Battery Charging Circuit Using Three-Phase Inverter Rectification
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Solution Overview
Problem
Conventional battery charging methods for electric vehicles, such as quasi-constant voltage transformers and constant current-constant voltage-constant current methods, are inefficient and require complex configurations, leading to insufficient or overcharging, and are costly due to the need for numerous components and modified circuit wiring.
Innovation Solution
A battery charging circuit that uses a single-phase output transformer, a rectifier circuit connected in parallel with a three-phase inverter and battery, and a controller to perform on-off control of switching elements, allowing for constant current charging without modifying motor or inverter connections, using a Scott connection transformer to match current and voltage waveforms for efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current-constant voltage-constant current (CC-CV-CC) charging method is used, then charging performance is improved and does not depend on input voltage or battery state, but the number of components increases and cost increases
Solution Approach 1:
The patent makes the three-phase inverter serve dual functions: motor drive during vehicle operation and battery charging during charging mode. By controlling the inverter to operate as a rectifier during charging, the system eliminates the need for separate charging circuitry while maintaining reliable constant current charging performance.
Solution Approach 2:
The patent combines the motor drive inverter and charging circuit into a single integrated system. The same three-phase inverter and switching elements are used for both driving the motor and charging the battery, reducing component count while maintaining charging performance through coordinated control.
2Ease of manufacture
If connector is provided in motor coil line and rectifier is connected to neutral point of motor coils, then charging circuit can be formed using conventional motor control circuit, but components must be added and circuit wiring must be modified which complicates charger configuration
Solution Approach 1:
The patent enables the existing three-phase inverter to perform both motor control and battery charging functions without adding connectors or modifying the neutral point connection. The inverter's switching elements are controlled to rectify AC charging voltage and charge the battery, eliminating the need for separate charging circuitry.
Solution Approach 2:
The patent makes the motor inverter serve itself by using its own switching elements and circuitry for both motor drive and battery charging. The system utilizes its existing components to perform the charging function without requiring external charging circuitry or modifications to the motor coil connections.
3Device complexity
If quasi-constant voltage transformer charging method is used, then charging circuit is simple, but charging performance depends on input voltage and battery state causing insufficient charging or overcharging
Solution Approach 1:
The patent implements control based on detecting the battery voltage and comparing it with reference values. The controller adjusts the switching elements' on-off timing to maintain constant charging current, preventing both insufficient charging and overcharging while maintaining circuit simplicity.
Solution Approach 2:
The patent dynamically controls the switching elements to transition between different operating modes based on battery state. The system maintains constant current charging by adjusting switching timing according to battery voltage levels, ensuring reliable charging performance while keeping the circuit configuration simple.
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
Enables constant current charging with minimal additional components, improves power factor, reduces the number of components needed, and shortens charging time by using existing motor and inverter systems without disrupting their operation, and eliminates the need for a full-wave rectifier circuit.
Implementation Method 1
a transformer is connected in a Scott T configuration
Implementation Method 2
a rectifier circuit connected in parallel with a three-phase inverter and battery
Data Source
Figure 1
Figure 2A~3B
Figure 4~5D
AI summary
A charging circuit is provided that charges a battery for supplying power to a motor drive system that includes a three-phase motor and a three-phase inverter for controlling the three-phase motor. The three-phase inverter includes first to third sets of switching elements. Each set corresponds to one of the three phases. The charging circuit includes a single-phase output transformer, a rectifier circuit, a line, and a controller. The single-phase output transformer includes a secondary side output section having a first terminal and a second terminal. The rectifier circuit is connected in parallel with the three-phase inverter and the battery. The rectifier circuit is also connected to the first terminal of the secondary side output section. The line connects a connecting point between the first set of the switching elements in the three-phase inverter with the second terminal of the secondary side output section. The controller performs on-off control of the first to third sets of the switching elements. During charging of the battery, the controller maintains the first set of the switching elements in an OFF state, and performs the on-off control of at least one set of the second and third sets of the switching elements.