Modular Inverter Cascade for Low-Loss AC Voltage Balancing
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Solution Overview
Problem
Existing systems for generating alternating voltage from multiple direct voltage sources face challenges in achieving high-quality, precise sinusoidal output due to interference and switching losses, particularly in battery management systems for electric vehicles and household power networks, where battery cells of varying capacities and conditions require balanced charging and discharging.
Innovation Solution
A modular inverter circuit arrangement featuring a cascade of inverter units connected to their own DC voltage sources, with a control device and data transmission system for precise configuration and synchronization, allowing for flexible combination of DC voltage sources and reducing clock frequencies to minimize switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the switching frequency of the inverter is increased to reduce voltage harmonics, then the quality of alternating voltage is improved, but the switching losses of the inverter increase proportionally
Solution Approach 1:
The patent divides a single high-frequency inverter into multiple lower-frequency inverters connected in series. Each inverter operates at a reduced switching frequency, collectively achieving the required high output voltage while maintaining lower individual switching losses. This segmentation allows the system to achieve high voltage quality without the exponential switching losses of a single high-frequency inverter.
2Reliability
If passive charge balancing is used to prevent overcharging, then battery cell safety is improved, but valuable electrical energy is lost
Solution Approach 1:
The patent implements active charge balancing using feedback control. The control device continuously monitors the charge states of individual battery cells and dynamically adjusts the operation of each inverter unit to redistribute energy among cells. This feedback mechanism prevents overcharging while recovering energy that would otherwise be wasted, converting it into useful electrical output instead of dissipating it as heat.
3Loss of energy
If active charge balancing is used to solve passive balancing problems, then energy efficiency is improved, but the circuit complexity with power electronic components and control systems increases
Solution Approach 1:
The patent makes each inverter unit in the cascade multi-functional: each unit not only contributes to the overall voltage generation but also participates in charge balancing of its associated battery cell. This universal design allows the same hardware infrastructure to perform both voltage generation and charge management functions, avoiding the need for separate dedicated balancing circuits and reducing overall system complexity.
4Power
If multiple battery cells are connected in series to achieve high voltage, then the voltage requirement is met, but manufacturing limitations cause different cell properties that complicate charge management
Solution Approach 1:
The patent segments the battery pack into multiple independent cell groups, each associated with its own inverter unit. This segmentation allows independent monitoring and control of each cell's charge state, simplifying the management of manufacturing variations. Each inverter unit handles its associated cell independently, transforming the complexity of managing diverse cell properties into a modular control architecture.
Solution Approach 2:
The patent applies local quality control by allowing each inverter unit to operate with parameters optimized for its specific battery cell characteristics. The control device configures each inverter unit individually based on the charge state and properties of its associated cell, enabling tailored charge management that accounts for local variations in cell performance while maintaining overall system coordination.
Data Source
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AI summary
The invention relates to a circuit arrangement (5) for generating an alternating voltage (uAC). The circuit arrangement comprises at least one modular inverter (7) configured as a cascade of several inverter units (8), a control unit (11) for configuring the inverter units (8), and a data transmission system (12) for signal transmission between the control unit (11) and the inverter units (8). Each of the inverter units (8) can be connected to its own DC voltage source (6), has a control input (sIN) and a data output (sOUT), and is configured to make the associated DC voltage source (6) available or unavailable for generating the alternating voltage (uAC) on the output side, depending on control signals received by the control unit (11) via the control input (sIN).The data transmission system (12) is provided to have a control line (S) and at least one data line (D) connected to the control unit (11), wherein the control line (S) is also connected to the control inputs (sIN) of the inverter units (8) and the at least one data line (D) is connected to the data outputs (sOUT) of the inverter units (8). The inverter units (8) are configured to transmit status information concerning the respective associated DC voltage source (6) to the control unit (11) via the at least one data line (D), wherein the control unit (11) is configured to transmit the control signals for configuring the inverter units (8) depending on the received status information.