Cfrgtkky

I have written the attached optimization problem. But, as it can be seen that equations (1c)-(1j) are very close to one another. I want to add a small space between each equation. What is the neatest way to do this?

Thanks a lot!!

documentclass[review,12pt]{elsarticle}

usepackage{array}

usepackage{amsmath}

usepackage{amssymb}

usepackage{setspace}

usepackage{subfigure}

DeclareMathOperator{Tr}{Tr}

DeclareMathOperator{rank}{rank}

DeclareMathOperator{diag}{diag}

usepackage[utf8]{inputenc}

usepackage[T1]{fontenc}

usepackage{footnote}

makesavenoteenv{tabular}

makesavenoteenv{table}

newcommand{tightermath}{%

setlength{thickmuskip}{.3thickmuskip}

setlength{medmuskip}{.3medmuskip}

setlength{thinmuskip}{.3thinmuskip}}

onehalfspacing

begin{document}

begin{figure}[h]

begin{subequations}

    setlengthparindent{0pt}

    rule{columnwidth}{1pt}

    textbf{M2:} textbf{SDP-based OPF} \

    rule[1ex]{columnwidth}{1pt}       

    vspace*{-1.5baselineskip} 

    begin{flalign}

    mathbf{M2: } underset{Psi}{mathbf{minimize}} f(Psi)&&& 

    end{flalign}       

    vspace*{-1.5baselineskip}     

    begin{flalign}

    &mathbf{variable:}hspace{1em}mathbf{W}&\

    & hspace{5.7em}P_{g_k}^varphi, Q_{g_k}^varphi hspace{2em}forall varphi in eta_{k}, forall k in N & nonumber

    end{flalign}   

    $mathbf{subject}$ $mathbf{to:}$ 

    begin{flalign}

    & Tr(mathbf{Psi}_{k,nw_p}^varphi mathbf{W}) + P_{l_k}^upsilon = 0, hspace{11.7em}forall varphi in eta_k, upsilon in chi_k, k in Nbackslash G label{eq:PBL2}\ 

    & Tr(mathbf{Psi}_{k,nw_q}^varphi mathbf{W}) + Q_{l_k}^upsilon-y_{c_k}^upsilon  Tr(mathbf{Psi}_{k,nw_v}^varphimathbf{W}) = 0, hspace{3em}forall varphi in eta_k, upsilon in chi_k, k in Nbackslash G label{eq:QBL2} \

    & underline{P}_{g_i} leq Tr(mathbf{Psi}_{i,nw_p}^varphi mathbf{W}) {+} P_{l_i}^upsilon leq overline{P}_{g_i}, hspace{8.8em}forall varphi in eta_i, upsilon in chi_i, i in G label{eq:PBG2}\

    & underline{Q}_{g_i} leq Tr(mathbf{Psi}_{i,nw_q}^varphi mathbf{W}) {+} Q_{l_i}^upsilon leq overline{Q}_{g_i}, hspace{8.8em}forall varphi in eta_i, upsilon in chi_i, i in G label{eq:QBG2}\

    & (underline{V}_k)^2 leq Tr(mathbf{Psi}_{k,nw_v}^varphi mathbf{W}) leq (overline{V_k})^2, hspace{9.0em}forall varphi in eta_k, k in N^+ label{eq:Vol2} \

    & [mathbf{W}]_{eta_0 times eta_0} = mathbf{V}_0 mathbf{V}_0^H \

    & mathbf{W} succeq 0, \

    & rank(mathbf{W}) = 1 label{rank_con}

    end{flalign}

    rule[1ex]{columnwidth}{1pt}

end{subequations}

end{figure}

end{document}