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1、Photovoltaic Power Pupply Pine Pave Inverter Based On68HC908MR16 MCU1 IntroductionWith the growing energy crisis and increase the environmental awareness of mankind,the development and utilization of new energy is reccining increasing attention. And solar energy as an inexhaustible supply of highly
2、efficient non-polluting energy has more people of all ages. In this paper, the photovoltaic power system is sinusoidal inverter suitable for a household, especially for electricty without electricity in remote areas of the western region of a power systm users, as Chinas western development will be
3、its market prospects will become more and more broad.2 Structure and principle of the inverter system2.1 The basic structure of the systemFirst of all, by the solar array to the battery charging circuit in order to get a basic stability of the DC voltage, and then by the inverter ciruit will be high
4、-frequency alternationg current into direct current recerse, and finally by the frequency step-up transformer and filter circuit filtering into 50Hz,220V sinusoidal AC voltage.Control of the whole system is completed by a single-chip MR16.The core part of the formation of SPWM wave and the output AC
5、 voltage according to the feedback form, composed of sampling digital PI regulator part.2.2Single-chip on the MR1668HC908MR 16 single chip is a low-cost, high-performance single-chip 8. It has 32k bytes of rewritable flash memory-chip FLASH,with 768 bytes of RAM,this system completely enough;with a
6、dedicated motor for 6-channel PWM output PWMMC modules, suitable for in single-phase, three-phase inverter, at the same time the module was also devoted to the protection Fsult FAULT pin 4, whem the fault does not occur in the case of interruption caused by the rapid blockade of the PWM output to ac
7、hieve the purpose of protection; with the option external crystal clock or internal clock phase-locked loop clock generator modul, the system chosen by the internal PLL clock can producc accurate 8MHz internal bus frequency, so as to ensure the accuracy of the frequency of the system; with programma
8、ble AD clock. AD fastest conversion time only 2s,to minimize disroption of program execution tim;with SCI serial communication interface, can work infull-duplex or half-duplex mode, in this system can reliably be completed with the outside world keyboard monitor serial communication system.2.3 Inver
9、ter Main Circuit Switching device is appropriate for low-power devices, with switching speed, high frequency characteristics of the power MOSFET. Switch gate drive signal from the single-chip MR16 wave generated by the SPWM signal driver circuitl Full-bridge inverter SPWM output for high-frequency w
10、ave, the step-up transformer and filter immediately be 220V,50Hz standard AC ovltage sinusoidal.2.4 SPWM wave formation68HC908MR16 with a special single-chip motor control can be used to work in threepairs of complementary mode or standalone mode, including 6-channel PWM output module PWMMC, Initial
11、ization of the system in its work in three pairs of complementary patterns in the same bridge that the two PWM signal arm is complementary, in the initialization of dollars to write a value to the PMOD(H:L) in orde to determine the carrier frequency that is switching frequency. Real-time wave PWM pu
12、lse width calculation is completed by the interruption of the procedure, each PWMMC module PCTN(H:L) register, single-chip will PVALX(H:L) of the value of PMOD(H:L) after the value in the automatic generation of SPWM signal sent by the PWM pin,. In order to prevent the same bridge arm of the two tub
13、es at the same tine the phenomenon of conduction occurred in the absence of signal generator DEADTIME in DEADTM writes a register balue to determine the dead time. The design of the system time for 2.5s, the carrier frequency to 10KHz, including 200 made to enlarge the value of the sine sine table.
14、There are 4modules PWMMC fault protection port FAULT1FAULT4,when the port when high, PWMMC initialization can be set to block in accordance with the corresponding PWM output, the sstem is the use of the over-current protection function, When over0current, it FAULT1 home port in order to place all si
15、x road blockade PWM port. PWMMC work the system so that the center alignment mode, in the PWM clock frequency of 8MHz carrier under its formula for the cycle Carrier cycle =1/10k=PMOD(H:L)(1/8M)2Therefore, the system must be initialized PMOD(H:L) =0190(Note: for the MR16 in hexadecimal notation)2.5
16、System control structure The system through the digital PI regulator to control realization of regulators. The control system block diagram shown in figure 3.AC voltage feedback signal from the AD sample. In order to ensure accuracy, the system uses sampling voltage transformer,Just start to set out
17、put voltage from the soft-start, soft-start is generated at startup in order to avoid large peak currentl. Soft-start the use of successive incremental increases to a voltage required for the method,after the soft-start voltage is set to correspond to 220V voltage values, In order to enhance the spe
18、ed, the system uses a feedforward control and feedback control of the control method of combining.In order to enhance the output characteristics of the dynamic system. The system changes in accordance with the ratio of deviation of the size of coefficient and integral coefficient of the fuzzy contro
19、l method, when the deviation is larger, the proportion coefficient and integral coefficient is aslo larger., when the deviation of the proportion of small coefficients and imtergral coefficient smaller, thus reducing the overshoot, it iseasy to make the system stable,the total elimination of the int
20、egral saturation phenomenon,but also to enhance the adaptability of the system.3 Serial CommunicationIn order to enhance the systems ability to adapt to different environments,it is necessary to monitor and control system to monitor and modify the parameters of regulation,this system uses a serial c
21、ommunication technology keyboard monitoring system with the outside world to communicate.Procedures on the use of inquiry methods to the outside world periodically send test data,test data including the solar cell voltage,charge current, battery voltage,DC current ,output voltage,output current, hea
22、t sink temperature,when the event of the failure priority send fault signal,when the need to modify parameters and modify data on the reception of the corresponding parameters,and use the methods of calibration and calibration test of the accuracy of data communication. MAXIMs hardware as a MAX485 i
23、nterface chip to work in half-duplex mode, while the system optocoupler isolation systems approach to enhance anti-interference ability and reliability.4 System software designThe modular design of system software, including the initialization module, the protection module, regulator modules, commun
24、ication modules, such as interruption of program modules,in addition to disruption of modules outside the main program on the remaining modules, which will completion of system initialization main module initialization, the variable unit, given the initial value of the register unit.Protection modul
25、e in accordance with voltage and current sample values to determine fault and the fault occurs in the PWM output of the blockade. Protection,including under-voltage battery voltage, over-voltage protection can be achieved since the restoration, that is, the battery voltage is detected and returned t
26、o normal, the system re-soft start and resume normal work. Overcurrent protection as a result of the rapid response they need to protect the use of hardware, when the over-current at the time of the blockade as soon as all the PWM output, but also sealed off all the driving circuit, only to return t
27、o work can be rest, software can determine whether there has been over-current protection.Regulator module to complete the system of the PI regulator output voltage regulation, entrance to the output parameters for the soft-start exports to the disruption module M parameters involved in the calculat
28、ion of PWM pulse width. Through real-time adjustment of the value of the parameter value can be changed so that the output pulse width given to follow.Interruption of program modules to complete the issue of SPWM waveform, AC voltage, AC current parameters of the sample. Interruption of the entrance
29、 parameters of PI regulator for the output parameter M, the parameters involved in the calculation of pulse width that is PVALX(H:L) values calculated, thus changing the duty cycle which regulates the output voltage 2 in accordance with the the rules of SPWM sampling methods, combined with the initi
30、alization of PWMMC set formula for calculating real-time pulse width for real-time pulse width forIs a half cycle:PVALX(H:L)=PMOD(H:L)/2+M*SIN(PTR)Negative half-cycle:PVALX(H:L)=PMOD(H:L)/2-M*SIN(PTR)One PTR pointer to sine table, SIN (PTR) for the corresponding sine value of the pointer PTR.5 Concl
31、usionPrototype made in accordance with the above thinking, the last to be relatively standard 220V,50Hz sinusoidal voltage, soft-start is also very stable, its frequency error =0.1%,the output voltage err of =0.5%. As a result of the carrier frequency of 10KHz, in the transformer primary side to be
32、20kHz high-frequency signals without noise. Under the above-mentioned control can ensure the system load or a sudden reduction in load to maintain output voltage stability quickly. Keyboard and monitor system with the outside world of the scrial. Communication good,strong practicality and reliabilit
33、y.基于68HC908MR16单片机的光伏正弦波逆变电源1 引言随着能源危机的日益加剧和人类环保意识的提高，新能源的开发利用越来越受到人们的重视。而太阳能作为取之不尽用之不竭的高效无污染的能源近来更受人们的青睐。本文介绍的光伏正弦逆变电源系统正是一种适于户用的、特别适于无电少电的西部边远地区用户的一种电源系统，随着我国西部大开发的进行其市场前景必将越来越广阔。 2 逆变系统结构及原理 2.1 系统基本结构 首先太阳电池阵列经充电电路向蓄电池充电，从而得到一个基本稳定的直流电压，再经逆变电路将直流电逆变成高频交流电，最后经工频变压器升压和滤波电路滤波变成50Hz、220V正弦交流电压。整个系统的
34、控制都是由MR16单片机完成的。其核心部分为SPWM波的形成及根据输出交流电压采样形成反馈组成的数字式PI调节器部分。 2.2 关于MR16单片机 68HC908MR16单片机是一种低成本、高性能的八位单片机。它具有32k字节的可擦写的片内闪速存储器FLASH，具有768字节的RAM，对于本系统来说完全够用；具有一个专门用于电机控制的6路PWM输出的PWMMC模块，适合于单相、三相逆变，同时该模块还有专门用于故障保护的4路FAULT引脚，当故障发生时可在不引起中断的情况下快速封锁PWM输出达到保护的目的；具有可选择外部晶振时钟或内部锁相环时钟的时钟发生器模块，本系统选择的内部锁相环时钟能产生精
35、确的8MHz的内部总线频率，从而保证了系统的频率精度；具有可编程的AD时钟,AD转换时间最快只需2s，能最大程度地减少中断程序的执行时间；具有SCI串行通信接口，可工作于全双工或半双工模式，在本系统中能够可靠地完成与外界键盘监控系统的串行通信。 2.3 逆变主电路 其中开关器件采用适合于小功率装置、具有开关速度快、工作频率高等特性的功率MOSFET。开关管的栅极驱动信号来源于MR16单片机产生的SPWM波经驱动电路后的信号。全桥逆变的输出为高频SPWM波，经变压器升压及滤波后即得到220V、50Hz的标准正弦交流电压。 2.4SPWM波的形成 68HC908MR16单片机具有一个专门用于电机控
36、制的可工作于3对互补模式或独立模式的包括6路PWM输出的PWMMC模块。在本系统中初始化使其工作于3对互补模式即同一桥臂2个PWM信号是为互补的，在初始化中写一计数值到PMOD(H:L)中以决定载波频率即开关频率。PWM波的实时脉宽计算是由中断程序完成的，每次PWMMC模块中的PCTN(H:L)计数器计数到PMOD(H:L)中的值时就引起中断。预先将0360的正弦值制成表格存于FLASH某一区域中，每次中断时从中取一正弦值，经过一定计算后得一数值，将其送入PVALX(H:L)寄存器中，单片机将PVALX(H:L)中的值与PMOD(H:L)中的值比较后自动生成SPWM信号并由PWM引脚发出。为了
37、防止同一桥臂两个管子同时导通的现象发生，在无信号发生器DEADTIME中的寄存器DEADTM中写入一数值以确定死区时间。本系统设计死区时间为2.5s，载波频率为10kHz，制成包括200个放大的正弦值的正弦表。PWMMC模块还有4路故障保护端口FAULT1FAULT4，当端口为高电平时，PWMMC就能根据初始化设定来封锁相应的PWM输出，本系统中的过流保护正是利用了这个功能，当发生过电流时，就置位FAULT1端口从而封锁全部六路PWM端口。本系统使PWMMC工作在中心对齐模式，在PWM时钟频率为8MHz下其载波周期计算公式为 载波周期=1/10k=PMOD(H:L)(1/8M)2 所以本系统须
38、初始化PMOD(H:L)=0190(注：为MR16中十六进制符号) 2.5系统的控制结构 本系统通过数字式PI调节器实现稳压控制。系统的控制框图如图3所示。反馈信号来自交流电压的AD采样，为了保证精度，本系统利用变压器进行电压采样。刚启动时给定电压取自软启动输出，软启动是为了避免启动时产生大的峰值电流，软启动采用逐次加1递增到所需电压的方法，软启动结束后给定电压就是对应于220V电压的数值。为了加强快速性，本系统采用前馈控制与反馈控制相结合的控制方式。为了增强系统的动态输出特性，本系统采用根据偏差大小改变比例系数和积分系数的模糊控制方法，当偏差较大时，比例系数和积分系数也较大，当偏差较小时比例
39、系数和积分系数也较小，从而大大减少了超调量，很容易使系统稳定，完全消除了积分饱和现象，也增强了系统的适应能力。 3 串行通信 为了增强系统适应不同环境的能力，有必要对系统进行监控监测及对参数进行修改调节，本系统采用串行通信技术同外界键盘监控系统进行通信。程序上采用查询方式，周期性地向外界发送检测的数据，检测的数据包括太阳电池电压、充电电流、蓄电池电压、直流侧电流、输出电压、输出电流、散热器温度等，当发生故障时优先发送故障信号，当需要修改参数时就接收数据并修改相应参数，并使用校验和校验的方法检验数据通信的准确性。硬件采用MAXIM公司的MAX485作为接口芯片使其工作于半双工模式，同时本系统采用
40、光耦隔离的办法以增强系统抗干扰能力，提高可靠性。 4 系统的软件设计 本系统软件采用模块化设计，包括初始化模块、保护模块、调节器模块、通信模块、中断程序模块等，除中断模块外其余模块都放在主程序中进行。初始化模块主要完成系统的初始化、各变量单元、各寄存器单元赋初值。 保护模块根据电压电流采样值进行故障判断，并在故障发生时封锁PWM的输出。保护包括蓄电池欠压、蓄电池过压、系统过载、过热保护等，其中蓄电池欠压、过压保护能够实现自恢复，即在检测到蓄电池电压又恢复正常时，系统重新软启动并恢复正常工作。过流保护由于需要快速反应故采用硬件保护，当过流发生时就立即封锁全部PWM输出，也立即封锁全部驱动电路，只
41、有重新复位时才能恢复工作，软件可判断出是否发生过流保护。 调节器模块完成对系统输出电压稳压的PI调节，使输出电压稳定在220V，同时软启动也放在其中。其入口参数为软启动输出，出口参数M送到中断模块中参与PWM脉宽的计算。通过实时调节该参数的值就能改变脉宽值从而使输出跟随给定。 中断程序模块完成SPWM波形的发出、交流电压、交流电流参数的采样。中断的入口参数为PI调节器的输出参数M，该参数参与脉宽的计算即PVALX(H:L)值的计算，从而改变了占空比也即调节了输出电压。按照SPWM的规则2采样的方法，结合初始化中对PWMMC的设定得脉宽的实时计算公式为 正半周期： PVALX(H:L)=PMOD(H:L)/2MSIN(PTR) 负半周期：PVALX(H:L)=PMOD(H:L)/2MSIN(PTR) 其中PTR为正弦表指针，SIN(PTR)为对应PTR指针的正弦值。 5 结束语 按照以上思想制成样机，最后能得到比较标准的220V、50Hz正弦电压，软启动也很平稳，其频率误差0.1,输出电压误差0.5。由于采用10kHz的载波频率，在变压器原边得到20kHz高频信号，无噪声。在上述控制方式下，能保证系统在突然加载或减载时输出电压快速地保持稳定。并且与外界键盘监控系统的串行通信良好，有较强的实用性和可靠性。