Active Rectifier VSCF Circuit for Constant-Frequency Generator Output
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Solution Overview
Problem
Existing VSCF systems with passive rectifiers deliver variable voltage to the DC bus, lack optimal sizing of power modules and capacitors over the operating range, and are non-reversible, limiting their efficiency and functionality in generating constant frequency polyphase currents from variable speed synchronous generators.
Innovation Solution
An active rectifier system with controllable switches and an electronic control unit that monitors and controls both the rectifier and inverter, allowing for regulated DC voltage, defluxing, and reversibility, along with an EMC filter with inductors and capacitors for each phase, enabling efficient management of the neutral and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a passive rectifier is used in the VSCF system, then the system control is simplified, but the voltage delivered to the DC bus becomes variable and cannot be optimally regulated
Solution Approach 1:
The patent transforms the static passive rectifier into a dynamic active rectifier with controllable switches (IGBTs or MOSFETs) that can be controlled in real-time. This allows the rectifier to adapt its operation dynamically, enabling regulated DC voltage output while maintaining system functionality. The active rectifier bridges the gap between control simplicity and voltage stability by introducing controllable elements that respond to control signals.
Solution Approach 2:
The invention changes the operational parameters of the rectifier by introducing controllable switches that can be activated or deactivated based on control signals. This parameter change enables the rectifier to regulate DC voltage by controlling the conduction angle and timing of the switches, thereby transforming the rectifier from a passive voltage-delivering component to an active voltage-regulating component.
2Device complexity
If a passive rectifier is used, then the system structure is simpler, but the sizing of power modules and capacitors cannot be optimal over the entire operating range
Solution Approach 1:
The active rectifier introduces dynamic control capability that allows the system to optimize power module and capacitor sizing across different operating ranges. By controlling the switches dynamically, the system can adapt to varying power demands and maintain optimal component utilization throughout the entire operating range, rather than being fixed at a single operating point.
Solution Approach 2:
The active rectifier with controllable switches provides multi-functionality, serving both as a rectifier and as a voltage regulator. This universal component can operate efficiently across different operating conditions, making the power modules and capacitors optimally sized for various power levels and operating scenarios, thereby improving overall system productivity.
3Device complexity
If a passive rectifier is used, then the system is simpler to implement, but the synchronous generator cannot be defluxed
Solution Approach 1:
The active rectifier enables dynamic control of current flow direction and magnitude, which is essential for defluxing the synchronous generator. By controlling the switches in reverse conduction mode, the active rectifier can extract residual magnetic flux from the generator, a capability that requires dynamic bidirectional control rather than the unidirectional flow of a passive rectifier.
Solution Approach 2:
The active rectifier enables reverse operation to achieve defluxing by controlling the controllable switches to conduct in the reverse direction. This inversion of the normal rectification process allows current to flow back to the generator, extracting residual flux. The passive rectifier's diode structure prevents this reverse conduction, while the active rectifier's controlled switches enable it.
4Device complexity
If a passive rectifier is used, then the system has fewer components, but current flow is unidirectional and energy recovery is not possible
Solution Approach 1:
The active rectifier introduces dynamic bidirectional control capability that enables energy recovery. By controlling the switches to conduct in both forward and reverse directions, the system can capture regenerative energy and feed it back to the DC bus or generator, transforming the unidirectional energy flow of a passive rectifier into a bidirectional energy management system.
Solution Approach 2:
The active rectifier enables the system to recover energy that would otherwise be discarded. By controlling the controllable switches to operate in reverse conduction mode, the system can capture regenerative energy during braking or deceleration and feed it back to the DC bus or generator, thereby recovering energy instead of losing it.
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 active rectifier system ensures a constant frequency polyphase current output, improves efficiency, allows for reversible operation, and enhances the system's ability to manage short circuits and neutral management, providing a stable and fault-tolerant power supply.
Implementation Method 1
a permanent magnet synchronous generator 2
Implementation Method 2
means for converting an alternating current into a direct current
Implementation Method 3
a direct current into an alternating current
Implementation Method 4
an electromagnetic compatibility filter 9a arranged at the output of the system 1a
Data Source
AI summary
A system configured to deliver as output a polyphase current of constant frequency from a synchronous generator driven at variable speed. The system includes, at the output of the generator, an AC-to-DC active rectifier including one arm per phase of the current, a DC bus and a DC-to-AC inverter for the output including one arm per phase of the current, the inverter or the DC bus including an arm connected to the neutral, each arm including a controllable switch, the system including an electronic control unit driving the rectifier and including means for tracking a voltage for the rectifier and/or the inverter and means for controlling the inverter, the system including an EMC filter including one arm for each phase of the current, each arm including an inductor, a capacitor connected in a bypass downstream of the inductor, the arm connected to the neutral being connected to each bypass.