Multilevel Hysteresis Voltage Control for Cascaded Power Cell Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing voltage modulation techniques in power electronic circuits suffer from inefficiencies such as low frequency pulsations due to unbalanced DC-link voltages and variations in load parameters, requiring complex PI controllers and additional regulation loops, which are inadequate for rapid load changes.
Innovation Solution
A multi-level hysteresis voltage controller (MHVC) with a robust structure that dynamically adjusts output voltages of power cells using a hysteresis loop, eliminating the need for additional regulation loops and ensuring precise voltage regulation across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common modulation techniques (PWM, PSM) are used, then voltage modulation can be achieved, but low frequency pulsations occur due to unbalanced DC-link voltages and parameter variations
Solution Approach 1:
The patent implements a hysteresis-based feedback mechanism that continuously monitors the output voltage and adjusts the switching states of power cells accordingly. The hysteresis comparator compares the actual output voltage with a reference voltage and switches the power cell configuration when the voltage deviates beyond hysteresis thresholds, providing automatic correction of voltage fluctuations without requiring additional regulation loops.
Solution Approach 2:
The patent employs dynamic switching of power cell configurations based on real-time voltage conditions. The system dynamically adjusts which power cells are connected in series or parallel, and dynamically modifies the duty cycles of switching devices, allowing the system to adapt quickly to voltage imbalances and parameter variations, thereby eliminating low frequency pulsations.
2Measurement precision
If PI controller with feedforward loop is used, then modulation index can be estimated, but the system becomes complex and cannot respond fast enough to rapid load changes
Solution Approach 1:
The patent extracts the essential control function from complex PI controllers with feedforward loops and implements a simplified hysteresis-based control mechanism. By taking out only the necessary voltage regulation function and implementing it through hysteresis comparators and simple switching logic, the system achieves accurate modulation index estimation without the complexity of multiple regulation loops.
Solution Approach 2:
The hysteresis control system is self-regulating and does not require external feedforward loops or complex parameter tuning. The system automatically adjusts its switching behavior based on the hysteresis thresholds and actual voltage conditions, providing fast response to load changes without requiring complex controller structures.
3Speed
If hysteresis voltage control is applied to voltage modulators, then fast response is achieved, but the control technique becomes increasingly complicated with increased number of series connected power cells
Solution Approach 1:
The patent segments the control of multiple series-connected power cells into independent modular units. Each power cell is controlled by its own switching device and hysteresis logic, allowing the system to maintain fast response characteristics while scaling to any number of series-connected cells. The segmentation approach prevents control technique complexity from increasing proportionally with the number of power cells.
Solution Approach 2:
The patent implements a universal control architecture where the same hysteresis-based control logic can be applied to any number of series-connected power cells. The control technique is designed to be multi-functional, handling voltage regulation, power cell balancing, and modulation index estimation through a unified approach, thereby preventing complexity escalation as the system scales.
4Reliability
If PI controller is used for voltage modulation, then voltage regulation can be achieved, but the controller cannot operate efficiently when load characteristics change rapidly and over wide range
Solution Approach 1:
The patent implements dynamic hysteresis thresholds that can adapt to different operating conditions and load characteristics. The switching logic dynamically adjusts the hysteresis band width based on the rate of change of voltage error and operating point, allowing the controller to maintain efficient voltage regulation across rapidly changing and wide-range load characteristics.
Solution Approach 2:
The patent employs parameter changes in the hysteresis control mechanism to adapt to different load conditions. By dynamically modifying hysteresis threshold values, switching frequencies, and power cell configuration parameters, the system maintains efficient and accurate voltage regulation even when load characteristics change rapidly and over a wide range.
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 MHVC provides fast and accurate voltage control with minimal regulation error, even under wide load fluctuations, by dynamically balancing power sharing and voltage levels among series-connected cells.
Implementation Method 1
a hysteresis block having a high boundary (HB) threshold and a low boundary (LB) threshold... when the voltage difference signal is higher than the high boundary (HB) threshold, the state of the hysteresis block is set to '1'... when the voltage difference signal is lower than the low boundary (LB) threshold, the state of the hysteresis block is set to '0'
Data Source
AI summary
Systems and methods that facilitate multilevel hysteresis voltage control methods for cascaded multilevel voltage modulators having a plurality of power cells connected in series and has any positive integer number of output voltage levels to control any unipolar voltage on the load of the voltage modulator, and transfer electrical power from an electrical grid via AC/DC converters or directly from energy storage elements of the power cells to that load. A method of operational rotation of the power cells of a multilevel voltage modulator, which ensures an equal power sharing among the power cells and voltage balancing of the energy storage elements of the power cells of the modulator.