DC microgrid has a promising future for its strong power supply capacity, good controllability, and high efficiency. The quality of the is one core issues planning, design, operation, control. However, due to zero-frequency characteristic system, presents new characteristics. This paper analyzes differences between AC constructs index system. harmonic, voltage fluctuation flicker, sag, unbalances, deviations are defined according existing literature standards. Moreover, correlation harmonics...

In this paper, a method is proposed to mitigate unbalanced voltage and reduce power losses due neutral line current in bipolar direct (DC) distribution network by introducing DC electric spring (DC-ES). The coupling relationship between positive negative pole voltages are investigated given the resistance of network. matrixes DC-ES output deduced. And demonstrate that control system composed double inputs outputs voltages. small-signal model with DC-ESs derived further. Subsequently,...

In a bipolar DC distribution network, the unbalanced load resistance, line resistance and renewable energy source will cause an current for each node of neutral lead to its voltage. This is unique power quality problem networks, which increase loss in network overcurrent protection serious cases. A voltage balancer can be adopted suppress current. However, existing literature does not consider consistent application multiple balancers multi-node network. paper creatively proposes consensus...

The precise identification of fault locations in multi-terminal DC (MTDC) transmission systems using traveling waves (TW) is imperative for ensuring the secure and stable operation power systems. presence wave impedance discontinuity overhead-cable hybrid lines (OCHTL) causes significant changes TW velocity. Traditional TW-based location methods struggle to adapt these changes. This paper introduces an innovative approach tailored OCHTL, with primary aim enhancing fault-ranging accuracy....

The unbalanced DC loads between the positive and negative poles of bipolar distribution network leads to increase current (voltage) power losses. This affects efficiency transmission also influences quality load. In this article, an load switching strategy based on automatic commutation switch (ACS) genetic algorithm (GA) is proposed. proposed method can automatically adjust supply polarity (PSP) according currents in network. article introduces configuration topology ACS a Furthermore, its...

Addressing the issue of reduced system inertia and significantly increased risk frequency deviation due to high penetration renewable energy sources, this paper proposes a power disturbance trajectory prediction method based on light gradient boosting machine (LightGBM) Spearman provide data support for advanced stability judgment initiation control measures. Firstly, optimal cluster is determined by combining K-means clustering algorithm with elbow eliminate redundant electrical quantities....

The voltage source converter-based multi-terminal DC transmission (VSC-MTDC) system can use additional frequency control to respond the change of faulty AC system. However, coefficient traditional is mostly fixed, and flexibility insufficient, so it cannot be adjusted adaptively according Therefore, a strategy VSC-MTDC based on fuzzy logic proposed. Based slope controller, this introduces an controller control, takes deviation rate as input, dynamically adjusts quantity through link realize...

The use of bipolar direct current (dc) distribution systems introduces the possibility unbalanced voltage (current). This situation increases deviations and power losses at each node owing to presence a neutral line current. article proposes method that mitigates caused by constant loads (CPLs) dc electric springs (DC-ESs). A linearized model is used in small-signal analysis CPLs. On this basis, coupling relationship between positive negative pole voltages analyzed. After DC-ESs are...

Four-mode modulation (FMM) method is the most advanced for four-switch buck–boost converter among existing control strategies. But its efficiency still not optimal. In this article, all FMM methods are analyzed, and minimum inductor current root mean square value of each obtained via generalized Lagrange multiplier method. Under circumstance, optimal selected to form a that improves operating over whole range. Experimental results comparison with state-of-the-art demonstrate effectiveness...

When systems experience a severe fault, splitting, as the final line of defense to ensure stability power system, holds immense significance. The precise selection splitting sections has become current focal point research. Addressing challenges large search space and unclear sections, this paper introduces grid structure optimization algorithm based on electrical coupling degree. Firstly, employing theory slow coherency, generalized characteristic analysis system is conducted, leading an...

This study develops a high-speed protection method for modular multilevel converter (MMC)-based DC grids. The utilizes the single-end derivative of common-mode (CM) and differential-mode (DM) currents to construct phase-plane that divides different fault types into regions. When starts, first sampling point enters regions has largest value. five sampled data satisfy corresponding conditions, signal will be sent. scheme ensures rapidity protection. CM DM circuits MMC, transmission line,...

The difference between positive and negative pole dc loads in a bipolar distribution network causes unbalanced current the neutral line. This increases power losses leads to voltage each node. An automatic commutation switch (ACS)-based method is developed this study suppress voltage. Expressions of single node multiple nodes are derived. equations indicate that poles can be reduced by adjusting supply polarity (PSP) load. PSP load corresponding switching command determined comparing...

Large-scale wind farms are usually integrated into transmission systems through interconnecting transformers. Applying traditional, steady-state, fundamental frequency-based differential protection (DP) strategies in these transformers creates challenges. First, the fault current of might be dominated by non-fundamental frequency components caused activation their own during low-voltage ride-through (LVRT). Second, contains low-order that may affect second-harmonic restraint algorithm...

Flexible DC grids with dedicated metallic return (DMR) encounter two major challenges when reclosing hybrid circuit breakers (DCCBs): (1) identifying permanent and nonpermanent faults to determine whether DCCBs should be reclosed; (2) pole-to-ground (P-GND) pole-to-DMR (P-DMR) all lines isolated a fault occurs. Under P-DMR fault, transmission instead of maintaining half the power transmission. In this study, equivalent circuits analytical expressions currents under P-GND are deduced. On...