Uninterruptible power supply apparatus and power path transfer method

• US 4,782,241 A
• Filed: 08/11/1987
• Issued: 11/01/1988
• Est. Priority Date: 08/11/1987
• Status: Expired due to Term

• Current Assignee: Liebert Corporation (Vertiv Holdings Co.)
• Original Assignee: Liebert Corporation (Vertiv Holdings Co.)
• Inventors: Orsak, Leonard E., Martin, James K., Baker, Robert W.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Logan, Sharon D.
• Application Number:
  US07/084,305
• Time in Patent Office: 448 Days
• Field of Search: 307/66, 307/64, 307/87, 307/85, 307/86, 323/267, 323/308
• US Class Current: 307/66
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

An uninterruptible power supply capability is provided for line regulators of a variety synthesizing a desired waveshape for presentation to a critical load. A static switch is active intermediate the input of the line regulator and the line power supply to provide a power path during normal operation. Upon the occurrence of a line defect, a stand-by power path is provided which includes a source of d.c. stand-by energy such as rechargeable batteries which supply input to an unregulated inverter which, in turn, provides an unregulated input through an inductance to the input of the line regulator. Transfer is achieved by preliminary voltage level adjustment at the inverter and the inverter itself is employed to assure commutation off of the switching components of the static switch. Detection of line fault is made by detecting any instantaneous phase shift in the line input.

Claims

1. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein including defects discernable from phase information to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter.

2. The apparatus of claim 1 including:

precharge circuit means coupled with said inverter d.c. energy storing bus means for providing, when activated, a d.c. voltage thereat having a predetermined transfer value; and

said control means is responsive to the presence of said predetermined transfer value as a condition for effecting said transfer of power flow.

3. The apparatus of claim 1 in which:

said control means includes line monitoring means responsive to said line power source for deriving instantaneous phase information corresponding therewith; and

said control means is responsive to predetermined values of variation of said instantaneous phase information as a said predetermined defect.

4. The apparatus of claim 1 in which said control means includes:

line monitoring means responsive to said line power source for deriving instantaneous phase information corresponding therewith;

an inverter oscillator controllable to provide said switch control signals;

phase lock network means controllable for selectively synchronizing said switch control signals with said instantaneous phase information; and

comparison means responsive to instantaneous phase deviation of predetermined value between said switch control signals in the presence of said synchronization and said line monitoring means instantaneous phase information for deriving an instantaneous phase error signal as a said predetermined defect.

5. Apparatus for use with a waveform synthesizing line regulator having an input connectable with a line power source of given frequency, voltage and sinusoidal waveform, comprising:

static switch means connectible intermediate said source and said line regulator input, actuable into a conducting state and commutatable to a non-conducting condition in the absence of said actuation;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing means for connection in energy exchange relationship with said stand-by source, solid-state switch means responsive to switch control signals to derive an unregulated, substantially square waveform from said d.c. energy storing means at an inverter output;

inductor means connectable intermediate said inverter output and said line regulator input for effecting current flow limitation; and

control means including;

transfer circuit means comprising;

line responsive means for monitoring the condition of said line power source and having a transfer condition in response to predetermined defects of said power source,

an inverter oscillator for providing select said switch control signals,

phase lock network means controllable for selectively synchronizing said switch control signals with said line power source waveform,

transfer control means responsive to said transfer condition for effecting said static switch means commutation and applying said switch control signals to said solid-state switch means to derive said square waveform at said inverter output for application to said line regulator input through said inductor means; and

reacquire circuit means for transferring power flow to said line regulator input from said inverter and stand-by source of d.c. power to said line power source, comprising graduated firing circuit means responsive to said line monitoring means for deriving a reacquire switching output for effecting a select actuation of said static switch means during each half cycle of said sinusoid waveform to sum energy therefrom with said inverter square waveform and effect a corresponding elevation of the voltage amplitude at said inverter d.c. energy storing means until a correspondence thereof with the peak voltage amplitude of said line power source waveform is developed, said reacquire circuit means fully actuating said static switch means substantially when said correspondence is achieved.

6. The apparatus of claim 5 in which said reacquire circuit means includes phase control means for effecting a predetermined variance between the zero cross-over occasions of said inverter square waveform and said line source sinusoidal voltage waveform.

7. The apparatus of claim 5 in which said reacquire circuit means includes:

non-overlapping wave generator means for deriving a non-overlapping oscillatory output from said inverter oscillator having a waveform transition occurring non-simultaneously with corresponding transitions of said switch control signals; and

interlock network means for effecting synchronizing enablement of said reacquire switching output with said non-overlapping oscillatory output so as to isolate switching events at said inverter switch means from switching events at said static switch means.

8. The apparatus of claim 5 in which said control means includes:

line monitoring means responsive to said line power source for deriving instantaneous phase information signals corresponding with said given graduated firing circuit means includes;

ramp current means for generating ramp signals of voltage varying at a predetermined rate from a first to a second level; and

ramp-phase comparator means responsive to said ramp signals and to said instantaneous phase information signals for deriving said require switching output.

9. The apparatus of claim 8 in which said reacquire circuit means includes ramp terminate detect network means responsive to said ramp signal voltage reaching said second level to effect said full actuation of said static switch means.

10. The apparatus of claim 5 in which said transfer circuit means includes:

precharge circuit means coupled with said inverter d.c. energy storing means for providing, when activated, a d.c. voltage thereat having a predetermined transfer value corresponding with the peak said voltage of said line power source; and

said control means effects said precharge circuit means activation when said static switch means is in said conducting state.

11. The apparatus of claim 5 in which;

said line monitoring means is responsive to said line power source for deriving instantaneous phase information corresponding therewith and derives said transfer condition in response to predetermined values of variation of said instantaneous phase information.

12. The apparatus of claim 5 in which said transfer circuit means includes commutation circuit means for commutating said static switch means to said non-conducting state by select application of said switch control signals to said inverter solid-state means.

13. The apparatus of claim 12 in which said transfer circuit means includes:

precharge circuit means coupled with said inverter d.c. energy storing means for selectively grounding a d.c. transfer value corresponding with the peak said voltage of said line power source.

14. The apparatus of claim 12 in which said transfer circuit means includes commutation interval timing means responsive to said transfer condition for deriving a predetermined interval within which said commutation of said static switch means is carried out to achieve said non-conducting state.

15. The apparatus of claim 5 in which:

said transfer circuit means line responsive means is responsive to said line power source for deriving instantaneous phase information corresponding therewith; and

said line response means further includes comparison means responsive to to said switch control signals occurring in the presence of said phase lock network means synchronization and to said line responsive means instantaneous phase information for detecting the presence of phase deviation therebetween to derive said transfer condition.

16. The apparatus of claim 5 in which said transfer control means includes:

static switch current monitoring means responsive to the direction of current through said static switch means for providing static switch current signals corresponding therewith;

direction network means responsive to a commutate signal and to said static switch current signals for deriving select commutating said switch control signals in correspondence therewith to effect commutation of said static switch means to said non-conducting condition; and

means deriving a commutate signal in response to said transfer condition.

17. The apparatus of claim 16 in which said transfer control means includes commtuate timing means responsive to said commutate signal for effecting application of said select commutating switch control signals to said inverter solid-state switch means for a predetermined interval.

18. The apparatus of claim 16 in which said transfer circuit means includes:

inverter current monitor means responsive to current flow at said inverter and deriving an inverter overload signal when said current flow exceeds a predetermined value;

said transfer control means is responsive to said inverter overload signal to terminate said communate signal; and

includes retry timing means responsive to said inverter overload signal for reinstating said commutate signal a predetermined interval following said termination thereof.

19. The apparatus of claim 16 in which said transfer control means includes:

cross-over detect means responsive to said static switch current signals for deriving a cross-over detect signal;

delay means responsive to the occurrence of a said cross-over detect signal for deriving a timing signal a predetermined interval following the occurrence of said cross-over detect signal; and

said inverter transfer means is responsive to said delay means to inhibit said commutate signal until the occurrence of said timing signal.

20. An uninterruptible power supply system connectable between a load and a line power source of given frequency, variable voltage and waveshape, comprising:

static switch means having an input connectable with said line power source and controllable to selectively convey power from said input to an output thereof;

auxiliary power means for providing a standby d.c. source;

an inverter having an input connected with said d.c. source for providing an a.c. power output substantially at said given frequency at an inverter output;

line regulator means connectable with said load, having an input coupled with said inverter output and with said static switch output for synthesizing an output waveform of regulated voltage substantially at said given frequency;

inductor means coupled intermediate said line regulator means input and said inverter output for effecting current flow limitation; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein to terminate said conveyance of power by said static switch means and to effect said provision of a.c. power output from said inverter to said line regulator input.

21. In an uninterruptible power supply system in which a first power path is provided wherein line input a.c. power of first phase is applied through a static switch having actuable switching components to the input of a waveshape synthesizing line regulator coupled to a load, and wherein a second power path is provided in which a stand-by source of d.c. power supplies stand-by power to said regulator input through an inverter having switching components actuable for switching an applied d.c. voltage to derive an unregulated squarewave output of second phase, the method for transferring from said second power path to said first power path comprising:

providing an inductor in common with the outputs of said static switch and said inverter;

synchronizing said first and second phases in a manner wherein one is retarded a predetermined amount with respect to the other;

actuating said static switch switching components to conduct during portions of the cycles of said line input to effect conveyance of gradually increasing amounts of cycle defined energy to said inductor for voltage summing with said squarewave to gradually elevate the value of said applied d.c. voltage; and

deactivating said inverter switching components when said applied d.c. voltage corresponds with the peak values of voltage exhibited by said line input a.c. power.

22. The method of claim 21 including the step of interlocking said inverter squarewave output with the activation of said static switch components in a manner wherein said static switch components are not actuated simultaneously with the actuation of said inverter switching components.

23. In an uninterruptible power supply system in which a first power path is provided wherein line input a.c. power of given peak voltage level and frequency is applied through a static switch, having switching components actuable between on and commutatable off states, to the input of a waveshape synthesizing line regulator, and wherein a second power path is provided in which a stand-by source of d.c. power supplies stand-by power to said regulator input through an inverter having switch components actuable for switching an applied d.c. inverter voltage to derive a time varying output, the method for transferring from said first power path to said second power path, comprising:

monitoring currents through said static switch switching components and deriving direction signals representing the direction thereof;

actuating said static switch switching components to said commutatable off state;

actuating said inverter switch components in correspondence with said direction signals to effect commutation off of said static switch switching components;

determining whether the said commutation is effective or ineffective; and

actuating said inverter switch components to derive said time varying output at said give frequency when said commutation is determined to be effective.

24. The method of claim 23 including the step of precharging said applied d.c. inverter voltage to a level corresponding with said line input given peak voltage level.

25. The method of claim 23 in which:

said step of actuating said inverter switch components in correspondence with said direction signals is carried out for a predetermined interval;

including the step of deriving corrected said direction signals when said commutation is determined to be ineffective during said predetermined interval; and

actuating said inverter switching components in correspondence with said corrected direction signals to effect commutation of said static switch switching components off.

26. The method of claim 23 including the step of providing inductance to limit current flow through said inverter.

27. In an uninterruptible power supply system wherein line input a.c. power of given phase and frequency is applied to a load and wherein an inverter is employed having switch components actuated from the time varying output of an oscillator the frequency and phase of which is controllable for synchronization with said line input by a phase lock loop, the method for detecting a defect in said input comprising the steps of:

monitoring said line input to provide a corresponding time varying line signal;

comparing said time varying signal with said time varying output of said oscillator when controlled by said phase lock loop; and

determining the presence of said defect when the phase of said time varying line signal deviates from the phase of said controlled oscillator time variable signal.

28. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch controls signal;

inductor means connectable intermediate said inverter output and said line regulator input for effecting current flow limitation; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter.

29. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals;

precharge circuit means coupled with said inverter d.c. energy storing bus means for providing, when activated, a d.c. voltage thereat having a predetermined transfer value corresponding with said line power source given peak value; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter and further responsive to the presence of said predetermined transfer value as a condition for effecting said transfer of power flow.

30. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals; and

control means for monitoring the condition of said line power source including;

cross-over detection network means responsive to said line power source waveshape for deriving a cross-over detect signal corresponding with a zero crossing of said source waveshape,

delay means responsive to said cross-over detect signal for deriving a timing signal following a predetermined interval within a period of a half cycle of said waveshape,

said control means being responsive to said timing signal and to predetermined defects of said line power source to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter.

31. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals; and

control means for monitoring the condition of said line power source, and responsive to predetermined defects therein to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter, said control means including;

static switch current monitoring means for providing a static switch current signals,

direction network means responsive to said static switch current signals and to a commutate signal for deriving select said switch control signals in correspondence therewith to effect commutation of said static switch means into said non-conducting state, and

inverter transfer circuit means for deriving said commutate signal on the occurrence of a said predetermined defect.

32. The apparatus of claim 31 in which said control means includes commutate timing means responsive to said commutate signal for effecting application of said select switch control signals to said inverter solid-state switching means for a predetermined interval.

33. The apparatus of claim 32 in which said control means includes commutation timing means responsive to said commutate signal for effecting the application of said select switch control signals for a predetermined commutation interval.

34. The apparatus of claim 31 including:

precharge circuit means coupled with said inverter bus means for providing, when activated, a d.c. voltage thereat having a predetermined transfer value corresponding with said line power source given peak value; and

aid control means is responsive to the presence of said predetermined transfer value as a condition for effecting said transfer of power flow.

35. The apparatus of claim 31 in which said control mean includes:

inverter current monitor means responsive to current flow at said inverter and deriving an inverter overload signal when said current flow exceeds a predetermined value;

said inverter transfer circuit means is responsive to said inverter overload signal to terminate said commutate signal; and

including retry timing means responsive to said inverter overload signal for reinstating said commutate signal a predetermined interval following said termination thereof.

36. The apparatus of claim 31 in which said control means includes:

cross-over detect means responsive to said static switch current signals for deriving a cross-over detect signal;

delay means responsive to the occurrence of a said cross-over detect signal for deriving a timing signal a predetermined interval following the occurrence of said cross-over detect signal; and

said inverter transfer circuit means is responsive to said delay means to inhibit said commutate signal until the occurrence of said timing signal.

37. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein to actuate said static switch from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter, said control means including;

commutation interval timing means responsive to said predetermined defects for deriving a predetermined interval for carrying out a commutation of said static switch means to achieve said non-conducting state, and

commutation circuit means for communating said static switch means to said non-conducting state by select application of said switch control signals to said inverter solid-state switching means.

38. Apparatus for use with a waveform synthesizing line regulator having an input and an output connectable with a load, said apparatus being connectable with a line power source of given frequency, variable voltage of given peak value and waveshape and comprising:

static switch means connectable intermediate said source and said line regulator input and actuable between conducting and non-conducting states for selectively conveying power from said source to said regulator input;

means deriving a stand-by source of d.c. power;

an inverter including d.c. energy storing bus means for connection in energy exchange relationship with said stand-by source, solid-state switch means coupled with said bus means and responsive to switch control signals to provide an inverter active state for deriving an unregulated power input to said line regulator input at said given frequency, and said inverter having a non-switching stand-by state in the absence of said switch control signals; and

control means for monitoring the condition of said line power source and responsive to predetermined defects therein to actuate said static from said conducting to said non-conducting state and to apply said switch control signals to said solid-state switching means so as to provide said active state control of said inverter and effect a transfer of power flow from said static switch means to said inverter, said control means including commutation circuit means for commutating said static switch means to said non-conducting state by select application of said switch control signals to said inverter solid-state switching means.

39. The apparatus of claim 38 in which said control means includes:

precharge circuit means coupled with said inverter bus means for providing, when activated, a d.c. voltage thereat having a predetermined transfer value corresponding with said line power given peak value; and

said control means effects said precharge circuit means activation when said static switch means is in said conducting state.