CN102842921B - Micro-grid multi-inverter parallel voltage control method for droop control of robust power - Google Patents

Abstract

The invention discloses a micro-grid multi-inverter parallel voltage control method for droop control of robust power. The method comprises the following steps of: specific to each inverter in a micro-grid, computing and synthesizing an inverter output reference voltage by adopting a robust power droop controller; and introducing virtual complex impedance containing a resistance component and an inductive impedance component, and keeping inverter output impedance in a pure resistance state under a power frequency condition by adopting a multi-loop voltage control method based on virtual impedance and quasi-resonance PR (Proportional-Resonant) control, thereby realizing micro-grid multi-inverter parallel running and power equation, wherein the robustness of a micro-grid parallel system on numeric value computing errors, parameter drift, noise interference and the like is enhanced. Due to the adoption of the method, the defects of larger loop current of a parallel system, non-uniform power distribution and the like caused by the inductivity of the impedance output by inverters in the conventional droop method are overcome; and the method is suitable for multi-grid parallel uniform current control in a low-voltage micro-grid.

Description

The micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control

Technical field

The present invention relates to micro-capacitance sensor multi-inverter control field, the micro-capacitance sensor multi-inverter parallel voltage control method of particularly a kind of robust power droop control.

Background technology

In order to preferably excavate the potentiality of distributed power generation, the adverse effect that distributed power generation is brought to bulk power grid is solved, the focus of current power system research is turned into using the form Tissue distribution formula plant-grid connection of micro-capacitance sensor.In recent years, with the operation of many experimental nature micro-capacitance sensors, achieved certain achievement in terms of microgrid energy management system and power electronics Interface Controller, but under physical condition Small And Medium Capacity distributed power source a large amount of presence so that low-voltage micro-capacitance sensor is increasingly becoming study hotspot.

One key issue of low-voltage micro-capacitance sensor operation is the parallel running of multi-inverter.The control strategy of single inverter determines its output impedance characteristic, and output impedance characteristic is different, and the droop control method of use is also just differed.At present, the voltage control mode that shunt chopper is used typically uses PI control modes.Inverter output impedance under such a control mode is general in inductive, thus droop control method is just using traditional droop control mode based on emotional resistance.But, inverter output resistance and line resistance be can not ignore in most cases in low-voltage micro-capacitance sensor, particularly with low-voltage circuit, its line resistance is much larger than circuit induction reactance, thus traditional droop control method based on perceptual output impedance is applied to low-voltage micro-capacitance sensor, may result in situations such as power-sharing precision is not high, circulation is larger.

The content of the invention

The technical problems to be solved by the invention are, it is not enough for prior art, a kind of micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control is provided, when solution existing method is applied to multi-inverter parallel sharing control in low-voltage micro-capacitance sensor, the problem of power-sharing precision is not high, circulation is larger.

In order to solve the above technical problems, the technical solution adopted in the present invention is：A kind of micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control, including micro-capacitance sensor multi-inverter parallel system, the micro-capacitance sensor multi-inverter parallel system include several inverters in parallel, and the inverter accesses power network；The inverter includes dc source, inverter circuit, LC filter circuits, A/D sample circuits, phase-locked loop circuit, controller, Drive Protecting Circuit, touch-screen; the dc source, inverter circuit, LC filter circuits are sequentially connected, and the LC filter circuits access micro-capacitance sensor；The A/D sample circuits input is connected with the LC filter circuits；The controller is connected with the Drive Protecting Circuit input, A/D sample circuits output end, touch-screen, phase-locked loop circuit output end；The phase-locked loop circuit input is connected with micro-capacitance sensor；The step of Drive Protecting Circuit drives the inverter circuit, this method is as follows：

1）In the starting point in each sampling period, controller is by A/D sample circuits to inverter output filter capacitor voltage u_oWith filter capacitor electric current i_c, line current i_oSampled respectively, sampled data is given controller and handled；

2）By inverter output LC filtering circuit capacitor voltages u_oAfter 90 ° of phase shift, with line current i_oMultiplication obtains q, inverter output LC filtering circuit capacitor voltages u_oWith line current i_oMultiplication obtains reactive power average value Q in p, power frequency period and active power mean value P computing formula is as follows：

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.,$

Wherein, k is sampling sequence number in power frequency period, and N is the sampling number in power frequency period；

3）LC filtering circuit capacitor voltages u is calculated using discrete Fourier transform_oIn the virtual value U of a cycle_o, output voltage amplitude reference value E^*Subtract U_o, obtained difference is multiplied by COEFFICIENT K_e, then P and sagging coefficient n product are subtracted, obtained difference passes through integral operation, obtains the virtual value E of reference voltage, and its time-domain expression is：

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s},$

Wherein, K_IFor integral coefficient, s is complex frequency；

4）Angular frequency reference value ω^*Plus Q and the product of sagging Coefficient m, the integrated computing of both sums obtains referring to angular frequency, and its time-domain expression is：

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s};$

5）By the virtual value E of reference voltage and with reference to angular frequency and phase-locked loop circuit output synchronous phase angle

Synthesized reference voltage u^* _ref, its computing formula is：

Wherein, phase angle

For presynchronization signal；

6）Virtual resistance component and virtual inductor component are introduced, by reference voltage u^* _refSubtract line current i_oWith the product of virtual impedance, LC filtering circuit capacitor voltage reference values u is obtained_ref, its computing formula is：

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-k_L{L}_s\frac{s}{s+{\mathrm{\ω}}_c})i_o$

Wherein, ω_cFor the cut-off frequency of low pass filter, R_DFor virtual resistance value, L_sFor LC filter circuit inductance values, k_LFor virtual inductor coefficient；

7）By u_refAnd u_oAs the input of quasi-resonance PR controllers, the reference value i of LC filtering circuit capacitor electric currents is obtained_ref；

8）Introduce LC filtering circuit capacitor electric voltage feed forward links k_Uu_o, obtain reference current

9）

With LC filtering circuit capacitor current feedback signals k_ci_cProportion adjustment is carried out, SPWM modulation wave signals D is obtained；

10）SPWM modulating waves and triangular carrier carry out bipolar modulation, the duty cycle signals of switching tube are drawn, through Drive Protecting Circuit, controlling switch pipe S₁~S₄Open and turn off.

Compared with prior art, the advantageous effect of present invention is that：Invention introduces the virtual complex impedance containing virtual resistance component and virtual induction reactance component, virtual resistance increase inverter output resistance can further suppress internal circulation, improve power-sharing effect；Virtual induction reactance reduces inverter output induction reactance, the output impedance of shunt chopper is designed as into resistive under the conditions of power frequency, it is ensured that the uniformity of inverter output impedance and line impedance, but do not produce corresponding power attenuation.Robust power droop control device is introduced in low-voltage micro-capacitance sensor, power-sharing precision when further increasing different capabilities distributed power source parallel running, and logarithm value calculation error, parameter drift, noise jamming etc. have stronger robustness.

Brief description of the drawings

Fig. 1 is one embodiment of the invention micro-capacitance sensor multi-inverter parallel system structure diagram；

Fig. 2 is the micro-capacitance sensor multi-inverter parallel voltage control method schematic diagram of one embodiment of the invention robust power droop control；

Fig. 3 is one embodiment of the invention robust power droop control device structural representation；

Fig. 4 is many loop voltag control block diagrams of the one embodiment of the invention based on virtual complex impedance technology；

Fig. 5 is two inverter parallel simulation waveforms of the one embodiment of the invention using the micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control.

Embodiment

As shown in figure 1, one embodiment of the invention micro-capacitance sensor multi-inverter parallel system includes several inverters in parallel, the inverter accesses power network；The inverter includes dc source, inverter circuit, LC filter circuits, A/D sample circuits, phase-locked loop circuit, dsp controller, Drive Protecting Circuit, touch-screen; the dc source, inverter circuit, LC filter circuits are sequentially connected, and the LC filter circuits access micro-capacitance sensor；The A/D sample circuits input is connected with the LC filter circuits；The dsp controller is connected with the Drive Protecting Circuit input, A/D sample circuits output end, touch-screen, phase-locked loop circuit output end；The phase-locked loop circuit input is connected with micro-capacitance sensor；The Drive Protecting Circuit drives the inverter circuit.Inverter circuit is IGBT switching tubes S₁~S₄The single-phase inversion circuit of composition.Inductance L and electric capacity C composition inverter output filter circuits, for filtering the high-frequency harmonic of inverter ac side generation.U_dcDC voltage, u are exported for distributed power source_invFor inverter output voltage, i_oFor line current, i_LFor inductive current, i_cFor capacitance current, u_oFor output filter capacitor voltage,

For presynchronization signal.Multiple inverters are connected on ac bus points of common connection PCC by connection line, and are supplied to micro-capacitance sensor to load the energy for being distributed the source that declines.Dc source is connected with inverter circuit, and inverter circuit is connected with output filter circuit, and dsp controller is connected with A/D sample circuits, phase-locked loop pll circuit, Drive Protecting Circuit, touch-screen respectively, the switching tube connection of Drive Protecting Circuit and inverter circuit.Switching tube S in the output control inverter circuit of Drive Protecting Circuit₁~S₄Break-make.Inverter output filter capacitor voltage u_o, line current i_o, capacitance current i_cAfter A/D sample circuits, feeding dsp controller carries out calculation process.

The micro-capacitance sensor multi-inverter parallel voltage control method of the robust power droop control of the present invention is as follows：

1）In the starting point in each sampling period, dsp controller is by A/D sample circuits, to inverter output filter capacitor voltage u_oWith filter capacitor electric current i_c, line current i_oSampled respectively, sampled data is given dsp controller and handled；

2）Inverter output filter capacitor voltage u_o, line current i_o, idler angular frequency reference value ω^*, idle voltage output amplitude reference value E^*As the input of robust power droop control device, calculated by robust power droop control method and draw reference voltage u^* _ref, implement process as follows：

（1）By inverter output filter capacitor voltage u_oAfter 90 ° of phase shift, with line current i_oMultiplication obtains q, inverter output filter capacitor voltage u_oWith line current i_oThe reactive power average value Q and active power mean value P that multiplication is obtained in p, power frequency period ask for calculating by average value and obtained；

（2）Inverter output voltage u is calculated using discrete Fourier transform DFT_oIn the virtual value U of a cycle_o, output voltage amplitude reference value E^*Subtract U_o, obtained difference is multiplied by COEFFICIENT K_e, then P and sagging coefficient n product are subtracted, obtained difference passes through integral operation, obtains reference voltage virtual value E；

（3）Angular frequency reference value ω^*Plus Q and the product of sagging Coefficient m, the integrated computing of both sums obtains referring to angular frequency；

（4）By the virtual value E of reference voltage and with reference to angular frequency and phaselocked loop output synchronous phase angleSynthesized reference voltage u^* _ref.Phase angle

For presynchronization signal, kept when accessing micro-capacitance sensor and common point voltage in phase, access micro-capacitance sensor backed off after random.

3）Reference voltage u^* _ref, inverter output filter capacitor voltage u_o, line current i_o, filter capacitor electric current i_cAs the input of polycyclic voltage controller, SPWM modulating wave D are calculated by many loop voltag control algolithms, it is concretely comprised the following steps：

（1）Reference voltage u^* _refSubtract line current i_oThe product of virtual impedance is multiplied by, the Voltage Reference u of polycyclic voltage controller is obtained_ref；

（2）u_refAnd u_oAs the input of quasi-resonance PR controllers, it exports the reference value i for obtaining capacitance current_ref；

（3）Introduce electric voltage feed forward link k_Uu_o, obtain reference current

（4）

With capacitor current feedback signal k_ci_cProportion adjustment is carried out, SPWM modulation wave signals D is obtained.

4）SPWM modulating waves and triangular carrier carry out bipolar modulation, the duty cycle signals of switching tube are drawn, through Drive Protecting Circuit, controlling switch pipe S₁~S₄Open and turn off.

Fig. 2 is a kind of micro-capacitance sensor multi-inverter parallel voltage control method structured flowchart for the robust power droop control invented.Inverter output filter capacitor voltage u_o, line current i_o, idler angular frequency reference value ω^*, idle voltage output amplitude reference value E^*As the input of robust power droop control device, calculated by robust power droop control method and draw reference voltage u^* _ref.Reference voltage u^* _ref, inverter output voltage u_o, line current i_o, filter capacitor electric current i_cAs the input of polycyclic voltage controller, SPWM modulating waves D is calculated by many loop voltag control algolithms based on virtual complex impedance technology and quasi-resonance PR controls.SPWM modulating waves and triangular carrier carry out bipolar modulation, draw the duty cycle signals of switching tube, through Drive Protecting Circuit, control IGBT switching tubes S₁~S₄Open and turn off so that shunt chopper output AC voltage.

Fig. 3 is robust power droop control device structural representation.For low-voltage micro-capacitance sensor circuit, its line resistance is much larger than circuit induction reactance, now, if being resistive by the output impedance control of inverter, inverter output impedance and line impedance sum are still resistive, now, using traditional droop control method, then droop control equation is：

$\left\{\begin{array}{c}\mathrm{\ω}={\mathrm{\ω}}^{*}+\mathrm{mQ}\\ E=E^{*}-\mathrm{nP}\end{array}\right.---\left(1\right)$

Wherein, m, n are sagging coefficient, ω^*For idler angular frequency reference value, E^*For idle voltage output amplitude reference value.The active power of output of shunt chopper and the expression formula of reactive power are

$\left\{\begin{array}{c}P=2(U_o{U}_{\mathrm{pcc}}\cos \mathrm{\θ}-U_{\mathrm{pcc}}^2)/R_o\\ Q=-2U_o{U}_{\mathrm{pcc}}\sin \mathrm{\θ}/R_o\end{array}\right.---\left(2\right)$

Wherein, U_o、U_pccThe respectively virtual value of the virtual value of inverter output filter capacitor voltage and bus points of common connection voltage, θ is the phase difference of inverter output voltage and points of common connection voltage, R_oFor substitutional connection resistance.

During application conventional power droop control method, when the inverter parallel of multiple identical capacity, if the parameter of each inverter is identical and connection line electric parameter difference is smaller, preferable inverter parallel can be obtained and flow effect.But in the case where each inverter rated capacity is different or connection line parameter differences are larger, it can make occur the problems such as system circulation is larger, inverter power distributes uneven during micro-capacitance sensor parallel running using conventional power droop control method.

Robust power droop control method can effectively solve the above problems.As shown in figure 3, by inverter output filter capacitor voltage effective value U_o, with E^*Difference be multiplied by COEFFICIENT K_e, obtained value substituted（1）In E^*.By introducing integral element 1/s in conventional power droop control, and then realize that active power is distributed by precise proportions so that active power output is not influenceed by equivalent output impedance, similarly, integrator is constructed to Reactive Power Control link, can also realize that reactive power is distributed by precise proportions.The more traditional droop control method of robust power droop control method can effectively weaken the influence to system such as error in numerical calculation, parameter drift, noise jamming so that system has stronger robustness for the presence of these extraneous factors.Meanwhile, robust droop control method can also effectively weaken influence of the load change to micro-capacitance sensor voltage.

Robust power droop control device to implement process as follows：

1）By inverter output filter capacitor voltage u_oAfter 90 ° of phase shift, with line current i_oMultiplication obtains q, filter capacitor voltage u_oWith line current i_oThe reactive power average value Q and active power mean value P that multiplication is obtained in p, power frequency period ask for formula by average value and are calculated as：

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.---\left(3\right)$

Wherein, k is sampling sequence number in power frequency period, and N is the sampling number in power frequency period.

2）Inverter output filter capacitor voltage u is calculated using discrete Fourier transform DFT_oIn the virtual value U of a cycle_o, output voltage amplitude reference value E^*Subtract U_o, obtained difference is multiplied by COEFFICIENT K_e, then P and sagging coefficient n product are subtracted, obtained difference passes through integral operation, obtains the virtual value E of reference voltage, and its time-domain expression is：

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s}---\left(4\right)$

Wherein, m, n are sagging coefficient, ω^*For idler angular frequency reference value, E^*For idle voltage output amplitude reference value.It is pointed out that under limit, the input quantity of integrator should be 0, that is, have：

nP=K_e(E^*-U_o)                                （5）

For all shunt choppers, as parameter K_eWhen value is identical, formula（5）Amount on the right side of middle equal sign is also identical.I.e. under limit, the nP values of whole system are constant.

3）Angular frequency reference value ω^*Plus Q and the product of sagging Coefficient m, the integrated computing of both sums obtains referring to angular frequency, expression formula is

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s}---\left(6\right)$

4）By the virtual value E of reference voltage and with reference to angular frequency and phaselocked loop output synchronous phase angleSynthesized reference voltage u^* _ref.Its computing formula is：

Wherein, phase angleFor presynchronization signal, kept when accessing micro-capacitance sensor and common point voltage in phase, access micro-capacitance sensor backed off after random.

Fig. 4 show many loop voltag control block diagrams based on virtual complex impedance and quasi-resonance PR controls.It is polycyclic voltage-controlled to be mainly characterized by：The virtual complex impedance containing resistive component and induction reactance component is introduced, and make it that inverter output impedance is in purely resistive under power frequency by multiple feedback loop method.Labor is as follows：

The relation shown in Fig. 1, it is assumed that filter inductance value is L_s, the equivalent resistance of filter inductance is R_L, inverter output voltage is u_inv, the electric current for flowing through filter inductance is i_L, can be obtained by circuit：

$L\frac{{\mathrm{di}}_L}{\mathrm{dt}}=u_{\mathrm{inv}}-u_o-R_L{i}_L---\left(8\right)$

$C\frac{{\mathrm{du}}_o}{\mathrm{dt}}=i_c=i_L-i_o---\left(9\right)$

More than simultaneous two formula, is obtained：

$\mathrm{LC}\frac{d^2{u}_o}{\mathrm{dt}}+R_{L}C\frac{{\mathrm{du}}_o}{\mathrm{dt}}+u_o+L\frac{{\mathrm{di}}_o}{\mathrm{dt}}+R_L{i}_o=u_{\mathrm{inv}}---\left(10\right)$

In conventional voltage control method, inverter parallel output voltage control is mostly realized using PI controls, in order to realize the zero steady state error control of inverter output voltage, the control performance when micro-capacitance sensor frequency changes is improved simultaneously, employ quasi-resonance PR controllers and realize voltage control, the transmission function of quasi-resonance PR controllers is：

$G\left(s\right)=k_{\mathrm{pr}}+\frac{{2k}_r{\mathrm{\ω}}_{c}s}{s^2+2{\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2}---\left(11\right)$

Wherein, k_prAnd k_rFor the coefficient of quasi-resonance PR controllers, ω_cFor the cut-off frequency of low pass filter.

In order that inverter output impedance is in resistive under the conditions of power frequency, and possess higher performance, introduce virtual complex impedanceWherein, R_DFor virtual resistance value, L_sFor output inductor value, k_LFor virtual inductor coefficient, ω_cThe introducing of low pass filter can be effectively prevented from high-frequency noise interference.It is assumed that output voltage reference value is u_ref, it is hereby achieved that

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-L_D\frac{s}{s+{\mathrm{\ω}}_c})i_o={u^{*}}_{\mathrm{ref}}-Z_V\left(s\right)i_o---\left(12\right)$

By introducing the virtual complex impedance Z containing resistive component and induction reactance component_V(s), virtual resistance component increases inverter output resistance, and virtual induction reactance component reduces inverter output induction reactance, and the output impedance that can make shunt chopper is purely resistive under the conditions of power frequency.

In order to further improve system control performance, capacitive current inner ring controlling unit is introduced, with the robustness of strengthening system.Meanwhile, in order to reduce influence of the voltage pulsation to current inner loop, introduce electric voltage feed forward link k_Uu_o, k_UFor output voltage feedback factor.Reference current

Computing formula is

$i_c^{*}=(u_{\mathrm{ref}}-u_o)G\left(s\right)+k_U{u}_o---\left(13\right)$

Introduce capacitor current feedback coefficient k_c, capacitive current inner ring control is constituted, its output is used as modulated signal.Instruction current

With capacitor current feedback signal k_ci_cProportion adjustment is carried out, SPWM modulation wave signal D are obtained, its computing formula is：

$D=k_{\mathrm{pc}}(i_c^{*}-k_c{i}_c)---\left(14\right)$

Wherein, k_pcFor proportionality coefficient.

Obtained SPWM modulating waves and triangular carrier carries out bipolar modulation, the duty cycle signals of switching tube is drawn, through Drive Protecting Circuit, controlling switch pipe S₁~S₄Open and turn off.Pulsewidth modulation link is equivalent to the scaling gain k that a multiplication factor is proportional to DC bus-bar voltage_PWM, then by being inverter output voltage u after the link_inv.LC filtering is carried out to inverter output voltage, high fdrequency component is filtered, inverter output fundamental voltage, i.e. inverter output filter capacitor voltage u can be obtained_o。

Fig. 5 show the two inverter parallel current simulations oscillograms using the micro-capacitance sensor multi-inverter parallel voltage control method based on robust power droop control.It is assumed that inverter capacity is 2.5kVA, the line impedance value of inverter 1 is 0.15+j0.02 Ω, and the line impedance value of inverter 2 is 0.25+j0.035 Ω, and carrier frequency is set to 12.8kHz, loads the resistive load for 2.2kW.i₁、i₂Respectively flow through inverter 1, the electric current of 2 connection lines, i_HFor the circulation between inverter, i is defined as_H=(i₁-i₂)/2.There was only the isolated operation of inverter 1, i before 0.6s_H=i₁/2；0.6s inverters 2 are incorporated to system, electric current i₁Gradually become original half.After transient process terminates, i₁With i₂Amplitude, phase it is essentially identical, i_HAlso zero is tended to be essentially.

Claims (2)

1. a kind of micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control, including micro-capacitance sensor multi-inverter parallel system, the micro-capacitance sensor multi-inverter parallel system include several inverters in parallel, the inverter accesses micro-capacitance sensor；The inverter includes dc source, inverter circuit, LC filter circuits, A/D sample circuits, phase-locked loop circuit, controller, Drive Protecting Circuit, touch-screen; the dc source, inverter circuit, LC filter circuits are sequentially connected, and the LC filter circuits access micro-capacitance sensor；The A/D sample circuits input is connected with the LC filter circuits；The controller is connected with the Drive Protecting Circuit input, A/D sample circuits output end, touch-screen, phase-locked loop circuit output end；The phase-locked loop circuit input is connected with power network；The Drive Protecting Circuit drives the inverter circuit, it is characterised in that as follows the step of this method：

1）In the starting point in each sampling period, controller is by A/D sample circuits to inverter output filter capacitor voltage u_oWith filter capacitor electric current i_c, line current i_oSampled respectively, sampled data is given controller and handled；

2）By inverter output filter capacitor voltage u_oAfter 90 ° of phase shift, with line current i_oMultiplication obtains q, inverter output filter capacitor voltage u_oWith line current i_oMultiplication obtains reactive power average value Q in p, power frequency period and active power mean value P computing formula is as follows：

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}p\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}q\left(k\right)=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{u}_o\left(k\right)i_o(k-\frac{N}{4})\end{array}\right.$

Wherein, k is sampling sequence number in power frequency period, and N is the sampling number in power frequency period；

3）Inverter output filter capacitor voltage u is calculated using discrete Fourier transform_oIn the virtual value U of a cycle_o, output voltage amplitude reference value E^*Subtract U_o, obtained difference is multiplied by COEFFICIENT K_e, then P and sagging coefficient n product are subtracted, obtained difference passes through integral operation, obtains the virtual value E of reference voltage, and its time-domain expression is：

$E=(K_e(E^{*}-U_o)-\mathrm{nP})\frac{K_I}{s},$

Wherein, K_IFor integral coefficient, s is complex frequency；

4）Angular frequency reference value ω^*Plus Q and the product of sagging Coefficient m, the integrated computing of both sums obtains referring to angular frequency, and its time-domain expression is：

$\mathrm{\ω}=({\mathrm{\ω}}^{*}+\mathrm{mQ})\frac{K_I}{s};$

5）By the virtual value E of reference voltage and with reference to angular frequency and phase-locked loop circuit output synchronous phase angle

Synthesized reference voltage u^* _ref, its computing formula is：

Wherein, phase angle

For presynchronization signal；

6）Virtual resistance component and virtual inductor component are introduced, by reference voltage u^* _refSubtract line current i_oWith the product of virtual impedance, LC filtering circuit capacitor voltage reference values u is obtained_ref, its computing formula is：

$u_{\mathrm{ref}}={u^{*}}_{\mathrm{ref}}-(R_D-k_L{L}_s\frac{s}{s+{\mathrm{\ω}}_c})i_o$

Wherein, ω_cFor the cut-off frequency of low pass filter, R_DFor virtual resistance value, L_sFor LC filter circuit inductance values, k_LFor virtual inductor coefficient；

7）By u_refAnd u_oAs the input of quasi-resonance PR controllers, the reference value i of LC filtering circuit capacitor electric currents is obtained_ref；The transmission function of quasi-resonance PR controllers is：

$G\left(s\right)=k_{\mathrm{pr}}+\frac{{2k}_r{\mathrm{\ω}}_{c}s}{s^2+{2\mathrm{\ω}}_{c}s+{\mathrm{\ω}}^2}$

Wherein, k_prAnd k_rFor the coefficient of quasi-resonance PR controllers；

8）Introduce LC filtering circuit capacitor electric voltage feed forward links k_Uu_o, obtain reference current

k_UFor voltage feedback factor, $i_c^{*}=(u_{\mathrm{ref}}-u_o)G\left(s\right)+k_U{u}_o;$

9）

With LC filtering circuit capacitor current feedback signals k_ci_cProportion adjustment is carried out, SPWM modulation wave signals D is obtained：

k_pcFor proportionality coefficient, k_cFor capacitor current feedback coefficient；

10）SPWM modulating waves and triangular carrier carry out bipolar modulation, the duty cycle signals of switching tube are drawn, through Drive Protecting Circuit, controlling switch pipe S₁~S₄Open and turn off.

2. the micro-capacitance sensor multi-inverter parallel voltage control method of robust power droop control according to claim 1, it is characterised in that the controller is dsp controller.

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