CN115882466B - Power quality management system of power distribution network based on AC-AC topological structure - Google Patents
Power quality management system of power distribution network based on AC-AC topological structure Download PDFInfo
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Abstract
The invention discloses a power quality control system of a power distribution network based on an AC-AC topological structure, which comprises a transformer, an AC-AC converter, a filter inductor and a control circuit, wherein the AC-AC converter comprises an input inductor, a Buck bridge arm and two Boost bridge arms, one end of a secondary winding of the transformer is connected with one end of the input inductor, the other end of the input inductor is connected with the midpoint of one Boost bridge arm, the midpoint of the other Boost bridge arm is grounded with the other end of the secondary winding of the transformer, and the midpoint of the Buck bridge arm is connected with the input end of a user load through the filter inductor; the control circuit is used for modulating PWM signals of a switching tube in the AC-AC converter to generate corresponding compensation waveforms when the voltage of the power grid is reduced, and guaranteeing the voltage stability of a load side. The invention realizes an AC/AC topology composed of a small number of devices, can solve the phenomenon of voltage drop in a power grid, and realizes the electric energy quality control of a distributed energy network.
Description
Technical Field
The invention belongs to the technical field of power distribution networks, and particularly relates to a power quality management system of a power distribution network based on an AC-AC topological structure.
Background
The intelligent energy multi-energy flow micro-energy network formed by various distributed energy sources (photovoltaic, energy storage, charging piles, biomass energy, air source heat pump, cold and heat storage equipment, cold and heat and electricity triple supply and the like) is a key for the future energy supply and demand development. The access of high-proportion renewable energy sources (photovoltaic and wind power) and the frequent switching of electricity loads lead to frequent fluctuation of node voltage of the power distribution network, and the frequency of voltage sag is gradually increased. Although the loss of the primary voltage sag is not large, the number of the sag caused by weather is several times and tens times of that of a power failure accident, so the loss and harm of the voltage sag to users are obvious. The voltage sag has the characteristics of short duration and wide influence range, and the voltage sag caused by short circuit can influence the normal operation of loads beyond a few kilometers. The voltage sag in the transmission system is transmitted to the power distribution system along the transmission line and finally to the terminal enterprise user, so that the normal operation of the sensitive equipment is affected. And the voltage sag makes the sensitive equipment unable to obtain the required high quality electrical energy. Voltage sags caused by equipment failure will cause an interruption of the electrical connection between the voltage and the electrical equipment, while disrupting the continuous operation of the customer equipment production line.
To solve the above problem, a power quality controller UPQC is generally used, and as shown in fig. 1, the UPQC mainly includes an inverter unit, a rectifying unit, an LC low-pass filter, a series transformer, a parallel transformer, and a control circuit part, where the control circuit includes a voltage ring, a rectifying part control link, and an inverter part control link, it is seen that the UPQC is actually an AC-DC-AC converter, and a large capacitor C is required, which is costly.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a power quality control system of a power distribution network based on an AC-AC topological structure, which can effectively save cost, namely, realize the problem of power grid voltage drop by using an AC/AC topology formed by a small number of devices and realize the power quality control of a distributed energy network.
The invention provides a power quality control system of a power distribution network based on an AC-AC topological structure, which comprises a transformer, a Boost-Buck AC-AC converter, a filter inductor and a control circuit, wherein the Boost-Buck AC-AC converter comprises an input inductor, a Buck bridge arm, a Boost bridge arm A and a Boost bridge arm B, the three bridge arms are connected in parallel, a primary winding of the transformer is connected in series on a connecting line between a power grid and a corresponding user load, one end of a secondary winding of the transformer is connected with one end of the input inductor, the other end of the input inductor is connected with a midpoint of the Boost bridge arm A, the midpoint of the Boost bridge arm B and the other end of the secondary winding of the transformer are grounded, and the midpoint of the Buck bridge arm is connected with the input end of the user load through the filter inductor;
the control circuit is used for executing the following procedures: the method comprises the steps of (1) obtaining alternating current voltage of a power grid through a transformer; (2) Judging whether the power grid voltage is reduced or not, and when the power grid voltage is judged to be normal, controlling switching tubes in all bridge arms to be switched off; when judging that the grid voltage is reduced temporarily, calculating a required compensation amount according to the acquired grid voltage and a preset grid voltage, and modulating PWM signals of switching tubes in the Boost-Buck AC-AC converter according to the compensation amount to generate corresponding compensation waveforms so as to ensure the stability of the voltage at the load side.
According to the power quality management system of the power distribution network based on the AC-AC topological structure, which is provided by the invention, the AC-AC topological structure is adopted to replace an AC-DC-AC converter in the traditional UPQC, so that the cost of dynamic voltage conditions can be reduced; the system has simple control strategy, can effectively solve the problem of voltage drop in the power grid, and realizes the power quality control of the distributed energy network.
In one embodiment, when judging that the grid voltage has a dip, the method for modulating the PWM signal of the switching tube in the Boost-Buck AC-AC converter by the control circuit includes:
according to the preset duty ratio D of the lower bridge arm switch tube S2 in the Boost bridge arm A in the positive half cycle of the alternating voltage 1 PWM signals of an upper bridge arm switch tube S5 and a lower bridge arm switch tube S6 in the Buck bridge arm are modulated to generate corresponding compensation waveforms, so that voltage stability at a load side is ensured; wherein, the upper bridge arm switch tube in the Boost bridge arm BThe PWM signals of the S3 and the lower bridge arm switching tube S4 are modulated into high-frequency complementary signals with the duty ratio of 50%, and the PWM signals of the upper bridge arm switching tube S1 and the lower bridge arm switching tube S2 in the Boost bridge arm A and the PWM signals of the upper bridge arm switching tube S5 and the lower bridge arm switching tube S6 in the Buck bridge arm are respectively modulated into complementary signals.
In one embodiment, the upper bridge arm switch tube S5 and the lower bridge arm switch tube S6 in the Buck bridge arm have a switch period T when the ac voltage is positive half cycle 1 Is divided into 0 to a 1 、a 1 ～b 1 And b 1 ～c 1 Three stages; wherein a is 1 Point corresponds to T 1 Point/2, b 1 Point corresponds to D 1 T 1 Point, c 1 The point corresponds to the end point of a single switching period and D is more than or equal to 0.5 1 ≤1；
At 0 to a 1 The switching tube S5 is turned on, and the switching tube S6 is turned off;
at a 1 ～b 1 The switching tube S5 is turned off, and the switching tube S6 is turned on;
at b 1 ～c 1 The switching tube S5 is turned on, and the switching tube S6 is turned off;
one switching period T of the upper bridge arm switching tube S5 and the lower bridge arm switching tube S6 in the Buck bridge arm in the negative half cycle of the alternating voltage 1 Divided into d 1 ～e 1 、e 1 ～f 1 And f 1 ～g 1 Three stages; wherein d 1 The point corresponds to the start point of a single switching cycle when the alternating voltage is negative half cycle, e 1 Point correspondence (1-D) 1 )T 1 A dot; f (f) 1 Point corresponds to T 1 2 points;
at d 1 ～e 1 The switching tube S5 is turned off, and the switching tube S6 is turned on;
at e 1 ～f 1 The switching tube S5 is turned on, and the switching tube S6 is turned off;
at f 1 ～g 1 In the stage, the switching tube S5 is turned off, and the switching tube S6 is turned on.
In one embodiment, the conduction period of the upper bridge arm switching tube S1 and the lower bridge arm switching tube S2 in the Boost bridge arm a is the same as the ac voltage period.
In one embodiment, the voltage U output by the Boost-Buck AC-AC converter 0 The calculation formula of (2) is as follows:
U 0 ＝(3/2-D 1 )U vin
in U vin Representing the grid ac voltage.
In one embodiment, the switching tubes in each bridge arm are all fully-controlled semiconductor devices, and each switching tube is connected in anti-parallel with a diode.
In one embodiment, the switching tubes in each leg are IGBTs or MOSFETs.
Drawings
FIG. 1 is a topology diagram of a conventional UPQC;
FIG. 2 is a schematic circuit diagram of a power quality management system for a power distribution network based on an AC-AC topology according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a Boost unit according to an embodiment of the present invention;
FIGS. 4 (a) -4 (c) are schematic diagrams illustrating the turn-on of a Boost unit during a positive half cycle of an AC voltage of a power grid according to an embodiment of the present invention;
FIGS. 4 (d) -4 (f) are schematic diagrams illustrating the turn-on of Boost units during the negative half cycle of the AC voltage of the power grid according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a modulation strategy for positive phase output of an AC-AC converter according to an embodiment of the present invention;
FIGS. 6 (a) -6 (c) are schematic diagrams illustrating the conduction of an AC-AC converter during a positive half cycle of an AC voltage in a power grid according to an embodiment of the present invention;
fig. 7 (a) to 7 (c) illustrate the conduction of the AC-AC converter at the negative half cycle of the AC voltage of the power grid according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In order to solve the problem of high cost in the conventional UPQC-based power grid voltage sag solving, the invention provides a power distribution network power quality management system based on an AC-AC topological structure, which comprises a transformer T, boost-Buck AC-AC converter and a filter inductor L as shown in figure 2 0 And a control circuit.
Wherein the Boost-Buck AC-AC converter comprises an input inductance L in The three bridge arms are connected in parallel, each bridge arm is formed by connecting an upper bridge arm switch tube and a lower bridge arm switch tube in series, the switch tubes of the upper bridge arm and the lower bridge arm in each bridge arm are all fully-controlled semiconductor devices such as IGBT (insulated gate bipolar transistor) or MOSFET (metal oxide semiconductor field effect transistor), and each switch tube is connected in anti-parallel with a diode. The AC-AC topological structure provided by the embodiment adopts a Boost-Buck AC-AC converter based on a switching tube, and can provide various working modes, including functions of in-phase Buck, in-phase Boost, anti-phase Buck, anti-phase Boost and the like.
The connection relation of each device provided in this embodiment is: the primary winding of the transformer T is connected in series with the connection line between the power grid and the corresponding user load (i.e. the load in figure 2), and one end of the secondary winding of the transformer T is connected with the input inductance L in Is connected to one end of the input inductance L in The other end of the bridge arm is connected with the midpoint of the Boost bridge arm A, the midpoint of the Boost bridge arm B and the other end of the secondary winding of the transformer T are grounded, and the midpoint of the Buck bridge arm passes through the filter inductor L 0 Connected to the input of the user load.
The control circuit provided in this embodiment is used for executing the following procedures: the method comprises the steps of (1) obtaining alternating current voltage of a power grid through a transformer; (2) Judging whether the power grid voltage is reduced or not, and when the power grid voltage is judged to be normal, controlling the switching tubes in the bridge arms to be turned off so that the AC-AC converter is in a bypass state and does not participate in the exchange of power grid energy. When judging that the grid voltage sags, calculating the required compensation quantity according to the obtained grid voltage and the preset grid voltage and a compensation quantity calculating method commonly used in the field, modulating PWM signals of a switching tube in the Boost-Buck AC-AC converter according to the compensation quantity to generate corresponding compensation waveforms, namely flexibly adjusting the voltage through an AC-AC topological structure with a Boost-Buck flexible control function, dynamically adjusting the output voltage of the voltage, and then stringing the adjusted voltage into a circuit through a transformer T again, so that the sag of the grid voltage is counteracted, and the stability of the voltage at the load side is ensured.
According to the power quality management system of the power distribution network based on the AC-AC topological structure, which is provided by the embodiment, the AC-AC topological structure is adopted to replace an AC-DC-AC converter in the traditional UPQC, so that the cost of dynamic voltage conditions can be reduced; the system has simple control strategy, can effectively solve the problem of voltage drop in the power grid, and realizes the power quality control of the distributed energy network.
It should be noted that, the control circuit provided by the invention modulates the PWM signal of the switching tube in the Boost-Buck AC-AC converter, so that the control circuit has the following working principle of the voltage Boost-Buck flexible control function:
fig. 3 is a schematic diagram of a Boost unit modulation scheme according to an embodiment of the present invention, where 0 to D in fig. 4 represent half a sine cycle, T represents one switching cycle of the switching transistors S5 and S6, a preset on cycle of the switching transistors S1 and S2 is equal to a power grid ac voltage cycle, D represents a preset duty cycle of the switching transistor S2 in a positive half cycle of the power grid ac voltage, and a detailed description is made on the principle of the Boost unit formed by the switching transistors S1 to S4.
Taking fig. 4 (a) to 4 (c) as an example. In fig. 4 (a) to 4 (c), when the ac voltage of the power grid is positive half cycle, the Boost unit in the whole topology is analyzed separately, and in fig. 4 (a) and 4 (b), the power grid inputs inductance L in Charging, in fig. 4 (c), the grid and the input inductance L in Simultaneously supplying power to the load, so that the output voltage reaches Boost effect
In fig. 4 (a) and 4 (b), the inductance L is input in The above using volt-second equilibrium gives:
in fig. 4 (c), the inductance L is input in The above using volt-second equilibrium gives:
(T-DT)(U in -U 0 )
so there are:
fig. 4 (d) -4 (f) are the conduction conditions when the ac voltage of the grid is negative half cycle.
So there is a topology Boost unit that can Boost the grid ac voltage by a factor of more than 2.
When the grid ac voltage is positive, a single switching cycle in the Boost unit is divided into: 0-a, a-b and b-c; wherein, the point a corresponds to T/2, the point b corresponds to DT, the point c corresponds to the end point of a single switching period, and T represents the switching period of a single Boost unit; DT-1/2T represents the time that the switching tube S1 is turned off in the whole switching cycle; and D is more than or equal to 0.5 and less than or equal to 1.
In 0-a, an upper bridge arm switching tube S1 in a Boost bridge arm A and an upper bridge arm switching tube S3 in a Boost bridge arm B are conducted, and a lower bridge arm switching tube S2 in the Boost bridge arm A and a lower bridge arm switching tube S4 in the Boost bridge arm B are cut off.
In a-B, an upper bridge arm switch tube S1 in a Boost bridge arm A and an upper bridge arm switch tube S3 in a Boost bridge arm B are turned off, and a lower bridge arm switch tube S2 in the Boost bridge arm A and a lower bridge arm switch tube S4 in the Boost bridge arm B are turned on.
In B-c, the upper bridge arm switching tube S1 in the Boost bridge arm A and the lower bridge arm switching tube S4 in the Boost bridge arm B are turned on, and the lower bridge arm switching tube S2 in the Boost bridge arm A and the upper bridge arm switching tube S3 in the Boost bridge arm B are turned off.
When the alternating voltage of the power grid is negative in half cycle, a single switching cycle of the Boost unit is divided into: d-e, e-f and f-g; when the point D corresponds to the negative half cycle of the input alternating current, the starting point of a single switching cycle of the Boost unit, e corresponds to (1-D) T, f corresponds to T/2, and the point g corresponds to the cycle ending point T.
In d-e, an upper bridge arm switching tube S1 in a Boost bridge arm A and a lower bridge arm switching tube S4 in a Boost bridge arm B are turned off, and a lower bridge arm switching tube S2 in the Boost bridge arm A and an upper bridge arm switching tube S3 in the Boost bridge arm B are turned on.
In e-f, the upper bridge arm switching tube S1 in the Boost bridge arm A and the upper bridge arm switching tube S3 in the Boost bridge arm B are turned on, and the lower bridge arm switching tube S2 in the Boost bridge arm A and the lower bridge arm switching tube S4 in the Boost bridge arm B are turned off.
In f-g, an upper bridge arm switching tube S1 in a Boost bridge arm A and an upper bridge arm switching tube S3 in a Boost bridge arm B are turned off, and a lower bridge arm switching tube S2 in the Boost bridge arm A and a lower bridge arm switching tube S4 in the Boost bridge arm B are turned on.
For convenience of description, the following transformation preset d=0.5 is discussed:
fig. 5 is a schematic diagram of a modulation strategy during normal phase output of an AC-AC converter according to an embodiment of the present invention, as shown in fig. 5, the switching transistors S3 and S4 are high-frequency complementary signals with a duty ratio of 50%, respectively, and a Boost effect is obtained by presetting the switching transistors S1 and S2, and a Buck effect is obtained by modulating the switching transistors S5 and S6. The circuit state of each stage at the time of forward output is as shown in fig. 6 (a) to 6 (c) and 7 (a) to 7 (c).
In FIG. 6, (a) is from 0 to a 1 The circuit is turned on at the moment (i.e., 0-T/2), and the inductance L is input in The above using volt-second equilibrium to giveFIG. 6 (b) shows T/2-D 1 The circuit is conducted at the moment T, and the inductance L is input in The upper using volt-second balance is 0. FIG. 6 (c) is D 1 The circuit is conducted at the moment of T-T, and the inductance L is input in The above using the volt-second equilibrium gives (T-D 1 T)U in . And the whole switching period is obtained according to the volt-second balance principle: />
It can be solved that:
from this, it is clear that if the on-state strategy of the switching transistors S1 and S2 is set to be the same as the grid ac voltage period, the output voltage can be changed in the grid ac voltage in the range of 0.5 to 1 times.
When the grid alternating voltage is positive half cycle, a single switching cycle in the Buck unit is divided into: 0 to a 1 、a 1 ～b 1 And b 1 ～c 1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein a is 1 Point corresponds to T 1 /2，b 1 Point corresponds to D 1 T 1 ,c 1 The point corresponds to the end point of a single switching period, T 1 Representing a single Boost unit switching period; (1-D) 1 )T 1 Indicating the time that the switching tube S6 is turned on in the entire switching cycle; and D is more than or equal to 0.5 1 ≤1。
As shown in fig. 6 (a) to 6 (c), the values are 0 to a 1 In the method, an upper bridge arm switching tube S5 in the Buck unit is conducted, and a lower bridge arm switching tube S6 in the Buck unit is cut off; at a 1 ～b 1 In the method, an upper bridge arm switching tube S5 in the Buck unit is turned off, and a lower bridge arm switching tube S6 in the Buck unit is turned on; at b 1 ～c 1 In the Buck unit, the upper bridge arm switching tube S5 is turned on, and the lower bridge arm switching tube S6 is turned off.
When the alternating voltage of the power grid is negative half cycle, the single switching cycle of the positive-phase Boost unit is divided into d 1 ～e 1 、e 1 ～f 1 And f 1 ～g 1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein d 1 When the point corresponds to the negative half cycle of the input alternating current, the starting point, e, of a single switching cycle of the Boost unit 1 Correspondence (1-D) 1 )T 1 ，f 1 Corresponding T 1 The g point corresponds to the cycle end point T 1 。
As shown in fig. 7 (a) to 7 (c), at d 1 ～e 1 In the method, an upper bridge arm switching tube S5 in the Buck unit is turned off, and a lower bridge arm switching tube S6 in the Buck unit is turned on; at e 1 ～f 1 In the method, an upper bridge arm switching tube S5 in the Buck unit is conducted, and a lower bridge arm switching tube S6 in the Buck unit is cut off; at f 1 ～g 1 In the Buck unit, the upper bridge arm switching tube S5 is turned off, and the lower bridge arm switching tube S6 is turned on.
The power quality management system of the power distribution network based on the AC-AC topological structure has the following effects: (1) The AC-AC topological structure with fewer components can effectively reduce the cost of dynamic voltage regulation, and the topology modulation strategy is simple and convenient and has wide modulation range; (2) The system can naturally realize safe commutation without using an RC buffer or a soft commutation strategy, thereby effectively eliminating the need of pulse width modulation dead time; (3) The adoption of the external fast recovery diode can avoid the high-frequency conduction of the MOSFET body diode, and effectively eliminate the slow reverse recovery problem and the corresponding power loss; (4) A common ground is shared between the input and output ports to provide support for the reactive load, draw a continuous sinusoidal current from the ac power source, and provide a continuous output current. The power supply can replace an AC/DC/AC converter in the traditional UPQC, greatly saves the system cost and effectively solves the power quality problem of a distributed energy network.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (6)
1. The power quality control system of the power distribution network based on the AC-AC topological structure is characterized by comprising a transformer, a Boost-Buck AC-AC converter, a filter inductor and a control circuit, wherein the Boost-Buck AC-AC converter comprises an input inductor, a Buck bridge arm, a Boost bridge arm A and a Boost bridge arm B, the three bridge arms are connected in parallel, a primary winding of the transformer is connected in series on a connecting line between a power grid and a corresponding user load, one end of a secondary winding of the transformer is connected with one end of the input inductor, the other end of the input inductor is connected with the midpoint of the Boost bridge arm A, the midpoint of the Boost bridge arm B is connected with the other end of the secondary winding of the transformer, and the midpoint of the Buck bridge arm is connected with the input end of the user load through the filter inductor;
the control circuit is used for executing the following procedures: the method comprises the steps of (1) obtaining alternating current voltage of a power grid through a transformer; (2) Judging whether the power grid voltage is reduced or not, and when the power grid voltage is judged to be normal, controlling switching tubes in all bridge arms to be switched off; when judging that the grid voltage is reduced temporarily, calculating a required compensation amount according to the acquired grid voltage and a preset grid voltage, and modulating PWM signals of a switching tube in the Boost-Buck AC-AC converter according to the compensation amount to generate corresponding compensation waveforms so as to ensure that the voltage at the load side is stable;
when judging that the power grid voltage is reduced, the control circuit modulates the PWM signal of the switching tube in the Boost-Buck AC-AC converter by the following method:
according to the preset duty ratio D of the lower bridge arm switch tube S2 in the Boost bridge arm A in the positive half cycle of the alternating voltage 1 PWM signals of an upper bridge arm switch tube S5 and a lower bridge arm switch tube S6 in the Buck bridge arm are modulated to generate corresponding compensation waveforms, so that voltage stability at a load side is ensured; the PWM signals of the upper bridge arm switching tube S3 and the lower bridge arm switching tube S4 in the Boost bridge arm B are modulated into high-frequency complementary signals with a duty ratio of 50%, and the PWM signals of the upper bridge arm switching tube S1 and the lower bridge arm switching tube S2 in the Boost bridge arm a and the PWM signals of the upper bridge arm switching tube S5 and the lower bridge arm switching tube S6 in the Buck bridge arm are respectively modulated into complementary signals.
2. The AC-AC topology based power distribution network power quality management system of claim 1, wherein an upper leg switching tube S5 and a lower leg switching tube S6 in the Buck leg have a switching period T when the AC voltage is positive half cycle 1 Is divided into 0 to a 1 、a 1 ～b 1 And b 1 ～c 1 Three stages; wherein a is 1 Point corresponds to T 1 Point/2, b 1 Point corresponds to D 1 T 1 Point, c 1 The point corresponds to the end point of a single switching period and D is more than or equal to 0.5 1 ≤1；
At 0 to a 1 The switching tube S5 is turned on, and the switching tube S6 is turned off;
at a 1 ～b 1 The switching tube S5 is turned off, and the switching tube S6 is turned on;
at b 1 ～c 1 Stage(s)The switch tube S5 is turned on, and the switch tube S6 is turned off;
one switching period T of the upper bridge arm switching tube S5 and the lower bridge arm switching tube S6 in the Buck bridge arm in the negative half cycle of the alternating voltage 1 Divided into d 1 ～e 1 、e 1 ～f 1 And f 1 ～g 1 Three stages; wherein d 1 The point corresponds to the start point of a single switching cycle when the alternating voltage is negative half cycle, e 1 Point correspondence (1-D) 1 )T 1 A dot; f (f) 1 Point corresponds to T 1 2 points;
at d 1 ～e 1 The switching tube S5 is turned off, and the switching tube S6 is turned on;
at e 1 ～f 1 The switching tube S5 is turned on, and the switching tube S6 is turned off;
at f 1 ～g 1 In the stage, the switching tube S5 is turned off, and the switching tube S6 is turned on.
3. The power quality management system of a power distribution network based on an AC-AC topology according to claim 2, wherein the conduction period of the upper arm switching tube S1 and the lower arm switching tube S2 in the Boost arm a is the same as the AC voltage period.
4. The AC-AC topology based power distribution network power quality management system of claim 3, wherein said Boost-Buck AC-AC converter outputs a voltage U 0 The calculation formula of (2) is as follows:
U 0 ＝(3/2-D 1 )U vin
in U vin Representing the grid ac voltage.
5. The power quality management system of the power distribution network based on the AC-AC topological structure according to claim 1, wherein the switching tubes in each bridge arm are all fully-controlled semiconductor devices, and each switching tube is connected with a diode in anti-parallel.
6. The power quality management system of the power distribution network based on the AC-AC topological structure according to claim 5, wherein the switching tubes in each bridge arm are all Insulated Gate Bipolar Transistors (IGBT) or Metal Oxide Semiconductor Field Effect Transistors (MOSFET).
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| KR20000038849A (en) * | 1998-12-09 | 2000-07-05 | 김진한 | Uninterruptible power supply and method for controlling the same |
| CN114268104A (en) * | 2020-09-16 | 2022-04-01 | 苏州爱科赛博电源技术有限责任公司 | Novel transformerless three-bridge-arm series active voltage quality regulator and control method |
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