共查询到17条相似文献，搜索用时 578 毫秒
1.
PWM逆变器载波方式的选择 总被引：1，自引：2，他引：1
In this paper the influence of different carrier waveforms upon the output characteristics of PWM inverter is described in detail. When a triangular carrier waveform is used in hard-switching PWM inverters, harmonics exist in the neighborhood of the output frequency of the inverter output voltage and current due to the dead time. The triangular carrier waveform used in soft-switching PWM inverter will cause difficulties in controlling resonance-trigger time, higher loss in the resonant circuit, and less utilization of the DC bus voltage. If a sawtooth carrier is used in hard-switching PWM inverter, there will be severe distortion in the current waveform. When sawtooth carriers with alternate positive and negative slopes are used in soft-switching PWM inverters, the resonancetrigger time is easy to control, and distortion in the output voltage and current caused by the dead time will not appear. 相似文献
2.
A new PWM converter based on soft-switching is introduced.The converter uses a minimum number of devices,and requires less switching operations than conventional techniques,Switching is realized solely in a ZVS)zero voltage switching)mode,therefore the loss is reduced and EMI(electromagnetic interference)is suppressed.The paper analyzes the operation of ZVS,and discusses the methods for maintaining a unit power factor and constant DC voltage.Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage.It also keeps the current sinusoidal,and ensures a constant output voltage. 相似文献
3.
A high speed column-parallel CDS/ADC circuit with nonlinearity compensation is proposed in this paper.The correlated double sampling (CDS) and analog-to-digital converter (ADC) functions are integrated in a threephase column-parallel circuit based on two floating gate inverters and switched-capacitor network.The conversion rate of traditional single-slope ADC is speeded up by dividing quantization to coarse step and fine step.A storage capacitor is used to store the result of coarse step and locate the section of ramp signal of fine step,which can reduce the clock step from 2 n to 2 (n/2+1).The floating gate inverters are implemented to reduce the power consumption.Its induced nonlinear offset is cancelled by introducing a compensation module to the input of inverter,which can equalize the coupling path in three phases of the proposed circuit.This circuit is designed and simulated for CMOS image sensor with 640×480 pixel array using Chartered 0.18μm process.Simulation results indicate that the resolution can reach 10-bit and the maximum frame rate can reach 200 frames/s with a main clock of 10MHz.The power consumption of this circuit is less than 36.5μW with a 3.3V power supply.The proposed CDS/ADC circuit is suitable for high resolution and high speed image sensors. 相似文献
4.
A speed-sensorless vector control system for induction machines （IMs）is presented, According to the vector control theory of IMs, the rotor flux is estimated based on a flux observer,and the speed is estimated through the method of q-axis rotor flux converging on zero with proportional integral regulator, A 0.75 kW,50 Hz,two-pole induction machine was used in the simulation and experimental verification, The simulation model was constructed in Matlab. A series of tests were performed in the field weakening region, for both no-load and loaded operation. The estimated speed tracks the actual speed well in the based speed region and field weakening region （ 1 per unit value to 4 per unit value）. The small estimation error of residual speed is due to the existence of slip. 相似文献
5.
In this paper, a vector regulating principle of the phase and amplitude control （ PAC ） method for three-phase grid-connected inverters is presented. To solve the problem of heavy inrush current and slow dynamic response when system starts up, the starting voltage prediction control and the current feed-forward control are proposed and used, which improve the dynamic performance of the system in the PAC. The experimental results carried out on a three-phase grid-connected inverter proved the validity of the proposed method. 相似文献
6.
In comparison with several zero-voltage transition (ZVT) inverter topologies,a double-PWM converter is presented using a simple ZVT topology.The rectifier and inverter of this double-PWM share a set of commutation circuit which can provide soft-switching for the power devices and the diodes.The commutation circuit consists of 1 auxiliary device,6 resonant inductors,and 12 diodes.Its topology is simpler than the conventional auxiliary resonant converter,leading to low loss and easy control.The control strategy and resonant working modes are analyzed.Experimental results show good performance of the system. 相似文献
7.
This paper presents a powerful application of genetic algorithm （GA） for the minimization of the total harmonic current distortion （THCD） in high-power induction motors fed by voltage source inverters, based on an approximate harmonic model. That is, having defined a desired fundamental output voltage, optimal pulse patterns （switching angles） are determined to produce the fundamental output voltage while minimizing the THCD. The complete results for the two cases of three and five switching instants in the first quarter period of pulse width modulation （PWM） waveform are presented. Presence of harmonics in the stator excitation leads to a pulsing-torque component. Considering the fact that if the pulsing-torques are at low frequencies, they can cause troublesome speed fluctuations, shaft fatigue, and unsatisfactory performance in the feedback control system, the 5th, 7th, 1 lth, and 13th current harmonics （in the case of five switching angles） are constrained at some pre-specified values, to mitigate the detrimental effects of low-frequency harmonics. At the same time, the THCD is optimized while the required fundamental output voltage is maintained. 相似文献
8.
Multi-frequency proportional-resonant （MFPR） current controller for PWM VSC under unbalanced supply conditions 总被引：1，自引：0，他引：1
HU Jia-bing HE Yi-kang 《浙江大学学报(A卷英文版)》2007,8(10):1527-1531
This letter presents a multi-frequency proportional-resonant （MFPR） current controller developed for PWM voltage source converter （VSC） under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSE The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance. 相似文献
9.
A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching （ZVS） PWM converter based on phase and amplitude control （PAC）, when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes. 相似文献
10.
The magamp （magnetic amplifier） is widely used in power supplies due to its low cost, simplicity and other advantages. This paper discusses a novel application of the magamp in switching power supplies, where the magamp is used to regulate pulse width modulation （PWM） instead of power signal in the main circuit. This method extends the application of the magamp in power supplies, and makes it possible to further regulate control signal when PWMs have been generated. Based on this applica- tion, a new current-sharing （CS） scheme using the magamp is proposed, which uses a modified inner loop CS structure. In this scheme PWMs are generated by one main controller, and CS is achieved by regulating PWMs using a magamp in each module. Compared with traditional application of the magamp, the new CS scheme can be used in most topologies and only requires magamps of low power capacity. Then a test circuit of parallel power supply is developed, in which CS is achieved by a PWM regulator with the magamp. The proposed scheme is also used to upgrade an electroplate power to make it capable of paralleling supplies. Experimental results show that the proposed scheme has good CS performance. 相似文献
11.
In this paper, a new soft-switching inverter using a minimum number of devices, and a new PWM (pulse-width modulation) method
suitable for 3-phase soft-switching inverters are proposed. The circuit is used as an interface between the DC supply and
the conventional voltage source of a PWM inverter. The number of switching operations can be reduced by using the PWM strategy.
Increasing the amplitude of the fundamental component contained in the output waveform results in an effective utilization
of the DC supply, a reduction of nominated capacity of the inverter elements, and a reduction of switching loss in the switching
devices.
Supported by National Natural Science Foundation of China (59977012) 相似文献
12.
多输入DC-DC变换器由于其独特的电路拓扑结构，在结合利用诸如太阳电池，燃料电池，风力发电等电源容量及电压级别各不相同的无公害能源方面，具有很好的应用前景。但其功率开关器件在硬开关状态下动作，由此产生的功率损耗及噪音污染成为问题。本文对多输入变换嚣中最常用的2输入升降压型DC-DC变换嚣的部分共振特性进行了探讨，在储能电感处于非连续电流工作状态下，以极其简单的电路方式，实现半导体功率开关的零电压零电流导通，输出整流二极管的振荡电压的消除及零电流关断，从而改善了变换器的转换效率并降低了其所产生的噪音。 相似文献
13.
Cascade multilevel inverters have been developed for electric utility applications. A cascade M-level inverter consists of (M-1)/2 H-bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi-pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer-less connection to medium- and high-voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi-pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters. 相似文献
14.
Applications of cascade multilevel inverters 总被引：1，自引：0，他引：1
INTRODUCTIONRecently,flexiblealternatingcurrenttrans missionsystems (FACTS) ,custompower,andpowerqualityhavebeenhottopicsbecauseoftheincreasingpowerdemand ,thewidespreaduseofnon linearelectronicequipment,andthehigherpowerqualityrequirementsofsensitiveload… 相似文献
15.
方菁 《宁波职业技术学院学报》2010,14(2):19-22,39
针对传统的直接转矩控制中存在转矩、定子磁链波动大的问题,提出了一种结合空间矢量调制的模糊神经网络直接转矩控制方法。该方法运用模糊神经网络得到期望的任意相位空间电压矢量,再结合空间矢量调制直接对逆变器的开关状态进行控制,以达到减小转矩、定子磁链波动的目的。最后以TMS320F240为核心搭建了直接转矩控制系统,通过采集实验数据分析结果表明,直接转矩控制系统与传统的直接转矩控制系统相比,磁链和转矩波动明显减少,并且保持了转矩和速度的响应速度。 相似文献
16.
单相光伏并网逆变系统的设计 总被引：1，自引：1，他引：0
介绍了一种宽电压输入范围的单相光伏并网逆变系统的设计。在光伏并网发电中,为了实现并网,直流侧电压必须高于电网电压幅值,这就对光伏阵列的输出电压有所要求。为了满足复杂的现场要求,该系统前端有一个直流升压电路,扩大了光伏阵列输出直流电压的范围。该系统由DSP控制,通过电压、电流测量电路和电网电压过零点检测电路使并网电流和电网电压同频同相位,并将指令电流和并网电流的偏差通过PID控制算法使指令电流实时地跟随指令电流变化。另外,该系统有相应的通信接口,具有通信功能和扩展功能。 相似文献
17.
To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control (DTC) of induction machines, the factors of influence torque variation are examined. A new torque ripple minimization algorithm is proposed. The novel method eradicated the torque ripple by imposing the required stator voltage vector in each control cycle. The M and T axial components of the stator voltage are accomplished by measuring the stator flux error and the expected incremental value of the torque at every sampling time. The maximum angle rotation allowed is obtained. Experimental results showed that the proposed method combined with the space vector pulse width modulation(SVPWM) could be implemented in most existing digital drive controllers, offering high performance in both steady and transient states of the induction drives at full speed range. The result of the present work imphes that torque fluctuation could be eliminated by imposing proper stator voltage, and the proposed scheme could not only maintain constant switching frequency for the inverter, but also solve the heating problem and current harmonics in traditional induction motor drives. 相似文献