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In AC/DC power distributions networks, power converters are interfacing buses to ensure DC voltage regulation and power distribution. Active front ends are used between AC and DC buses and two typical control schemes that can be implemented are voltage regulation or power regulation. On the DC side, open‐loop operated DC transformers could be used between two DC buses to provide voltage adaptation, isolation and natural power flow. In this context, power flows and DC bus voltages in the power distribution network are dependent on the combined operation of the active front ends and the DC transformer. Mainly studied from a stability perspective, this interdependency between active front ends and DC transformers has lacked investigations in terms of dynamics. Fast dynamics is nevertheless important to operate optimally a network. In this paper, the assessment of the dynamic performance for distribution systems with DC transformers is performed for different mixes of voltage regulating and power regulating active front ends. The influence of DC line length and DC transformer power reversal method on the system is further investigated. A model of the system is proposed, validated experimentally and can be used to aid system level design and analysis of future DC systems. [ABSTRACT FROM AUTHOR]

This article presents a maximum torque per ampere strategy for a five-phase synchronous reluctance drive. The approach is developed considering general machine parameters and is formalized as a constrained optimization problem. The optimal solution is found analytically by using Lagrange’s multipliers method and is based on the computation of the eigenvalues and eigenvectors of the inductance derivatives matrix. The proposed approach is evaluated both numerically and experimentally. It is also compared with other current references control strategies, effectively showing a reduction of the machine rms currents for the same developed torque. The same approach can also be extended to machines with a different number of phases. [ABSTRACT FROM AUTHOR]

The article presents a novel carrier-based pulsewidth modulation technique for multiphase neutral point clamped converters. The technique is aimed to actively control the neutral point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole common mode voltage injection or on the sole multistep switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index, and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms. [ABSTRACT FROM AUTHOR]

In this article, a new pulsewidth modulation technique is proposed for the output voltage control and the dc-bus capacitors voltage balancing of a multipoint-clamped multilevel converter. The voltage equalization is achieved by allowing each converter's leg voltage to switch through multiple levels in a single modulation period (multistep operation). The approach is generalized with respect to the number of levels and phases and can be applied regardless of the converter operating conditions. Nevertheless, the multistep behavior generally leads to an increase of the average switching transitions rate. In the proposed method, this drawback is mitigated with an online adaptive selection of the number of switching levels. The algorithm is validated through an extensive hardware-in-the-loop testing and compared to other approaches. [ABSTRACT FROM AUTHOR]

This article proposes a space-vector modeling formalism and a harmonic balance control strategy for the voltage equalization of a double-star modular multilevel converter employed as an active interface between a three-phase ac grid and an HVdc grid. The balancing procedure is based on the control of the power flow through the converter legs, with the aim to stabilize the energy stored in each switching module to the same value. By properly exploiting both the space-vector/zero-component and the common/differential mode decompositions, the proposed approach is able to highlight all the viable interactions between the system voltages and currents. The harmonic balance control is then formulated in its most general form in order to effectively increase the degrees of freedom available to the voltage equalization while guaranteeing the hardware constraints and functional requirements of the converter. The resulting control algorithm, based on a subset of the harmonic control variables, has been implemented on a controller board and experimentally validated on a 1.5-kW test bench. [ABSTRACT FROM AUTHOR]

This paper deals with a Power Electronic Transformer (PET) topology for a 3-phase AC distribution grid. In the discussed topology, a Modular Multilevel Converter (MMC) and a Full-Bridge converter are employed for the medium voltage (MV) and the low voltage (LV) side, respectively. By using the space vector, approach a mathematical model for the MMC is presented and a grid-synchronous algorithm is implemented to easily control the power flow through the structure. The MV and LV side converters are linked through a High Frequency (HF) transformer, whose control strategy is a Dual-Active Phase-Shift Control (PSC) with Square Wave Modulation (SQM). This technique is combined with a predictive algorithm, which is able to keep each leg's capacitors' voltages balanced both in stationary and in transient conditions. The proposed algorithm is numerically validated in the Matlab/Simulink® environment. [ABSTRACT FROM AUTHOR]