Flux-Weakening Strategy for PMSM Finite-Control-Set Model Predictive Control System Utilizing Closed Loop of Expected Fundamental Voltage

Flux weakening (FW) control is the core technology for permanent magnet synchronous motors (PMSMs) to operate above base speed. The size of the expected fundamental voltage vector (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula>) serves as the key criterion for determining whether FW operation is required. However, in finite-control-set model predictive control (FCS-MPC) system, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula> cannot be obtained directly. Focusing on this problem, this article derives the quantitative model of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula>. According to the deadbeat control model and the actual discrete model of stator current, the quantitative relations among the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula>, the reference voltage vector (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u}_{\mathbf{ref}}$</tex-math> </inline-formula>), and the actual output voltage vector (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u}_{\mathbf{act}}$</tex-math> </inline-formula>) are derived. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula> for the current control cycle is derived from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u}_{\mathbf{ref}}}$</tex-math> </inline-formula> and the voltage error accumulated in the preceding cycle. On this basis, the FW control scheme based on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{u_{\mathbf{EFV}}}$</tex-math> </inline-formula> closed-loop is designed and combined with the FCS-MPC system. Comparative experimental results validate the computational accuracy of the expected fundamental voltage. Compared with the model-based FW scheme, the proposed FW method has better robustness. Compared with the conventional FW scheme based on actual fundamental voltage closed loop, the proposed scheme has better dynamic performance.