This paper addresses the frequency oscillation problem in a parallel-inverter-based grid-connected system. Angular interactions between inverters and grid exhibit various numbers of complicated characteristics that seriously threaten connected power system's stable operation. proposes unified method analysis to investigate multi-VSG In this method, control model each inverter is equivalent two-terminal network by analogy which can be described as "current source" parallel with reciprocal...

In modern power systems, more sensitive loads appear. The impact of voltage sags on customers cannot be ignored. With the opening electricity markets, it is necessary to modify and supplement reliability indices consider influences sags. this paper, three supplementary are proposed, that is: 1) event time; 2) sag energy; 3) cost events. Furthermore, we try redefine traditional service. These may useful today in future as well. Computer simulation results show do affect indices, which change...

Modular solid-state transformers (SSTs) are suitable for various voltage- and power-level applications. State-of-the-art modular-SST topologies contain a considerable quantity of high-frequency (HFTs) power switches, thereby increasing the costs, difficulty, workloads engineering. To overcome this challenge, new SST topology family, namely, hybrid-frequency cascaded full-bridge (HCFB-SST), is established on basis concept modulation. In comparison with modular-multilevel converter (M <sup...

This paper discusses the sensitivity of programmable logic controllers (PLCs) to voltage sags based on mechanistic analysis and numerous tests. First, sag caused by different values rated working is shown through an power supply discrete input/output modules PLCs. Second, a detailed sag-tolerance experimental scheme proposed, PLC curves that differ from early are established several Experiments conducted with nine typical The input researched first, then, effect key characteristics sag,...

From the last few decades, power demand has significantly increased. However, this growing is not pursued by enhancing generation and transmission capacity. Consequently, plants are running at their maximum capacity to accommodate electric load requirement. Thus, systems minimally protected carry liability of voltage instability, which led many major networks, collapses worldwide. The implementation flexible alternating current system (FACTS) can be a significant choice for stability...

Harmonic impedance estimation and suitable evaluation index selection are the key steps of harmonic contribution evaluation. Most traditional methods only applicable to scenario, where background is stable utility constant. However, this scenario will change in many cases due fluctuation harmonic, system operation mode so on. In order improve accuracy for impedance, a method proposed paper based on similarity measure ordering points identify clustering structure (OPTICS). The total...

This study presents a new approach to the optimal placement of voltage sag monitors considering uncertainties associated with transition resistance. The influence resistance on magnitude sags triggered by symmetrical and unsymmetrical faults is analyzed. Then interval set array for established, basis which, random vector model observability proposed related indices are defined in form conditional probability. established taking available number as constraint condition maximum global index...

The harmonic and resonant characteristics of a multi-inverter grid-connected system can negatively affect power quality when weak grid conditions are present. In this paper, firstly, currents modeled for the inverter, correctness low-frequency harmonics high-frequency verified in closed loop, analyzed parameters varied. Secondly, inverter with feed-forward link analyzed, equivalent model based on triple-decomposition conductance is developed conjunction modal analysis method. Then, resonance...

With the growing power demand, it is vital to expand transfer capacity of transmission lines. But new expansion in our present system confined due financial problems, environmental concerns and health hazards electric magnetic fields. May be its worthwhile option use flexible AC (FACTS) for enhancement system. This paper presents, fruitfulness FACTS devices SSSC TCSC with POD (Power oscillation damper) as additional controller. The major function decrease peaks overshooting clearing time...

This paper analyses the different voltage sag phenomenon of sources and summarizes characteristics sources, including amplitude sag, swell happening at same time changes during three phases balance or not. Most existing source recognition methods their disadvantages application have been analyzed in this paper. Considering that actual power quality monitoring network, many equipments only can provide parts data, so a simple practical method is proposed Only RMS voltages are calculated...

Variable frequency drives (VFDs) are the types of power electronic device commonly used to drive motors with a wide range industrial and practical applications, especially in systems. VFDs sensitive voltage sag, thereby limiting their application. However, difficulty determining detailed sag tolerance characteristics is due various influencing factors, curve obtained from test results updated as mainstream low-voltage change. This paper first perform an in-depth analysis on influence...

The classification and recognition of voltage sag disturbance sources is the foundation mitigating sags. This study analysed characteristics various kinds sags, including sags caused by short-circuit faults, energising transformers starting large induction motors. According to features different sources, an evaluation index set was formed three-phase unbalance factor, duration ratio increments second harmonic. After that, weight each element calculated analytic hierarchy process. A novel...

The demand for power and nonlinear loads is currently increasing, thus a compensator that can efficiently afford compensation with growing or reducing load requirement available transmission network resources are necessary. In this study, we implemented serial FACTS devices, namely, static series synchronous (SSSC) thyristor-controlled (TCSC), to increase the capacity flow in an electric network. We primarily aim capability of system maintain stability after fault transient. Therefore,...

Voltage sags can lead to abnormal operation of electric vehicle charging equipment, but the problem has not been paid more attention now. With gradual increase in application vehicles, it is necessary study impacts voltage on vehicles charging. The simulation models 6-pulse rectifier charger, 12-pulse charger and PWM are established, then different severity types chargers working conditions analyzed degree influence assessed. results show that only related strength sags, also state chargers.

Abstract Faced with the uncertainty of wind and photovoltaic power output load fluctuation caused by increase new energy penetration in active distribution network, demand for operational flexibility construction flexible resources network are gradually increasing. The operation can be realized coordinated planning soft open point integrated storage system (ESOP) resources. Firstly, resource adjustability evaluation margin indicators proposed response model typical Secondly, a two‐stage...

In recent years, with the wide application of power electronic devices and stringent requirement industrial process, voltage sag has caused much attention in many countries. To design effective efficient mitigation management strategies, it is essential to have accurate classification sources. this study, based on analysis massive events grid recorded by online quality monitoring systems several different regions China, a more extensive practical sources given. The sags are divided into...

The three-stage modular solid-state transformer (SST) is a typical SST with non-trivial start-up process. Specifically, special controls must be used to reduce the inrush current in DC/DC stage during process of these SSTs. For based on widely studied single-phase-shift dual active bridge (DAB), no inner-phase-shift control required its normal operations. In this case, using existing increases PWM channel requirements microprocessors and complexity system. To address problem, paper proposes...

The presence of unbalanced voltage sag in grid actual operation gives rise to the output power fluctuation PV inverter, increasing current harmonics and current. calculation reference is a key technology control inverter has important influence on under voltage. Base instantaneous theory, this paper proposed method sag. will not bring harmonic problems, with benefits selectively elimination active fluctuations, reactive fluctuations or negative sequence component. In addition, can be...

With the complication of power system, features resonance interaction behave diversely and pose a threat to effectiveness suppression strategies. Existing strategies are usually designed for specific scenarios which in close correlation with impedance frequency-amplitude distribution, their adaptability under different is hard evaluate. In this paper, domain DC distribution network derived based on node variation before/after suppressed. The criterion takes admittance change as variables,...

In response to China’s goal of “carbon peak and carbon neutrality”, a large number new energy sources are connected the power grid, Chinese cities also accelerating construction systems led by energy. Taking Lishui City as an example, this paper constructs low-carbon emission reduction evaluation system evaluate effectiveness system. This first introduces basic technical characteristics system, in detail key technologies involved Lishui. Then, projects implemented promoting current...

The method of voltage sag source location proposed in this paper is using wavelet-multiresolution to decompose the and current waveforms from monitoring points analyzing change signal energy three-phase instantaneous power during ascertain relative points. caused by line fault, transformer energizing induction motor starting, which are main reason sag, analyzed tested based on an PSCAD simulation model paper. results show that simple reliable can be used determine location.

Harmonic pollution and reactive power compensation are the important quality problems. This paper proposes a combined filter system consisting of parallel operation hybrid active (HAPF) passive filters or capacitors. The HAPF is formed by single tuned LC per phase small-rated three-phase filter, which directly connected in series. characteristics harmonic current detection method using combination load mains analyzed simulated. simulation results show that good performance can be obtained...

Electrified railway has advantages of high speed, heavy load, energy utilization and good economic benefits. However, its access to grid will bring about power quality problems such as harmonics, three-phase imbalance reactive power, which goes against safe operation system. In this paper, issues especially negative-sequence have been discussed possible improvement methods are given. And still in research stage given a introduction aiming at providing reference for the following study. Also,...