A Comparison Between GSA and IGSA for Optimal Allocation and Sizing of DG and Impact to Voltage Stability Margin in Electrical Distribution System

Bujal Noor Ropidah,Sulaiman Marizan,Abd Kadir Aida Fazliana,Khatib Tamer,Eltawil Naji 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.6

Optimal placement and sizing of Distributed Generation (DG) are essential for future power planning of distribution networks. The performance of Gravitational Search Algorithm (GSA) and an Improved version of Gravitational Search Algorithm (IGSA) are compared in solving the optimization problem. The multi-objective function optimization includes power loss minimization (P loss ), Minimum bus voltage (Vbus min ), and an average voltage total harmonic distortion (THDv) are considered in this optimization problem and the IEEE 13-bus and IEEE 69-bus radial distribution network were applied on this study. The benefi ts due to the optimal placement and sizing of DG include power loss reduction, minimization of total harmonic distortion, and improvement of bus voltages, especially the weakest bus in the distribution network. The impact of DG installation at the proposed location with the proposed sizing on voltage stability margin also presented. The results show the Voltage Stability Margin (VSM) for both real power (P) and reactive power (Q) at the weakest bus after DG have improvement with present of DG.

The Inter-tie Protection Schemes of the Utility Interactive Dispersed Generation Units for Distribution Automatic Reclosing

Park, Joon-Ho,Kim, Jae-Chul,Moon, Seung-Il The Korean Institute of Electrical Engineers 2002 KIEE International Transactions on Power Engineeri Vol.a2 No.4

Dispersed Generation (DG) units significantly effect the existing distribution protection practices. Therefore, new protection practices of the distribution system interconnected with DG units should be reevaluated and developed. In this paper, a new inter-tie protection scheme of DG units for distribution automatic reclosing is proposed. The impact of DG units on existing radial-sectionaliser coordination is analyzed. And the effects of the distribution reclosing type (radial and passive reclosing) on DG dynamics are analyzed and classified. From the results of the DG dynamic responses by the reclosing type, i.e. radial and passive reclosing, the inter-tie protection schemes of DG are introduced to improve the reliability and availability of utility interactive DG. The proposed schemes are proved and evaluated by a case study using PSCAD/EMTDC simulation.

Control Strategy Design of Grid-Connected and Stand-Alone Single-Phase Inverter for Distributed Generation

Cai, Fenghuang,Lu, Dexiang,Lin, Qiongbin,Wang, Wu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 kVA prototype demonstrate the effectiveness of the proposed control strategy.

A New Islanding Detection Method using Phase-Locked Loop for Inverter-InterfacedDistributed Generators

Il-Yop Chung,Seung-Il Moon 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.2

This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.

A New Islanding Detection Method using Phase-Locked Loop for Inverter-Interfaced Distributed Generators

Chung, Il-Yop,Moon, Seung-Il The Korean Institute of Electrical Engineers 2007 Journal of Electrical Engineering & Technology Vol.2 No.2

This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.

배전계통의 전압조정기 운영방법에 따른 분산형전원 최대 도입 용량 산출

김미영(Miyoung Kim) 대한전기학회 2009 전기학회논문지 Vol.58 No.7

Stable and sustainable power supply means maintaining a certain level of power quality and service while securing energy resource and resolving environmental issues. Distributed generation (DG) has become an essential and indispensable element from environmental and energy security perspectives. It is known that voltage violation is the mostimportant constraint for load variation and the maximum allowable DG. In distribution system, sending voltage from distribution substation is regulated by ULTC (Under Load Tap Changer) designed to maintain a predetermined voltage level. ULTC is controlled by LDC (Line Drop Compensation) method compensating line voltage drop for a varying load, and the sending voltage of ULTC calls for LDC parameters. The consequence is that the feasible LDC parameters considering variation of load and DG output are necessary. In this paper, we design each LDC parameters determining the sending voltage that can satisfy voltage level, decrease ULTC tap movement numbers, or increase DG introduction. Moreover, the maximum installable DG capacity based on each LDC parameters is estimated.

Control Strategy Design of Grid-Connected and Stand-Alone Single-Phase Inverter for Distributed Generation

Fenghuang Cai,Dexiang Lu,Qiongbin Lin,Wu Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 ㎸A prototype demonstrate the effectiveness of the proposed control strategy.

A Novel Three-Phase Four-Wire Grid-Connected Synchronverter that Mimics Synchronous Generators

Qian Tan,Zhipeng Lv,Bei Xu,Wenqian Jiang,Xin Ai,Qingchang Zhong 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Voltage and frequency stability issues occur in existing centralized power system due to the high penetration of renewable energy sources, which decrease grid absorptive capacity of them. The grid-connected inverter that mimics synchronous generator characteristics with inertia characteristic is beneficial to electric power system stability. This paper proposed a novel three-phase four-wire grid-connected inverter with an independent neutral line module that mimics synchronous generators. A mathematical model of the synchronous generator and operation principles of the synchronverter are introduced. The main circuit and control parameters design procedures are also provided in detail. A 10 ㎾ prototype is built and tested for further verification. The primary frequency modulation and primary voltage regulation characteristics of the synchronous generator are emulated and automatically adjusted by the proposed circuit, which helps to supports the grid.

필터 리액턴스 오차에 의한 병렬연계 인버터 기반 슬랙발전기의 최대 용량 분석

이수형 대한전기학회 2022 전기학회논문지 P Vol.71 No.4

The renewable-energy-penetration is rapidly increasing worldwide. This causes an increase in the inverter ratio in the power system. This paper analyzes the effect of filter reactance error on the capacity of a scaled-up slack generator. In the scaled-up slack generator, parallel-connected multiple inverters, except the physical slack inverter, share the power supply to the grid by a predetermined ratio based on their capacities. It is inevitable having an error between real and known values of filter reactance. This makes the multiple inverters operate non-identically, so it reduces the maximum potential capacity of the scaled-up slack generator. The scaled-up slack generator is simulated with parallel-connected eleven inverters, including one physical slack, to get the data for the analysis. The simulation is conducted using a power system computer-aided design/electromagnetic transient including DC (PSCAD/EMTDCTM).

A Distributed Harmonic Power Sharing Strategy for Islanded Microgrids

Tuan V. Hoang,Hong-Hee Lee 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This study presents a distributed-based control method to provide accurate harmonic power sharing for islanded microgrids. The proposed method requires simple communication network through which the DG unit uses local and its neighbors’ information to execute the control algorithm. In the proposed method, a distributed adaptive virtual impedance controller is developed to realize accurate harmonic power sharing for the islanded microgrids regardless of load changes. The proposed method is quite easily implemented in practice because the information such as the line impedances, load powers, and the detailed microgrid configuration is needless. Also, the feasibility and effectiveness of the proposed method are validated via digital simulation.