Dual Grid Voltage Modulated Direct Power Control of Grid-Connected Voltage Source Converter under Unbalanced Network Condition

This paper proposes a constant-frequency model predictive direct power control (CF-MPDPC) method for a fault-tolerant bidirectional voltage-source converter (BVSC). The method can enhance the reliability and fault-tolerant operation capability of BVSCs in the condition of bridge-arm fault. Through the analysis of a fault-tolerant three-phase four-switch (TPFS) structure and the voltage vectors in the αβ stationary frame, the predictive power model and DC-link midpoint voltage offset suppression are established. According to model-predictive theory, fault-tolerant TPFS, and multivector control, the CF-MPDPC method for fault-tolerant BVSC is presented. The method realizes direct power control based on three output vectors with constant frequency, which can track the optimal vector more accurately and reduce current harmonics. Furthermore, the balanced control of DC-link capacitor voltages is also achieved by adding the term of DC-link midpoint voltage offset into the cost function. The balanced capacitor voltages protect the converter against the second faults caused by over-voltage operation of electrolytic capacitor. The simulation and experimental results prove that the fault-tolerant BVSC controlled by proposed method can maintain the continuous operation when the switching devices have fault. Low current harmonic content and stable output power exhibit good reliability and dynamic performance of the proposed CF-MPDPC for a fault-tolerant BVSC with a phase fault.

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Virtual Flux Predictive Direct Power Control of Five-level T-type Multi-terminal VSC-HVDC System

Periodica Polytechnica Electrical Engineering and Computer Science ◽

10.3311/ppee.14441 ◽

2020 ◽

Vol 64 (2) ◽

pp. 133-143

Author(s):

Ahmed Reguig Berra ◽

Said Barkat ◽

Mansour Bouzidi

Keyword(s):

Power Control ◽

Reactive Power ◽

Operating Conditions ◽

Voltage Source ◽

Voltage Source Converter ◽

Switching Frequency ◽

Direct Power ◽

Direct Power Control ◽

Active And Reactive Power ◽

Virtual Flux

This paper proposes a Virtual Flux Predictive Direct Power Control (PDPC) for a five-level T-type multi-terminal Voltage Source Converter High Voltage Direct Current (VSC-HVDC) transmission system. The proposed PDPC scheme is based on the computation of the average voltage vector using a virtual flux predictive control algorithm, which allows the cancellation of active and reactive power tracking errors at each sampling period. The active and reactive power can be estimated based on the virtual flux vector that makes AC line voltage sensors not necessary. A constant converter switching frequency is achieved by employing a multilevel space vector modulation, which ensures the balance of the DC capacitor voltages of the five-level t-type converters as well. Simulation results validate the efficiency of the proposed control law, and they are compared with those given by a traditional direct power control. These results exhibit excellent transient responses during range of operating conditions.

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