The grid-forming and grid-following controls are adopted in three-phase voltage source converters according to different grid conditions. However, the basic operation principle of two kinds control is will lead instability grid-connected system through various paths. In this article, energy function model controlled established compared detail. influence parameters studied, large-signal stability boundaries derived a general method. Moreover, converter, converter lose by exhibiting varying...

Three-phase voltage source converters (VSCs) are commonly used as power flow interface in ac/dc hybrid systems. The ac grid suffers from unpredictable short-circuit faults and fluctuations, causing undesirable dips. dips may last for a short time or long duration, vary the working conditions of VSCs. Due to their nonlinear characteristics, VSCs enter abnormal operating mode response In this paper, transient three-phase under practical is studied catastrophic bifurcation phenomenon identified...

The undesired nonlinear operation of phase-locked loops (PLL) is one the main causes transient instability in grid-connected converters. However, stable operating region PLL, knowing which helpful for protection purposes, hard to find due characteristic process. In this article, PLL control loop relevant converter identified. averaging method applied derive a time-domain expression under disturbance. Based on analytical expression, response and related stability criterion are established,...

Under a short-circuit fault in low-voltage dc microgrid, solid-state circuit breaker (SSCB) assumes the responsibility of quick and effective isolation faulted area, while its own safety reliability depends on overvoltage suppression ability snubber. For SSCB snubber design, however, traditional method suited for converter switch cannot be directly applied, because stresses more current withstanding instead loss reduction. Therefore, this paper strives to build design specialized at bus...

As a flexible and reliable way for distributed energy consumption integration, the converters-dominated microgrid has attracted more attention recently. Owing to low inertia high nonlinearity of power converters, islanded under large-signal disturbances is easily suffer transient stability problems. To support stable operation microgrid, grid-forming converters are extensively investigated applied. In this paper, an improved equal area criterion (IEAC) proposed analysis simple equipped with...

Large disturbance scenarios, such as pulse power load operation and switching are commonly seen in the of dc microgrids. The mixed potential theory-based large-signal stability (LSS) analysis is a simple practical method for investigating LSS However, this characterized by conservatism, produces conservative criterion results. When they applied to parameter designs microgrids, create excessive control redundancies; when used running status estimations, may cause system be misjudged unstable,...

Due to the lack of flexible interconnection devices, power imbalances between networks cannot be relieved effectively. Meanwhile, increasing penetration distributed generators exacerbates temporal caused by large peak-valley load differences. To improve operational economy lowered spatiotemporal imbalances, this paper proposes a two-stage optimization strategy for active distribution (ADNs) interconnected soft open points (SOPs). The SOPs and energy storage system (ESS) are adopted transfer...

With the increasing penetration of renewable energy generators, stability issues grid-tied converter systems become much more important. However, due to high nonlinearity and varying damping systems, conventional transient analysis methods are not applicable, which may bring conservativeness or misjudgment on assessment. In this paper, with is investigated provide boundary estimation. Firstly, considering frequency mutation phase-locked loop (PLL) caused by various perturbations, a modified...

Although hybrid circuit breaker (HCB) uses a combination of mechanical switch and insulated-gate bipolar transistors (IGBTs) to accommodate HVDC application, it still has large number series-connected IGBTs in its main breaker. Besides, multiterminal system, three or more HCBs appear cluster at one node, which worsens the HCBs' disadvantage volume. To simplify cluster's topology structure control system as well increase compactness, multiport (MPCB) is proposed this paper with procedure...

Under weak grid scenarios, the widely adopted synchronous reference frame phase-locked loop (SRF-PLL) exhibits complex behavior due to possible phase or frequency disturbances. In this brief, nonlinear damping characteristics of PLL is identified. The ratio under various strength explored thoroughly. root cause instability unveiled. It shown that, with low short-circuit (SCR) very grid, will drop sharply nonlinearity detector. A practical parameter design method developed accordingly avoid...

In this letter, a cascading synchronization instability phenomenon is reported in multi-voltage-source-converter (VSC) grid. By adopting the equal area criterion, it revealed that during fault transient, there static interaction increases equivalent mechanical power for original stable-operating VSC. Due to fast angle swing of unstable VSC, nonnegligible dynamic interaction, which may decrease its stability margin. The effect system parameters on studied, and simulation experimental results...

With the rapid development of distributed renewable energy generation and integration, stability issues power converters systems have been widely studied in recent years. Many previous studies focus on transient a single converter connected to weak grid. However, nonlinear dynamics mechanism multiple remain unclear. In this article, unified model paralleled-converters system is established, which reveals interactive damping among To analyze impacts terms stability, dual-iterative equal area...

Microgrid has been rapidly developed for the integration of distributed renewable energy, owing to their superiority flexible operation and high reliability. Without frequency support from main grid, microgrid under islanded operating mode is more likely lose stability in presence large-signal disturbances. However, previous studies mainly focus on weak grid conditions ignore interaction effects between different-type converters. Therefore, this article investigates transient synchronization...

In the grid-following (GFL) voltage source converter (VSC), synchronization process of phase-locked loop (PLL) can be seriously affected by interactions from inner current and other parallel-connected VSCs. this paper, we focus on influences these stability GFL-VSC. Firstly, are classified into static dynamic mechanism how they affect PLL. Then, their influence is estimated based a novel Lyapunov criterion, which derived extended invariance principle. On basis, in terms physical mechanism,...

At home and broad, more wind power is being installed in electricity markets, the influence brought by become important on system stability, especially fluctuation, uncertainty production multi-time scale of wind.In order to forecast ramp events before encountering failure, so that operator can adopt some limited controlling strategy.This paper introduces present status prediction at abroad.And it gives out four kinds definitions events, which are used many scholars, then provides various...

Photovoltaic-battery hybrid power system (PBHPS) is a good candidate for rural electrification in remote areas. In this system, multiple energy sources are combined together to the user loads under various structures. We identify and analyze bifurcation process when enters unstable operation states. Then, small signal stability criterion derived based on reasonable simplification of analysis. Furthermore, according nonlinear dynamics interconnected with closed-loop control, large-signal...

A cascaded H-bridge (CHB) converter-based medium or high-voltage motor drive system, that consists of three single-phase CHB chains, may suffer a severe second-harmonic ripple power issue. Oversizing dc capacitors and using active decoupling control with additional passive components are the two possible ways to address this issue, but is achieved at expense increased system cost complexity. This paper proposes tackle issue without any extra for regenerative CHB-based converters. By...

Lifetime is an important performance factor in the reliable operation of power converters. However, state-of-the-art LC filter design a buck dc-dc converter limited to specifications voltage and current ripples constrains density cost without reliability considerations. This paper proposes method optimize filters from perspective, besides other An enhanced model derived quantify lifetime capacitor considering electrothermal stress on it. Furthermore, influence different aspects such as value...

The high penetration of renewable energy generation (REG) systems influences the dynamics power systems. Accurate transient simulations and dynamic models are indispensable for research on behavior REG A large-scale system consisting numerous grid-connected inverters consumes a large amount computation time, so aggregated model is needed efficient simulation. established by coherent equivalence fits detailed well, thus it widely used in aggregation Presently, key challenge application...

The dc-dc converters are connected in parallel to feed the utility loads many applications like dc microgrid, photovoltaic-battery hybrid power system, etc. Since sources usually a bus through electronics converters, dynamics of whole system is complex and stability issues would be critical. In this brief, large-signal modeling analysis performed such using controlled current represent parallel-connected converters. mixed potential theory-based criterion then generated with simplified model....

An input-independent and output-series modular dc-dc converter with multiple input ports high voltage conversion ratio can apply well to medium-voltage dc interface of distributed photovoltaics (PV). However, PV power mismatch will result in output imbalance the submodules (SMs), which is contrary standardized multimodule design. In this article, a multiport low-loss series LC balancing unit (PBU) proposed address problem. isolated employed as SM, consists full-bridge (FB) circuit on side...

As the crucial interface of renewable energy integration, stable operation power converters under grid faults and external disturbances has become much more important. However, synchronization instability grid-tied inverters been found caused by phase-locked loop (PLL) some critical operating conditions, such as voltage sag, current surge, transmission line faults. Due to strong nonlinearity, transient stability analysis with PLL becomes complicated large-signal perturbations weak...