CN104716886A - Virtual impedance voltage converter-based control method of virtual synchronous motor - Google Patents

Abstract

The invention discloses a virtual impedance voltage converter-based control method of a virtual synchronous motor. Output voltage and current of a voltage converter is controlled to have the characteristic of a synchronous motor through electric and mechanical main parts of the virtual synchronous motor, wherein the electric part comprises a novel virtual impedance simulation algorithm, a conventional converter current inner ring and a modulation strategy and the mechanical part comprises a power calculating module, a rotor mechanical equation and a virtual damping module. The virtual impedance voltage converter-based control method of the virtual synchronous motor can be used for simulating winding impedance without introducing a differential term of current output by the converter, so that the influence on impedance simulation by an extra low pass filter is overcome, and the current inner ring control of a parallel converter is not sacrificed, and therefore, alternating current is controlled, and the converter has the capacity of preventing current fluctuation, overcurrent and even impact without quick current inner ring control. A silent pole motor and a non-salient pole motor can be simultaneously simulated.

Description

Based on virtual impedance Voltage type converter virtual synchronous motor control method

Technical field:

Patent of the present invention belongs to virtual synchronous Motor Control Field, is specifically related to a kind of based on virtual impedance Voltage type converter virtual synchronous motor control method.

Background technology:

Distributed new generator unit major part access power distribution network, close with load.Along with distributed new access ratio improves, power distribution network is developed to network structure by traditional vertical stratification.The most typical feature of cancellated power distribution network is that generator unit is no longer traditional minority Large Copacity, but most low capacity.Major part distribution generator unit is all grid-connected by electronic power convertor in addition, and therefore its grid-connected characteristic is subject to the control method decision of current transformer.When usual distributed new is grid-connected, current transformer adopts current source control model, and the meritorious and idle alternating current by controlling current transformer namely injecting electrical network realizes.Compared with conventional rotary synchronous generator, grid-connected converter active reactive fast response time, output impedance is little, without the feature of moment of inertia.These make power distribution network face some new problems: one is power distribution network strengthens the reliability of whole network system, stability and safety effects, especially there is standard regulation distributed power source must automatically exit when electric network fault, increased the weight of the unbalanced power of system transient modelling process further; Two is that the intermittent feature of new forms of energy brings serious voltage fluctuation problem to the power distribution network of high impedance, three are distribution power flow by simply unidirectional thicken two-way, have impact on the voltage control of power distribution network, relaying protection, network loss and the quality of power supply.In order to give full play to the advantage of distributed energy, diminuendo distributed power source is on the impact of power distribution network and transmission network, electrical network is allowed to dissolve distributed energy more, distributed power source must participate in frequency modulation and the pressure regulation process of power distribution network and transmission network, the potential assistant service of distributed power source must fully be excavated, and distributed power source must provide necessary assistant service to electrical network.

For the shortcoming of new forms of energy power grid, there is scholar to propose the control thought of virtual synchronous motor, namely by control algolithm, make new forms of energy power supply have the grid-connected characteristic identical with traditional rotary power source, the process of active participate electric power system frequency modulation and voltage modulation, for electrical network provides assistant service.Virtual synchronous motor concept is proposed by J.Driesen scholar the earliest, the units such as Energieonderazok Centrum Nederland (Energy research Centre of Netherlands), TU Delft University of Science and Technology set up VSYNC plan in 2007, research virtual synchronous motor technology, by increasing the virtual inertia of distributed generation unit, reach the object of electric power grid frequency stabilization.After this, Chinese scholars has done a large amount of research work, domestic have the Sheng Wanxing scholar of China Electric Power Research Institute, HeFei University of Technology Zhang Xinghe Soviet Union build emblem scholar, have the Zhong Qingchang scholar, U.S. Hussam Alatrash scholar etc. of German Lao Kesi tal fibre polytechnical university Ralf scholar, Univ Sheffield UK abroad.

According to the common recognition of numerous scholar, grid-connected converter simulation synchronous machine characteristic is the trend that following grid-connected converter controls.Electromagnetism and the mechanical property of simulating synchronous machine are the most general ways simultaneously, and specific implementation can again can by hardware implementing by pure algorithm realization.Wherein electromagnetic property all adopts the mode of impedance simulation, and be all based on model stator winding, comprise voltage-type and current mode scheme, but the shortcoming that each scheme has it intrinsic: all voltage-type impedance simulation modes, because the voltage instruction calculated is all directly control bridge wall voltage by PWM, the current loop control pattern of conventional current transformer has all been sacrificed, alternating current is directly not controlled, this can cause alternating current to occur fluctuation, overcurrent even impacts, especially when also site grid voltage amplitude or phase place are undergone mutation, have a strong impact on the normal operation of current transformer, and current mode impedance simulation mode, owing to copying the impedance operator simulating synchronous motor completely, existing in impedance simulation link significantly delayed, in order to ensure the retardance of overall control within the specific limits, the response speed of current regulator will have been made to require very high.But existing current loop control strategy all cannot reach so high requirement, cause control method retardance comparatively large, Current adjustment is not prompt enough, and control effects is poor.

Summary of the invention:

The present invention is directed to the defect of virtual synchronous motor technology, provide a kind of based on virtual impedance Voltage type converter virtual synchronous motor control method.

For achieving the above object, the present invention adopts following technical scheme:

Based on virtual impedance Voltage type converter virtual synchronous motor control method, it is characterized in that, comprise the following steps:

1) equation of rotor motion of synchronous motor is simulated, according to the active power of output instruction P of Voltage type converter _refwith actual active power of output P _edifference P _err, and the frequency perunit value ω of virtual synchronous motor is calculated with the automatic virtual blocks of proportional component representative ^*, utilize the frequency perunit value ω of synchronous machine ^*calculate the phase theta needed for coordinate transform;

2) synchronous reactance part is simulated, utilize step 1) in the phase theta needed for coordinate transform that obtains, the instruction of current transformer output voltage and actual output voltage are transformed to dq coordinate system respectively, virtual impedance matrix is designed under dq coordinate system, by virtual impedance matrix, computing is carried out to the instruction of current transformer output voltage and actual output voltage, obtain the instruction of current transformer dq axle output current with

3) design current inner ring, utilize step 1) in the phase theta needed for coordinate transform that obtains, output current of converter is transformed to dq coordinate system, for poor with the instruction of current transformer dq axle output current under dq coordinate system, its difference is through PI controller, calculate current transformer dq axle modulation signal, and then obtain the switch controlling signal exporting converter switches network, thus for driving switch network.

The present invention further improves and is, step 1) in, the active power of output instruction P of voltage converter _refwith actual active power of output P _ediffer from, its difference is through the reference capacity P of generating set _basemark the one, the result after mark the one divided by 2 times synchronous machine inertia time constant H and to result integration, obtain the frequency perunit value ω of synchronous machine ^*, concrete formula is as follows:

${\mathrm{\ω}}^{*}=\frac{(P_{\mathrm{ref}}-P_e)}{P_{\mathrm{base}}}\·\frac{1}{2\mathrm{Hs}}---\left(1\right)$

In formula: s is integral operator;

Frequency perunit value ω ^*be multiplied by frequency reference value ω again _rand to result integration, obtain designing the phase theta needed for current transformer Double closed-loop of voltage and current ring, concrete formula is as follows:

$\mathrm{\θ}={\mathrm{\ω}}^{*}\·\frac{{\mathrm{\ω}}_R}{s}---\left(2\right)$

Again to simulate damping effect in actual synchronization rotor rotary course for target, the automatic virtual blocks of design proportion link representative as feedback element, frequency perunit value ω ^*after making difference with reference frequency perunit value 1, link is multiplied and obtains Damping Power therewith, by the power difference P of Damping Power and current transformer _errreal-time poor, for corrected power difference P _err, and then correct the output phase place of this link, obtain the phase theta needed for coordinate transform.

The present invention further improves and is, step 2) in, utilize step 1) middle gained phase theta, dq conversion is carried out to output voltage instruction and the actual three-phase voltage that exports, obtains the virtual excitation electric gesture E of current transformer dq axle respectively _d, E _qwith current transformer dq axle actual output voltage v _d, v _q, respectively by E _dwith v _dmake difference and obtain d shaft voltage error v _{d_err}, E _qwith v _qmake difference and obtain q shaft voltage error v _{q_err}; D shaft voltage error v _{d_err}with q shaft voltage error v _{q_err}through being used for simulate synchronous reactance virtual impedance link after, obtain the instruction of dq axle output current with wherein virtual impedance link only simulates the power frequency characteristic of three-phase symmetrical inductance, is cast out by the differential term of inductive current, and casts out resistive component, obtains the equation of virtual impedance:

$\left[\begin{array}{cc}0& -\frac{1}{w_{R}L}\\ \frac{1}{w_{R}L}& 0\end{array}\right]\left[\begin{array}{c}{u}_{L\_d}\\ u_{L\_q}\end{array}\right]=\left[\begin{array}{c}{i}_{L\_d}\\ i_{L\_q}\end{array}\right]---\left(3\right)$

Wherein, i _{l_d}, u _{l_d}be respectively d shaft current voltage, i _{l_q}, u _{l_q}be respectively q shaft current voltage, w _rfor synchro angle frequency, L is inductance value.

The present invention further improves and is, step 3) in, utilize step 1) middle gained phase place, actual output current is carried out dq conversion, obtains dq axle actual output current i _{c_d}and i _{c_q}, by the instruction of dq axle output current with respectively with dq axle actual output current i _{c_d}and i _{c_q}differ from, its difference obtains current transformer dq axle modulation signal after the computing of PI controller, and modulation signal, again through PWM or SVM modulator, obtains the switch controlling signal exporting converter switches network, thus for driving switch network.

Compared with prior art, the advantage applies that the present invention is based on virtual impedance Voltage type converter virtual synchronous motor control method exists:

It can realize winding reactance simulation without the need to the differential term introducing output current of converter, overcome the impact of extra low pass filter on impedance simulation, and the current inner loop of not sacrificing grid-connected converter controls, make alternating current controlled, resist current fluctuation, the ability that overcurrent even impacts, current inner loop fast is not needed to control yet, conventional current ring is made to may be used in virtual synchronous motor control algorithms and larger retardance problem can not be caused, thus make virtual synchronous motor control algorithms become feasible under existence conditions, and salient pole machine and non salient pole machine can be simulated simultaneously.

Accompanying drawing illustrates:

Fig. 1 is the control block diagram based on virtual impedance Voltage type converter virtual synchronous motor control method;

Fig. 2 is the control block diagram of simulation synchronous motor rotor portion;

Fig. 3 is virtual impedance control block diagram;

Fig. 4 is traditional PI current inner loop control block diagram;

Fig. 5 is synchronous motor when electric network voltage phase suddenlys change and the present invention carries current transformer power output response wave shape under control method;

Fig. 6 is synchronous motor when electric network voltage phase suddenlys change and the present invention puies forward current transformer A phase current waveform under control method;

Fig. 7 is synchronous motor when electric network voltage phase suddenlys change and the present invention carries the frequency change waveform of the current transformer output voltage under control method.

Embodiment:

Below in conjunction with the drawings and specific embodiments, the present invention is described in further details

As shown in Figure 1, the present invention is based on virtual impedance Voltage type converter virtual synchronous motor control method, comprise the following steps:

1) equation of rotor motion of synchronous motor is simulated, according to the active power of output instruction P of Voltage type converter _refwith actual active power of output P _edifference P _errand the frequency perunit value ω of virtual synchronous motor is calculated with the automatic virtual blocks of proportional component representative ^*, utilize the frequency perunit value ω of synchronous machine ^*calculate the phase theta needed for coordinate transform, as shown in Figure 2;

In this step, the active power of output instruction P of voltage converter _refwith actual active power of output P _ediffer from, its difference is through the reference capacity P of generating set _basemark the one, the result after mark the one divided by 2 times synchronous machine inertia time constant H and to result integration, obtain the frequency perunit value ω of synchronous machine ^*, concrete formula is as follows:

${\mathrm{\ω}}^{*}=\frac{(P_{\mathrm{ref}}-P_e)}{P_{\mathrm{base}}}\·\frac{1}{2\mathrm{Hs}}---\left(1\right)$

In formula: s is integral operator;

Frequency perunit value ω ^*be multiplied by frequency reference value ω again _rand to result integration, obtain designing the phase theta needed for current transformer Double closed-loop of voltage and current ring, concrete formula is as follows:

$\mathrm{\θ}={\mathrm{\ω}}^{*}\·\frac{{\mathrm{\ω}}_R}{s}---\left(2\right)$

Again to simulate damping effect in actual synchronization rotor rotary course for target, the automatic virtual blocks of design proportion link representative as feedback element, frequency perunit value ω ^*after making difference with reference frequency perunit value 1, link is multiplied and obtains Damping Power therewith, by the power difference P of Damping Power and current transformer _errreal-time poor, for corrected power difference P _err, and then correct the output phase place of this link.

2) synchronous reactance part is simulated, virtual excitation electric gesture E _dand E _qpoor with current transformer dq axle actual output voltage respectively, through virtual impedance matrix, calculate the instruction of current transformer dq axle output current with as shown in Figure 3;

Wherein, virtual impedance realizes under dq coordinate, there is versatility, the impedance of arbitrary form can be simulated, comprise pure perception, pure capacitive, resistance sense and capacitance-resistance, also comprise the asymmetric inductance of ac-dc axis, and avoid the introducing of current differential item of conventional method and extra use low pass filter;

In this step, utilize step 1) middle gained phase place, dq conversion is carried out to output voltage instruction and the actual three-phase voltage that exports, obtains virtual excitation electric gesture E respectively _d, E _qwith current transformer dq axle actual output voltage v _d, v _q, respectively by E _dwith v _dmake difference and obtain d shaft voltage error v _{d_err}, E _qwith v _qmake difference and obtain q shaft voltage error v _{q_err}; D shaft voltage error v _{d_err}with q shaft voltage error v _{q_err}through being used for simulate synchronous reactance virtual impedance link after, obtain the instruction of dq axle output current with wherein virtual impedance link only simulates the power frequency characteristic of three-phase symmetrical inductance, is cast out by the differential term of inductive current, and casts out resistive component, obtains the equation of virtual impedance:

$\left[\begin{array}{cc}0& -\frac{1}{w_{R}L}\\ \frac{1}{w_{R}L}& 0\end{array}\right]\left[\begin{array}{c}{u}_{L\_d}\\ u_{L\_q}\end{array}\right]=\left[\begin{array}{c}{i}_{L\_d}\\ i_{L\_q}\end{array}\right]---\left(3\right)$

Wherein, i _{l_d}, u _{l_d}for d shaft current voltage, i _{l_q}, u _{l_q}for q shaft current voltage, w _rfor synchronously

Angular frequency, L is inductance value.

3) design current inner ring, the instruction of current transformer dq axle output current with respectively with current transformer dq axle actual output current i _{c_d}and i _{c_q}differ from, its difference, through PI controller, calculates current transformer dq axle modulation signal, and then obtains the switch controlling signal exporting converter switches network, for driving switch network, as shown in Figure 4;

In this step, utilize step 1) middle gained phase place, actual output current is carried out dq conversion, obtains dq axle actual output current i _{c_d}and i _{c_q}, by the instruction of dq axle output current with respectively with dq axle actual output current i _{c_d}and i _{c_q}differ from, its difference obtains current transformer dq axle modulation signal after the computing of PI controller, and modulation signal, again through PWM or SVM modulator, obtains the switch controlling signal exporting converter switches network, for driving switch network.

Embodiment:

When electric network voltage phase suddenlys change, contrast the present invention institute carries virtual impedance simulation algorithm and controls lower current transformer operational effect and operational effect such as synchronous machine such as capacity such as grade.In the 10s moment, electric network voltage phase increases suddenly 15 degree; In the 20s moment, electric network voltage phase declines suddenly 15 degree.As shown in Figure 5, as shown in Figure 6, electric voltage frequency change waveform as shown in Figure 7 for A phase current change waveform for its power response waveform.Can be found by simulation result, when tackling electric network voltage phase sudden change, current transformer power output under algorithm control is put forward by the present invention institute, alternating current and frequency fluctuation will be significantly less than synchronous machine.Demonstrate the present invention put forward the superiority of virtual impedance algorithm.The design parameter of emulation is arranged see table 1 and table 2:

Table 1 grid-connected converter and virtual synchronous Motor control parameters

Table 2 parameter of synchronous machine

Claims (4)

1., based on virtual impedance Voltage type converter virtual synchronous motor control method, it is characterized in that, comprise the following steps:

1) equation of rotor motion of synchronous motor is simulated, according to the active power of output instruction P of Voltage type converter _refwith actual active power of output P _edifference P _err, and the frequency perunit value ω of virtual synchronous motor is calculated with the automatic virtual blocks of proportional component representative ^*, utilize the frequency perunit value ω of synchronous machine ^*calculate the phase theta needed for coordinate transform;

2) synchronous reactance part is simulated, utilize step 1) in the phase theta needed for coordinate transform that obtains, the instruction of current transformer output voltage and actual output voltage are transformed to dq coordinate system respectively, virtual impedance matrix is designed under dq coordinate system, by virtual impedance matrix, computing is carried out to the instruction of current transformer output voltage and actual output voltage, obtain the instruction of current transformer dq axle output current with

3) design current inner ring, utilize step 1) in the phase theta needed for coordinate transform that obtains, output current of converter is transformed to dq coordinate system, for poor with the instruction of current transformer dq axle output current under dq coordinate system, its difference is through PI controller, calculate current transformer dq axle modulation signal, and then obtain the switch controlling signal exporting converter switches network, thus for driving switch network.

2. according to claim 1 based on virtual impedance Voltage type converter virtual synchronous motor control method, it is characterized in that, step 1) in, the active power of output instruction P of voltage converter _refwith actual active power of output P _ediffer from, its difference is through the reference capacity P of generating set _basemark the one, the result after mark the one divided by 2 times synchronous machine inertia time constant H and to result integration, obtain the frequency perunit value ω of synchronous machine ^*, concrete formula is as follows:

${\mathrm{\ω}}^{*}=\frac{(P_{\mathrm{ref}}-P_e)}{P_{\mathrm{base}}}\·\frac{1}{2\mathrm{Hs}}---\left(1\right)$

In formula: s is integral operator;

Frequency perunit value ω ^*be multiplied by frequency reference value ω again _rand to result integration, obtain designing the phase theta needed for current transformer Double closed-loop of voltage and current ring, concrete formula is as follows:

$\mathrm{\θ}={\mathrm{\ω}}^{*}\·\frac{{\mathrm{\ω}}_R}{s}---\left(2\right)$

Again to simulate damping effect in actual synchronization rotor rotary course for target, the automatic virtual blocks of design proportion link representative as feedback element, frequency perunit value ω ^*after making difference with reference frequency perunit value 1, link is multiplied and obtains Damping Power therewith, by the power difference P of Damping Power and current transformer _errreal-time poor, for corrected power difference P _err, and then correct the output phase place of this link, obtain the phase theta needed for coordinate transform.

3. according to claim 1 based on virtual impedance Voltage type converter virtual synchronous motor control method, it is characterized in that, step 2) in, utilize step 1) middle gained phase theta, dq conversion is carried out to output voltage instruction and the actual three-phase voltage that exports, obtains the virtual excitation electric gesture E of current transformer dq axle respectively _d, E _qwith current transformer dq axle actual output voltage v _d, v _q, respectively by E _dwith v _dmake difference and obtain d shaft voltage error v _{d_err}, E _qwith v _qmake difference and obtain q shaft voltage error v _{q_err}; D shaft voltage error v _{d_err}with q shaft voltage error v _{q_err}through being used for simulate synchronous reactance virtual impedance link after, obtain the instruction of dq axle output current with wherein virtual impedance link only simulates the power frequency characteristic of three-phase symmetrical inductance, is cast out by the differential term of inductive current, and casts out resistive component, obtains the equation of virtual impedance:

$\left[\begin{array}{cc}0& -\frac{1}{w_{R}L}\\ \frac{1}{w_{R}L}& 0\end{array}\right]\left[\begin{array}{c}{u}_{L-d}\\ u_{L-q}\end{array}\right]=\left[\begin{array}{c}{i}_{L-d}\\ i_{L-q}\end{array}\right]---\left(3\right)$

Wherein, i _{l_d}, u _{l_d}be respectively d shaft current voltage, i _{l_q}, u _{l_q}be respectively q shaft current voltage, w _rfor synchro angle frequency, L is inductance value.

4. according to claim 1 based on virtual impedance Voltage type converter virtual synchronous motor control method, it is characterized in that, step 3) in, utilize step 1) middle gained phase place, actual output current is carried out dq conversion, obtains dq axle actual output current i _{c_d}and i _{c_q}, by the instruction of dq axle output current with respectively with dq axle actual output current i _{c_d}and i _{c_q}differ from, its difference obtains current transformer dq axle modulation signal after the computing of PI controller, and modulation signal, again through PWM or SVM modulator, obtains the switch controlling signal exporting converter switches network, thus for driving switch network.