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Space-vector pulsewidth modulation for a seven-level cascaded H-bridge inverter with the control of DC-link voltages

Lewicki A., Morawiec M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

619--628

EN

A control strategy of DC-link voltages for a seven-level cascaded H-bridge inverter is proposed in this paper. The DC-link voltage balancing is accomplished by an appropriate selection of H-bridges and control of their duty cycles in space-vector modulation (SVM) algorithm. The proposed SVM method allows to maintain the same voltage level on all inverter capacitors. Regardless of the balancing function, the SVM strategy makes it possible to generate the output voltage vector properly also in the case where the DC-link voltages are not balanced. The results of simulation and experimental investigations are presented in the paper.

2

Power electronic transformer based on cascaded H-bridge converter

Morawiec M., Lewicki A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

675--683

EN

In this paper the control strategy of power electronic transformer (PET) is proposed. The analyzed structure of PET uses two seven-level cascaded H-bridge (CHB) rectifiers. The electrical power of PET is transferred between DC-links of CHB converters using dual-active-bridges (DABs) and low voltage high frequency transformers. The roposed solution allows for controlling the active and reactive power with a low level of harmonic distortions. The DC-link voltages and the load of the utilized H-bridges are controlled using appropriate modulation strategy. The theoretical issues are confirmed by simulation and experimental results.

3

Model predictive control of multilevel cascaded converter with boosting capability – experimental results

Wiatr P., Kryński A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

589--599

EN

The main goal of this paper is to present a five-level converter with the feature of output voltage boosting capability. Thanks to its modular construction and single DC source usage, 5LCHB converter becomes an important alternative for two-level converters operating with DC-DC converters that use bulky inductors. Furthermore, model predictive control (MPC) method is presented, which allows for boosting output voltage of presented converter while providing three-phase load current control and flying capacitor voltage stabilization. The last section describes a 5kVA laboratory model of five-level hybrid converter interfacing RL load and shows experimental results confirming theoretical analysis derived in previous sections.

4

Modeling and current control strategy for a medium-voltage cascaded multilevel statcom with LCL filter

Zhao X., Shi L., Chen L., Xia Z., Bendre A. R.

Journal of Power Technologies

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2015

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Vol. 95, nr 1

1--13

EN

The Static Synchronous Compensator (STATCOM a.k.a. SVG) is widely used to regulate dynamic reactive power and to solve dynamic voltage stability problems. Modeling shows that a cascaded STATCOM, which is composed of several cascaded H-bridges, not only has strong coupling characteristics when an LCL filter is added but it is also a non-linear, multivariable system. Therefore, its practical design and application are dicult to implement. In this paper an internal decoupling control algorithm is introduced to provide independent control of the active and reactive currents. Decoupling control algorithms are proposed, and models and simulation of the decoupling are provided. We describe the setting up of a simulation and experiments with a cascaded STATCOM based on combined circuit topology with a multi-field programmable gate array (FPGA), and double-loop control algorithms with a current inner loop, and a capacitor voltage outer loop. To provide control of the current inner loop, proportional-integral (PI) and resonant controllers are used, having the control ability to cancel harmonics while compensating for the reactive power. This paper presents new current-tracing control models that compensate for the fundamental current and eliminate selective harmonics by adopting a d-q synchronous reference frame, and a discrete Fourier transform (DFT). Voltage balance is realized by introducing modulation wave distribution strategies. Furthermore, both simulation and experiments are employed to verify the feasibility and eectiveness of the control strategy.