important role. The small microgrids of this system are intended to operate separately or in the form of one large microgrid with a certain switch status. Furthermore, experiments on control, protection, and other technologies have been carried out. The results show that the operation conditions meet the related IEEE Standard 1547 and power quality requirements. The integrated microgrid laboratory system is able to operate stably and reliably under different conditions, including mode transition and fault events. © 1969-2012 IEEE.


Wang S.-H.,Zhejiang Electrical Power Test and Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2012

To understand the aerodynamic characteristics of an iced conductor under wind load, the air flow field around the iced conductor was simulated with the software Fluent. The lift coefficient, drag coefficient and torsional coefficient under different attack angles were calculated for the iced conductors with different ice thickness. The influences of ice thickness and wind speed on the aerodynamic parameters of iced conductors were obtained. The results show that the ice thickness exerts significant influence on the drag coefficient, lift coefficient and torsional coefficient. The wind velocity exerts great influence on the drag coefficient, but slight influence on lift coefficient and torsional coefficient. The computation results may facilitate the research of conductor galloping.


Patent
Zhejiang Electrical Power Test, Research Institute, State Grid Corporation of China and NR Electrical Co. | Date: 2016-04-13

A low-frequency band suppression enhanced anti-reversal power system stabilizer is presented by the invention. Currently the widely used PSS2B power system stabilizer needs lead elements above Order 2 to meet the phase compensation requirement of DC blocking signal of active power, thus quickly increasing high-frequency band gain, restricting allowable total setting gain of PSS, limiting low-band gain and reducing low-frequency band suppression ability of power system stabilizer. The invention will add generator speed signal (which is treated by DC blocking element and corrected by parallel proportional differential PD) and active power signal P_(e )(which is treated by DC blocking element and gained by gain factor K_(s3)) to get equivalent synthetic mechanical power of power system stabilizer. The actual active power signal gained by gain factor K_(S1 )can meet the requirement of phase compensation through Order 1 lead and lag elements, thus increasing allowable total setting gain of PSS and improving the ability of low-frequency band oscillation suppression.


Patent
State Grid Corporation of China, Zhejiang Electrical Power Test and Research Institute | Date: 2014-12-24

A method for quickly carrying out effective automatic interlocking logic detection based on a GOOSE communication mechanism, comprising: introducing an automatic system device model and configuration satisfying the IEC61850 standard, and simulating a GOOSE communication behavior in which an intelligent electronic device acts as a quick packet transmitter and receiver, so as to realize the closed-loop detection function by independent publishing and feedback monitoring GOOSE information.


Patent
Zhejiang Electrical Power Test, Research Institute and State Grid Corporation of China | Date: 2013-10-14

The present application discloses a method for optimized design of an independent micro-grid system, the independent micro-grid system comprising diesel generators, wind powered generators, a photovoltaic array, and an energy storage battery, the optimization method referring specifically to a multi-objective optimization design model based on the independent micro-grid system. In terms of the optimization planning design model, the method takes into account a combined start-up mode for a plurality of diesel generators and a control strategy for coordinating between the energy storage battery and the diesel generators, such that the usage rate of renewable energy in the independent micro-grid is higher, and operations more economical and environmentally friendly. Regarding the stability of the system optimization planning design model, the method takes into account the reserve capacity needed for stability of the independent micro-grid. In terms of the solving algorithm of the optimization planning design model, the method employs a multi-objective genetic algorithm based on NSGA-II to implement multi-objective problem-solving, thereby allowing a multi-objective optimization of the three major objectives of economy, reliability, and environmental friendliness of an independent micro-grid system.


Patent
State Grid Corporation of China, Zhejiang Electrical Power Test and Research Institute | Date: 2015-05-14

A method for obtaining a relation between a winding state and a leakage reactance parameter of a transformer by using simulation software is provided. The method includes: establishing a simulation transformer based on a size of a physical transformer; setting parameters of the simulation transformer, setting a winding of the simulation transformer in a predetermined winding state; obtaining a predetermined number of values of a leakage reactance parameter of the simulation transformer in the winding state; and performing statistics on all the values to obtain a value range of the leakage reactance parameter in a case that the winding is in the winding state. The value range is used as a value range of a leakage reactance parameter of the physical transformer in a case that a winding of the physical transformer is in the winding state.

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