.gif)
Adaptive Hybrid Synchronization Control Scheme of Grid-Forming Inverter to Improve Transient Stability by Chan-Kyu Shin
A THESIS
Submitted to the faculty of
INHA UNIVERSITY
in partial fulfillment of the requirements
for the degree of
MASTER COURSE
Department of Electrical and Computer Engineering
Abstract
The increasing number of inverter resources in power systems has
changed the dynamics of the system, leading to new types of stability
problems that have not been observed before. In 2020, the IEEE Power
& Energy Society (PES) revised the stability classification and introduced
new stability criteria, which has led to an increase in stability analysis
studies for grid-connected inverter systems.
Grid-connected inverters are classified into grid-following inverters (GFL
inverters), which utilize voltage-based synchronization, and grid-forming
inverters (GFM inverters), which utilize power-based synchronization
control, according to the synchronization control method. Recently, inverter
models with Hybrid Synchronization Control (HSC) technique that combines
the advantages of both synchronization controls have been studied, and the
need to develop control techniques that consider the impact of current
limiting algorithms applied for protection of inverter switching elements on
inverter control performance has been increasingly emphasized.
This paper proposes an adaptive hybrid synchronous control scheme to
improve the transient stability of GFM inverters under various grid
conditions. The proposed technique considers the voltage at the point of
common coupling (PCC) and the maximum output current of the inverter
to adjust the ratio between the Power Synchronization Control (PSC) control
and the Phase Locked Loop (PLL) control in the active power control loop
and the power references to improve the transient response characteristics.
First, the effect of current limitation on the output power of a GFM inverter
is formally defined, and the need for inverter output control considering
current limitation is verified using the Equal Area Criterion(EAC). Based
on this, we design a GFM inverter adaptive control structure that utilize the
PCC voltage to improve the system damping characteristics and mitigate
the instability problem caused by the current limit. The control system of
the inverter has a cascade control structure. The upper controller, the active
power control loop, is composed of swing equation based PSC and a
proportional PLL, respectively, while the reactive power control loop is
composed of an integral controller and a droop controller. The voltage and
current control loops, which are the lower-level controllers, control the
inverter output power using the reference values obtained from the output
of the upper-level controllers.
The performance of the proposed adaptive synchronization control
technique is verified by transient stability analysis using Phase Portrait
(PP), and time-domain simulation demonstrates that the inverter can
operate stably under various voltage disturbance conditions.
Nenhum comentário:
Postar um comentário