Systems and methods for rapid disturbance detection and response

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, wherein the noisy measurement signal measures a supply line voltage of the HVAC system;

resetting the signal filter in response to the detected deviation exceeding a noise threshold, wherein resetting the signal filter comprises increasing a covariance parameter used by the signal filter to calculate a weight assigned to a current value of the noisy measurement signal, which causes the signal filter to assign a relatively lesser weight to a previous estimate of the supply line voltage and a relatively greater weight to the current value of the noisy measurement signal, thereby increasing a responsiveness of the signal filter to changes in the noisy measurement signal;

filtering the noisy measurement signal using the reset signal filter to determine a new estimate of the supply line voltage;

determining whether a disturbance has occurred by comparing the new estimate of the supply line voltage to both a brownout voltage threshold and a blackout voltage threshold less than the brownout voltage threshold, wherein both the brownout voltage threshold and the blackout voltage threshold are different from the noise threshold;

deactivating one or more active power relays in response to a determination that the new estimate of the supply line voltage is less than the blackout voltage threshold; and

preventing one or more inactive power relays from activating in response to a determination that the new estimate of the supply line voltage is between the blackout voltage threshold and the brownout voltage threshold.

2. The method of claim 1 , further comprising:

performing a control action in response to the new estimate of the supply line voltage crossing a disturbance threshold, wherein the control action includes at least one of: modifying a setpoint for a device of the HVAC system and controlling an activation status of a device of the HVAC system.

3. The method of claim 2 , wherein the disturbance threshold is at least one of the brownout voltage threshold and the blackout voltage threshold.

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 supply line voltage and for an error covariance;

computing a Kalman gain using the error covariance; and

updating the initial estimate of the supply line voltage using the Kalman gain and a measured value received from a measurement device.

5. 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.

6. 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.

7. The method of claim 1 , further comprising:

comparing the new estimate of the supply line voltage to a disturbance threshold; and

concluding that a disturbance has occurred if the new estimate of the supply line voltage is less than the disturbance threshold.

8. The method of claim 7 , wherein the disturbance threshold is a two-tiered threshold including the brownout voltage threshold and the blackout voltage threshold.

9. The method of claim 7 , wherein the supply line 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.

10. The method of claim 1 , wherein resetting the signal filter comprises increasing a process noise covariance parameter used by the signal filter to calculate the weight assigned to the current value of the noisy measurement signal.

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 of a supply line voltage 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, wherein resetting the signal filter comprises increasing a covariance parameter used by the signal filter to calculate a weight assigned to a current value of the noisy measurement signal, which causes the signal filter to assign a relatively lesser weight to a previous estimate of the supply line voltage and a relatively greater weight to the current value of the noisy measurement signal, thereby increasing a responsiveness of the signal filter to changes in the noisy measurement signal;

filter the noisy measurement signal using the reset signal filter to determine a new estimate of the supply line voltage;

determine whether a disturbance has occurred by comparing the new estimate of the supply line voltage to both a brownout voltage threshold and a blackout voltage threshold less than the brownout voltage threshold, wherein both the brownout voltage threshold and the blackout voltage threshold are different from the noise threshold;

deactivate one or more active power relays in response to a determination that the new estimate of the supply line voltage is less than the blackout voltage threshold; and

prevent one or more inactive power relays from activating in response to a determination that the new estimate of the supply line voltage is between the blackout voltage threshold and the brownout voltage 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 new estimate of the supply line voltage crossing a disturbance threshold, wherein the control actions include at least one of: modifying a setpoint for a device of the HVAC system and controlling an activation status of a device of the HVAC system.

13. The system of claim 12 , wherein the disturbance threshold is at least one of the brownout voltage threshold and the blackout voltage threshold.

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 supply line voltage and for an error covariance;

compute a Kalman gain using the error covariance; and

update the initial estimate of the supply line voltage using the Kalman gain and a value measured by the sensor.

15. 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.

16. 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.

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

compare the new estimate of the supply line voltage to a disturbance threshold; and

determine that a disturbance has occurred if the new estimate of the supply line voltage is less than the disturbance threshold.

18. The system of claim 11 , wherein resetting the signal filter comprises increasing a process noise covariance parameter used by the signal filter to calculate the weight assigned to the current value of the noisy measurement signal.