Improved Direct Power Control for Grid-Connected Voltage Source Converters

EEE Ind. Electron. Mag.

Blaabjerg

et al. 2019

Self Cite

This article discusses the mathematical relationship between the grid-voltage-modulated-directpower-control (GVM-DPC) and the vector-current-control (VCC) for three-phase voltage-source-converters (VSCs). It reveals that the GVM-DPC is equivalent to the VCC at the steady-state, yet presents a superior transient performance by removing the need of phase-locked loop (PLL). That means the GVM-DPC solves the disadvantage of conventional DPC such as poor steady-state performance. Moreover, the GVM-DPC will reduce the computational burden in comparison with the VCC due to the absence of Park transformation and PLL. Consequently, we can expect that the GVM-DPC method has a good capability of plug-and-play for the VSC. Finally, the experiment results match the theoretical expectations closely. Index Terms Direct power control, vector current control, voltage source converters, phase-locked loop. I. INTRODUCTION OF CONTROL OF GRID-CONNECTED VOLTAGE-SOURCE CONVERTERS Voltage source converter (VSC) is widely used in the application of smart grid, flexible AC transmission systems, and renewable energy sources (e.g., wind and solar) [1]-[6]. Various control methods are researched for VSC to improve its performance, stability, and robustness [7].

Section: Controller Design For Gvm-dpcmentioning

confidence: 99%

“…4). The main disadvantage of the conventional DPC method is the steady-state performance (i.e., power ripple) compared to the VCC method designed in the d-q frame [25], [37]. However, the GVM-DPC has a similar active power tracking performance compared to the VCC method, as shown in Fig.…”

Section: Performance Validationmentioning

confidence: 99%

Control of Grid-Connected Voltage-Source Converters: The Relationship Between Direct-Power Control and Vector-Current Control

EEE Ind. Electron. Mag.

Blaabjerg

et al. 2019

Self Cite

“…Moreover, the system is a time-varying one since both control inputs are multiplied by the grid voltages. To simplify the dynamics in (8), we use the GVM control inputs defined in [47], [48], which are a similar concept in [20], [51] as follows:…”

Section: Modeling Of Voltage Source Invertersmentioning

confidence: 99%

Vector Current Control Derived from Direct Power Control for Grid-Connected Inverters

IEEE Trans. Power Electron.

Blaabjerg

2019

Self Cite

103

We propose a vector current control derived from direct power control (VCC-DPC) for a three-phase voltage source inverter (VSI) in the synchronous rotating frame through instantaneous real and reactive powers. The proposed VCC-DPC method has the same control structure as the conventional VCC except for the coordinate transformation, since we obtain the d-q axes currents model of VSI without using Park transformation and the PLL system. Consequently, the proposed method has the same property as the conventional VCC if the PLL extracts the phase angle of the grid voltage correctly. However, with the consideration of the slow dynamics of the PLL, the proposed method has an enhanced dynamical performance feature compared with the conventional VCC. Moreover, it has another benefit that the reduction of the computational burden could be expected since there is no Park transformation and the PLL in the controller implementation. We can guarantee that the closed-loop system with the proposed method is exponentially stable in the operating range. Finally, both simulation and experimental results using a 15-kW-inverter system match the theoretical expectations closely. Index Terms-Voltage source inverter, vector current controller, instantaneous real and reactive powers, exponentially stable.

“…Recently, Gui et al introduced a grid voltage modulated-DPC (GVM-DPC), which solves the main disadvantage of the DPC method, the steady-state performance [36], [37]. It may be easily designed and analyzed for the grid-connected VSIs through various linear control techniques since a linear timeinvariant (LTI) system is obtained based on the GVM-DPC…”

Section: Introductionmentioning

confidence: 99%

Voltage-Modulated Direct Power Control for a Weak Grid-Connected Voltage Source Inverters

IEEE Trans. Power Electron.

et al. 2019

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In this paper, we design a voltage modulated direct power control (VM-DPC) for a three-phase voltage source inverter (VSI) connected to a weak grid, where the PLL system may make the system unstable if the conventional vector current control (VCC) method is applied. Compared with the conventional VCC method, the main advantage of the proposed VM-DPC method is that the PLL system is eliminated. Moreover, in order to inject the rated real power to the weak grid, the VSI system should generate some certain amount of reactive power as well. An eigenvalues based analysis shows the system with the proposed method tracks its desired dynamics in the certain operating range. Both simulation and experimental results match the theoretical expectations closely. Index Terms-Voltage source inverter, voltage modulated direct power control (VM-DPC), vector current controller, weak grid, stable system.