Discrete-Time DC-Link Voltage and Current Control of a Grid-Connected Inverter with LCL-Filter and Very Small DC-Link Capacitance

Kalmbach, Oliver; Dirscherl, Christian; Hackl, Christoph M.

doi:10.3390/en13215613

Cited by 7 publications

(4 citation statements)

References 56 publications

(90 reference statements)

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“…Important to note that the approach (27) can easily be extended to a generic PIR ± k controller up to the k-th harmonic order as can be seen in ( 28). The gain matrices are obtained by the aforementioned LQR tuning [23,24]. To do so, the closedloop system and input matrices of the closed-loop system ( 13) and (28) must be derived.…”

Section: DC and Circulating (σ-) Current Controlmentioning

confidence: 99%

I/O-Linearization Based Current Decoupling Control of Modular Multilevel Cascade Converters

Kalmbach¹,

Hackl²

2023

Preprint

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<p>A generic current control system for modular multilevel cascade converters (MMCCs) is proposed. It is based on (i) input/output-linearization (I/O-linearization), (ii) feedforward disturbance compensation and (iii) parallelized proportional-integral-resonant controllers to compensate for arbitrarily many harmonics (including positive and negative sequence). The controller design is performed in state space. It is generic and flexible and combines pole placement and LQR tuning. Moreover, it allows to take all system parameters such as cluster or output (grid) inductances or resistances individually into account during controller design and tuning. Moreover, the typically imposed simplifying assumptions on system dynamics (e.g., identical parameters) or operating conditions (e.g., balanced loading) can be overcome. The proposed control system is validated for a dual-star bridge-cell MMCC. The simulation results illustrate its excellent control performance under ideal but also non-ideal conditions, where conventional approaches usually fail. </p>

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Section: DC and Circulating (σ-) Current Controlmentioning

confidence: 99%

I/O-Linearization Based Current Decoupling Control of Modular Multilevel Cascade Converters

Kalmbach¹,

Hackl²

2023

Preprint

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“…In case that a lower sampling frequency is selected, higher-order discretization methods can be implemented as presented in [30]. Furthermore, the controllability and observability of system in Equations ( 4) and ( 5) are studied in the continuous-and discrete-time domain in [31,32], respectively.…”

Section: System Model Of Grid-connected Invertermentioning

confidence: 99%

“…In this subsection, the influence of the grid impedance variation on the resonant frequency is presented. Considering that the series configuration of L 2 and L g is combined as L 2g = L 2 + L g , the transfer function from the inverter voltage to the grid-side current is obtained from Figure 2 as [5,30]:…”

Section: Frequency Response Of Lcl Filter Under Grid Impedance Changementioning

confidence: 99%

Stability Assessment of Current Controller with Harmonic Compensator for LCL-Filtered Grid-Connected Inverter under Distorted Weak Grid

2020

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An assessment of the stability and performance of current controllers with harmonic compensators is presented for an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter under distorted weak grid conditions. By using two typical current control schemes which are the direct current controller with the capacitor current-based active damping and integral-resonant state feedback current controller, the closed-loop system stability and current control performance are investigated in the presence of both uncertain grid impedance and distorted grid. Even though the controller stability has been investigated under weak grid in several studies, the stability assessment of the entire current control scheme, including the harmonic resonant controllers, still needs a further comprehensive investigation. The system stability is analyzed by obtaining the movement of the closed-loop poles in the discrete-time domain when the grid impedance varies. To fully study the impact of distorted weak grid condition on the LCL filters, three LCL filter parameter sets giving the resonance frequency in different frequency bands are chosen for the purpose of evaluating the system robustness and grid-injected current quality. In order to support the presented theoretical analyses, comprehensive simulation and experimental results based on 32-bit DSP TMS320F28335 to control 2 kVA grid-connected inverter are presented in terms of grid current quality and control stability in the environment of both uncertain grid impedance and distorted grid.

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“…These effects are even more accentuated in DERs based on intermittent sources, DER interconnected to weak grids, or caused by local nonlinear loads in the PCC [5]. To mitigate such harmonic distortions, several studies have been proposed, using passive filters such as L, LC, and LCL configurations [6]; using active filters [7]; or energy storage systems [8]. Wind turbines (WT) generators have been developed, with most being based on synchronous or induction machines concerning wind energy.…”

Section: Introductionmentioning

confidence: 99%

Modeling and Harmonic Impact Mitigation of Grid-Connected SCIG Driven by an Electromagnetic Frequency Regulator

2021

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The power quality analysis is an essential issue in the integration of distributed energy resources to the grid. Recent standards regulate the harmonics disturbances due to the increasing penetration of intermittent energy sources interconnected with the grid employing power converters. This paper aims to analyze the power quality of an interconnected wind turbine system based on a Squirrel Cage Induction Generator (SCIG) driven by an Electromagnetic Frequency Regulator (EFR). The steady state of the EFR harmonic model is developed in the stationary frame based on the conventional induction generator modeling, which allows the study of the harmonic disturbances in the electrical and mechanical variables due to the PWM inverter of the EFR’s armature voltage. There is no electrical connection between the EFR and SCIG, and the results show that the inherent system inertia contributes to the mitigation of the harmonic content at the grid side generated by the switching. In addition to the steady-state results, the Total Rated Distortion (TRD), which considers the harmonics and interharmonics components, was computed and presented a good performance compared to the IEEE 1547 standard and real data extracted of a single Doubly Fed Induction Generator (DFIG). Finally, the harmonic performance of the proposed system was evaluated considering the impact of the equivalent Thevenin impedance of the grid at the Point of Common Coupling (PCC).

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Discrete-Time DC-Link Voltage and Current Control of a Grid-Connected Inverter with LCL-Filter and Very Small DC-Link Capacitance

Cited by 7 publications

References 56 publications

I/O-Linearization Based Current Decoupling Control of Modular Multilevel Cascade Converters

I/O-Linearization Based Current Decoupling Control of Modular Multilevel Cascade Converters

Stability Assessment of Current Controller with Harmonic Compensator for LCL-Filtered Grid-Connected Inverter under Distorted Weak Grid

Modeling and Harmonic Impact Mitigation of Grid-Connected SCIG Driven by an Electromagnetic Frequency Regulator

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