Common Mode Voltage Control Filter for Power Converters
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Solution Overview
Problem
Existing power converter systems face challenges in effectively reducing common mode voltages generated during switching operations, which can exceed insulation ratings and shorten the lifespan of loads like motors, with existing solutions either increasing complexity, cost, or size, or failing to adequately reduce these voltages.
Innovation Solution
A three-phase power converter system incorporating a common mode voltage control filter with a resistive, capacitive, and inductive network, including an LC or notch filter, coupled to the inverter outputs and DC bus, which reduces common mode voltages by circulating current within the filter and avoiding ground coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional switches are used to compensate for common mode voltages, then common mode voltage reduction is achieved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the common mode voltage compensation function from the main power conversion circuit by introducing a separate auxiliary winding on the transformer. This auxiliary winding is specifically dedicated to generating negative common mode voltages to cancel out the harmful common mode voltages, while the main switching circuit remains unchanged and simple to control.
Solution Approach 2:
The auxiliary winding acts as an intermediary element between the transformer and the common mode voltage issue. By coupling this auxiliary winding to the transformer, the system can generate compensating negative common mode voltages without requiring additional switches or complex control circuitry in the main power conversion path.
2Object-affected harmful factors
If transformers are used to handle common mode voltage levels, then common mode voltage compensation is achieved, but cost and size increase
Solution Approach 1:
The invention makes the transformer multi-functional by adding an auxiliary winding that serves dual purposes: the transformer continues its main function of power conversion while simultaneously providing common mode voltage compensation through the auxiliary winding. This eliminates the need for separate common mode chokes or additional transformers.
Solution Approach 2:
The common mode voltage compensation function is merged with the existing transformer structure. The auxiliary winding is integrated into the transformer core, combining the power conversion and common mode compensation functions into a single component, thereby avoiding the need for separate sizeable components.
3Device complexity
If standard power converter structure is used, then simplicity and cost-effectiveness are maintained, but common mode voltage reduction capability is insufficient
Solution Approach 1:
The invention segments the voltage generation function into two parts: the main transformer windings handle the primary power conversion, while the auxiliary winding specifically handles common mode voltage compensation. This segmentation allows the standard power converter structure to be maintained while adding targeted common mode voltage reduction capability.
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 significantly reduces common mode voltages from 200V to 3V, maintaining system simplicity, cost-effectiveness, and size, while ensuring safe operation of loads by effectively managing voltage levels.
Implementation Method 1
A three-phase power converter system incorporating a common mode voltage control filter with a resistive, capacitive, and inductive network, including an LC or notch filter
Implementation Method 2
A three-phase power converter system incorporating a common mode voltage control filter with a resistive, capacitive, and inductive network
Data Source
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AI summary
A three-phase power converter includes a converter configured to convert a three phase AC power input to a DC power output, the DC power output being provided to high and low sides of a DC bus, and an inverter coupled to the DC bus and configured to convert the DC power to a three phase AC output. The inverter comprises three legs and each leg comprises a pair of solid state switches and a respective output therebetween. The power converter further includes a common mode voltage control filter comprising three filter inputs and two filter outputs, each filter input coupled to an output of a respective leg of the inverter and each filter output coupled to a respective side of the DC bus.