Generator Inverter Control With Dynamic DC-Link Voltage Stabilization
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Solution Overview
Problem
Conventional inverter systems face limitations in using high proportional gain for DC-link voltage control, particularly at high load conditions, especially when the inductance of the inverter is large or the capacitance of the DC-link capacitor is small, leading to instability and suboptimal performance.
Innovation Solution
A method and controller that incorporate a dynamic stabilizing term into stator parameter references, such as stator current or flux references, to allow for higher proportional gain and faster DC-link voltage control by minimizing the energy change in stator currents or fluxes, thereby stabilizing the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high proportional gain is provided to the DC voltage controller to achieve fast response, then the DC-link voltage control speed is improved, but the system becomes unstable at high load conditions particularly when inductance is large or capacitance is small
Solution Approach 1:
The patent applies dynamics by making the d-axis current reference dynamic rather than constant. The d-axis current reference is adjusted based on operating conditions (load, inductance, capacitance values) to maintain stability while enabling fast response. This dynamic adjustment allows the system to adapt the stabilizing effect to different operating points, resolving the contradiction between fast response and stability.
Solution Approach 2:
The patent changes the parameter of d-axis current reference from a fixed value to a variable that depends on system parameters (inductance L, capacitance C, load power). By modifying this parameter dynamically, the system can maintain stability across different operating conditions while utilizing high proportional gain for fast DC-link voltage control response.
2Device complexity
If the inductance of the inverter is large or the capacitance of the DC-link capacitor is small, then the system structure is simplified or cost is reduced, but the maximum usable proportional gain is limited leading to slower control response
Solution Approach 1:
The patent changes the d-axis current reference parameter to compensate for the limited proportional gain caused by large inductance or small capacitance. This parameter modification allows the system to achieve faster control response without requiring changes to the physical inductance or capacitance values, thus maintaining device simplicity while improving performance.
Solution Approach 2:
The patent applies local quality by adjusting the d-axis current reference specifically in the d-axis direction (in the dq reference frame) to provide stabilizing effect where needed. This targeted adjustment in a specific parameter space allows the system to overcome the limitations imposed by large inductance or small capacitance without affecting other aspects of the system design.
3Power
If the maximum output voltage of the inverter is reached, then the inverter operates at full capacity, but the d-axis current reference needs to be adjusted to maintain stability
Solution Approach 1:
The patent applies dynamics by making the d-axis current reference adaptive to the operating point. When the inverter operates at full capacity (maximum output voltage reached), the d-axis current reference is automatically adjusted to provide the necessary stabilizing effect. This dynamic adaptation ensures stability is maintained across the entire operating range from low to full power.
Solution Approach 2:
The patent implements feedback by using information about the current operating state (whether maximum output voltage is reached) to adjust the d-axis current reference. This feedback mechanism ensures that stability is maintained by adapting the current reference based on the actual operating conditions, particularly when the inverter is operating at its power limits.
Data Source
AI summary
A method for operating an inverter configured to drive a generator is provided. The inverter comprises a direct current link (DC-link) having a DC-link capacitor, and the inverter is configured to convert a three-phase alternating current (AC) voltage generated by the generator into a DC-link voltage to be applied to the DC-link capacitor. The method includes receiving a DC-link voltage reference to be applied to the DC-link, receiving an actual DC-link voltage currently present over the DC-link, determining a stator parameter reference based on the received DC-link voltage reference and the received actual DC-link voltage, modifying the determined stator parameter reference by adding a dynamic stabilizing term to the stator parameter reference, generating a switching signal for the inverter based on the modified stator parameter reference, and operating the inverter by supplying the switching signal to the inverter.