Control Apparatus and Method of Senseless MPPT Control For Photovoltaic Power Generation System

• US 20080203994A1
• Filed: 03/03/2008
• Published: 08/28/2008
• Est. Priority Date: 05/09/2006
• Status: Active Grant

• Current Assignee: Chang WON National University Business Administration
• Original Assignee: Chang WON National University Business Administration
• Inventors: Park, Min Won
• Granted Patent: US 7,994,768 B2
• Time in Patent Office: Days
• US Class Current: 323/318
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

The present invention relates to a senseless MPPT control apparatus of a photovoltaic power generation system and a method thereof. The control apparatus includes a current transformer, an A/D converter, a new and old current detector, a new duty ratio detector, an old duty ratio detector, a new and old duty ratio comparator, first and second new and old current comparators, a duty ratio adder, a duty ratio subtractor and a PWM signal generator. A maximum output point of a solar battery cell is tracked by using only one feedback current flowing into a load. Further, feedback factors can be reduced to one. It is possible to simplify the construction of a control circuit and minimize tracking control failure.

Claims

1. A senseless MPPT control apparatus of a photovoltaic power generation system, comprising:

a current transformer for detecting an output current of a DC/DC converter, which DC/DC-converts an output voltage of a solar battery cell and inputs a converted voltage to a load;

an A/D converter for converting a load current, output as an analog signal from the current transformer, into a digital signal;

a new and old current detector for detecting a new current and an old current, respectively, which are introduced to the load, from current values output from the A/D converter, and storing the detected new current and the old current;

a new duty ratio detector for detecting a new duty ratio from output signals of a duty ratio adder and a duty ratio subtractor and storing the detected duty ratio;

an old duty ratio detector for detecting an old duty ratio from an output signal of a PWM signal generator and storing the detected duty ratio;

a new and old duty ratio comparator for comparing the output signal of the new duty ratio detector and the output signal of the old duty ratio detector;

first and second new and old current comparators for receiving a comparison result value of the new and old duty ratio comparator and the new current and the old current of the new and old current detector, comparing the new current and the old current when the new duty ratio is greater than the old duty ratio or the new duty ratio is smaller than the old duty ratio, and outputting output values corresponding to the comparison results to the duty ratio adder and the duty ratio subtractor, respectively;

the duty ratio adder for adding a duty ratio shift to the new duty ratio to produce a new duty ratio, if predetermined output signals are respectively input from the first and second new and old current comparators;

the duty ratio subtractor for subtracting the duty ratio shift from the new duty ratio to produce a new duty ratio, if predetermined output signals are respectively input from the first and second new and old current comparators; and

the PWM signal generator for, if the new duty ratio, which has been increased or decreased according to the new duty ratios output from the duty ratio adder and the duty ratio subtractor, is input through the new duty ratio detector, modulating (PWM) a pulse width of a control signal according to the duty ratio, and outputting the result to the old duty ratio detector or the DC/DC converter.

2. A senseless MPPT control method of a photovoltaic power generation system, comprising:

a step (S21) of allowing a new and old current detector, connected to the current transformer, to detect a current introduced to the load, and to store the detected current;

a step (S22) of detecting a PWM duty ratio that was used previously and a PWM duty ratio that is currently being used and storing the detected PWM duty ratios;

a step (S23) of determining whether the new duty ratio ND is greater than the old duty ratio OD;

a step (S24, S25) of, if as a result of the comparison, the new duty ratio ND is greater than the old duty ratio OD (Yes in step S23) or the new duty ratio ND is smaller than the old duty ratio OD (No in step S23), determining whether a new current NC is greater than an old current OC;

a step (S26, S28) of, if, as a result of the comparison, the new duty ratio is greater than the old duty ratio (ND>

OD) and the new current is greater than the old current (NC>

OC) or the new duty ratio is smaller than the old duty ratio (ND<

OD) and the new current is smaller than the old current (NC<

OC), adding a duty ratio shift ratio Δ

D to the new duty ratio ND (ND+Δ

D) to produce a new duty ratio;

a step (S27, S28) of, if, as a result of the comparison, the new duty ratio is greater than the old duty ratio (ND>

OD) and the new current is smaller than the old current (NC<

OC) or the new duty ratio is smaller than the old duty ratio (ND<

OD) and the new current is greater than the old current (NC>

OC), subtracting the duty ratio shift ratio Δ

D from the new duty ratio ND (ND+Δ

D) to produce a new duty ratio; and

a step (S29) of allowing the PWM signal generator to generate a PWM signal corresponding to the new duty ratio and to control the DC/DC converter.