CN105958525B - PWM grid-connected inverter control method of permanent magnet wind power generation system - Google Patents

PWM grid-connected inverter control method of permanent magnet wind power generation system Download PDF

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CN105958525B
CN105958525B CN201510947257.2A CN201510947257A CN105958525B CN 105958525 B CN105958525 B CN 105958525B CN 201510947257 A CN201510947257 A CN 201510947257A CN 105958525 B CN105958525 B CN 105958525B
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current
grid
inverter
phase
axis
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CN105958525A (en
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王红玲
郭利辉
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Xuchang University
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Xuchang University
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • H02J3/382Dispersed generators the generators exploiting renewable energy
    • H02J3/386Wind energy
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/70Wind energy
    • Y02E10/76Power conversion electric or electronic aspects

Abstract

The invention discloses a PWM grid-connected inverter control method of a permanent magnet wind power generation system, which comprises the following steps: obtaining a current sampling value and a filter capacitor current value in a grid-connected current fundamental wave period T; subtracting the current sampling value from a current feedback value; multiplying the adjustment signal by a synchronous signal to obtain a grid-connected inverter network side current instruction signal; subtracting the filter capacitor current sampling value from the filter capacitor current feedback value; carrying out proportional resonance adjustment to obtain a filter capacitor current instruction signal; adjusting the grid-connected inverter grid-side current and a current instruction signal, adding the adjusted current and the current instruction signal to a filter capacitor current instruction signal, and multiplying by a proportionality coefficient to obtain a total control quantity; and generating an inverter pulse width modulation signal PWM according to the total control quantity. The invention can realize active and reactive decoupling control and improve the stability and the high efficiency of the whole system.

Description

PWM grid-connected inverter control method of permanent magnet wind power generation system
Technical Field
The invention relates to the field of power technology control, in particular to a PWM grid-connected inverter control method of a permanent magnet wind power generation system.
Background
The grid-connected power generation system of photovoltaic, wind power and the like mainly comprises a photovoltaic array, a fan, a grid-connected inverter and the like, and a storage battery is also arranged in the schedulable system to serve as energy storage equipment. The grid-connected power generation system is connected to a public power grid through an inverter with proper matching capacity, under the condition that sunlight is sufficient in the daytime, a local load is provided, the surplus energy can be provided for the public power grid, and under the condition of night or cloudy day, the local load directly obtains required electric energy from the power grid.
An inverter combining a PWM control technology is called a PWM inverter, the PWM inverter is researched and researched for more than 30 years, great progress is made, and a main circuit of the PWM inverter is developed from an early semi-controlled device bridge circuit to a present full-controlled device bridge circuit; the topological structure of the circuit is developed from a single-phase circuit and a three-phase circuit to a multi-phase combination and multi-level topological circuit; the PWM switch control is developed to soft switch modulation from pure hardware switch modulation, the power level is also developed to megawatt level from kilowatt level, along with the development of PWM inverter technology, a plurality of PWM inverters have been designed, and the following types are specifically provided:
classifying according to the phase number of the power grid: single-phase circuits, three-phase circuits, multi-phase circuits;
classification by PWM on-off modulation: hard switching modulation and soft switching modulation;
classified according to bridge structure: half-bridge configuration, full-bridge configuration;
sorting by modulation level: a two-level, three-level circuit, a multi-level circuit;
the PWM inverter is further classified into a voltage-type PWM inverter and a current-type PWM inverter according to the difference between the dc energy storage elements. The voltage-type and current-type PWM inverters have respective characteristics in aspects of a main circuit structure, PWM signal generation, a control strategy and the like, and circuit duality exists between the voltage-type and current-type PWM inverters. Other distribution methods can be classified as either current-mode or voltage-mode PWM inverters with respect to the main circuit topology.
The grid-connected inverter is an important part of a grid-connected system and is divided into a voltage source type and a current source type. The voltage source type PWM grid-connected inverter is mature in technology, and is widely applied to grid-connected power generation due to good bidirectional grid-connected inversion capability. However, the voltage on the dc side of the voltage grid-connected inverter must be higher than the peak value of the grid voltage and keep constant, so a step-up chopper is added in the middle, which will increase the system cost and reduce the system efficiency. The three-phase current type PWM grid-connected inverter does not need a booster circuit, and the grid-connected problem of low direct-current side voltage can be solved by directly utilizing the characteristics of the current type PWM grid-connected inverter, so that the system efficiency is improved, and the cost is saved.
The control strategy of the current-mode PWM inverter comprises the following steps:
1) indirect current control
The basic idea of indirect current control is to indirectly control the output inductor current by controlling the amplitude and phase of the fundamental wave of the input voltage of the inverter, so that the phase current output at the ac side and the phase voltage at the ac side are kept in the same phase, which is also called amplitude phase control.
The indirect current control has the advantages of simple control structure, no need of a current sensor, good switching characteristic and static characteristic, and is convenient for microcomputer realization. And the defects are that the dynamic response is slow, the system parameter change is sensitive, and direct current offset exists in the dynamic process.
The indirect current control of the current-mode PWM inverter means that the grid-side current of the current-mode PWM inverter is indirectly controlled by controlling the amplitude and the phase of the alternating-current side capacitor voltage or the alternating-current output current of the inverter. The fundamental component of alternating current output current of the current type PWM inverter is linear amplification of an SPWM modulation signal, the phase and amplitude of the output current of the inverter can be adjusted by controlling the modulation signal by applying an SPWM technology, and then indirect current control of the inverter can be realized by filtering action of an AC side LC filter, so that a network side unit power factor is achieved. Of course, in order to stabilize the input direct current, the indirect current control also needs to introduce current closed-loop feedback.
2) Direct current control
The direct current control is a current transient tracking control method, and is characterized by that it utilizes operation to obtain current instruction signal of AC side, then introduces current feedback of AC side and directly controls the current of AC side to make it track the instruction current value. The control mode has a double-loop control structure of a current inner loop and a voltage outer loop; in the current inner loop, the reactive power can be controlled by controlling the power factor angle. In the voltage outer loop, the control of the direct current is realized by adjusting the reference amplitude of the alternating current. Whether the outer loop voltage is stable or not depends on whether the inner loop current can quickly and accurately track the current set. The control mode can effectively track the change of load voltage, has the advantages of good dynamic performance, easy current limiting, high current control precision and the like, is widely concerned, and researches various control schemes in sequence, mainly comprises modes of PID control, predictive current control, sliding mode variable structure control, pole allocation, quadratic optimal control, nonlinear state feedback control, fuzzy control and the like. However, the common characteristics of the sensors are that decoupling of control variables is needed, the calculated amount is large, the realization is difficult, two current sensors are needed for detecting state variables, and an alternating current electromotive force sensor and a capacitance voltage sensor are needed for some sensors, so that the cost is high.
Modulation mode of current-mode PWM inverter
1) SPWM technique
The SPWM technology compares a sine wave modulation signal with a triangular carrier signal with fixed frequency, uses an intersection point as a switching point to obtain a series of high-frequency pulse sequences with equal amplitude and unequal widths, and can accurately reproduce modulation wave information after power amplification of an inverter.
The SPWM modulation technology of the current-type inverter is based on the traditional two-logic bipolar SPWM modulation technology, a certain matrix operation is carried out to convert the SPWM modulation technology into a three-logic PWM waveform, the three-logic signal also fully reflects the information of a modulation wave, and the three-logic signal is decoupled under the conditions of high frequency and low frequency, and can be used for controlling the on-off of a main circuit switch, so that the aim of controlling the current on an alternating current side is fulfilled.
With the development of an intelligent high-speed micro control chip, the shortening of an instruction cycle, the enhancement of a computing function and the increase of storage capacity, the digital SPWM has wider application prospect. Therefore, in recent years, voltage vector pulse width modulation technology has been rapidly developed and widely applied to many aspects of electric transmission.
1. The voltage space vector PWM method is firstly applied to an AC variable frequency speed regulating system, and compared with the AC variable frequency speed regulating system adopting a conventional SPWM mode, the AC variable frequency speed regulating system adopting the SVPWM mode has the advantages that the torque ripple of a motor is reduced, and the utilization rate of DC voltage fed to an inverter is improved; meanwhile, the stator phase current is closer to a sine wave, the harmonic wave is less, and the dynamic performance of the alternating current variable frequency speed regulating system adopting the SVPWM mode is very excellent.
2. At present, the voltage space vector PWM method is widely applied to an active filter, a three-phase converter is controlled as a whole, and the interaction between phases of a PWM main circuit is well coordinated. The control strategy can effectively track the command current, restrain the load harmonic wave, obviously reduce the total current distortion rate of the current at the power supply side, and is an effective current tracking control scheme.
3. The voltage space vector PWM method is applied to a rectification control system, the system has good dynamic performance, the digitization is easy to realize, high power factor can be realized, and energy can flow in two directions. The most outstanding advantage is that the direct current utilization rate is improved by about 15.47% compared with the conventional SPWM control method, and the switching loss is reduced to different degrees by different modulation methods. Based on the above advantages, the space vector PWM method is more and more widely applied to the rectification control system.
The three-phase grid-connected inverter is generally realized by a three-phase full-bridge circuit, each of three bridge arms is formed by connecting 2 power devices in series, the middle connection part is used as a three-phase voltage output end, and the real-time control of three-phase output voltage or three-phase output current is realized by controlling the on-off time of 6 power devices. Currently, the SVPWM method is widely used, and the method needs to complete 2 switching operations (defining that a power device is switched from on to off or from off to on and is switched from 1 switching operation) for each power device in each switching period, and a power device will cause a certain power loss without one switching operation. When the switching frequency is low, the switching loss of the power device can be ignored, but the low switching frequency can cause that the output waveform of the three-phase voltage or current contains more harmonic content, the sine degree of the waveform is influenced, and meanwhile, the burden and the cost of the filter current are increased.
In order to pursue two smaller output voltages and output currents of harmonic waves, the switching frequency generally needs to be increased, but obviously, larger switching loss of a power device is brought, and the conversion efficiency of the three-phase grid-connected inverter is reduced. In order to further increase the switching frequency and reduce the switching loss, discontinuous modulation technology is adopted in the prior art to reduce the switching loss on the three-phase multi-level inverter. In another scheme, discontinuous modulation is applied to the active filter to achieve a better control effect. Still another solution proposes a unified discontinuous modulation technique applied to a three-phase two-level inverter. The scheme is realized by injecting different zero sequence components on the basis of basic sine wave reference voltage, and the inactive interval of each bridge arm switch in one fundamental wave period is 120 degrees.
Disclosure of Invention
The invention provides a PWM grid-connected inverter control method of a permanent magnet wind power generation system based on one or more problems, which is used for solving the problem that active power and reactive power output by a grid-side inverter in the prior art cannot be decoupled.
The PWM grid-connected inverter control method of the permanent magnet wind power generation system comprises the following steps:
sampling grid-connected current and filter capacitor current with a sampling period of L1 to obtain M1 current sampling values I in a grid-connected current fundamental wave period TnetmAnd M2 filter capacitor current values inetmWherein, M1 is M2 is T/L1, M is 0, 1, 2 …, M1-1, and the current sampling value Inet0Corresponding to 0 phase point of grid-connected current fundamental wave, and filter capacitor current sampling value inet0Corresponding to a 0 phase point of a grid-connected filter capacitor current fundamental wave;
sampling the M1 current samples InetmSubtracting the current feedback value to obtain a first error value;
the M2 filter capacitance current values inetmSubtracting the current feedback value of the filter capacitor to obtain a second error value; adjusting the first error value, and multiplying the adjusted first error value by a synchronous signal to obtain a grid-connected inverter grid-side current instruction signal;
carrying out proportional resonance adjustment on the second error value to obtain a filter capacitor current instruction signal;
adjusting the grid-connected inverter grid side current and the current instruction signal, adding the adjusted current instruction signal and a filter capacitor current instruction signal, and multiplying by a proportionality coefficient to obtain a total control quantity;
and generating an inverter pulse width modulation signal PWM with the duty ratio M3 changed along with the synthesized total control quantity according to the total control quantity.
Further, a permanent magnet synchronous generator system includes: the circuit comprises a main circuit, a driving circuit, a control circuit and an auxiliary circuit.
Furthermore, the main circuit comprises a rectifying circuit, a capacitor filter circuit and an IPM inverter circuit.
Further, the grid-connected inverter grid-side current and the grid-connected inverter grid-side current command signal are regulated by a current outer loop PI regulator;
the proportional coefficient of the PI regulator is as follows:
the lead time coefficient of the PI regulator is as follows:
wherein: r is current outer ring resistance, C is current outer ring capacitance, and L is current outer ring inductance.
Further, the method further comprises:
acquisition of three-phase voltage signal U of power gridga、Ugb、UgcAnd the three-phase current signal i on the AC side of the invertera、ib、ic
The three-phase voltage signal U of the power grid is converted into a three-phase voltage signalga、Ugb、UgcObtaining a power grid voltage signal U under a two-phase synchronous rotating coordinate system through coordinate transformationgdAnd UgqThe three-phase current signal i on the AC side of the inverter is useda、ib、icObtaining an alternating current side current signal i under a two-phase synchronous rotating coordinate system through coordinate transformationdAnd iq
According to a mathematical model of the inverter under a three-phase static coordinate system, when three-phase inductance on the alternating current side of the inverter is unbalanced, establishing the mathematical model of the inverter under a two-phase synchronous rotating coordinate system;
according to the mathematical model under the two-phase synchronous rotating coordinate system, establishing a d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system;
and carrying out decoupling control on the three-phase PWM grid-connected inverter according to the current loop controller under the condition of unbalanced inductance.
Further, the coordinate transformation adopts one of Clarke transformation, Park transformation or Park inverse transformation.
Further, the mathematical model of the inverter in the three-phase stationary coordinate system is as follows:
wherein L isa、Lb、LcFor three-phase inductance, R, on the AC side of the invertera、Rb、RcIs a three-phase resistance u in the linega、ugb、ugcFor three-phase voltage of the grid ua、ub、ucIs a three-phase voltage u on the AC side of the inverterONThe potential difference is between the neutral point on the ac side of the inverter and the negative pole on the dc side.
Further, a mathematical model of the inverter under a two-phase synchronous rotating coordinate system is as follows:
wherein: lambda [ alpha ]qdAnd λdqRespectively a d-axis voltage coupling coefficient and a q-axis voltage coupling coefficient under a two-phase synchronous rotating coordinate system, ZdAnd ZqThe inductance impedance of d-axis and q-axis under a two-phase synchronous rotating coordinate system, ZqdAnd ZdqRespectively representing the coupling impedance of the q axis to the d axis and the coupling impedance of the d axis to the q axis under the two-phase synchronous rotating coordinate system; u. ofdAnd uqThe components of the d axis and the q axis of the voltage signal at the alternating current side of the inverter under a two-phase synchronous rotating coordinate system are respectively.
Further, the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system has the input of an alternating-current side two-phase current signal and a power grid voltage signal and the output of an inverter alternating-current side voltage given value u under the two-phase synchronous rotating coordinate systemd_refAnd uq_ref
Further, the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system is as follows:
wherein id_refAnd iq_refRespectively setting values of d-axis and q-axis components of alternating current side current of the inverter, kiIs an integral coefficient, kpIs a proportionality coefficient, RmAnd the average value of the three-phase resistance of the inverter is obtained.
According to the PWM grid-connected inverter control method of the permanent magnet wind power generation system, provided by the invention, by collecting a plurality of sampling values of grid-connected current and filter capacitor current in a period T and carrying out inner ring and outer ring regulation on the plurality of sampling values, harmonic waves in output current of the grid-side inverter can be effectively reduced, output waveform distortion is reduced, active and reactive decoupling control is realized, and the stability and the efficiency of the whole system are improved.
Drawings
Fig. 1 is a flowchart of a PWM grid-connected inverter control method of a permanent magnet wind power generation system according to a first embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a permanent magnet wind power generation system according to a second embodiment of the present invention;
FIG. 3 is a schematic diagram of a driving circuit according to a second embodiment of the present invention;
fig. 4 is a schematic structural diagram of a sampling circuit according to a second embodiment of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples. It should be noted that, if not conflicting, the embodiments of the present invention and the features of the embodiments may be combined with each other within the scope of protection of the present invention.
Example one
The embodiment of the invention provides a PWM grid-connected inverter control method of a permanent magnet wind power generation system, and the permanent magnet synchronous generator system comprises: the circuit comprises a main circuit, a driving circuit, a control circuit and an auxiliary circuit. The main circuit comprises a rectifying circuit, a capacitor filter circuit and an IPM inverter circuit.
As shown in fig. 1, the method includes:
101. sampling grid-connected current and filter capacitor current with a sampling period of L1 to obtain M1 current sampling values I in a grid-connected current fundamental wave period TnetmAnd M2 filter capacitor current values inetm. Wherein, M1 is M2 is T/L1, M is 0, 1, 2 …, M1-1, and the current sampling value Inet0Corresponding to 0 phase point of grid-connected current fundamental wave, and filter capacitor current sampling value inet0And corresponding to the 0 phase point of the grid-connected filter capacitor current fundamental wave.
102. Sampling the M1 current samples InetmSubtracting the current feedback value to obtain a first error value;
103. the M2 filter capacitance current values inetmSubtracting the current feedback value of the filter capacitor to obtain a second error
A value;
104. adjusting the first error value, and multiplying the adjusted first error value by a synchronous signal to obtain a grid-connected inverter grid-side current instruction signal;
105. carrying out proportional resonance adjustment on the second error value to obtain a filter capacitor current instruction signal;
106. the grid-connected inverter grid side current is added with the filter capacitor current instruction signal after being regulated by the current instruction signal, and then the sum is multiplied by a proportionality coefficient to obtain the total control quantity
Specifically, the grid-connected inverter grid-side current and the grid-connected inverter grid-side current command signal are regulated by a current outer loop PI regulator;
the proportional coefficient of the PI regulator is as follows:
the lead time coefficient of the PI regulator is as follows:
wherein: r is current outer ring resistance, C is current outer ring capacitance, and L is current outer ring inductance.
107. And generating an inverter pulse width modulation signal PWM with the duty ratio M changing along with the synthesized total control quantity according to the total control quantity.
Wherein, the duty ratio M is:
M=K×(Iref-IL)
wherein K is a proportionality coefficient, ILIs a steady-state value of the inductor current on the DC side, IrefThe current value is given to the dc side.
According to the PWM grid-connected inverter control method of the permanent magnet wind power generation system, provided by the invention, by collecting a plurality of sampling values of grid-connected current and filter capacitor current in a period T and carrying out inner ring and outer ring regulation on the plurality of sampling values, harmonic waves in output current of the grid-side inverter can be effectively reduced, output waveform distortion is reduced, active and reactive decoupling control is realized, and the stability and the efficiency of the whole system are improved.
Example two
The embodiment of the invention provides a PWM grid-connected inverter control method of a permanent magnet wind power generation system. The permanent magnet wind power generation system is shown in fig. 2 and comprises a main circuit, a driving circuit, a control circuit and an auxiliary circuit. The main circuit comprises a three-phase rectifier circuit, an intelligent power module IPM inverter circuit, a permanent magnet synchronous motor and the like; the drive circuit drives the IPM power inverter after the 6 paths of PWM signals generated by the DSP are subjected to optical coupling isolation; the TMS320F2812DSP control chip is used as a core of the control circuit and is used for completing realization of controller algorithms of a speed loop and a current loop of the permanent magnet synchronous motor, generation of space vector PWM waves and the like; the auxiliary circuit comprises a Hall sensor, a current detection circuit, a fault detection protection circuit and the like, and realizes the detection of the rotating speed and the position of the motor, the current detection, the system protection and the like.
The drive circuit is used for amplifying the PWM pulse output by the DSP to be enough to drive the power switch tube, and the drive circuit mainly plays a role in switching power amplification in principle, but the importance of the drive circuit is that the switching characteristic of the power switch tube is closely related to the performance of the drive circuit, and the drive circuit with excellent design can improve the switching characteristic of the power switch tube, so that the switching loss is reduced, and the efficiency of the whole system and the working reliability of a power device are improved. Therefore, the quality of the driving circuit directly affects the performance of the converter. The power switch device selected in this embodiment uses IPM (6MBP20RH060), the PWM pulse high and low levels sent by the DSP are 0V and 3V, respectively, and the driving signal high and low levels required by the IPM are 0V and 15V, respectively, and when the pulse input pin of the 6MBP20RH060 is low, the IGBT is turned on, and when it is high, the IGBT is turned off.
The driving circuit structure of this embodiment is shown in FIG. 3, in which PWM is DSPThe pulse, fault, is the signal sent by the protection circuit. The NAND gate adopts SN74F00D of TI company, the high-speed optical coupler adopts HCPL4504, here, the optical coupler and the NAND gate are combined to realize the amplification and the negation of pulse signals, and effectively realize the electric isolation of weak current and a main circuit. When the IPM works normally, fault is at high level. When PWM is high level, the optical coupler outputs VinAt low level, the internal IGBT is turned on, and conversely, when the PWM pulse is at low level, VinAt a high level of 15V, the internal IGBT is turned off. Fault signal is low level when IPM is in fault, resulting in VinThe output high level turns off the internal IGBT. And the function of externally locking the PWM pulse is realized. In addition, when the internal IGBT needs to be turned off, a low level can be added to the fault pin to block the PWM pulse.
The control circuit comprises a sampling circuit, a Clark conversion circuit, a Park conversion circuit, a PI regulator control circuit and a PWM pulse generation circuit.
Common current sampling methods include a sampling resistance method, a current transformer method, a hall sensor method, and the like. The Hall sensor has the advantages of high precision, good linearity, wide frequency band, quick response and the like, but is expensive and high in cost; the sampling resistance method has the problems of electric isolation, the need of an external optical isolator or a magnetic isolator and large power loss. In view of the fact that the three-phase grid-connected current is power frequency alternating current which is approximate to a sine wave, the sampling requirement can be met by adopting the current transformer, and therefore the grid-connected current and the filter capacitor current are sampled by the current transformer method. The current transformer has the functions of realizing the electrical isolation of the main circuit and the control circuit on one hand and realizing the conversion and sampling of the stator current on the other hand. The output of the current transformer is a bipolar alternating current signal obtained by scaling down the stator current, and an A/D conversion module of the DSP can only acquire a unipolar voltage signal between 0 and 3V, so that a sampling circuit is required to modulate the output signal of the current transformer to a range which can be acquired by the DSP.
The structure of the sampling circuit of this embodiment is shown in fig. 4. In FIG. 4, the operational amplifier is TL082 from TI company and is powered by a +/-15V power supply; t is the current mutual inductance TA 14W-200. Output i of T1The alternating current signal is obtained by reducing the current on the network side according to the conversion rate; a voltage follower, a resistor R1And R2Is connected in parallel as a sampling resistor, i1Converted into a voltage signal u1Outputting; the second stage operational amplifier will u1The amplitude value of the phase-locked loop is zoomed to +/-1.5V, and the phase position is kept unchanged; finally, -15V DC power supply and resistor R4Form a boost circuit, will u11.5V is increased to obtain a unipolar voltage signal u with the amplitude of 0-3V0
It is worth noting that in the design of the current sampling circuit, for the use of the current transformer, a proper sampling resistor must be selected to obtain a high sampling precision, two anti-parallel diodes at the output end of the sampling circuit form a limiting circuit, and the output voltage is clamped between 0 and 3V to avoid damaging the DSP.
The embodiment of the invention provides a PWM grid-connected inverter control method of a permanent magnet wind power generation system. The method further comprises the following steps on the basis of the embodiment:
107. acquisition of three-phase voltage signal U of power gridga、Ugb、UgcAnd the three-phase current signal i on the AC side of the invertera、ib、ic
108. The three-phase voltage signal U of the power grid is converted into a three-phase voltage signalga、Ugb、UgcObtaining a power grid voltage signal U under a two-phase synchronous rotating coordinate system through coordinate transformationgdAnd UgqThe three-phase current signal i on the AC side of the inverter is useda、ib、icObtaining an alternating current side current signal i under a two-phase synchronous rotating coordinate system through coordinate transformationdAnd iq
In this embodiment, the coordinate transformation is one of Clarke transformation, Park transformation, or Park inverse transformation.
109. According to a mathematical model of the inverter under a three-phase static coordinate system, when three-phase inductance on the alternating current side of the inverter is unbalanced, establishing the mathematical model of the inverter under a two-phase synchronous rotating coordinate system;
in this embodiment, a mathematical model of the inverter in a three-phase stationary coordinate system is as follows:
wherein L isa、Lb、LcFor three-phase inductance, R, on the AC side of the invertera、Rb、RcIs a three-phase resistance u in the linega、ugb、ugcFor three-phase voltage of the grid ua、ub、ucIs a three-phase voltage u on the AC side of the inverterONThe potential difference is between the neutral point on the ac side of the inverter and the negative pole on the dc side.
The mathematical model of the inverter under the two-phase synchronous rotating coordinate system is as follows:
wherein: lambda [ alpha ]qdAnd λdqRespectively a d-axis voltage coupling coefficient and a q-axis voltage coupling coefficient under a two-phase synchronous rotating coordinate system, ZdAnd ZqThe inductance impedance of d-axis and q-axis under a two-phase synchronous rotating coordinate system, ZqdAnd ZdqRespectively representing the coupling impedance of the q axis to the d axis and the coupling impedance of the d axis to the q axis under the two-phase synchronous rotating coordinate system; u. ofdAnd uqThe components of the d axis and the q axis of the voltage signal at the alternating current side of the inverter under a two-phase synchronous rotating coordinate system are respectively.
110. According to the mathematical model under the two-phase synchronous rotating coordinate system, establishing a d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system;
in this embodiment, the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system inputs two-phase current signals and grid voltage signals at the ac side, and outputs a given voltage value u at the ac side of the inverter in the two-phase synchronous rotating coordinate systemd_refAnd uq_ref
Preferably, the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system is:
wherein id_refAnd iq_refRespectively setting values of d-axis and q-axis components of alternating current side current of the inverter, kiIs an integral coefficient, kpIs a proportionality coefficient, RmAnd the average value of the three-phase resistance of the inverter is obtained.
111. And carrying out decoupling control on the three-phase PWM grid-connected inverter according to the current loop controller under the condition of unbalanced inductance.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (10)

1. A PWM grid-connected inverter control method of a permanent magnet wind power generation system is characterized by comprising the following steps:
sampling grid-connected current and filter capacitor current in a sampling period L1 to obtain M1 current sampling values I in a grid-connected current fundamental wave period TnetmAnd M2 filter capacitor current values inetmWherein M1 ═ M2 ═ T-
L1, M0, 1, 2 …, M1-1, current sample value Inet0Corresponding to 0 phase point of grid-connected current fundamental wave, and filter capacitor current value inet0Corresponding to a 0 phase point of a grid-connected filter capacitor current fundamental wave;
sampling the M1 current samples InetmSubtracting the current feedback value to obtain a first error value;
the M2 filter capacitance current values inetmSubtracting the current feedback value of the filter capacitor to obtain a second error value; adjusting the first error value, and multiplying the adjusted first error value by a synchronous signal to obtain a grid-connected inverter grid-side current instruction signal;
carrying out proportional resonance adjustment on the second error value to obtain a filter capacitor current instruction signal;
adjusting the grid-connected inverter grid-side current and the grid-connected inverter grid-side current instruction signal, adding the adjusted grid-connected inverter grid-side current instruction signal and the adjusted grid-connected inverter grid-side current instruction signal to a filter capacitor current instruction signal, and multiplying the sum by a proportionality coefficient to obtain a total control quantity;
and generating an inverter pulse width modulation signal PWM with the duty ratio M3 changed along with the synthesized total control quantity according to the total control quantity.
2. The PWM grid-connected inverter control method of a permanent magnet wind power generation system according to claim 1, wherein the permanent magnet synchronous generator system comprises: the circuit comprises a main circuit, a driving circuit, a control circuit and an auxiliary circuit.
3. The PWM grid-connected inverter control method of the permanent magnet wind power generation system according to claim 2, wherein the main circuit includes a rectifier circuit, a capacitor filter circuit and an IPM inverter circuit.
4. The PWM grid-connected inverter control method of the permanent magnet wind power generation system according to claim 1, wherein the grid-connected inverter grid-side current and the grid-connected inverter grid-side current command signal are adjusted by a current outer loop PI regulator;
the proportional coefficient of the PI regulator is as follows:
the lead time coefficient of the PI regulator is as follows:
wherein: r is current outer ring resistance, C is current outer ring capacitance, and L is current outer ring inductance.
5. The PWM grid-connected inverter control method of a permanent magnet wind power generation system according to claim 1, further comprising:
acquisition of three-phase voltage signal U of power gridga、Ugb、UgcAnd the three-phase current signal i on the AC side of the invertera、ib、ic
The three-phase voltage signal U of the power grid is converted into a three-phase voltage signalga、Ugb、UgcObtaining a power grid voltage signal U under a two-phase synchronous rotating coordinate system through coordinate transformationgdAnd UgqThe three-phase current signal i on the AC side of the inverter is useda、ib、icObtaining an alternating current side current signal i under a two-phase synchronous rotating coordinate system through coordinate transformationdAnd iq
According to a mathematical model of the inverter under a three-phase static coordinate system, when three-phase inductance on the alternating current side of the inverter is unbalanced, establishing the mathematical model of the inverter under a two-phase synchronous rotating coordinate system;
according to the mathematical model under the two-phase synchronous rotating coordinate system, establishing a d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system;
and carrying out decoupling control on the three-phase PWM grid-connected inverter according to the current loop controller under the condition of unbalanced inductance.
6. The PWM grid-connected inverter control method of the permanent magnet wind power generation system according to claim 5, wherein the coordinate transformation is one of Clarke transformation, Park transformation or Park inverse transformation.
7. The PWM grid-connected inverter control method for the permanent magnet wind power generation system according to claim 5, wherein a mathematical model of the inverter under a three-phase static coordinate system is as follows:
wherein L isa、Lb、LcFor inverter acLateral three-phase inductance, Ra、Rb、RcIs a three-phase resistance u in the linega、ugb、ugcFor three-phase voltage of the grid ua、ub、ucIs a three-phase voltage u on the AC side of the inverterONThe potential difference is between the neutral point on the ac side of the inverter and the negative pole on the dc side.
8. The PWM grid-connected inverter control method of the permanent magnet wind power generation system according to claim 5, wherein a mathematical model of the inverter under a two-phase synchronous rotation coordinate system is as follows:
wherein: lambda [ alpha ]qdAnd λdqRespectively a d-axis voltage coupling coefficient and a q-axis voltage coupling coefficient under a two-phase synchronous rotating coordinate system, ZdAnd ZqThe inductance impedance of d-axis and q-axis under a two-phase synchronous rotating coordinate system, ZqdAnd ZdqRespectively representing the coupling impedance of the q axis to the d axis and the coupling impedance of the d axis to the q axis under the two-phase synchronous rotating coordinate system; u. ofdAnd uqThe components of the d axis and the q axis of the voltage signal at the alternating current side of the inverter under a two-phase synchronous rotating coordinate system are respectively.
9. The PWM grid-connected inverter control method for the permanent magnet wind power generation system according to claim 8, wherein the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system has an input of an alternating-current side two-phase current signal and a grid voltage signal and an output of an inverter alternating-current side voltage given value u under the two-phase synchronous rotating coordinate systemd_refAnd uq_ref
10. The PWM grid-connected inverter control method of the permanent magnet wind power generation system according to claim 9, wherein the d-axis and q-axis effectively decoupled current loop controller of the two-phase synchronous rotating coordinate system is:
wherein id_refAnd iq_refRespectively setting values of d-axis and q-axis components of alternating current side current of the inverter, kiIs an integral coefficient, kpIs a proportionality coefficient, RmAnd the average value of the three-phase resistance of the inverter is obtained.
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