Power hardware in the loop and ancillary service for voltage regulation in low voltage grid

Power production via traditional generators play a major role to meet demand, however, the trend is shifting towards utilization of distributed renewable sources. Distributed Energy Resources (DER) becomes a means to support loads locally. As DERs are typically intermittent sources, there are challenges associated with the high level of penetration of these resources that are of concern to grid operators. There are also opportunities associated with this technology as the inverters connecting the DERs could support voltage regulation by performing reactive power compensation in the grid.The concept of utilizing droop controlled DERs as reactive power resources is explored in this paper. As the active power production fluctuates with solar insolation, the spare capacity of the inverters could be employed to provide effective reactive power compensation to support the grid.In this paper, Power Hardware in the Loop (PHIL) simulation was employed where a single-phase PV inverter hardware is operated in parallel with three other real-time simulated inverters to deliver ancillary services. The results have shown that the switching steps of the On-Load Tap changer transformer (OLTC) were reduced, thus improving overall system performance

A reactive power-voltage control strategy of an AC microgrid based on adaptive virtual impedance

As an effective carrier of distributed generation, a microgrid is an effective way to ensure that distributed power can be reasonably utilized. However, due to the property of line impedance and other factors in a microgrid, reactive power supplied by distributed generation units cannot be shared rationally. To efficiently improve reactive power sharing, this paper proposes a reactive power-voltage control strategy based on adaptive virtual impedance. This method changes the voltage reference value by adding an adaptive term based on the traditional virtual impedance. Meanwhile, a voltage recovery mechanism was used to compensate the decline of distributed generation (DG) output voltage in the process. MATLAB/Simulink simulations and experimental results show that the proposed controller can effectively improve the steady state performance of the active and reactive power sharing. Finally, the feasibility and effectiveness of the proposed control strategy were verified

Improvement of Frequency Regulation in VSG-Based AC Microgrid via Adaptive Virtual Inertia

A virtual synchronous generator (VSG) control based on adaptive virtual inertia is proposed to improve dynamic frequency regulation of microgrid. When the system frequency deviates from the nominal steady-state value, the adaptive inertia control can exhibit a large inertia to slow the dynamic process and, thus, improve frequency nadir. And when the system frequency starts to return, a small inertia is shaped to accelerate system dynamics with a quick transient process. As a result, this flexible inertia property combines the merits of large inertia and small inertia, which contributes to the improvement of dynamic frequency response. The stability of the proposed algorithm is proved by Lyapunov stability theory, and the guidelines on the key control parameters are provided. Finally, both hardware-in-the-loop and experimental results demonstrate the effectiveness of the proposed control algorithm