• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.217-218
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• 2018

Droop control method is the conventional controller to solve the problem of current sharing error and voltage deviation that can occur in parallel connection of DC-DC converter. This paper compared V-I droop control with I-V droop control, which based on communication and confirmed the results through experiments.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1196-1201
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• 2014

This paper presents an exploration on the effect of wind turbine contribution to the frequency control of individual systems that can be used for efficient power production in India. The research includes the study of Permanent Magnet Synchronous Generator (PMSG), in wind farms. The WTs are tested for inertia and for droop responses with intelligent fuzzy logic controllers (FLC) that choose Double Input Single Output (DISO) strategy that automatically sets gain constants, as well as combined responses for the WTs. Quantitative analyses are presented for the WTs for benefits and drawbacks including appropriate selection parameters. The analysis includes inertia, droop and combined inertia, droop schemes. The reconnaissance also incorporates inertia with FLC, droop with FLC, inertia and droop with FLC schemes for detailed study of WTs, so as to forecast and achieve proper frequency control. Moreover, the analysis provides the best suited method for frequency control in PMSG.

• Journal of Power Electronics
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• v.14 no.1
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• pp.22-29
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• 2014

Current sharing between modules in a converter parallel operation is very important for the reliability of the system. This paper proposes an improved droop method that can effectively improve current sharing accuracy. The proposed method adaptively adjusts the output voltage set-point of each module according to the current set-points. Unlike conventional droop control, modules share a signal line to communicate with each other. Nevertheless, since signals are simple and in digital form, the complexity of the circuitry is much less and noise immunity is much better than those of conventional methods utilizing communication. The operation principle and design procedure of the proposed method are described in detail. Results of the experiment on two boost converters operating in parallel under the specification of a TFT LCD TV panel power supply verify the validity of the proposed scheme.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.51-52
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• 2017

This paper presents an advanced DC droop using both an output current and a grid current. To control parallel-connected converters without communication, the DC droop control is conventionally used. The conventional DC droop control method droops output voltage using an output current. It cannot control the source current causing output voltage errors. This paper proposed the DC droop method using both an output current and a grid current to improve dynamic response of voltage droops. The simulation results with PSIM is provided.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.33-34
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• 2017

This paper presents a linear droop control scheme based on the generation costs of DGs in an autonomous DC microgrid. Unlike the proportional power sharing of the conventional droop control, in the proposed control algorithm, the minimum output voltage range is adjusted and the droop coefficients are regulated according to the generation costs of DGs. As a result, the DGs with lower costs supplies more power in comparison with those with higher costs. Therefore, total generation cost of the system is reduced significantly. The proposed method is simple to implement and it does not require the centralized controller and communication links.

• Journal of Power Electronics
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• v.15 no.2
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• pp.455-468
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• 2015

A microgrid (MG) with integrated renewable energy resources can benefit both utility companies and customers. As a result, they are attracting a great deal of attention. The control of a MG is very important for the stable operation of a MG. The droop-control method is popular since it avoids circulating currents among the converters without using any critical communication between them. Traditional droop control methods have the drawback of an inherent trade-off between power sharing and voltage and frequency regulation. An adaptive droop control method is proposed, which can operate in both the island mode and the grid-connected mode. It can also ensure smooth switching between these two modes. Furthermore, the voltage and frequency of a MG can be restored by using the proposed droop controller. Meanwhile, the active power can be dispatched appropriately in both operating modes based on the capacity or running cost of the Distributed Generators (DGs). The global information (such as the average voltage and output active power of the MG and so on) required by the proposed droop control method to restore the voltage and frequency deviations can be acquired distributedly based on the Multi Agent System (MAS). Simulation studies in PSCAD demonstrate the effectiveness of the proposed control method.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.692-695
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• 2003

Generally, photovoltaic system is composed with several solar cell modules. For increasing power of photovoltaic systems, serial and parallel connection needed. A Desirable characteristic of a parallel supply system is that individual converters share the load current equally and stably. The current sharing(CS) can be implemented using two approaches. The first one, known as a droop method, relies on the high output impedance of each converter. and The second approach, known as active current-sharing techniques. In this paper, using droop method at parallel connection with it's convenience and simplicity.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1060-1068
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• 2018

Droop control schemes have been widely employed in the control strategies for Multi-Terminal Direct Current (MTDC) system for its high reliability. Under the conventional DC voltage-active power droop control, the droop slope applies a proportional relationship between DC voltage error and active power error for power sharing. Due to the existence of DC network impedance and renewable resource fluctuation, there is inevitably a DC voltage deviation from the droop characteristic, which in turn results in inaccurate control of converter's power. To tackle this issue, a piecewise droop control with DC voltage dead band or active power dead band is implemented into controller design. Besides, an advanced droop control scheme with versatile function is proposed, which enables the converter to regulate DC voltage and AC voltage, control active and reactive power, get participated into frequency control, and feed passive network. The effectiveness of the proposed control method has been verified by simulation results.

• Journal of Power Electronics
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• v.13 no.3
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• pp.479-486
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• 2013

This paper presents a control strategy for distributed systems, which can be used in islanded microgrids. The control strategy is based on the droop method, which uses locally measured feedback to achieve load current sharing. Instead of the traditional droop method, an improved one is implemented. A virtual inductor in the synchronous frame for three-phase inverters is proposed to deal with the coupling of the frequency and the amplitude related to the active and reactive power. Compared with the traditional virtual inductor, the proposed virtual inductor is not affected by high frequency noises because it avoids differential calculations. A model is given for the distributed generation system, which is beneficial for the design of the droop coefficients and the value of the virtual inductor. The effectiveness of the proposed control strategy is verified by simulation and experiment results.

• Advances in Energy Research
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• v.3 no.2
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• pp.81-95
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• 2015

Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.