CREATE TABLE table_17591 ("Year" FLOAT, "Mens singles" TEXT, "Womens singles" TEXT, "Mens doubles" TEXT, "Womens doubles" TEXT, "Mixed doubles" TEXT)

How many times did Niels Christian Kaldau win the men's single and Pi Hongyan win the women's single in the same year?
SELECT COUNT("Year") FROM table_17591 WHERE "Mens singles" = 'Niels Christian Kaldau' AND "Womens singles" = 'Pi Hongyan'
SELECT COUNT("Year") FROM "table_17591" WHERE "Mens singles" = 'Niels Christian Kaldau' AND "Womens singles" = 'Pi Hongyan'