CN102611117B - LC-VSI device reactive compensation control method based on self-adaptive control DC side voltage - Google Patents

Abstract

The invention discloses an LC-VSI device reactive compensation control method based on a self-adaptive control DC side voltage, which is suitable for a three-phase four-line and a three-phase three-line power systems. The LC-VSI device reactive compensation control method comprises the following steps of: firstly, figuring out a minimum DC side voltage required by three phases of an LC-VSI device through a reactive power QLxf of each phase of load, self-adaptively regulating a reference DC side voltage level Vdc; secondly, figuring out a reactive compensation current and a compensation current required by each phase through transient reactive powers of three phases, summating the two currents to obtain a final reference compensation current icx* of the LC-VSI device, wherein the compensation current is used for controlling the DC side voltage to track the self-adaptive reference DC side voltage value; and finally, controlling the inverter by using a PWM (Pulse Width Modulation) method to output a compensation current icx to track the final reference current icx*, and carrying out dynamic reactive compensation and self-adaptive DC side voltage control of the LC-VSI device. The invention can self-adaptively regulate the required DC capacitance voltage level, thus the purpose of optimizing and reducing loss and noise when an active part operates is achieved.

Description

Regulate the LC-VSI device power-less compensation control method of DC voltage based on self adaptation

Technical field

The power-less compensation control method that the present invention relates to a kind of compensation arrangement based on LC-coupled voltages type inverter structure, belongs to the Semiconductor Converting Technology field in electrical engineering.

Background technology

Shunt capacitor and compensator etc. that traditional reactive power compensation means have machinery to drop into, but they all exist some problems, as shunt capacitor operation inconvenience, easily resonate, and in the time that system voltage reduces, can not effectively provide the shortcomings such as reactive power support.Although and compensator dynamic property is better, range of operation is also wider, owing to comprising rotating part, its equipment and operating cost are all higher.The appearance of flexible AC power transmission and distribution (FACTS/DFACTS) technology has brought new control technology and application means to electric power system.Static var compensator (Static Var Compensator, SVC), STATCOM (Static Synchronous Compensator, STATCOM) and Active Power Filter-APF (APF) be all the important FACTS/DFACTS equipment that can be used to carry out reactive power compensation, its Men has high dynamic response speed, roomy compensation range, can suppress resonance problems, but it is first and operating cost is high.

LC-coupled voltages type inverter (LC-VSI) is applied to STATCOM and APF and just forms LC-coupling STATCOM (LC-STATCOM) and the LC-hybrid active electric filter (LC-HAPF) that is coupled, as " static state synchronization reactive compensator connecting by capacitive reactances and control method " (Chinese invention patent, open day: on April 15th, 2009, publication number: CN101409450A), " middle pressure hybrid active electric filter " (Chinese invention patent, open day: on August 22nd, 2007, publication number CN101022218A), " hybrid active electric filter and control method thereof " (Chinese invention patent, open day: on May 30th, 2007, publication number CN1972060A).LC-STATCOM and LC-HAPF can make the output voltage of voltage source inverter (VSI) can be far below system voltage, thereby greatly reduce the voltage of inverter direct current component, reduce cost and the switching loss of LC-STATCOM and LC-HAPF reactive power compensation.

LC-STATCOM and the LC-HAPF reference DC voltage in the time of running is all changeless, but when the reactive power providing when Passive LC part almost can full compensating load reactive power, the DC voltage of LC-STATCOM and the required compensating reactive power of LC-HAPF active part requires can be very low, if this LC-STATCOM and LC-HAPF still operate in the fixing DC voltage level of design, thereby having increased loss and the noise of switch module, the efficiency and the compensation effect that reduce LC-STATCOM and LC-HAPF are undesirable.

Summary of the invention

The object of the invention is in order to make the compensation arrangement based on LC-coupled voltages type inverter (LC-VSI) structure, as LC-STATCOM and LC-HAPF, can make dynamic passive compensation to electric power system, and can be at loss and the noise of run-time optimizing and minimizing switch module, improve efficiency and the compensation effect of device, propose a kind of under different loads reactive power scope self adaptation regulate the power-less compensation control method of DC voltage LC-VSI device.

In order to realize above object, the invention provides a kind of LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation, be applicable to the electric power system of three-phase and four-line and phase three-wire three, first control method comprises the steps:, calculate the required minimum direct current side voltage of LC-VSI device three-phase by every phase load reactive power Q Lxf, according to minimum direct current side voltage, self adaptation regulates with reference to the horizontal V of DC voltage _dc ^*; Then, calculate every reactive power compensation electric current needing mutually and control the offset current of DC voltage tracking adaptive with reference to DC voltage value by the instantaneous reactive of three-phase, above-mentioned two current summations are obtained to LC-VSI ^*install final reference offset current i _cx; Afterwards, utilize PWM method control inverter output offset current i _cx ^*follow the tracks of final reference current i _cx, carry out the control of LC-VSI device dynamic passive compensation and self adaptation direct current side voltage.

In above-mentioned control method, calculate every phase load reactive power method specific as follows:

$\left[\begin{array}{c}{v}_{\mathrm{x\α}}\\ v_{\mathrm{x\β}}\end{array}\right]=\left[\begin{array}{c}{v}_x\left(\mathrm{\ωt}\right)\\ v_x(\mathrm{\ωt}+\mathrm{\π}/2)\end{array}\right],\left[\begin{array}{c}{i}_{\mathrm{Lx\α}}\\ i_{\mathrm{Lx\β}}\end{array}\right]=\left[\begin{array}{c}{i}_{\mathrm{Lx}}(\mathrm{\ωt}+{\mathrm{\θ}}_{\mathrm{Lx}})\\ i_{\mathrm{Lx}}(\mathrm{\ωt}+\mathrm{\π}/2+{\mathrm{\θ}}_{\mathrm{Lx}})\end{array}\right],$ X=a, b, c phase, ω=2 π f

Wherein vx is system phase voltage, and iLx is load-side electric current, and f is system fundamental frequency, θ _lxfor the phase angle of every phase load electric current; Utilize single-phase Instantaneous Power Theory, can be every phase v _xand i _lxtransform on orthogonal alpha-beta coordinate system, can obtain α axle and β axle instantaneous system phase voltage v under alpha-beta coordinate system _{x α}, v _{x β}and momentary load side current i _{lx α}, i _{lx β};

According to single-phase Instantaneous Power Theory, the instantaneous meritorious p of every phase _lxand idle q _lxfor:

pLx＝v _xα ⁱ _Lxα+v _xβ ⁱ _Lxβ，q _Lx＝-v _xβ ⁱ _Lxα+v _xα ⁱL _xβ

-q _lx/ 2 just can try to achieve the load reactive power of every phase by low pass filter ;

In above-mentioned control method, obtain every mutually required compensation minimum direct current side magnitude of voltage V _{dc_minx}method as follows:

A) three-phase and four-line LC-VSI device:

For a fixing DC voltage =0.5V _dcbe made as m=1 with modulation index m, every mutually required compensating load reactive power minimum direct current side magnitude of voltage be:

$V_{\mathrm{dc}\_\min x}=2\sqrt{2}{V}_x|1-\frac{{Q_{\mathrm{Lx}}}_f}{\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}\right|}|,x=a,b,c$ Phase

Wherein Vx is system phase voltage effective value, for the reactive compensation power that LC passive leg (PF) provides, X _ccand X _lcfor capacitor C in passive leg (PF) _cand inductor L _cfundamental frequency Xc value and the anti-value of inductance, and

B) phase three-wire three LC-VSI device:

For a fixing DC voltage V _dcvacation is m=1 with modulation index m, its every mutually required compensating load reactive power minimum direct current side magnitude of voltage expression formula be:

$V_{\mathrm{dc}\_\min x}=\frac{3\sqrt{2}}{2}{V}_x|1-\frac{{Q_{\mathrm{Lx}}}_f}{\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}\right|}|$ X=a, b, c phase.

In above-mentioned control method, the minimum direct current side voltage V that LC-VSI device three-phase is required _{dc_min}draw by following formula:

V _{dc_min}=max (V _{dc_mina}, V _{dc_minb}, V _{dc_minc}), x=a, b, c phase.

In above-mentioned control method, described self adaptation regulates with reference to the horizontal V of DC voltage _dc ^*concrete grammar be: with reference to DC voltage V _dc ^*be divided into n electric pressure: V _dc1, V _dc2... V _dcmax, V _dc1< V _dc2< V _dcmax, n=1,2 ... Max, controls, as the required minimum direct current side magnitude of voltage V of three-phase _{dc_min}lower than minimum voltage grade V _dc1, final reference DC voltage V _dc ^*=V _dc1; Otherwise more next high voltage grade V _dc2, repeat this step.

In above-mentioned control method, the method for calculating every reactive power compensation electric current needing is mutually as follows:

Based on Clarke conversion, first the three-phase instantaneous system voltage v under a-b-c coordinate system _a, v _b, v _cand momentary load current i _la, i _lb, i _lctransform on the coordinate system of alpha-beta-0, draw α axle under the coordinate system of alpha-beta-0, β axle and 0 axle instantaneous system phase voltage v _α, v _β, v0 and momentary load side current i _{l α}, i _{l β}, i _l0;

According to Instantaneous Power Theory, instantaneous reactive q _{α β}for:

q _αβ＝-v _β ⁱL _α+v _α ⁱLβ

The needed offset current i of compensating reactive power under the coordinate system of alpha-beta-0 _{c α}, i _{c β}, i _c0can be calculated by following formula:

$i_{\mathrm{ca}}=i_{\mathrm{cap}}+i_{\mathrm{caq}}=0+\frac{-q{\mathrm{a\&beta;}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2},i_{\mathrm{c\&beta;}}=i_{\mathrm{c\&beta;p}}+i_{\mathrm{c\&beta;q}}=0+\frac{q{\mathrm{a\&beta;}}^{v}a}{v_{\mathrm{a\&beta;}}^2},i_{c0}=i_{c0p}=i_{L0}$

Wherein v _α ² _β=v _α ²+ v ² _β, i _{c α p}and i _{c α q}for the instantaneous meritorious and reactive power compensation electric current of α axle under the coordinate system of alpha-beta-0, i _{c β p}and i _{c β q}for the instantaneous meritorious and reactive power compensation electric current of β axle, i _c0pit is the instantaneous meritorious offset current of 0 axle; Afterwards, convert by anti-Clarke, obtain the needed every phase offset current i of compensating reactive power under a-b-c coordinate system _{ca_q}, i _{cb_q}, i _{cc_q}, i _{cx_q}=i _cxp+ i _cxq, x=a, b, c;

Wherein i _cxpand i _cxqfor the instantaneous meritorious and reactive power compensation electric current of every phase (x=a, b, c) under a-b-c coordinate system.

In above-mentioned control method, under the coordinate system of alpha-beta-0, control DC voltage V _dcevery phase offset current of track reference DC voltage Vdc* is calculated by following formula:

$i_{\mathrm{ca}\_\mathrm{dc}}=i_{\mathrm{cap}\_\mathrm{dc}}+i_{\mathrm{caq}\_\mathrm{dc}}=\frac{\mathrm{\&Delta;p}{\mathrm{dc}}^{v}a}{v_{\mathrm{a\&beta;}}^2}+\frac{\mathrm{\&Delta;q}{\mathrm{dc}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2},$

$\begin{array}{c}{i}_{\mathrm{c\&beta;}\_\mathrm{dc}}=i_{\mathrm{c\&beta;p}\_\mathrm{dc}}+i_{\mathrm{c\&beta;q}\_\mathrm{dc}}=\frac{\mathrm{\&Delta;p}{\mathrm{dc}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2}+\frac{\mathrm{\&Delta;q}{\mathrm{dc}}^{v}a}{v_{\mathrm{a\&beta;}}^2},\\ i_{c0\_\mathrm{dc}}=0\end{array}$

Wherein Δ p _dc=-Δ q _dc=kp (V _dc ^*-V _dc), kp is gain, i _{c α p_dc}and i _{c α q_dc}for the instantaneous meritorious and reactive power compensation electric current of α axle control DC voltage under the coordinate system of alpha-beta-0, i _{c β p_dc}and i _{c β q_dc}for the instantaneous meritorious and reactive power compensation electric current of β axle control DC voltage; Convert by anti-Clarke, just can obtain controlling the needed every phase offset current i of DC voltage under a-b-c coordinate system _{ca_dc}, i _{cb_dc}, i _{cc_dc}, i _{cx_dc}=i _{cxp_dc}+ i _{cxq_dc}, x=a, b, c

Wherein i _{cxp_dc}and i _{cxq_dc}for the instantaneous meritorious and reactive power compensation electric current of every phase control DC voltage under a-b-c coordinate system. ^*

In above-mentioned control method, final reference offset current i _cxdefinite method be: instantaneous reactive is calculated to every reactive power compensation current i needing mutually _{cx_q}and control DC voltage tracking adaptive is with reference to the offset current i of DC voltage value _{cx_dc}addition obtains the final reference offset current i of LC-VSI device _cx ^*.

Beneficial effect of the present invention is:

(1), because the reactive power of electric power system load is dynamic change, the active and passive part of self adaptation direct current side voltage LC-VSI device can provide reactive compensation power jointly within the specific limits.

(2) in response to different load reactive power situations, LC-VSI device energy self adaptation regulates required DC capacitor voltage level, thereby reaches loss and noise while optimizing and reduce active part operation, improves efficiency and the compensation effect of LC-VSI device.

(3) the adjustable DC voltage that the present invention proposes is optimized and loss and the noise of the switch module of minimizing system, improve the innovative point of system effectiveness and compensation effect, this innovative point also can be practiced in other phase three-wire threes or three-phase and four-line, and two level are flexible AC electrical power trans mission/distribution system (FACTS/DFACTS) device of level at the most.

Brief description of the drawings

Fig. 1 is the self adaptation direct current side voltage LC-VSI apparatus structure schematic diagram that the present invention proposes.

Fig. 2 is the single-phase fundamental frequency equivalent-circuit model of LC-VSI device provided by the invention.

Fig. 3 is the single-phase fundamental frequency phasor diagram of the stable state of LC-VSI device under inductive load: a is full compensation, b be undercompensation and, c is overcompensation.

Fig. 4 is self adaptation direct current side voltage LC-VSI device control block diagram provided by the invention.

Fig. 5 adopts point LC-VSI structure drawing of device in two level three brachium pontis in emulation example.

Fig. 6 is that in emulation example, self adaptation direct current side voltage LC-VSI device whole dynamic compensation process and oscillogram: a thereof under different inductive loads are load-side reactive power , b is DC voltage V _dcU, V _dcL, c is system side reactive power , d is that LC-VSI device injects reactive power (situation 1 is to situation 6).

Fig. 7 be in emulation example after LC-VSI device compensation A phase voltage and current waveform figure in: a is load-side, and b is system side (when inductive load 1 connects).

Fig. 8 be in emulation example after LC-VSI device compensation A phase voltage and current waveform figure in: a is load-side, and b is system side (when inductive load 1 and 2 connects).

Fig. 9 be in emulation example after LC-VSI device compensation A phase voltage and current waveform figure in: a is load-side, and b is system side (when inductive load 1,2 and 3 connects).

Figure 10 be in emulation example, fix the horizontal LC-VSI device of DC voltage ( , =120V) under different inductive loads, whole emulation dynamic compensation process and oscillogram: a thereof are load-side reactive power , b is DC voltage , , c is mains side reactive power , d is that LC-VSI device injects reactive power (situation 1 is to situation 6).

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is described in further detail.

As shown in Figure 1, self adaptation direct current side voltage LC-VSI device comprises: LC passive leg and the control device of voltage source inverter, connection inverter and electric power system based on all-controlling power electronics device (GTO or IGBT).Described LC passive leg includes series capacitor C _cwith inductor L _c.According to the single-phase fundamental frequency equivalent-circuit model of the LC-VSI device of Fig. 2, can obtain the three kind stable states single-phase fundamental frequency phasor diagram of LC-VSI device under inductive load, as shown in Figure 3.When choosing suitable LC passive leg resistance value, the output voltage of the device of LC-VSI shown in Fig. 3 voltage source inverter can be significantly less than system voltage, this reduces the voltage of voltage source inverter DC capacitor part greatly, the withstand voltage of the selected switch module of corresponding inverter can reduce, thereby reduces cost and the switching loss of device.

The LC-VSI device power-less compensation control method of the self adaptation direct current side voltage proposing for the present invention, its control method adopting comprises: first, calculate every phase load reactive power ( can try to achieve by single-phase instantaneous reactive and low pass filter); Then, by every phase determine the every phase of LC-VSI device and the required compensation of three-phase minimum direct current side magnitude of voltage (V _{dc_minx}, V _{dc_min}), thereby carry out adaptive control.In fact, while being, become because of load reactive power, in order to reduce the impact that the DC voltage moment fluctuates on LC-VSI device compensation performance and effect, inverter is with reference to DC voltage V _dc ^*also be specially divided into n electric pressure (V _dc1, V _dc2... V _dcmax, V _dc1< V _dc2< V _dcmax, n=1,2 ... max) control, as shown in Figure 4.As the required minimum direct current side magnitude of voltage V of three-phase _{dc_min}lower than minimum voltage grade V _dc1, final reference front voltage V _dc ^*=V _dc1; Otherwise, more next high voltage grade V _dc2, and repeat this step, as shown in Figure 4.

Utilize three-phase instantaneous reactive method to calculate every reactive power compensation electric current needing mutually and control the offset current of DC voltage tracking adaptive with reference to DC voltage value, it is exactly final reference offset current i that these two electric currents are added up _cx ^*thereby, carry out the control of the idle and self adaptation direct current side voltage of dynamic compensation, as shown in Figure 4.Shown in structure chart 1 based on LC-VSI device, the implementation procedure of the method is as follows:

(1) calculate every phase load reactive power

Lead the conversion of front or lagging phase angle to consider by pi/2, can be every phase instantaneous system voltage v _a, v _b, v _cand momentary load current i _la, i _lb, i _lctransform to alpha-beta coordinate system, draw α axle and β axle instantaneous system phase voltage v under alpha-beta coordinate system _{x α}, v _{x β}and momentary load current i _{lx α}, i _{lx β}as follows:

$\left[\begin{array}{c}{v}_{\mathrm{x\&alpha;}}\\ v_{\mathrm{x\&beta;}}\end{array}\right]=\left[\begin{array}{c}{v}_x\left(\mathrm{\&omega;t}\right)\\ v_x(\mathrm{\&omega;t}+\mathrm{\&pi;}/2)\end{array}\right],\left[\begin{array}{c}{i}_{\mathrm{Lx\&alpha;}}\\ i_{\mathrm{Lx\&beta;}}\end{array}\right]=\left[\begin{array}{c}{i}_{\mathrm{Lx}}(\mathrm{\&omega;t}+{\mathrm{\&theta;}}_{\mathrm{Lx}})\\ i_{\mathrm{Lx}}(\mathrm{\&omega;t}+\mathrm{\&pi;}/2+{\mathrm{\&theta;}}_{\mathrm{Lx}})\end{array}\right],x=a,b,c$ Phase, ω=2 π f

F is system fundamental frequency, θ _lxfor the phase angle of every phase load electric current; According to single-phase Instantaneous Power Theory, the instantaneous meritorious p of every phase _lxand idle q _lxfor:

p _Lx＝v _xα ⁱL _xα+v _xβ ⁱL _xβ,q _Lx＝-v _xβ ⁱL _xα+v _xα ⁱL _xβ

-q _lx/ 2 just can try to achieve the load reactive power of every phase by low pass filter .

(2) calculate every mutually required compensation minimum direct current side magnitude of voltage V _{dc_minx}

A) three-phase and four-line LC-VSI device:

For a fixing DC voltage = =0.5V _dcbe made as m=1 with modulation index m, R _vdcrepresent the different voltage levvl V of DC side _dcwith system phase voltage V _xvoltage ratio between effective value, can be expressed as:

phase;

LC-VSI device is for load reactive power compensation scope be:

$\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}(1-|{R_V}_{\mathrm{dc}}\left|\right)\right|\&le;{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}(1+|{R_V}_{\mathrm{dc}}\left|\right)|,x=a,b,c$ Phase;

Wherein for the reactive compensation power that LC passive leg (PF) provides, XC _cand XL _cfor capacitor C in passive leg (PF) _cand inductor L _cfundamental frequency Xc value and the anti-value of inductance, and XL _c=2 π fL _c;

By arranging ${Q_{\mathrm{Lx}}}_f\&ap;\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}(1-|{R_V}_{\mathrm{dc}}\left|\right)\right|\&ap;\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}(1+|{R_V}_{\mathrm{dc}}\left|\right)\right|,$ Can draw every mutually required compensating load reactive power minimum direct current side magnitude of voltage:

$V_{\mathrm{dc}\_\min x}=2\sqrt{2}{V}_x|1-\frac{{Q_{\mathrm{Lx}}}_f}{\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}\right|}|$

B) phase three-wire three LC-VSI device:

And for a fixing DC voltage V _dcbe made as m=1 with modulation index m, its every mutually required compensating load reactive power minimum direct current side magnitude of voltage expression formula be:

$V_{\mathrm{dc}\_\min x}=\frac{3\sqrt{2}}{2}{V}_x|1-\frac{{Q_{\mathrm{Lx}}}_f}{\left|{Q_{\mathrm{cx}}}_{f\_\mathrm{PF}}\right|}|$

The self adaptation that above two formulas can be applicable to three-phase and four-line and phase three-wire three LC-VSI device regulates DC voltage control algorithm, the reactive power Q providing when passive part as seen from this two formula _{cxf_PF}can full compensating load reactive power time, can obtain minimum direct current side magnitude of voltage is V _{dc_minx}=0.In addition, when the reactive power difference between them is larger, required DC voltage level requires higher, and vice versa.Whenever every phase load reactive power can calculate time, just can try to achieve every mutually corresponding required minimum direct current side magnitude of voltage V by above formula _{dc_minx}.

(3) self adaptation regulates inverter with reference to DC voltage horizontal determining method

By calculating every mutually required compensation minimum direct current side magnitude of voltage V _{dc_minx}, the minimum direct current side voltage V that LC-VSI device three-phase is required _{dc_min}can select to draw by following formula:

V _{dc_min}=max (V _{dc_mina}, V _{dc_minb}, V _{dc_minc}), x=a, b, c phase;

According to above formula, just can put into practice LC-VSI device in response under the idle scope of different loads, self adaptation regulates with reference to the horizontal V of DC voltage _dc ^*.

(4) inverter is determined with reference to DC voltage grade is

In fact, while being, become because of load reactive power, in order to reduce the impact that the DC voltage moment fluctuates on LC-VSI device compensation performance and effect, inverter is with reference to DC voltage V _dc ^*also be specially divided into n electric pressure (V _dc1, V _dc2... V _dcmax, V _dc1< V _dc2< V _dcmax, n=1,2 ... max) control, as shown in Figure 4.As the required minimum direct current side magnitude of voltage V of three-phase _{dc_min}lower than minimum voltage grade V _dc1, final reference DC voltage V _dc ^*=V _dc1; Otherwise, more next high voltage grade V _dc2, repeat this step, as shown in Figure 4.Then by the DC side voltage control method of mentioning below, just reach the function of automatic adjusting DC voltage level.

(5) calculate every reactive power compensation electric current needing mutually

Based on Clarke conversion, first the three-phase instantaneous system voltage v under a-b-c coordinate system _a, v _b, v _cand momentary load current i _la, i _lb, i _lctransform on the coordinate system of alpha-beta-0, draw α axle under the coordinate system of alpha-beta-0, β axle and 0 axle instantaneous system phase voltage v _α, v _β, v ₀and momentary load current i _{l α}, i _{l β}, i _l0;

According to Instantaneous Power Theory, instantaneous reactive q _{α β}for:

q _αβ＝-v _β ⁱL _α+v _α ⁱL _β

The needed offset current i of compensating reactive power under the coordinate system of alpha-beta-0 _{c α}, i _{c β}, i _c0can be calculated by following formula:

$i_{\mathrm{ca}}=i_{\mathrm{cap}}+i_{\mathrm{caq}}=0+\frac{-q{\mathrm{a\&beta;}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2},i_{\mathrm{c\&beta;}}=i_{\mathrm{c\&beta;p}}+i_{\mathrm{c\&beta;q}}=0+\frac{q{\mathrm{a\&beta;}}^{v}a}{v_{\mathrm{a\&beta;}}^2},i_{c0}=i_{c0p}=i_{L0}$

Wherein v _α ² _β=v _α ²+ v ² _β, i _{c α p}and i _{c α q}for the instantaneous meritorious and reactive power compensation electric current of α axle under the coordinate system of alpha-beta-0, i _{c β p}and i _{c β q}for the instantaneous meritorious and reactive power compensation electric current of β axle, i _c0pit is the instantaneous meritorious offset current of 0 axle;

Convert by anti-Clarke, just can obtain the needed every phase offset current i of compensating reactive power under a-b-c coordinate system _{ca_q}, i _{cb_q}, i _{cc_q}, i _{cx_q}=i _cxp+ i _cxq, x=a, b, c, as shown in Figure 4, wherein i _cxpand i _cxqfor every mutually instantaneous meritorious and reactive power compensation electric current under a-b-c coordinate system.

(6) DC voltage tracking adaptive is with reference to the control method of DC voltage value

And under the coordinate system of alpha-beta-0, control DC voltage V _dctrack reference value V _dc ^*every phase offset current also can be calculated by following formula:

$i_{\mathrm{ca}\_\mathrm{dc}}=i_{\mathrm{cap}\_\mathrm{dc}}+i_{\mathrm{caq}\_\mathrm{dc}}=\frac{\mathrm{\&Delta;p}{\mathrm{dc}}^{v}a}{v_{\mathrm{a\&beta;}}^2}+\frac{\mathrm{\&Delta;q}{\mathrm{dc}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2},$

$\begin{array}{c}{i}_{\mathrm{c\&beta;}\_\mathrm{dc}}=i_{\mathrm{c\&beta;p}\_\mathrm{dc}}+i_{\mathrm{c\&beta;q}\_\mathrm{dc}}=\frac{\mathrm{\&Delta;p}{\mathrm{dc}}^v\mathrm{\&beta;}}{v_{\mathrm{a\&beta;}}^2}+\frac{\mathrm{\&Delta;q}{\mathrm{dc}}^{v}a}{v_{\mathrm{a\&beta;}}^2},\\ i_{c0\_\mathrm{dc}}=0\end{array}$

Wherein Δ p _dc=-Δ q _dc=k _p(V _dc ^*-V _dc), k _pfor gain, i _{c α p_dc}and i _{c α q_dc}for the instantaneous meritorious and reactive power compensation electric current of α axle control DC voltage under the coordinate system of alpha-beta-0, i _{c β p_dc}and i _{c β q_dc}for the instantaneous meritorious and reactive power compensation electric current of β axle control DC voltage; Convert by anti-Clarke, just can obtain controlling the needed every phase offset current i of DC voltage under a-b-c coordinate system _{ca_dc}, i _{cb_dc}, i _{cc_dc}, i _{cx_dc}=i _{cxp_dc}+ i _{cxq_dc}, x=a, b, c, as shown in Figure 4, wherein i _{cxp_dc}and i _{cxq_dc}for the instantaneous meritorious and reactive power compensation electric current of every phase control DC voltage under a-b-c coordinate system.This DC voltage control method is also applicable to put into practice LC-VSI device starting DC capacitor oneself and charges to the function of reference voltage level.

(7) final reference offset current i _cx ^*definite

Instantaneous reactive is calculated to every reactive power compensation current i needing mutually _{cx_q}and control DC voltage tracking adaptive is with reference to the offset current i of DC voltage value _{cx_dc}adding up is exactly the final reference offset current i of LC-VSI device _cx ^*, utilize PWM method control inverter output offset current i _cxfollow the tracks of final reference current i _cx ^*thereby, carry out the control of LC-VSI device dynamic passive compensation and self adaptation direct current side voltage.

Self adaptation direct current side voltage LC-VSI device of the present invention is active can provide reactive compensation power in certain limit jointly with passive part, and in different load reactive power situations, LC-VSI device-adaptive regulates DC voltage level, thereby optimize and reduced loss and the noise of switch module, improve efficiency and the compensation effect of LC-VSI device.

An emulation example of the present invention below:

In this emulation example, self adaptation direct current side voltage LC-VSI device is connected in parallel in the three-phase four wire system that a line voltage is 380V, is used for compensating power, and the detailed maps of this bucking-out system as shown in Figure 5.LC-VSI device has been selected the voltage source inverter of separation structure in two level three brachium pontis DC capacitors, in different loads situation, LC-VSI device DC side voltage of converter can self adaptation regulate, and from loss and noise to reduce switch module, improves the efficiency of LC-VSI device.The detail parameters of this emulation example is as follows:

(1) system parameters:

System voltage v _x220V, system frequency 50Hz, system reactance L _s0.5mH;

(2) self adaptation LC-VSI apparatus system parameter:

Capacitor C _cand inductor L _c: 110 μ F, 10mH;

Inverter is with reference to DC voltage , be divided into Three Estate: V _dc1/ 2=40V, V _dc2/ 2=80V and V _dcmax/ 2=120V;

Inverter direct current capacitor C _dcfor 10mF;

(3) three-phase balancing load parameter:

Inductive load 1: resistance R _l1and inductance L _l1: 13.9 Ω, 50mH;

Inductive load 2: resistance R _l2and inductance L _l2: 36.0 Ω, 50mH;

Inductive load 3: resistance R _l3and inductance L _l3: 43.0 Ω, 50mH;

In this emulation example, self adaptation direct current side voltage LC-VSI device is in different loads reactive power required minimum direct current side electric pressure above ( , =40V, 80V, 120V) as shown in the table:

According to Fig. 4, when trying to achieve final reference current i _cx ^*after, utilize 7.5kHz carrier-based PWM method control inverter output offset current i _cxtrack reference current i _cx ^*.Under 6 kinds of different situation emulation, Figure 6 shows that self adaptation direct current side voltage LC-VSI device whole emulation dynamic compensation process and oscillogram (a) load-side reactive power thereof under different inductive loads , (b) DC voltage , , (c) mains side reactive power , (d) LC-VSI device injects reactive power .As seen from Figure 6, DC voltage , and LC-VSI device injects reactive power can regulate adaptively in response to different situations.In different loads situation, system side voltage v _xwith load-side current i _lxas Fig. 7, (as shown in a) – 9 (a), and LC-VSI device compensates rear system side voltage v to waveform _xwith system side current i _sxwaveform is if Fig. 7 is (as shown in b) – 9 (b).System side reactive power before and after compensation , fundamental frequency power factor DPF and current i _sxeffective value is as shown in the table:

From above result, in different loads situation, when dropping into after self adaptation direct current side voltage LC-VSI device, system side reactive power greatly reduced, system side fundamental frequency power factor DPF be improved to 0.999 or more than, and system side current i _sxeffective value is the aobvious minimizing that lands also.From above simulation result and Fig. 6 to Fig. 9, self adaptation direct current side voltage LC-VSI device (V _dcmax/ 2=120V) active and passive part can jointly provide reactive compensation power in certain limit.In addition, in contrast to the fixing DC voltage level of tradition device compensation result, as shown in figure 10, they roughly can obtain similar stable state reactive power compensation result, but self adaptation direct current side voltage LC-VSI device energy self adaptation regulates DC voltage, optimize and reduce loss and the noise of switch module, improve efficiency and the compensation effect of LC-VSI device.

Claims (6)

1. a LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation, is applicable to three-phase and four-line and phase three-wire three-electric power system processed, it is characterized in that, comprises the steps: first, by every phase load reactive power calculate the required minimum direct current side voltage of the every phase of LC-VSI device and three-phase, according to minimum direct current side voltage, self adaptation regulates with reference to the horizontal V of DC voltage _dc ^*; Then, calculate every reactive power compensation electric current needing mutually and control the offset current of DC voltage tracking adaptive with reference to DC voltage value by the instantaneous reactive of three-phase, above-mentioned two current summations are obtained to the final reference offset current i of LC-VSI device _cx ^*; Afterwards, utilize PWM method control inverter output offset current i _cxfollow the tracks of final reference current i _cx ^*, carry out the control of LC-VSI device dynamic passive compensation and self adaptation direct current side voltage;

The described LC-VSI device power-less compensation control method based on self adaptation adjusting DC voltage, calculates every phase load reactive power method specific as follows:

x=a, b, c phase, ω=2 π f;

Wherein v _xfor system phase voltage, i _lxfor load-side electric current, f is system fundamental frequency, θ _lxfor the phase angle of every phase load electric current; Utilize single-phase Instantaneous Power Theory, can be every phase v _xand i _lxtransform on orthogonal alpha-beta coordinate system, can obtain α axle and β axle instantaneous system phase voltage v under alpha-beta coordinate system _{x α}, v _{x β}and momentary load side current i _{lx α}, i _{lx β};

According to single-phase Instantaneous Power Theory, the instantaneous meritorious p of every phase _lxand idle q _lxfor:

p _Lx＝v _xαi _Lxα+v _xβi _Lxβ，q _Lx＝-v _xβi _Lxα+v _xαi _Lxβ

-q _lx/ 2 just can try to achieve the load reactive power of every phase by low pass filter

In above-mentioned control method, obtain every mutually required compensation minimum direct current side magnitude of voltage V _{dc_minx}method as follows:

A) three-phase and four-line LC-VSI device:

For a fixing DC voltage be made as m ≈ 1 with modulation index m, every mutually required compensating load reactive power minimum direct current side magnitude of voltage be:

Wherein V _xfor system phase voltage effective value, for the reactive compensation power that capacitive passive leg (PF) provides, X _ccand X _lcfor capacitor C in capacitive passive leg (PF) _cand inductor L _cfundamental frequency Xc value and the anti-value of inductance, and X _lc=2 π fL _c;

B) phase three-wire three LC-VSI device:

For a fixing DC voltage V _dcbe made as m ≈ 1 with modulation index m, its every mutually required compensating load reactive power minimum direct current side magnitude of voltage expression formula be:

2. the LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation according to claim 1, is characterized in that the minimum direct current side voltage V that LC-VSI device three-phase is required _{dc_min}draw by following formula:

V _{dc_min}=max (V _{dc_mina}, V _{dc_minb}, V _{dc_minc}), x=a, b, c phase.

3. the LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation according to claim 2, is characterized in that, described self adaptation regulates with reference to the horizontal V of DC voltage _dc ^*concrete grammar be: with reference to DC voltage V _dc ^*be divided into n electric pressure: V _dc1, V _dc2... V _dcmax, V _dc1< V _dc2< V _dcmax, n=1,2 ... Max, controls, as the required minimum direct current side magnitude of voltage V of three-phase _{dc_min}lower than minimum voltage grade V _dc1, final reference DC voltage V _dc ^*=V _dc1; Otherwise more next high voltage grade V _dc2, repeat this step.

4. the LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation according to claim 3, is characterized in that, the method for calculating every reactive power compensation electric current needing is mutually as follows:

Based on Clarke conversion, first the three-phase instantaneous system voltage v under a-b-c coordinate system _a, v _b, v _cand momentary load current i _la, i _lb, i _lctransform on the coordinate system of alpha-beta-0, draw α axle under the coordinate system of alpha-beta-0, β axle and 0 axle instantaneous system phase voltage v _α, v _β, v ₀and momentary load side current i _{l α}, i _{l β}, i _l0;

According to Instantaneous Power Theory, instantaneous reactive q under the coordinate system of alpha-beta-0 _{α β}for:

q _αβ＝-v _βi _Lα+v _αi _Lβ

The needed offset current i of compensating reactive power under the coordinate system of alpha-beta-0 _{c α}, i _{c β}, i _c0can be calculated by following formula:

i _c0＝i _c0p＝i _L0

Wherein i _{c α p}and i _{c α q}for the instantaneous meritorious and reactive power compensation electric current of α axle under the coordinate system of alpha-beta-0, i _{c β p}and i _{c β q}for the instantaneous meritorious and reactive power compensation electric current of β axle, i _c0pit is the instantaneous meritorious offset current of 0 axle; Afterwards, convert by anti-Clarke, obtain the needed every phase offset current i of compensating reactive power under a-b-c coordinate system _{ca_q}, i _{cb_q}, i _{cc_q}, i _{cx_q}=i _cxp+ i _cxq, x=a, b, c;

Wherein i _cxpand i _cxqfor the instantaneous meritorious and reactive power compensation electric current of every phase (x=a, b, c) under a-b-c coordinate system.

5. the LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation according to claim 4, is characterized in that, controls DC voltage V under the coordinate system of alpha-beta-0 _dctrack reference DC voltage V _dc ^*every phase offset current calculated by following formula:

i _{c0_dc}＝0

Wherein Δ p _dc=-Δ q _dc=k _p(V _dc ^*-V _dc), k _pfor gain, i _{c α p_dc}and i _{c α q_dc}for the instantaneous meritorious and reactive power compensation electric current of α axle control DC voltage under the coordinate system of alpha-beta-0, i _{c β p_dc}and i _{c β q_dc}for the instantaneous meritorious and reactive power compensation electric current of β axle control DC voltage; Convert by anti-Clarke, just can obtain controlling the needed every phase offset current i of DC voltage under a-b-c coordinate system _{ca_dc}, i _{cb_dc}, i _{cc_dc}, i _{cx_dc}=i _{cxp_dc}+ i _{cxq_dc}, x=a, b, c;

Wherein i _{cxp_dc}and i _{cxq_dc}controlling the instantaneous of DC voltage for every phase (x=a, b, c) under a-b-c coordinate system gains merit and reactive power compensation electric current.

6. the LC-VSI device power-less compensation control method that regulates DC voltage based on self adaptation according to claim 5, is characterized in that final reference offset current i _cx ^*definite method be: instantaneous reactive is calculated to every reactive power compensation current i needing mutually _{cx_q}and control DC voltage tracking adaptive is with reference to the offset current i of DC voltage value _{cx_dc}addition obtains the final reference offset current i of LC-VSI device _cx ^*.