微机控制PWM GTO逆变器变频调速系统

Frequency Control of Motor System Using a PWM GTO Inverter Controlled by Microcomputer

研制了一套由微机产生最优化鞍形波等面积PWM信号来控制的电压型GTO逆变器交流电机变频调速系统。该系统以准16位单片微处理机8098为控制手段,以16位微型计算机IBM SUPER-Ⅲ与MCS-96BH串行通讯所组成的开发装置为基础,以最优化鞍形波PWM开关方案-最小脉动电流法(THD)为控制思想,并与适宜实时计算的等面积对称规则采样法相结合,充分利用准16位单片微机快速的乘除运算,A/D转换及可编程的高速输出器,软件定时器等功能,在6路高速输出端(HSO.0-HSO.5)输出PWM信号,再经光电隔离放大,驱动主电路逆变器的6个GTO。最优化鞍形波等面积PWM方案具有如下优点:1/4波对称可消除偶次谐波,逆变器输出电压近似线性变化,谐波电流有效值的总和为最小,低频时不存在电机转矩脉动现象。带电机负载实验表明,系统运行稳定,调速平滑,反应速度快。

Develops a variable-frequency and adjustable-speed motor system, by using a GTO voltage source inverter, which is controlled by the saddle area-equal PWM pattern, A quasi-16-bit single-chip microprocessor 8098 has been employed as the control means of the system, which is on the basis of the developmental device composed of the serial port between IBM SUPER-Ⅲ and MCS-96BH. An optimal saddle PWM switching scheme——the minimisation of total harmonic current distortion (THD) has been taken as control idea of the system, which is combined with area-equal symmetry regular-sampled technique to be suitable for real-time calculation. The function of the quasi-16-bit single-chip microprocessor, i. e. fast multiplication and divide openation, A/D converter, programmable high-speed output unit and sofeware timer, has been fully utilized. The PWM signals from HS0.0～HS0.5 of the microprocessor, being photo-isolated and amplified, drive the six GTOs in the main circuit of optimal saddle area-equal PWM scheme include: elimination of even hariation by using quarter-wave symmetry, almost linear variation of the inverter output voltage, minimissation of total harmonic current distortion, no torque pulsation in motor at low-frequency. The motor load experimental results show that the system works very satisfactorily witth smooth adjuistment and fast reaction.