Improved Voltage Control Strategy Research Articles

Analysis and Verification of Compound SRFPI-LADRC Strategy for an Off-Grid Single-Phase Inverter

Summary. The linear active disturbance rejection control (LADRC) is mainly applied for tracking a step signal, and it is inadequate to realize satisfactory performance in the control of a single-phase inverter whose reference signal is sinusoidal. In this paper, an improved voltage control strategy based on compound synchronous reference frame proportional-integral (SRFPI) control and LADRC is proposed. The SRFPI and LADRC remain relatively independent without complicating the control parameter design. Detailed theoretical analyses on the compound strategy and its performance are presented, indicating that it inherits the advantages of the two controllers. Moreover, contrast experiments are carried out to verify the feasibility and superiority of the proposed control strategy. The results show that the system achieves a small steady-state error, voltage tracking error, fast transient response, and low total harmonic distortion (THD) when feeding a highly nonlinear load.

Analysis of Voltage Control Strategies for Wind Farms

PCC voltage control is an important key to deal with upcoming challenges of large-scale wind power integration into electric grid. In this paper, based on the derived transfer functions of the plant and controllers, the dynamic performance of three voltage control strategies (centralized, decentralized, and distributed control) is evaluated in terms of robustness to variation of short-circuit ratio (SCR), disturbance rejection (DR), and impact of communication delay. After showing shortcomings of each strategy, an improved voltage control strategy with lower sensitivity to SCR variation and higher capability on grid voltage DR as well as on reactive current dispatch is proposed. The theoretical analysis is validated by simulation results in MATLAB. Finally, a small wind farm is modeled and simulated in RTDS to demonstrate the possible control interaction and reactive current sharing performance of the studied control schemes.

Improved Voltage Control Strategy for Multi-terminal Flexible DC System

This paper presents an improved Voltage Droop control strategy, which updates the reference of DC link voltage by adding the difference between reference and actual voltage, which also adopts a dynamic P-V droop coefficient to improve the DC voltage level. By applying this method, we can eliminate the steady-state deviation of DC link voltage caused by ignoring the power loss in converter. In this paper, in order to demonstrate the reduction of deviation of DC link voltage, an improved control strategy is implemented for a three-terminal flexible DC power system modelled in PSCAD/EMTDC.

Improved voltage control strategy for photovoltaic grid-connected system based on double-layer coordination control

An improved automatic voltage coordination control strategy (AVCCS) based on automatic voltage control (AVC) and battery energy storage control (BESC) is proposed for photovoltaic grid-connected system (PVGS) to mitigate the voltage fluctuations caused by environmental disturbances. Only AVC is used when small environmental disturbances happen, while BESC is incorporated with AVC to restrain the voltage fluctuations when large disturbances happen. An adjustable parameter determining the allowed amplitudes of voltage fluctuations is introduced to realize the above switching process. A benchmark low voltage distribution system including PVGS is established by using the commercial software DIg SILENT. Simulation results show that the voltage under AVCCS satisfies the IEEE Standard 1547, and the installed battery capacity is also reduced. Meanwhile, the battery’s service life is extended by avoiding frequent charges/discharges in the control process.