Abstract
The increasing penetration of power electronics-based distributed energy resources (DERs) displacing conventional synchronous generators is rapidly changing the dynamics of large-scale power systems. As the result, the electric grid loses inertia, voltage support, and oscillation damping needed to provide ancillary services such as frequency and voltage regulation. This paper presents the multi-mode operation of a Z-source virtual synchronous generator (ZVSG). The converter is a Z-source inverter capable of emulating the virtual inertia to increase its stability margin and track its frequency. The added inertia will protect the system by improving the rate of change of frequency. This converter is also capable of operating under normal and grid fault conditions while providing needed grid ancillary services. In normal operation mode, the ZVSG is working in MPPT mode where the maximum power generated from the PV panels is fed into the grid. During grid faults, a low voltage ride through control method is implemented where the system provides reactive power to reestablish the grid voltage based on the grid codes and requirements. The proposed system operation is successfully validated experimentally in the OPAL-RT real-time simulator.
Highlights
Power electronics-based distributed generators (DGs) have been integrated into the modern power grid to improve its reliability and performance [1]
SIMULATION AND RESULTS The performance of the proposed Z-source virtual synchronous generator (ZVSG) shown in Fig. 1, with control and system parameters given in Table 1 and Table 2 is evaluated in different modes of operation, such as steady state, sudden load changes and occurring voltage sag
This paper studied the multi-mode operation of an impedance-source virtual synchronous generator which is comprised of a single-stage ZSI, equipped with VSG control algorithm and is capable of providing grid ancillary services
Summary
Power electronics-based distributed generators (DGs) have been integrated into the modern power grid to improve its reliability and performance [1]. The generated MPPT power by the PV panels, PMMPT is considered as an active power reference for the VSG control algorithm and the converter works with the unity power factor in this mode. After detecting the low voltage fault, the control method switches from MPPT to LVRT strategy In this state, the reactive power needs to be injected to the grid to reestablish the voltage. The measured voltage of PV array, VPV is compared with the reference voltage at the maximum power point VMPP, a PI controller is used to obtain the shoot-through duty D0 to control the output voltage of the impedance network, Vpn. By implementing the mechanical equation of a conventional SG into the control loops of a PV system, similar behavior can be expected during normal operation and frequency related contingencies due to applying any change (decrease or increase) in the load.
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