Linear quadratic regulator based current control of grid connected inverter for Renewable Energy Applications

Vinifa, R.; Kavitha, A.

doi:10.1109/iceets.2016.7582908

Cited by 6 publications

(3 citation statements)

References 2 publications

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“…Employing a system state-space model, the controller gains are designed based on a linear quadratic regulator (LQR). Usually, LQR cost factors are designed manually [13][14][15]. However, in this paper, a sensitivity analysis is proposed to choose the LQR cost factors.…”

Section: Introductionmentioning

confidence: 99%

Direct AC voltage control for grid-forming inverters

Qoria

Oue

et al. 2019

J. Power Electron.

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Grid-forming inverters usually use inner cascaded controllers to regulate output AC voltage and converter output current. However, at the power transmission system level where the power inverter bandwidth is limited, i.e., low switching frequency, it is difficult to tune controller parameters to achieve the desired performances because of control loop interactions. In this paper, a direct AC voltage control-based state-feedback control is applied. Its control gains are tuned using a linear quadratic regulator. In addition, a sensitivity analysis is proposed to choose the right cost factors that allow the system to achieve the imposed specifications. Conventionally, a system based on direct AC voltage control has no restriction on the inverter current. Hence, in this paper, a threshold virtual impedance has been added to the state-feedback control in order to protect the inverter against overcurrent. The robustness of the proposed control is assessed for different short-circuit ratios using smallsignal stability analysis. Then, it is checked in different grid topologies using time domain simulations. An experimental test bench is developed in order to validate the proposed control.

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Section: Introductionmentioning

confidence: 99%

Direct AC voltage control for grid-forming inverters

Qoria

Oue

et al. 2019

J. Power Electron.

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“…In the middle of designing the LQR, exponential weighting is used for the sake of robust performance and fast response of IC. In [21], LQR technique is proposed for the current control of grid-connected inverter by considering its advantages, such as good transient response and excellent stability margins. Other applications of LQR for converter control are on three-phase power converters Space Vector Pulse Width Modulation (SVPWM) [22], multi-loop linear control strategy for UPS inverter [23], and a three-phase three-switch three-level AC/DC converter [24].…”

Section: Hybrid Ac/dc Microgrid Operationmentioning

confidence: 99%

Interlink Converter with Linear Quadratic Regulator Based Current Control for Hybrid AC/DC Microgrid

2017

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A hybrid alternate current/direct current (AC/DC) microgrid consists of an AC subgrid and a DC subgrid, and the subgrids are connected through the interlink bidirectional AC/DC converter. In the stand-alone operation mode, it is desirable that the interlink bidirectional AC/DC converter manages proportional power sharing between the subgrids by transferring power from the under-loaded subgrid to the over-loaded one. In terms of system security, the interlink bidirectional AC/DC converter takes an important role, so proper control strategies need to be established. In addition, it is assumed that a battery energy storage system is installed in one subgrid, and the coordinated control of interlink bidirectional AC/DC converter and battery energy storage system converter is required so that the power sharing scheme between subgrids becomes more efficient. For the purpose of designing a tracking controller for the power sharing by interlink bidirectional AC/DC converter in a hybrid AC/DC microgrid, a droop control method generates a power reference for interlink bidirectional AC/DC converter based on the deviation of the system frequency and voltages first and then interlink bidirectional AC/DC converter needs to transfer the power reference to the over-loaded subgrid. For efficiency of this power transferring, a linear quadratic regulator with exponential weighting for the current regulation of interlink bidirectional AC/DC converter is designed in such a way that the resulting microgrid can operate robustly against various uncertainties and the power sharing is carried out quickly. Simulation results show that the proposed interlink bidirectional AC/DC converter control strategy provides robust and efficient power sharing scheme between the subgrids without deteriorating the secure system operation.

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“…The reference currents are generated in such a way that the reactive and harmonic components are compensated. Several techniques are discussed by many researchers to generate reference currents using instantaneous p ‐ q theory [17], synchronous detection method [18], symmetrical component theory [19], and Fryze current minimisation method. However, the linearity between voltage and current is maintained in Fryze current minimisation technique under unbalanced grid voltage conditions too [20].…”

Section: Introductionmentioning

confidence: 99%

Sliding mode controller‐based voltage source inverter for power quality improvement in microgrid

Rajakumar

Kavitha

2020

IET Renewable Power Generation

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Development of control technologies facilitates the integration of renewable energy sources to the grid through power electronic converters. In this study, the inverter acts as shunt active power filter along with the power conversion operation. Various sliding mode control (SMC) techniques namely relay and signum method, hysteresis method and equivalent control method are implemented to control the real, and reactive power flow between Renewable Energy System (RES), load and grid using an inverter. To reduce the complexity, the control law (u eq) for equivalent control method is derived using a simple singlephase equivalent circuit of a three-phase voltage source inverter. In this study, the robustness is enhanced by choosing the integral sliding surface. These controllers are used to reduce the total harmonic distortion (THD) and to ensure unity power factor (PF) in the grid during balanced and unbalanced grid voltage conditions even in the existence of nonlinear loads. The SMC using equivalent control function outperforms the other methods in terms of chattering, THD and PF. To illustrate the effectiveness, three different modes are considered: (i) no RES power, (ii) insufficient RES power and (iii) excess RES power. The performance of controllers is validated by the simulation and experimental results.

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Linear quadratic regulator based current control of grid connected inverter for Renewable Energy Applications

Cited by 6 publications

References 2 publications

Direct AC voltage control for grid-forming inverters

Direct AC voltage control for grid-forming inverters

Interlink Converter with Linear Quadratic Regulator Based Current Control for Hybrid AC/DC Microgrid

Sliding mode controller‐based voltage source inverter for power quality improvement in microgrid

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