Separated DC Metering for Tamper-Resistant EV Charging Billing
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Solution Overview
Problem
Current electrical vehicle charging stations lack accurate and reliable measurement of actual power consumption for billing purposes, requiring a solution that is easy to implement, install, and manufacture, while addressing mechanical, thermal, and system integration constraints.
Innovation Solution
A DC meter system comprising a meter unit and a separate sensor unit connected via an interconnection cable, with the sensor unit measuring current and voltage on the DC power supply lines and transmitting encrypted data to the meter unit for power computation, featuring microprocessors with ADCs for signal conversion and secure communication, and a user interface for data output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single integrated meter unit is used, then device complexity is reduced, but measurement precision and reliability deteriorate due to potential manipulation and inaccurate power consumption measurement
Solution Approach 1:
The meter system is divided into separate functional units: a sensor unit for measuring voltage and current on power lines, and a meter unit for processing measurements and billing. This segmentation prevents manipulation by physically isolating the measurement function from the processing function, while maintaining measurement precision through dedicated sensor hardware.
Solution Approach 2:
An interconnection cable serves as an intermediary between the sensor unit and meter unit, transmitting encrypted measurement data. This intermediary connection allows the system to maintain separation of functions while enabling secure data exchange, preventing direct manipulation of measurement circuits.
2Reliability
If the sensor unit is integrated with the meter unit, then ease of manufacture is improved, but reliability and security against manipulation deteriorate
Solution Approach 1:
The system separates the sensor unit (with voltage and current sensors) from the meter unit (with processor and display), improving reliability by isolating the measurement function from potential manipulation points. While this increases manufacturing steps, it enables specialized production of each unit type.
Solution Approach 2:
The sensor unit design with separate voltage and current sensors can be universally applied to different charging station configurations and power line arrangements, maintaining ease of manufacture through standardized sensor modules while ensuring reliable measurements across various applications.
3Reliability
If data transmission is unencrypted, then device complexity is reduced, but security and protection against manipulation deteriorate
Solution Approach 1:
The interconnection cable acts as a secure intermediary channel, transmitting encrypted data between sensor and meter units. This intermediary encryption layer protects measurement data from manipulation during transmission without requiring complex security systems at each endpoint.
Solution Approach 2:
The system changes the parameter of data transmission from unencrypted to encrypted form, enhancing security against manipulation. The encryption transforms the data representation while maintaining transmission functionality, adding security without fundamentally changing the communication architecture.
4Measurement precision
If sampling frequency is increased, then measurement precision is improved, but use of energy and processing requirements worsen
Solution Approach 1:
The system optimizes the sampling frequency parameter to achieve sufficient measurement precision for billing purposes without excessive energy consumption. By selecting an appropriate sampling rate (not maximum possible), the system balances accuracy requirements with energy efficiency in the sensor unit's microprocessor operations.
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 solution provides accurate, reliable, and secure measurement of power consumption, reducing the risk of manipulation and enhancing the ease of installation and manufacturing, while ensuring secure communication and tamper-proofing, thus enabling precise billing and efficient energy management.
Implementation Method 1
The sensor unit further comprises a microprocessor with analog to digital convertors (ADC) for converting the received analog voltage measurement and current measurement signals to digital signals
Data Source
Figure 1
Figure 2
Figure 3a~3d
AI summary
A DC meter (1) for an electrical vehicle charging station having a pair of DC power supply lines (27a, 27b) extending from a charging station controller (40) to an electrical vehicle connector (28), the DC meter comprising a meter unit (2) and a sensor unit (3). The meter unit comprises a user interface (9), a sensor interface (11) for connection to the sensor unit (3), a metering interface (30) for connection to the charging station controller, and a microprocessor (10) configured to receive and process signals received from the sensor unit (3), to exchange data with the charging station controller and to receive commands from the user interface and output information to the user interface. The sensor unit is separate and connected at a point distal from the meter unit via an interconnection cable (25) for the transmission of measurement signals, the sensor unit being coupled to one of the pair of DC power supply lines (27a, 27b) configured for measuring the current flowing through said power line, the sensor unit further comprising a voltage sensor (6) for coupling to each of the pair of power supply lines for measuring a voltage difference therebetween.