Control device and power conversion system

Patent metadata

Field	Value
Publication number	US-12416935-B2
Application number	US-202218700365-A
Country	US
Kind code	B2
Filing date	Oct 5, 2022
Priority date	Oct 5, 2022
Publication date	Sep 16, 2025
Grant date	Sep 16, 2025

Abstract

A control device includes a modulation rate calculator configured to calculate a modulation rate based on a DC voltage on a DC side an, a limiter configured to update a DC voltage command lower bound limiter based on the lower bound limiter operation value; a maximum power point tracking controller configured to calculate a first DC voltage command value and determine a second DC voltage command value based on the calculated first DC voltage command value and the DC voltage command lower bound limiter set to the limiter, and an inverter controller configured to control an inverter of the power conversion system based on the second DC voltage command value.

First claim

The invention claimed is:

1. A control device in a photovoltaics power conversion system connected to a solar panel on a DC side, the control device comprising:
a modulation rate calculator configured to calculate a modulation rate based on a DC voltage on a DC side of the power conversion system and a grid voltage root mean square value on an AC side of the power conversion system;
a limiter adjuster configured to calculate a lower bound limiter operation value based on a predetermined lower bound limiter set value, the grid voltage root mean square value, and a predetermined rated value in accordance with the modulation rate calculated by the modulation rate calculator;
a limiter configured to update a DC voltage command lower bound limiter based on the lower bound limiter operation value calculated by the limiter adjuster;
a maximum power point tracking controller configured to calculate a first DC voltage command value by performing maximum power point tracking control based on DC power generated by the solar panel and determine a second DC voltage command value based on the calculated first DC voltage command value and the DC voltage command lower bound limiter set to the limiter; and
an inverter controller configured to control an inverter of the power conversion system based on the second DC voltage command value determined by the maximum power point tracking controller.

2. The control device according to claim 1 , wherein when the lower bound limiter operation value is calculated by the limiter adjuster, the limiter updates the DC voltage command lower bound limiter based on the lower bound limiter operation value calculated by the limiter adjuster while being out of synchronization with the maximum power point tracking control by the maximum power point tracking controller.

3. The control device according to claim 1 , wherein the limiter adjuster includes an upper-lower bound limiter configured to limit upper and lower bound values of the lower bound limiter operation value so that the lower bound limiter operation value does not become smaller than the predetermined lower bound limiter set value at least.

4. The control device according to claim 1 , wherein the maximum power point tracking controller determines the value of the DC voltage command lower bound limiter to be the second DC voltage command value when the calculated first DC voltage command value is smaller than the value of the DC voltage command lower bound limiter set to the limiter, and the maximum power point tracking controller determines the first DC voltage command value to be the second DC voltage command value when the calculated first DC voltage command value is equal to or larger than the value of the DC voltage command lower bound limiter set to the limiter.

5. A photovoltaics power conversion system connected to a solar panel at which power generation is performed by sunlight, the photovoltaics power conversion system comprising:
an inverter configured to convert DC power generated by the solar panel into AC power; and
the control device according to claim 1 .

6. A control device in an energy-storage-system power conversion system connected to an energy storage system on a DC side, the control device comprising:
a modulation rate calculator configured to calculate a modulation rate based on a DC voltage on a DC side of the power conversion system and a grid voltage root mean square value on an AC side of the power conversion system;
a limiter adjuster configured to calculate an operation range lower bound voltage operation value based on a predetermined operation range lower bound voltage set value, the grid voltage root mean square value, and a predetermined rated value in accordance with the modulation rate calculated by the modulation rate calculator;
a limiter configured to update the operation range lower bound voltage based on the operation range lower bound voltage operation value calculated by the limiter adjuster;
a DC voltage operation range detector configured to compare the DC voltage on the DC side of the power conversion system and the operation range lower bound voltage set to the limiter and determine whether the DC voltage is smaller than the operation range lower bound voltage; and
an operation controller configured to stop an inverter of the power conversion system when it is determined by the DC voltage operation range detector that the DC voltage is smaller than the operation range lower bound voltage.

7. The control device according to claim 6 , wherein when the operation range lower bound voltage operation value is calculated by the limiter adjuster, the limiter updates the operation range lower bound voltage based on the operation range lower bound voltage operation value calculated by the limiter adjuster while being out of synchronization with control by the DC voltage operation range detector.

8. The control device according to claim 6 , wherein the limiter adjuster includes an upper-lower bound limiter configured to limit upper and lower bound values of the operation range lower bound voltage operation value so that the operation range lower bound voltage operation value does not become smaller than the predetermined operation range lower bound voltage set value at least.

9. An energy-storage-system power conversion system connected to an energy storage system capable of charging and discharging electric power, the energy-storage-system power conversion system comprising:
an inverter configured to convert DC power supplied from the energy storage system into AC power; and
the control device according to claim 6 .

Assignees

• Toshiba Mitsubishi Electric Industrial Systems Corp

Inventors

• Katsukura Tomoya
• Tawada Yoshihiro
• Fukasawa Issei
• Kinoshita Masahiro

Classifications

• H02J2101/25

  involving maximum power point tracking control for photovoltaic sources · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02M7/5395

  by pulse-width modulation · CPC title

• H02J3/381

  Dispersed generators · CPC title

• H02J7/35

  with light sensitive cells · CPC title