电气专业毕业设计外文翻译6.docx

附录一： 中文翻译光伏阵列和逆变器摘要-本文提出了一种双向电子转换器，这两项措施的特性曲线光伏发电机和物理模拟其实时物理行为。这两个转换器的运行模式（模拟和测量）可以用微控制器实施其数字化。该转换器的电流控制的手段，是通过一个类比变滞后控制回路，其范围是由微控制器提供。在测量作业模式中，数字电压控制回路的实施，使光伏发电支付其四特性曲线。在模拟运行模式中，测量的电压和电流范围是从编程计算或衡量四特性曲线。该系统每秒可以测量三次7光伏发电机的特性曲线，然后效仿其电气性能测试的光伏逆变器。分析光伏发电机和逆变器，不但可以可靠地运行，其结果可以帮助他们更好地工作。比较它们的性能以及在实现最佳配置上， 仿真和实验结果都非常令人满意。1 导言完整的表征光伏阵列和逆变器，尤其是在不同操作条件下，采用光伏系统是一个非常重要的方面。对于光伏阵列，实验室中使用不同的设备，以获取他们的I - V特性曲线。关于光伏逆变器，各种实时模拟器已经被提出来在不同操作条件下用于测试逆变器。然而，在一段时间内实验室里的所有这些系统都无法“保存”几个光伏发电机的四特性曲线的实时演变，从而“仿造”它提供一个变频器。这些优化设计的设备和光伏系统的配置显示出的特征结果是非常有趣的。通过测量四特性曲线在一段时间内的不同光伏阵列，可以从已知的能源里获得最大值，这是可以用整个光伏发电机计算的最高能量。一旦获得这一信息，就有可能确定出一个系统的配置功能（系列/并行方面，中环/字符串转换器等）消耗的总能量 ，然后这个能源与可以从整个光伏发电机获得的最大能源相比。总之，不同配置的系统可以进行比较，然后从能源的角度可以确定一个最理想的。另一方面，一个分析在不同的现实条件下实现最大功率点跟踪（最大功率跟踪）技术的文献提出一个仿真器复制这些实时的I - V特性曲线是可行的。此外，在实验室里这个模拟器可以进行分析的行为，在特殊条件下（局部阴影，黎明，黄昏等）最大功率跟踪技术和完整的光伏发电系统没有必要进行实地试验，特别是等待大气条件。实验室里，在没有真正的光伏能源的条件下，光伏发电机的电气性能仿真允许光伏逆变器进行性能分析。上一段描述的电子转换器有两个操作模式。其主要优势是拟议转换器是把其性能和运作模式结合起来的唯一设备：特性曲线测量作业模式允许获得光电发生器的电压和电流的转变模式，在实验室里，这一模式就可以用于测试任何变频器。因此，这个逆变器将通过一个相当可靠的光伏电压的电力仿真行为被测试，在实际运行条件下其性能将获得一个非常高的精度。设计和建造一个15千瓦的样机，在测量作业模式中，这个原型可以每秒同时衡量三次7种不同的光伏发电机的特性曲线。就像将要显示的一样，实验测试取得了令人满意的成果。在模拟操作模式中，原型可以仿效最高电压和电流为500 V和30A的光伏发电机的行为，并分别提供了一个最大为15千瓦的功率。2 系统的提议描述系统的提议方案如图1 ，它主要由显示在图片中央的电子转换器，显示在光伏发电机左侧的微控制器和显示在右侧逆变器组成。图1 模拟仿真测试系统15千瓦的实验电子转换原型是系统的的核心。其目前的控制手段是通过内部类比控制回路实现的。同时包括带有电压和电流传感器的测量板和转换器。针对过电压和过电流，该转换器包括若干电子对其防御。电子转换器能够在测量和仿真这两种不同的模式下运行。这两种运行模式是通过集成在一台PC的DSP微控制器驱动的。在测量操作模式中，该设备与7种不同的光伏发电机的最大值相连接。数字电压控制回路是在微控制器编程以后，使光伏发电覆盖其完整的I - V特性曲线。电压控制回路为内部电流环提供了参考。然后每秒三次连续测量其特性曲线。获得的数据都储存在个人电脑，为后面的分析做准备，还用于为模拟操作模式产生电流电压模式。电脑还可以用来对四特性曲线进行实时监测。在模拟操作模式下，被测试的逆变器连接到转换器和微控制器从理想电流电压模式产生参考电流，这是通过测量四特性曲线特定光伏发电机演变获得的。这样，无论是直接通过微控制器编程或通过前测量测量操作模式获得，设备都可以作为任何电力阵列性能的实时仿真器。因此，光伏逆变性能和效率以及表征任何最大功率跟踪算法可以可靠地，准确地被执行。正如介绍中所说，设备可以仿效光电发电机的性能，最高可以达到15千瓦，最大短路电流和开路电压分别可以达到30安和500伏。图2显示了变换器的结构。从图中可以看出，它是由一个双向DC / DC转换器以及过滤阶段和能量耗散电路组成的。图2 电子转换器的结构该转换器由两个IGBT，T1和T2 ，以及两个二极管D1、D2组成，是由一项纠正交流三相电压源提供电流的。转换器的输出主要由允许短期和开路作业的电感L和电容C1和C2 组成。过滤器的其他部分是根据减轻切换谐波，同时能消除谐振模式，并尽量减少损失的目的设计的。在模拟操作模式下，该转换器成为一个由交流电压提供的勃克穆利纠正所。在这种情况下，能源从AC源传输到了连接到输出拟议转换的光伏逆变器。为了使转换器效仿光伏发电机的性能，测量输出电压被发送到外部微控制器（ DSP ），控制器的作用是计算从编好的I-V特性曲线中由转换器收集的电流 。如图3所示，电感L中的电流IL由变滞环电流控制回路来控制。这个控制回路可以实现短路操作，这样就可以测量和仿真光伏阵列。转换器的输出过滤器基本不影响动态电流控制环路，因为过滤器是用来过滤频率远高于控制回路所需的切换谐波。总之，除了快速的输出电压变化，转换器的输出电流实际上和电感器中的电流相等。在测量作业模式下，转换器由光电发电器提供能量驱动。光电发电器的能量在耗散电路中消散。这个耗散电路包括一个IGBT的T3，二极管 D3 ，和耗散电阻R。在这种工作模式下，通过转换器，光电发电器可以完整地作出伏安特性曲线。原则上，可以用两种方法来概括光电发电器的特性曲线。一个是以电流为轴，一个是以电压为轴。然而，从伏安特性曲线的外形来看，很明显用第二种方法会得到更好的结果，因为第一种方法所得到的斜坡远高于第二种方法所得到的斜坡。由此我们可以得出一个结论：转换器的输出电压必须受到控制，而且要断路、短路时的参考点不同。附录二： 外文原文The Analysis of Photovoltaic Arrays and InvertersAbstract - This paper proposes a bi-directional electronic converter that both measures the characteristic curves of photovoltaic generators and physically emulates their real-time physical behavior. The two converter operation modes (emulation and measurement) are digitally implemented in a microcontroller. The converter current is controlled by means of an analogical variable-hysteresis control loop, whose reference is provided by the microcontroller. In the measuring operation mode, a digital voltage control loop is implemented to make the photovoltaic generators cover their I-V characteristic curves. In the emulating operation mode, the voltage is measured and the current reference is calculated from the programmed or measured I-V Characteristic curve.The system can measure three times per second the characteristic curves of up to seven photovoltaic generators and then emulate their electrical behavior to test photovoltaic inverters. Analysis of photovoltaic generators and inverters can thus be reliably carried out, and the results can help to bothcompare their performance and achieve optimal configurations.Simulation and experimental results are very satisfactory.I. INTRODUCTIONThe complete characterization of photovoltaic arrays and inverters, specially their performance under different operating conditions, is a very important aspect in photovoltaic systems. In the case of photovoltaic arrays, different equipments are used in the laboratories to obtain their I- V characteristic curves. Concerning the photovoltaic inverters, a variety of real-time simulators have been proposed to test the inverters under different operating conditions.However, all these systems are not able to both “save” the real-time evolution of the I-V characteristic curves of several photovoltaic generators during a period of time, and then “reproduce” it to supply an inverter at the laboratory. An equipment with these characteristics results to be very interesting for an optimum design and configuration of the photovoltaic systems. By measuring the I-V characteristic curves of different photovoltaic arrays during a period of time, the maximum available energy of each one of them can be known, and then it is possible to calculate the maximum energy that could be obtained from the whole photovoltaic generator. Once this information becomes available, it is possible to determine the total energy that can be obtained as a function of the configuration of the system (series/parallel connection, central/string converter, etc.), and then this energy can be compared with the maximum energy available from the whole photovoltaic generator. In short, the different configurations of the system can be compared and then the optimal one can be determined from an energy point of view. On the other hand, with an emulator that can reproduce in real time these I- V characteristic curves, a reliable analysis in real conditions of the different maximum power point tracking (MPPT) techniques proposed in the literature can be carried out. In addition, with this emulator it is possible to analyze at the laboratory the behavior of both the MPPT techniques and the complete photovoltaic system under special conditions (partial shading, dawn, nightfall, etc.) with no need to make field tests and wait for particular atmospheric conditions. The emulation of the electrical behavior of photovoltaic generators allows performance analysis of photovoltaic inverters to be carried out at the laboratory without requiring real photovoltaic energy sources. In this paper, an electronic converter is proposed that has the two operation modes described in the previous paragraph. The main advantage of the proposed converter is its ability to combine both operation modes in an only equipment: the characteristic curves measuring operation mode permits to obtain a pattern for the evolution of the voltage and current of the photovoltaic generator, and this pattern can then be used to test any inverter at the laboratory. This inverter will be tested, therefore, by means of a very reliable emulation of the electrical behavior of the photovoltaic generator, and its performance under real operating conditions will be obtained with a very high accuracy.A 15 kW prototype has been designed and built. In the measuring operation mode, this prototype can measure simultaneously three times per second the characteristic curves of 7 different photovoltaic generators. Experimental tests have achieved satisfactory results, as will be exposed later. In the emulating operation mode, the prototype can emulate the behavior of a photovoltaic generator with maximum voltage and current of 500 V and 30 A, respectively, providing a maximum power of 15 kW. DESCRIPTIOONF THEP ROPOSED SYSTEMThe scheme of the proposed system is presented in Fig. 1. It consists mainly of the electronic converter, shown in the central picture, the microcontroller, shown on the left and the photovoltaic generators and inverters, shown on the right.Fig. 1. Proposed emulation-measurement systemThe 15 kW experimental electronic converter prototype is the heart of the system. Its current is controlled by means of an inner analogical control loop.Together with the converter, a measuring board with the voltage and current sensors is included. The converter includes several electronic protections against over-voltages and over-currents. The electronic converter can operate in two different modes: measuring and emulating. Both operation modes are driven by means of the DSP microcontroller, which is integrated in a PC.In the measuring operation mode, the equipment is connected to a maximum of 7 different photovoltaic generators. A digital voltage control loop is then programmed in the microcontroller to make the photovoltaic generators cover their complete I- V characteristic curves. The voltage control loop provides the reference for the inner current loop. The characteristic curves are then continuously measured three times per second. The data obtained are stored in the PC so that they can be both analyzed later and used to generate the current-voltage pattern for the emulating operation mode. The PC can also be used to make a real-time monitoring of the I-V characteristic curves.In the emulating operation mode, the inverter to be tested is connected to the converter and the microcontroller generates the current reference from the desired current-voltage pattern, which was obtained by measuring the evolution of the I-V characteristic curve of a particular photovoltaic generator. In this way, the equipment behaves as a real-time emulator of any electrical array behavior that has been either programmed directly in the microcontroller or obtained by previous measurements in the measuring operation mode. Performance and efficiency of photovoltaic inverters can therefore be reliably and accurately carried out, as well as the characterization of any MPPT algorithm. As it was pointed out in the introduction, the equipment can emulate the behavior of photovoltaic generators up to 15 kW, with maximum short-circuit currents and open-circuit voltages of 30 A and 500 V, respectively.Fig. 2. Structure of the electronic converterFig. 2 shows the structure of the proposed converter. As it can be observed, it consists of a bi-directional DC/DC converter, a filtering stage and an energy dissipation circuit.The converter, which is made up of two IGBT, TI and T2, and two diodes, DI and D2, is supplied by means of a rectified AC three-phase voltage source. The output of the converter consists mainly of the inductor L and the capacitors C1 and C2, which permit the short and open-circuit operation. The other elements of the filter are designed with the aim of attenuating switching harmonics, while eliminating resonant modes and minimizing losses.In the emulating operation mode, the converter works as a Buck supplied by the rectified AC voltage. In this situation, the energy flows from the AC source to the photovoltaic inverter that is connected to the output of the proposed converter. In order to make the converter emulate the behavior of a photovoltaic generator, the measurement of the output voltage is sent to the external microcontroller (DSP), which calculates the current to be generated by the converter from the programmed I-V characteristic curve.The current IL through the inductor L is controlled by means of the variable-hysteresis control loop shown in Fig. 3. This control loop permits the short-circuit operation that is required both to measure and to emulate the photovoltaic arrays. The filter at the output of the converter hardly affects the dynamics of the current control loop because it is designed to filter switching harmonics whose frequencies are higher than that expected for the current loop. In short, except for quick output voltage variations, the current at the output of the converter will be practically similar to the current IL through the inductor L. The variable-hysteresis current control loop presented in Fig. 3 achieves constant frequency operation by means of tuning the hysteresis width AI as a unction of the duty cycle D. The hysteresis width is in fact the current ripple. The necessary limitation of this ripple will produce variable frequency behavior at low and high duty cycles. In the measuring operation mode, the converter works as a Boost supplied by the photovoltaic generators. The energy coming from the photovoltaic generators is dissipated in the dissipation circuit, which consists of an IGBT, T3, a diode, D3, and a dissipation resistor, R. In this operation mode, the converter has to make the photovoltaic generators cover their complete I- V characteristic curves. In principle, there are two options to cover the characteristic curve of a photovoltaic generator. It can be covered along either the current axis or the voltage axis. However, from the shape of the I-V characteristic curves, it is clear that better results will be obtained if the second option is chosen because the slope in the first option is considerably higher than that of the second one. As a conclusion, the output voltage of the converter has to be controlled and its reference varied from the open to the short-circuit condition.