Current Regulated Delta Modulation Research Articles

Predictive current control with current-error correction for PM brushless AC drives

The performance of the conventional predictive current control (PCC) when applied to a permanent-magnet brushless ac (PM BLAC) drive is analyzed. A technique is proposed to reduce the current errors that arise due to the inaccuracies in the system parameters and the nonideal behavior of the inverter during a steady-state operation. In addition, a current-regulated delta modulator is employed to achieve a fast dynamic response during a transient operation. The performance of the proposed PCC, which is simple to implement on a low-cost fixed-point DSP, is demonstrated experimentally

Improved Current-Regulated Delta Modulator for Reducing Switching Frequency and Low-Frequency Current Error in Permanent Magnet Brushless AC Drives

The conventional current-regulated delta modulator (CRDM) results in a high current ripple and a high switching frequency at low rotational speeds, and in low-frequency current harmonics, including a fundamental current error, at high rotational speeds. An improved current controller based on CRDM is proposed which introduces a zero-vector zone and a current error correction technique. It reduces the current ripple and switching frequency at low speeds, without the need to detect the back-emf, as well as the low-frequency error at high speeds. The performance of the modulator is verified by both simulation and measurements on a permanent magnet brushless ac drive.

Hybrid multilevel power conversion system: a competitive solution for high-power applications

Trends in power semiconductor technology indicate a tradeoff in the selection of power devices in terms of switching frequency and voltage-sustaining capability. New power converter topologies permit modular realization of multilevel inverters using a hybrid approach involving integrated gate commutated thyristors (IGCTs) and insulated gate bipolar transistors (IGBTs) operating in synergism. This paper investigates a hybrid multilevel power conversion system typically suitable for high-performance high-power applications. This system, designed for a 4.16 kV/spl ges/100 hp load is comprised of a hybrid seven-level inverter, a diode bridge rectifier, and an IGBT rectifier per phase. The IGBT rectifier is used on the utility side as a real power flow regulator to the low-voltage converter and as a harmonic compensator for the high-voltage converter. The hybrid seven-level inverter on the load side consists of a high-voltage slow-switching IGCT inverter and a low-voltage fast-switching IGBT inverter. By employing different devices under different operating conditions, it is shown that one can optimize the power conversion capability of the entire system. A detailed analysis of a novel hybrid modulation technique for the inverter, which incorporates stepped synthesis in conjunction with variable pulsewidth of the consecutive steps is included. In addition, performance of a multilevel current-regulated delta modulator as applied to the single-phase full-bridge IGBT rectifier is discussed. Detailed computer simulations accompanied with experimental verification are presented in the paper.

A source voltage-clamped resonant link inverter for a PMSM using a predictive current control technique

A simple source voltage-clamped resonant link (SVCRL) inverter is proposed to clamp the DC-link voltage to the input source voltage and reduce the current rating of a resonant inductor. The current control of a permanent magnet synchronous motor (PMSM) employing a predictive current control technique (PCCT) for the SVCRL, inverter is also investigated to overcome the disadvantage of the current-regulated delta modulation (CRDM) control technique. By employing the PCCT based on the discrete model of a PMSM and estimation of back electromotive force (EMF), the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

DSP-based predictive current control technique for a permanent-magnet synchronous motor using a resonant DC link inverter

A predictive current control technique for a permanent magnet synchronous motor (PMSM) employing a resonant DC link inverter is proposed to overcome the disadvantage of the current regulated delta modulation (CRDM) control technique. Also, the discrete model of a PM synchronous motor and estimation of back EMF are investigated. Based on this discrete model and estimated back EMF, a predictive current control technique is newly developed. Using the proposed control technique, the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

Performance analysis of three-phase inverters controlled by synchronous delta-modulation systems

Synchronous delta-modulation systems are used to control resonant voltage link inverters, where switching has to be synchronized with the zero crossings of the link voltage. This paper shows that output current harmonic distortion and average switching frequency of such systems can be calculated analytically in spite of the quasistochastic behavior of the modulators output. Under the assumption of constant link frequency and large ratio of link to output frequency, results are derived for three-phase sigma-delta modulation, space-vector based sigma-delta modulation, and current-regulated delta modulation. The results hold for any shape of the inverter input voltage (including DC). The output current harmonic distortion of resonant link inverters is compared with conventional hard switching PWM inverters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance characterization of a new discrete pulse-modulated current regulator

A novel discrete pulse-modulated current regulator, which controls a space vector that describes the load current, is introduced. This controller uses no additional state feedback and results in better performance than the current regulated delta modulator (CR Delta M). The proposed adjacent state discrete time current regulator, which switches between adjacent switching vectors and the zero state on the basis of the state chosen by the CR Delta M scheme, contains most of the operating characteristics of a cost function regulator, which utilizes full state feedback. Simulation results of this new regulator are compared to the CR Delta M and the cost function discrete time current regulator. The same ideas used in the discrete pulse case can be extended to form a new hard-switched hysteresis-type current regulator. In either case, the regulator is easily implemented, requiring no calculation of counter-EMF (electromotive force) or Delta I. In addition, a modified sigma/delta modulated voltage regulator that satisfies the pulse polarity consistency rule is derived. Finally, complete experimental results are given. >