SYSTEMS AND METHODS FOR RAPID DISTURBANCE DETECTION AND RESPONSE

• US 20140214214A1
• Filed: 01/31/2013
• Published: 07/31/2014
• Est. Priority Date: 01/31/2013
• Status: Active Grant

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Johnson Controls Technology Company (Johnson Controls International plc)
• Inventors: Asmus, Matthew J., Turney, Robert D., Seifi, Justin J.
• Granted Patent: US 9,568,204 B2
• Time in Patent Office: Days
• US Class Current: 700/276
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/49 ensuring correct operation, e.g. by trial operation or configuration checks
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2130/40 Noise
• CPC Class Codes: G01D 3/021 using purely analogue techniques
• CPC Class Codes: G01D 3/08 with provision for safeguarding the apparatus, e.g. against abnormal operation, against breakdown

Abstract

A method for detecting and responding to disturbances in a HVAC system using a noisy measurement signal and a signal filter is provided. The method includes detecting a deviation in the noisy measurement signal, resetting the filter in response to a detected deviation exceeding a noise threshold, filtering the noisy measurement signal using the signal filter to determine an estimated state value, and determining that a disturbance has occurred in response to the estimated state value crossing a disturbance threshold. In some embodiments, the method further includes performing one or more control actions in response to the detection of a disturbance.

Claims

1. A method for detecting and responding to disturbances in a HVAC system using a noisy measurement signal and a signal filter, the method comprising:

detecting a deviation in the noisy measurement signal;

resetting the signal filter in response to the detected deviation exceeding a noise threshold;

filtering the noisy measurement signal using the signal filter to determine an estimated state value;

determining whether a disturbance has occurred in response to the estimated state value crossing a disturbance threshold.

2. The method of claim 1, further comprising:

performing a control action in response to the determination of the disturbance, wherein the control actions include at least one of;

modifying a setpoint for a device of the HVAC system and controlling an activation status a device of the HVAC system.

3. The method of claim 2, wherein the disturbance threshold is at least one of a brownout voltage threshold or a blackout voltage threshold and wherein controlling an activation status for a device of the HVAC system includes deactivating a power relay or preventing a power relay from activating.

4. The method of claim 1, wherein the filter is a Kalman filter and wherein filtering the noisy measurement signal includes:

receiving an initial estimate for the estimated state value and for an error covariance;

computing a Kalman gain using the error covariance; and

updating the estimated state value using the Kalman gain and a measured value received from a measurement device.

5. The method of claim 1, wherein resetting the signal filter includes adjusting a covariance parameter used by the signal filter, wherein adjusting the covariance parameter affects a responsiveness of the signal filter to the deviation in the measurement signal.

6. The method of claim 1, wherein the deviation in the noisy measurement signal is at least one of:

a difference between two measured values in the noisy measurement signal, a difference between a measured value in the noisy measurement signal and a steady state value, and a standard deviation of two or more measured values in the noisy measurement signal.

7. The method of claim 1, wherein the noisy measurement signal is received from at least one of:

a chiller, a boiler, an air handling unit, a flow controller, a field controller, a supervisory controller, an actuator, a signal relay, a temperature sensor, a pressure sensor, a voltage sensor, and a current sensor.

8. The method of claim 1, wherein the noisy measurement signal is a voltage measurement and the estimated state value is an estimated voltage, wherein determining that a disturbance has occurred includes:

comparing the estimated voltage to the disturbance threshold; and

concluding that a disturbance has occurred if the estimated voltage is less than the disturbance threshold.

9. The method of claim 8, wherein the disturbance threshold is a two-tiered threshold including a brownout voltage threshold and a blackout voltage threshold, wherein the blackout voltage threshold is less than the brownout voltage threshold.

10. The method of claim 8, wherein the voltage is an AC voltage and an oscillatory period of the AC voltage defines a line cycle, wherein it is determined that a disturbance has occurred within three line cycles of the disturbance occurring.

11. A system for detecting and responding to disturbances using a noisy measurement signal and a signal filter, the system comprising:

a sensor configured to measure one or more values in an HVAC system, wherein the sensor produces a noisy measurement signal including the one or more measured values; and

a processing circuit configured to;

detect a deviation in the one or more measured values;

reset the signal filter in response to the detected deviation exceeding a noise threshold;

filter the noisy measurement signal using the signal filter to determine an estimated state value; and

determine whether a disturbance has occurred in response to the estimated state value crossing a disturbance threshold.

12. The system of claim 11, wherein the processing circuit is further configured to:

perform one or more control actions in response to the disturbance, wherein the control actions include at least one of;

modifying a setpoint for a device of the HVAC system and controlling an activation status a device of the HVAC system.

13. The method of claim 12, wherein the disturbance threshold is a brownout voltage threshold or a blackout voltage threshold and wherein controlling an activation status for a device of the HVAC system includes deactivating a power relay or preventing a power relay from activating.

14. The system of claim 11, wherein the filter is a Kalman filter and wherein the processing circuit is configured to:

receive an initial estimate for the estimated state value and for an error covariance;

compute a Kalman gain using the error covariance; and

update the estimated state value using the Kalman gain and a value measured by the sensor.

15. The system of claim 11, wherein resetting the signal filter includes adjusting a covariance parameter used by the signal filter, wherein adjusting the covariance parameter affects a responsiveness of the signal filter to the deviation in the measured values.

16. The system of claim 11, wherein the deviation is at least one of:

a difference between two of the measured values, a difference between one of the measured values and a steady state value, a variance of two or more of the measured values, and a standard deviation of two or more of the measured values.

17. The system of claim 11, wherein the sensor is configured to measure at least one of:

a temperature, a pressure, a voltage, a flow rate, a power usage, and an electric current.

18. The system of claim 11, wherein the measured values are voltage measurements and the estimated state value is an estimated steady state voltage, wherein the processing circuit is configured to:

compare the estimated steady state voltage to the disturbance threshold; and

determine that a disturbance has occurred if the estimated steady state voltage is less than the disturbance threshold.

19. A method for adaptively updating a filter to detect disturbances in a noisy measurement signal, the method comprising:

outside of the filter, monitoring for a deviation exceeding a noise threshold in a collection of recent measurements in the noisy measurement signal;

adjusting, in response to the deviation, a parameter used by the filter to provide a weight to a previous estimate used by the filter;

filtering the noisy measurement signal using the adjusted parameter and the previous estimate to determine an updated estimate;

outputting the updated estimate and repeating the monitoring, adjusting, and filtering steps.

20. The method of claim 19, wherein the filter is a Kalman filter and the adjusted parameter is an error covariance parameter used by the filter to assign a weight to the previous estimate, wherein the deviation is a standard deviation of the collection of recent measurements, and wherein adjusting the parameter involves increasing the error covariance parameter used by the Kalman filter in response to the deviation exceeding the noise threshold.