Electrical Storage System Ripple Current Masking
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Solution Overview
Problem
Existing techniques for detecting current and voltage values in electrical storage devices face reliability issues due to ripple current, leading to inaccurate calculations of internal resistance and potential erroneous determination of sensor failures, especially when the frequency difference between motor rotation speed and step-up circuit operation is small.
Innovation Solution
An electrical storage system that includes sensors to detect current and voltage values, with a controller that masks these values when the frequency difference between the motor rotation speed and step-up circuit operation is below a threshold, preventing the use of unreliable data for calculations and reducing the risk of erroneous processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the detected current value and voltage value are used for calculating internal resistance, then the calculation can be performed continuously, but the reliability of the calculation deteriorates when ripple current is present due to frequency matching between motor rotation and step-up circuit operation
Solution Approach 1:
The controller preliminarily determines whether the frequency difference between the current value and voltage value is smaller than a threshold before performing the internal resistance calculation. This preliminary check prevents unreliable calculations from being performed in the first place, rather than attempting to correct errors after they occur.
Solution Approach 2:
When the frequency difference is smaller than the threshold, the controller extracts and excludes the detected current value and voltage value from the calculation process. This separates the unreliable data from the calculation, allowing the system to maintain calculation continuity using only reliable data points while avoiding contamination from ripple current effects.
2Quantity of substance
If sensor values are used during resonance conditions, then data utilization is maximized, but measurement precision deteriorates due to ripple current induced variations
Solution Approach 1:
The controller performs a preliminary determination of the frequency difference between the current value and voltage value before utilizing the sensor data. This advance check ensures that only data collected under stable conditions (frequency difference >= threshold) are used, preventing precision degradation while maximizing safe data utilization.
Solution Approach 2:
The frequency difference determination acts as an intermediary condition that mediates between data utilization and measurement precision. By introducing this intermediate check, the system can intelligently select which sensor values to use based on the resonance condition, thereby maintaining precision while utilizing available data.
3Device complexity
If the system monitors only motor rotation speed to detect ripple current, then the detection system remains simple, but the detection accuracy deteriorates because it does not account for step-up circuit switching frequency
Solution Approach 1:
The controller utilizes existing frequency information from both the motor rotation speed and the step-up circuit switching operation to determine the frequency difference. This multi-functional approach uses available system parameters for a dual purpose: normal control and ripple current detection, improving detection accuracy without adding dedicated detection hardware.
Solution Approach 2:
The system merges the frequency information from the motor rotation and step-up circuit switching into a single frequency difference determination. By combining these two frequency sources, the system achieves more accurate ripple current detection while maintaining relatively simple system architecture, as both frequency sources are already present in the system.
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 approach ensures reliable data usage by avoiding calculations based on unreliable sensor values during conditions of increased ripple current, thereby preventing erroneous resistance calculations and sensor failure determinations, and optimizing the use of detected values.
Implementation Method 1
a step-up circuit configured to step up an output voltage of the electrical storage device
Implementation Method 2
an inverter configured to convert a direct-current power, output from the step-up circuit, to an alternating-current power
Implementation Method 3
a motor configured to operate upon reception of an output power of the inverter
Data Source
AI summary
At least one of a current value and a voltage value of an electrical storage device which is charged and discharged is detected with the use of each of a plurality of sensors. A predetermined process is executed on the basis of the detected values of the plurality of sensors The predetermined process is executed without using the detected values of the sensors in the predetermined process when a difference between a frequency of each of the detected values, which varies with a rotation speed of a motor that operates upon reception of an output power of the electrical storage device, and a resonance frequency of a step-up circuit, which varies with operation of the step-up circuit that steps up an output voltage of the electrical storage device and outputs the stepped-up electric power to the motor, is smaller than a threshold.