Even at an unknown power point, control by estimated maximum power point is carried out. An MPPT controller (20) includes: a measurement data acquiring section (31), which acquires an amount of solar radiation and/or a temperature from a pyrheliometer (14)/a thermometer (15), and which acquires an electric current value and/or a voltage value from an ammeter (17a)/a voltmeter (17b); a search control section (34), which searches for a maximum power point by controlling a power point of an array (10) by controlling an inverter (18); an estimate equation computing section (32), which estimates an estimate equation (A) that holds between the amount of solar radiation and a maximum operating current value and/or an estimate equation (B) that holds between the temperature and a maximum operating voltage value; and an MPP estimating section 35, which estimates a maximum power point at an amount of solar radiation or at a temperature by using the estimate equation (A) or (B).
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