Variable excitation doubly-fed switched reluctance generator current transformation system
Technical Field
The invention relates to the field of switched reluctance motor systems, in particular to a high-efficiency, low-stress and high-reliability switched reluctance generator current conversion system which can output variable excitation voltage current and charging voltage and high generation voltage, is adjustable and can feed back the electric energy of an excitation power supply in a reverse direction and a control method thereof.
Background
Switched reluctance motors are increasingly receiving attention from the industry as a motor with obvious advantages of simple structure, low cost, strong fault tolerance, convenient heat dissipation, high reliability and the like.
Compared with a mainstream generator, the switched reluctance generator has certain advantages, but the development of a current conversion system of the switched reluctance generator is slower.
The switched reluctance generator has the advantages that each phase winding is put into operation in a time-sharing mode according to the relative position relation of the stator and the rotor during operation, each phase winding is divided into two major phases of excitation and power generation during operation and is carried out in a time-sharing mode, the excitation phase absorbs electric energy, the power generation phase generates electric energy, and the switch reluctance generator is significant only when the generated electric energy is obviously larger than the absorbed electric energy, and in order to generate electric energy as much as possible, the excitation phase needs to establish excitation current as soon as possible, and the time as short as possible is reserved for the power generation phase for more time, so that the switch reluctance generator has important significance in strengthening excitation capacity.
In the operation of a traditional switched reluctance generator system, control variables are generally a switching angle and exciting current, the exciting current generally adopts a chopping mode and is limited to low-speed operation, so that the exciting voltage is provided as a variable, the exciting current is finally adjusted, and the excitation adjustment is certainly a great technical progress if the excitation adjustment can be smoothly and continuously adjusted, the adjustment range is wide, and electric energy is not wasted in the process.
Generally, the power supply voltage required by a user side, namely a load side or a power grid side, is far greater than the voltage directly output by the generator, so that a special boosting link device is required, and if the boosting link is integrated into a switched reluctance generator converter system, the method has important significance.
The output generated voltage needs high voltage, but the industry usually ignores another development opportunity, according to the mathematical model of the switched reluctance generator, the relationship between the motion electromotive force and the generated voltage directly involves the variation trend of the winding current in the generation stage, namely directly relates to the generated output electric power, which is obviously very important, but the motion electromotive force and the generator rotating speed are directly related, in some occasions such as variable speed wind power generation, the rotating speed is often forced to change, if the generated voltage is not changed, the generation output capability or the generation range is greatly influenced, the generation efficiency and benefit are reduced, if the generated voltage becomes a variable, the generation voltage is completely different, the flexibility and the adaptability are instantly increased, the significance is achieved, on the other hand, the generation voltage can be adjusted, the opportunity is brought to the load side, for example, when some loads or networks need to adjust the generated voltage to adapt to the needs of the generator, in summary, an adjustable generation voltage is of great importance.
According to a mathematical model and an operation principle of the switched reluctance generator, when a power generation stage is finished, if the current in the phase winding is not timely reduced to zero, the phase winding is bound to enter an electric working condition area, so that the power generation efficiency is reduced.
In a switched reluctance generator converter system, a switching tube, which is often a fully-controlled power electronic switching device, is necessary to protect the devices, especially the buffer absorption function, which is often accompanied with the loss of electric energy, and certainly, if the buffer absorption energy can be released to the power generation output end, the power generation efficiency of the system must be improved; furthermore, the problem of reducing losses in switching tubes, in particular in high-frequency switching, i.e. the implementation of soft switching, is also an important way to improve efficiency and reliability; for a converter device which needs a switched reluctance generator to output high voltage, the problem of voltage stress of a switching tube is also a big problem, if the voltage stress is too large, the number of the switching tubes connected in series must be increased, even the switching tubes cannot be selected, and the like, so that the cost and complexity of a converter system are increased, and even a bottleneck is met.
The storage battery is adopted as the excitation power supply of the switched reluctance generator, so that the switched reluctance generator has obvious advantages and small interference, but the problem of the exhausted electric energy of the storage battery is solved, if a self-excitation mode is adopted, particularly, the excitation storage battery is automatically charged after the output voltage is converted, the switched reluctance generator has a considerable significance, and the advantages of self-excitation and independent excitation are taken into consideration; based on the existence of the storage battery, the double-fed concept and the practical problems from the wind power field are combined, for example, the problem of short-time sudden drop of voltage caused by overlarge load on the output side is solved, if the fault problem cannot be overcome, the system may be broken down, and at the moment, more electric energy needs to be provided, while if the storage battery has electric energy, feedback output is performed if the storage battery is utilized, so that the storage battery has great significance, of course, in order to adapt to good charging and good reverse feedback, the receiving end always has the optimal requirement, that is, the adjustable charging conversion and feedback adjustment tend to further improve the adaptability and controllable flexibility of the whole system.
Disclosure of Invention
According to the background technology, the invention provides a high-efficiency, low-stress and high-reliability switched reluctance generator current conversion system with non-switching natural strong excitation and variable excitation voltage, variable excitation current, variable excitation charging voltage, variable generation voltage, direct high generation voltage output, automatic charging and reverse adjustable energy feedback and a control method thereof, and the system is suitable for the field of variable-speed and constant-speed switched reluctance generator systems under various power driving.
The technical scheme of the invention is as follows:
a variable excitation doubly-fed switched reluctance generator current transformation system is characterized by comprising: a storage battery, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, a ninth switch tube, a tenth switch tube, an eleventh switch tube, a twelfth switch tube, a thirteenth switch tube, a first branch winding of a first phase winding, a second branch winding of the first phase winding, a first branch winding of a second phase winding, a second branch winding of the second phase winding, a first branch winding of a third phase winding, a second branch winding of the third phase winding, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a ninth diode, a twelfth diode, an eleventh diode, a twelfth diode, a thirteenth diode, a fourteenth diode, a fifteenth diode, a sixteenth diode, a seventeenth diode, a ninth diode, a tenth diode, a twelfth diode, a fifteenth diode, a sixteenth diode, the positive pole of the storage battery is connected with the anode of the first switch tube, the anode of the second switch tube, the anode of the third switch tube, one end of the fourth reactor and one end of the fifth reactor, the cathode of the first switch tube is connected with one end of a first branch winding of the first phase winding and the anode of the first diode, and the other end of the first branch winding of the first phase winding is connected with the anode of the second diode, The anode of the third diode, the cathode of the first diode are connected with the cathode of the second diode and one end of the second branch winding of the first phase winding, the cathode of the second switch tube is connected with one end of the first branch winding of the second phase winding and the anode of the fourth diode, the other end of the first branch winding of the second phase winding is connected with the anode of the fifth diode and the anode of the sixth diode, the cathode of the fourth diode is connected with the cathode of the fifth diode and one end of the second branch winding of the second phase winding, the cathode of the third switch tube is connected with one end of the first branch winding of the third phase winding and the anode of the seventh diode, the other end of the first branch winding of the third phase winding is connected with the anode of the eighth diode and the anode of the ninth diode, the cathode of the seventh diode is connected with the cathode of the eighth diode and one end of the second branch winding of the third phase winding, the other end of the second branch winding of the second phase winding, the cathode of a sixth diode, the other end of the second branch winding of the third phase winding, the cathode of a ninth diode, the anode of a fourth switching tube, the cathode of the fourth switching tube are connected with the anode of a fifth switching tube, one end of a first capacitor and one end of a second capacitor, the cathode of the fifth switching tube is connected with the cathode of a storage battery, the cathode of the eleventh diode, the cathode of the twelfth switching tube and the cathode of a thirteenth switching tube, the cathode of the twelfth diode is connected with the other end of the first capacitor, the same-name end of the primary side winding of the first coupling reactor and the same-name end of the primary side winding of the second coupling reactor, the other end of the primary side winding of the first coupling reactor is connected with the anode of the sixth switching tube, the anode of the fourteenth diode, one, the other end of the primary side winding of the second coupling reactor is connected with the anode of the seventh switch tube, one end of the fifth capacitor and one end of the sixth capacitor, the cathode of the sixth switch tube is connected with the cathode of the seventh switch tube, the anode of an eleventh diode, the other end of the second capacitor and the cathode of the fifteenth diode, the cathode of a fourteenth diode is connected with the other end of the fifth capacitor and the anode of the seventeenth diode, the other end of the sixth capacitor is connected with the anode of a fifteenth diode and the cathode of the sixteenth diode, the anode of the sixteenth diode is connected with the other end of the seventh capacitor and the input negative end of the bidirectional direct current isolation transformer, the other end of the eighth capacitor is connected with the cathode of the seventeenth diode, one end of the third capacitor and the anode of the twelfth diode, the cathode of the twelfth diode is connected with the anode of the thirteenth, the other end of the third capacitor is connected with one end of the fourth capacitor and the dotted end of the secondary side winding of the second coupling reactor, the other end of the secondary side winding of the first coupling reactor is connected with the other end of the secondary side winding of the second coupling reactor, the cathode of a thirteenth diode is connected with the other end of the fourth capacitor and the input positive end of a bidirectional direct-current isolation transformer, the output positive end of the bidirectional direct-current isolation transformer is connected with one end of the ninth capacitor, the anode of the eighth switch tube and the anode of the tenth switch tube, the other end of the ninth capacitor is connected with the anode of the thirteenth switch tube, the other end of the fifth reactor and one end of the tenth capacitor, the cathode of the eighth switch tube is connected with the anode of the ninth switch tube and one end of the eleventh capacitor, and the cathode of the tenth switch tube is connected with the anode of the twelfth, One end of the third reactor is connected with the other end of the eleventh capacitor, and the cathode of the eleventh switch tube is connected with the cathode of the ninth switch tube, the other end of the tenth capacitor and the output negative end of the bidirectional direct-current isolation transformer;
the first phase winding first branch winding and the first phase winding second branch winding form a first phase winding, the second phase winding first branch winding and the second phase winding second branch winding form a second phase winding, and the third phase winding first branch winding and the third phase winding second branch winding form a third phase winding; the primary side winding of the first coupling reactor and the secondary side winding of the first coupling reactor form a first coupling reactor, the primary side winding of the second coupling reactor and the secondary side winding of the second coupling reactor form a second coupling reactor, and the first coupling reactor and the second coupling reactor have the same structure and the same transformation ratio; the eighth switch tube, the ninth switch tube, the tenth switch tube, the eleventh switch tube, the twelfth switch tube and the thirteenth switch tube are all full-control power electronic switch devices with anti-parallel diodes.
A control method of a variable-excitation doubly-fed switched reluctance generator variable-current system is characterized in that when a first phase winding needs to be put into operation according to rotor position information in the operation of a switched reluctance generator, a first switch tube is closed, an excitation stage is started, and at the moment, control over a fourth switch tube and a fifth switch tube is divided into three modes, wherein the three modes are respectively as follows: the fourth switching tube and the fifth switching tube are closed simultaneously, the fourth switching tube closes the fifth switching tube and is disconnected, the fourth switching tube opens the fifth switching tube and is closed, and the first-phase winding exciting current in the excitation stage is adjusted by adjusting the ratio of the fourth switching tube to the fifth switching tube in three modes; according to the rotor position information, when the excitation stage is finished, the fourth switching tube and the fifth switching tube are in a disconnected state at the same time, and the power generation stage is started; according to the rotor position information, when the power generation stage is finished, the first switching tube is disconnected, and the first phase winding is finished; according to the rotor position information, when the second phase winding and the third phase winding need to be put into operation, the second switching tube and the third switching tube correspond to the first switching tube, and other devices are shared and have the same working mode as the first phase winding;
during the operation of the switched reluctance generator, the working modes of the sixth switching tube and the seventh switching tube are as follows: the sixth switching tube and the seventh switching tube work according to a PWM mode, the switching frequency of the sixth switching tube and the switching frequency of the seventh switching tube are the same, the duty ratio of the sixth switching tube and the seventh switching tube are the same and larger than 0.5, the phase difference is 180 degrees, and the voltage of the power generation output end, namely the total voltage after the third capacitor, the fourth capacitor, the seventh capacitor and the eighth capacitor are connected in series, is changed by adjusting the duty ratio of the sixth switching tube and the seventh switching tube based on the above constraints;
when the electric quantity of the storage battery is detected to be lower than the lower limit value, the bidirectional direct-current isolation transformer absorbs electric energy from the power generation output end to charge the storage battery in a forward direction, specifically, the eighth switching tube, the ninth switching tube, the tenth switching tube and the eleventh switching tube work according to a PWM mode, the twelfth switching tube and the thirteenth switching tube are in an off state, the tenth switching tube and the eleventh switching tube have the same switching frequency, the same duty ratio and smaller than 0.5, the phase difference is 180 degrees, the eighth switching tube is used as a zero-current soft switching device closing function when the eleventh switching tube is turned off, and the ninth switching tube is used as a zero-current soft switching device closing function when the tenth switching tube is turned off; when the current of the storage battery is detected to be higher than the upper limit value, all switching tubes required for charging are in an off state, and the charging operation is stopped;
when the load of the power generation output end is detected to be overlarge and the voltage suddenly drops and more electric energy needs to be supplemented, and simultaneously the electric energy of the storage battery is higher than the lower limit value, the electric energy of the storage battery feeds back the energy to the power generation output end in a reverse direction, in the period, the tenth switching tube and the eleventh switching tube are in an off state, the eighth switching tube, the ninth switching tube, the twelfth switching tube and the thirteenth switching tube work according to a PMW mode, the switching frequency of the twelfth switching tube and the switching frequency of the thirteenth switching tube are the same, the duty ratio of the twelfth switching tube and the eleventh switching tube are the same and larger than 0.5, the phase difference is 180 degrees, the eighth switching tube is used for closing a zero-current soft switching device when the thirteenth switching tube is turned off, and the ninth switching tube is used for; when the electric quantity of the storage battery is detected to be lower than the lower limit value or the voltage of the power generation output side is recovered and energy feedback is not needed, all switch tubes needed by the energy feedback are in a disconnected state, and the reverse energy feedback work is stopped.
The invention has the following main technical effects:
each phase of winding is divided into two branch windings, a natural parallel excitation strengthening mode and a series power generation output mode are adopted, a switching tube is not needed in the process, and double effects of strengthening excitation and outputting high power generation voltage in the first stage are naturally obtained; in the excitation stage of each phase winding, through the combination of three different modes of the fourth switching tube and the fifth switching tube and the adjustment of the ratio of the three modes, the direct adjustment of the excitation voltage and the excitation current in the continuously and smoothly adjusted phase winding is realized (wherein, the strongest excitation voltage and the strongest excitation current are obtained when the fourth switching tube and the fifth switching tube are both closed in the full excitation period at the same time), the adaptability, the flexibility and the controllability of the power generation system are greatly improved, the comprehensive control of the system is significant, and meanwhile, the adjusted energy storage in the first capacitor and the second capacitor is not wasted and can be output, and the power generation efficiency is also improved; in the power generation stage, the natural series connection of the two branch windings of the phase winding is realized, and the two branch windings are connected with the storage battery in series and then output, namely the power generation voltage is still obviously higher than the input voltage, namely the voltage of the storage battery, and meanwhile, the first capacitor and the second capacitor output redundant electric energy in parallel with the first capacitor and the second capacitor according to the reality, so that the power generation efficiency is high; in addition, when the power generation stage is finished, because the first switching tube is directly turned off (the first phase winding, the second phase winding and the third phase winding turn off the second switching tube) and the winding current is not naturally reduced to zero, the current of the (first) phase winding is forcibly turned off, the current is reduced to zero before the forward torque between the stator and the rotor of the switched reluctance generator, namely the electric working condition, is ensured, and the power generation efficiency is improved.
Under the alternate interleaved switching working mode of the sixth switching tube and the seventh switching tube, firstly, the current pulsation on two sides after the first capacitor and the second capacitor are connected in series is small, so that the excitation and power generation stages are stable; the primary windings of the first coupling reactor and the second coupling reactor are connected in parallel, then the secondary windings of the first coupling reactor and the second coupling reactor are connected in series, high voltage obtained after output is output to the third capacitor and the fourth capacitor and connected in series, and the voltage lifting size can be adjusted by changing the transformation ratio of the first coupling reactor and the second coupling reactor; the two auxiliary passive clamping circuits respectively consisting of the fifth capacitor, the fourteenth diode, the sixth capacitor and the fifteenth diode can release the absorbed sharp edge electric energy, the leakage inductance magnetic energy of the two coupling reactors and the like to the seventh capacitor and the eighth capacitor besides protecting the sixth switching tube and the seventh switching tube, the electric energy utilization rate is high, the power generation efficiency is high, in addition, the sixth switching tube and the seventh switching tube are connected with the third capacitor and the fourth capacitor in series, so that the total output power generation voltage is further improved, meanwhile, continuous different power generation voltage output can be realized by adjusting the duty ratio of the sixth switching tube and the seventh switching tube, so that the output power generation voltage formed by connecting the third capacitor, the fourth capacitor, the seventh capacitor and the eighth capacitor in series can obtain a voltage value which is more than 10 times higher than the voltage of the storage battery relative to the input side, namely the voltage at the two sides of the storage battery, the multi-pole adjustable power generation device has important significance in that the multi-pole adjustable power generation device realizes wide-range power generation voltage change output; in addition, the voltage stress of the individual switching tubes and diodes in the above-described operation is much lower than this for the resulting high generator voltage values.
The charging voltage and the charging current of the storage battery can be adjusted by adjusting the PWM switching duty ratio of the tenth switching tube and the eleventh switching tube so as to meet the optimal charging requirement, and the adaptability is strong; when the storage battery feeds back energy, firstly, a double-fed energy output mode which is jointly realized together with the power generation output of the phase winding of the switched reluctance generator is formed at the moment, and the double-fed energy output mode has great significance and extremely strong adaptability, in addition, the voltage and the current of the reverse feed energy output, namely the power generation output end, can be adjusted by adjusting the PWM switching duty ratio of the twelfth switching tube and the thirteenth switching tube so as to meet the system requirements, and the double-fed energy output mode also has extremely strong adaptability and flexibility, and then the final power generation output voltage can be actively adjusted during the discharging output period of the phase winding, so that an important multivariable basis is provided for the performance improvement and the further development of the system; in addition, the resonance assistance of the eleventh capacitor and the third reactor branch circuit required by the charging and reverse energy feedback of the storage battery and the zero current soft turn-off operation of the eighth switching tube and the ninth switching tube for the rest of the switching tubes are adopted, so that the reliability of the part is improved, and the loss is reduced; finally, the charged and reverse energy feedback operation of the storage battery is carried out only when required in extreme conditions, so that the complexity of the overall system during operation is reduced, and the efficiency is improved.
Drawings
Fig. 1 is a circuit structure diagram of a variable excitation doubly-fed switched reluctance generator current transformation system according to the present invention.
Detailed Description
A current transformation system of a variable excitation doubly-fed switched reluctance generator of this embodiment is shown in fig. 1, and includes a battery X, a first switching tube V1, a second switching tube V2, a third switching tube V3, a fourth switching tube V4, a fifth switching tube V5, a sixth switching tube V6, a seventh switching tube V7, an eighth switching tube V8, a ninth switching tube V9, a tenth switching tube V10, an eleventh switching tube V11, a twelfth switching tube V12, a thirteenth switching tube V13, a first phase winding first branch winding M1, a first phase winding second branch winding M2, a second phase winding first branch winding N1, a second phase winding second branch winding N2, a third phase winding first branch winding P1, a first phase winding second branch winding P2, a first diode D1, a second diode D87458, a third diode D3, a fifth diode 3D 3, a first diode 3, a seventh diode 3, a fifth diode 3, a seventh diode 3, a fifth diode, An eighth diode D8, a ninth diode D9, a twelfth diode D10, an eleventh diode D11, a twelfth diode D12, a thirteenth diode D13, a fourteenth diode D14, a fifteenth diode D15, a sixteenth diode D16, a seventeenth diode D17, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a tenth capacitor C10, an eleventh capacitor C11, a first coupling reactor primary winding L11, a first coupling reactor secondary winding L12, a second coupling reactor primary winding L21, a second coupling reactor secondary winding L22, a third reactor L3, a fourth reactor L4, a fifth reactor L5, a bidirectional isolation transformer X, a first switch V1, and a positive electrode of the first switch V1, The anode of a second switching tube V2, the anode of a third switching tube V3, one end of a fourth reactor L4 and one end of a fifth reactor L5, the cathode of a first switching tube V1 is connected with one end of a first phase winding M1 and the anode of a first diode D1, the other end of the first phase winding M1 is connected with the anode of a second diode D2 and the anode of a third diode D3, the cathode of the first diode D1 is connected with the cathode of a second diode D2 and one end of a first phase winding M2, the cathode of a second switching tube V2 is connected with one end of a second phase winding N1 and the anode of a fourth diode D4, the other end of the second phase winding N1 is connected with the anode of a fifth diode D5 and the anode of a sixth diode D6, the cathode of the fourth diode D4 is connected with the cathode of a fifth diode D695D 5 and one end of a second phase winding N2, the cathode of the third switching tube V3 is connected with the first end 1P 1, The anode of a seventh diode D7, the other end of the first branch winding P1 of the third phase winding is connected with the anode of an eighth diode D8 and the anode of a ninth diode D9, the cathode of a seventh diode D7 is connected with the cathode of an eighth diode D8 and one end of a second branch winding P2 of the third phase winding, the other end of the second branch winding M2 of the first phase winding is connected with the cathode of a third diode D3, the other end of the second branch winding N2 of the second phase winding, the cathode of a sixth diode D6, the other end of the second branch winding P2 of the third phase winding, the cathode of a ninth diode D9, the anode of a fourth switch tube V4 and the anode of a twelfth diode D10, the cathode of a fourth switch tube V4 is connected with the anode of a fifth switch tube V5, one end of a first capacitor C1 and one end of a second capacitor C2, the cathode of the fifth switch tube V5 is connected with the cathode of a storage battery X, the cathode of an eleventh diode D11, the cathode of a twelfth switch tube V12, the cathode of a, The other end of the first coupling reactor primary side winding L11 is connected with the anode of a sixth switching tube V6, the anode of a fourteenth diode D14, one end of a seventh capacitor C7 and one end of an eighth capacitor C8, the other end of the first coupling reactor primary side winding L11 is connected with the anode of a seventh switching tube V6, one end of a fifth capacitor C5 and one end of a sixth capacitor C6, the cathode of the sixth switching tube V6 is connected with the cathode of a seventh switching tube V7, the anode of an eleventh diode D11, the other end of a second capacitor C2 and the cathode of a fifteenth diode D15, the cathode of a fourteenth diode D14 is connected with the other end of a fifth capacitor C5 and the anode of a seventeenth diode D17, the other end of a sixth capacitor C9 is connected with the anode of a fifteenth diode D15, the cathode of a sixteenth diode D16, the anode of a sixteenth diode D8653 is connected with the cathode of a seventh diode C7, The other end of the eighth capacitor C8 is connected with a cathode of a seventeenth diode D17, one end of a third capacitor C3 and an anode of a twelfth diode D12, the cathode of the twelfth diode D12 is connected with an anode of a thirteenth diode D13 and a dotted end of a secondary winding L12 of the first coupling reactor, the other end of the third capacitor C3 is connected with one end of a fourth capacitor C4 and a dotted end of a secondary winding L22 of the second coupling reactor, the other end of a secondary winding L12 of the first coupling reactor is connected with the other end of a secondary winding L22 of the second coupling reactor, the cathode of the thirteenth diode D13 is connected with the other end of the fourth capacitor C4 and an input positive end of the bidirectional DC isolation transformer, the output positive end of the bidirectional DC isolation transformer is connected with one end of a ninth capacitor C9, an anode of an eighth switching tube V8 and an anode of a tenth switching tube V10, the other end of the ninth capacitor C9 is connected with an anode, The other end of a fifth reactor L5 and one end of a tenth capacitor C10, the cathode of an eighth switching tube V8 is connected with the anode of a ninth switching tube V9 and one end of an eleventh capacitor C11, the cathode of a tenth switching tube V10 is connected with the anode of a twelfth switching tube V12, the other end of a fourth reactor L4, the anode of an eleventh switching tube V11 and one end of a third reactor L3, the other end of the third reactor L3 is connected with the other end of an eleventh capacitor C11, and the cathode of the eleventh switching tube V11 is connected with the cathode of a ninth switching tube V9, the other end of a tenth capacitor C10 and the negative output end of the bidirectional direct-current isolation transformer;
the first phase winding M1 and the first phase winding second branch winding M2 form a first phase winding M, the second phase winding first branch winding N1 and the second phase winding second branch winding N2 form a second phase winding N, and the third phase winding first branch winding P1 and the third phase winding second branch winding P2 form a third phase winding P; the first coupling reactor L1 is composed of a first coupling reactor primary side winding L11 and a first coupling reactor secondary side winding L12, the second coupling reactor L2 is composed of a second coupling reactor primary side winding L21 and a second coupling reactor secondary side winding L22, and the first coupling reactor L1 and the second coupling reactor L2 are identical in structure and equal in transformation ratio; the eighth switching tube V8, the ninth switching tube V9, the tenth switching tube V10, the eleventh switching tube V11, the twelfth switching tube V12 and the thirteenth switching tube V13 are all full-control power electronic switching devices with anti-parallel diodes; the first capacitor C1 and the second capacitor C2 are not equal, including the rated voltage and the capacitance are not equal.
In the control method of the variable-excitation doubly-fed switched reluctance generator current conversion system, when the switched reluctance generator operates, according to the rotor position information, when a first phase winding M needs to be put into operation, a first switching tube V1 is closed, an excitation stage is started, and at the moment, the control of a fourth switching tube V4 and a fifth switching tube V5 is divided into three modes, which are respectively: a first mode in which fourth switching tube V4 is closed simultaneously with fifth switching tube V5, a second mode in which fourth switching tube V4 is closed and fifth switching tube V5 is open, and a third mode in which fourth switching tube V4 is open and fifth switching tube V5 is closed, in which first mode battery X directly and solely excites first phase winding M, the excitation voltage to which both legs of first phase winding M are respectively subjected is equal to battery X voltage, in which second mode battery X charges and excites first phase winding M while charging in series via eleventh diode D11 to second capacitor C2, in which third mode battery X charges and excites first phase winding M while charging in series via twelfth diode D10 to first capacitor C1, since C1 is not equal to C2, including rated voltage and capacitance, by adjusting the ratio of the three modes of fourth switching tube V4 and fifth switching tube V5 at this excitation stage, the excitation current of the first phase winding M in the excitation stage can be adjusted, wherein the excitation in the first mode is strongest, and the excitation in the strongest excitation mode is considered because the two branch windings of the first phase winding M are charged and excited in parallel; according to the rotor position information, when the excitation phase is finished, the fourth switching tube V4 and the fifth switching tube V5 are in an open state at the same time, the first switching tube V1 is kept closed, the power generation phase is started, at the moment, the first branch winding M1 and the second branch winding M2 of the first phase winding M are in a series mode and are connected with the storage battery X in series to generate power and output, the generated voltage is obviously greater than the voltage of the storage battery X after the series connection, and if the first capacitor C1 and the second capacitor C2 have enough energy storage in the excitation phase before, the first capacitor C1 and the second capacitor C2 are also connected in series to output, so that the power generation efficiency is high; according to the rotor position information, when the power generation phase is finished, the first switching tube V1 is disconnected, the first phase winding M is forcibly disconnected, and therefore the power generation work can be strictly controlled to be finished;
according to the position information of the rotor, when the second phase winding N and the third phase winding P need to be put into operation, the second switching tube V2 and the third switching tube V3 correspond to the first switching tube V1, the fourth diode D4 and the seventh diode D7 correspond to the first diode D1, the fifth diode D5 and the eighth diode D8 correspond to the second diode D2, the sixth diode D6 and the ninth diode D9 correspond to the third diode D3, the second phase winding first branch winding N1 and the third phase winding first branch winding P1 correspond to the first phase winding first branch winding M1, the second phase winding second branch winding N2 and the third phase winding second branch winding P2 correspond to the first phase winding second branch winding M2, and other common devices are the same as the working mode of the first phase winding M;
in the operation of the switched reluctance generator, the working modes of the sixth switching tube V6 and the seventh switching tube V7 are as follows: the sixth switching tube V6 and the seventh switching tube V7 operate according to the PWM mode, the switching frequency of the sixth switching tube V6 and the switching frequency of the seventh switching tube V7 are the same, the duty ratio is the same and is greater than 0.5, the phase difference is 180 degrees, that is, the staggered switching operation is performed, based on the above constraint, the voltage at the power generation output end, that is, the total voltage after the third capacitor C3, the fourth capacitor C4, the seventh capacitor C7 and the eighth capacitor C8 are connected in series is changed by adjusting the duty ratio of the sixth switching tube V6 and the seventh switching tube V7, specifically, the primary sides of the first coupling reactor L1 and the second coupling reactor L2 are connected in parallel, the secondary sides are connected in series and realize higher voltage output to the third capacitor C3 and the fourth capacitor C4, while the fifth capacitor C5, the fourteenth diode D14, the sixth capacitor C6 and the fifteenth diode D15 are under the action of two clamping circuits, and respectively inhibit the sixth switching tube V6 and the seventh switching tube V7 from absorbing the peak leakage inductance energy, the stored energy is output to a seventh capacitor C7 and an eighth capacitor C8 on the power generation output side at the same time, the generated voltage is further raised, and the voltage which is obviously higher than the voltage of the storage battery X and is obtained by connecting the first capacitor C1 in series with the second capacitor C2 in the previous excitation and power generation stages is combined, so that the generated voltage which is far higher than the voltage of the storage battery X on the input side is obtained on the final power generation output side, and further voltage change can be realized by changing the transformation ratio of the first coupling reactor L1 and the second coupling reactor L2.
When detecting that the electric quantity of the storage battery X is lower than the lower limit value, the bidirectional direct current isolation transformer absorbs the electric energy from the power generation output end to charge the storage battery X in the forward direction for working, specifically, an eighth switch tube V8, a ninth switch tube V9, a tenth switch tube V10 and an eleventh switch tube V11 work according to a PWM mode, a twelfth switch tube V12 and a thirteenth switch tube V13 are in an off state (but diodes connected in parallel reversely participate in the switching work), the tenth switch tube V10 and the eleventh switch tube V11 have the same switching frequency, the same duty ratio and less than 0.5, and a phase difference of 180 degrees, under the constraint condition, the charging voltage and the charging current output to the storage battery X can be adjusted by adjusting the duty ratios of the tenth switch tube V10 and the eleventh switch tube V11, the flexibility and the reliability are good, the eighth switch tube V8 is used as a zero current soft switching device closing function when the eleventh switch tube V11 is turned off, the ninth switch tube V9 is used as a zero current soft switching device closing function when the tenth switch tube V10 is turned off, the eleventh capacitor C11 and the third reactor L3 form a resonance auxiliary branch; when the current of the storage battery X is detected to be higher than the upper limit value, all switching tubes required for charging are in an off state, and the charging operation is stopped;
when the voltage drop caused by the overload or the fault in the grid connection of the power generation output end is detected and more electric energy needs to be supplemented, and the electric energy of the storage battery X is higher than the lower limit value, the electric energy of the storage battery X reversely feeds the power to the power generation output end, in the period, the tenth switching tube V10 and the eleventh switching tube V11 are in an off state, the eighth switching tube V8, the ninth switching tube V9, the twelfth switching tube V12 and the thirteenth switching tube V13 work according to a PMW mode, the twelfth switching tube V12 and the thirteenth switching tube V13 have the same switching frequency, the duty ratio is the same and larger than 0.5, the phase difference is 180 degrees, the voltage output to the power generation output end by the reverse feed energy is adjusted based on the constraint condition, the duty ratio is strong, the eighth switching tube V8 is used as the closing action of a zero current soft switching device when the thirteenth switching tube V13 is turned off, the ninth switching tube V9 is used as a zero-current soft switching device closing action when the twelfth switching tube V12 is turned off, and the eleventh capacitor C11 and the third reactor L3 are used as a resonance auxiliary branch; when the electric quantity of the storage battery X is detected to be lower than the lower limit value or the voltage of the power generation output side is recovered and energy feedback is not needed, all switch tubes needed by the energy feedback are in a disconnected state, and the reverse energy feedback work is stopped.
When the bidirectional isolation direct current transformer works in the forward direction, the bidirectional isolation direct current transformer generally shows a voltage reduction mode so as to meet the requirement that after power generation transformation, a very high power generation voltage is transformed into a flexible and adjustable relatively low storage battery voltage.
Since the branch circuits directly connected with the phase windings have the same structure and the working mode of each phase winding is the same, the switched reluctance generators with any number of phase windings except the switched reluctance generator with three-phase windings according to the embodiment of the present invention should be within the protection scope of the present invention.