Power Control System for Grid-Connected Energy Storage
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Solution Overview
Problem
Conventional power control systems experience operational disruptions and instability when switching modes, leading to instantaneous power variations that can affect the load or power grid stability.
Innovation Solution
A power control system incorporating a DC/DC converter, a DC/AC converter, a power smoothing element, flow power detection, reverse flow power detection, and a control device that adjusts output commands based on detected power and voltage to maintain stability and follow power command values, suppressing voltage variations and reverse flow power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If operation mode switching is implemented in conventional power control systems, then power storage control flexibility is improved, but instantaneous power variation and system instability occur
Solution Approach 1:
The patent introduces a power smoothing element (capacitor) as an intermediary component between the DC/DC converter and DC/AC converter. This capacitor absorbs instantaneous power variations during operation mode switching, preventing direct transmission of power fluctuations to the load and grid, thereby maintaining system stability while enabling flexible mode transitions.
Solution Approach 2:
The control device performs beforehand cushioning by detecting operation mode switching signals in advance and generating corrected output commands that anticipate upcoming power variations. This proactive control adjusts converter outputs before instantaneous variations occur, preventing stability issues while maintaining control flexibility.
2Adaptability or versatility
If operation mode switching is implemented, then power management adaptability is improved, but time lag and response delay occur
Solution Approach 1:
The control device performs preliminary action by detecting operation mode switching signals and generating corrected output commands before the actual mode transition completes. This advance preparation ensures that power converter outputs are already adjusted when the transition occurs, eliminating time lag and achieving instantaneous response to mode changes.
3Reliability
If instantaneous power variation control is added, then grid stability is improved, but device complexity increases
Solution Approach 1:
The control device performs multiple functions using existing components: it detects operation mode switching signals, calculates corrected output commands based on converter output values and switching signals, and outputs corrected commands to both DC/DC and DC/AC converters. This multi-functional approach achieves grid stability without requiring separate dedicated control systems for each converter.
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 enables reliable charging or discharging of power storage devices without influencing load or grid stability, ensuring smooth operation and maintaining power grid stability during mode changes.
Implementation Method 1
a DC/DC converter (12) having a first input/output side connected to the power storage device (10) and causing the power storage device (10) to be charged or discharged through a bidirectional DC/DC power conversion operation
Implementation Method 2
a DC/AC converter (13) having a DC side connected to a second input/output side of the DC/DC converter and an AC side connected to a power grid (1), and performing bidirectional power conversion operation between DC and AC
Implementation Method 3
a power smoothing element (14) connected between the second input/output side of the DC/DC converter and the DC side of the DC/AC converter
Data Source
AI summary
In a power control system which connects power from the power storage device to a power grid and supplies power to a load, the power from the power storage device is connected to the load and the power grid via a DC/DC converter, a smoothing capacitor, and a DC/AC converter. By a first power control unit for controlling flow power of the power grid to be a power command value, and by a second power control unit for suppressing reverse flow power, an output power command for the DC/AC converter is generated, an output power command for the DC/DC converter is generated so that voltage of the smoothing capacitor becomes target voltage, and the output power command is corrected so as to suppress voltage variation in the smoothing capacitor.