CN104935015A - Virtual synchronous inversion control based energy storage system - Google Patents

Abstract

The invention relates to a virtual synchronous inversion control based energy storage system which comprises a battery, a DC/DC converter, a DC/AC converter, a transformer, an AC power grid, a first controller and a second controller. According to the energy storage system, a virtual synchronous motor control technology is adopted, so that external characteristics of an AC interface of an energy storage apparatus with a power electronic system can be equivalent to characteristics of a synchronous motor, inertial and damping characteristics of a power electronic energy storage system are improved, and the stability of a power system is enhanced.

Description

Based on the energy-storage system of virtual synchronous inversion control

Technical field

The present invention relates to intelligent grid, particularly a kind of energy-storage system based on virtual synchronous inversion control.

Background technology

Because power electronic equipment does not almost have moment of inertia and damping characteristic, so consider the problem of energy-storage system discharge and recharge from two kinds of angles.

Consider from the angle of electrical network, set up and improve a kind of electrical network form---intelligent grid more friendly to generation of electricity by new energy, the problem of generation of electricity by new energy can be solved well.Topmost two features of intelligent grid are exactly intelligent and utilize regenerative resource on a large scale.In following intelligent grid, AC network is as the main power transmission mode of electric power system, and direct current transportation is as the important useful supplement of ac transmission.Compared to AC network, direct current network is more friendly to generation of electricity by new energy.Small-sized DC distribution net can be set up in small-sized distributed power generation (mainly referring to wind power generation and photovoltaic generation) concentrated place, after final unified inversion, be incorporated to large-scale ac transmission network.Due to the access of extensive new forms of energy equipment, energy storage device is also the indispensable necessaries of following intelligent grid.Building intelligent grid is the essential measure solving new energy power generation grid-connection.

Considering from the angle of inverter, there is another kind of thinking in the transformation of AC network and development.The Blast Furnace Top Gas Recovery Turbine Unit (TRT) (thermal power generation, hydroelectric power generation etc.) of tradition bulk power grid is nearly all generated electricity by synchronous generator, if the inverter in distribution is looked from net side can present the operation characteristic of synchronous generator, so just can be well compatible with traditional electrical network.For this reason, need to transform inverter, make it look from net side and present the characteristic of synchronous generator, thus the stability of electrical network of increasing exchanges.

Based on the virtual synchronous inversion controlling method of energy-storage system, according to the electromagnet inertia of synchronous generator, inverter is controlled, more can reflect the characteristic of synchronous generator.The electromagnetic property of synchronous generator, rotor inertia, primary frequency modulation and excitation voltage adjustment characteristic is simulated in controller, the characteristic of synchronous generator more can be simulated from external characteristic, and there is integral element due to idle, real power control part, idle, meritorious indifference can be realized control, and greatly can improve the stability of a system.

Summary of the invention

The object of the present invention is to provide a kind of energy-storage system based on virtual synchronous inversion control, this system is when battery charges, and inverter adopts the control strategy of virtual synchronous inversion transformation technique, can improve inertia and the damping characteristic of system, strengthens the stability of system.

Technical solution of the present invention is as follows:

Based on an energy-storage system for virtual synchronous inversion control, its feature is, comprises battery, DC/DC converter, DC/AC converter, transformer, AC network, the first controller and second controller;

Described battery is connected with the input of DC/DC converter, the output of described DC/DC converter is connected with the input of described DC/AC converter, the output of this DC/AC converter is connected with the low pressure input of described transformer, and the high-voltage output end of described transformer is connected with AC network;

The output of the first described controller is connected with the control end of described DC/DC converter, the input of the first controller is connected with the output of DC/DC converter, the output of described second controller is connected with the control end of DC/AC converter, and the input of second controller is connected with the output of described DC/AC converter;

The first described controller comprises the first comparator and a PI controller, the input of output termination the one PI controller of this first comparator;

Described second controller comprises virtual synchronous inversion control, power control, Current Control, voltage coordinate modular converter, electric current coordinate transferring and inverse coordinate transferring six part, and described virtual synchronous inversion control part comprises mechanical part, excitation system, angular transition module and electric part;

Described mechanical part output connects the input of described angular transition module and the input of described inverse coordinate transferring respectively, the output of described angular transition module connects the input of described voltage coordinate modular converter and the input of electric current coordinate transferring respectively, the input of the electric part described in output termination of described voltage coordinate modular converter, the input of the electric part described in output termination of described excitation system, the input of Current Control described in the output termination of described electric part, the input of the Current Control described in output termination that described power controls, the input of the inverse coordinate transferring described in the output termination of described Current Control,

Described mechanical part comprises the second comparator, the 3rd comparator, hypothetical rotor inertial element, first adder and the first integrator that connect successively, second input of output through adjusting poor feedback element to connect the second described comparator of described hypothetical rotor inertial element;

Described excitation system comprises the 4th comparator, virtual magnetizing exciter and the first compensator, and the output of described virtual magnetizing exciter connects the second input of the 4th comparator through the first described compensator;

Described power control section is divided and is comprised the 5th comparator and the 2nd PI controller, the 6th comparator and the 3rd PI controller;

Described current control division divides and comprises the control of d axle component and the control of q axle component, described d axle component controls to comprise second adder, the 7th comparator and the 4th PI controller, and described q axle component controls to comprise the 3rd adder, the 8th comparator and the 5th PI controller.

The first described controller and second controller are digital signal processor, single-chip microcomputer or computer.

Described DC/DC converter is DC converter that is high-power, wide output voltage range.

Described DC/AC converter adopts virtual synchronous inversion control to become with the direct current that conventional power controls the comprehensive controling algorithm combined the converter exchanged, realize the object whole energy-storage system being equivalent to a synchronous generator viewed from net side, the voltage of responsive electricity grid and frequency disturbance adaptively, strengthens inertial properties and the damping characteristic of system.

The control method of the energy-storage system based on virtual synchronous inversion control described in utilization, its feature is, the method comprises following content and step:

1) initialization, sets following parameter value by operator according to system requirements in this energy-storage system:

The DC bus-bar voltage reference value of DC/AC converter

The electromagnetic power reference value P of energy-storage system _ref;

The reactive power reference qref Q of energy-storage system _ref;

Setting difference coefficient R is between 30-50, inertia constant M is between 1-20, load-damping constant D is 1% or 2%;

Setting hypothetical rotor x _qwith the impedance x of stator _dbe between 1-10;

AC voltage reference value U _ref, per unit value is set to 1;

The gain K of the first compensator of setting excitation system _fwith time constant T _fbetween 0-1, the gain K of excitation system _abetween 100-500, excitation system time constant T _ebetween 0-1, the upper limit E of exciting voltage amplitude _fmaxbetween 0-15, the lower limit E of exciting voltage amplitude _fmin=-E _fmax;

The hypothetical rotor transient state impedance x ' of setting electric part _dspan between 0.1-0.5, the transient state impedance x ' of stator _qspan between 0.3-1, the transient state open circuit time constant T ' of d axle _dospan between 1.5-10, the transient state open circuit time constant T ' of q axle _qospan between 0.5-2.0;

The control coefrficient of the one PI controller is k _p1and k _i1, 0<k _p1<1000,0<k _i1<1000;

The control coefrficient of the 2nd PI controller is k _p2and k _i2, 0<k _p2<1000,0<k _i2<1000;

The control coefrficient of the 3rd PI controller is k _p3and k _i3, 0<k _p3<1000,0<k _i3<1000;

The control coefrficient of the 4th PI controller is k _p4and k _i4, 0<k _p4<1000,0<k _i4<1000;

The control coefrficient of the 5th PI controller is k _p5and k _i5, 0<k _p5<1000,0<k _i5<1000;

Adopt Hall element to sample to DC voltage, AC voltage and current, obtain the output end voltage U of DC/DC converter (2) _dc, unit is per unit value, and grid side three-phase voltage e _a, e _b, e _cwith grid side three-phase current i _a, i _b, i _c;

2), the first controller performs according to the following steps:

21), the first comparator calculates the input value of a PI controller:

22), a PI controller calculates after the output receiving above-mentioned first comparator, exports corresponding controlled quentity controlled variable: $k_{p1}(U_{dc}^{*}-U_{dc})+k_{i1}\&Integral;(U_{dc}^{*}-U_{dc})dt;$

3) mechanical part of the virtual synchronous inversion control of second controller (7) performs according to the following steps:

31), following formulae discovery virtual machine power P is pressed by the second comparator _m:

$P_m=P_{ref}-\frac{1}{R}\mathrm{\&Delta;}\mathrm{\&omega;},$

Wherein, P _refbe the electromagnetic power reference value of setting, R is difference coefficient, and Δ ω is hypothetical rotor offset for the output variable of hypothetical rotor inertial element, M is the inertia constant in hypothetical rotor inertial element, and D is the load-damping constant in hypothetical rotor inertial element, and s is complex frequency, and the initial value of Δ ω is set to zero;

32), by the virtual accelerating power P of the 3rd comparator calculating machine part _a:

P _a=P _m-P _e, wherein P _efor the electromagnetic power of mechanical part, P _e=e _ai _a+ e _bi _b+ e _ci _c;

33), calculating angular speed by first adder is: ω=ω ₀+ Δ ω, ω ₀for the initial value of angular speed, when mains frequency is 50Hz, then ω ₀=2 × π × 50=314rad/s;

34), synchronous angle is calculated by first integrator: θ=∫ ω; θ is the input of angular transition module;

35), by angular transition module carry out angle compensation, formula is as follows:

$tan\left({\mathrm{\&theta;}}_0\right)=\frac{x_{q}I}{e_g}$

${\mathrm{\&theta;}}^{\&prime;}=\mathrm{\&theta;}-(\frac{\mathrm{\&pi;}}{2}-{\mathrm{\&theta;}}_0)$

Wherein, θ ' is phase-locked angle; I is power network current amplitude; e _gfor grid voltage amplitude; x _qfor hypothetical rotor impedance;

4), the excitation system of second controller virtual synchronous inversion control performs according to the following steps:

41) the input variable U of virtual magnetizing exciter, is calculated by the 4th comparator _t, formula is as follows:

U _t＝U _ref-U _x

Wherein: U _reffor the AC magnitude of voltage of setting, K _fand T _fbe gain and the time constant of the first compensator; U _xbe the output of the first compensator;

42) the virtual exciting voltage E of input of electric part, is calculated by virtual magnetizing exciter _f, formula is as follows:

$E_f=\frac{K_a}{T_{e}s+1}{U}_t,$

Wherein: K _aand T _ebe respectively gain and the time constant of virtual magnetizing exciter, E _fmaxand E _fminbe respectively the upper and lower bound of the voltage magnitude of virtual magnetizing exciter;

43), U is calculated by the first compensator _x, formula is as follows:

$U_t=\frac{{\mathrm{sK}}_f}{T_{f}s+1}{E}_f.$

5), voltage coordinate conversion module and electric current coordinate transformation module perform according to the following steps:

51), by e _a, e _band e _cline voltage d-q component U is calculated through voltage coordinate conversion module _dand U _q, formula is as follows:

$\left[\begin{array}{c}{U}_d\\ U_q\end{array}\right]=\frac{\sqrt{2}}{\sqrt{3}}\left[\begin{array}{ccc}\cos \mathrm{\&theta;}& \cos \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)& \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\\ -\sin \mathrm{\&theta;}& -\sin \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)& -\sin \left(\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\right)\end{array}\right]\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right]$

52), by i _a, i _band i _cline voltage d-q component i is calculated through electric current coordinate transformation module _dand i _q, formula is as follows:

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\frac{\sqrt{2}}{\sqrt{3}}\left[\begin{array}{ccc}\cos \mathrm{\&theta;}& \cos \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)& \cos (\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\\ -\sin \mathrm{\&theta;}& -\sin \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)& -\sin \left(\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\right)\end{array}\right]\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]$

6), the electric part of second controller virtual synchronous inversion control performs according to the following steps:

61), calculating current is with reference to I _dref1and I _qref1, formula is as follows:

$I_{dref1}=\frac{E_f-(T_{d0}^{\&prime;}s+1)U_q}{x_d^{\&prime;}{T}_{d0}^{\&prime;}s+x_d}$

$I_{qref1}=\frac{(T_{q0}^{\&prime;}s+1)U_d}{x_q^{\&prime;}{T}_{q0}^{\&prime;}s+x_q}$

Wherein: U _dand U _qit is the d-q component of line voltage; I _dref1and I _qref1the virtual stator current part of described DC/AC converter (3) output current, E _fit is virtual exciting voltage;

7), second controller power control section divides execution according to the following steps:

71) input of the 2nd PI controller, is calculated by the 5th comparator: P _ref-P _e;

72), the 2nd PI controller carries out control algorithm after the output receiving above-mentioned 5th comparator, exports corresponding controlled quentity controlled variable I _dref2: I _dref2=k _p2(P _ref-P _e)+k _i2∫ (P _ref-P _e) dt; Be the input of Current Control part;

73) input of the 3rd PI controller, is calculated by the 6th comparator: Q _ref-Q _e;

74), the 3rd PI controller carries out control algorithm after the output receiving above-mentioned 6th comparator, exports corresponding controlled quentity controlled variable I _qref2:

I _qref2=k _p3(Q _ref-Q _e)+k _i3∫ (Q _ref-Q _e) dt; Be the input of Current Control part;

8), the d axle component of second controller (7) Current Control part controls to perform according to the following steps:

81) d shaft current reference value I, is calculated _dref, formula is as follows:

I _dref＝I _dref1+I _dref2；

82) input of the 4th PI controller, is calculated by the 7th comparator: I _dref-I _d; I _dfor three-phase current d axle component, by i _a, i _band i _cexport through coordinate transform;

83), the 4th PI controller carries out control algorithm after the output receiving above-mentioned 7th comparator, exports mutually deserved controlled quentity controlled variable U _dref: U _dref=k _p4(I _dref-I _d)+k _i4∫ (I _dref-I _d) dt;

9), the q axle component of second controller Current Control part controls to perform according to the following steps:

91) q shaft current reference value I, is calculated _qref, formula is as follows:

I _qref＝I _qref1+I _qref2；

92) input of the 5th PI controller, is calculated by the 8th comparator: I _qref-I _q; I _qfor three-phase current q axle component, by i _a, i _band i _cexport through coordinate transform;

93), the 5th PI controller carries out control algorithm after the output receiving above-mentioned 8th comparator, exports mutually deserved controlled quentity controlled variable U _qref: U _qref=k _p5(I _qref-I _q)+k _i5∫ (I _qref-I _q) dt;

10), second controller output variable:

101), by obtained U _drefand U _qrefthrough inverse coordinate transformation module conversion, obtain U _aref, U _brefand U _crefthree modulating waves, using these three amounts as control signal and carrier wave ratio comparatively, the control signal of acquisition DC/AC converter (3), formula is as follows:

$\left[\begin{array}{c}{U}_{aref}\\ U_{bref}\\ U_{cref}\end{array}\right]=\frac{\sqrt{2}}{\sqrt{3}}\left(\begin{array}{cc}\cos \mathrm{\&theta;}& -\sin \mathrm{\&theta;}\\ \cos \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)& -\sin \left(\mathrm{\&theta;}-\frac{2}{3}\mathrm{\&pi;}\right)\\ \cos \left(\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\right)& -\sin \left(\mathrm{\&theta;}+\frac{2}{3}\mathrm{\&pi;}\right)\end{array}\right)\left[\begin{array}{c}{U}_{dref}\\ U_{qref}\end{array}\right].$

Technique effect of the present invention is as follows:

In present system, the DC/AC inverter be connected with grid side adopts the control method of virtual synchronous inversion transformation technique, supports and voltage support to the frequency of electrical network necessity, improves the stability of system.Its feature is as follows:

1, because the external characteristic of power electronic system interchange interface is equivalent to synchronous generator characteristic, make accumulator cell charging and discharging interface equipment can participate in electrical network mutual, provide necessary support to line voltage and frequency, can grid stability be improved.

2. adopt have high power transmission ability, the DC/DC converter of wide output voltage range, response speed and the control precision of system can be improved.

Accompanying drawing explanation

Fig. 1 is the entire block diagram of the energy-storage system that the present invention is based on virtual synchronous inversion transformation technique.

Fig. 2 is the overall control block diagram of virtual synchronous inversion control.

Fig. 3 is mechanical part control block diagram.

Fig. 4 is Excitation Controller block diagram.

Fig. 5 is the first controller control block diagram.

Fig. 6 is second controller power control block figure.

Fig. 7 is second controller Current Control block diagram.

Fig. 8 is angular transition module

Fig. 9 is system control process figure.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the invention will be further described, and nitrogen should not limit the scope of the invention with this.

Refer to Fig. 1, Fig. 1 is the energy-storage system schematic diagram that the present invention is based on virtual synchronous inversion transformation technique, comprise battery 1, DC/DC converter 2, DC/AC converter 3, transformer 4, AC network 5, first controller 6 and second controller 7, introduce each part in detail below:

Described battery 1 is for energy-storage system provides the equipment of stored energy and Energy transmission;

DC/DC converter 2 is converters that are high-power, wide output voltage range;

DC/AC converter 3 adopts the control method of virtual synchronous inversion transformation technique and conventional power to control the comprehensive controling algorithm combined, realize the object whole energy-storage system being equivalent to a synchronous generator viewed from net side, the voltage of responsive electricity grid and frequency disturbance adaptively, strengthens inertial properties and the damping characteristic of system.

First controller 6 is responsible for the sampling of DC/DC converter 2, process, calculating and control etc.;

Second controller 7 is responsible for data sampling, process, calculating and control etc., controls the DC/AC converter 3 of net side.

Described battery 1 is connected with the input of DC/DC converter 2, the output of described DC/DC converter 2 is connected with the input of described DC/AC converter 3, the output of this DC/AC converter 3 is connected with the low pressure input of described transformer 4, and the high-voltage output end of described transformer 4 is connected with AC network 5;

The output of the first described controller 6 is connected with the control end of described DC/DC converter 2, the input of the first controller 6 is connected with the output of DC/DC converter 2, the output of described second controller 7 is connected with the control end of DC/AC converter 3, and the input of second controller 7 is connected with the output of described DC/AC converter 3.

Fig. 2 is the control block diagram of the first controller 6, and the first described controller 6 comprises the first comparator and a PI controller, the input of output termination the one PI controller of this first comparator.

Described second controller 7 comprises virtual synchronous inversion control, power control, Current Control, voltage coordinate modular converter, electric current coordinate transferring and inverse coordinate transferring six part, and described virtual synchronous inversion control part comprises mechanical part, excitation system, angular transition module and electric part;

Described mechanical part output connects the input of described angular transition module and the input of described inverse coordinate transferring respectively, the output of described angular transition module connects the input of described voltage coordinate modular converter and the input of electric current coordinate transferring respectively, the input of the electric part described in output termination of described voltage coordinate modular converter, the input of the electric part described in output termination of described excitation system, the input of Current Control described in the output termination of described electric part, the input of the Current Control described in output termination that described power controls, the input of the inverse coordinate transferring described in the output termination of described Current Control,

Described mechanical part comprises the second comparator, the 3rd comparator, hypothetical rotor inertial element, first adder and the first integrator that connect successively, second input of output through adjusting poor feedback element to connect the second described comparator of described hypothetical rotor inertial element;

Described excitation system comprises the 4th comparator, virtual magnetizing exciter and the first compensator, and the output of described virtual magnetizing exciter connects the second input of the 4th comparator through the first described compensator;

Described power control section is divided and is comprised the 5th comparator and the 2nd PI controller, the 6th comparator and the 3rd PI controller;

Described current control division divides and comprises the control of d axle component and the control of q axle component, described d axle component controls to comprise second adder, the 7th comparator and the 4th PI controller, and described q axle component controls to comprise the 3rd adder, the 8th comparator and the 5th PI controller.

Fig. 3 is the overall control block diagram of virtual synchronous inversion control, Fig. 4 is mechanical part control block diagram, Fig. 5 is the exciter control system of virtual synchronous inversion controlling method, Fig. 6 is the power control block figure of second controller 7, Fig. 7 is the Current Control block diagram of second controller, Fig. 8 is angular transition module diagram, and Fig. 9 is the overall control flow chart of present system.Fig. 4, Fig. 5, Fig. 6 and Fig. 7 are included in Fig. 3.

Claims (4)

1. the energy-storage system based on virtual synchronous inversion control, it is characterized in that, comprise battery (1), DC/DC converter (2), DC/AC converter (3), transformer (4), AC network (5), the first controller (6) and second controller (7):

Described battery (1) is connected with the input of DC/DC converter (2), the output of described DC/DC converter (2) is connected with the input of described DC/AC converter (3), the output of this DC/AC converter (3) is connected with the low pressure input of described transformer (4), and the high-voltage output end of described transformer (4) is connected with AC network (5);

The output of described the first controller (6) is connected with the control end of described DC/DC converter (2), the input of the first controller (6) is connected with the output of DC/DC converter (2), the output of described second controller (7) is connected with the control end of DC/AC converter (3), and the input of second controller (7) is connected with the output of described DC/AC converter (3);

Described the first controller (6) comprises the first comparator and a PI controller, the input of output termination the one PI controller of this first comparator;

Described second controller (7) comprises virtual synchronous inversion control, power control, Current Control, voltage coordinate modular converter, electric current coordinate transferring and inverse coordinate transferring six part, and described virtual synchronous inversion control part comprises mechanical part, excitation system, angular transition module and electric part;

Described mechanical part output connects the input of described angular transition module and the input of described inverse coordinate transferring respectively, the output of described angular transition module connects the input of described voltage coordinate modular converter and the input of electric current coordinate transferring respectively, the input of the electric part described in output termination of described voltage coordinate modular converter, the input of the electric part described in output termination of described excitation system, the input of Current Control described in the output termination of described electric part, the input of the Current Control described in output termination that described power controls, the input of the inverse coordinate transferring described in the output termination of described Current Control,

Described mechanical part comprises the second comparator, the 3rd comparator, hypothetical rotor inertial element, first adder and the first integrator that connect successively, second input of output through adjusting poor feedback element to connect the second described comparator of described hypothetical rotor inertial element;

Described excitation system comprises the 4th comparator, virtual magnetizing exciter and the first compensator, and the output of described virtual magnetizing exciter connects the second input of the 4th comparator through the first described compensator;

Described power control section is divided and is comprised the 5th comparator and the 2nd PI controller, the 6th comparator and the 3rd PI controller;

Described current control division divides and comprises the control of d axle component and the control of q axle component, described d axle component controls to comprise second adder, the 7th comparator and the 4th PI controller, and described q axle component controls to comprise the 3rd adder, the 8th comparator and the 5th PI controller.

2. the energy-storage system based on virtual synchronous inversion control according to claim 1, is characterized in that, described the first controller (6) and second controller (7) are digital signal processor, single-chip microcomputer or computer.

3. the energy-storage system based on virtual synchronous inversion control according to claim 1, is characterized in that, described DC/DC converter (2) is DC converter that is high-power, wide output voltage range.

4. the energy-storage system based on virtual synchronous inversion control according to claim 3, it is characterized in that, described DC/AC converter (3) adopts virtual synchronous inversion control to become with the direct current that conventional power controls the comprehensive controling algorithm combined the converter exchanged, realize the object whole energy-storage system being equivalent to a synchronous generator viewed from net side, the voltage of responsive electricity grid and frequency disturbance adaptively, strengthens inertial properties and the damping characteristic of system.