Direct Power Control Strategy of PWM Rectifier Based on Improved Virtual Flux-Linkage Observer

Abstract

In order to achieve the low cost and high performance control of three-phase PWM rectifier, a direct power control (DPC) strategy based on a new-style virtual flux-linkage observer is proposed. The model of three-phase PWM rectifier and the principle of virtual flux-linkage vector control are introduced firstly. Then, in order to avoid the effect of integral initial value and cumulative deviation, three first-order low-pass filters are cascaded to replace the pure integral link; an improved virtual flux-linkage observer of threephase power grid is presented. From the observed virtual flux-linkage, the voltage and instantaneous power of three-phase power grid are online estimated. On this basis, the power grid voltage sensorless direct power control system of three-phase PWM rectifier is designed. Simulation results have shown that, both in the rectifying state and in the inverting state, the power grid side current and the DC side voltage of three-phase PWM rectifier all can be effectively controlled; the high power factor operation of three-phase PWM rectifier is realized.

An advanced virtual flux integrated multifold table‐based direct power control with delay compensation for active front‐end rectifiers

“…So the system output (controlled variable) "U dc " can be controlled by the input current. Hence the transfer function of the plant can be obtained by taking the ratio as shown in Equation (11).…”

“…The estimations performed using this method are found to be accurate even during the nonideal grid conditions like unbalanced and distorted phase voltages. The dynamic performance of the flux estimation technique is improved using two cascaded second‐order LPF 10 and third‐order LPF 11 . On the counter side, the use of higher‐order LPF increases the complexity of the tuning process.…”

“…The dynamic performance of the flux estimation technique is improved using two cascaded second-order LPF 10 and third-order LPF. 11 On the counter side, the use of higher-order LPF increases the complexity of the tuning process.…”

Improved virtual flux direct power control of three phase PWM rectifier using SOGI-FLL estimator under disturbed voltage conditions

“…Direct power control without line voltage sensors is investigated. This sensorless method is based on definition and estimation virtual flux ,The three-phase rectifier can be seen as a virtual AC motor, its virtual flux-linkage can be used to estimate the voltage of rectifier , in the conventional virtual flux (VF) estimation of three-phase rectifier,But in the conventional (VF) estimation, there exists a pure integral link, and then the estimation process of (VF) is automatically affected by the initial value and the cumulative deviation of the integrator [11][12][13][14][15][16][17]. For solving pure integration problems, more researchers are focusing on replacing the pure integrator by using low-pass filters (LPFs), in which case the pure integrator initial value problem can be solved with success [11], [15][16][17] but, the problem of amplitude and phase deviation is caused.…”

“…For solving pure integration problems, more researchers are focusing on replacing the pure integrator by using low-pass filters (LPFs), in which case the pure integrator initial value problem can be solved with success [11], [15][16][17] but, the problem of amplitude and phase deviation is caused. In order to dominate the influence of its problems, several authors propose methods of estimation of the (VF)], diverse authors propose technique of estimation of the (VF) such as [12], [18]. In summary, the key to a successful operation of the DPC utilizing grid (VF) estimation is dependent on the effectiveness of the (VF) estimation procedure and the selection of the converter switching states [19].…”