CN-122026737-A - Bus voltage control method and device of photovoltaic inverter

CN122026737ACN 122026737 ACN122026737 ACN 122026737ACN-122026737-A

Abstract

The application relates to a bus voltage control method and device of a photovoltaic inverter, wherein the method comprises the steps of obtaining a photovoltaic working point voltage and a bus voltage of the photovoltaic inverter, wherein the inverter comprises DCDC and DCAC which are connected in series, the bus voltage is a voltage on a direct current capacitor between the DCDC and the DCAC, the photovoltaic working point voltage is a voltage generated by a photovoltaic module and input to the DCDC, determining a duty ratio based on the photovoltaic working point voltage and the bus voltage, wherein the duty ratio represents the proportion of the conduction time of a switching tube in the DCDC in one switching period to the total period, comparing the duty ratio with a preset threshold value, and determining whether the bus voltage is regulated according to a comparison result so that the duty ratio is in a preset range. According to the application, the problem of low reliability of the inverter caused by the fact that the photovoltaic voltage is at different values so that the duty ratio is not in a proper interval in order to track the maximum power in the prior art is solved.

Inventors

MAO CHAOYANG
HUANG MENG
TANG WENQIANG
Ning Jiehua
NI ZIRONG

Assignees

珠海格力电器股份有限公司

Dates

Publication Date: 20260512
Application Date: 20251229

Claims (10)

1. A bus voltage control method of a photovoltaic inverter, comprising: Obtaining a photovoltaic working point voltage of a photovoltaic module and a bus voltage of an inverter, wherein the inverter comprises a direct current-direct current converter (DCDC) and a direct current-alternating current converter (DCAC) which are connected in series, the bus voltage is a voltage on a direct current capacitor between the DCDC and the DCAC, and the photovoltaic working point voltage is a voltage generated by the photovoltaic module and input to the DCDC; Determining a duty cycle based on the photovoltaic operating point voltage and the bus voltage, wherein the duty cycle characterizes a ratio of a conduction time of a switching tube in the DCDC in one switching period to a total period; Comparing the duty ratio with a preset threshold value, and determining whether to adjust the bus voltage according to the comparison result so that the duty ratio is within a preset range.
2. The method of claim 1, wherein comparing the duty cycle to a preset threshold and determining whether to adjust the bus voltage to bring the duty cycle within a preset range based on the comparison result comprises: comparing the duty ratio with a first preset threshold value and a second preset threshold value respectively, wherein the first preset threshold value is larger than the second preset threshold value; And when the comparison result is that the duty ratio is larger than the first preset threshold value or the duty ratio is smaller than the second preset threshold value, adjusting the bus voltage so that the duty ratio is within a preset range, wherein the bus voltage is increased to increase the duty ratio when the duty ratio is larger than the first preset threshold value, and the bus voltage is decreased to decrease the duty ratio when the duty ratio is smaller than the second preset threshold value.
3. The method according to claim 2, wherein, in the case that the comparison result is that the duty ratio is greater than the first preset threshold or the duty ratio is less than a second preset threshold, adjusting the bus voltage so that the duty ratio is within a preset range includes: And when the comparison result is that the duty ratio is continuously larger than the first preset threshold value in the first preset time period or the duty ratio is continuously smaller than the second preset threshold value in the first preset time period, adjusting the bus voltage so that the duty ratio is in a preset range.
4. A method according to claim 3, wherein, in case the comparison result is that the duty cycle is continuously greater than the first preset threshold value for a first preset period of time, adjusting the bus voltage so that the duty cycle is within a preset range comprises: under the condition that the comparison result is that the duty ratio is larger than the first preset threshold value, the bus voltage is increased from the current level voltage to the upper level voltage, wherein the bus voltage runs at preset voltage, the preset voltage comprises preset multi-level voltage, the voltage corresponding to the higher level is larger, the comparison result is counted once every second preset time length, the second preset time length is smaller than the first preset time length, and the value of N is a positive integer larger than 1; And after the bus voltage is increased from the current level voltage to the previous level voltage, continuously counting the comparison result, continuously executing the operation of increasing the bus voltage if the comparison result is still that the duty ratio is larger than the first preset threshold value, and stopping adjusting the bus voltage if the comparison result is that the duty ratio is smaller than the first preset threshold value and larger than the second preset threshold value.
5. A method according to claim 3, wherein, in case the comparison result is that the duty cycle is continuously smaller than the second preset threshold value for a first preset period of time, adjusting the bus voltage so that the duty cycle is within a preset range comprises: Under the condition that the comparison result is that the duty ratio is smaller than the second preset threshold value, the bus voltage is reduced from the current level voltage to the next level voltage, wherein the bus voltage operates with preset voltage, the preset voltage comprises preset multilevel voltages, the voltage corresponding to the higher level is larger, the comparison result is counted once every second preset time period, the second preset time period is smaller than the first preset time period, and the value of N is a positive integer larger than 1; and after the bus voltage is reduced from the current level voltage to the next level voltage, continuing to count the comparison result, if the comparison result is still that the duty ratio is smaller than the second preset threshold value, continuing to execute the operation of increasing the bus voltage, and if the comparison result is that the duty ratio is smaller than the first preset threshold value and larger than the second preset threshold value, stopping adjusting the bus voltage.
6. The method according to claim 4 or 5, characterized in that the method further comprises: And under the condition that the comparison result is counted that the duty ratio is smaller than the first preset threshold value and larger than the second preset threshold value, returning the value of N to zero and counting the comparison result again.
7. The method of claim 1, wherein determining a duty cycle based on the photovoltaic operating point voltage and the bus voltage comprises: determining a ratio of the photovoltaic operating point voltage to the bus voltage; the ratio of 1 minus the ratio is determined as the duty cycle.
8. A bus voltage control device of a photovoltaic inverter, comprising: The photovoltaic module is used for obtaining photovoltaic working point voltage of the photovoltaic module and bus voltage of the photovoltaic inverter, wherein the inverter comprises a direct current-direct current converter DCDC and a direct current-alternating current converter DCAC which are connected in series, the bus voltage is voltage on a direct current capacitor between the DCDC and the DCAC, and the photovoltaic working point voltage is voltage generated by the photovoltaic module and input to the DCDC; a determining module, configured to determine a duty cycle based on the photovoltaic operating point voltage and the bus voltage, where the duty cycle characterizes a ratio of a conduction time of a switching tube in the DCDC in one switching period to a total period; And the first processing module is used for comparing the duty ratio with a preset threshold value, and determining whether to adjust the bus voltage according to a comparison result so that the duty ratio is in a preset range.
9. The electronic equipment is characterized by comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory are in communication with each other through the communication bus, the memory is used for storing a computer program, and the processor is used for realizing the bus voltage control method of the photovoltaic inverter according to any one of claims 1-7 when the computer program is executed.
10. A storage medium having stored thereon a computer program, which when executed by a processor, implements the busbar voltage control method of a photovoltaic inverter of any of claims 1-7.

Description

Bus voltage control method and device of photovoltaic inverter Technical Field The application relates to the field of inverter control, in particular to a bus voltage control method and device of a photovoltaic inverter. Background The photovoltaic inverter is an inverter applied to a solar power generation system, is an important component in the photovoltaic power generation system, the output power of the photovoltaic inverter directly influences the quantity of generated energy, the current string type photovoltaic inverter is composed of two modules, namely a direct current-direct current converter (Direct Current to Direct Current Converter, DCDC) +a direct current-alternating current converter (Direct Current to Alternating Current Converter, DCAC), the DCDC module is used for realizing maximum power point tracking, the DCAC is used for inverting and surfing the Internet, the DCDC output voltage is the input voltage of the DCAC, and the DC can be controlled relatively independently through bus capacitance decoupling. In practical applications, the bus voltage and the photovoltaic operating point voltage together determine the operating duty cycle of the DCDC. When the illumination intensity and the environment temperature of the photovoltaic group string number, sunrise, sunset, cloudiness and the like are different, the attribute of the photovoltaic power generation can be changed. In order to track the maximum power, the photovoltaic voltage is at different values, so that the duty ratio is not in a proper interval, and the photovoltaic inverter has larger current ripple or spike voltage, so that the reliability of the inverter is reduced. Disclosure of Invention The application provides a bus voltage control method and device of a photovoltaic inverter, which are used for solving the problem that in the prior art, in order to track the maximum power, the photovoltaic voltage is in different values so that the duty ratio is not in a proper interval, and the reliability of the inverter is lower. The application provides a bus voltage control method of a photovoltaic inverter, which comprises the steps of obtaining a photovoltaic working point voltage of a photovoltaic module and a bus voltage of the photovoltaic inverter, wherein the inverter comprises a direct current-direct current converter (DCDC) and a direct current-alternating current converter (DCAC) which are connected in series, the bus voltage is a voltage on a direct current capacitor between the DCDC and the DCAC, the photovoltaic working point voltage is a voltage which is generated by the photovoltaic module and is input into the DCDC, determining a duty ratio based on the photovoltaic working point voltage and the bus voltage, wherein the duty ratio represents the ratio of the conduction time of a switching tube in the DCDC to the total period in one switching period, comparing the duty ratio with a preset threshold value, and determining whether to adjust the bus voltage according to a comparison result so that the duty ratio is in a preset range. Optionally, comparing the duty ratio with a preset threshold value, and determining whether to adjust the bus voltage to enable the duty ratio to be in a preset range according to a comparison result comprises comparing the duty ratio with a first preset threshold value and a second preset threshold value respectively, wherein the first preset threshold value is larger than the second preset threshold value, adjusting the bus voltage to enable the duty ratio to be in a preset range when the duty ratio is larger than the first preset threshold value or smaller than the second preset threshold value as a result of the comparison, and increasing the bus voltage to increase the duty ratio when the duty ratio is larger than the first preset threshold value and decreasing the bus voltage to decrease the duty ratio when the duty ratio is smaller than the second preset threshold value. Optionally, when the comparison result is that the duty ratio is greater than the first preset threshold value or the duty ratio is smaller than the second preset threshold value, the bus voltage is adjusted so that the duty ratio is within a preset range, and when the comparison result is that the duty ratio is continuously greater than the first preset threshold value within a first preset duration or the duty ratio is continuously smaller than the second preset threshold value within the first preset duration, the bus voltage is adjusted so that the duty ratio is within the preset range. Optionally, when the comparison result is that the duty ratio is continuously greater than the first preset threshold value within a first preset duration, the bus voltage is adjusted to enable the duty ratio to be within a preset range, the method comprises the steps of continuously counting the bus voltage from a current level voltage to a previous level voltage when the comparison result is that the duty ratio is greater than