CN219918709U - Single-phase grid-connected converter capable of reducing impact current - Google Patents
Single-phase grid-connected converter capable of reducing impact current Download PDFInfo
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Abstract
The utility model discloses a single-phase grid-connected converter capable of reducing impulse current, and relates to the technical field of DC/AC converters. The utility model comprises a converter and a monitoring controller, wherein the converter is used for converting input direct current into alternating current for output, and the monitoring controller is used for monitoring and controlling direct current-alternating current conversion of the converter and slowly increasing the inversion open-loop voltage until the amplitude of the grid voltage. According to the utility model, the inversion open-loop voltage is slowly increased until the power grid voltage amplitude is reached by adopting a wave-buffering mode; and when the last main control relay is closed, the relay is adopted to detect open loop and then keep open loop control all the time, so that the inversion open loop voltage is synchronous with the amplitude, the phase and the frequency of the power grid voltage, no impact current is generated when the main control switch is closed, and the problem of reducing the impact current in the aspects of design and element selection is not required to be considered in the whole process, so that the performance of the converter is improved.
Description
Technical Field
The utility model belongs to the technical field of DC/AC converters, and particularly relates to a single-phase grid-connected converter capable of reducing impact current.
Background
The single-phase grid-connected converter has the advantages of simple circuit, easy design of driving and the like, has wide application in a plurality of fields such as new energy application and the like, and simultaneously becomes a big hot spot for researching the performance and optimizing the control strategy.
In a common single-phase grid-connected converter, the possible point of current impact is that the inverter voltage generated under open-loop control based on power grid feedforward is easy to generate larger impact current on a grid-connected filter capacitor at open-loop wave generation time in the relay detection process; when the last main control relay is closed, larger power grid voltage and inversion voltage difference easily generate impact current to the filter capacitor; the impact current can affect machine life and stability and severely impact transient and steady state performance of the system.
For the problems in the related art, no effective solution has been proposed at present.
Disclosure of Invention
Aiming at the problems in the related art, the utility model provides a single-phase grid-connected converter for reducing the impact current so as to overcome the technical problems in the prior related art.
In order to solve the technical problems, the utility model is realized by the following technical scheme:
the utility model relates to a single-phase grid-connected converter for reducing impulse current, which comprises: the monitoring controller is used for monitoring and controlling the direct current-alternating current conversion of the converter and slowly increasing the inversion open-loop voltage until the power grid voltage amplitude; the converter comprises a bus capacitor, an H-bridge inverter circuit, a filter circuit, a main relay, an auxiliary relay and a power grid interface, wherein the input current provided by the bus capacitor is firstly converted into alternating current by the H-bridge inverter circuit and then is output to the filter circuit, the main relay and the auxiliary relay jointly control the communication relationship between the filter circuit and the power grid interface, and when the main relay and the auxiliary relay are both in a closed state, the filter circuit is used for filtering the alternating current converted by the H-bridge inverter circuit and then outputting the filtered alternating current to the power grid interface; the monitoring controller can acquire the power grid voltage from the power grid interface, and can control the output of a modulation signal to the H-bridge inverter circuit according to the power grid voltage so as to synchronize the amplitude and the frequency of the inverter open-loop voltage output from the power grid interface with the power grid voltage.
Further, the H-bridge inverter circuit is connected in parallel to two ends of the bus capacitor, the H-bridge inverter circuit comprises a first bridge arm and a second bridge arm which are connected in parallel, the first bridge arm and the second bridge arm comprise two transistors connected in series, and the filter circuit is connected in series between midpoints of the first bridge arm and the second bridge arm.
Further, the filter circuit comprises a first filter inductor, a filter capacitor and a second filter inductor which are sequentially connected in series, the power grid interface is connected in parallel with two ends of the filter capacitor, and the main relay and the auxiliary relay are connected in parallel with the parallel circuit of the power grid interface and the filter capacitor.
Further, the monitoring controller comprises a PLL, a current inner loop and a voltage outer loop, wherein the PLL can be used for phase locking after sampling the grid voltage from the grid interface; the voltage outer ring can compare a given reference voltage of the bus with an actual voltage of the bus, and obtains a current ring inner ring current reference given after PI regulation output; and the current inner loop can compare the current reference given by the current inner loop with the current actual value, output the current through PR adjustment, and output SPWM to the H-bridge inverter circuit after the feedforward compensation of the grid voltage.
Further, before grid connection, voltage open-loop control is adopted, and current reference of a current loop output by the voltage open-loop is given as 0; after grid connection, voltage closed-loop control is adopted, the given reference voltage of the bus and the actual voltage of the bus are compared, and the current reference of the current loop is regulated through PI.
The utility model has the following beneficial effects:
in the control of the single-phase grid-connected converter, the inversion voltage at the open-loop wave generation moment based on open-loop control of the power grid feedforward in the relay detection process easily generates larger impulse current on the grid-connected filter capacitor, and the inversion open-loop voltage is slowly increased until the power grid voltage amplitude is reached by adopting a wave-buffering mode, so that the impulse current can be well solved.
When the last main control relay is closed, larger grid voltage and inversion voltage difference easily generate impulse current to the filter capacitor, after the relay is adopted to detect open loop and send out, open loop control is kept all the time, so that the inversion open loop voltage realizes synchronization with the amplitude, the phase and the frequency of the grid voltage, no impulse current is generated when the main control switch is closed, and the problem of reducing the impulse current in design and element selection is avoided in the whole process, so that the performance of the converter is improved.
Of course, it is not necessary for any one product to practice the utility model to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings that are needed for the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the utility model, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a circuit topology of a single-phase grid-tied inverter for reducing inrush current in accordance with the present utility model;
FIG. 2 is a circuit topology and control diagram of a single-phase grid-connected inverter for reducing inrush current in accordance with the present utility model;
FIG. 3 is a timing diagram of a single-phase grid-connected inverter grid-connected process for reducing rush current according to the present utility model;
Detailed Description
The following description of the technical solutions in the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings in the embodiments of the present utility model, and it is apparent that the described embodiments are only some embodiments of the present utility model, not all embodiments. All other embodiments, based on the embodiments in the utility model, which a person of ordinary skill in the art would obtain without inventive faculty, are within the scope of the utility model.
In the description of the present utility model, it should be understood that the terms "open," "upper," "lower," "top," "middle," "inner," and the like indicate an orientation or positional relationship, merely for convenience of description and to simplify the description, and do not indicate or imply that the components or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the utility model.
Referring to fig. 1-3, the present utility model is a single-phase grid-connected inverter for reducing surge current, comprising: the monitoring controller is used for monitoring and controlling the direct current-alternating current conversion of the converter and slowly increasing the inversion open-loop voltage until the power grid voltage amplitude; the converter comprises a bus capacitor, an H-bridge inverter circuit, a filter circuit, a main relay, an auxiliary relay and a power grid interface, wherein the input current provided by the bus capacitor is firstly converted into alternating current by the H-bridge inverter circuit and then is output to the filter circuit, the main relay and the auxiliary relay jointly control the communication relationship between the filter circuit and the power grid interface, and when the main relay and the auxiliary relay are both in a closed state, the filter circuit is used for filtering the alternating current converted by the H-bridge inverter circuit and then outputting the filtered alternating current to the power grid interface; the monitoring controller can acquire the power grid voltage from the power grid interface, and can control the output of a modulation signal to the H-bridge inverter circuit according to the power grid voltage so as to synchronize the amplitude and the frequency of the inverter open-loop voltage output from the power grid interface with the power grid voltage.
In one embodiment, the H-bridge inverter circuit is connected in parallel to two ends of the bus capacitor, the H-bridge inverter circuit includes a first bridge arm and a second bridge arm connected in parallel, the first bridge arm and the second bridge arm each include two transistors connected in series, and the filter circuit is connected in series between midpoints of the first bridge arm and the second bridge arm.
In one embodiment, the filter circuit comprises a first filter inductor, a filter capacitor and a second filter inductor which are sequentially connected in series, the power grid interface is connected in parallel with two ends of the filter capacitor, and the main relay and the auxiliary relay are connected in parallel with the parallel circuit of the power grid interface and the filter capacitor.
In one embodiment, the control controller comprises a PLL, a current inner loop and a voltage outer loop, the PLL being capable of phase locking after sampling a grid voltage from the grid interface; the voltage outer ring can compare a given reference voltage of the bus with an actual voltage of the bus, and obtains a current ring inner ring current reference given after PI regulation output; and the current inner loop can compare the current reference given by the current inner loop with the current actual value, output the current through PR adjustment, and output SPWM to the H-bridge inverter circuit after the feedforward compensation of the grid voltage.
In one embodiment, before grid connection, voltage open-loop control is adopted, and the current reference of the current loop of the voltage open-loop output is given as 0; after grid connection, voltage closed-loop control is adopted, the given reference voltage of the bus and the actual voltage of the bus are compared, and the current reference of the current loop is regulated through PI.
Referring to fig. 1, the topology structure of the single-phase grid-connected converter for reducing the impact current adopts a topology structure that an inverter circuit based on an H bridge is composed of a bus capacitor C1, a MOSFET, a diode, an inductor L, a filter capacitor C, a main Relay relay_m, an auxiliary Relay relay_s and other devices, as shown in fig. 1, the positive electrode of the bus capacitor C1 is connected to the collectors of S1 and S2 respectively, the negative electrode is connected to the emitters of S3 and S4, wherein S1, S2, S3 and S4 are all structures of antiparallel diodes. And the middle points of the bridge arms formed by S1 and S3 and the middle points of the bridge arms formed by S2 and S4 are respectively led out to be connected with an inductor L, a main Relay Relay_M and an auxiliary Relay Relay_S in series to a power grid Ug, and the two inductors are directly connected in parallel to a filter capacitor C to form a filter circuit structure of the LCL.
Referring to fig. 2, +, -symbol is an operator, in the control link of the single-phase grid-connected converter for reducing the impact current, the voltage open loop is needed, namely the inversion open loop control is performed when the relay is detected before grid connection after the grid voltage is subjected to phase locking by the PLL, the reference value of the inner loop current loop is directly given to be 0, the voltage loop PR is adjusted, the feedforward compensation of the grid voltage is added, and finally the output is modulated by the SPWM, so that the inversion open loop voltage can be synchronized with the amplitude and the frequency phase of the grid voltage. And switching to voltage closed-loop control after grid connection, namely regulating a busbar voltage outer ring, a current inner ring and a current ring PR, adding a grid voltage feedforward compensation, and finally SPWM modulating output.
Table 1 shows a Relay detection stage table, in which the switching states of the main Relay relay_M and the auxiliary Relay relay_S, the inversion open loop output enable conditions (inversion open loop output conditions; circuit on-off conditions at positions V1 and V2), the judgment results and the test purposes are shown in Table 1, and the Relay detection stage table is divided into 6 stages for detection.
Table 1: relay detection stage table
The single-phase grid-connected converter for reducing the impact current has the impact current when the voltage of the inversion open loop passes through the LCL (filter circuit) in the figure 1 in the first open loop in the relay detection, so that the voltage compensation of the first open loop adopts a slow increase compensation mode, the voltage of the inversion open loop is slowly started, and the instant larger impact current of the open loop can not be caused.
Referring to fig. 3, in the grid-connected process timing diagram of the single-phase grid-connected converter for reducing the impact current, after the Relay is detected, the auxiliary control relay_s is closed, then the main control Relay relay_m is closed, the open-loop state of the voltage is kept unchanged, at the moment, the inversion open-loop voltage is synchronous with the amplitude, the phase and the frequency of the voltage of the power grid, no larger impact current exists after the main control is closed, finally, the main control Relay is switched to closed-loop control after being closed through time delay, no impact current in the whole process can be seen, and therefore the purpose of reducing the impact current is achieved on the basis of not increasing any hardware cost.
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the utility model. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above disclosed preferred embodiments of the utility model are merely intended to help illustrate the utility model. The preferred embodiments are not exhaustive or to limit the utility model to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the utility model and the practical application, to thereby enable others skilled in the art to best understand and utilize the utility model.
Claims (5)
1. A single-phase grid-tie inverter for reducing inrush current, comprising: the monitoring controller is used for monitoring and controlling the direct current-alternating current conversion of the converter and slowly increasing the inversion open-loop voltage until the power grid voltage amplitude;
the converter comprises a bus capacitor, an H-bridge inverter circuit, a filter circuit, a main relay, an auxiliary relay and a power grid interface, wherein the input current provided by the bus capacitor is firstly converted into alternating current by the H-bridge inverter circuit and then is output to the filter circuit, the main relay and the auxiliary relay jointly control the communication relationship between the filter circuit and the power grid interface, and when the main relay and the auxiliary relay are both in a closed state, the filter circuit is used for filtering the alternating current converted by the H-bridge inverter circuit and then outputting the filtered alternating current to the power grid interface;
the monitoring controller can acquire the power grid voltage from the power grid interface, and can control the output of a modulation signal to the H-bridge inverter circuit according to the power grid voltage so as to synchronize the amplitude and the frequency of the inverter open-loop voltage output from the power grid interface with the power grid voltage.
2. The single-phase grid-tie inverter for reducing rush current according to claim 1 wherein: the H-bridge inverter circuit is connected in parallel with two ends of the bus capacitor and comprises a first bridge arm and a second bridge arm which are connected in parallel, the first bridge arm and the second bridge arm comprise two transistors connected in series, and the filter circuit is connected in series between midpoints of the first bridge arm and the second bridge arm.
3. The single-phase grid-tie inverter for reducing rush current according to claim 2 wherein: the filter circuit comprises a first filter inductor, a filter capacitor and a second filter inductor which are sequentially connected in series, the power grid interface is connected in parallel with two ends of the filter capacitor, and the main relay and the auxiliary relay are connected in parallel with the parallel circuit of the power grid interface and the filter capacitor.
4. The single-phase grid-tie inverter for reducing rush current according to claim 1 wherein: the monitoring controller comprises a PLL, a current inner loop and a voltage outer loop;
the PLL can sample the grid voltage from the grid interface and then carry out phase locking;
the voltage outer ring can compare a given reference voltage of the bus with an actual voltage of the bus, and obtains a current ring inner ring current reference given after PI regulation output;
and the current inner loop can compare the current reference given by the current inner loop with the current actual value, output the current through PR adjustment, and output SPWM to the H-bridge inverter circuit after the feedforward compensation of the grid voltage.
5. The single-phase grid-tie inverter for reducing rush current according to claim 4 wherein: before grid connection, voltage open-loop control is adopted, and current reference of a current loop output by the voltage open-loop is given as 0;
after grid connection, voltage closed-loop control is adopted, the given reference voltage of the bus and the actual voltage of the bus are compared, and the current reference of the current loop is regulated through PI.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202320346068.XU CN219918709U (en) | 2023-02-24 | 2023-02-24 | Single-phase grid-connected converter capable of reducing impact current |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202320346068.XU CN219918709U (en) | 2023-02-24 | 2023-02-24 | Single-phase grid-connected converter capable of reducing impact current |
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