Optimal allocation of multi-type FACTS devices in power systems based on power flow entropy

The unified power flow controller (UPFC) based on modular multilevel converter (MMC) is the most creative flexible ac transmission system (FACTS) device. In theory, the output voltage of the series MMC in MMC-UPFC can be regulated from 0 to the rated value. However, there would be relatively large harmonics in the output voltage if the voltage modulation ratio is small. In order to analyze the influence of MMC-UPFC on the harmonics of the power grid, the theoretical calculation method and spectra of the output voltage harmonics of MMC are presented. Subsequently, the calculation formulas of the harmonics in the power grid with UPFC are proposed. Based on it, the influence of UPFC on the grid voltage harmonics is evaluated, when MMC-UPFC is operated with different submodular numbers and voltage modular ratios. Eventually, the proposed analysis method is validated using digital simulation. The study results would provide guideline for the design and operation of MMC-UPFC project.

Section: Mmc-upfc Modelmentioning

confidence: 99%

“…Consequently, the output voltage would increase. At every switch cycle, the numbers of SMs which are put into operation in the upper and lower arms can be determined according to (1).…”

Section: Basic Principle Of Nlmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Harmonic influence analysis of unified power flow controller based on modular multilevel converter

Yuan

Kong

et al. 2016

“…Bridge-type fault current limiter (BFCL) that uses a switched transformer-type DC reactor, whilst the load current exceeds a predefined threshold, the secondary side of the transformer can be opened by an insulated gate bipolar transistor [18]. These FACTS type devices have possible capability of being applied for fault current suppression, because they can perform power flow regulation functions under steadystate operation conditions [19], and can also be switched to an emergency control status during serious faults. Thyristor-controlled phase shifting transformer (TCPST) is a special FACTS device with a series and a parallel power transformer, which fulfills fast phase angle adjustment of the voltage across the device to regulate regional power flow [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Application of thyristor controlled phase shifting transformer excitation impedance switching control to suppress short-circuit fault current level

Liu

Hao

Wang

et al. 2018

Short-circuit fault current suppression is a very important issue in modern large-interconnected power networks. Conventional short-circuit current limiters, such as superconducting fault current limiters, have to increase additional equipment investments. Fast power electronics controlled flexible AC transmission system (FACTS) devices have opened a new way for suppressing the fault current levels, while maintaining their normal functionalities for steady-state and transient power system operation and control. Thyristor controlled phase shifting transformer (TCPST) is a beneficial FACTS device in modern power systems, which is capable of regulating regional power flow. The mathematical model for TCPST under different operation modes is firstly investigated in this study. Intuitively, the phase shifting angle control can adjust the equivalent impedance of TCPST, but the effect has been demonstrated to be weak. Therefore, a novel transformer excitation impedance switching (EIS) control method, is proposed for fault current suppressing, according to the impedance characteristics of TCPST. Simulation results on IEEE 14-bus system have shown considerable current limiting characteristic of the EIS control under various fault types. Also, analysis of the timing requirement during fault interruption, overvoltage phenomenon, and ancillary mechanical support issues during EIS control is discussed, so as to implement the proposed EIS control properly for fast fault current suppression.

“…Much work has been done in the field of evaluation methods. In [8][9][10][11][12][13][14], the analytic hierarchy process (AHP) method [8], fuzzy AHP method [9][10][11][12], and entropy method [13,14] were studied. Interval arithmetic (IA) is an efficient tool for handling ''unknown but bounded'' uncertainties.…”

Section: Introductionmentioning

confidence: 99%

Hybrid interval AHP-entropy method for electricity user evaluation in smart electricity utilization

Wang

Cai

et al. 2017

Smart electricity utilization (SEU) is one of the most important components in a smart grid. It is crucial to evaluate efficiency, safety, and demand response capability of electricity users to achieve the smart use of electricity. The analytic hierarchy process (AHP) uses subjective criteria to determine index weights in multi-criteria decisionmaking problems, while the entropy method provides objectivity in determining index weights. Taking into account the uncertainty of expert scoring and user data, a hybrid interval analytic hierarchy process (IAHP) and interval entropy (IE) method is proposed for electricity user evaluation (EUE). Specifically, in the proposed method, electricity users are evaluated in terms of energy efficiency, safety monitoring, and demand response. The weights of EUE indices are calculated under uncertainty. The proposed approach derives subjective weights of EUE indices by the IAHP with expert scoring as input data, and determines objective weights of EUE indices by the IE method with user data as inputs. In order to obtain the optimal combined index weights, the two weights are normalized by a selected weight factor. Numerical case studies illustrate the effectiveness and advantages of the proposed approach, which combines subjective and objective information to derive the optimal combined index weights.