Parallel DPWM Converter Control for Switching Discontinuity Alignment
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Solution Overview
Problem
The parallel operation of power converters using discontinuous pulse width modulation (DPWM) schemes generates significant differential and common mode noise, and existing solutions like coupling converters to different transformer windings or adding large filters increase size, weight, and cost.
Innovation Solution
Generate reference signals for each power converter such that switching discontinuities in their PWM signals are aligned, allowing operation at different operating points without the need for additional transformers or large filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If parallel power converters operate with discontinuous PWM schemes at different operating points, then power conversion capability is increased, but differential and common mode noise increases significantly
Solution Approach 1:
The control system pre-aligns the switching discontinuities of PWM signals from multiple parallel converters by adjusting their phase relationships. This preliminary synchronization ensures that discontinuities occur simultaneously, preventing the generation of differential and common mode noise while maintaining the power conversion capability of parallel operation at different operating points
Solution Approach 2:
The invention changes the temporal parameters of PWM signals by adjusting the phase and timing of switching discontinuities. By modifying when the discontinuities occur in each converter's PWM cycle, the system achieves alignment that eliminates noise generation while preserving the ability to operate at different power levels
2Object-generated harmful factors
If common mode filters are added to reduce noise, then noise is reduced, but system size, weight, and cost increase
Solution Approach 1:
The invention extracts and eliminates the root cause of noise generation through control signal alignment, removing the need for physical filtering components. By addressing the noise problem at its source through PWM synchronization rather than adding filtering hardware, the system avoids increasing size, weight, and cost
Solution Approach 2:
The invention replaces the mechanical/physical approach of adding filters with a control-theory approach of aligning switching discontinuities. This substitution eliminates the need for additional inductors, capacitors, and filters, thereby avoiding increased system size, weight, and cost while still achieving noise reduction
3Object-generated harmful factors
If power converters are coupled to different transformer windings, then noise is reduced, but implementation flexibility is limited
Solution Approach 1:
The control system acts as an intermediary that coordinates the PWM signals from parallel converters before they reach the common AC bus. By introducing this control layer that aligns switching discontinuities, the system achieves noise reduction without requiring physical separation through different transformer windings, thus maintaining implementation flexibility
4Adaptability or versatility
If switching discontinuities in PWM signals are misaligned, then different operating points can be maintained, but noise and distortions increase
Solution Approach 1:
The control system performs preliminary alignment of switching discontinuities by adjusting the phase of PWM signals before they are generated. This advance coordination allows each converter to operate at its required operating point while ensuring their switching events are synchronized, preventing noise and distortions
Data Source
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Figure 5~6
AI summary
A method of controlling the operation of a power converter system is provided. The power converter system (10) may comprise at least a first power converter (11) and a second power converter (21), each power converter (11, 21) having an AC side with an AC interface (30), the first and second power converters (11, 21) being electrically connected together at their AC interfaces (30). Each power converter (11, 21) may be operated with a pulse width modulation (PWM) scheme that generates a PWM signal (63, 73) based on a reference signal (61, 71). A first reference signal (61) and a second reference signal (71) are generated such that a switching discontinuity (75) in a second PWM signal (73) derived from the second reference signal (71) is aligned with a corresponding switching discontinuity (65) in a first PWM signal (63) derived from the first reference signal (61).