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A power electronic based DR (distributed resource e.g., a UPS (uninterrupted power supply), Fuel Cell or Microturbine) is controlled to emulate a voltage source behind an impedance and behave as a power system stabilizer. The impedance in the DR is emulated and an estimate of impedance at the power/

A power electronic based DR (distributed resource e.g., a UPS (uninterrupted power supply), Fuel Cell or Microturbine) is controlled to emulate a voltage source behind an impedance and behave as a power system stabilizer. The impedance in the DR is emulated and an estimate of impedance at the power/electronic interface is derived and applied to the control of the DR in a manner wherein the power and voltage swings on systems (loads) that otherwise would have difficulty with dynamic loads, are stabilized. Damping and synchronizing power are provided measuring only voltage, current and frequency at the interface between the DR and the load. The DR may include some energy storage.

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1. A power-electronic based DR (distributed resource) control arrangement which causes the DR to emulate a voltage source behind an impedance and stabilize power supplied to a load, the control arrangement receiving signals indicative of current (i s ), voltage (ν s ) and calculated power (P

1. A power-electronic based DR (distributed resource) control arrangement which causes the DR to emulate a voltage source behind an impedance and stabilize power supplied to a load, the control arrangement receiving signals indicative of current (i s ), voltage (ν s ) and calculated power (P s ) at an interface between the DR and the load, the control arrangement including circuitry which utilizes the signals indicative of interface current (i s ), voltage (ν s ) and calculated power (P s ) and which:generates an internal frequency and internal angle references;compares internal frequency reference with a measured power frequency;uses the frequency difference to modulate power command for damping control of load power oscillations;determines a current magnitude and phase angle for DR output utilizing the specified emulated impedance. 2. A power-electronic based DR control arrangement as set forth in claim 1, wherein the load comprises a power supply grid. 3. A power-electronic based DR control arrangement as set forth in claim 1, wherein the load comprises a power supply line and at least one electrical device connected thereto. 4. A power-electronic based DR control arrangement as set forth in claim 1, wherein the load comprises a grid and a power supply one to which at least one electrical device is connected, connected in parallel. 5. A power-electronic based DR control arrangement as set forth in claim 1, wherein the load comprises a microgrid. 6. A power-electronic based DR control arrangement as set forth in claim 1, wherein the load comprises a large grid having a least one other power supply. 7. A control arrangement associated with a DR (distributed resource) for controlling the DR on the basis of a voltage measurement signal (ν s ), a current measurement signal (i s ) and a calculated power measurement signal (P s ) from an interface between the load and the DR, the control arrangement comprising:a power control section which is responsive to the system voltage measurement signal (ν s ) and the system current measurement signals (i s ), which generates a system frequency signal ({tilde over (ω)} s ) and a system voltage signal (V s ) based on the system voltage measurement signal (ν s ), a voltage angle ramp (γ s ), and system current measurement signals (i s ), and which compares the system frequency signal ({tilde over (ω)} s ) with a reference frequency signal ({tilde over (ω)}*) and modifies the system power measurement signal (P s ) to produce an internal power angle signal (δ i ); anda voltage control section which determines an error between the system voltage signal (V s ) with a reference voltage (v*) and produces an internal voltage signal (V i ). 8. A control system as set forth in claim 7, further comprising an impedance emulation section which is responsive to the internal power angle signal (δ i ), the internal voltage signal (V i ) and the system voltage signal (V s ) and which outputs a system current control signal (I s ) and an angle control signal (θ s ) which are used to control the distributed resource. 9. A control system as set forth in claim 7, wherein the power control section includes:a frequency regulation circuit which responds to the difference between the system frequency signal ({tilde over (ω)} s ) with a reference frequency signal ({tilde over (ω)}*) and produces a power reference signal (P*); andphase shift loop which phase shifts a difference between the system frequency signal ({tilde over (ω)} s ) with a reference frequency signal ({tilde over (ω)}*) and modifies the power reference signal (P*) with the phase shifted difference and produces a correction in the internal power angle signal (δ i ) which induces a frequency variation damping effect. 10. A control system as set forth in claim 7, wherein the impedance emulation section processes the interna l power angle signal, the internal voltage signal and the system voltage signal on the basis of the following equations: V i cos δ i −RI s cos θ s +XI s sin θ s =V s   (1 V i sin δ i −XI s cos θ s −RI s sin θ s =0  (2wherein:δ i denotes the angle between V i and V s ;δ s denotes the angle between I s and V s ;V i denotes internal voltage;V s denotes system voltage signal;I s denotes system current magnitude control signal. 11. A control system as set forth in claim 7, wherein the frequency control section includes a system measurement circuit which receives the system voltage measurement signal (ν s ) and the system current measurement signal (i s ) and outputs the system voltage signal (V s ) and system power (P s ); and a phase lock loop circuit which outputs the system frequency signal ({tilde over (ω)} s ) and a system angle ramp signal (γ s ). 12. A method of controlling a power electronic based DR (distributed resource) in a manner that emulates a voltage source behind an impedance and stabilizes power supplied to a load operatively associated with the DR, comprising:sensing system current (i s ) and system voltage (ν s ), at the output of the DR, and based on the one or more of the signals indicative of system current (i s ) and system voltage (ν s ) implementing the steps of:generating an internal frequency and internal angle references;comparing internal frequency with a measured power system frequency;using the frequency difference to modulate power command for damping control of grid power oscillations;determining, based on the estimated impedance, a current magnitude and phase angle for DR output. 13. A method of controlling a DR (distributed resource) so as to behave as a power system stabilizer comprising the steps of:detecting a system voltage measurement signal (ν s ) and a system current measurement signal (i s ) at the DR output;using the system voltage measurement signal (ν s ) and the system current measurement signal (i s ) to develop a system voltage control signal (V s ) and system power measurement signal (P s );using a phase lock loop on system voltage signal (ν s ) to produce a system frequency signal ({tilde over (ω)} s ) and a phase angle ramp signal (γ s ) indicative of the rotating phase angle of the system voltage (ν s );modifying the system frequency signal ({tilde over (ω)}s) with a reference frequency signal({tilde over (ω)}*) and the system power measurement signal (P s ) to generate a modified system frequency signal;frequency regulating the modified system frequency signal to develop a power reference signal (P*);generating a phase correction signal by phase shifting a signal based on a difference between the system frequency signal({tilde over (ω)}s) and the reference frequency signal({tilde over (ω)}*);modifying the power reference signal (P*) with the phase correction signal;power regulating the modified power reference signal to develop an internal power angle signal (δ i );Regulating an voltage error signal derived using a reference voltage and generating an internal voltage signal (V i );using the internal voltage system (V i ), the internal power angle signal (δ i ) and the system voltage control signal V s to emulate a voltage source behind an impedance and to output a system current control signal (I s ) and a system angle control signal (θ s ) indicative of the angle between the system current control signal (I s ) and the system voltage control signal (V s );modifying the system angle control signal (θ s ) with the system frequency ramp signal (γ s ) and internal ramp signal (γ i ) to produce a modified system angle control signal (γ so ); andoutputting the modified system angle co ntrol signal and the system current control signal (I s ) to the DR. 14. An apparatus for controlling a DR (distributed resource) so as to behave as a power system stabilizer, comprising:means for detecting a system voltage measurement signal (ν s ) and a system current measurement signal (i s ) from the DR;means for using the system voltage measurement signal (ν s ) and the system current measurement signal (i s ) to develop a system voltage control signal (V s ) and a system power measurement signal (P s );means to phase lock loop on system voltage control signal (ν s ) to produce a system frequency signal ({tilde over (ω)}s) and a phase angle ramp signal (γ s ) indicative of the rotating phase angle of system voltage (ν s );means for modifying the system frequency signal ({tilde over (ω)}s) with a reference frequency signal ({tilde over (ω)}*) and the system power measurement signal (P s ) to generate a modified system frequency signal;means for frequency regulating the modified system frequency signal to develop a power reference signal (P*);means for generating a phase correction signal by phase shifting a signal based on a difference between the system frequency signal({tilde over (ω)}s) and the reference frequency signal({tilde over (ω)}*);means for modifying the power reference signal (P*) with the phase correction signal;means for power regulating the modified power reference signal to develop an internal power angle signal (δ i );means for regulating an voltage error signal derived using a reference voltage and generating an internal voltage signal (δ i );means for using the internal voltage system (V i ), the internal power angle signal (δ i ) and the system voltage control signal V s to emulate a voltage source behind an impedance and to output a system current control signal (I s ) and a system angle control signal (θ s ) indicative of the angle between the system current control signal (I s ) and the system voltage control signal (V s );means for modifying the system angle control signal (θ s ) with the system frequency ramp signal (γ s ) and internal ramp signal (γ i ) to produce a modified system angle control signal (γ so ); andmeans for outputting the modified system angle control signal and the system current control signal (I s ) to the DR.