Converter Controller Voltage Stability Power Transmission Network
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Solution Overview
Problem
The interaction between the capacitance of power transmission media and the impedance of phase reactance in power transmission networks can cause disturbances that adversely affect the ability of converters to stably control voltage at AC terminals and the point of common coupling, leading to instability in the network.
Innovation Solution
A converter controller is programmed to process voltage and current measurements at the point of common coupling to compute a state vector, derive a converter demand by combining this vector with control parameters including capacitance and impedance, and operate the converter to inhibit perturbations, using full state feedback control principles and linear quadratic regulation to stabilize converter voltage and minimize the need for extensive communication links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional converter control is used, then the converter can operate in the power transmission network, but the interaction between capacitance of power transmission media and impedance of phase reactance causes voltage perturbations and instability
Solution Approach 1:
The patent implements a state feedback control mechanism where the converter controller continuously monitors the state vector (voltage and current at the point of common coupling) and adjusts the converter demand accordingly. The control law uses full state feedback to compute the converter demand that actively counteracts voltage perturbations caused by the interaction between capacitance and impedance, thereby stabilizing the converter voltage at the AC terminal and point of common coupling.
Solution Approach 2:
The patent changes the control parameters to include the capacitance of the power transmission medium and the impedance of the phase reactance in the converter demand calculation. By incorporating these parameters into the state feedback control law, the system adapts to the specific electrical characteristics of the transmission network and compensates for the harmful interaction effects, achieving stable voltage control despite the presence of capacitance-impedance interactions.
2Reliability
If full state feedback control is implemented to stabilize voltage, then voltage control stability is improved over a wide range of frequencies, but the complexity of the converter controller increases
Solution Approach 1:
The patent enables the converter controller to self-regulate by using locally available measurements of voltage and current at the point of common coupling to compute the state vector and determine the converter demand. The full state feedback control law allows the controller to automatically adjust its output based on the actual system state, eliminating the need for external control signals or complex communication infrastructure, thereby achieving wide frequency range stability while keeping the controller design relatively straightforward.
3Loss of information
If extensive communication links are deployed to monitor network conditions, then information about the power transmission network is obtained, but the device complexity and cost increase
Solution Approach 1:
The converter controller obtains all necessary information about the power transmission network state through local measurements of voltage and current at the point of common coupling. By using these measurements to compute the state vector and applying the state feedback control law, the system eliminates the need for extensive communication links distributed throughout the network, achieving full state awareness with minimal communication infrastructure.
Data Source
AI summary
A power transmission network including a single-phase or multi-phase AC electrical system, a converter including an AC terminal, a point of common coupling, a phase reactance connecting the common coupling to each AC terminal, and a transmission medium to interconnect the common coupling and the electrical system. The network includes a controller to: process the voltage and current at the common coupling to compute a state vector; derive a converter demand by combining the state vector with control parameters, including the capacitance of the power transmission medium presented at the common coupling and the impedance of the phase reactance; and operate the converter according to demand controlling the voltage at each terminal and/or the common coupling to inhibit any perturbation in the converter voltage from a target converter voltage or range resulting from the interaction between the capacitance of the power transmission medium and the impedance of the phase reactance.