Evaluation and Enhancement of Control Strategies for VSC Stations Under Weak Grid Strengths

Lu, Shaoqi; Xu, Zheng; Jiang, Wei; Xiao, Liang

doi:10.1109/tpwrs.2017.2713703

Cited by 60 publications

(37 citation statements)

References 31 publications

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“…Moreover, when feeding a weak AC system (in which the short circuit ratio (SCR) is below three) [69], the PLL in the conventional VSC-HVDC control block degrades the system's stability and restricts its transmission ability. On the contrary, a VSG-controlled VSC-HVDC can self-synchronize and feed an isolated system [70,71].…”

Section: Converter Stationmentioning

confidence: 99%

Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation

Yan

Zhang

2019

Applied Sciences

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Due to the irreversible energy substitution from fossil fuels to clean energy, the development trend of future power systems is based on renewable energy generation. However, due to the incompatibility of converter-based non-dispatchable renewable energy generation, the stability and reliability of traditional power systems deteriorate as more renewables are introduced. Since conventional power systems are dominated by synchronous machines (SM), it is natural to utilize a virtual synchronous generator (VSG) control strategy that intimates SM characteristics on integrated converters. The VSG algorithm developed in this paper originates from mimicking mathematic models of synchronous machines. Among the different models of implementation, the second-order model is simple, stable, and compatible with the control schemes of current converters in traditional power systems. The VSG control strategy is thoroughly researched and case studied for various converter-interfaced systems that include renewable generation, energy storage, electric vehicles (EV), and other energy demands. VSG-based integration converters can provide grid services such as spinning reserves and inertia emulation to the upper grids of centralized plants, distributed generation networks, and microgrids. Thus, the VSG control strategy has paved a feasible way for an evolutionary transition to a power electronics-based future power grid. By referring to the knowledge of traditional grids, a hierarchical system of operations can be established. Finally, generation and loads can be united in universal compatibility architecture under consolidated synchronous mechanisms.

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Section: Converter Stationmentioning

confidence: 99%

Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation

Yan

Zhang

2019

Applied Sciences

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“…On the basis of (12)- (18), the small-signal model of the MMC AC side model, the inner controller and the PLL could be derived as (19):…”

Section: Small-signal Model Of Phase-locked Loop (Pll)mentioning

confidence: 99%

Minimum Short Circuit Ratio Requirement for MMC-HVDC Systems Based on Small-Signal Stability Analysis

et al. 2019

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This paper determines the minimum short circuit ratio (SCR) requirement for a modular multilevel converter based high-voltage direct current (MMC-HVDC) transmission systems. Firstly, a simplified model of MMC is introduced; the MMC is represented by its AC and DC side equivalent circuit. Next, by linearizing the MMC subsystem and the DC network subsystem, the deduction of the small-signal models of MMC subsystem, the small-signal model of the DC network and MMC-HVDC are carried out successively. Thirdly, the procedure for determining the minimum SCR requirement of MMC-HVDC is described. Finally, case studies are performed on a two-terminal MMC-HVDC system under four typical control schemes. The results show that the restraint factors for the rectifier MMC is predominantly the voltage safety limit constraint, and the restraint factors for the inverter MMC are mainly the phase locked loop (PLL) or the outer reactive power controller. It is suggested that the minimum SCR requirement for the sending and the receiving systems should be 2.0 and 1.5 in the planning stage.

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“…In weak systems, the second approach has shown to be very effective to improve the frequency control in terms of both the rate of change of frequency (RoCoF) and the frequency nadir [10]. The emulation of a synchronous generator entails some challenges, similar to the installation of a new conventional generator in a multi-machine power system [11].…”

Section: Introductionmentioning

confidence: 99%

Improving Small-Signal Stability of Power Systems With Significant Converter-Interfaced Generation

Mauricio

León

2020

IEEE Trans. Power Syst.

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This work presents a hierarchical control strategy to improve the stability of electrical networks with significant converter-interfaced generation (CIG). Due to the lack of inertia of CIG systems, these networks can undergo a high rate of change of frequency, compromising the frequency stability. In a first level control, a local controller based on the virtual synchronous generator (VSG) concept is used to emulate inertia and provide short-term frequency regulation. However, the inclusion of significant VSG units can have a negative impact on the damping of inter-area oscillations. Therefore, in a second level control, a centralized controller is proposed to damp these low-frequency electromechanical oscillations affected by VSGs. Several practical issues such as the identification of a system model for the control design, the compensation of communication delays, and the discrete-time implementation of the controller are particularly analyzed. The introduced supplementary controls allow increasing the penetration of renewable energy sources without jeopardizing the frequency and small-signal stability. Eigenvalue analysis and nonlinear hybrid simulations combining DIgSILENT and Python are performed to validate the proposed control strategy.

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Evaluation and Enhancement of Control Strategies for VSC Stations Under Weak Grid Strengths

Cited by 60 publications

References 31 publications

Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation

Review of VSG Control-Enabled Universal Compatibility Architecture for Future Power Systems with High-Penetration Renewable Generation

Minimum Short Circuit Ratio Requirement for MMC-HVDC Systems Based on Small-Signal Stability Analysis

Improving Small-Signal Stability of Power Systems With Significant Converter-Interfaced Generation

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