P. Marino

A new high performance shunt active filter based on digital control

A new high performance shunt active filter is presented. It is based on a new control strategy, which utilizes the supply current regulation and a robust filtering algorithm, implemented by means of a digital controller. The supply current reaction ensures the digital control delay does not produce supply current spikes and a new filtering algorithm ensures the active filter performances do not decrease in the presence of unbalanced and distorted supply voltage conditions. Comparative simulations among the proposed active filter and filters based on the most widespread control techniques present in literature show the advantages of the proposed solution.

A new DSP controlled shunt active filter for nonideal supply conditions

A new DSP controlled shunt active filter, proposed by the same authors in a previous paper (see IEEE PES Winter Meeting, 2000), is implemented, tested and compared with other shunt active filters. The active filter is based on a supply current regulation implemented by means of an analog controller, and a robust filtering algorithm implemented by means of a digital controller. It is suitable for nonideal supply conditions and overcomes the DSP implementation drawbacks. Laboratory tests on an IGBT inverter show the advantages of the proposed solution with respect to the most widespread active filters presented in literature.

A new method based on periodic convolution for sensitivity analysis of multi-stage conversion systems

A new approach for sensitivity analysis of harmonics and interharmonics in multi-stage conversion systems is presented. Each component (converter, filter, transformer, etc.) is modeled by taking advantage of periodic convolution and representing the signals by means of a discrete Fourier transform. Firstly, single component frequency coupling matrices are built up starting from the component characteristics. Then, according to the specific topology of the conversion system, single-component matrices are combined to deduce a whole-system frequency coupling matrix: it provides the coupling among the harmonics and interharmonics of voltages and currents. The operative procedure to build up the frequency coupling matrix of a complex AC/DC/AC PWM adjustable speed drive is described: it is very fast and efficient. In particular, the frequency coupling matrix is utilized to perform a sensitivity analysis of the absorbed current with respect to the supplying voltage perturbations around a fixed operating point, developed with reference to a specific case-study.

A frequency domain model for AC/DC/AC conversion systems

A simple model in the frequency domain of AC/DC/AC conversion systems is presented and applied to predict DC and AC current harmonics and interharmonics. It is based on the modulation function theory, but differently from the classical approaches, it allows prediction in a fast and direct way those current interharmonics which are caused by the time variation of the actual inductance seen from the conversion system DC-link. The method utilizes a simple linearization of time varying inductances, so allowing achievement of better modeling capabilities without reducing the inherent simplicity and speed of the classical approaches. Comparative tests are performed to validate the proposed method and to demonstrate its improved performances.

Three-phase robust series compensator for voltage disturbances

In this paper the problem of voltage disturbances compensation in a three-phase three-wire electrical industrial system is addressed. A robust synchronous-based control algorithm is proposed for both endogenous and exogenous voltage disturbances compensation. The compensator is made of series transformers fed by a PWM-voltage source inverter (VSI). The control system regulates to zero the d- and q- components of the fundamental negative sequence of the supply voltages and compensates their harmonic content, by means of a feed-forward and of a feedback action. The influence of the passive filter for the switching ripple, on the compensator performances, has been investigated. Numerical simulations validate the effectiveness of the proposed compensation strategy.

Active front-end design criteria

In this paper some design criteria for an active front-end (AFE) are presented. The rules are formulated on the basis of the rated power of the line where the AFE is connected. The proposed AFE is based on the voltage processing and supply current reaction algorithm for power shunt active filters and performs the AC-DC conversion, the line current distortions and the reactive power compensation. A shunt capacitive filter is presented to compensate not only the node voltage disturbances due to the AFE switching, but also the average reactive power. The design criteria and the problems connected to the passive filter are discussed. Numerical simulations validate the proposed criteria.

Design criteria for a multifunctional AC/DC boost converter

Design criteria are presented for a multifunctional AC/DC boost converter, used in an industrial subsystem not only to transfer power from AC to DC side, but also to improve power quality. The converter has already been presented in previous papers by the same research team. In this paper the design of converter passive components, input filter and transformer impedance is related to the converter performances and useful criteria are deduced. Finally, numerical experiments validate the proposed criteria and highlight their usefulness.

Active filtering of low frequency harmonics in DC/DC converters for traction applications

The line-side DC/DC converter used for ETR500P traction train by ANSALDO Trasporti SpA (Italy) is considered. A new active filtering technique is proposed in order to compensate for undesired input current harmonics. The compensation technique does not require any additional power converter and it is based on an on-line detection of the undesired harmonic to be eliminated. The controller is designed by using an equivalent circuit of the DC/DC converter, obtained by means of a proper transformation of its state space model. Simulation results show the effectiveness of the proposed technique.

High-performance single-phase high-power Active Front-End

A high-performance single-phase active front-end (AFE) for modern railway applications is presented. It can successfully manage the well known trade-off between high power handling and high switching frequency, with regard to utility side effects. The proposed system is made-up by two parallel-connected two-level single-phase AC-DC boost converters with common dc-link capacitor. One is a high-power AC-DC boost converter which behaves as an unitary displacement power factor (DPF) AC-DC rectifier. It works at a low switching frequency and so it is able to control the fundamental components of the line currents only to be aligned with the positive sequence of the node voltages. Adding a low-power high-frequency boost converter working as an active parallel compensator (APC), the whole system also allows a low THD factor at the point of common coupling (PCC).

High-performance three-phase three-wire high-power active front-end

A high-performance three-phase active front-end (AFE) for high-power applications is presented. It can successfully manage the well known trade-off between high power handling and high switching frequency, with regard to utility side effects. The proposed system is made-up by two parallel-connected two-level three-phase AC-DC boost converters with common DC-link capacitor. A high-power AC-DC boost converter which behaves as unitary displacement power factor (DPF) AC-DC rectifier. It works at low switching frequency and so it is able to control only the fundamental components of the line currents to be aligned with the positive sequence of the node voltages. Adding a low-power high-frequency boost converter working as an active parallel compensator (APC), the overall system also allows a low THD factor at the point of common coupling (PCC). An efficient digital control algorithm is proposed for both the converters, using an innovative PLL strategy.