Frequency Converter Auxiliary Voltage Segmentation
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Solution Overview
Problem
Existing frequency converters face challenges in operating outside their normal input voltage range, leading to uneven stress on power semiconductor switches and limitations in motor type compatibility, especially during power supply disruptions, where they require limited performance and alternative power sources.
Innovation Solution
A frequency converter with two auxiliary voltage sources and corresponding control units, allowing operation across a wide voltage range, where the first unit operates at lower voltages for basic control and the second unit takes over at normal voltages, enabling three-phase voltage pulse patterns for inverter control, and allowing connection of a battery as a temporary power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a frequency converter is designed to operate only within its normal input voltage range, then the auxiliary voltage source can be dimensioned for efficient operation, but the device cannot operate during power supply disruptions or outside normal voltage ranges
Solution Approach 1:
The auxiliary voltage source is divided into two separate sources: a first auxiliary voltage source for normal operating conditions and a second auxiliary voltage source for low-voltage conditions. This segmentation allows each source to be optimized for its specific operating range, enabling the frequency converter to operate across a wider voltage spectrum without excessive complexity in a single source design.
Solution Approach 2:
The frequency converter system achieves multi-functionality by incorporating two auxiliary voltage sources that can operate independently or in coordination. The first auxiliary voltage source handles normal operating voltages while the second handles low-voltage conditions, making the device universally operable across diverse power supply conditions including disruptions.
2Adaptability or versatility
If only one auxiliary voltage source is used, then the device structure remains simple, but the frequency converter cannot operate at lower voltages when network power is disconnected
Solution Approach 1:
The auxiliary voltage functionality is segmented into two distinct sources with different operating characteristics. The first auxiliary voltage source operates during normal network power conditions, while the second auxiliary voltage source activates when network power is disconnected or at lower voltages, enabling operation during power disruptions without requiring a completely redundant system.
3Adaptability or versatility
If the frequency converter uses a single control unit, then the control structure is simplified, but it cannot provide optimized control for both normal and low-voltage operating conditions
Solution Approach 1:
The control system is segmented into a first control unit and a second control unit, each optimized for specific operating conditions. The first control unit manages normal operating conditions while the second control unit handles low-voltage conditions, providing adapted control strategies for each scenario without requiring a single complex control algorithm to handle all conditions.
Solution Approach 2:
Each control unit possesses local quality optimized for its specific operating range. The first control unit is configured for normal voltage conditions while the second control unit is configured for low-voltage conditions, allowing each to employ control parameters and strategies specifically suited to its operating context rather than using a generic control approach.
4Reliability
If power semiconductor switches control only one branch, then control is simplified, but uneven stress distribution can lead to component damage
Solution Approach 1:
The control of power semiconductor switches is segmented between two control units, each managing specific switches during their respective operating conditions. This segmentation ensures that when one auxiliary voltage source is active, its corresponding control unit manages the appropriate switches, distributing stress more evenly across the power semiconductor components by matching control activation with operational requirements.
Data Source
Figure 1~3
Figure 4
AI summary
Method and apparatus for controlling a frequency converter, which frequency converter comprises a rectifier (REC) connected to the input voltage, a three-phase inverter (INU) provided with controllable solid-state switches, an intermediate voltage circuit between these, and also a control system, which is supplied with two auxiliary voltage sources, and which frequency converter controls the operation of an electric motor (M) connected to it, and which frequency converter comprises two auxiliary voltage sources (PS1, PS2), operating in different voltage ranges and to be connected to the intermediate voltage circuit, to each of which auxiliary voltage sources an own control unit (CU1, CU2) is connected, both of which control units are able to form a three-phase control pulse pattern controlling the inverter (INU), which first auxiliary voltage source (PS1) is controlled to operate when the intermediate circuit voltage rises to a first level, and it supplies operating voltage at least to the first control unit (CU1) and to the gate drivers controlling the power semiconductors of the inverter, which second auxiliary voltage source (PS2) is controlled to operate when the intermediate circuit voltage rises to a second level, and it supplies operating voltage at least to the second control unit (CU2) and to the gate drivers controlling the power semiconductors of the inverter, and wherein when the second control unit energizes to operate, the using of the control signals formed by the first control unit for controlling the power semiconductors of the inverter is prevented.