Systems and methods for generating an inertial response to a change in the voltage of an electricial grid

Patent metadata

Field	Value
Publication number	US-9728969-B2
Application number	US-201113149054-A
Country	US
Kind code	B2
Filing date	May 31, 2011
Priority date	May 31, 2011
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

Systems, methods, and computer program products for providing an inertial response by a wind power system to power fluctuations in an electrical grid. The system includes a synthetic inertial response generator configured to generate a power offset in response to fluctuations in grid voltage. The power offset signal is generated by determining a quadrature component the grid voltage using an internal reference voltage having an angular frequency and phase angle that is synchronized to the electrical grid by a control loop. The quadrature component is used to determine a synchronous power level. A control loop error signal is produced by the difference between the synchronous power level and the wind turbine system power output. Changes in the grid frequency produce an error signal that is added to the power set point of wind turbine system output controllers to provide a power system inertial power output response.

First claim

What is claimed is:

1. A method for controlling a power output from a wind power system coupled with an electrical grid, wherein the wind power system comprises a wind turbine having a rotor, the method comprising:
monitoring, at a connection point of the wind power system with the electrical grid, a grid voltage of the electrical grid;
generating an internal reference voltage having an angular frequency and a phase angle;
comparing a phase angle of the grid voltage to the phase angle of the internal reference voltage to generate a quadrature component of the grid voltage;
generating, based on the quadrature component of the grid voltage, a synthetic inertial response signal representing a desired inertial response to be provided to the electrical grid by the wind power system;
applying, responsive to a magnitude of the generated synthetic inertial response signal exceeding a non-zero predefined threshold value, a power offset signal to a power set point signal of the wind power system, wherein the power offset signal includes the synthetic inertial response signal as a component;
monitoring an angular speed of the rotor;
in response to the angular speed of the rotor falling below a reference threshold, setting a recovery flag indicating that the rotor has insufficient kinetic energy to provide an inertial response;
in response to the synthetic inertial response signal exceeding the predefined threshold value, setting an inertia flag indicating that the wind power system is providing an inertial response to the electrical grid; and
performing one of:
enabling the inertia flag when the recovery flag is clear; and
disabling the inertia flag when the recovery flag is set.

2. The method of claim 1 , wherein generating the internal reference voltage having the angular frequency and the phase angle comprises:
generating a feedback signal from a mathematical product of the angular frequency of the internal reference voltage and a transfer function of a damping circuit;
subtracting the feedback signal from the synthetic inertial response to generate a difference signal;
multiplying the difference signal by a gain constant to generate an amplified difference signal;
integrating the amplified difference signal to generate the angular frequency of the internal reference voltage; and
integrating the angular frequency of the internal reference voltage to generate the phase angle of the internal reference.

3. The method of claim 1 , wherein generating the synthetic inertial response signal based on the quadrature component of the grid voltage comprises:
filtering the quadrature component of the grid voltage to produce a conditioned quadrature voltage;
multiplying the conditioned quadrature voltage by a synchronous reactance power quotient to produce a synchronous power output; and
subtracting an inertial response power reference point from the synchronous power output to generate the synthetic inertial response signal.

4. The method of claim 1 , further comprising:
processing the synthetic inertial response signal through an inertial response reference generator to generate an inertial response reference signal; and
determining the power offset signal based on the inertial response reference signal.

5. The method of claim 4 , wherein processing the synthetic inertial response signal through the inertial response reference generator further comprises: processing the synthetic inertial response signal through at least one of a gain scheduler, a dead band limiter, a ramp rate limiter, and an absolute limiter.

6. The method of claim 1 , further comprising: in response to the angular speed of the rotor decreasing below a minimum threshold, disabling the inertia flag.

7. The method of claim 1 , wherein generating a synthetic inertial response signal is based on a predefined parameter indicating a sensitivity of the wind power system to changes in the phase angle of the grid voltage, and wherein the predefined parameter is independent of the grid voltage and of an impedance of the electrical grid.

8. The method of claim 7 , wherein the predefined parameter comprises a synchronous reactance power quotient, and wherein the synchronous reactance power quotient is determined without measuring parameters of a synchronous machine and without modeling a response of the synchronous machine.

9. A method of generating a synthetic inertial response signal using a wind turbine power generation system, wherein the wind turbine power generation system comprises a wind turbine having a rotor, the method comprising:
sampling a grid voltage at a connection point;
generating an internal reference voltage having an angular frequency and a phase angle;
synchronizing, using a control loop of the wind turbine power generation system, the phase angle of the internal reference voltage to a phase angle of the grid voltage;
calculating, using the control loop, an error signal between an inertial response power reference point and a synchronous output power of the wind turbine power generation system;
applying, responsive to determining that a magnitude of the error signal exceeds a non-zero predefined threshold value, a power output adjustment to the wind turbine power generation system, wherein the power output adjustment is based on the error signal;
monitoring an angular speed of the rotor;
in response to the angular speed of the rotor falling below a reference threshold, setting a recovery flag indicating that the rotor has insufficient kinetic energy to provide an inertial response;
in response to the synthetic inertial response signal exceeding the predefined threshold value, setting an inertia flag indicating that the wind turbine power generation system is providing an inertial response to the electrical grid via the power output adjustment; and
performing one of:
enabling the inertia flag when the recovery flag is clear; and
disabling the inertia flag when the recovery flag is set.

10. The method of claim 9 , wherein the control loop is configured to generate a step response such that the error signal produced in response to a change in the phase angle of the grid voltage produces a synthetic inertial response signal from the wind turbine power generation system.

11. The method of claim 9 , wherein the synthetic inertial response signal is configured to counter a change in the grid voltage.

12. A wind power system for providing power to an electrical grid, the wind power system comprising:
one or more wind turbine systems, wherein each wind turbine system includes:
a rotor,
a generator coupled to the rotor, and
a power converter coupling the generator with the electrical grid at a connection point, wherein the power converter is configured to transfer at least a part of the generated power from the wind turbine to the electrical grid; and

a central controller operatively coupled to the one or more wind turbine systems, the central controller configured to:
generate a synthetic inertial response signal representing a desired inertial response to be provided to the electrical grid by the wind power system;
apply, responsive to a magnitude of the synthetic inertial response signal exceeding a non-zero predefined threshold value, an adjustment to a power output provided by the one or more wind turbine systems, wherein the adjustment to the power output is based on the magnitude of the synthetic inertial response signal; and
set an inertia response flag in response to the synthetic inertial response signal exceeding the predefined threshold value, the inertia response flag indicating that the wind power system is providing an inertial response to the electrical grid,

Assignees

• Tarnowski Germán Claudio
• Vestas Wind Sys As

Inventors

• Tarnowski Germán Claudio

Classifications

• H02P9/105

  for increasing the stability · CPC title

• F03D7/0284

  in relation to the state of the electric grid · CPC title

• H02J2101/28

  Wind energy · CPC title

• H02J3/00142

  Oscillations concerning frequency · CPC title

• Y02E10/723

  Cross-Sectional Technologies · mapped topic