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The resonant stability problems of LCL filter have become big challenges for grid-connected inverter in weak grid. This paper takes the effect of non-minimum phase time delay on the ratio between resonance frequency and sampling frequency into account and use it to design the LCL filter. Both LCL resonance frequency and inverter-side inductor and filter capacitor related L1C resonance frequency are...
An increased deployment of distributed generation in recent years has contributed to creation of meshed power networks usually seen as a way to improve power flow management capability. Also, power electronics converters have been commonly used to interface distributed resources to the grid, yet their impact on the network stability has not been sufficiently explored. In this paper the stability of...
This paper investigates the problem of accurate active power sharing in virtual flux droop where flux angle droop control is used for DG controllers instead of traditional frequency droop control. Firstly, the virtual flux droop control method is introduced. Then, the reasons for inaccurate active power sharing in flux angle droop are analysed. Further, to solve this problem, an active power compensation...
The significant mechanical inertia of the rotor in a synchronous generator is crucial for facilitating the cooperative grid forming capability of multiple such generators on the transmission and distribution network. This paper demonstrates that the DC link capacitance in a PV inverter is the analogous form of inertia for such a system, albeit having much smaller magnitude. Furthermore it proposes...
This paper presents a new approach that provides scaling the LCL-filter inductances based on the harmonic analysis of the filter output current. The approach considers the filter design together with the inverter control, both together, improving the system stability and the dynamic response. The model and general guidelines for selecting the filter parameters, taking into account the variation of...
Weak grid is commonly seen as a voltage source which contains the gird impedance and background harmonics. The grid current closed-loop control and the grid voltage feed forward control are coupled with each other because of the grid impedance. The proportion feed forward control strategy introduces a positive feedback loop, which affects the grid current quality and the system stability. This paper...
Today a well-known concept of the use of a synchronous generator with permanent magnet excitation in the power generating system with variable frequency is based on the implementation of voltage control due to the high reactance of the generator. This paper describes an analytical method of calculating the parameters of the generator and voltage quality in the power supply system with variable frequency,...
Large-scale integration of distributed generations (DGs) may degrade the stability of the power distribution system. This paper proposes a control method to improve the system stability of grid-connected inverter-based distributed generation (DG) systems. The proposed method is to add a stabilizer inside the inverter interface controller of a DG unit to supply auxiliary current reference signal for...
As an important part of the distributed power generation system, grid-connected inverter has been widely used. However, as a time-varying nonlinear system, the grid-connected inverter has complex dynamic behavior, which can cause serious stability problem. As a consequence, more and more researches have focused on this issue, most of which are limited to the stability problem caused by the variations...
This paper introduces a state-space controller for grid current control which has been developed to optimize the system behaviour of grid connected inverters during voltage dips and short circuits. The performed tests illustrate that in comparison to standard PID-controllers a considerable improvement of the system performance could be realized.
As the traditional resources have become rare, photovoltaic generation is developing quickly. The grid-connected issue is one of the most importance problem in this field. The voltage source inverter usually uses LC or LCL as the filter. LCL filter, which can reduce the required filtered inductance and save the cost, is adopted to connect the grid in this paper. However, reasonable design of LCL filter...
This paper is concerned with the design and simulation of a pulse width modulation (PWM) rectifier for three-phase Permanent Magnetic motor drive. Based on the mathematical model of PWM rectifier, the dual-close-loop engineering design with decoupled feed-forward control is applied in the 3-phase voltage source rectifier. The objective to be reached is to realize unity power factor at the input ac...
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