scholarly journals A Novel Control Scheme for Multi-Terminal Low-Frequency AC Electrical Energy Transmission Systems Using Modular Multilevel Matrix Converters and Virtual Synchronous Generator Concept

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 747 ◽  
Author(s):  
Mustafa Al-Tameemi ◽  
Yushi Miura ◽  
Jia Liu ◽  
Hassan Bevrani ◽  
Toshifumi Ise
Keyword(s):  
Negative Impact ◽  
Low Frequency ◽  
Synchronous Generator ◽  
Electrical Energy ◽  
Energy System ◽  
Power Sharing ◽  
Matrix Converters ◽  
R Ratio ◽  
Control Scheme ◽  
Virtual Synchronous Generator

This paper proposes a new control scheme for the low frequency AC transmission (LFAC) system aiming at extending the point-to-point configuration to form a multi-terminal electrical energy network. The multi-terminal low frequency ac (MT-LFAC) system configuration is based on the use of modular multilevel matrix converters (M3Cs) and virtual synchronous generator (VSG) control. The M3C is the next ac/ac converter generation, which is used as an interface with the conventional AC network and the LFAC electrical energy system. Application of VSG control is proposed to enable proper power sharing, to provide synchronization of each terminal, and frequency stabilization, thus, to offer multiterminal forming capability. Two different operation modes are applied in the system to damp the frequency deviation after a dynamic perturbation, which provides additional stabilization feature to the VSG. Frequency restoration mode and commanded mode of power sharing are applied as dynamic states to validate the robustness of the VSG control system. Besides, to solve the negative impact of low X/R ratio in the LFAC electrical energy system, we enhance the VSG control by proposing a virtual-impedance-based solution, which increases the output total impedance on the low frequency side and prevents the coupling between P and Q. The operation of the proposed system is examined by simulation results with a precise model of M3Cs in the PSCAD/ EMTDC software environment (version 4.2.1, Winnipeg, MB, Canada).

scholarly journals The Strategy of Active Grid Frequency Support for Virtual Synchronous Generator

Electronics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1131
Author(s):  
Lingfang Yang ◽  
Junpeng Ma ◽  
Shunliang Wang ◽  
Tianqi Liu ◽  
Zihao Wu ◽  
...  
Keyword(s):  
Characteristic Curve ◽  
Synchronous Generator ◽  
Voltage Source ◽  
Frequency Variation ◽  
Pass Filter ◽  
High Pass Filter ◽  
Active Grid ◽  
Control Scheme ◽  
High Pass ◽  
Virtual Synchronous Generator

Virtual synchronous generator (VSG) control is a promising control approach for voltage source converters as an interface between new energy sources and the power grid. VSG is a grid-friendly control scheme, which can imitate the mechanical inertia of the synchronous generator (SG) and the power droop characteristics. Yet, the droop characteristics imitation of SG induces the frequency variation of the grid-connected inverter along with the droop characteristic curve, which will deteriorate the performance of the grid frequency support during the transient process. In this paper, a control scheme, which shapes the droop curve during the disturbance, is proposed for active grid frequency support. First, a load disturbance extraction strategy with a high-pass filter is applied in the proposed method, and the disturbance component is effectively extracted to compensate for the frequency reference variation in traditional VSG control. The grid frequency is actively supported by shaping the droop curve of active power to the frequency of VSG during the disturbance. Afterward, H∞ and H2 norms are used as the objective function to quantify the control performance of the proposed method, and the particle swarm optimization (PSO) algorithm is applied to optimize the control parameters of the proposed method. With a well-optimized high-pass filter, the active support performance is further improved. Finally, the simulation results and hardware in the loop (HIL) tests verify the effectiveness of the proposed method.

scholarly journals The new power sharing method for threephase parallel inverters with nonlinear loads

2015 ◽  
Vol 18 (1) ◽  
pp. 16-28
Author(s):  
Phuong Minh Le ◽  
Dai Tan Le ◽  
Hoa Thi Xuan Pham
Keyword(s):  
Reactive Power ◽  
Energy System ◽  
Active Power ◽  
Power Sharing ◽  
Control Loop ◽  
Output Impedance ◽  
Nonlinear Loads ◽  
Control Scheme ◽  
Virtual Impedance

This paper presents a new method for controling parallel inverters to share active power and reactive power in the energy system with non-linear loads. In these systems, the virtual output impedance is usually added to the control loop of each inverter to improve the active power and reactive power sharing as well as the quality of the voltage system. Paper also proposes a kind of virtual impedance as a second-order general-integrator (SOGI) scheme. The simulation results in Matlab Simulink show the ability of the proposed controller to good share power P-Q, when connected with unbalanced and nonlinear loads. By using the proposed algorithm allows to reduce the voltage THD to 1.9% and 1.2% for unbalanced and nonlinear loads according by comparision with traditional control scheme.

Adaptive Virtual Impedance-Based Reactive Power Sharing in Virtual Synchronous Generator Controlled Microgrids

2021 ◽  
Vol 57 (1) ◽  
pp. 46-60
Author(s):  
Xiaodong Liang ◽  
Chowdhury Andalib-Bin-Karim ◽  
Weixing Li ◽  
Massimo Mitolo ◽  
Md Nasmus Sakib Khan Shabbir
Keyword(s):  
Reactive Power ◽  
Synchronous Generator ◽  
Power Sharing ◽  
Virtual Impedance ◽  
Virtual Synchronous Generator
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