CN103236800B - Novel topological structure voltage source type inverter and adjusting method - Google Patents

Abstract

The invention relates to a novel topological structure voltage source type inverter and an adjusting method. The structure is a star-like topological structure and is formed by connecting a three-phase bridge type inverter in series at a neutral point of cascaded inverters connected in a star shape. Compared with the conventional cascaded inverters connected in the star shape, the novel topological structure theoretically has a function of completely compensating negative sequence current; and compared with the conventional three-phase bridge type inverter, the novel topological structure can realize extended application under high voltage level without using a device cascade or MMC (Multilevel Converter) structure. In the novel topological structure, a direct current side of the three-phase bridge type inverter can be connected with a direct current network, energy storage equipment or a power grid through a current transformer; the inverter can be widely applied to the fields of flexible direct current power transmission, new energy connection, high voltage frequency converter and the like; and the application prospect of the voltage source type inverter in the corresponding field is expanded. The novel topological structure has good generalization performance based on mature unit cascade and three-phase inverter structure and control technology.

Description

A kind of new topological structure voltage source type inverter and control method

Technical field

The present invention relates to a kind of voltage source inverter and control method, especially relate to a kind of new topological structure voltage source type inverter and control method.

Background technology

Along with the development of electric power system, power quality problem more and more causes the attention of people.Based on the voltage source inverter of wholly-controled device, with its response speed and superior compensation performance fast, more and more applied in fields such as power system reactive power compensation, electric machine speed regulation, direct current transportation.

The main topological structure of current voltage source inverter has following two kinds:

The first is three-phase bridge structure.Three-phase bridge structure can realize the functions such as positive sequence reactive power compensation, negative-sequence current compensation, harmonic compensation and meritorious adjustment easily, but is limited to topological structure and device parameters, and its application also exists significant limitation.The most basic three-phase bridge structure is three-phase half-bridge structure, and it has structure and controls simple, design the advantages such as easy, but the harmonic content exported is relatively high, and is subject to the restriction of device voltage withstand class, be used for the occasion of low-pressure reactive compensation.In order to widen the range of application of three-phase bridge structure further, the technology such as the many level of diode clamp, the many level of striding capacitance, devices in series, MMC are successively there is.Wherein, the many level of diode clamp, the many level of striding capacitance are due to topological structure complexity, and level number and practical electric pressure have certain restriction; Devices in series and MMC technology solve the problem that inverter under high pressure runs well, and wherein MMC technology also can realize the function of many level simultaneously, but both control is more complicated, are only applied in minority engineering.

The second is series-connected structure.Series-connected structure is the cascaded structure based on single-phase full bridge module, on the basis not increasing individual unit design level, achieves inverter application under high pressure.This structure proposes in electrical converter, has become the main flow topological structure of mesohigh STATCOM, electrical converter at present.Series-connected structure can be divided into again the cascaded inverter of triangle connection and Y-connection according to different connected modes.Both substantially do not have difference on the idle compensation effect of positive sequence; In negative-sequence current compensation, triangular connection structure in theory can full remuneration unsymmetrical current, and Y-connection structure can only ensure uneven self stable operation lower, cannot accomplish to compensate completely; In harmonic compensation, the inverter of Y-connection is simpler in control.

Summary of the invention

Above-mentioned technical problem of the present invention is mainly solved by following technical proposals:

A new topological structure voltage source type inverter, is characterized in that, comprises based on the inverter of single-phase bridge cascade structure and the inverter based on three-phase bridge structure; The described inverter based on single-phase bridge cascade structure is three-phase, and three-phase cascaded inverter accesses three-phase bridge structure inverter simultaneously and connects into star structure at neutral point place; Or three-phase bridge structure inverter is positioned at the neutral point of three-phase cascaded inverter.

In above-mentioned a kind of new topological structure voltage source type inverter, the inverter of cascade structure each be made up of N number of H-bridge unit cascade, its DC side can only connect electric capacity or connect DC network or by current transformer incoming transport network.

In above-mentioned a kind of new topological structure voltage source type inverter, the inverter of described three-phase bridge structure adopts three-phase half-bridge structure formula inverter or three phase full bridge structural formula inverter or diode clamp many level block formula inverter or striding capacitance many level block formula inverter or devices in series structural formula inverter or block combiner many level block formula inverter.

In above-mentioned a kind of new topological structure voltage source type inverter, the DC side of the inverter of described three-phase bridge structure can only connect electric capacity or connect DC network or by current transformer incoming transport network.

The present invention is in conjunction with cascade connection type two kinds of inverters of three-phase bridge and Y-connection, a kind of new voltage source inverter topological structure of creationary proposition, this structure had both had the wide feature of three-phase bridge compensation range, had again the advantage that cascaded inverter applied voltage grade is high.The proposition of this topological structure, has enriched topological classification and the application prospect of voltage source inverter.

Based on a control method for new topological structure voltage source type inverter, it is characterized in that, comprise following control method:

Control method one: cascaded inverter and three-phase bridge inverter direct-flow side only connect DC capacitor, complete full remuneration that is idle and negative-sequence current, concrete steps are:

Step 1: under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, can be analyzed to positive sequence component with negative sequence component , inverter output current is used represent, can be analyzed to positive sequence idle component with negative sequence component ; Wherein: with access point place voltage phase place is identical, is used for the positive sequence reactive current of bucking-out system; be used for the negative-sequence current of bucking-out system; According to reactor characteristic, positive sequence voltage component advanced forward-order current component 90 °, phase place, negative sequence voltage components advanced negative-sequence current component 90 °, phase place;

Step 2: for cascaded inverter, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, be then decomposed into positive sequence component with negative sequence component ;

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, can be analyzed to positive sequence component equally with negative sequence component ;

Step 3: idle with in the realization of negative sequence component, need the main principle followed:

${\stackrel{\·}{U}}_{L+}={\stackrel{\·}{U}}_S-{\stackrel{\·}{U}}_{1+}-{\stackrel{\·}{U}}_{2+}$

${\stackrel{\·}{U}}_{L-}=-({\stackrel{\·}{U}}_{1-}+{\stackrel{\·}{U}}_{2-})$

Therefore, can according to the idle reasonable distribution realizing bridge architecture and cascade structure contravarianter voltage with negative phase-sequence instruction current and export, thus control device output current , to reach idle and full remuneration that is negative sequence component.

Control method two: cascaded inverter DC side only connects electric capacity, three-phase bridge type converter is by current transformer incoming transport electrical network, and now can realize meritorious and idle adjustment, concrete steps are:

Step 1: under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, can be analyzed to real component with idle component ; Wherein: with access point place voltage phase place is identical, is used for regulating idle output; be used for regulating meritorious output, output current is used represent, can be analyzed to real component with idle component , according to reactor characteristic, voltage real component leading current real component 90 °, phase place, voltage power-less component leading current idle component 90 °, phase place;

Step 2: for cascade structure, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, be then decomposed into real component with idle component ;

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, can be analyzed to real component equally with idle component ;

Step 3: meritorious with in the realization of idle component, need the main principle followed:

${\stackrel{\·}{U}}_{\mathrm{Lq}}={\stackrel{\·}{U}}_s-{\stackrel{\·}{U}}_{1q}-{\stackrel{\·}{U}}_{2q}$

${\stackrel{\·}{U}}_{\mathrm{Lp}}=-({\stackrel{\·}{U}}_{1p}+{\stackrel{\·}{U}}_{2p})$

Therefore, can according to the meritorious reasonable distribution realizing bridge architecture and cascade structure contravarianter voltage with idle instruction current and export, thus control device output current , to reach the adjustment of meritorious and idle component.

Therefore, tool of the present invention has the following advantages: 1. can realize the expanded application under voltage levels; 2. in new topological structure, three-phase bridge type converter DC side can be accessed by DC network, energy storage device or accesses electrical network by current transformer, the fields such as flexible DC power transmission, new forms of energy access, high voltage converter can be widely used in, widen the application prospect of voltage source inverter in corresponding field.New topological structure, based on the structure of unit cascaded, the three-phase inverter of maturation and control technology, has good generalization.

Accompanying drawing explanation

Fig. 1 is the structure chart of patent of the present invention.

Fig. 2 is the cascaded inverter structure chart of patent of the present invention.

Fig. 3 a is the three-phase bridge type converter structure chart (three-phase half-bridge structure formula inverter) of patent of the present invention.

Fig. 3 b is the three-phase bridge type converter structure chart (three phase full bridge structural formula inverter) of patent of the present invention.

Fig. 3 c is the three-phase bridge type converter structure chart (diode clamp many level block formula inverter) of patent of the present invention.

Fig. 3 d is the three-phase bridge type converter structure chart (striding capacitance many level block formula inverter) of patent of the present invention.

Fig. 3 e is the three-phase bridge type converter structure chart (devices in series structural formula inverter) of patent of the present invention.

Fig. 3 f is the three-phase bridge type converter structure chart (block combiner many level block formula inverter) of patent of the present invention.

Fig. 4 is that patent of the present invention is applied to the structure chart of gaining merit when regulating.

Fig. 5 is the fundamental diagram that patent of the present invention is applied to when fundamental wave reactive power and negative-sequence current compensate.

Fig. 6 is that patent of the present invention is applied to the fundamental diagram of gaining merit with during Reactive-power control.

Embodiment

Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is described in further detail.

Embodiment:

The structure and working principle of patent of the present invention is just described below by reference to the accompanying drawings.

1. the composition of new voltage source inverter topological structure.

See Fig. 1, be new voltage source inverter topology diagram, it is characterized in that: on the cascaded inverter basis of Y-connection, neutral point place access three-phase bridge type converter.Whole device is by connecting reactance access electrical network.For the ease of analysis afterwards, in each amount and reference directions thereof such as this regulation device electric current, line voltage, connection reactance voltage, device output voltages.This topological structure combines the advantage of series-connected structure and bridge architecture: when DC side only connects capacitor, possesses compensation ability that is idle, harmonics and negative sequence electric current, and can work under the condition that electric pressure is higher; During when DC side access DC network or by current transformer incoming transport network, the adjustment of active power can be realized.

2. the composition of cascaded inverter structure.

See Fig. 2, it is cascaded inverter structure chart.Its each formed by N number of basic H-bridge unit cascade, three-phase adopts star-like connected mode, the u that outlet a, b, c export with three-phase bridge type converter respectively _a, u _b, u _cthree-phase is connected.By certain modulation technique, its output harmonic wave content can be made less, the waveform that switching frequency is higher, but due to self structure restriction, it does not possess the ability of full remuneration negative-sequence current.

3. the composition of three-phase bridge type converter structure.

See Fig. 3 a to Fig. 3 f, it is the various forms of structure chart of three-phase bridge type converter.Wherein comprise the various structures forms such as three-phase half-bridge, three phase full bridge, the many level of diode clamp, the many level of striding capacitance, devices in series, MMC.Figure (3-a) is basic three-phase half-bridge inverter, is made up of three basic single-phase semi-bridge unit; Figure (3-b) is three-phase full-bridge inverter, is made up of three single-phase full bridge unit; Figure (3-c) is diode-clamped three-level inverter, mainly in basic three-phase bridge structure, adds diode clamping circuit, thus achieves the output of many level; Figure (3-d) is striding capacitance three-level inverter, mainly on each brachium pontis, adds capacitive branch, utilizes the discharge and recharge of electric capacity can realize many level and exports; Figure (3-e) is devices in series type structure, and wherein each unit is composed in series by several switching devices respectively, effectively can improve the capacity that device exports; Figure (3-f) is MMC type inverter, and its each elementary cell is single phase half bridge inverter, can improve device electric pressure and output level number.The u of often kind of structure output _a, u _b, u _ca, b, c three-phase that three-phase voltage exports with cascade structure is respectively connected, thus is built into new topological structure.

4. new voltage source inverter is applied to composition during meritorious adjustment.

See Fig. 4, for new voltage source inverter is applied to the composition of gaining merit when regulating.Cascaded inverter DC side only connects electric capacity, and three-phase bridge inverter is by current transformer incoming transport electrical network.Its feature is, can according to the flexible combination of cascade connection type module and three-phase bridge module, interconnected between the AC network realizing different electric pressure.

5. the idle realization compensated with negative-sequence current.

See Fig. 5, for new voltage source inverter is for the phasor diagram under stable state when fundamental wave reactive power and negative sequence compensation, take positive sequence component as reference frame, negative sequence component edge under this coordinate system rotates with twice rated frequency clockwise.

Without loss of generality, this phasor diagram obtains under following two assumed conditions:

(1) ignore device and circuit active loss, namely suppose all resistance R=0;

(2), after negative-sequence current full remuneration, in system voltage, only there is positive sequence component.

Under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, can be analyzed to positive sequence component with negative sequence component .Output current is used represent, can be analyzed to positive sequence component with negative sequence component .Wherein: with access point place voltage phase place is identical, is used for the positive sequence reactive current of bucking-out system; be used for the negative-sequence current of bucking-out system.According to reactor characteristic, positive sequence voltage component advanced forward-order current component 90 °, phase place, negative sequence voltage components advanced negative-sequence current component 90 °, phase place.

For cascade structure, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, can be analyzed to positive sequence component with negative sequence component .

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, can be analyzed to positive sequence component equally with negative sequence component .

Idle with in the realization of negative sequence component, need the main principle followed:

${\stackrel{\·}{U}}_{L+}={\stackrel{\·}{U}}_S-{\stackrel{\·}{U}}_{1+}-{\stackrel{\·}{U}}_{2+}$

${\stackrel{\·}{U}}_{L-}=-({\stackrel{\·}{U}}_{1-}+{\stackrel{\·}{U}}_{2-})$

Therefore, can according to the idle reasonable distribution realizing bridge architecture and cascade structure contravarianter voltage with negative phase-sequence instruction current and export, thus control device output current , to reach idle and full remuneration that is negative sequence component.

6. the realization of idle and meritorious adjustment.

See Fig. 6, for new voltage source inverter be used for fundamental wave reactive power with meritorious adjustment time, the phasor diagram under stable state.Topology is only considered three-phase bridge DC side is connected to the situation in merit source, cascade connection type unit DC side direct capacitance.

Without loss of generality, this phasor diagram obtains under following assumed condition:

(1) ignore device and circuit active loss, namely suppose all resistance R=0;

(2) negative sequence component is not contained in system.

Under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, can be analyzed to real component with idle component .Wherein: with access point place voltage phase place is identical, is used for regulating idle output; be used for regulating meritorious output.Output current is used represent, can be analyzed to real component with idle component .According to reactor characteristic, voltage real component leading current real component 90 °, phase place, voltage power-less component leading current idle component 90 °, phase place.By control λ angle, the flowing of meritorious energy between system just can be realized.

For cascade structure, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, can be analyzed to real component with idle component .

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, can be analyzed to real component equally with idle component .

Meritorious with in the realization of idle component, need the main principle followed:

${\stackrel{\·}{U}}_{\mathrm{Lq}}={\stackrel{\·}{U}}_s-{\stackrel{\·}{U}}_{1q}-{\stackrel{\·}{U}}_{2q}$

${\stackrel{\·}{U}}_{\mathrm{Lp}}=-({\stackrel{\·}{U}}_{1p}+{\stackrel{\·}{U}}_{2p})$

Therefore, can according to the meritorious reasonable distribution realizing bridge architecture and cascade structure contravarianter voltage with idle instruction current and export, thus control device output current , to reach the adjustment of meritorious and idle component.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Claims (1)

1. based on a control method for voltage source inverter, it is characterized in that, based on a kind of voltage source inverter, comprise based on the inverter of single-phase bridge cascade structure and the inverter based on three-phase bridge structure; The described inverter based on single-phase bridge cascade structure is three-phase, and three-phase cascaded inverter accesses three-phase bridge structure inverter simultaneously and connects into star structure at neutral point place; Or three-phase bridge structure inverter is positioned at the neutral point of three-phase cascaded inverter;

The inverter of cascade structure is often made up of N number of H-bridge unit cascade, and its DC side only connects electric capacity or connects DC network or by current transformer incoming transport network;

The inverter of described three-phase bridge structure adopts three-phase half-bridge structure formula inverter or three phase full bridge structural formula inverter or diode clamp many level block formula inverter or striding capacitance many level block formula inverter or devices in series structural formula inverter or block combiner many level block formula inverter;

The DC side of the inverter of described three-phase bridge structure only connects electric capacity or connects DC network or by current transformer incoming transport network;

Comprise following control method:

Control method one: cascaded inverter and three-phase bridge type converter DC side only connect DC capacitor, complete full remuneration that is idle and negative-sequence current, concrete steps are:

Step 1: under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, and be decomposed into positive sequence component with negative sequence component inverter output current is used represent, and be decomposed into positive sequence idle component with negative sequence component wherein: with access point place voltage phase place is identical, is used for the positive sequence reactive current of bucking-out system; be used for the negative-sequence current of bucking-out system; According to reactor characteristic, positive sequence voltage component advanced forward-order current component 90 °, phase place, negative sequence voltage components advanced negative-sequence current component 90 °, phase place;

Step 2: for cascaded inverter, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, be then decomposed into positive sequence component with negative sequence component

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, be decomposed into positive sequence component equally with negative sequence component

Step 3: idle with in the realization of negative sequence component, need the main principle followed:

${\stackrel{\·}{U}}_{L+}={\stackrel{\·}{U}}_S-{\stackrel{\·}{U}}_{1+}-{\stackrel{\·}{U}}_{2+}$

${\stackrel{\·}{U}}_{L-}=-({\stackrel{\·}{U}}_{1-}+{\stackrel{\·}{U}}_{2-})$

According to the idle reasonable distribution realizing bridge architecture and cascaded inverter voltage with negative phase-sequence instruction current and export, thus control device output current to reach idle and full remuneration that is negative sequence component;

Control method two: cascaded inverter DC side only connects electric capacity, three-phase bridge type converter is by current transformer incoming transport electrical network, and now can realize adjustment that is meritorious and idle component, concrete steps are:

Step 1: under stable state, the voltage drop that grid-connected inverters connects in reactance is used represent, and be decomposed into real component with idle component wherein: with access point place voltage phase place is identical, is used for regulating idle output; be used for regulating meritorious output, output current is used represent, and be decomposed into real component with idle component according to reactor characteristic, voltage real component leading current real component 90 °, phase place, voltage power-less component leading current idle component 90 °, phase place;

Step 2: for cascade structure, for ensureing that it can stable operation, its output voltage must and output current phase relation in 90 °, be then decomposed into real component with idle component

For three-phase bridge type converter, in the steady state, its output voltage with output current between phase relation adjustable, be decomposed into real component equally with idle component

Step 3: meritorious with in the realization of idle component, need the main principle followed:

${\stackrel{\·}{U}}_{\mathrm{Lq}}={\stackrel{\·}{U}}_s-{\stackrel{\·}{U}}_{1q}-{\stackrel{\·}{U}}_{2q}$

${\stackrel{\·}{U}}_{\mathrm{Lp}}=-({\stackrel{\·}{U}}_{1p}+{\stackrel{\·}{U}}_{2p})$

According to the meritorious reasonable distribution realizing bridge architecture and cascade structure contravarianter voltage with idle instruction current and export, thus control device output current to reach the adjustment of meritorious and idle component.