High-Quality Power Generation Through Distributed Control of a Power Park Microgrid

Abstract

Abstract-Inverters are a necessary interface for several forms of distributed generation (DG) and where they form a microgrid they have the potential to offer high power quality. The challenge is to coordinate the actions of a group of inverters so that they offer the level of power quality known to be possible from fast local control of a single inverter. The case examined here is a power park of several inverter-based DG in relatively close proximity. A basic requirement is that the inverters regulate the grid voltage and share the real and reactive power demands according to their ratings. In small girds with high proportions of nonlinear and unbalanced loads it is also important to actively control the waveform quality in terms of harmonics, transient disturbances, and balance. Further, it is important that these duties are shared equally between the units rather than having one master unit taking the lead in the voltage control function. A constraint faced in designing a sharing system is the limited bandwidth of signal communication even over distances of a few meters. A control method is proposed that separates the control tasks in the frequency domain. Power sharing and voltage regulation are controlled centrally and commands are distributed through a low-bandwidth communication link. Waveform quality functions are controlled in high bandwidth controllers distributed to each local inverter. Experimental tests on a grid of three 10-kVA inverters are used to show that the method fully exploits the inherent fast response of the inverters while also ensuring voltage balance even with extreme load imbalance. It is shown that circulating currents are avoided during steady state and transients.

A Review of Power Electronics Based Microgrids

“…On the other hand, in the islanded microgrids, switching of loads can also cause high voltage transients, which consequently require all DER units to support this disturbance [56]. In addition, the appearance of negativesequence component in the system voltage leads to the second harmonic oscillations in the system of DER units.…”

“…The most obvious drawback is that the limited bandwidth of signal communication leads the master unit to take up most of nonlinear loads in the microgrid. Hence, the distorted powers are often compensated locally by DER unit itself without using communication links in the improved active load sharing method [56].…”

Elgamal Elliptic Curve Based Secure Communication Architecture for Microgrids

“…and also helps to integrate wind and solar energy generation systems into the main grid [1][2][3]. Key components of a microgrid include (1) connection from and to the main power grid (2) electrical loads and (3) a mean of backup energy source (e.g., renewable resources, etc.).…”

A Control Stratergy for the Improvement of Power Quality in Microgrid.

“…Several intrinsic problems led to its limited transient response, as the system dynamics depends on the power calculation characteristics. Another new adaptive neuro-fuzzy control method is utilized to achieve smooth bidirectional power flow and nonlinear unbalanced load compensation simultaneously [8]. In this case, the traditional PI controller might be insufficient because of the instantaneous changes in the dynamics of the system.…”

“…In reference [8], a current control method for inverters based on the sigma delta modulation algorithm called the sigma delta-based current controlled voltage source inverter interfaced with DG generators was studied. A particle swarm optimization method was used for the optimum tuning of the controllers as a result of the existent number of PI controllers.…”