Electric Drive Protective Device Voltage Spike Dissipation
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Solution Overview
Problem
Electric drive systems face high electrical currents and voltages during transitions to safe states like active short circuit or freewheeling, which can damage components if not properly dissipated, especially when the battery is disconnected.
Innovation Solution
A protective device that monitors the voltage across the intermediate circuit capacitor and alternates between motor and generator operating modes using space vector vectors to dissipate energy, preventing dangerous voltage and current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric drive system transitions to a safe state (active short circuit or freewheeling), then the system achieves protection against error states, but high electrical currents and voltages occur that can damage components
Solution Approach 1:
The control device detects intermediate circuit voltage in advance and activates the alternating operating modes before dangerous voltage levels cause damage. By monitoring voltage continuously and switching modes proactively, the system prevents harmful voltage buildup rather than reacting after damage occurs.
Solution Approach 2:
The control device alternates between motor operating mode and generator operating mode in periodic cycles. This periodic switching creates controlled energy dissipation cycles that prevent dangerous voltage accumulation in the intermediate circuit capacitor while maintaining system safety.
2Reliability
If the battery is disconnected from the drive system, then system safety is improved by isolating the energy source, but electrical energy cannot be dissipated leading to dangerous voltage buildup
Solution Approach 1:
The control device acts as an intermediary between the disconnected battery and the intermediate circuit capacitor. By switching between motor and generator modes, it creates an alternative energy dissipation path through the electric machine, allowing energy to be released without requiring battery connection.
Solution Approach 2:
The electric drive system dissipates its own stored energy using its own components (electric machine and intermediate circuit capacitor) without external assistance. The alternating operating modes enable the system to self-regulate and dissipate energy internally even when the battery is disconnected.
3Loss of energy
If the control device alternates between motor and generator operating modes, then electrical energy is dissipated effectively, but the device complexity increases
Solution Approach 1:
The control device utilizes the electric machine's existing dual capability to operate in both motor and generator modes. By leveraging this multi-functionality, the system achieves effective energy dissipation without adding separate dedicated dissipation hardware, thus limiting complexity increase.
Solution Approach 2:
The control device manages complexity by changing operational parameters (operating modes) rather than adding physical components. By switching between motor and generator modes through parameter control, the system achieves energy dissipation using existing infrastructure.
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
Effectively dissipates electrical energy without causing high voltages or currents, ensuring component safety by rapidly switching between operating modes based on monitored voltage levels.
Implementation Method 1
The voltage sensor is designed to detect an electrical voltage across the intermediate circuit capacitor
Implementation Method 2
The control device is designed to alternately provide a first control signal for the power converter based on a first space vector vector and to provide a second control signal for the power converter based on a second space vector vector
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to the protection of an electric drive system. If a voltage spike occurs on the input of a current converter of the electric drive system via the intermediate circuit, then in order to dissipate said voltage spike in the electric drive system, a change is made to and fro between a motor operating mode and a generator operating mode in order to dissipate the electrical energy from the intermediate circuit capacitor. For the motor operating mode and the generator operating mode, in each case suitable space phasor vectors can be predefined. This permits particularly simple and rapid activation in order to dissipate the electrical energy in the electric drive system.