DC-bus Controller Adaptive Estimator Ripple Isolation

Solution Overview

Problem

Conventional DC-bus voltage control schemes for grid-connected DC/AC converters suffer from sluggish transient responses due to low frequency ripple in the DC-bus capacitor voltage, leading to over-designing of converters and increased costs, as they require low bandwidth PI controllers to prevent ripple propagation.

Innovation Solution

An adaptive DC-value estimator/observer is used to estimate the DC-bus voltage, allowing for a high bandwidth voltage loop controller by isolating double frequency ripple, thereby improving transient response and system robustness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a low bandwidth PI controller is used to regulate DC-bus voltage, then the low frequency ripple is prevented from propagating to the control loop, but the transient response becomes sluggish and poor

Engineering Contradiction:

Improveripple preventionVSAvoidtransient response

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The control system is segmented into two independent parts: a high bandwidth current controller that handles transient response, and a low bandwidth voltage controller that handles ripple suppression. The current controller operates at high bandwidth to provide fast transient response, while the voltage controller operates at low bandwidth to suppress ripple, eliminating the need to choose between the two conflicting requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A decoupling mechanism is introduced as an intermediary between the voltage and current control loops. This decoupling compensates for the interaction between the two loops, allowing the high bandwidth current controller to operate without being constrained by the low bandwidth voltage controller, thus achieving both ripple suppression and fast transient response.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If a high bandwidth voltage loop controller is used, then the transient response is improved, but the low frequency ripple propagates to the control loop

Engineering Contradiction:

Improvetransient responseVSAvoidripple propagation

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The control system is segmented into two independent parts: a high bandwidth current controller that handles transient response, and a low bandwidth voltage controller that handles ripple suppression. The current controller operates at high bandwidth to provide fast transient response, while the voltage controller operates at low bandwidth to suppress ripple, eliminating the need to choose between the two conflicting requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A decoupling mechanism is introduced as an intermediary between the voltage and current control loops. This decoupling compensates for the interaction between the two loops, allowing the high bandwidth current controller to operate without being constrained by the low bandwidth voltage controller, thus achieving both ripple suppression and fast transient response.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the DC-bus capacitor is over-designed to handle transient overshoots/undershoots, then system reliability is improved, but system cost increases

Engineering Contradiction:

Improvetransient handling capabilityVSAvoidcapacitor size

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The control system transitions from a static, conservative design to a dynamic control approach. By implementing a high bandwidth current controller with decoupling, the system can actively and rapidly respond to transient disturbances, eliminating the need for oversized passive components like capacitors. The dynamic control compensates for what would otherwise require excessive energy storage capacity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control parameters are optimized to achieve fast transient response without requiring oversized hardware. The high bandwidth current controller adjusts the control gains and response characteristics dynamically, allowing the system to handle transient overshoots and undershoots through active control rather than passive over-design of the DC-bus capacitor.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9537424B2DC-bus controller for grid-connected DC/AC converters

Publication Date: 2017.01.03 SPARQ SYST INC

AI summary

Systems, methods, and devices for controlling a DC-bus voltage for a power conditioning system. A control system regulates the DC value of the DC-bus voltage. The control system uses an adaptive DC-value estimator/observer to estimate this DC-value. Instead of having to determine the DC-value of a signal with a low frequency ripple without compromising the signal's dynamic response, a suitably precise estimate for that DC-value is used.