In view of the characteristics of bidirectional flow of energy in the AC excitation device, a solution of AC-DC plus dual control is adopted, and the system is composed of a novel motor-controlled MCU.
Turn-off word asynchronous generator shifting Hengpo AC excitation energy two-way flow dual system, single-chip microcomputer control picture classification number document identification code article number one s a wind generator for grid-connected power generation, the wind turbine output frequency and grid The frequency is the same.
There are two types of methods for keeping the frequency of the wind turbine constant. 1 Keep the speed of the wind turbine constant, so that the constant frequency power is obtained, that is, the constant speed constant frequency. At present, most wind power generation systems adopt this method. The generator speed changes with the wind speed, that is, the variable speed constant frequency.
Since wind energy is proportional to the power of the speed, allowing the speed to change within a certain range can make more efficient use of wind energy, and the efficiency is more significant. Therefore, the research and development of the variable frequency constant frequency wind turbine excitation control system is more and more Pay attention to it.
Variable-speed constant-frequency wind power generation system currently mainly has AC-DC system AC excitation generator system brushless doubly-fed generator system Switched reluctance motor system Magnetic field modulation generator system Synchronous asynchronous variable-speed constant-frequency generator system and electromagnetic slip connection system .
This paper studies the AC excitation generator system.
It uses a power electronic device to feed the rotor with a nine-person frequency and a corresponding amplitude current to make the output voltage constant frequency constant amplitude.
Because AC excitation generator system has the characteristics of energy bidirectional flow, in the past, the crossover converter was mostly used, but its output current harmonic component is high and the output frequency is limited.
At present, some people adopt matrix converters, although their performance is excellent, they have great potential, and the advantages of intersection and intersection are all in one, but the principle is still immature and still in the research and experimental stage.
This article is a period of Huang Mingchuan male, master student of Hefei University of Technology.
Journal of Hefei University of Technology, Natural Science Edition, Volume I, the first phase of the controllable symmetric AC-DC converter.
Compared with the traditional AC-DC converter, it not only maintains the advantage that the output current is completely close to the sine wave, but also achieves the input current closure of the unit power factor.
The most important thing is that the two-way controllable AC-DC converter is controlled by a control system composed of a new type of single-chip microcomputer, which solves the problem that the traditional AC-DC converter cannot perform two-way flow of energy, and realizes two kinds of sub-synchronous speed and super-synchronous speed. Variable speed constant frequency and constant voltage in the state.
The principle of variable speed constant frequency This paper studies a system consisting of a three-phase wound asynchronous motor and a two-way AC-DC inverter power source excited to the rotor.
The principle is shown in the figure.
In the asynchronous generator, the relationship between the rotational speeds is the rotational speed of the stator's rotating magnetic potential in the Renren/Several type, that is, the synchronous rotational speed of the rotor rotating rotor with respect to the rotational speed of the rotor, when the direction is the same, No. When the direction is opposite, take the No. 1 grid frequency, that is, the output frequency motor pole logarithm rotor current frequency slip rate. It can be known from the formula that when the rotor speed changes, the bidirectional AC-DC inverter power supply supplies the rotor frequency to the human current. The fluctuations compensated by changing the rotor current frequency and making changes eventually remain unchanged.
The corresponding basic equations can be listed as a sub-graph.
The eight-worker corpse spoon one door r Shengyi, J diagram basic principle block diagram circle equivalent circuit diagram one 犷 one blade several blade type respectively for the power supply voltage rotor feed respectively stator potential rotor potential respectively for the stator current rotor current phase Huang Mingchuan, the research of variable-speed constant-frequency AC excitation wind turbine system is that the stator winding resistance and reactance are respectively the rotor winding resistance and the reactance, respectively, and the excitation loop resistance and reactance are respectively the current ratio coefficient and the voltage ratio coefficient. The equation can be derived from the phasor diagram of the doubly-fed generator as shown.
Through analysis, it can be seen that the rotor of the figure can be operated in both super-synchronous speed and sub-synchronous speed. At this time, the generator can output power to the outside, and the electromagnetic power is a few com, mechanical power corpse, a corpse, poor power corpse, Yin Dang When the rotor is in the sub-synchronous speed, the corpse rotor enters the power from the variable frequency power supply. When the rotor is in the super synchronous speed, the corpse and the rotor output power to the variable frequency power supply.
In either case, the input mechanical power always overcomes the electromagnetic torque to do work while delivering power to the stator.
Figure two-stage generator phase, figure microcomputer control system The doubly-fed wind turbine system is mainly composed of three-phase wound asynchronous generator, AC-DC variable-frequency excitation power supply and excitation transformer.
The rotation speed detecting element is a photoelectric encoder.
The main circuit of the excitation power supply is a two-way AC-straight type, and the rectification and inverter parts are power components composed of a three-phase bridge circuit.
Compared with the way of intersection, it has obvious advantages. Firstly, the cost is reduced. The inverter bridge with at least 18 power devices is required, and the crossover is only 12, and the output current waveform is almost completely close to the sine wave. The waveform distortion is large, the intermediate DC link has large inertia, and the output is affected by the input. In addition, the rectification end of the AC-DC variable-frequency excitation power supply also adopts M control, that is, the whole system is dual M control, which not only realizes the energy bidirectional flow, but also greatly The power factor of the rectification is increased and the input current waveform is improved.
Dual system has appeared in the field of AC drive at home and abroad, but it is limited by the number of high-speed output ports of the microprocessor. It is generally a double-structure or single-additional waveform generating circuit structure. The system is more complicated, the cost is increased, and the testability is also reduced.
The new motor-controlled single-chip microcomputer introduced by the company just solved the problem of dual-system. In addition to retaining and improving the traditional port as an event processor, it also added a component waveform generator that can directly output three-phase waves. The control circuit is composed of a single-chip microcomputer with peripheral circuits. The waveform generator directly outputs complementary signals to control the inverter. The event processor also controls the rectification part through the software high-speed output complementary signal, which satisfactorily solves the dual M control. problem.
The driving circuit of the power device is composed of a dedicated integrated driving circuit, and the protection function is provided with a rotor overcurrent output overvoltage overvoltage and undervoltage, and a low rotation speed.
The frequency conversion method adopts the currently widely used operation according to the speed value detected by the encoder in real time, and the three-phase pulse of the frequency one is generated by the single chip microcomputer to drive the inverter circuit.
Since the mathematical model of the asynchronous motor is a strong combination of high-order multivariable equations, it is very difficult to control with the traditional double closed loop. The research shows that the vector control is very suitable for the variable speed constant frequency generator.
In this paper, the vector control of the rotor field orientation is used, which just happens to achieve the purpose of solving the problem of speed and output frequency.
The control software mainly consists of the main program waveform generation subroutine service subroutine software timing subroutine and a series of function subroutines. The waveform generation subroutine is responsible for the inverter end control, the service subroutine is responsible for the rectification end control, and the software timing subroutine is used for The vector control algorithm of the inverter and the rectifier end determines the energy flow direction by the subroutine to judge whether the converter is inverting or rectifying at both ends.
Journal of Hefei University of Technology, Natural Science Edition, Volume I, Phase I, Inverter Driven Rectifier Drive 8. [Simplified Control Circuit Loop Conclusions Due to the maturity of frequency conversion technology and the development of microcomputer technology, variable speed constant frequency doubly-fed generators can fully realize power frequency. Constant frequency power supply to the grid is a promising wind power system.
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