Power Converter Reactive Power Control for Grid Voltage Stability
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Solution Overview
Problem
The existing voltage control devices for power distribution grids, which rely on static var compensators, are expensive and inefficient in stabilizing fluctuations caused by decentralized power supply systems like solar power generation.
Innovation Solution
A power conversion system that includes an automatic voltage regulator, a power converter circuit, a voltage detection unit, a voltage target value generation unit, a correction unit, and a command unit to stabilize voltage fluctuations by outputting reactive power based on the deviation from a voltage control deadband, without the need for a static var compensator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static var compensator is used to suppress short-cycle voltage fluctuations, then voltage stability is improved, but the cost increases significantly
Solution Approach 1:
The patent replaces the expensive static var compensator with a low-cost inverter that can be integrated into existing solar power systems. The inverter uses standard power electronic components (IGBTs, capacitors, inductors) that are much cheaper than dedicated voltage compensation equipment, while achieving the same voltage stabilization function through reactive power control.
Solution Approach 2:
The inverter performs multiple functions: it converts DC from solar panels to AC for grid injection, and simultaneously provides voltage stabilization through reactive power compensation. This multi-functionality eliminates the need for separate voltage control equipment, reducing overall system cost while maintaining voltage stability.
2Reliability
If a static var compensator is deployed for voltage control, then voltage fluctuations are suppressed, but the device complexity increases
Solution Approach 1:
The patent combines the voltage control function with the existing inverter system. The inverter's control unit is enhanced to detect voltage deviations and adjust reactive power output accordingly, merging two functions (power conversion and voltage control) into a single integrated device, thereby reducing system complexity.
Solution Approach 2:
The inverter autonomously detects voltage fluctuations and adjusts its reactive power output without external control signals. The control unit continuously monitors grid voltage and automatically compensates for deviations, enabling the system to self-regulate and reduce operational complexity.
3Reliability
If reactive power compensation is implemented continuously, then voltage stability is maintained, but energy losses increase
Solution Approach 1:
The control unit implements reactive power compensation only when voltage deviations exceed a predetermined threshold. By periodically monitoring voltage and activating compensation only when necessary, the system maintains voltage stability while minimizing continuous energy losses associated with reactive power generation.
Solution Approach 2:
The system applies reactive power compensation partially - only to the extent needed to correct voltage deviations. Rather than continuous full-capacity compensation, the inverter adjusts reactive power output proportionally to the magnitude of voltage deviation, reducing unnecessary energy consumption.
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
This solution effectively stabilizes voltage fluctuations in power distribution grids interconnected with decentralized power supply systems, reducing the operational burden on step voltage regulators and extending their lifespan, while avoiding the high costs associated with static var compensators.
Implementation Method 1
a power converter circuit to convert a direct-current power output from the decentralized power supply into an alternating-current power, and output the alternating-current power to the power distribution grid
Implementation Method 2
a voltage detection unit to detect a voltage at a point of interconnection between the power converter circuit and the power distribution grid
Implementation Method 3
the power converter circuit to output a reactive power based on of a magnitude of the deviated amount of voltage
Data Source
AI summary
A power conversion device includes: a power converter circuit which converts a direct-current power, output from a decentralized power supply, into an alternating-current power, and outputs the alternating-current power to a power distribution grid; a voltage target value generation unit which removes a high-frequency variation from a root mean square of a voltage detected by a voltage detection unit to generate a voltage target value; a correction unit which corrects the voltage target value when the correction unit detects that the automatic voltage regulator has performed an action; and a command unit which, if the voltage at the point of interconnection detected by the voltage detection unit deviates from a voltage control deadband referenced to the voltage target value, commands the power converter circuit to output a reactive power based on a magnitude of the deviated amount of voltage.