永磁同步电机英文

Permanent magnet synchronous motorWorksSynchronous generator in order to achieve the energy conversion, the need for a DC magnetic field. The magnetic field generated direct current, called the generator excitation current. According to the excitation current supply mode, all obtained from other power generator excitation current, known excited generators, excitation power obtained from the generator itself, it is called self excited generator.Work1, the generator excitation current in several ways to obtain1) DC generator excitation modeThis excitation mode of the generator has a dedicated DC generator, this dedicated DC generator called DC exciter, exciter generally coaxial with the generator, the generator field winding mounted on a large shaft through slip rings and fixed brush to get the DC current from the exciter. This excitation mode with the excitation current independent, work is more reliable and reducing electricity consumption from the advantages of the past few decades the main generator excitation mode, with a more mature operating experience. Excitation drawback is slower, maintenance workload, it is more than 10MW units rarely used.2) AC exciter excitation mode power supplySome of the modern large-capacity generator provides AC exciter field current. AC exciter shaft is mounted on the large generator, which outputs the rectified AC power is supplied through the rotor excitation generator, time, the generator excitation mode excitation mode are His, and the use of stationary fairing, so called Reed for his static excitation, AC pilot exciter provides excitation current. AC permanent magnet pilot exciter measuring device can be machine or device with a self-excitation constant voltage alternator. In order to improve the speed excitation regulator, AC exciter usually 100 - 200HZ IF generators, while the AC pilot exciter is used 400 - 500HZ IF generators. The generator field winding and three-phase alternating current windings are wound in the stator slots, the rotor teeth and grooves only without winding, like a gear, so that it is no brushes, slip rings and other rotating parts, with reliable , simple structure and easy manufacturing process. Drawback is noisy, the harmonic components of the AC potential is large.3) No exciter excitation modeIn excitation mode is not set up special exciter and excitation power obtained from the generator itself, and then supplied by the rectifier exciter generator itself, said self-commutated static excitation. Self-commutated static excitation can be divided into self-healing and self-shunt excitation in two ways. It does this by way of self-shunt connected to the outlet of the generator excitation current rectifier transformer to obtain, after rectification supply generator excitation, this excitation mode with a simple knot, less equipment, less investment and less maintenance, etc. Since the complex excitation mode in addition to a rectifier transformer, it also has a series of high-power in the generator stator circuit current transformer. The role of such a transformer in the event of a short circuit to provide a larger excitation current generator to compensate for the lack of the rectifier transformer output. This excitation mode has two excitation power, obtained through the rectifier transformer voltage supply and through a series transformer current source.Relevant characteristics1, the voltage regulationAutomatic adjustment of excitation can be seen as a system to adjust the amount of voltage of the negative feedback control system. Reactive load current is caused by the main generator terminal voltage drops when the excitation current is constant, the generator terminal voltage will vary with the reactive current increases. However, in order to meet user requirements for power quality, the generator terminal voltage should be essentially unchanged, the way to achieve this requirement is to change with the reactive current regulator generator excitation current.2, the regulation of reactive power:Generator running in parallel with the system can be considered as large-capacity power and infinite bus run, to change the generator excitation current, EMF and the stator current also followed changes, then the generator reactive current changes also followed. When the generator with infinite capacity systems operating in parallel, in order to change the reactive power of the generator, the generator excitation current must be adjusted. At this point changing excitation current is not usually called surge, but just changed into the system reactive power.3, reactive load distribution:Parallel operation of generators according to their rated capacity, in proportion to the reactive current assignment. Large capacity generators should pay more reactive load, while the smaller capacity is negative provide less reactive load. To achieve the reactive load can be automatically assigned, by automatically adjusting the excitation means high pressure, changing excitation current to maintain its terminal voltage is constant, but also on the characteristics of the generator voltage regulator to adjust the tilt to achieve the parallel operation of the generator the rational allocation of reactive load.Automatic adjustmentChanging the excitation current of the generator in general, not directly in the rotor circuit for, as the large current circuit is not easy to direct regulation, commonly used method is to change the exciter field current of the generator in order to achieve adjustment rotor current purposes. Commonly used methods to change the exciter field circuit resistance to change additional exciter field current changeSCR conduction angle. Here is mainly about changing the thyristor conduction angle method, which is based on the generator voltage, current or power factor changes, changes accordingly thyristor conduction angle, so the generator excitation current will change accordingly. This device generally consists of transistors, thyristors electronic components, the sensitive, rapid, non-failure zone, output power, small size and light weight advantages. In case of accident can effectively inhibit the generation of over-voltage and fast excitation. Automatic adjustment of excitation devices are usually by the measurement unit, the synchronization unit, an amplifier, difference adjustment unit, stabilization unit, limiting unit, and some auxiliary units. Signal to be measured (such as voltage, current, etc.), the measurement unit transformation compared with the given value, and then compare the results (deviation) after pre-amplification unit and power amplification unit amplified and used to control the thyristor conduction angle, adjust the excitation current in order to achieve the purpose. Synchronization units role is to make part of the output of the phase shift trigger pulse thyristor rectifier with AC excitation power synchronization to ensure correct silicon controlled trigger. Droop units role is to make the parallel operation of the generator can be a stable and reasonable allocation of reactive loads. Stabilization unit is to improve the stability of the power system and the introduction of elements. Excitation system stabilizing unit for improving the stability of the excitation system. Limiting unit is to enable the generator will not over-or under-excitation excitation operation under the conditions and settings. Must be noted that not every kind of automatic adjustment of excitation devices have the various units, a regulator device has the units responsible for specific tasks related to their.Auxiliary equipmentAutomatically adjust the excitation voltage transformer organic component parts, machine-side current transformer, excitation transformer; excitation device will need to provide the following current, Plant AC380v, Plant DC220v control power switch on the power plant with DC220v; need to provide the following empty contacts , automatic boot. automatically shut down. Grid (one normally open, one normally closed) increases or decreases; need to provide the following analog signal generator terminal voltage of 100V, generator terminal current of 5A, bus voltage 100V, excitation device outputs the following relay contact signal; excitation transformer overcurrent, loss of excitation, excitation device abnormalities.Excitation control, protection and signal routing excitation switch back to help the magnetic circuit, fans, excitation switch steal jump, excitation transformer overcurrent regulator failure, abnormal working conditions generator, power transmitter and other components. In the synchronous generator of an internal failure in addition to splitting, it must also de-excitation, the rotor magnetic field weakening as quickly as possible to the minimum extent, but in the case to ensure the rotor, so that excitation shortest possible time, is the main excitation device function. The size of the rated excitation voltage excitation can be divided into linear and nonlinear resistor resistor excitation.Over the past decade, as new technologies, new technology and the emergence of new devices and use, making the generator excitation mode has been continuously developed and refined. In the automatic adjustment of excitation installations, but also continue to develop and promote the use of many new adjustment device. As the use of computer software for computer automatic adjustment of excitation device has significant advantages, many countries are in the development and testing of a computer with a microcomputer with a corresponding number of external devices constitute automatic adjustment excitation device, this device will be able to achieve self-regulation adapt to the best adjustment.The method is called to obtain the excitation current excitation mode. Currently used in the field is divided into two categories: one category is used as a DC generator excitation power of the DC exciter excitation system; another rectifier unit is converted into DC after the AC supply rectifier exciter excitation system. Is as follows:A DC-DC exciter exciter field generally coaxial with the synchronous generator, using shunt or excited connection. Reed uses his connection, the exciter field current by another deputy exciter called coaxial DC generator supply. As shown in Figure 15.5.2 Still the same axis with three rectifier exciter alternator, that is the main generator, AC main exciter exciter and exchange deputy. Vice exciter excitation current starts by the external DC power supply, to be built up and then converted to self-excitation voltage (sometimes using the generator). Vice exciter output current through the static thyristor rectifier rectifier supply main exciter and main exciter AC output current through the stationary phase bridge rectifier silicon rectifier supplies the main generator field winding. (See Figure 15.6)3 stationary rotating rectifier exciter rectifier DC output must brush and collector ring to the rotating field windings transported, for large-capacity synchronous generator, the excitation current of several thousand amperes, so that the collector ring serious overheating. Therefore, in the large-capacity synchronous generator, often using brushes and slip rings without rotating rectifier excitation system, as shown in Figure 15.7. Main exciter armature is rotating three-phase synchronous generator, the AC current flows through the armature rotates together with the spindle rotating silicon rectifier rectifier directly to the main generator rotor field winding. AC main exciter excitation current from the coaxial communication via stationary pilot exciter rectifier thyristor rectifier supply. Because of this excitation system canceled the collector ring and brush gear, also called brushless excitation system.Advantages: Synchronization can be used when the generatorDisadvantages: easily broken brush motor complex structure, high costInsulation resistance tester optical fiber tensile testing machine barrel pump metering pump high and low temperature alloy analyzer Temperature Transmitter Infrared Thermometer Sichuan bulk SMS composite salt spray corrosion test chamber mixer noise meter metallic elemental analyzer pall ring stainless steel instrumentation valves Electromagnetic Flowmeter electric actuator pressure transmitter SwirlmeterControl strategy1 IntroductionIn recent years, with the power electronics technology, microelectronics, new motor control theory and the rapid development of rare earth permanent magnetic materials, permanent magnet synchronous motor speedy popularization and application. With conventional electrically excited synchronous motor compared to the permanent magnet synchronous motor, especially rare earth permanent magnet synchronous motor has less wear and tear, high efficiency, energy-saving effect is obvious advantages. Permanent magnet synchronous motor with permanent magnet excitation provided the motor structure is relatively simple, reducing the machining and assembly costs, and eliminates the need for error-prone collector ring and brush to improve the reliability of motor operation; because without excitation current, no excitation loss, improved motor efficiency and power density, so it is more research in recent years, and is widely applied in various fields as a motor. In energy conservation and environmental protection and more attention today, it is very necessary for their research. Therefore. Here the permanent magnet synchronous motor control strategies are reviewed and introduced permanent magnet synchronous motor control system, the various control strategies development. 12 The mathematical model of permanent magnet synchronous motorsWhen the permanent magnet synchronous motor stator pass into the three-phase alternating current, three-phase current in the stator winding resistance voltage drop. The three-phase alternating current generated by the rotation of the armature magnetomotive force and the magnetic field created by the armature, on the one hand cut the stator windings and the induced electromotive force generated in the stator windings; other electromagnetic force to the rotor to synchronize the rotational speed drag. Armature current will produce only intersects with the stator winding of the stator winding chain leakage flux and the stator leakage induced electromotive force generated in the windings. Furthermore, the rotor magnetic field generated by the permanent magnet synchronous speed to cut the stator windings. Resulting in no-load electromotive force. To facilitate analysis, mathematical models, assume the following parameters: ignore the motor core saturation; the motor without hysteresis loss and eddy current; the stator and the rotor magnetomotive force along the magnetic field generated by the inner circle of the stator sinusoidal , ignoring all the space harmonics magnetic field; symmetrical windings of each phase, i.e. the number of turns of each phase winding resistance of the same, with the axis of the mutual displacement of the same electrical angle.The analysis of the mathematics of the synchronous motor, often using two-phase synchronous rotating (d, q) coordinate system and the two-phase stationary (, ) coordinate system. Figure 1 shows the permanent magnet synchronous motor (d, q) rotating coordinate system mathematical model.(1) The stator voltage equation is:Where: r is the stator winding resistance; p is the differential operator, p = d / dt; id, iq for the stator current; ud, uq is the stator voltage; d, q respectively, flux in d, q-axis component of ; f is the rotor angular velocity ( = fnp); np for the motor pole pairs.(2) the stator flux equation:Where: f is the rotor flux.(3) electromagnetic torque is:Where: J is the moment of inertia of the motor.If the motor is a salient pole motor, then Ld = Lq, select id, iq and the motor mechanical angular velocity is the state variable, which can have the status of permanent magnet synchronous motor equation:By the formula (7) shows that the three-phase permanent magnet synchronous motor is a multi-variable system, and id, iq, nonlinear coupling exists between the relationship, in order to achieve high-performance three-phase permanent magnet synchronous motor control, is a challenging task.Three permanent magnet synchronous motor control strategiesAny electromagnetic torque motors are the main magnetic field and the magnetic field generated by the interaction of the armature. DC motor armature main magnetic field and the magnetic field in the spatial difference between each 90 , it can be adjusted independently; AC motor armature main magnetic field and the magnetic field is not perpendicular to each other, influence each other. Thus, a long time, the AC motor torque control performance is poor. After a long study, the current AC motor control with constant frequency ratio control, vector control, direct torque control scheme.3.1 Constant ratio controlConstant ratio control is an open loop control. It is based on a given system, using space vector pulse width modulation conversion uout the desired output voltage is controlled to operate the motor at a certain speed. Dynamic performance requirements in some places, because the open-loop VVVF control is simple, is still widely used for general speed control system, but because of the steady-state model based on the motor, you can not get a good dynamic control performance, Therefore, the motor must be based on a dynamic mathematical model. Permanent magnet synchronous motor is nonlinear dynamic mathematical model, multi-variable, which contains with id or iq product terms, so to get an accurate dynamic control performance, must be and id, iq decoupling. In recent years, research various nonlinear controller is used to solve the nonlinear characteristics of permanent magnet