Abstract:
A method for generating and controlling power by means of at least one controlled permanent magnet machine (PMM) with a permanent magnet (PM) rotor and a stator with a magnetic flux diverter circuit for controlling the output of the PMM, comprises the steps of: rotating the PM rotor at a velocity sufficient to develop a high frequency alternating current (HFAC) power output from the stator; transforming the HFAC output to produce a desired non-HFAC power output; sensing desired power output parameters; generating a control signal responsive to the sensed parameters; and applying the control signal to the magnetic flux diverter circuit to control the desired power output.

Description:
FIELD OF THE INVENTION 
     The invention relates to electric power generation systems, and more particularly to prime mover driven electric power generation systems with power regulation by means of magnetic flux control. 
     BACKGROUND OF THE INVENTION 
     It is of great importance to minimize the size and weight of electric power generation and regulation systems for mobile applications. Such power generation and regulation systems generally derive electrical power for their operation from a mechanical source that comprises a prime mover, such as an engine. An electrical generator converts mechanical power from the prime mover into electrical power. Regulation of such systems has generally involved the use of a wound field synchronous machine (WFSM) with exciter control or a permanent magnet machine (PMM) with high power electronic regulation of a direct current (DC) output or DC link. Both of these options involve increased cost and weight. 
     SUMMARY OF THE INVENTION 
     The invention generally comprises a method for generating and regulating power by means of at least one controlled permanent magnet machine (PMM) with a permanent magnet (PM) rotor and a stator with a magnetic flux diverter circuit for controlling the output of the PMM, comprising the steps of: rotating the PM rotor at a velocity sufficient to develop a high frequency alternating current (HFAC) power output from the stator; transforming the HFAC output to produce a desired non-HFAC power output; sensing desired power output parameters; generating a control signal responsive to the sensed parameters; and applying the control signal to the magnetic flux diverter circuit to control the desired power output. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a power generation and regulation system according to a first embodiment of the invention. 
         FIG. 2  is a schematic diagram of a power generation and regulation system according to a second possible embodiment of the invention. 
         FIG. 3  is a schematic diagram of a power generation and regulation system according to a third possible embodiment of the invention. 
         FIG. 4  is a schematic diagram of a power generation and regulation system according to a fourth possible embodiment of the invention. 
         FIG. 5  is a schematic diagram of a power generation and regulation system according to a fifth possible embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic diagram of a power generation and regulation system  2  according to a first embodiment of the invention. The power system  2  comprises a prime mover  4 , such as a gas turbine engine, that couples to at least one high frequency alternating current (HFAC) generator module  6  by means of a prime mover drive shaft  8 . The HFAC generator module  6  includes a desired direct current (DC) power output that an electrical load  10  receives by way of generator module output lines  12 . 
     The generator module  6  comprises a single phase controlled permanent magnet machine (PMM)  14  that serves as a HFAC generator, such as of the type described in U.S. Pat. No. 8,085,003to Gieras et al., owned by the assignee of this application and hereby incorporated by reference. Each PMM  14  has a permanent magnet (PM) rotor  16  and a stator  18  with a winding  19  and a magnetic flux diverter circuit  20 . The prime mover  4  rotates the PM rotor  16  by way of the prime mover drive shaft  8  at a velocity sufficient to develop a HFAC current in the stator  18 . The winding  19  of the stator  18  has a centre-tapped single phase output with a centre tap to provide a balanced single phase HFAC output on stator output lines  22  with respect to the centre tap on stator neutral line  24 . 
     A power transformation circuit  26 , shown as a synchronous rectification circuit in  FIG. 1 , receives the balanced single phase HFAC output on the stator output lines  22  and transforms it to produce the desired DC output of the generator module  6  on its respective generator module output line  12 . A current sensor  28  may monitor the current level of the desired DC power output on the generator module output lines  12  and generate a respective current feedback signal on a current feedback line  30  that is representative of the sensed current level. An electrical potential difference sensor  32  may monitor the level of potential difference between the generator output lines  12  and generate a respective electrical potential difference feedback signal on a potential difference feedback line  34  that is representative of the sensed potential difference level. A low-pass filter network  36  coupled to the output of the power transformation circuit  26 , comprising output filter inductors  38  and output filter capacitor  40 , filters any HFAC content from the generator module output lines  12 . 
     A current limit look-up table circuit  42  receives the current feedback signal on the current feedback line  30  and generates an electrical potential difference offset signal on a look-up table output line  44  that is representative of a value of potential difference needed to limit current to a desired level. A summer  46  receives a desired electrical potential difference reference signal on a DC electrical potential reference level line  48  and the electrical potential difference offset signal on the look-up table output line  44  to generate a compensated electrical potential difference reference signal on a summer output line  50  that is representative of the difference. 
     An electrical potential difference regulator circuit  52  receives the compensated electrical potential difference reference signal on the summer output line  50  and the electrical potential difference feedback signal on the potential difference feedback line  34  and generates on a control current reference signal line  54  a control current reference signal that is responsive to the difference. A control current regulator circuit  56  receives the control current reference signal on the control current reference line  54  and a control current feedback signal on a control current feedback line  58  and generates on a magnetic flux diverter circuit current drive line  60  a magnetic flux diverter circuit current drive signal that is responsive to the difference. 
     An H-bridge  62  receives the magnetic flux diverter circuit current drive signal on the magnetic flux diverter circuit current drive line  60  to produce a magnetic flux diverter circuit current on H-bridge output lines  64 . The magnetic flux diverter circuit  20  receives the magnetic flux diverter circuit current on the H-bridge output lines  60  to control the level of the balanced single phase HFAC output on the stator output lines  22 . A magnetic flux diverter circuit current sensor  66  senses the level of magnetic flux diverter current passing through the H-bridge output lines  64  and generates the control current feedback signal on the control current feedback line  58  to be representative of the sensed current level. 
     A zero crossing detector circuit  68  senses the zero crossings of the HFAC output signal on one of the stator output lines  22  relative to the stator neutral line  24  and generates a zero crossing output signal on a zero crossing output signal line  70  and an inverted zero crossing output signal on an inverted zero crossing output line  72 . A first synchronous rectifier drive circuit  74  in the power transformation circuit  26  receives the zero crossing output signal by way of the zero crossing output line  70  and generates a respective first gate drive signal to drive a respective first synchronous rectifier  76  and control current flow between one of the stator output lines  22  and one of the generator module output lines  12 . A second synchronous rectifier gate drive circuit  78  receives the inverted zero crossing output signal by way of the inverted zero crossing output signal line  72  and generates a respective second gate drive signal to drive a respective second synchronous rectifier  80  and control current flow between the other one of the stator output lines  22  and the generator module output line  12 . 
       FIG. 2  is a schematic diagram of the power generation and regulation system  2  according to a second possible embodiment of the invention. Similar to the first embodiment, the motor drive system  2  comprises a prime mover  4 , but it couples to a generator module  82  by way of the prime mover drive shaft  8 . However, the generator module  82  generates a desired low frequency AC power on the generator module output line  12 . 
     The generator module  82  comprises the PMM  14  as described in connection with the generator module  6 . It has the same PM rotor  16  and the stator  18  with the magnetic flux diverter circuit  20 . Likewise, the prime mover  4  rotates the PM rotor  16  by way of the prime mover drive shaft  8  at a velocity sufficient to develop a HFAC current in the stator  18 . The stator  18  again has a centre-tapped single phase output with the centre tap grounded to provide a balanced single phase HFAC output with respect to the centre tap on stator neutral line  24 . 
     The power transformation circuit  26 , shown as a bi-directional switching circuit in  FIG. 2 , receives the balanced single phase HFAC output on the stator output lines  22  and transforms it to produce the desired single phase low frequency AC output of the generator module  82  on it generator module output line  12 . The module also includes the low-pass filter network  36  coupled to the output of the power transformation circuit  26 , shown in  FIG. 2  as two commutating inductors  84  to limit bi-directional current within the power transformation circuit  26  during commutation, an output filter inductor  86  and an output filter capacitor  88 . The current sensor  28  may monitor current that passes through the output capacitor  88  from the generator module output line  12  to system ground and generate an output capacitor current feedback signal on the current feedback line  30 . The electrical potential difference sensor  32  may monitor the level of potential difference between the generator output line  12  and system ground and generate a respective electrical potential difference feedback signal on the potential difference feedback line  34  that is representative of the sensed potential difference level. 
     A root-mean-square (RMS) calculation circuit  90  receives the electrical potential difference feedback signal on the potential difference feedback line  34  and generates a respective RMS potential difference signal on a measured RMS output line  92 . A summer  94  receives the RMS potential difference signal on the measured RMS output line  92  and a RMS reference level electrical potential difference signal on a RMS reference potential difference line  96  that represents the desired level of electrical potential difference for the low frequency AC power output on the generator module output line  12  and generates an electrical potential difference error signal on a summer output line  98  that is representative of the difference. 
     An RMS proportional-plus-integral (PI) controller  100  receives the error signal on the summer output line  98  and generates a corresponding PI controller output signal on an RMS controller output line  102 . 
     A sine wave generator circuit  104  generates an AC reference signal on a reference frequency line  106  with a frequency corresponding to the desired frequency of the low frequency AC output power on the generator module output line  12 . A multiplier  108  receives the PI controller output signal on the PI controller output line  102  and the AC reference signal on a reference frequency line  106  and generates an output filter capacitor current reference signal on a multiplier output line  110 . 
     A low pass filter  112  receives the output filter capacitor  88  current feedback signal on the current feedback line  30  and passes low frequency content of the output capacitor  88  current feedback signal as a filtered capacitor current feedback signal on a low pass filter output line  114 . A summer  116  receives the output filter capacitor current reference signal on the multiplier output line  110  and the filtered capacitor current feedback signal on the low pass filter output line  114  to generate an error signal on a summer output line  118 . 
     An RMS output filter capacitor current regulator  120  receives the error signal on the summer output line  118  and generates a corresponding control current reference signal on control current reference line  122 . An absolute value output circuit  124  receives the control current reference signal on the control current reference line  122  and converts it to an absolute value signal on an absolute value line  126 . 
     The control current regulator circuit  56  receives the absolute value signal on the absolute value line  126  and a control current feedback signal on the control current feedback line  58  and generates on the magnetic flux diverter circuit current drive line  60  a magnetic flux diverter circuit current drive signal that is representative of the difference. 
     The H-bridge  62  receives the magnetic flux diverter circuit current drive signal on the magnetic flux diverter circuit current drive line  60  to produce a magnetic flux diverter circuit current on H-bridge output lines  64 . The magnetic flux diverter circuit  20  receives the magnetic flux diverter circuit current on the H-bridge output lines  60  to control the level of the balanced single phase HFAC output on the stator output lines  22 . The magnetic flux diverter circuit current sensor  66  senses the level of magnetic flux diverter current passing through the H-bridge output lines  64  and generates the control current feedback signal on the control current feedback line  58  to be representative of the sensed current level. 
     The zero crossing detector circuit  68  senses the zero crossings of the desired low frequency AC power output on the generator module output line  12  by way of the electrical potential difference feedback signal on the potential difference feedback line  34  and generates a zero crossing output signal on the zero crossing output signal line  70  and an inverted zero crossing output signal on the inverted zero crossing output line  72 . 
     A first bi-directional gate drive circuit  128  in the power transformation circuit  26  receives the zero crossing output signal by way of the zero crossing output line  70  and generates a respective first gate drive signal to drive a respective first bi-directional switch  130  and control current flow through a respective one of the stator output lines  22  to the generator module output line  12 . A second bi-directional gate drive circuit  132  receives the inverted zero crossing output signal by way of the inverted zero crossing output signal line  72  and generates a respective second gate drive signal to drive a respective second bi-directional switch  134  and control current flow between the other one of the stator output lines  22  and the generator module output line  12 . 
     Since the control current reference signal on the control current reference line  122  is a rectified fundamental frequency that represents the desired frequency of the variable low frequency AC output of its respective generator module  82  on its respective generator module output line  12 , the action of the generator module  82  is that of an electromechanical amplifier, wherein the control current reference signal on the control current reference line  122  may be of low power to control the high power of the desired low frequency output on the generator module output line  12 . Another way of looking at the action is that the relatively low power control current reference signal on the control current reference line  122  by means of the magnetic flux diverter circuit  20  modulates the HFAC output on the stator output lines  22  and the power transformation circuit  26  demodulates the HFAC output on the stator output lines  22  to produce the high power low frequency AC output on the generator module output line  12  with the same frequency as its respective control current reference signal on the control current reference line  122 . 
     Since the output filter capacitor  88  current reference signal on the summer output line  118  is responsive to the output capacitor current feedback signal on the current feedback line  30 , the generator module  82  also maintains a sinusoidal current at the frequency of the desired low frequency AC power output on the generator module output line  12  by modulating the control current reference signal on the control current reference line  122 . This feature enables a good waveform for the desired low frequency AC power output on the generator module output line  12  even when the electrical load  10  is non-linear. 
       FIG. 3  is a schematic diagram of the power generation and regulation system  2  according to a third possible embodiment of the invention. For this embodiment, the power system has N of the generator modules  82  coupled to the prime mover  4  by the prime mover drive shaft  8  to generate N phases of output, with the power output of each generator module output line  12  shifted by 360/N degrees relative to its neighbouring generator module. By way of illustration only,  FIG. 3  shows a power system  2  with three phases using three of the generator modules  82 , with three generator module output lines  12  having outputs shifted 120 degrees relative to each other. 
     For each generator module  82  a system controller  136  generates a reference level electrical potential difference signal on a corresponding reference potential difference line  96  and an AC reference signal on a corresponding reference frequency line  106  with a frequency corresponding to the desired frequency of the low frequency AC output power. The AC reference signals will be shifted by 360/N degrees relative to each other, or 120 degrees for a three phase power system  2  as shown in  FIG. 3 . 
       FIG. 4  is a schematic diagram of the power generation and regulation system  2  according to a fourth possible embodiment of the invention. The power system  2  for this embodiment is a single phase AC system that uses a sliding mode cycloconverter system as described in co-pending patent application U.S. Ser. No. 12/435,534 to Nguyen et al., owned by the assignee and hereby incorporated by reference. The power system  2  has a generator module  138  that is similar to the generator module  82 , except that its output comprises the balanced single phase HFAC output on the stator output lines  22  and it also comprises an electrical potential difference sensor  140  that senses the level of electrical potential difference across the magnetic flux diverter circuit  20  and generates a magnetic flux diverter circuit potential difference signal on a magnetic flux diverter circuit potential difference line  142  that is representative of the sensed level. 
     A single phase sliding mode cycloconverter  144  comprises the power transformation circuit  26 , shown as a bi-directional switching circuit in  FIG. 4  with the first bi-directional gate drive circuit  128 , the first bi-directional switch  130 , the second bi-directional gate drive circuit  132  and the second bi-directional switch  134 , as described for the second embodiment of the invention in connection with  FIG. 2 . It also comprises an angle generator  146 , a sliding mode converter  148  and a signal steering block  150 , as described in Nguyen et al. The power transformation circuit  26  receives the HFAC output on the stator output lines  22  and transforms it to a desired low frequency AC power output on a cycloconverter output line  152 . 
     A low pass filter network  154 , similar to the low pass filter network  36  described for the second embodiment of the invention in connection with  FIG. 2 , comprising the output filter inductor  86 , the output filter capacitor  88 , the current sensor  28  and the electrical potential difference sensor  32 . 
     The angle generator  146  generates an angle reference frequency signal φ on an angle reference frequency line  156  that has a frequency corresponding to the frequency of the desired low frequency AC power output on the cycloconverter output line  152 . The signal steering block  148  receives the angle signal φ on the angle line  156 , the output capacitor current feedback signal on the current feedback line  30  and the electrical potential difference feedback signal on the potential difference feedback line  34  and generates a respective control signal on a sliding mode controller output line  158 . 
     The signal steering block  150  receives the control signal on the sliding mode controller output line  158  and the magnetic flux diverter circuit potential difference signal on the magnetic flux diverter circuit potential difference line  142  and generates gate drive signals for the first bi-directional gate drive circuit  128  and second bi-directional gate drive circuit  132  on respective steering block first and second drive lines  160  and  162 , thereby controlling the first bi-directional switch  130  and the second bi-directional switch  134  in the power transformation circuit  26 . 
     The root-mean-square (RMS) calculation circuit  90  receives the electrical potential difference feedback signal on the potential difference feedback line  34  and generates a respective RMS electrical potential difference signal on the measured RMS output line  92 . The summer  94  receives the RMS electrical potential difference signal on the measured RMS output line  92  and a RMS electrical potential difference reference signal on a RMS electrical potential difference reference signal line  96  to generate an error signal on a summer output line  98 . 
     The proportional-plus-integral (PI) controller  100  receives the error signal on the summer output line  98  and generates a corresponding controller output signal on the controller output line  102 . The control current regulator circuit  56  receives the controller output signal on the controller output line  102  and a control current feedback signal on the control current feedback line  58  and generates a magnetic flux diverter circuit current drive signal on the magnetic flux diverter circuit current drive line  60  that is representative of the difference. 
     The H-bridge  62  receives the magnetic flux diverter circuit current drive signal on the magnetic flux diverter circuit current drive line  60  to produce a magnetic flux diverter circuit current on H-bridge output lines  64 . The magnetic flux diverter circuit  20  receives the magnetic flux diverter circuit current on the H-bridge output lines  60  to control the level of the balanced single phase HFAC output on the stator output lines  22 . The magnetic flux diverter circuit current sensor  66  senses the level of magnetic flux diverter current passing through the H-bridge output lines  64  and generates the control current feedback signal on the control current feedback line  58  to be representative of the sensed current level. 
     The low pass filter network  154  filters HFAC content from the desired low frequency AC power output on the cycloconverter output line  152  to pass a filtered AC power output on a power output line  164 . Similar to the second embodiment of the power system  2  as described in connection with  FIG. 2 , the power system  2  according to this embodiment employs the output capacitor current feedback signal on the current feedback line  30  to adjust the output waveform of the filtered AC power output on the power output line  164  in response to non-linear loads. 
       FIG. 5  is a schematic diagram of the power generation and regulation system  2  according to a fifth possible embodiment of the invention. It is similar to the single phase power system  2  described in connection with  FIG. 4 , except it employs a multiphase cycloconverter  166  and a multiphase low pass filter network  168 . The multiphase cycloconverter  166  essentially comprises N of the single phase cycloconverters  144 , where N is the number of phases, except that the angle generator may generate N angle signals, one for each of the N phases, each of the angle signals shifted by 360/N degrees. By way of example only,  FIG. 5  shows the power system  2  with three phases. In this case, the angle generator  146  generates three angle signals, one for each phase, and the root-mean-square (RMS) calculation circuit  90  receives the electrical potential difference feedback signal on the potential difference feedback line  34  for each phase of the power system  2 . 
     The described embodiments of the invention are only some illustrative implementations of the invention wherein changes and substitutions of the various parts and arrangement thereof are within the scope of the invention as set forth in the attached claims.