DC-Bus Voltage Control Stability Affected by AC-Bus Voltage Control in VSCs Connected to Weak AC Grids

Huang, Yunhui; Yuan, Xiaoming; Hu, Jiabing; Peng, Zhou; Wang, Dong

doi:10.1109/jestpe.2015.2480859

Cited by 163 publications

(99 citation statements)

References 25 publications

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“…For DPGSs, especially megawatt-level systems, it is relatively difficult to measure the PCC voltage to realize grid synchronization, due to the following reasons [24]: (1) the isolation transformer may be geographically far from the grid-connected converter; (2) in medium-or high-voltage applications, the PCC voltage is comparatively high, leading to a situation where the signal conditioning circuit can be quite complex and expensive; and (3) the grid side inductance of the LCL filter might be replaced by the leakage inductance of the isolation transformer to reduce the volume and cost, as in the system described in this paper. Therefore, as applied in [13,24,25], filter capacitor voltage Uc is used as the input voltage of DDSRF-PLL. Moreover, a weak grid can be denoted by the Thevenin equivalent circuit, in which an ideal grid voltage Ug is in series with the grid impedance Lg.…”

Section: Generation and Suppression Mechanism Analysis Of Start-up Inmentioning

confidence: 99%

Improved Capacitor Voltage Feedforward for Three-Phase LCL-Type Grid-Connected Converter to Suppress Start-Up Inrush Current

et al. 2017

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Three-phase active damping LCL-type grid-connected converters are usually used in distributed power generation systems. However, serious inrush current will be aroused when the grid-connected converter starts, especially in rectifier mode, if no effective control method is taken. The point of common coupling (PCC) voltage feedforward is usually used to suppress start-up inrush current. Unfortunately, it will introduce a positive feedback loop related to the grid current and grid impedance under weak grid conditions, and therefore, the grid current will be distorted and the system stability margin will be significantly reduced. To solve the above problems, this paper proposes a simple method based on a d-axis fundamental positive-sequence component of filter capacitor voltage feedforward, without extra sensors and software resources. With the proposed method, it is possible to suppress the start-up inrush current and maintain the grid current quality and system stability under weak grid conditions. The mechanism of start-up inrush current and the effectiveness of the method for inrush current suppression are analyzed in detail. Then, the influences of different feedforward methods on system stability are analyzed under weak grid conditions by the impedance model of grid-connected converter. Finally, experimental results verify the validity of the proposed method.

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Section: Generation and Suppression Mechanism Analysis Of Start-up Inmentioning

confidence: 99%

Improved Capacitor Voltage Feedforward for Three-Phase LCL-Type Grid-Connected Converter to Suppress Start-Up Inrush Current

et al. 2017

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“…Voltage source converter (VSC)-based DC transmission technology can realize active and reactive power controlling [1] and bus voltage supporting [2], which can restrain the fluctuation and randomness of renewable energy in a large range and has potential advantages in renewable energy paralleling in the power grid [3,4]. Meanwhile with a common DC voltage and easy parallel connections, VSC-based DC transmission technology is the most appropriate for multi-terminal DC systems (MTDC) [5].…”

Section: Introductionmentioning

confidence: 99%

Parameter Matching and Optimization of a Hybrid Type DC SFCL Considering the Transient Characteristics of VSC-Based DC Systems

et al. 2019

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Voltage source converter-based (VSC-based) DC systems play an important role in connecting large-scale renewable energy and distributed energy, but they are vulnerable to DC short-circuit fault and lacks mature protection devices and appropriate protection strategies. Therefore, a hybrid type DC superconducting fault current limiter (H-SFCL) is proposed and the current limiting mechanism of the SFCL is analyzed. According to the requirements and strategies for protection, several different effective parameter matching and optimization methods of the H-SFCL are proposed by combining optimization algorithms and two short-circuit transient calculation models of VSC-based DC systems. The optimization methods proposed in this paper are compared and analyzed in terms of convergence, running time, calculation range and stability of optimization results, revealing their respective calculation characteristics. Finally, the effectiveness of parameter matching and optimization methods are well validated by comparison and analysis of simulation. The proposed methods can select a good parameter matching scheme of the H-SFCL to deal with different requirements.Keywords: hybrid type DC SFCL (H-SFCL); DC circuit breaker (DCCB); voltage source converter (VSC); parameter matching; optimization IntroductionVoltage source converter (VSC)-based DC transmission technology can realize active and reactive power controlling [1] and bus voltage supporting [2], which can restrain the fluctuation and randomness of renewable energy in a large range and has potential advantages in renewable energy paralleling in the power grid [3,4]. Meanwhile with a common DC voltage and easy parallel connections, VSC-based DC transmission technology is the most appropriate for multi-terminal DC systems (MTDC) [5]. As a promising research hotspot, several VSC-based demonstration projects have been built including the conventional two or three level converter and modular multi-level converter [6][7][8][9][10]. Nevertheless, the safe, reliable and continuous operation of VSC-based DC system is the premise of exerting its own advantages. Due to the low damping of the DC system, DC short-circuit fault with high current rising rate and fast fault propagation speed is a great threat to the VSC-based DC system [11], which requires the sensitivity of fault identification and the rapidity of protective action. According to [12,13], DC short-circuit current must be interrupted within 5 ms to ensure the safety of VSC components.At present, there are three main methods to deal with DC short-circuit fault, including blocking trigger pulse of converter, opening all AC circuit breakers (ACCBs) on AC sides of the VSC system then opening DC circuit breakers (DCCBs) [13]. DC short-circuit current is difficult to be cleared because

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“…The stability of PV generation connected to a weak grid has been investigated in several works [5][6][7][8][9][10][11][12][13]. The authors in [7,8] proposed an impedance model of a VSC, which was useful for control dynamics and stability studies.…”

Section: Introductionmentioning

confidence: 99%

“…Reference [11] proposed a small-signal model to analyze the stability of DC-link voltage control in the VSC, but it did not consider the impacts of other control loops. References [12,13] pointed out that the instability phenomenon is related to converter control loops such as the phase-locked loop (PLL) controller and the AC terminal controller.…”

Section: Introductionmentioning

confidence: 99%

Small-signal stability analysis of photovoltaic generation connected to weak AC grid

Jia

Yan

Cai

et al. 2018

J. Mod. Power Syst. Clean Energy

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A small-signal model of photovoltaic (PV) generation connected to weak AC grid is established based on a detailed model of the structure and connection of a PV generation system. An eigenvalue analysis is then employed to study the stability of PV generation for different grid strengths and control parameters in a phaselocked loop (PLL) controller in the voltage source converter. The transfer function of the power control loop in the dq rotation frame is developed to reveal the influence mechanism of PLL gains on the small-signal stability of PV generation. The results can be summarized as follows: À oscillation phenomena at a frequency of about 5 Hz may occur when the grid strength is low;`the tuning control parameters of the PLL have a noticeable effect on the damping characteristics of the system, and larger proportional gain can improve the system damping;ẃ ithin a frequency range of 4-5 Hz, the PLL controller has positive feedback on the power loop of PV generation. A virtual inductance control strategy is proposed to improve the operational stability of PV generation. Finally, a simulation model of PV generation connected to weak AC grid is built in PSCAD/EMTDC and the simulation results are used to validate the analysis.

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DC-Bus Voltage Control Stability Affected by AC-Bus Voltage Control in VSCs Connected to Weak AC Grids

Cited by 163 publications

References 25 publications

Improved Capacitor Voltage Feedforward for Three-Phase LCL-Type Grid-Connected Converter to Suppress Start-Up Inrush Current

Improved Capacitor Voltage Feedforward for Three-Phase LCL-Type Grid-Connected Converter to Suppress Start-Up Inrush Current

Parameter Matching and Optimization of a Hybrid Type DC SFCL Considering the Transient Characteristics of VSC-Based DC Systems

Small-signal stability analysis of photovoltaic generation connected to weak AC grid

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