Adaptive Virtual Impedance Droop Control Based on Consensus Control of Reactive Current

Abstract

It is difficult to achieve accurate distribution of reactive power based on conventional droop control due to the line impedance mismatch in an islanded microgrid. An adaptive virtual impendence method based on consensus control of reactive current is proposed in this paper. A distributed control structure without the central controller has been established. In this structure, each distributed generation unit (DG) is an independent agent, one-way communication is used between the adjacent DGs, and the reactive power sharing is equivalent to a problem of reactive power current consensus. It has been proven that the system is asymptotically stable under the proposed control strategy. When the adjacent DG's reactive power is not proportionally distributed, the current weight error term will generate a virtual impedance correction term through the proportional-integral controller based on the reactive current consensus control strategy, thus introducing adaptive virtual impedance to eliminate mismatches in output impedance between DGs. Reactive power auto-proportional distribution can be achieved without knowing the line impedance. At the same time, the power control loop is simplified and the virtual impedance compensation angle is employed to compensate the decreased reference voltage magnitude and varied phase angle due to the introduction of the virtual impedance, so the stability of the system can be improved. Finally, the correctness and effectiveness of the proposed strategy are verified by modeling analysis and microgrid simulations.

A Load-Balance System Design of Microgrid Cluster Based on Hierarchical Petri Nets

“…The validated model becomes an alternative control proposal for load balancing in the legacy LV grid where the implementation of microgrids and distributed sources of power generation is not currently implemented. Thus, it can act as an alternative control resource in synchronization with the current injection of microgrids, the integrated coordination of control and the integrated coordination of multimicrogrids, as discussed in Section 1 and the general architecture of urban microgrids, as also discussed in Section 2.1 and according to the bibliographic review [21,31,32]. Where it would constitute a distributed control system connected with the CU, the LV transformer, the MGCC system, and the supervision center of the whole electrical system, in order to guarantee the efficient acquisition of consumption data, the load-balancing application and the switching selection according to the load consumption matrix of each single-phase consumer unit.…”

“…Nevertheless, in the legacy LV system [15] the phase-load imbalance is a drawback, especially because domestic loads generated by single-phase consumers affect grid phase stability, and the energy quality supplied [16,17]. Thus, some methods of solving this problem are highlighted in the the electrical current injection from distributed generation microgrids [18][19][20], the coordinated load balance [16,21], the integrated multimicrogrid control [12,[22][23][24] and the load phase balance [25][26][27].…”

Control Method of Parallel Inverters with Self-Synchronizing Characteristics in Distributed Microgrid

“…Therefore, power decoupling needs to be achieved through control methods, such as virtual impedance theory and its improved methods [17,18], the virtual power decoupling method [19] and the feedforward decoupling method [20,21]. (2) Multi-parallel inverters power sharing performance: Droop control can only ensure a reasonable sharing of the active power between parallel inverters, while the reactive power sharing accuracy is affected by the voltage drop of the connecting line, so the reactive power control strategy needs to be improved [17,22,23]. In most of the literature regarding decoupling strategy, the inverter side power decoupling effects of the connecting lines between micro-source and AC bus are studied.…”

Adaptive Fuzzy Droop Control for Optimized Power Sharing in an Islanded Microgrid

“…Moreover, the droop control has its own stability drawbacks such as a dilemma between accurate power sharing and voltage/frequency deviation, a high dependency on the inverter output impedance, and a slow transient response and so on [12]. To overcome these issues, [13] considers different line impedance, [14][15][16] proposes an adjustable virtual output impedance, [17] adds a frequency restoration loop to the conventional droop control, [18] applies fuzzy logic controller to improve transient response and [19] proposes a transient droop gains in order to increase robust stability. Besides the direct improvement to the traditional droop control, the secondary control is also considered to regulate frequency/voltage deviation.…”