CN202917979U - Chained-mode SVG control device - Google Patents
Chained-mode SVG control device Download PDFInfo
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- CN202917979U CN202917979U CN2012205030495U CN201220503049U CN202917979U CN 202917979 U CN202917979 U CN 202917979U CN 2012205030495 U CN2012205030495 U CN 2012205030495U CN 201220503049 U CN201220503049 U CN 201220503049U CN 202917979 U CN202917979 U CN 202917979U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/10—Flexible AC transmission systems [FACTS]
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Abstract
The utility model relates to a chained-mode SVG control device. The chained-mode SVG control device includes an H-bridge multi-connection-type multilevel inverter, a sampling circuit, an automatic bypass circuit and a pulse width modulation circuit; the multilevel inverter is formed by three phases of H-bridge power modules which are connected with a three-phase power supply, wherein each phase of H-bridge power modules are additionally provided with at least one spare H-bridge unit circuit; and the pulse width modulation circuit which is connected with a phase-splitting current independent control circuit which controls carrier triangular wave phase-shifted SPWM adopted among each H-bridge unit circuit according to the modulation ratio M and phase angle of sinusoidal modulation waves. According to the chained-type SVG control device of the utility model, each phase of H-bridge power modules are additionally provided with at least one spare H-bridge unit circuit, such that when one H-bridge power module is damaged, the fault module can be automatically bypassed, and therefore, downtime maintenance is not required.
Description
Technical Field
The utility model relates to an electric power system electric energy quality field, in particular to chain SVG controlling means.
Background
With the rapid development of the power industry, the problem of safety and stability of the power system is increasingly highlighted. The Static Var Generator (SVG) is used as a new important element in a flexible alternating current transmission system and a customized power system, can enhance the control capability of the power system, has small volume and high regulation speed, and has great advantages in the aspects of regulating system voltage, correcting power factors, balancing load, filtering harmonic waves and the like.
In the chained SVG device, an H-bridge power module is the most important component and is also the most prone to failure. In the prior art, when a certain power module breaks down, a worker usually needs to stop the machine for maintenance, at this time, the whole circuit must be in a power-off state, certain inconvenience is brought to production and life, or the fault is not found in time to cause the damage of the whole circuit, so that the power supply can not be cut off for maintenance, and the automatic cutting of the faulty H-bridge unit circuit is a technical problem in the field.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is to provide a be suitable for automatic bypass trouble H bridge unit circuit to guarantee the chain SVG controlling means of many level inverter of H electric bridge multiplex type normal work.
In order to solve the technical problem, the utility model provides a chain SVG controlling means, include:
the H-bridge multi-connected multi-level inverter comprises three-phase H-bridge power modules connected to a three-phase power supply, wherein at least one standby H-bridge unit circuit is additionally arranged in each phase of H-bridge power module consisting of a plurality of H-bridge unit circuits; an automatic bypass circuit provided at the output terminal of each H-bridge unit circuit,
a sampling circuit connected to the three-phase power supply and adapted to track a voltage phase of the three-phase power supply;
a modulation ratio M and a phase angle which are connected with the sampling circuit and are suitable for outputting a sine modulation wave required by the pulse width modulation circuit according to the voltage phase of the three-phase power supply
The split-phase current independent control circuit;
the modulation ratio M and the phase angle of the sine modulation wave are used for regulating the phase of the sine modulation wave
And the pulse width modulation circuit is used for controlling carrier triangular wave phase-shifting SPWM adopted among the H bridge unit circuits.
The utility model has the advantages of it is following: (1) at least one standby H bridge unit circuit is additionally arranged in each phase of H bridge power module, so that when the H bridge power module is damaged, a fault module is automatically bypassed without shutdown maintenance; (2) the pulse width modulation circuit adjusts the modulation wave of the damaged one-phase H-bridge power module, thereby effectively avoiding the generation of harmonic waves; (3) the problem of compensation of unbalanced output of the three-phase power supply is solved through independent control of split-phase current.
Drawings
In order that the present invention may be more readily and clearly understood, reference will now be made in detail to the present invention, examples of which are illustrated in the accompanying drawings
Fig. 1 is a block diagram of a chain SVG control apparatus using a redundant control strategy according to the present invention;
fig. 2 is a circuit diagram of an H-bridge multiple multi-level inverter of the present invention;
fig. 3 is a structural diagram of an H-bridge unit circuit according to the present invention.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings and embodiments:
as shown in fig. 1 to 3, a chained SVG control apparatus includes:
the H-bridge multi-connected multi-level inverter (also called chained SVG) is composed of three-phase H-bridge power modules connected to a three-phase power supply, wherein at least one standby H-bridge unit circuit is additionally arranged in each phase of H-bridge power module composed of a plurality of H-bridge unit circuits;
the sampling circuit is connected with the three-phase power supply and is suitable for acquiring the amplitude, the period and the phase of the voltage and the current of the three-phase power supply;
a modulation ratio M and a phase angle of a sine modulation wave connected with the sampling circuit and suitable for tracking the voltage phase of the three-phase power supply to output the sine modulation wave required by the pulse width modulation circuitThe split-phase current independent control circuit;
the automatic bypass circuit is arranged at the output end of each H bridge unit circuit and bypasses one H bridge unit circuit when the H bridge unit circuit is damaged;
a pulse width modulation circuit connected with the split-phase current independent control circuit and used for modulating the phase angle according to the modulation ratio M and the phase angle of the sine modulation wave
Controlling carrier triangular wave phase-shifting SPWM adopted among the H bridge unit circuits; namely, after the damaged H-bridge unit circuit bypasses, the pulse width modulation circuit is adapted to change the carrier frequency of the carrier triangular wave phase-shifted SPWM of the one-phase H-bridge power module in which the damaged H-bridge unit circuit is located, on the basis of keeping the sampling period of the sampling circuit unchanged, so as to obtain the pulse modulation waveform of the carrier triangular wave phase-shifted SPWM corresponding to the number of the remaining H-bridge unit circuits in the one-phase H-bridge power module.
A pulse width modulation circuit relates to an SPWM (sinusoidal pulse width modulation) method, which is characterized in that a sine wave is used as a modulation wave, a triangular wave with the frequency F times that of the sine modulation wave is used as a carrier wave to carry out waveform comparison, and a group of amplitudes generated by the waveform comparison are equal, and the width of the triangular wave is in direct proportion to a rectangular pulse train of the sine modulation wave to be equivalent to the sine wave, so that the on-off of a switching device (namely the switching device in a multilevel inverter) is controlled.
The utility model discloses a carrier wave triangular wave moves the SPWM control of looks phase and the hybrid control algorithm of carrier wave triangular wave range upon range of formula SPWM control: on the whole, carrier triangular wave phase-shifting SPWM control is adopted among all H-bridge unit circuits, and a stacked SPWM control method is adopted for a single H-bridge unit circuit.
The carrier triangular wave phase-shifting SPWM control method is to compare N carrier triangular waves with different phase and identical frequency and amplitude with one sinusoidal modulation wave for N H bridge unit circuits to generate N groups of SPWM control pulse waveforms to control N H bridges respectively, so that each H bridge unit circuit outputs SPWM voltage waveforms with identical fundamental voltage, and the SPWM voltage waveforms output by the N H bridge unit circuits are superposed to synthesize SPWM multilevel voltage waveforms.
The initial phase angles of the N carrier triangular waves should be sequentially shifted by an angle, which is the same as that of the bipolar carrier triangular wave if the bipolar carrier triangular wave is adopted
(ii) a If the single-polar carrier triangular wave is used, the angle is
。
The carrier triangular wave cascade type SPWM control method is an SPWM modulation method which applies a multi-level inverter earlier. The carrier triangular wave stacked SPWM modulation method can be divided into two methods, namely a single-layer stacked SPWM modulation method and a multilayer stacked SPWM modulation method, and the two methods can achieve the technical effect of the patent.
The carrier triangular wave single-layer stacked SPWM modulation method can be further divided into a carrier triangular wave reverse phase single-layer stacked SPWM modulation method (the phases of two carrier triangular waves are opposite) and a carrier triangular wave in-phase single-layer stacked SPWM modulation method (the phases of two carrier triangular waves are the same) according to the phase relationship of the two triangular carriers. The carrier wave triangular wave reverse phase single layer stack SPWM modulation method and carrier wave triangular wave homophase single layer stack SPWM modulation method do not have the difference of good or bad in these two modulation methods, the utility model discloses a carrier wave triangular wave homophase single layer stack SPWM modulation method.
In the carrier triangular wave in-phase single-layer laminated SPWM modulation method, two carrier triangular waves
And
are the same. Wherein
And
carrier triangular waves at the upper and lower layers of the horizontal axis,
is a sine modulation wave. Comparing sine wave with triangular wave
The part larger than the triangular wave will generate output SPWM pulse in the sine wave
A portion smaller than the triangular wave generates a zero pulse of the output voltage. Due to the fact that
Andare in phase, i.e. are
And
asymmetric sitting onThe horizontal axis indicates that the positive half cycle and the negative half cycle of the waveform of the output voltage SPWM generated by comparing the sine wave with the triangular wave are different.
Any one H-bridge unit circuit is taken for research and analyzed from the power perspective. Wherein,
is the output voltage of the H-bridge cell circuit,
for the purpose of the phase current,
for the included angle between the output voltage and the phase current, the active power absorbed by the H-bridge unit circuit is:
therefore, the active power absorbed by the H bridge can be changed by changing the output voltage of the H bridge unit circuit, the phase current and the included angle between the output voltage and the phase current. Because the magnitude and direction of the phase current Is are fixed, only the magnitude and direction of the output voltage of the H-bridge unit circuit, i.e. the modulation ratio M and the phase angle corresponding to the output of the pulse width modulation circuit, can be changed
。
The control strategy of the chained SVG adopts a layered control structure: the upper layer control mainly determines total active power and reactive power, and the lower layer control mainly adjusts reasonable distribution of active power among all the phase H bridges to ensure the balance of capacitance and voltage on the direct current side. The utility model discloses the method of upper control adopts split-phase current independent control, calculates the modulation ratio and the phase angle of expected modulation wave, and the error quantization of each bridge direct current side voltage is the sine function stack on this H bridge unit circuit's modulation wave, finely tunes the modulation wave phase place of each H bridge unit circuit, adjusts the distribution of active power between each H bridge unit circuit.
The principle of trimming phase difference to realize capacitor voltage balance, wherein USVGThe voltage of the direct current side capacitor is 90 degrees because the phase current lags or leads the SVG output voltage, and the charging amount of the direct current capacitor of each H bridge in a half period is 0; in the second cycle, fine-tuning it
At this time, the capacity charge increases. It can be seen that through the control
The charging or discharging of the capacitor can be controlled when
>When 0, the capacitor is charged and the voltage rises; on the contrary, when
<At 0, the capacitor discharges and the voltage drops. Therefore, the voltage on the direct current side of each H bridge can be passed through
The fine adjustment of the balance control is reasonably adjusted to achieve balance control.
The three-phase direct current side of the chained SVG has no coupling relation, so that split-phase control can be realized, three-phase systems are respectively compensated, and a good compensation effect can be achieved for a balanced system and an unbalanced system. In the control strategy provided in the previous section, the upper-layer control adopts current state complete decoupling control, the transient response is fast, the stability is good, but the controller only considers the condition of three-phase balance during design, and the problem of unbalance of a three-phase system is not considered. The quality of the power grid has been investigated to show that the voltage of the power grid is more or less asymmetrical in phase or amplitude, i.e. in practice, three-phase systems are mostly unbalanced.
The automatic bypass circuit adopts an automatic bypass technology, and the automatic bypass technology is to directly bypass the alternating current side of the fault power module, so that the fault module is separated from the device. Automatic bypass is achieved by providing a bypass mechanism on the output side of each power cell module.
The output end of each H bridge unit circuit is provided with a relay, and the fault H bridge unit circuit is separated from the phase H bridge power module by controlling the normally open state and the normally closed state; the output end of each H-bridge unit circuit is connected to the rectifier bridge formed by two pairs of diodes, so that the thyristor is always in forward voltage drop. When the monitoring system detects an internal fault of the power module, the IGBT pulse is immediately blocked, and the thyristor is triggered to be conducted, so that bypass separation is realized; or a triac may be used.
When a faulty H bridge unit circuit in a certain phase H bridge power module is bypassed, if the pulse transmission of the sinusoidal modulation signal output by the pulse width modulation circuit is transmitted according to normal operation, the output of the chained SVG control device is only superposed by the output voltages of N H bridge unit circuits, and the harmonic content is increased. Therefore, for the remaining N non-faulty H-bridge unit circuits, the modulation strategy needs to be adjusted accordingly.
Because the carrier triangular wave laminated SPWM only acts in a single H-bridge unit circuit, the fault module separation has no influence on the modulation of the carrier triangular wave laminated SPWM and only influences the carrier triangular wave phase-shifting SPWM. Therefore, for the convenience of analysis, only the carrier triangular wave phase shift SPWM is analyzed. When N + 1H bridge unit circuits are arranged in series, the carrier frequency of the chained SVG control device is 1/TcWith a sampling period of TsSampling period T when carrier is unipolars = Tc /[2(N+1)]. Two common adjusting methods after the circuit of the fault H bridge unit is separated are given below.
The first method comprises the following steps: t iscInvariable, TsVariations in
In order to simplify analysis, before selecting a fault, if the number of the multi-level inverters is n +1=6, the sampling period T of each phase H-bridge power module is set to bes=Tc/12 at 0/6Ts、Ts/7Ts、2Ts/8Ts、3Ts/9Ts、4Ts/10Ts、5Ts/11TsThe modulated wave is sampled at one time and compared to generate corresponding trigger pulses.
If a certain H-bridge unit circuit is separated due to a fault (assuming that the first H-bridge unit circuit is separated), if the modulation strategy is not adjusted correspondingly, the sampling interval of the pulse generation timing sequence of the remaining N non-faulty H-bridge unit circuits is 2TsHowever, the sampling interval between the other power H-bridge unit circuits is TsThis clearly does not conform to the basic principle of carrier phase-shifted SPWM modulation. The harmonic content of the output voltage of the SVG device necessarily increases.
Let the carrier period be constant and still be TcBut with a sampling period at TcAnd performing internal readjustment. After a fault, the number of the multi-level inverters is changed to 5, so that the sampling period after modulation is Ts’=Tc/10. This will produce a complete carrier phase shifted output pulse of N = 5.
The method adjusts the switching modulation strategy of the SPWM by changing the sampling period of a fault phase (a phase H-bridge power module where a fault H-bridge unit circuit is located). For the phase, the phase can play a good role in regulation.
The second method comprises the following steps: t iscVariation, TsIs not changed
When the first H bridge unit circuit is separated due to failure, the sampling period T is keptsAnd adjusting the carrier triangular wave period of the phase without changing.
And the carrier period of the fault phase is Tc' after adjustment, and the carrier periods Tc of other non-fault phases are kept unchanged. And generating trigger pulses of the H-bridge power module by the once sampling modulation wave at the moments of 0/5Ts, Ts/6Ts, 2Ts/7Ts, 3Ts/8Ts and 4Ts/9 Ts. In this way, a complete N =5 carrier phase shifted SPWM pulse modulated waveform is obtained. Because the sampling period of the fault phase is not changed before and after the fault module is separated, the synchronism of three-phase current sampling can still be ensured after the fault module is separated.
Chain SVG controlling means, still include: a split-phase current independent control circuit, comprising:
a phase locked loop for tracking a voltage phase of the three phase power supply;
the reactive current setting module is suitable for calculating the cosine quantity of the voltage phase according to the voltage phase obtained by the phase-locked loop and multiplying the cosine quantity by a reactive current reference value to obtain actual reactive current output;
the active current setting module is suitable for calculating the sine quantity of the voltage phase according to the voltage phase obtained by the phase-locked loop, and meanwhile, subtracting the voltage reference value of the direct current side capacitor from the voltage average value of the direct current side capacitor of each phase H-bridge power module, multiplying the subtracted value by the sine quantity after PI control so as to obtain the actual active current output;
the instantaneous current tracking module is used for firstly superposing the currents output by the reactive current setting module and the active current setting module, then subtracting the instantaneous current in the three-phase power supply, and calculating the modulation ratio M and the phase angle of the sine modulation wave required by the pulse width modulation circuit through the controller
。
Wherein the reference current is a desired compensation current and the dc voltage reference is a desired compensation voltage.
Claims (1)
1. The utility model provides a chain SVG controlling means which characterized in that includes:
the H-bridge multi-connected multi-level inverter comprises three-phase H-bridge power modules connected to a three-phase power supply, wherein at least one standby H-bridge unit circuit is additionally arranged in each phase of H-bridge power module consisting of a plurality of H-bridge unit circuits; the automatic bypass circuit is arranged at the output end of each H bridge unit circuit;
a sampling circuit connected to the three-phase power supply and adapted to track a voltage phase of the three-phase power supply;
and said miningThe sample circuit is connected with a modulation ratio M and a phase angle suitable for outputting a sine modulation wave required by the pulse width modulation circuit according to the voltage phase of the three-phase power supply
The split-phase current independent control circuit;
the modulation ratio M and the phase angle of the sine modulation wave are used for regulating the phase of the sine modulation wave
And the pulse width modulation circuit is used for controlling carrier triangular wave phase-shifting SPWM adopted among the H bridge unit circuits.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2012205030495U CN202917979U (en) | 2012-09-27 | 2012-09-27 | Chained-mode SVG control device |
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| Application Number | Priority Date | Filing Date | Title |
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| CN2012205030495U CN202917979U (en) | 2012-09-27 | 2012-09-27 | Chained-mode SVG control device |
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| CN202917979U true CN202917979U (en) | 2013-05-01 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103401460A (en) * | 2013-06-29 | 2013-11-20 | 华为技术有限公司 | Method and device for PWM (pulse width modulation) of three-phase carrier waves |
-
2012
- 2012-09-27 CN CN2012205030495U patent/CN202917979U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103401460A (en) * | 2013-06-29 | 2013-11-20 | 华为技术有限公司 | Method and device for PWM (pulse width modulation) of three-phase carrier waves |
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