PV Inverter Frequency Stabilization via Current Measurement
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Solution Overview
Problem
Photovoltaic generation systems face challenges in providing stable power due to fluctuations in solar irradiation, lacking the frequency adjustment capabilities of synchronous generators, which complicates system frequency stabilization when integrated with power systems.
Innovation Solution
A photovoltaic generation system incorporating a direct-current power supply, storage battery, electric power converter, voltage and current detectors, and a power generator characteristics computation unit that adjusts output voltage phase and magnitude to mimic synchronous generator behavior, enabling stable power supply by controlling effective power flow and frequency stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase angle correction and target voltage calculation are performed based on effective power and terminal voltage of the inverter power supply, then power flow control is achieved, but output voltage calculation accuracy deteriorates
Solution Approach 1:
The patent introduces a current detector as an intermediary measurement device to directly measure the output current of the inverter power supply. This measured current value serves as a more accurate basis for calculating output voltage compared to the indirect method using effective power and terminal voltage, thereby improving calculation accuracy while maintaining control functionality
Solution Approach 2:
The patent replaces the indirect electrical calculation method (based on effective power and voltage) with a direct current measurement approach. By substituting the calculation-based voltage determination with current measurement followed by voltage calculation, the system achieves higher precision in output voltage control
2Stability of the object's composition
If photovoltaic generation modules are combined with storage battery units to stabilize power output, then power fluctuation is reduced, but system frequency stabilization capability is lost
Solution Approach 1:
The patent changes the operational parameters of the inverter power supply by controlling its output voltage phase and frequency based on system frequency deviations. When system frequency drops, the inverter increases its output power by adjusting voltage parameters, thereby providing frequency stabilization capability while maintaining the power smoothing function of the storage battery system
Solution Approach 2:
The patent enables the photovoltaic-storage system to perform multiple functions: both power smoothing (reducing output fluctuations) and frequency stabilization (responding to system frequency changes). The inverter power supply acts as a multi-functional device that simultaneously manages power flow control and system frequency support
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively stabilizes power supply and frequency, allowing photovoltaic generation systems to operate similarly to synchronous generators, ensuring stable power delivery even when cooperating with traditional power systems.
Implementation Method 1
a photovoltaic generation module which generates direct current power by using the photovoltaic effect
Implementation Method 2
a storage battery which stores power
Implementation Method 3
an electric power converter which converts a direct current output from the photovoltaic generation module and the storage battery into an alternating current
Data Source
Figure 1
Figure 2A~3
Figure 4~5
AI summary
According to one embodiment, a photovoltaic generation system includes a direct-current power supply, which includes a photovoltaic 3 and a battery 4 to discharge a direct-current power to a converter 2, the converter 2 which supplies the converted power to a power system 1, a voltage detector 5 which detects a voltage at a connection point between the converter 2 and power system 1, a current detector 6 which detects a current output from the converter 2, an effective power detector 7 which detects effective power from a voltage value detected by the voltage detector 5 and a current value detected by the current detector 6, a rotor speed computation unit 10 which computes an angular frequency of the voltage output from the converter 2, based on an effective power value detected by the effective power detector 7, and an output target value of effective power, an electrical characteristics computation unit 21 which computes an output voltage target value of the converter 2, based on a current value detected by the current detector 6, and a set voltage value, and an angular frequency, and a power conversion controller 14 which controls the converter 2 according to the output voltage target value.