Power Converter Modulation Switching for Short-Circuit Overload
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power converters, when used as grid power generation units, face challenges in handling short-circuit situations due to their design limitations, leading to potential damage from high overload currents, as they are not typically designed to handle currents three times their rated value, necessitating oversizing to manage rare and brief operating cases.
Innovation Solution
A method for operating a power converter that switches between normal pulse width modulation and fundamental frequency modulation during exceptional situations, reducing switching frequency to manage high currents while ensuring functionality and protection against overcurrent and thermal overload, using measurements and logical combinations to control semiconductor switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter is oversized to handle short-circuit currents, then the overload capacity is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies dynamics by switching between two modulation modes (PWM and fundamental frequency modulation) depending on the operating condition. During normal operation, PWM provides efficient control, while during exceptional situations like short circuits, the system transitions to fundamental frequency modulation with reduced switching frequency, enabling the converter to handle overload currents without requiring permanent oversizing.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically. During exceptional situations, the switching frequency is reduced from typical PWM frequencies (e.g., 2.5 kHz) to fundamental frequency (e.g., 550 Hz), which allows the semiconductor switches and electrical connections to withstand high overload currents without damage, effectively increasing overload capacity without physical oversizing.
2Loss of energy
If the switching frequency is reduced to handle overload, then the power loss is reduced, but the control precision and feedback capability deteriorate
Solution Approach 1:
The system dynamically adapts control precision to operating conditions. During exceptional situations with reduced switching frequency, the control precision requirements are relaxed as the primary goal becomes overload management rather than precise voltage control. The logical combination with measurement results ensures that essential protection functions (overcurrent and thermal overload protection) are maintained even at lower switching frequencies.
Solution Approach 2:
During exceptional situations, the system applies partial control action by using only fundamental frequency modulation without full PWM functionality. This partial action is sufficient for the specific purpose of handling overload currents and providing protection, while avoiding the excessive switching activity that would cause high power losses.
3Power
If the semiconductor switches are activated at high frequency during exceptional situations, then the voltage control is maintained, but the thermal overload and damage risk increase
Solution Approach 1:
The patent changes the switching frequency parameter from high (PWM frequency of 2.5 kHz or higher) to low (fundamental frequency of approximately 550 Hz) during exceptional situations. This parameter change reduces the switching losses and thermal stress on semiconductor switches, enabling them to handle the high currents without thermal overload or damage while maintaining sufficient voltage control capability through logical combination with measurement results.
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
Method for operating a power converter, computer program for implementing such a method and data carrier as well as computer system, in particular power converter, on which such a computer program is stored orA method for operating a power converter (10) with a bridge circuit equipped with controllable semiconductor switches (T1, T2, T3, T4, T5, T6) is described, wherein the semiconductor switches (T1-T6) are controlled during normal operation of the power converter (10) according to a normal operation modulation referred to as the first modulation mode, and a power converter operating according to the method is described, in which, during an exceptional or fault situation, in particular a mains voltage dip or short circuit, the control of the semiconductor switches (T1-T6) is carried out on the basis of a second modulation mode, wherein a measurement is carried out in mains-side strings (24, 26, 28) to which the power converter (10) is connected and an actual control of the semiconductor switches (T1-T6) is carried out with regard to switching times of the second modulation mode and a logical connection with the results of the measurement.