Just delete the 2 first line of imports and add the following lines:

import { jsPDF } from 'jspdf';
import { autoTable } from 'jspdf-autotable';

autoTable(doc, { ... })

You can see an example here

Is working for me Angular 5.

To work with jspdf-autotable in angular 5, one must install jspdf and jspdf-autotable via npm

npm install jspdf --save
npm install @types/jspdf --save-dev
npm install jspdf-autotable --save

also add the jspdf and jspdf-autotable files to the scripts array in angular-cli.json

"scripts": [
"../node_modules/jspdf/dist/jspdf.min.js",
"../node_modules/jspdf-autotable/dist/jspdf.plugin.autotable.js"
],

and in component never import jspdf or jspdf-autotable just.

Forget about the following import.

    import * as jsPDF from 'jspdf'; 
    import 'jspdf-autotable';

Just use Before @Component:

declare var jsPDF: any;

Your component (related parts ):

declare var jsPDF: any;

@Component({
    selector: "energy-login",
    templateUrl: "./login.component.html",
    styleUrls: ["./login.component.scss"]
})

export class MyComponent implements OnInit {

    constructor() {}

    ngOnInit() {}

    downloadPDF() {

        let columns = ["ID", "Name", "Country"];
        let rows = [
            [1, "Shaw", "Tanzania"],
            [2, "Nelson", "Kazakhstan"],
            [3, "Garcia", "Madagascar"],
        ];

        let doc = new jsPDF('l', 'pt');
        doc.autoTable(columns, rows); // typescript compile time error
        doc.save('table.pdf');
        }
    }