共查询到20条相似文献,搜索用时 15 毫秒
1.
Hong-Seok Song Kwanghee Nam 《Industrial Electronics, IEEE Transactions on》1999,46(5):953-959
Voltage unbalance in a three-phase system causes performance deterioration of PWM power converters by producing 120 Hz voltage ripples in the DC link and by increasing the reactive power. To eliminate the DC link voltage ripple and the DC component of the reactive power, both positive- and negative-sequence currents should be controlled simultaneously, according to the paper by Rioual et al (1996). The authors used two synchronous reference frames: a positive-sequence current regulated by a proportional integral (PI) controller in a positive synchronous reference frame (SRF); and a negative-sequence current regulated by a PI controller in a negative SRF. In the positive SRF, which rotates counterclockwise, the positive sequence appears as DC, while the negative sequence appears as 120 Hz. In contrast, in the negative SRF, which rotates clockwise, the negative sequence appears as DC, while the positive sequence appears as 120 Hz. By deleting 120 Hz components using a notch filter in each SRF, one can measure positive- and negative-sequence currents separately, and use them for constructing two feedback controllers. Since the negative-sequence current is also controlled in its own SRF by a DC command, this approach yields better performance without increasing the control gain. Note that, since the controller is implemented by a software routine in the digital signal professor chip, using two SRFs does not require additional hardware. The authors demonstrated the effectiveness of the proposed control scheme by using computer simulation and experiments 相似文献
2.
Ji Yanchao Shan Mingwei 《Power Electronics, IEEE Transactions on》1999,14(2):233-245
This paper proposes a novel three-phase AC/DC converter without a front-end filter. Because an adjustable triangular-wave pulsewidth modulation (PWM) (ATPWM) technique is adopted, not only is a front-end filter located after the three-phase rectifier is omitted, but also the size of the input AC filter and the output DC filter are reduced. In addition, this AC/DC converter has many advantages such as simpler structure, higher reliability, and better output waveform. The principle of operation, harmonics elimination, and feedback control of the novel AC/DC topology are elaborated. A thorough analysis on its performance under an unbalanced system is presented. Finally, the theoretical analysis is proved to be correct by simulations and experiments 相似文献
3.
The three-phase pulsewidth modulation (PWM) AC/DC voltage-source converter with the control laws proposed so far is not only unstable against large-signal disturbances, but also has the problem that its stability depends on the circuit parameters such as the DC-output capacitance. This paper describes a new control law based on Lyapunov's stability theory. It is shown that the converter can be stabilized globally for handling large-signal disturbances. The resulting closed-loop system not only guarantees a sufficient stability region (independent of the circuit parameters) in the state space, but also exhibits good transient response both in the rectifying and regenerating modes. Also, a new simulation technique is introduced which increases the speed of the simulation process considerably. Computer simulations are presented to confirm the effectiveness of the proposed control strategy and the validity of the simulation technique. Experimental results are also presented to verify the theoretical and simulation studies 相似文献
4.
Hong-Seok Song In-Won Joo Kwanghee Nam 《Industrial Electronics, IEEE Transactions on》2003,50(6):1238-1245
A source voltage sensorless estimation scheme is proposed for a pulsewidth-modulation (PWM) rectifier in unbalanced circumstances. The negative sequence is accompanied by the unbalance among phases, and acts as an ac disturbance to a normal-mode estimator and controller. Hence, without considering voltage unbalance, a PWM rectifier yields a voltage ripple in the dc-link voltage and large reactive currents. With the proposed sensorless scheme, both positive and negative components are estimated separately by using a full- (or reduced-) order estimator. The feasibility of the proposed sensorless scheme is confirmed through computer simulation and experiment. 相似文献
5.
Dong-Choon Lee Dae-Sik Lim 《Power Electronics, IEEE Transactions on》2002,17(6):883-890
In this paper, a novel control scheme of three-phase PWM rectifiers eliminating both the AC input voltage and current sensors is proposed. The phase angle and the magnitude of the source voltage are estimated by controlling the deviation between the rectifier current and its model current to be zero. The input currents can be reconstructed from switching states of the PWM rectifier and the measured DC link currents. To eliminate the calculation time delay effect of the microprocessor, the currents ahead one sampling period are estimated by a state observer and then are used for feedback control. The proposed control scheme reduces the system cost and improves its reliability. The feasibility of the proposed AC sensorless technique for three-phase PWM rectifiers has been verified through experiments using a high performance DSP chip. 相似文献
6.
In this paper, an equivalent DC duty cycle for the generalized zero-voltage space vectors is proposed such that control of the three-phase AC part and the DC part of the converter circuit can be integrated to achieve the ideal characteristic of single-stage step-up/down AC/DC converter. Depending upon how many modes are chosen and which class of generalized zero-voltage space vectors is selected to increase the equivalent DC duty cycle, different control strategies can be obtained. It is seen that not only the control of the six switches is simplified but also the deadtime circuit for avoiding short circuit of the same arm can be eliminated for the proposed converter. In addition, some guidelines for selecting the LC parameters are described briefly and experimental results given for verifying the validity of the proposed converter 相似文献
7.
Yip S.C. Qiu D.Y. Henry Shu-Hung Chung Hui S.Y.R. 《Power Electronics, IEEE Transactions on》2003,18(6):1346-1355
A novel voltage sensorless control technique for a bidirectional AC/DC converter is presented. Only a single current sensor that measures the inductor current is needed in the whole system. The sensed inductor current is used for two functions. The first one is for shaping the current waveform at the AC side and the second one is for deriving the inductor voltage by determining the rate of change of the inductor current. The AC-side and DC-side voltages, which are used for AC current synchronization and DC voltage regulation, respectively, are obtained by extracting the envelopes of the derived inductor voltage. Apart from reducing the number of sensing elements, the proposed method has additional advantages of: (1) inherent electrical isolation and reducing noise coupling between the power circuit and the controller; (2) wide operating range. Design criteria for the differentiator and the envelope detector circuit has been described. The applicability of the proposed method is verified with the experimental results of a laboratory prototype. 相似文献
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Abnormal harmonics of significant magnitude are generated at the output and input terminals of a PWM (pulse-width-modulated) AC-to-DC power converter under unbalanced operating conditions. A new control strategy is presented to selectively cancel the generated lower-order abnormal harmonics at the output and input terminals and thereby to preserve the high-performance features of a PWM AC-to-DC power converter. The proposed technique essentially involves computing the sequence components of the unbalanced input supply and suitably counter-unbalances the PWM gating signals of the power converter switches to cancel the generated abnormal harmonics. The technique is essentially a feedforward approach and is suitable for higher-power GTO (gate turn-off thyristor) type PWM AC-to-DC power converters. A procedure for implementing this technique in real time is discussed. Selected results are verified experimentally on a prototype PWM AC-to-DC power converter 相似文献
10.
A three-phase ZVS PWM DC/DC converter with asymmetrical duty cycle associated with a three-phase version of the hybridge rectifier 总被引:1,自引:0,他引:1
This paper proposes the use of a three-phase version of the hybridge rectifier in the three-phase zero-voltage switch (ZVS) DC/DC converter with asymmetrical duty cycle. The use of this new rectifier improves the efficiency of the converter because only three diodes are responsible for the conduction losses in the secondary side. The current in the secondary side of the transformer is half the output current. In addition to this, all the advantages of the three-phase DC/DC converter, i.e., the increased frequency of the output and input currents, the improved distribution of the losses, as well as the soft commutation for a wide load range, are preserved. Therefore, the resulting topology is capable of achieving high efficiency and high power density at high power levels. The theoretical analysis, simulation, and experimental results obtained from a 6-kW prototype, and also a comparison of the efficiency of this converter with the full-bridge rectifier are presented. 相似文献
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12.
Active filtering function of three-phase PWM boost rectifier under different line voltage conditions 总被引:1,自引:0,他引:1
Cichowlas M. Malinowski M. Kazmierkowski M.P. Sobczuk D.L. Rodriguez P. Pou J. 《Industrial Electronics, IEEE Transactions on》2005,52(2):410-419
Slight hardware and algorithm modifications as well as a higher power ratio of a three-phase pulsewidth-modulation (PWM) rectifier make compensation of neighboring nonlinear power load possible. The active filtering function enlarges the functionality of PWM rectifiers, which decreases the cost of additional installation of compensating equipment. It gives a chance to fulfill both shunt active filter (SAF) and PWM rectifier tasks in a multidrive system by one advanced converter. Thanks to the idea of virtual flux, the direct power control space-vector-modulated (DPC-SVM) and new synchronous double reference frame phase-locked loop approach, the control system is resistant to a majority of line voltage disturbances. This assures proper operation of the system for abnormal and failure grid conditions. Simulation and experimental results have proven excellent performance and verify the validity of the proposed system. 相似文献
13.
Blaabjerg F. Casadei D. Klumpner C. Matteini M. 《Industrial Electronics, IEEE Transactions on》2002,49(2):289-296
In this paper, the input current performance of matrix converters is analyzed, especially with reference to the operating conditions determined by unbalanced supply voltages. The space-vector modulation (SVM) technique is utilized to calculate the duty cycles of the active voltage vectors that must be applied, in each switching cycle period, in order to satisfy the input and output requirements. A detailed theoretical analysis of the input current harmonic content under unbalanced input voltage conditions is presented for two different current modulation strategies. On the basis of numerical simulations as well as measurements on a laboratory prototype setup, the strategies' performance are compared and the validity of the theoretical investigation confirmed. It is concluded that, when the input voltages are unbalanced to a significant extent, a dynamic input current modulation strategy has to be preferred, since a lower harmonic line current distortion will appear 相似文献
14.
An approximate procedure for on-line computing the loss-optimal values of the switching angles in a class of pulse width modulated converters is presented. The proposed technique is independent of the constants of the circuit and allows one to obtain a given power in the DC load with minimum loss of energy in the AC and DC filters. This corresponds to have a quasisinusoidal supply current with minimum ripple on the output load. Simulation and experimental results confirm the practical feasibility of the method 相似文献
15.
Lon-Kou Chang Hsing-Fu Liu 《Industrial Electronics, IEEE Transactions on》2005,52(1):125-131
This work presents a novel simple forward AC/DC converter with harmonic current correction and fast output voltage regulation. In the proposed AC/DC converter, a transformer incorporating reset winding provides two main advantages. First, the bulk inductor used in the conventional boost-based power-factor-correction cell is omitted in the proposed converter, allowing significant volume and weight of magnetic material to be saved. Second, the voltage across the bulk capacitor can be held under 450 V by adjusting the transformer winding ratio, despite the converter operating in a wide range of input voltages (90/spl sim/265 V/AC). This new converter complies with IEC 61000-3-2 under a load range of 200 W and has fast output voltage regulation. 相似文献
16.
Lagrangian modeling and passivity-based control of three-phase AC/DC voltage-source converters 总被引:2,自引:0,他引:2
Tzann-Shin Lee 《Industrial Electronics, IEEE Transactions on》2004,51(4):892-902
In this paper, we investigate the dc-bus voltage regulation problem for a three-phase boost-type pulsewidth-modulated (PWM) ac/dc converter using passivity-based control theory of Euler-Lagrange (EL) systems. The three-phase PWM ac/dc converters modeled in the a-b-c reference frame are first shown to be EL systems whose EL parameters are explicitly identified. The energy-dissipative properties of this model are fully retained under the d-q-axis transformation. Based on the transformed d-q EL model, passivity-based controllers are then synthesized using the techniques of energy shaping and damping injection. Two possible passivity-based feedback designs are discussed, leading to a feasible dynamic current-loop controller. Motivated from the usual power electronics control schemes and the study of Lee, the internal dc-bus voltage dynamics are regulated via an outer loop proportional plus integral (PI) controller cascaded to the d-axis current loop. Nonlinear PI control results of Desoer and Lin are applied to theoretically validate the proposed outer loop control scheme. The PWM ac/dc converter controlled by the proposed passivity-based current control scheme with outer loop PI compensation has the features of enhanced robustness under model uncertainties, decoupled current-loop dynamics, guaranteed zero steady-state error, and asymptotic rejection of constant load disturbance. Experimental results on a 1.5-kVA PC-based controlled prototype provide verification of these salient features. The experimental responses of a classical linear PI scheme are also included for comparative study. 相似文献
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The advent of high-power, high-frequency, solid-state switches with fast gate turn-off capabilities suggests that pulse-width-modulated (PWM) techniques can soon be introduced into HVDC (high-voltage direct-current) applications. A boost-type PWM converter with voltage angle lock control that is tailored to the utility environment is described. Experimental test results for 1 kVA models show that the advantages are substantial 相似文献
19.
Ching-Tsai Pan Jenn-Jong Shieh 《Industrial Electronics, IEEE Transactions on》1998,45(4):530-543
In this paper, a basic closed-form duty cycle control law is first derived for the proposed AC/DC converter to achieve clean sinusoidal input current, adjustable DC voltage, controllable power factor and bidirectional power flow capability, and fixed switching frequency, without using any current sensor. Then, a second dead-band scheme is derived from the previous basic form to achieve the same function and to reduce switching loss and thermal stress. Similarly, a four-switch scheme is also derived to provide a new operation mode to enhance the reliability of the converter. Modified control laws of the above family are also considered to handle the effect of unbalanced input voltage. It is very interesting to see that a unified theory can be used to give the above family of duty cycle control laws under both balanced and unbalanced input voltage. Some simulation and experimental results are presented for verification 相似文献
20.
Fernandez A. Sebastian J. Alou P. Cobos J.A. Rascon M. 《Power Electronics, IEEE Transactions on》2003,18(4):966-974
The aim of this paper is to study the performance of an AC/DC converter with low output voltage and low input current harmonic content. In order to obtain low output voltages with a high efficiency, synchronous rectification is mandatory. When the output voltage is low, it is very difficult to use self-driven synchronous rectification and additional windings are used to properly drive the metal oxide semiconductor field effect transmitters (MOSFETs). Besides this, IEC 1000-3-2 regulations impose low input current harmonic contents for power levels higher than 75 W. In this paper, a recently proposed synchronous rectification scheme is combined with a modified input current shaper to design a 100 W, 3.3 V AC/DC converter that complies with IEC 1000-3-2 regulations. The efficiency obtained in the prototype was very high for this application (86%) and both the size increase and the cost increase were quite low in comparison with the original topology with no synchronous rectification and no IEC 1000-3-2 compliance. 相似文献