Maximum power point tracking method and device, and photovoltaic power generation system

Patent metadata

Field	Value
Publication number	US-9354652-B2
Application number	US-201514597460-A
Country	US
Kind code	B2
Filing date	Jan 15, 2015
Priority date	Jun 20, 2014
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

A maximum power point tracking method, device and a photovoltaic power generation system. The maximum power point tracking method involves sampling a present voltage and a present current of a photovoltaic array and obtaining a present power based on the present voltage and the present current. The maximum power point tracking using a difference between the present power and a power for a previous sampling time as a present perturbation power, and based on a ratio of the present perturbation power to a perturbation power for a previous sampling time obtain a gradient perturbation voltage step ratio. Further, the maximum power point tracking obtains a perturbation voltage step based on the gradient perturbation voltage step ratio and the voltage difference between the present voltage and the voltage for the previous sampling time, and control an output voltage based on the perturbation voltage step.

First claim

The invention claimed is:

1. A maximum power point tracking method, for enabling a photovoltaic array to operate at maximum power point, comprising:
step a: sampling a present voltage and a present current of the photovoltaic array;
step b: obtaining a present power based on the present voltage and the present current sampled at a present sampling time;
step c: using a difference between the present power and a power for a previous sampling time as a present perturbation power, and obtaining a present gradient perturbation voltage step ratio based on a ratio of the present perturbation power to a perturbation power for a previous sampling time, wherein the power for the previous sampling time is obtained based on a voltage for the previous sampling time and a current for the previous sampling time which are sampled at the previous sampling time, and the perturbation power for the previous sampling time is a difference between the power for the previous sampling time and a power for a sampling time immediately before the previous sampling time;
step d: obtaining a perturbation voltage step based on the present gradient perturbation voltage step ratio and a voltage difference between the present voltage and the voltage for the previous sampling time; and
step e: controlling an output voltage of the photovoltaic array based on the perturbation voltage step.

2. The maximum power point tracking method of claim 1 , wherein:
the step a specifically comprises step 1: sampling the output voltage and an output current of the photovoltaic array for the k th sampling time so as to obtain an output voltage U k and an output current I k for the k th sampling time, wherein k is a natural number, U k is the present voltage, and I k is the present current;
the step b specifically comprises step 2: calculating an output power P k for the k th sampling time, wherein P k =U k ×I k , and P k is the present power;
the step c specifically comprises:
step 3: calculating a perturbation voltage step ΔU k and a perturbation power ΔP k for the k th sampling time, wherein ΔU k U k −U k−1 , ΔP k ×P k −P k−1 , U k−1 is the voltage for the previous sampling time, P k−1 is the power for the previous sampling time, P k−1 =U k−1 ×I k−1 , and I k−1 is the current for the previous sampling time, and
step 4: calculating a perturbation voltage step ratio r corresponding to the k th sampling time, wherein k=ΔP k /ΔP k−1 , and ΔP k−1 is a perturbation power for the k−1 th sampling time;
the step d specifically comprises step 5: calculating a perturbation voltage step ΔU k+1 corresponding to k+1 th sampling, wherein ΔU k+1 =|k×ΔU k |;
the step e specifically comprises step 6: based on the perturbation voltage step ΔU k+1 , obtaining Udc_ref k+1 , which is a reference voltage for a DC bus of an inverter or a given signal for a voltage close loop control of a DC/DC converter in the inverter, so as to control the output voltage of the photovoltaic array, wherein:

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Udc_ref k+1 is a reference voltage for the DC bus of the inverter corresponding to the k+1 th sampling or a given signal for the voltage close loop control of the DC/DC converter in the inverter corresponding to the k+1 th sampling, Udc_ref k is a reference voltage for the DC bus of the inverter corresponding to the k th sampling or a given signal for the voltage close loop control of the DC/DC converter in the inverter corresponding to the k th sampling, ΔU k+1 is a perturbation voltage step for the DC bus of the inverter corresponding to the k+1 th sampling or a given signal for the voltage close loop control of the DC/DC converter in the inverter corresponding to the k+1 th sampling, ΔU k is the perturbation voltage step corresponding to the k th sampling, and ΔP k is the perturbation power corresponding to the k th sampling; and

Assignees

• Boe Technology Group Co Ltd
• Beijing Boe Energy Technology Co Ltd

Inventors

• Li Jin
• Han Xiaoyan
• Zheng Ping
• He Jia

Classifications

• G05F1/67 Primary

  to the maximum power available from a generator, e.g. from solar cell · CPC title

• Y02E10/58

  Cross-Sectional Technologies · mapped topic

• G05F1/46

  wherein the variable actually regulated by the final control device is DC (G05F1/625 takes precedence) · CPC title

• Y02E10/56

  Power conversion systems, e.g. maximum power point trackers · CPC title