高频UPS双环控制及并联运行关键技术研究.pdf

摘 要 不间断电源（UPS）的并联运行是提高供电系统供电可靠性以及增大系统供电容 量的主要技术手段本文在研发设计三台三相 40KVA 高频UPS并联系统的基础上，针 对高频UPS并联系统中的关键问题，分别对单相电流内环的双闭环逆变器波形控制、 基于双闭环的逆变器并联模型及环流特性、数字锁相环线性模型及特性、逆变器分散 逻辑并联控制等问题中的某些方面进行了比较详细的分析和研究 以负载电流作为可检测的扰动输入， 建立了开环逆变器的连续数学模型， 提 出了等效输出阻抗的逆变器模型提出电流内环电压外环的双闭环控制方法，并对该 结构进行了比较详细的分析从输出阻抗的角度分析了该控制方案抑制负载扰动的机 理，以及比较详细地分析了不同的控制器参数和前馈补偿系数对输出阻抗的影响通 过实验结果进一步表明，基于电流内环的双环控制方法是可行的 PWM建立了基于带输出阻抗的逆变器并联等效模型，并在该模型基础上对环流特性进 行了详细分析结合双闭环控制的特点，采取负载平均电流进行前馈补偿的方法，在 不降低抗负载扰动性能的前提下，增大了双闭环控制的逆变器并联之间的输出阻抗， 减小了并机环流，并推导出了基于双闭环的逆变器并联系统环流的表达传函，分析了 其环流的特性，然后为了进一步减小两机差异引起的环流，提出了瞬时环流下垂的方 法，且通过仿真做了进一步的验证。

锁相是分散逻辑控制的并机系统中不可缺少的部分基于市电周期作为扰动输入 量建立了数字锁相环的线性数学模型，进行了稳定性分析，给出了数字锁相环稳定的 条件基于UPS锁相的特殊性，着重分析了市电频率扰动以及相位给定突变时的系统 动态特性，仿真分析表明在同一个数字锁相环中，锁相误差抖动小与输出频率变化不 能过快，二者不可兼得因此，为了解决并机中既要求锁相精度高，输出频率变化又 不能太大的矛盾，提出了二级锁相和“再调制”的方法另外，针对电网频率波动较 大，并联运行的UPS在锁相和自振之间切换时可能出现的失锁现象，提出了一种握手 同步锁相的方法，简要说明了该方法的基本原理，并在实验中得到验证 在双闭环逆变器并联系统环流特性的基础上，给出了基于环流功率调节做为最外 环的控制策略为了提高电压的稳压精度以及加快环流收敛速度，在实际应用中采取 了一些措施并在实验中进行了实现，实验结果表明这种控制方案可以实现可靠并联 关键词：UPS 并联运行 输出阻抗 瞬时反馈 双闭环 均流控制 环流 数字锁相环 再调制 IAbstract Uninterrupted Power Supply’s (UPS) paralleling operation is the main technique to enhance the reliability and enlarge the capacity of the power supply. Based on the research and design for a paralleling operation system of 3 Three-phase 40KVA online UPSs, several key factors concerning paralleling operation are studied in detail in some respects, such as dual-loop control based waveform correction techniques, the parallel model and circumfluence characteristics of the paralleling operation system based on dual-loop control, Digital Phase Lock Loop (DPLL)’s linear mathematical model and characteristics, distributed logic based load-sharing control method, etc. With the load current treated as a measurable disturbance input, a linear mathematical model is established for a PWM inverter, and a electric model with equivalent output impedance for the PWM inverter is presented. A dual-loop control method with inductor current feedback as inner loop is introduced, and the control structure is analyzed in detail. While the output current feedforward is adopted, the inverter has a high dynamic performance when supplying a non-linear load, the distortion of the output waveform is restrained. The mechanism that how does this control method restrain the load current disturbance is analyzed from the aspect of output impedance, and the influence on the output impedance by various controller parameters is explained. Experiment results indicate that inductor current feedback based dual-loop control method is feasible. A parallel equivalent electric model with output impedance is established, on the basis of this model, circumfluence characteristics are analyzed in detail. Considering the advantage of dual-loop control, load average current feedforward is introduced, by which the impedance between two inverters connected is enlarged without losing the dynamic characteristic, so the circumfluence is reduced. The transfer function of the circumfluence based on dual-loop controlled inverters’ parallel system is brought out, and by which the circumfluence characteristic is analyzed. In order to reduce the circumfluence further, an instantaneous circumfluence droop method is introduced. Furthermore the simulation has been carried out, and the analysis above is coincident with the simulation results. Phase Lock is a indispensable part in parallel operation system based on distributed logic control. Digital PLL’s linear mathematical model is established, and it’s stability is analyzed, then the DPLL’s stability conditional expression is given. Whereas the phase lock in UPS is very particular, this dissertation emphasizes on the dynamic performance with IIdisturbance of the utility source’s frequency noise and the reference phase. Simulation results indicate that lower phase erro and slower output frequency alteration are not coexistent. In order to solve this conflict in parallel operation system, a 2-level PLL and a re-modulation technique are employed. On the other hand, a synchronization phase lock method with handshake is realized, minimizing the possibility of the UPS’s losing lock with each other when the utility source is unstable. On the basis of the circumfluence characteristic of dual-loop controlled inverter’s paralleling system, the circumfluence power control strategy is given. To get more precise voltage steady magnitude and faster circumfluence convergence speed, some measurement is adopted in experiment. The experiment has been done, the results tell the control strategy adopted can restrain the circumfluence effectively. Keywords: UPS; paralleling operation; output impedance; instantaneous feedback; dual-loop; circumfluence; load sharing control; Digital Phase Lock Loop; re-modulation III独创性声明 本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作 及取得的研究成果。

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