CN-122001233-A - Power conversion device

Abstract

The invention provides a power conversion device (1) capable of realizing stable operation even if direct current power changes, which converts direct current power into alternating current power and outputs the alternating current power. A controller (18) of the power conversion device (1) calculates an active power command value (adder (105)) from a detected value of DC power (panel output detected value) and an active power correction command value. The controller (18) calculates a frequency command value (frequency command calculator (107)) of the alternating voltage based on the active power command value and the active power detection value. The controller (18) outputs PWM signals (an integrator (108), a voltage command arithmetic unit (109), and a PWM arithmetic unit (110)) based on the frequency command value. The controller (18) calculates an active power correction command value (DC voltage controller (104)) using a deviation between the DC voltage detection value and the DC voltage command value and a control gain corresponding to the DC power detection value.

Inventors

• Ju Chihui
• YOSHIDA Naomitsu
• Todo Masanori
• MATSUNAGA SHUNSUKE

Assignees

• 株式会社日立产机系统

Dates

Publication Date

20260508

Application Date

20250603

Priority Date

20241108

Claims (7)

1. 1. An electric power conversion device for converting direct current power into alternating current power and then outputting the alternating current power, which is characterized in that: has a controller, said controller, Calculating an active power command value based on the detected value of the direct current power and the active power correction command value, Calculating a frequency command value of the alternating voltage based on the active power command value and the active power detection value, A PWM signal is output based on the frequency command value, The active power correction command value is calculated using a deviation between a DC voltage detection value and a DC voltage command value and a control gain corresponding to the DC power detection value.
2. 2. The power conversion device according to claim 1, characterized in that: the controller has a gain adjuster that receives the detected value of the dc power as an input and outputs a gain adjustment command value for adjusting the control gain.
3. 3. The power conversion device according to claim 2, characterized in that: The gain adjuster outputs the gain adjustment instruction value that increases monotonically with an increase in the detected value of the direct current power.
4. 4. A power conversion apparatus according to claim 3, wherein: The gain adjuster has a positive lower limit value, and outputs the gain adjustment instruction value equal to or higher than the lower limit value.
5. 5. The power conversion device according to claim 4, wherein: An interface unit for outputting the input/output characteristics of the gain adjuster and the control gain, inputting instructions for changing the input/output characteristics and the control gain, The controller changes the input-output characteristics and the control gain according to the instruction.
6. 6. An electric power conversion device for converting direct current power into alternating current power and then outputting the alternating current power, which is characterized in that: A controller for calculating an active power correction command value by using a control gain corresponding to the detected value of the DC power, When the detected value of the direct current power rises, the rate of change of the difference between the detected value of the active power and the detected value of the direct current power rises.
7. 7. The power conversion device according to claim 6, wherein: when the detected value of the direct current power rises, the control gain rises, and the change rate of the difference value between the active power detected value and the detected value of the direct current power rises.

Description

Power conversion device Technical Field The present invention relates to a power conversion device. Background In order to achieve carbon neutralization, renewable energy sources such as sunlight are increasingly used. The proportion of synchronous generators predicted to be grid-connected to the power system is then reduced, while the proportion of inverters to grid-connect the renewable energy source to the power system is increased. Synchronous generators have a rotating body and have the ability to provide inertia to the power system, but conventional inverters do not have such an ability. Accordingly, if the proportion of the inverter connected to the power system increases, there is a concern that the inertia of the power system is insufficient, the system frequency is liable to vary, and the power system becomes unstable. Thus, the concept of using an inverter to control virtual inertia that simulates the ability to provide inertia to the power system is proposed. An inverter having a capability of providing virtual inertia to an electric power system is attracting attention, and such an inverter is called a system-formed inverter (grid-formed inverter). As an example of such a system-shaped inverter, patent document 1 is known. Patent document 1 shows an example of a system-formed inverter having a dc power supply in a dc circuit. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2024-36973 Disclosure of Invention Problems to be solved by the invention However, in the case of applying the system-formed inverter to solar power generation, when an unstable dc power source such as a solar panel is provided in the dc circuit, the dc voltage of the system-formed inverter is difficult to maintain stable, and thus there is a problem in that it is difficult to perform stable operation of the system-formed inverter. When unbalance occurs between the power input from the solar panel to the dc portion of the system-formed inverter and the power output from the system-formed inverter to the power system, the dc voltage of the system-formed inverter fluctuates according to the unbalance amount. As a result, if the variation in the dc voltage is large, the system-formed inverter may be stopped due to the dc overvoltage or the dc undervoltage. In general, in a solar-light-oriented inverter, MPPT (maximum power point tracking) control is applied to maximize generated power, but such control is difficult to be applied when the dc voltage fluctuates. As described above, the solar panel is an unstable power source, and the reason for this is mainly that the illuminance of the solar light irradiated to the solar panel is liable to vary. When weather or the like changes sharply, the illuminance of sunlight may change in a short time. When the illuminance of sunlight changes, the output characteristics of the solar panel change, and the stability of the dc voltage also changes due to the influence of the change. If the inverter obtains information on the illuminance of sunlight, the control of the dc voltage can be adjusted in accordance with the change in the illuminance of sunlight, but since a sensor for detecting the illuminance of sunlight and the inverter are required to obtain the illuminance of sunlight in real time, it is actually difficult to adjust the control of the dc voltage in accordance with the change in the illuminance of sunlight. The invention aims to provide a device capable of realizing stable operation even if direct current power changes. Means for solving the problems In order to achieve the above object, the present invention provides a power conversion device for converting dc power into ac power and outputting the ac power, comprising a controller for calculating an active power command value from a detected value of the dc power and an active power correction command value, calculating a frequency command value of an ac voltage from the active power command value and the active power detected value, outputting a PWM signal based on the frequency command value, and calculating the active power correction command value using a deviation between the detected value of the dc voltage and the dc voltage command value and a control gain corresponding to the detected value of the dc power. Effects of the invention According to the present invention, stable operation can be realized even if the dc power is changed. The problems, configurations, and effects other than those described above will be described by the following description of the embodiments. Drawings Fig. 1 shows a configuration of a first embodiment of a power conversion device for solar power generation. Fig. 2 shows an example of the output characteristics of the solar panel. Fig. 3 shows an example of the output characteristics of the frequency command arithmetic unit. Fig. 4 shows an example of the output characteristics of the gain adjuster. Fig. 5 shows a configuration example of the