A Hybrid Reliability Evaluation Method for Meshed VSC-HVDC Grids

With the large amount of distributed generation in use, the structure of the distribution system is increasingly complex. Therefore, it is necessary to establish a method to improve load reliability. Based on the reliability model of distributed generation, this paper investigates the time sequential simulation of a wind/solar/storage combined power supply system under off-grid operation. After classifying the load by power supply region, the load weight coefficient is established, which modifies the reliability index of the load point and system. The modified expected energy not supplied (EENS) is adopted as the objective function, and the particle swarm optimization algorithm is used to solving the optimal energy scheduling for improving the load reliability. Finally, the load reliability is calculated with a hybrid method. Using the IEEE-RBTS Bus 6 system as an example, the correctness and validity of the proposed method are verified as an effective way to improve load reliability.

Section: Load Reliability Evaluation Based On the Hybrid Methodsmentioning

confidence: 99%

Section: Reliability Index Of a Different Energy Scheduling Schemementioning

confidence: 99%

A Method for Load Classification and Energy Scheduling Optimization to Improve Load Reliability

Ren

Yang

et al. 2018

“…Grid-connected voltage source converters (VSC) have been applied widely in renewable power generation systems and electric power transmission, due to the advantages of the controllable power factor and sinusoidal current output [1][2][3]. The control strategies for VSC connected to the ideal grid have been researched extensively [2][3][4][5]. However, according to the requirements of the grid standards in China [6], the harmonic distortions in voltage for a mid-low voltage supply network is allowed to be 5%, in which odd harmonics cannot be higher than 4%.…”

Section: Introductionmentioning

confidence: 99%

Improved Operation Strategy with Alternative Control Targets for Voltage Source Converter under Harmonically Distorted Grid Considering Inter-Harmonics

Pang

Nian

2019

This paper proposed an improved control method for grid-connected voltage source converter (VSC), when the grid voltage consisted of the integer harmonics and inter-harmonics. Control object of the proposed control can be alternated to achieve the sinusoidal current or smooth output power, which enhances the operation adaption of VSC under the harmonically distorted grid. On the basis of a PI regulator in the fundamental current control loop, the novel control strategy was proposed with a supplementary controller which consisted of a prepositive high-pass filter and a modified proportional-derivative controller. In the proposed control, the inter-harmonics could be suppressed without detecting frequency, while the traditional resonator was effective in the premise of knowing the harmonics frequency. Also, the influence of control gain on the steady performance and the stability of VSC was analyzed, and the influences on the fundamental control caused by the proposed controller were also analyzed to verify the practicability of the proposed control strategy. Finally, the effectiveness of the proposed strategy was verified by the experiments.

“…Voltage source converter high voltage direct current (VSC-HVDC) technology is playing an ever-increasing role in power transmission systems all over the world [1][2][3]. The VSC-HVDC system can provide flexible power control, and facilitate power grid interconnection and the integration of distributed generations.…”

Section: Introductionmentioning

confidence: 99%

Integral Plus Resonant Sliding Mode Direct Power Control for VSC-HVDC Systems under Unbalanced Grid Voltage Conditions

Yang

Zhang

et al. 2017

An integral plus resonant sliding mode direct power control (IRSMC DPC) strategy for voltage source converter high voltage direct current (VSC-HVDC) systems under unbalanced grid voltage conditions is proposed in this paper. Through detailed instantaneous power flow analysis, a generalized power compensation method, by which the ratio between the amplitude of active and reactive power ripples can be controlled continuously, is obtained. This enables the system to provide flexible power control, so that the desired performance of the system on both the ac and dc sides can be attained under different operating conditions. When the grid voltage is unbalanced, one or both of the active and reactive power terms contain ripples, oscillating at twice the grid frequency, to obtain non-distorted ac current. A power controller consisting of the proportional, integral and resonant control laws is designed using the sliding mode control approach, to achieve accurate power control objective. Simulation studies on a two-terminal VSC-HVDC system using MATLAB/SIMULINK (R2013b, Mathworks, Natick, MA, USA) are conducted to verify the effectiveness of the IRSMC DPC strategy. The results show that this strategy ensures satisfactory performance of the system over a wide range of operating conditions.