Improved AC-current control based on state space control applied to solar string inverters

2017 ◽  
Author(s):  
Tobias Rapp ◽  
Stephan Liese ◽  
Christoph Siedle ◽  
Martin Brand ◽  
Adalberto Jose Rossa
Keyword(s):  
State Space ◽  
Current Control ◽  
Ac Current

scholarly journals Comparative Study of Classical and MPC Control for Single-Phase MMC Based on V-HIL Simulations

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3230
Author(s):  
Milovan Majstorovic ◽  
Marco Rivera ◽  
Leposava Ristic ◽  
Patrick Wheeler
Keyword(s):  
Single Phase ◽  
Current Control ◽  
Superior Performance ◽  
Control Methods ◽  
Reference Tracking ◽  
Voltage Balancing ◽  
Current Reference ◽  
Circulating Current ◽  
Ac Current ◽  
Classical Control

The operation of single-phase Modular Multilevel Converter (MMC) is analyzed in the paper. A mathematical model of the converter is developed and described, based on which the structure and selection of parameters for Classical Control and Optimal Switching State Model Predictive Control (OSS-MPC) are defined. Additionally, the procedure for the determination of circuit parameters, such as submodule capacitance and arm inductance, is described and carried out. The listed control methods are designed and evaluated in Virtual Hardware-in-the-Loop together with single-phase MMC power circuit, regarding three control objectives: AC current control, voltage balancing control and circulating current control. Control methods are evaluated for both steady-state and transient performance and compared based on nine criteria: AC current reference tracking, THD of AC current and voltage, submodule capacitor voltage balancing, total submodule voltage control, circulating current magnitude and THD, number of control parameters and computational complexity. This is the first time that a fair comparison between Classical Control and MPC is considered in literature, resulting in superior performance of both control methods regarding four different criteria and the same performance regarding AC current reference tracking.

scholarly journals Disturbance-Observer-Based Model Predictive Control for Battery Energy Storage System Modular Multilevel Converters

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2285 ◽  
Author(s):  
Yantao Liao ◽  
Jun You ◽  
Jun Yang ◽  
Zuo Wang ◽  
Long Jin
Keyword(s):  
Energy Storage ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Current Control ◽  
Multilevel Converters ◽  
Battery Energy Storage ◽  
Circulating Current ◽  
Modular Multilevel Converters ◽  
Ac Current ◽  
Battery Energy

Although the traditional model predictive control (MPC) can theoretically provide AC current and circulating current control for modular multilevel converters (MMCs) in battery energy storage grid-connected systems, it suffers from stability problems due to the power quality of the power grid and model parameter mismatches. A two discrete-time disturbance observers (DOBs)-based MPC strategy is investigated in this paper to solve this problem. The first DOB is used to improve the AC current quality and the second enhances the stability of the circulating current control. The distortion and fluctuation of grid voltage and inductance parameter variation are considered as lump disturbances in the discrete modeling of a MMC. Based on the proposed method, the output prediction is compensated by disturbance estimation to correct the AC current and circulating current errors, which eventually achieve the expected tracking performance. Moreover, the DOBs have a quite low computational cost with minimum order and optimal performance properties. Since the designed DOBs work in parallel with the MPC, the control effect is improved greatly under harmonics, 3-phase unbalance, voltage sag, inductance parameter mismatches and power reversal conditions. Simulation results confirm the validity of the proposed scheme.

scholarly journals Hysteresis-Based Current Control Approach by Means of the Theory of Switched Systems

2021 ◽  
Vol 11 (19) ◽  
pp. 9175
Author(s):  
Malte Thielmann ◽  
Florian Hans
Keyword(s):  
State Space ◽  
Switched Systems ◽  
Multiple Equilibria ◽  
Current Control ◽  
The State ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Reference Trajectory ◽  
State Variables ◽  
Control Approach

In this paper, a novel hysteresis-based current control approach is presented. The basis of the developed control approach is the theory of switched systems, in particular, the system class of switched systems with multiple equilibria. The proposed approach guarantees the convergence of the state trajectory into a region around a reference trajectory by selective switching between the individual subsystems. Here, the reference trajectory is allowed to be time varying, but lies within the state space spanned by the subsystem equilibria. Since already published approaches only show convergence to a common equilibrium of all subsystems, the extension to the mentioned state space is a significant novelty. Moreover, the approach is not limited to the number of state variables, nor to the number of subsystems. Thus, the applicability to a large number of systems is given. In the course of the paper, the theoretical basics of the approach are first explained by referring to a trivial example system. Then, it is shown how the theory can be applied to a practical application of a voltage source converter that is connected to a permanent-magnet synchronous motor. After deriving the limits of the presented control strategy, a simulation study confirms the applicability on the converter system. The paper closes with a detailed discussion about the given results.

scholarly journals State-space model of grid-connected inverters under current control mode

2007 ◽  
Vol 1 (3) ◽  
pp. 329 ◽  
Author(s):  
N. Kroutikova ◽  
C.A. Hernandez-Aramburo ◽  
T.C. Green
Keyword(s):  
State Space ◽  
State Space Model ◽  
Current Control ◽  
Control Mode ◽  
Space Model
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