New adaptive droop control with combined line impedance estimation method for parallel inverters

This paper presents a new load sharing control between paralleled three-phase inverters in an islanded-microgrid based on the line impedance estimation online by the use of the Kalman filter. We can solve the mismatch of power sharing when the line impedance changes due to the temperature and frequency, significant differences of line parameters and requirements of Plug-and-Play mode of inverters connected to the microgrid. Moreover, the paper also presents a new Droop control method working with the line impedance which is different from the Droop traditional algorithm when the line impedance is assumed pure resistance R or pure inductance X. In the paper, the line impedance estimation for parallel inverters uses the least squares method combined with Kalman filter. In addition, secondary control loops are designed to restore the voltage amplitude and frequency of the microgrid by using a combined nominal value SOGI-PLL with generalized integral block and phase lock loop to exactly monitor the voltage magnitude and frequency phase at common PCC. Control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of the power sharing. The simulation results have shown the accuracy of the proposed control method. Therefore, the proposed adaptive droop control method based on line impedance estimation can be an alternative one for load sharing control in islanded microgrids.

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An Improved Droop Control Method for Voltage-Source Inverter Parallel Systems Considering Line Impedance Differences

Energies ◽

10.3390/en12061158 ◽

2019 ◽

Vol 12 (6) ◽

pp. 1158 ◽

Cited By ~ 5

Author(s):

Junjie Ma ◽

Xudong Wang ◽

Jinfeng Liu ◽

Hanying Gao

Keyword(s):

Traditional Method ◽

Reactive Power ◽

Control Method ◽

Average Power ◽

Parallel Systems ◽

Power Sharing ◽

Voltage Source ◽

Droop Control ◽

Voltage Reference ◽

Voltage Compensation

In this paper, the effect of the line impedance difference between various inverters on power sharing with the traditional droop control method is fully analyzed. It reveals that the line impedance difference causes a significant reactive power error. An improved droop control method to eliminate the reactive power errors caused by the line impedance errors is proposed. In the proposed method, a voltage compensation determined by the actual reactive power error between the local inverter and the average one is added into the local voltage reference based on the CAN communication. Even when the communication is interrupted, the controller will operate with the last value of the average power, which still outperforms the traditional method. The effectiveness of the proposed control method is verified by simulation and experimental results, which show the proposed method possesses the better power sharing performance and dynamic response.

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Voltage and Frequency Droop Control in an Autonomous Microgrid

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.236-237.568 ◽

2012 ◽

Vol 236-237 ◽

pp. 568-575

Author(s):

Xiao Ying ◽

Heng Wei Lin ◽

Zhao Yang Yan ◽

Jian Xia Li ◽

Ming Su

Keyword(s):

Control Method ◽

Low Voltage ◽

Impedance Control ◽

Power Sharing ◽

Voltage Source ◽

Droop Control ◽

Parallel Operation ◽

Communication Signals ◽

Control Loops ◽

Control Scheme

In this paper, a method for the parallel operation of inverters in an autonomous microgrid system is adopted. This paper presents the resistive output impedance control scheme that allows multiple voltage source converters (VSCs) to operate in parallel in a VSC fed microgrid. The control loops are taking into account the special nature of a low-voltage microgrid, in which the line impedance is mainly resistive. In contrast with the conventional droop-control method, the proposed controller uses a virtual resistance without communication signals to achieve good power sharing, which is insensitive to line-impedance unbalances.

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Six-phase motor drive supplied by four voltage source inverters with synchronized space-vector PWM

Archives of Electrical Engineering ◽

10.2478/v10171-011-0037-0 ◽

2011 ◽

Vol 60 (4) ◽

pp. 445-458 ◽

Cited By ~ 7

Author(s):

Valentin Oleschuk ◽

Gabriele Grandi

Keyword(s):

Continuous Phase ◽

Power Sharing ◽

Voltage Source ◽

Motor Drive ◽

Phase System ◽

Space Vector Pwm ◽

Space Vector ◽

Voltage Source Inverters ◽

Pulsewidth Modulation ◽

Novel Method

Six-phase motor drive supplied by four voltage source inverters with synchronized space-vector PWMNovel method of space-vector-based pulsewidth modulation (PWM) has been disseminated for synchronous control of four inverters feeding six-phase drive based on asymmetrical induction motor which has two sets of windings spatially shifted by 30 electrical degrees. Basic schemes of synchronized PWM, applied for control of four separate voltage source inverters, allow both continuous phase voltages synchronization in the system and required power sharing between DC-sources. Simulations show a behavior of six-phase system with continuous and discontinuous versions of synchronized PWM.

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