共查询到20条相似文献,搜索用时 31 毫秒
1.
Zhihong Ye Boroyevich D. Jae-Young Choi Lee F.C. 《Power Electronics, IEEE Transactions on》2002,17(5):609-615
One unique feature in parallel three-phase converters is a potential zero-sequence circulating current. To avoid the circulating current, most present technology uses an isolation approach, such as transformers or separate power supplies. This paper proposes a parallel system where individual converters connect both AC and DC sides directly without additional passive components to reduce size and cost of the overall parallel system. In this case, the control of the circulating current becomes an important objective in the converter design. This paper: (1) develops an averaged model of the parallel converters based on a phase-leg averaging technique; (2) a zero-sequence model is then developed to predict the dynamics of the zero-sequence current; (3) based on the zero-sequence model, this paper introduces a new control variable, which is associated with space-vector modulation; (4) a strong zero-sequence current control loop is designed to suppress the circulating current; and (5) simulation and experimental results validate the developed model and the proposed control scheme. 相似文献
2.
《Industrial Electronics, IEEE Transactions on》2009,56(8):3004-3012
3.
《Power Electronics, IEEE Transactions on》2009,24(5):1330-1339
4.
We describe three nonlinear control schemes for a parallel three-phase boost rectifier consisting of two modules. The basic idea, however, can be extended to a system with N modules. All of the control schemes are developed in a synchronous frame. Moreover, each of the closed-loop power-converter modules operates asynchronously without any communication with the other module. Based on the dynamical equations of the parallel converter, we find that independent control of both of the modules on the DQ axes is not necessary and possible. Consequently, we develop control schemes that stabilize the dq axes and limit the zero-axis disturbance by preventing the flow of the pure zero-sequence current. One of the control schemes is developed purely in the discrete domain. It combines the space-vector modulation scheme with a variable-structure control, thereby keeping the switching frequency constant and achieving satisfactory dynamic performance. The performances of the other control schemes are also satisfactory. 相似文献
5.
Modeling and Coordinate Control of Circulating Currents in Parallel Three-Phase Boost Rectifiers 总被引:1,自引:0,他引:1
Ching-Tsai Pan Yi-Hung Liao 《Industrial Electronics, IEEE Transactions on》2007,54(2):825-838
In this paper, definition of the circulating currents of multiphase paralleled converters is first presented, and the circulating-current-generating mechanism is clearly explained. Thus, based on this definition, an averaged model of the circulating current is proposed. It is seen from this model that the circulating current consists of not only the zero-sequence but also the nonzero-sequence components. The governing differential equation also shows explicitly the relation between the circulating currents and the affecting factors such as different pulse width-modulation strategies. With this understanding, a simple coordinate control is then presented to reduce the circulating current. The phenomenon of the intrinsic circulating current is also explained. Furthermore, a prototype system is constructed, and the proposed control is implemented using TMS320F2812 DSP. Both simulation and experimental results verify the validity of the proposed theory and control 相似文献
6.
Shunt active power filters are connected in parallel with the electricity supply network. If the AC mains has a neutral conductor, it is desirable to compensate the mains harmonic currents zero-sequence components. This can be achieved with a four-wire pulsewidth modulation voltage converter connected to the AC mains. In this case, the three-phase and the neutral AC currents must be controlled. A generalization of the space-vector-based current controller in the αβo coordinate system is presented in this paper. With this current controller, all the current harmonic systems of positive, negative, and zero sequence can be injected by the converter and, thus, compensated on the AC mains. The system is also useful to compensate unbalanced currents of fundamental frequency. A useful benefit of this system is that it is possible to control the converter four-wire currents with equal hysteresis errors. Simulation and experimental results are presented 相似文献
7.
Jia Wu Lee F.C. Boroyevich D. Heping Dai Kun Xing Dengming Peng 《Power Electronics, IEEE Transactions on》2003,18(6):1302-1308
This paper presents a 100 kW three-phase pulse-width modulated (PWM) boost rectifier that serves as the front-end power source for a DC distributed power system. A zero current transition (ZCT) soft-switching technique is applied to achieve greater performance in this high-power converter. This ZCT soft-switching technique assists the turn-on as well as the turn-off of the main and auxiliary insulated gate bipolar transistor (IGBT) switches. An issue about the implementation of the ZCT soft-switching technique in three-phase applications is discussed. A space vector modulation (SVM) scheme suitable for high power applications with high performance is identified. Experimental results demonstrate that high performance is achieved, in terms of wide control bandwidth, low total harmonic distortion (THD), unity power factor and high efficiency. 相似文献
8.
Pulsewidth modulated (PWM) current-source rectifiers (CSR), among other alternatives, offer marked improvements over thyristor line-commutated rectifiers as a source of variable DC power. Advantages include reduced line current harmonic distortion and complete displacement power factor control, including unity displacement power factor operation. However, due to nonlinearities of the PWM-CSR model, their control has usually been carried out using direct line current control in a three-phase stationary frame (abc). This paper proposes the application of a nonlinear control technique that introduces more flexibility in the control of the rectifier and results in a more straightforward approach to controller design. The proposed technique is based on a nonlinear state variable feedback approach in the rotating frame (dq). The approach allows the independent control of the two components of the line current (active and reactive) with the same dynamic performance, regardless of the operating point. The control strategy also eliminates the need for input damping resistors and rejects the effect of supply voltage variations. Furthermore, a space vector modulation (SVM) technique is used to maximize the supply voltage utilization. This paper includes a complete formulation of the system equations and a controller design procedure. Experimental results on a 2 kVA digital-signal-processor-controlled prototype confirm the validity of theoretical considerations 相似文献
9.
Keliang Zhou Danwei Wang 《Industrial Electronics, IEEE Transactions on》2002,49(1):186-196
This paper comprehensively analyzes the relationship between space-vector modulation and three-phase carrier-based pulse width modulation (PWM). The relationships involved, such as the relationship between modulation signals (including zero-sequence component and fundamental components) and space vectors, the relationship between the modulation signals and the space-vector sectors, the relationship between the switching pattern of space-vector modulation and the type of carrier, and the relationship between the distribution of zero vectors and different zero-sequence signal are systematically established. All the relationships provide a bidirectional bridge for the transformation between carrier-based PWM modulators and space-vector modulation modulators. It is shown that all the drawn conclusions are independent of the load type. Furthermore, the implementations of both space-vector modulation and carrier-based PWM in a closed-loop feedback converter are discussed 相似文献
10.
Three-Dimensional Feedforward Space Vector Modulation Applied to Multilevel Diode-Clamped Converters
《Industrial Electronics, IEEE Transactions on》2009,56(1):101-109
Simplified space vector modulation (SVM) techniques for multilevel converters are being developed to improve factors such as the computational cost, number of commutations, and voltage distortion. The feedforward SVM presented in this paper takes into account the actual DC capacitor voltage unbalance of the multilevel power converter. The resulting technique is a low-cost generalized feedforward 3-D SVM method and is particularized for three-phase multilevel diode-clamped converters. This new modulation technique can be applied to topologies where the gamma component may not be zero. The computational cost of the proposed method is similar to those of comparable methods, and it is independent of the number of levels of the power converter. Experimental results using a three-level diode-clamped converter are presented to validate the proposed modulation technique. 相似文献
11.
A three-phase AC/DC converter based on isolated Cuk topology feeding an inductive load is presented. The main goal is to get a compact, highly stable current source to feed an electromagnet. A high power factor is achieved, at constant duty-cycle and switching frequency, by discontinuous input current mode operation. The converter presents a linear relationship between the duty-cycle and the output current, making it easier to design the control system. Additionally the voltage stress on the power transistor is constant and does not depend on the duty-cycle. An auxiliary circuit allows zero voltage turn-off while limiting the over-voltage on the switch produced by the transformer leakage inductance. Pulse-width modulation (PWM) control is used to reduce sensitivity to line disturbances and to eliminate the 300-Hz ripple on the output current. Experimental measurements taken on a 400-W prototype confirm theoretical forecasts 相似文献
12.
The continuous, discontinuous pulse-width modulation (PWM) schemes and a novel space vector modulation methodology are proposed in this paper for four-leg dc-ac inverters. Using a space vector definition that includes the zero sequence voltage component and partitioning the feasible sixteen modes into two separate sets - one set having zero sequence voltages with positive magnitudes and the other set with negative magnitudes - the novel space vector implementation technique is determined as also the discontinuous carrier based PWM scheme. For the continuous carrier based PWM scheme, the indeterminate defining output voltage equations expressed in terms of the existence functions of the switching devices are solved using an optimization technique. The modulation schemes determined are shown by experimental results to synthesis any desirable balanced or unbalanced three-phase voltage sets when operating in the linear modulation region. 相似文献
13.
Fang Zheng Peng Ott G.W. Jr. Adams D.J. 《Power Electronics, IEEE Transactions on》1998,13(6):1174-1181
This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented 相似文献
14.
针对脉宽调制(PWM)逆变器,在研究逆变电源电压矢量的基础上,将空间矢量脉宽调制(SVPWM)技术应用于三相和单相PWM逆变电源,分别给出了三相和单相SVPWM的数字信号处理(DSP)算法,给出了一种开关模式优化的单相SVPWM算法,导出了三相和单相SVPWM基于载波调制的调制波形式以及零序信号形式,指出载波零序信号在本质上对应着逆变器零电压矢量作用时间分配与分布,论证了SVPWM与载波PWM的统一,实验结果验证了SVPWM算法的有效性. 相似文献
15.
Optimal Use of Zero Vectors for Minimizing the Output Current Distortion in Matrix Converters 总被引:1,自引:0,他引:1
《Industrial Electronics, IEEE Transactions on》2009,56(2):326-336
16.
A two-level four-leg inverter has been developed for the three-phase four-wire power quality compensators. When it is applied to medium and large capacity compensators, the voltage stress across each switch is so high that the corresponding dv/dt causes large electromagnetic interference. The multilevel voltage source inverter topologies are good substitutes, since they can reduce voltage stress and improves output harmonic contents. The existing three-level neutral point clamped (NPC) inverter in three-phase three-wire systems can be used in three-phase four-wire systems also, because the split dc capacitors provide a neutral connection. This paper presents a comparison study between the three-level four-leg NPC inverter and the three-level NPC inverter. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-level NPC inverter in a three-phase four-wire system. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. Both simulation and experimental results are given to show the effectiveness of the proposed 3DSVM control strategy. Comparisons between the 3DSVM and the 3-D hysteresis control strategy are also achieved. 相似文献
17.
The complete DC characteristics of three-phase modular power-factor-correction (PFC) converters using single-phase pulsewidth modulation (PWM) DC-to-DC converter modules for high-power applications are studied. Using circuit averaging, the converter input and output quantities are determined numerically. Both the continuous and discontinuous output current modes of operation (CCM and DCM) are studied in detail. Near-unity power factor can be achieved with the converter modules operating in the DCM. An averaged model was used to study and determine the boundaries between DCM and CCM over the full period of the three-phase input voltage. It is found that high power factor is inherent in the converter system provided that the converters are operated in the DCM and the voltage conversion ratio is selected properly. The criteria for obtaining high power factor are analyzed and the optimal circuit parameters are determined to obtain the best achievable power factor. Both simulations and experimental results from a 1.5-kW prototype using full-bridge converter modules have confirmed the analysis 相似文献
18.
Zhang R. Prasad V.H. Boroyevich D. Lee F.C. 《Power Electronics, IEEE Transactions on》2002,17(3):314-326
Four-leg voltage-source converters can effectively provide the neutral connection in three-phase four-wire systems. They can be used in inverter, rectifier, and active filter applications to handle the neutral current caused by the unbalanced and/or nonlinear load or unbalanced source. In this paper, three-dimensional (3-D) space vector modulation (SVM) schemes are proposed for controlling the four-leg voltage-source converters. Important issues for 3-D SVM, such as definition of 3-D vectors, identification of adjacent switching vectors in the 3-D space, and switching vector sequencing schemes and comparisons are addressed. The proposed 3-D SVM is a superset of the traditional two-dimensional (2-D) SVM, and thus it inherits all the merits of the traditional 2-D SVM. A 100 kW 5 kHz four-leg inverter and a 20 kHz four-leg rectifier prototypes are built and controlled by the proposed 3-D SVM. Experimental results are presented to validate the effectiveness of the 3-D SVM 相似文献
19.
DC-link current harmonics are the predominant factor to be considered for dimensioning dc capacitors in three-phase pulsewidth-modulation (PWM) voltage-source converters. In this paper, an analysis of the dc-link current harmonics applying a double Fourier series is derived. The analytical results for the dc-link current spectra of continuous and discontinuous PWMs are presented and compared with measurement results taken from a converter test setup. A good match between theoretically expected and actually obtained experimental results can be stated. Moreover, characteristic differences between the investigated modulation strategies regarding their dc-link current spectra become evident. 相似文献