Thyristor Starter Phase Control for DC Voltage Regulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional thyristor starters face inefficiencies and size constraints due to increasing DC voltage at the inverter input terminal as synchronous machine rotation speed increases, requiring large converters and inefficient operation when DC voltage peaks.
Innovation Solution
A thyristor starter with a speed operation portion, control angle operation portion, and control unit that varies the phase control angle of the inverter in multiple steps relative to the synchronous machine's rotation speed, maintaining a constant DC voltage at the inverter input terminal by adjusting the rate of increase in phase control angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant phase control angle is used in the inverter, then the control is simple, but the DC voltage at the inverter input terminal increases with rotation speed, requiring a larger converter
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant phase control angle to a dynamic phase control angle that varies with rotation speed. The control angle operation portion adjusts the phase control angle in multiple steps according to the detected rotation speed, allowing the system to adapt to changing operating conditions and maintain optimal DC voltage levels across different speed ranges.
Solution Approach 2:
The patent changes the parameter of phase control angle from a constant value to a variable value that depends on rotation speed. By dividing the speed range into multiple steps and assigning different phase control angles to each step, the system optimizes the DC voltage at the inverter input terminal for each operating condition, preventing excessive voltage increases and reducing converter size requirements.
2Device complexity
If the phase control angle is increased at a constant rate with rotation speed, then the control is simple, but the DC voltage reaches a peak value at certain rotation speed, requiring a large converter capacity and lowering efficiency
Solution Approach 1:
The patent segments the continuous variation of phase control angle into discrete multiple steps corresponding to different rotation speed ranges. Instead of a constant rate of increase, the system divides the speed range into several steps, each with its own phase control angle setting. This segmentation allows precise control of DC voltage at different operating points, avoiding peak voltage conditions and optimizing converter efficiency throughout the speed range.
3Reliability
If a large converter is designed to handle peak DC voltage, then the converter can supply power at all speeds, but the converter operates inefficiently during periods when DC voltage does not reach peak values
Solution Approach 1:
The patent optimizes the operating parameters of the converter by dynamically adjusting the phase control angle based on rotation speed. This ensures that the DC voltage at the inverter input terminal remains within an optimal range for each speed condition, allowing the converter to operate efficiently across all speeds without requiring excessive capacity to handle rare peak conditions. The parameter change approach maintains reliable power supply while minimizing energy losses.
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
This approach reduces the variation in DC voltage at the inverter input, leading to a smaller and more efficient converter design, optimizing energy use and reducing converter size.
Implementation Method 1
a converter converting three-phase AC power to DC power
Implementation Method 2
a DC reactor smoothing DC power
Implementation Method 3
an inverter converting DC power provided from the converter through the DC reactor to three-phase AC power at a desired frequency
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(c)
AI summary
This thyristor starter includes a control angle operation portion (9) including a function or a table showing relation between a rotation speed (N) of a synchronous machine (21) and a phase control angle (γ) of an inverter (4) and finding a phase control angle (γ) having a value in accordance with the rotation speed (N) of the synchronous machine (21) found by a speed operation portion (8). The phase control angle (γ) varies from a minimum value (γa) to a maximum value (γb) in accordance with the rotation speed (N) of the synchronous machine (21), and a rate of increase (Δγ/ΔN) in phase control angle (γ) relative to the rotation speed (N) of the synchronous machine (21) is varied in a plurality of steps in accordance with the rotation speed (N) of the synchronous machine (21).