CN103441696A - Cascade current transformer DC side self-voltage-stabilizing method - Google Patents

Abstract

The invention discloses a cascade current transformer DC side self-voltage-stabilizing method. The method involves performing feedback control over the voltage at the DC side of each H bridge and then performing carrier wave rotation on the basis of carrier wave phase shift so that self-voltage-stabilization can be realized under the condition that no auxiliary circuits and no other system extra expenditures are additionally added, and the voltage at the DC side of a cascade current transformer unit can be balanced.

Description

A kind of cascade converter DC side is from method for stabilizing voltage

Technical field

The present invention relates to a kind of cascade structure current transformer mutually in DC voltage from method for stabilizing voltage, be intended to not increase in the situation of any DC side auxiliary circuit and carry out from voltage stabilizing, guarantee the balance of unit DC voltage simultaneously.

Background technology

In the application of cascade converter, due to the imbalance of series loss and shunt loss, can cause DC voltage inconsistent in current transformer mutually.Existing method or be equipped with independent power supply circuits to each DC side and carry out voltage stabilizing; Or, at DC side connecting resistance and gate-controlled switch device, carry out the balance of voltage by the loss of resistance; Or carry out balancing energy by DC bus or public exchange bus.First method has increased extra circuit, has not only increased volume and the complexity of whole converter system, has improved cost simultaneously.Second method has increased the loss of device, has reduced the efficiency of system.The third method is identical with first method, has increased volume and the installation cost of system, makes the mobile of system capacity become complicated simultaneously.

Summary of the invention

The invention provides a kind of cascade converter DC side from method for stabilizing voltage, in the situation that do not increase auxiliary circuit and the other system extra expenses are carried out from voltage stabilizing, realize the balance of cascade converter unit DC voltage.

The technical scheme that realizes above-mentioned purpose is:

A kind of cascade converter DC side is from method for stabilizing voltage, described cascade converter every unit cascaded by N H bridge, and N >=2 and N are integer, and the DC voltage of each H bridge is carried out to FEEDBACK CONTROL, then on the basis of phase-shifting carrier wave, carry out the carrier wave rotation.

Above-mentioned cascade converter DC side is from method for stabilizing voltage, wherein, the DC voltage of each H bridge carried out to FEEDBACK CONTROL, and the A of take m H bridge mutually is example, and 1≤m≤N and m are integer, specifically comprise:

Under the effect of the mean value control ring of current regulator and all DC voltages, obtain the controlled quentity controlled variable U of A phase _a;

A is the DC voltage V of m H bridge mutually _am-dcthrough this H bridge DC side voltage control loop, the feedback quantity U of controlled ring _adcm;

According to formula:

obtain the A controlled quentity controlled variable U of m H bridge unit mutually _am, through the extra pulse transmission, m H bridge of A phase realized to FEEDBACK CONTROL.

Above-mentioned cascade converter DC side is from method for stabilizing voltage, wherein, under the effect of the mean value control ring of current regulator and all DC voltages, obtains the controlled quentity controlled variable U of A phase _a, specifically comprise:

According to formula:

${\stackrel{\‾}{v}}_{\mathrm{dc}}=\frac{V_{a1-\mathrm{dc}}+V_{a2-\mathrm{dc}}+...+V_{\mathrm{aN}-\mathrm{dc}}+V_{b1-\mathrm{dc}}+V_{b2-\mathrm{dc}}+...+V_{\mathrm{bN}-\mathrm{dc}}+V_{c1-\mathrm{dc}}+V_{c2-\mathrm{dc}}+...+V_{\mathrm{cN}-\mathrm{dc}}}{N*3}$

Wherein, V _a1-dc, V _a2-dc, V _aN-dcbe respectively the A DC voltage of first H bridge, second H bridge and N H bridge mutually; V _b1-dc, V _b2-dc, V _bN-dcbe respectively the B DC voltage of first H bridge, second H bridge and N H bridge mutually; V _c1-dc, V _c2-dc, V _cN-dcbe respectively the C DC voltage of first H bridge, second H bridge and N H bridge mutually;

Obtain the mean value of all H bridges unit DC voltage

through the mean value control ring of described all DC voltages, controlled amount U _dc;

Offset current i _ca, i _cb, i _ccbe compensated the dq component i of electric current through Park Transformation _d, i _q; Dq component i _d, i _qwith controlled quentity controlled variable U _dcthrough described current regulator, obtain the dq component U of reference voltage _d, U _q;

Line voltage v _sa, v _sb, v _scobtain the dq component v of line voltage through Park Transformation _d, v _q;

U _dwith v _dand U _qwith v _qdo with afterwards respectively, then carry out the controlled quentity controlled variable U that the Parker inverse transformation obtains A phase, B phase, C phase _a, U _b, U _c.

Above-mentioned cascade converter DC side, from method for stabilizing voltage, wherein, is carried out the carrier wave rotation on the basis of phase-shifting carrier wave, specifically comprises:

Each H bridge respectively corresponding carrier wave zero hour of each phase, that is: h H bridge correspondence h carrier wave, 1≤h≤N and h are integer;

Through certain modulating wave cycle, carrier wave carries out a rotation, that is: the carrier transformation of h H bridge is the h+1 carrier wave, and the carrier transformation of N H bridge is No. 1 carrier wave.

The invention has the beneficial effects as follows: the present invention controls on basis and adopts the control on extra software in tradition, carry out FEEDBACK CONTROL by the DC voltage to each H bridge, and carry out the carrier wave rotation on the basis of phase-shifting carrier wave, realization in the situation that do not increase the system extra expenses and carry out from voltage stabilizing, guarantees the balance of cascade converter unit DC voltage.

The accompanying drawing explanation

Fig. 1 is cascade converter system construction drawing while being applied to compensating reactive power and harmonic wave;

Fig. 2 is the FEEDBACK CONTROL block diagram of each H bridge DC side voltage in the present invention;

The carrier wave figure that when Fig. 3 is phase-shifting carrier wave, each H bridge is corresponding;

The carrier wave figure that when Fig. 4 is the carrier wave rotation, each H bridge is corresponding.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

Current transformer adopts conventional method to carry out DC side when voltage stabilizing, and itself all can have the mean value control ring of current regulator and all DC voltages.Current regulator is controlled the output current of current transformer, and the mean value control ring of all DC voltages can be guaranteed the stable of total DC side average voltage, thereby current transformer adopts phase-shifting carrier wave to be modulated more, guarantees that the switch subfrequency of output current is higher.But cascade converter forms (every unit cascaded by N H bridge, N >=2 and N are integer) by the discrepant H bridge of a lot of losses unit, so the DC voltage of each H bridge unit is inconsistent, thereby causes system normally not move.Original method all need connect in the DC side of each H bridge extra circuit.Provided by the invention from method for stabilizing voltage only on the original basis of controlling, adopt the control on extra software, comprise altogether two main points: be at first that DC voltage for each H bridge carries out FEEDBACK CONTROL; Next is the form that changes carrier wave, carries out the carrier wave rotation on the basis of phase-shifting carrier wave.

Refer to Fig. 1, system construction drawing while for cascade converter, being applied to compensating reactive power and harmonic wave, in the present embodiment, three the H bridges of every phase of take are unit cascaded is example, in Fig. 1, v _sa, v _sb, v _scfor line voltage; i _ca, i _cb, i _ccfor offset current; V _c1-dc, V _c2-dc, V _c3-dcbe respectively the C DC voltage of first H bridge, second H bridge and the 3rd H bridge mutually, other phase H bridge unit DC voltage is analogized.

DC voltage to each H bridge carries out FEEDBACK CONTROL, as shown in Figure 2, specifically comprises:

1), under the effect of the mean value control ring of current regulator and all DC voltages, obtain A phase, B phase, C controlled quentity controlled variable U separately mutually _a, U _b, U _c, specifically comprise:

According to formula:

${\stackrel{\‾}{v}}_{\mathrm{dc}}=\frac{V_{a1-\mathrm{dc}}+V_{a2-\mathrm{dc}}+...+V_{\mathrm{aN}-\mathrm{dc}}+V_{b1-\mathrm{dc}}+V_{b2-\mathrm{dc}}+...+V_{\mathrm{bN}-\mathrm{dc}}+V_{c1-\mathrm{dc}}+V_{c2-\mathrm{dc}}+...+V_{\mathrm{cN}-\mathrm{dc}}}{N*3}$

Obtain the mean value of all H bridges unit DC voltage

through the mean value control ring of all DC voltages, controlled amount U _dc, in Fig. 2,

for DC side average voltage set-point; In formula, V _a1-dc, V _a2-dc, V _aN-dcbe respectively the A DC voltage of first H bridge, second H bridge and N H bridge mutually; V _b1-dc, V _b2-dc, V _bN-dcbe respectively the B DC voltage of first H bridge, second H bridge and N H bridge mutually; V _c1-dc, V _c2-dc, V _cN-dcbe respectively the C DC voltage of first H bridge, second H bridge and N H bridge mutually; In the present embodiment, N is 3;

Offset current i _ca, i _cb, i _ccbe compensated the dq component i of electric current through Park Transformation _d, i _q; Dq component i _d, i _qwith controlled quentity controlled variable U _dcthrough current regulator, obtain the dq component U of reference voltage _d, U _q, in Fig. 2, i _d ^*, i _q ^*for the given electric current of electric current loop;

Line voltage v _sa, v _sb, v _scobtain the dq component v of line voltage through Park Transformation _d, v _q;

U _dwith v _ddo and, U _qwith v _qdo with afterwards, then carry out the controlled quentity controlled variable U that the Parker inverse transformation obtains A phase, B phase, C phase _a, U _b, U _c.

2) take A phase, B phase, C mutually separately m H bridge be example, 1≤m≤N and m are integer; A phase, B phase, C phase be the DC voltage V of m H bridge separately _am-dc, V _bm-dc, V _cm-dcthrough corresponding H bridge DC side voltage control loop separately, obtain the feedback quantity U of corresponding control ring _adcm, U _bdcm, U _cdcm,

for DC side average voltage set-point;

3) according to formula: obtain the A controlled quentity controlled variable U of m H bridge unit mutually _am, through the extra pulse transmission, m H bridge of A phase realized to FEEDBACK CONTROL; In like manner, obtain B phase, the C controlled quentity controlled variable U of m H bridge unit mutually _bm, U _cm, by the pulse transmission, B phase, m H bridge of C phase are realized to FEEDBACK CONTROL.

Therefore, the controlled quentity controlled variable of known each H bridge is comprised of two parts, and the A of take m H bridge mutually is example:

$U_{\mathrm{am}}=U_{\mathrm{adcm}}\left(1\right)+\frac{U_a}{N}\left(2\right)$

For the controlled quentity controlled variable of same interior different H bridges mutually, their (2) part is all identical, but the amount of (1) part is different amount, the different controlled quentity controlled variable of the first part has played regulating action for the consistency of DC voltage just.

If but only adopt top control, the parameter of H bridge DC side voltage control loop need change along with the variation of current transformer power output, when output reactive power is less than 10% full-load power, system may occur unstable, adopt the carrier wave rotation to address this problem, now the control ring parameter only need to get final product for a fixed value.When only adopting phase-shifting carrier wave, h H bridge of each phase will adopt same carrier wave, become the h carrier wave herein, and 1≤h≤N and h are integer.The frequency of all carrier waves, peak value and shape are all identical, but the h carrier wave will postpone than the h-1 carrier wave angle.When adopting the carrier wave rotation, the carrier wave of each H bridge will be unfixed.

Carry out the carrier wave rotation on the basis of phase-shifting carrier wave, specifically comprise:

Each H bridge respectively corresponding carrier wave zero hour of each phase, that is: h the corresponding h carrier wave of H bridge;

Through certain modulating wave cycle, carrier wave carries out a rotation, that is: the carrier transformation of h H bridge is the h+1 carrier wave, and the carrier transformation of N H bridge is No. 1 carrier wave.In the present embodiment, N is 3, carrier wave corresponding to each H bridge during phase-shifting carrier wave as shown in Figure 3; And carrier wave corresponding to each H bridge during the carrier wave rotation shown in Fig. 4; During beginning, the carrier wave of the 1st H bridge of each phase is No. 1 carrier wave, and the carrier wave of the 2nd H bridge is No. 2 carrier waves, and the carrier wave of the 3rd H bridge is No. 2 carrier waves; Through certain modulating wave week after date, the carrier wave of the 1st H bridge of each phase is No. 2 carrier waves, and the carrier wave of the 2nd H bridge is No. 3 carrier waves, and the carrier wave of the 3rd H bridge is No. 1 carrier wave; Pass through certain modulating wave week after date, the carrier wave of the 1st H bridge of each phase is No. 3 carrier waves again, and the carrier wave of the 2nd H bridge is No. 1 carrier wave, and the carrier wave of the 3rd H bridge is No. 2 carrier waves; In the modulating wave cycle that every process is certain like this, carrier wave just carries out a rotation.In Fig. 3, Fig. 4, y means the amplitude of carrier wave, and t means the time.

Above embodiment is used for illustrative purposes only, but not limitation of the present invention, person skilled in the relevant technique, without departing from the spirit and scope of the present invention, can also make various conversion or modification, therefore all technical schemes that are equal to also should belong to category of the present invention, should be limited by each claim.

Claims (4)

1. a cascade converter DC side is from method for stabilizing voltage, described cascade converter every unit cascaded by N H bridge, N >=2 and N are integer, it is characterized in that, DC voltage to each H bridge carries out FEEDBACK CONTROL, then on the basis of phase-shifting carrier wave, carries out the carrier wave rotation.

2. cascade converter DC side according to claim 1, from method for stabilizing voltage, is characterized in that, the DC voltage of each H bridge is carried out to FEEDBACK CONTROL, and the A of take m H bridge mutually is example, and 1≤m≤N and m are integer, specifically comprise:

Under the effect of the mean value control ring of current regulator and all DC voltages, obtain the controlled quentity controlled variable U of A phase _a;

A is the DC voltage V of m H bridge mutually _am-dcthrough this H bridge DC side voltage control loop, the feedback quantity U of controlled ring _adcm;

According to formula: obtain the A controlled quentity controlled variable U of m H bridge unit mutually _am, through the extra pulse transmission, m H bridge of A phase realized to FEEDBACK CONTROL.

3. cascade converter DC side according to claim 2, from method for stabilizing voltage, is characterized in that, under the effect of the mean value control ring of current regulator and all DC voltages, obtains the controlled quentity controlled variable U of A phase _a, specifically comprise:

According to formula:

${\stackrel{\‾}{v}}_{\mathrm{dc}}=\frac{V_{a1-\mathrm{dc}}+V_{a2-\mathrm{dc}}+...+V_{\mathrm{aN}-\mathrm{dc}}+V_{b1-\mathrm{dc}}+V_{b2-\mathrm{dc}}+...+V_{\mathrm{bN}-\mathrm{dc}}+V_{c1-\mathrm{dc}}+V_{c2-\mathrm{dc}}+...+V_{\mathrm{cN}-\mathrm{dc}}}{N*3}$

Wherein, V _a1-dc, V _a2-dc, V _aN-dcbe respectively the A DC voltage of first H bridge, second H bridge and N H bridge mutually; V _b1-dc, V _b2-dc, V _bN-dcbe respectively the B DC voltage of first H bridge, second H bridge and N H bridge mutually; V _c1-dc, V _c2-dc, V _cN-dcbe respectively the C DC voltage of first H bridge, second H bridge and N H bridge mutually;

Obtain the mean value of all H bridges unit DC voltage

through the mean value control ring of described all DC voltages, controlled amount U _dc;

Offset current i _ca, i _cb, i _ccbe compensated the dq component i of electric current through Park Transformation _d, i _q; Dq component i _d, i _qwith controlled quentity controlled variable U _dcthrough described current regulator, obtain the dq component U of reference voltage _d, U _q;

Line voltage v _sa, v _sb, v _scobtain the dq component v of line voltage through Park Transformation _d, v _q;

U _dwith v _dand U _qwith v _qdo with afterwards respectively, then carry out the controlled quentity controlled variable U that the Parker inverse transformation obtains A phase, B phase, C phase _a, U _b, U _c.

According to claim 1 or 2 or 3 described cascade converter DC side from method for stabilizing voltage, it is characterized in that, carry out the carrier wave rotation on the basis of phase-shifting carrier wave, specifically comprise:

Each H bridge respectively corresponding carrier wave zero hour of each phase, that is: h H bridge correspondence h carrier wave, 1≤h≤N and h are integer;

Through certain modulating wave cycle, carrier wave carries out a rotation, that is: the carrier transformation of h H bridge is the h+1 carrier wave, and the carrier transformation of N H bridge is No. 1 carrier wave.

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