非理想接入条件三相变换器并网适应性分析及优化控制研究

With a large number of inputs of intermittent new energy and nonlinear large load, grid voltage unbalance, harmonics, sudden change, frequency offset and so on is increasing year by year. Additionally, DC side of the converter is also vulnerable to a variety of disturbances. And, in actual, several situations may also occur at the same time. So stability of the grid-connected converter has been seriously affected. There are some problems in the existing control system, such as disunified basis for analysis, aiming at the single problem, responding passively and poor applicability. To improve the adaptability and initiative of the three-phase grid-connected converter, three aspects, i.e., unified modeling, analysis and determination of the stability and comprehensive control strategy, are studied. Unified models of the power grid, the converter and the power supply at the DC side, including the time and frequency domain dynamic models, small-signal state space models, large-signal state space average models and models normalization, are established. The effect mechanism of power grid dynamic characteristics, DC-side input disturbances and grid synchronization detection on voltage and current control of the converter is deeply revealed. Considering the compensation mechanism for correction in the non-ideal state of power grid, and adopting feedforward control, system calibration, parameters adaptive method and so on, optimized core algorithm is explored and formed in a combination of a variety of complex situations. Through this topic, some contribution would be made to our country's new-energy grid-connected basic theory.

)：随着一些间歇性新能源、非线性大负荷的大量投入，电网电压不平衡、谐波、突变、频率偏移等情况正逐年增加。加之变换器直流侧也易受到多种扰动，且实际系统中几种情况还可能同时发生，严重影响并网变换器稳定工作。现有控制方法存在着分析基础不统一、针对问题单一、被动应对以及适用性不强等问题。为提高三相变换器并网适应性及主动性，开展变换器交直流侧非理想接入情况下的统一建模、稳定性分析判定、综合控制策略研究等三方面内容。建立电网、变换器及直流侧电源的统一模型，包括时频域动态模型、小信号状态空间模型、大信号状态空间平均模型、模型归一化等，深入揭示电网动态特性、直流侧电源扰动、电网同步检测等对电压电流控制特性的影响机理。考虑矫正电网非理想状态的补偿机制，拟采用前馈控制、系统校正、参数自适应等方法，探索形成多种复杂情况共同作用下的并网控制核心优化算法，为我国新能源并网基础理论的构建做出一定贡献。

随着一些间歇性新能源、非线性大负荷的大量投入，电网电压不平衡、谐波、突变、频率偏移等情况正逐年增加。加之变换器直流侧也易受到多种扰动，且实际系统中几种情况还可能同时发生，严重影响并网变换器稳定工作。现有控制方法存在着分析基础不统一、针对问题单一、被动应对以及适用性不强等问题。为提高三相变换器并网适应性及主动性，开展变换器交直流侧非理想接入情况下的统一建模、稳定性分析判定、综合控制策略研究等三方面内容。建立电网、变换器及直流侧电源的统一模型，包括时频域动态模型、小信号状态空间模型、大信号状态空间平均模型、模型归一化等，深入揭示电网动态特性、直流侧电源扰动、电网同步检测等对电压电流控制特性的影响机理。考虑矫正电网非理想状态的补偿机制，拟采用前馈控制、系统校正、参数自适应等方法，探索形成多种复杂情况共同作用下的并网控制核心优化算法，为我国新能源并网基础理论的构建做出一定贡献。通过四年的大量研究，项目分别在电网电压不平衡、谐波畸变、电网大阻抗、模型预测控制以及基于MMC拓扑的控制策略等方面进行了大量的研究，取得了诸如电网不平衡系统建模及多目标优化控制策略、基于输出导纳重塑的电网电压谐波抑制方法、宽谐振阻尼区域的LCL滤波器电容电流反馈有源阻尼方法、电网阻抗耦合下多并网逆变器并联运行稳定性、MMC变频运行子模块电容电压波动抑制方法、MMC的快速模型预测控制策略、分层序列优化算法的模型预测控制建模方法等成果，通过本项目的研究一共发表了15篇论文，其中SCI检索8篇，授权专利6项，培养了9名硕士、3名博士。超额完成预期指标，预期将对提高非理想接入条件三相变换器并网适应性提供有益参考。