Showing papers on "Synchronous frame published in 2000"

Improved voltage regulation for current source inverters

Abstract: Voltage regulation schemes for current-source inverters (CSIs) commonly use a simple proportional-integral (PI) stationary frame controller, but this approach is known to suffer from significant steady-state error. In contrast, the more advanced schemes that are routinely used for current regulation of voltage-source inverters (VSIs) avoid these problems. This paper presents an approach to directly utilize VSI current regulation strategies to control the voltage for a CSI, without requiring significant modification or development. The approach uses a space-vector mapping technique to convert VSI modulation signals to CSI gate drive signals, which allows VSI closed-loop current control strategies to be directly applied to CSI voltage regulation. Three new voltage regulation CSI controllers based on hysteresis, synchronous frame PI, and stationary frame P+Resonant control principles are presented based on this concept.

A closed-loop selective harmonic compensation for active filters

Abstract: This paper proposes a control algorithm for parallel active power filters, based on current-controlled PWM converters, which allows precise compensation of selected harmonic currents produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of the selected harmonics using closed-loop synchronous frame controllers. Because of the closed-loop operation, full compensation of the desired harmonics is achieved even in the presence of a significant delay in the VSI current control. Because of the selective approach, active filter interactions with a possible dynamic component of the load are minimized. The complexity of the synchronous frame controllers are avoided using equivalent stationary frame controllers with the same dynamic performance. Experimental results of a converter prototype confirm the theoretical expectations.

Implementation of synchronous frame harmonic control for high-performance AC power supplies

Abstract: In order to achieve the reduction of voltage distortion in AC power supplies, this paper describes an implementation of synchronous frame control for selected frequencies in the output voltage. The regulation of the fundamental output voltage, as well as of some low-order harmonics, is achieved using a synchronous frame controller for each selected frequency in addition to a conventional control. The conventional part conserves good dynamic performance under load changes, while rotating frame controllers allow a slow, but very precise compensation of the residual errors within the assumption that the harmonics produced by distorting load are slowly-varying. Moreover, motivated by a fixed-point implementation, a set of refinements and modifications of the original scheme is proposed, allowing a reduction of signal processing requirements and a new control algorithm structure less sensitive to quantization and rounding errors. This solution is particularly effective for high-power fully-digital controlled AC power supplies, where the voltage loop bandwidth is usually not large enough to provide regulation at harmonic frequencies. The proposed control scheme has been implemented using a fired-point single-chip digital signal professor (ADMC401 by Analog Devices). Experimental results on a 3 kVA three-phase converter prototype show the effectiveness of the proposed approach.

Adaptive predictive synchronous current frame regulator method and apparatus

Abstract: A method and apparatus for controlling a synchronous frame current regulator wherein the apparatus includes a current predictor and a current predictor adjuster, the current predictor predicting the current provided to a plant from both a forcing function and an actual current value and the adjuster adjusting the current prediction based on a difference between the current prediction and the actual current sampled thereby driving the actual current so as to conform with a commanded current value.

Fuzzy logic based position control of permanent magnet synchronous motor

Abstract: In this paper, the performance of a fuzzy position controller of an interior permanent magnet synchronous motor for robotic applications is investigated. A fuzzy logic controller is employed as an outer position loop. Moreover, a synchronous frame PI controller is employed as an inner speed control loop. The controllers are designed based on the indirect field oriented control. The control scheme can be used for both the position and the speed control applications by enabling and disabling the position controller. The control scheme is implemented using Digital Signal Processor TMS320C31. The performance of the proposed control scheme is investigated both theoretically and experimentally. The results indicate a good performance of the proposed scheme.

High performance active filters using selective harmonic control

Abstract: The paper discusses the application of selective harmonic compensation for parallel active power filters based on current controlled inverters. A method based on closed-loop synchronous frame control of line currents is presented and compared with conventional, possibly selective, load current detection methods. Indeed, in active filter applications where distorting loads absorb slowly varying harmonics, the compensation of selected harmonics gives several advantages, such as rating optimisation, improved performance and robustness. In fact, the aforementioned methods are able to compensate for the inverter control, achieving full compensation on the selected harmonics, and to increase the stability margin of the system in case of capacitive or resonant loads. Experimental results of both control algorithms on a 5 kVA converter prototype confirm effectiveness and advantages of selected harmonic compensation.

Floating flame controller

Abstract: A floating frame controller determines a current Park vector, selects a reference frame for the current Park vector, and adjusts the reference frame until a quadrature component of a current Park vector in the adjusted reference frame is equal to a predetermined value, whereby a synchronous reference is established. The synchronous frame is used to control a power converter. The floating frame controller can drive a synchronous machine without the use of rotor position sensors.

Transient performance of UPS system with synchronous-frame digital controller

Abstract: This paper proposes a voltage controlled voltage source type nonlinear regulator, based on the state variable approach, for the control of three-phase UPS inverters. The purposes are to improve dynamic response, incorporate the output LC filter as part of the output voltage control system and reduce the number of sensors. The design and analysis are based on the system state-space models, with state variable linearization and decoupling performed through on-line calculation. An output voltage estimator is proposed, using the instantaneous power as the basis for the algorithm, with data sampling executed only at the zero switching states, thereby eliminating the filter. In addition, a full-order load current observer is used, which makes the proposed control system load parameter insensitive, and results in fast transient response. The steady state and transient performance of the UPS system are evaluated. The dynamic response time is around 4 ms. Experimental results are obtained on a 4 kVA DSP controlled prototype UPS.

For prototype super-conducting magnetic energy storage (SMES) [voltage source convertor control scheme]

Abstract: In this paper, a synchronous frame based control method of voltage source converter (VSC) for superconducting magnetic energy storage (SMES) is presented. The model and the feedforward decoupling method are described. The design of the regulators is depicted in detail. Simulations and experiments are both demonstrate the studies.

Comparative analysis of shunt active filters in nonideal operating conditions

Abstract: Four widely used shunt active filters, implemented by means of a DSP, are compared in nonideal operating conditions. Filters based on the instantaneous reactive power theory, on the synchronous frame theory, on the active power estimation theory and on the voltage processing and supply current reaction (VPSC) are considered in nonideal conditions: the DSP delay is not negligible and the supply voltage is distorted and/or unbalanced. The comparison is based on analytic results and comparative simulations. The VPSC filter results the best choice in the considered operating conditions to overcome the nonideal supply conditions and the DSP implementation drawbacks.