通过mathematica求解矩阵时，提示不是有效变量，求大牛解答。
(*电流矩阵*)
aa = {{-Subscript[i, q]}, {Subscript[i, d]}};
(*电压矩阵*)
bb = {{\[CapitalDelta]V}, {V*Subscript[\[CapitalDelta]\[Theta], V]}} ;
(*转换矩阵*)
cc = {{Cos[Subscript[\[Theta],
i]], -Sin[Subscript[\[Theta], i]]}, {Sin[Subscript[\[Theta], i]],
Cos[Subscript[\[Theta], i]]}} ;
dd = {{\[CapitalDelta]i}, {i*Subscript[\[CapitalDelta]\[Theta], i]}};
ee = {{\[CapitalDelta]i}, {i*\[CapitalDelta]\[Phi]}};
Z = cc.dd;
Dimensions[Z];
(*角度关系*)
Subscript[\[CapitalDelta]\[Theta],
V] = \[CapitalDelta]\[Delta] - Subscript[\[CapitalDelta]\[Theta],
pll];
Subscript[\[CapitalDelta]\[Theta],
i] = \[CapitalDelta]\[Phi] - Subscript[\[CapitalDelta]\[Theta], pll];
Subscript[\[CapitalDelta]\[Theta], pll] =
Subscript[H, pll]*
V* \[CapitalDelta]\[Delta]/(1 + Subscript[H, pll]*V);
0 == s*Subscript[H, pll]*Subscript[L, f]*V *
Subscript[\[CapitalDelta]\[Theta], V]*aa + (1 - Subscript[G, ff])*
bb + (Subscript[H, i] + s*Subscript[L, f])*cc.dd;
(*根据关系式求解电流和电压的关系*)
NSolve[0 ==
s*Subscript[H, pll]*Subscript[L, f]*V *
Subscript[\[CapitalDelta]\[Theta], V]*aa + (1 - Subscript[G, ff])*
bb + (Subscript[H, i] + s*Subscript[L, f])*
cc.dd, {{\[CapitalDelta]i}, {i*\[CapitalDelta]\[Phi]}}]

唉
tieba.baidu.com/p/6727303693