The problem of regulating voltages within the required limits is complicated by the fact that power system supplies power to a vast number of loads and is fed from many generating units. As loads vary, reactive power requirements of the transmission system vary. Moreover, voltage magnitude is relatively less sensitive to active power compared to reactive power due to high X/R ratio of transmission lines. Therefore, separating voltage control from active power is not only justified but also the common and practical way in power transmission systems. Considering these facts, the fast decoupled power flow jacobian can be used to control voltage magnitudes by reactive power compensation. In this paper, an optimal voltage control is presented to obtain new voltage set-points for PV buses by maximizing the effect of input change on output change using the Fast Decoupled Load Flow (FDLF) jacobian matrix. The proposed algorithm was tested on three IEEE systems: 9 bus, 14 bus and 30 bus systems.
Abstract-Appropriate control of high penetration renewable energies in power systems requires a complete modeling of the system. In this paper, a comprehensive state space modeling of voltage source inverters, networks and loads are studied. We have modeled a secondary voltage control that utilizes the nominal set points of the output voltage as the input for the controller design. A distributed control algorithm only requiring a sparse communication between neighboring distributed generators (DGs) is used. The proposed secondary voltage model is applied on a microgrid with three DGs and two loads to verify the results.
This paper proposes a novel cooperative secondary control strategy for microgrids which is fully distributed. There is a two-layered coordination, which exists between inverter based DGs of both types, i.e. Voltage Source Inverter (VSI) and Current Source Inverter (CSI), also called PQ inverter. In first layer of the proposed two-layered cooperative control strategy, VSIs will take care of the primary average voltage regulation by implementing the average consensus algorithm (ACA); then in the second layer of control, the PQ inverters will improve the voltage quality of the microgrid while maintaining the average voltage of buses at the same desired level. Zone dedication algorithm is utilized in the second layer for voltage quality purposes based on sensitivity analysis. The sensitivity analysis is based on Simplified Jacobian matrix and the result of that is used to define the zone related to each DG in the microgrid. The goal of this zone dedication is to assign loads to the DGs that can compensate their changes with less effort (generating less power) than the others. There are two major contributions in this paper; 1- PQ inverters are effectively involved to increase microgrids capacity for better power management by introducing sensitivity to the PQ inverters set-point. This is defined based on the structure of the microgrid and takes into account the location of load changes. 2- The proposed strategy not only focuses on transient response but also improves the steady state response which smooths the voltage profile of the system while keeping the average voltage at the same desired level. The algorithm has been applied to a 13 bus system with a fully distributed communication in which each VSI inverter only communicates with its immediate neighbors and each PQ inverter is only in touch with associated bordering agents. The conclusive results verify that the proposed control strategy is an effective way to control the microgrid's voltage to have a smoother and stable voltage profile. The analysis also confirms the robustness of the proposed cooperative control in presence of possible time delays.
Centralized secondary voltage control in a power system has been replaced by the distributed controller in the recent literature due to its high dependency on extensive communication messages. Although in the new method each distributed generator only communicate with its neighbors to control the voltage, yet the messages are circulating among the whole system. In this paper, we have utilized distributed controller locally so that it will work as a fully distributed control system. This controller has been justified by being studied within a case study including 6 distributed generators.
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