Volume 4, No. 11 (2005)

AC-AC CONVERTER FOR INDUCTION MOTOR APPLICATION

GAICEANU MARIAN

The goal of this paper is to present the topology, the control design and the experimental results of the 37 kW high performance quasi direct ac-ac converter prototype. The control algorithms and the strategy adopted in this paper are well suited for the ac drives application area. The complete ac-ac system is presented, but the main research interest was focused on the input conversion stage with the scope of meeting the following specifications: unity power factor operation; low input current harmonics; regeneration capability; reduced size of reactive components; full exploitation of the supply voltage. Although the output power inverter determines the overall drive performance, it has been treated only marginally since the conventional field oriented control was used. The overall system control has been designed to tightly balance the power flow in the system. Therefore, a small plastic film capacitor was used instead of the big electrolytic one, as with indirect ac-ac converters. The feed-forward load component has been added to the current reference of the source converter and thus, improving performances were obtained during the transients because of the fast control response to load changes (the feed-forward component was introduced in the inner control loop of the system). The stationary and transitory performances of the ac-ac converter system are shown through the experimental results, and so are the motor and regenerative operations.

PARALLEL ACTIVE POWER FILTER BASED ON SYNCHRONOUS REFERENCE FRAME ALGORITHM

GAICEANU MARIAN

In this paper a 33kVA Active Power Filter (APF) prototype based on the synchronous d-q reference frame (SRF) control method, well-known in the motor drives industry, is presented. The proportional-integral controllers are used for the voltage and current control loops. The proposed scheme employs a pulse-width modulation (PWM) voltage-source inverter. The APF prototype has been developed in order to meet the harmonics limits imposed by the IEEE Standard 519 [1] under all supply and load conditions. The main project objectives have been to design, realize and test an active power filter. In particular, the new apparatus had to have the following features: to control the active filter in a closed loop manner so as to actively shape the source current into the sinusoid; to compensate transient and harmonic components of the load current. The performance evaluation has been done on the basis of the %THD in the load current and the compensated mains current. Experimental results have shown that the APF system meets the IEEE 519 harmonic current limits in the supply.

SOME CONSIDERATIONS REGARDING THE POWER DIODES AND THEIR SPICE MODELS

GRIGORESCU LUIZA, DIACONESCU IOANA

The paper brings into the specialists’ attention some of the major issues about the characteristics of power diodes. Starting from the commutation characteristics and the commutation waveforms, there can be explained some of the issues regarding the direct and reverse commutation. The SPICE model for the power diode shown in the paper’s closure emphasizes both the phenomena specific to reversed return and that specific to direct return, mainly the voltage peak manifested on direct commutation.

OPTIMAL SIGNAL RECEPTION. THE MATHEMATICAL MODEL OF THE ADAPTIVE FILTER.

GRIGORESCU LUIZA, DIACONESCU IOANA

The authors take into discussion some of the issues specific to signal’ reception. The received signal is transformed by the receiver into a time dependant function, a number or a Boolean variable. The study of such transformation requires the defiition of the functions group corresponding to the periodic signal, of the finite amplitude signals and the finite energy signals. The simplest model, and also the most important one for clearing the basic aspects of this issues, has imposed the assumption that the parasite influence of the received signal are additive. The method for the elimination of the additive noise and the extraction of the purified information will therefore be presented.

WIRELESS CONTROL OF AN INDUSTRIAL SERIAL NETWORK WITH ARDETEM PECA 300 SIGNAL ANALYSERS

MARGINEANU IOAN, DEMETER ROBERT, ARPAD NAGY, SARKANY ISTVAN

Industrial serial networks communicate with master systems through serial ports. If we want to have a remote control for this type of applications, we can use RS232-RS485 converters. This solution limits the distance of the link to 1.2 km. Further so, these communications don’t have high speed because it is difficult to control the E/R amplifiers of the converter. We can accomplish remote control and monitor without these limitations using the possibility to transmit information over Ethernet networks (LAN, WLAN and WAN).In the paper we use virtual ports and a bi-directional Serial-Ethernet Redirector implemented in the computer and in the wireless Access Point like a client-server application, for control and monitor of a SCADA application with ARDETEM PECA 300 signal analyser.The software is transparent for the SCADA application and converts the communication protocol in UDP Datagram and vice-versa