【作者】 曹太强；

【导师】 许建平；

【作者基本信息】 西南交通大学 ， 电力电子与电力传动， 2011， 博士

【摘要】 针对光伏并网发电系统的逆变器并联技术、并网的最大功率跟踪控制、系统的稳定性和可靠性、不平衡负载对光伏系统中三相逆变器输出电压不对称的影响等关键问题,深入研究了光伏逆变器并联控制方法、并网最大功率跟踪控制技术、光伏发电系统谐波抑制以及三相不平衡负载控制方法等,提出了相应的解决方案。论文的主要研究工作和成果包括：(1)提出了一种高性能逆变器并联控制方法：以现场可编程门阵列(Field Programmable Gate Array, FPGA)产生各并联逆变器的正弦脉冲宽度调制(Sinusoidal Pulse Width Modulation, SPWM)波频率和相位,以确保输出电压绝对同步,用单相交流电压、电流构造三相交流电压、电流。根据瞬时无功理论计算方法把逆变器输出交流电流变换成两相瞬时电流分量,再经同步d-q变换得到有功电流和无功电流,最后用数字信号处理器(Digital Signal Processor, DSP)控制两台逆变器并联的瞬时有功、无功功率相等,从而使两台逆变器输出的电流均流。实验结果表明,该控制方法能达到各逆变器功率均分、逆变电源之间无环流的目的。(2)提出了一种光伏并网系统的最大功率传输方法,其控制思想是：在DC/DC变换器中用增量电导法的单周期功率扰动控制策略实现光伏电池最大功率跟踪；在DC/AC并网逆变器中用光伏电池最大功率输出时的最大直流电流作为并网逆变器输出交流电流反馈控制的瞬时参考电流的峰值,以电网电压的相位和频率作为瞬时交流参考电流的相位和频率,对该瞬时交流电流与并网交流电流的差进行PI控制,为确保并网逆变器的稳定性和可靠性；同时还引入了电网电压前馈和滤波器电容电流反馈控制。详细分析了并网控制系统的工作原理和控制策略,并用Matlab/Simulink对光伏系统进行仿真验证,验证了以上控制策略的可行性。(3)设计了一种新型无源三相△-带通滤波器,抑制大功率高频开关器件组成的光伏发电系统运行过程中产生的谐波成分。理论分析、仿真和实验研究结果表明,该滤波器能有效抑制光伏发电系统的3-19次等谐波(谐波总含量从31.5%减小到3.1%),提高了系统的功率因数和设备利用率,减小了线路耗损和电压损失,保证了光伏发电系统稳定可靠运行,提高了光伏发电系统供电的电能质量。(4)提出了一种三相逆变电源的输出电压分相控制方法,通过分别对三相逆变器输出线电压的控制,实现三相电压的平衡。三相逆变器中,传统的对称分量法是根据叠加原理对三相逆变器输出电压的正、负、零序分量分别进行补偿,以维持三相电压的平衡,它存在运算量大、实时性差、控制困难、效果不理想等缺点。理论分析、仿真和实验结果表明,本文所提出的方法简单、易实现,能够使三相最大不平衡度(A相额定负载、B相200%负载、C相空载)从传统的5.49%降到1%左右,有效地补偿因不平衡负载引起的逆变器输出电压畸变,从而保证逆变器在带任意不平衡负载时仍能维持三相逆变器的输出电压平衡。更多还原

【Abstract】 There exist many key problems in the development of photovoltaic power generation (PVPG) system and power-control of a grid-connected PVPG system, such as the parallel inverter technology of a grid-connected PVPG system, the maximum power track and control of a grid-connected PVPG system, the stability and reliability of the system, the influence of the unbalanced output-voltage of a three-phase inverter with unbalanced payload, etc. In this dissertation, we research deeply into these key problems, and propose corresponding solutions, i.e., a parallel control technology for a photovoltaic inverter, the maximum power track and control technology of a grid-connected PVPG system, harmonic suppression in a PVPG system, as well as a control algorithm for a three-phase unbalanced payload. The main research work and contributions of this dissertation are listed as follows:(1) A control scheme for high-performance paralleled-inverter in a PVPG system is proposed. This schemde is described below. Firstly, the frequency and phase of a sinusoidal-pulse width-modulation (SPWM) waveform is generated by a field programmable gate array (FPGA), which ensures the sysnchronization of the output voltages. After that, the three-phase alternating voltage and current are reconstructed from their single-phase ones. And then, they are transformed into two two direct components based on instantaneous reactive-power theory, which are transformed into their conresponding active and reactive currents using synchronous d-q transformation. Finally, the instantaneous reactive and active power of the two paralled-inverters are calculated and kept identical by a digital signal processor (DSP), thus the output current of the two inverters is current-sharing. Experiment results show that the control scheme is capable of power-sharing and small circumfluence between the inverters.(2) A maximum power-transmission method for PVPG grid-connected system is proposed. Its control strategy is described as follows:based on incremental conductance method, a control strategy of one cycle power-disturbance is applied in the DC/DC converter to track the PV battery maximum power; the maximum DC current of the PV battery maximum power output is used as the peak value of the instantaneous reference current for the AC feedback control of the output current of the grid-connected inverter in the DC/AC grid-connected inverter. The phrase and frequency of the grid voltage is used as those of the instantaneous AC reference current, the difference between which and the grid AC current is utilized for PI control. For assuring the stability and reliability of the grid-connected inverter, a grid-voltage feed-forward and a feedback of the filter-capacitor current are introduced. The principle and control strategy of the grid-connected control system are detailed analyzed. Simulation for the PV system is done using Matlab/Simulink tools, which validates the feasibility of the above-mentioned control-strategy.(3) This dissertation analyzed the causes that SPWM inverter power supply produces the harmonic and then designed a new three-phase△-band-pass filter. The theoretic analysis and the simulation showed that the filter can restrain the 3rd-19th components and the harmonic component are reduced from 31.5% to 3.1%. Consequently, the power factor and exploitation rate of equipment are improved and the loss-free line and loss of voltage are cut down considerable. Therefore, the PV system can work steadily and the quality of power is improved.(4) A split-phase control method of the output voltage of three-phase inverted power-supply is proposed. Applying the control of output line-voltage of a three-phase inverter, the balance of the three-phase voltage can be utilized, the traditional compensation method of the positive-, negative-and zero-sequence components of output voltage of the three-phase inverter under the case of unbalanced load is implemented by symmetrical component decomposing and superimpose theory in order to keep the the symmetric three-phase output voltage. However it is time-consuming, poor real-time and not easy to control. Thus, this dissertation proposed a novel individual phase control for output voltage of the three-phase inverter. The theoretic analysis and the simulation showed that this method is capable of reducing the maximal unbalance degree (rated load of A-phase,200% rated load of B-phase and no-load of C-phase) from traditional 5.49% to 1%, and the output voltage can reach the balance steadily and reliably when the unbalanced loads goes to 200%. Consequently, the voltage distorting caused by unbalanced load can be compensated effectively, so that the balanced output voltage is guaranteed under any unbalanced load.更多还原