Inverter

Abstract

The utility model discloses an inverter, which comprises an inversion unit, a grid-connected unit and a filtering unit, and is characterized in that the output end of the inversion unit is connected to a power grid through the grid-connected unit and the filtering unit in sequence; the filtering unit comprises a capacitive device, and at least one controllable switch is arranged on a capacitive device branch between any two phases. Through the at least one controllable switch on the capacitive device branch between any two phases, whether the capacitor is put into operation or not can be controlled by controlling the controllable switch; the problem of power consumption caused by the fact that a capacitor is connected with a network when the inverter is in a standby or shutdown state is solved, the service life of the capacitor is prolonged, the voltage difference between two phases is reduced to be within a safe voltage range, the requirement for quick turn-off is met, and the risk of electric shock is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to an inverter. Background Art

[0002] like Figure 1 As shown, in the inverter, the output end of the inverter unit will first be connected to the grid-connected unit, then to the filter unit, and finally to the grid. Placing the filter unit at the inverter port can obtain a better filtering effect, but when the inverter is not in the grid-connected state, the filter capacitor in the filter unit will become a capacitive load of the grid, thereby generating unnecessary reactive power consumption. For this reason, the owner not only needs to pay for the power consumed by the capacitor, but may even face a fine on the grid side due to excessive reactive power. In addition, the presence of the AC port capacitor will cause residual pressure on the capacitor after the grid loses power and the relay is disconnected. At this time, the DC voltage between the AC phase lines will not meet the requirements for rapid shutdown. When someone touches the terminals between the phase lines, there is a risk of electric shock, causing a safety accident. Utility Model Content

[0003] The present application provides an inverter to solve the problem of power consumption caused by capacitor connection when the inverter is in standby or shutdown state.

[0004] On one hand, the present application provides an inverter, comprising an inverter unit, a grid-connected unit and a filter unit, wherein the output end of the inverter unit is connected to a grid through the grid-connected unit and the filter unit in sequence;

[0005] The filtering unit includes a capacitive device, and there is at least one controllable switch on the capacitive device branch between any two phases;

[0006] The capacitive device includes a first capacitive device, a second capacitive device and a third capacitive device, and the controllable switch includes a first controllable switch and a second controllable switch; one end of the first capacitive device is connected to the first phase of the three-phase power grid, and the other end of the first capacitive device is connected to a common point through the first controllable switch; one end of the second capacitive device is connected to the second phase of the three-phase power grid, and the other end of the second capacitive device is connected to the common point through the second controllable switch; one end of the third capacitive device is connected to the third phase of the three-phase power grid, and the other end of the third capacitive device is connected to the common point; or,

[0007] One end of the capacitive device is connected to a first phase among the three phases of the power grid, and the other end of the capacitive device is connected to a second phase among the three phases of the power grid through the controllable switch.

[0008] In one example, a control unit is also included;

[0009] The control unit is configured to detect whether the inverter is in a grid-connected state. If the inverter is in a grid-connected state, all controllable switches are controlled to be closed; if the inverter is in a non-grid-connected state, at least one controllable switch on a capacitive device branch between any two phases is controlled to be disconnected.

[0010] In one example, the control unit is configured to determine whether the inverter is in a grid-connected state by detecting an on or off state of the grid-connected unit.

[0011] In one example, a resistor connected in parallel with the capacitive device is also included.

[0012] In one example, the controllable switch includes at least one of a relay, a contactor, a circuit breaker, and a semiconductor switch.

[0013] In one example, the grid-connected unit includes a grid-connected switch.

[0014] In one example, the grid-connected switch includes a relay.

[0015] The inverter provided by the present application uses at least one controllable switch on the capacitive device branch between any two phases, so that by controlling the controllable switch, it is possible to control whether the capacitor is put into operation; it solves the problem of power consumption caused by capacitor grid connection when the inverter is in standby or shutdown state, increases the service life of the capacitor, reduces the voltage difference between the two phases to within a safe voltage range, meets the rapid shutdown requirements, and reduces the risk of electric shock. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A circuit diagram of an existing inverter;

[0017] Figure 2 A circuit diagram of an inverter provided in an embodiment of the present application;

[0018] Figure 3 A circuit diagram of another inverter provided in an embodiment of the present application;

[0019] Figure 4 A circuit diagram of another inverter provided in an embodiment of the present application;

[0020] Figure 5 A schematic diagram of a control method for an inverter provided in an embodiment of the present application.

[0021] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer and more understandable, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "front", "back", "left", "right", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0024] Figure 2 A circuit diagram of an inverter provided in an embodiment of the present application.

[0025] like Figure 2 As shown, the inverter includes an inverter unit, a grid-connected unit, a filter unit and a control unit. The output end of the inverter unit is connected to the grid (shown as L1 to L3 in the figure) through the grid-connected unit and the filter unit in sequence.

[0026] The grid-connected unit includes a plurality of grid-connected switches, and each phase is provided with at least one grid-connected switch; taking the figure as an example, each phase is provided with a grid-connected switch, namely K1 to K3 in the figure. The grid-connected switches include but are not limited to relays, contactors, and the like.

[0027] In the filter unit, each phase is provided with at least one capacitive device, such as a filter capacitor, and all filter capacitors have a common point (common connection point). The filter capacitor can be an ordinary capacitor (lower cost) or an X capacitor. Taking the figure as an example, the filter unit includes three filter capacitors, and the three filter capacitors have a common point (shown as O in the figure); wherein one end of the filter capacitor C1 is connected to the first phase (L1), and the other end is connected to the common point of the filter capacitor (shown as O in the figure); one end of the filter capacitor C2 is connected to the second phase, and the other end is connected to the common point of the filter capacitor (shown as O in the figure); one end of the filter capacitor C3 is connected to the third phase, and the other end is connected to the common point of the filter capacitor (shown as O in the figure).

[0028] Further, there is at least one controllable switch on the capacitive device branch between any two phases. Taking the figure as an example, one end of the filter capacitor C1 is connected to the first phase, and the other end is connected to the common point of the filter capacitor through the controllable switch S1 (shown as O in the figure). It can be understood that in addition to the controllable switch S1, other controllable switches can be set on this branch, that is, multiple controllable switches are connected in series; one end of the filter capacitor C2 is connected to the second phase, and the other end is connected to the common point of the filter capacitor through the controllable switch S2 (shown as O in the figure); one end of the filter capacitor C3 is connected to the third phase, and the other end is directly connected to the common point of the filter capacitor (shown as O in the figure).

[0029] Controllable switches include but are not limited to relays, contactors, circuit breakers, semiconductor switches, etc.

[0030] The control unit is configured to detect whether the inverter is in a grid-connected state. If the inverter is in a grid-connected state, all controllable switches are controlled to be closed; if the inverter is in a non-grid-connected state, at least one controllable switch on a capacitive device branch between any two phases is controlled to be disconnected.

[0031] Taking the figure as an example, if the inverter is in a grid-connected state, the controllable switches S1 and S2 are controlled to be closed; if the inverter is in a non-grid-connected state, the controllable switches S1 and S2 are controlled to be opened.

[0032] It is understandable that if there are multiple controllable switches on the capacitive device branch, only one of the controllable switches needs to be disconnected. For example, if there are multiple controllable switches S1 connected in series between the first phase and the third phase, only one of the controllable switches needs to be disconnected.

[0033] It should be noted that if the inverter is in a non-grid-connected state and only the controllable switch S1 is controlled to be disconnected, power consumption will still be generated in the loop between the second phase (L2) and the third phase (L3); similarly, if only the controllable switch S2 is controlled to be disconnected, power consumption will still be generated in the loop between the first phase (L1) and the third phase (L3).

[0034] In a specific implementation, the control unit can determine whether the inverter is in a grid-connected state by detecting the on or off state of the grid-connected unit. For example, if it is detected that the grid-connected unit is in an on state, it is determined that the inverter is in a grid-connected state, that is, when the grid-connected switches K1 to K3 are all closed, the inverter is in a grid-connected state; otherwise, it is in a non-grid-connected state, that is, when the grid-connected switches K1 to K3 are all disconnected, the inverter is in a non-grid-connected state.

[0035] It should be noted that in other examples, the power grid system may be a TT or TN system. Figure 2 On the basis shown in the figure, a filter capacitor can be added between the common point of the filter capacitor and the ground.

[0036] Figure 3 A circuit diagram of another inverter provided in an embodiment of the present application.

[0037] like Figure 3 As shown, Figure 2 The difference in the example is that any of the three filter capacitors in the filter unit is connected between two phases; for example, the filter capacitor C1 is connected between the first phase and the second phase, the filter capacitor C2 is connected between the second phase and the third phase, and the filter capacitor C3 is connected between the first phase and the third phase.

[0038] and Figure 2 The difference is that in the filter unit, each phase is connected in series with at least one controllable switch, so that there is at least one controllable switch on the capacitive device branch between any two phases. Taking the figure as an example, one end of the filter capacitor C1 is connected to the first phase, and the other end is connected to the second phase through the controllable switch S1; one end of the filter capacitor C2 is connected to the second phase, and the other end is connected to the third phase through the controllable switch S2; one end of the filter capacitor C3 is connected to the first phase, and the other end is connected to the third phase through the controllable switch S3.

[0039] and Figure 2 Similarly, if the inverter is in a grid-connected state, the controllable switches S1, S2 and S3 are controlled to be closed; if the inverter is in a non-grid-connected state, the controllable switches S1, S2 and S3 are controlled to be opened.

[0040] Figure 4 A circuit diagram of another inverter provided in an embodiment of the present application.

[0041] like Figure 4 As shown, Figure 2 The difference is that resistors are connected in parallel at both ends of the filter capacitor. Taking the figure as an example, resistor R1 is connected in parallel at both ends of the filter capacitor C1, resistor R2 is connected in parallel at both ends of the filter capacitor C2, and resistor R3 is connected in parallel at both ends of the filter capacitor C3.

[0042] The parallel resistor can accelerate the discharge speed of the capacitor, so that after the system switch is disconnected, the capacitor can quickly release the residual voltage to a safe voltage range.

[0043] Figure 5 This is a schematic diagram of a control method for an inverter provided in an embodiment of the present application. The inverter can refer to the above content and will not be described in detail here.

[0044] The method comprises the steps of:

[0045] S11, detecting whether the inverter is in a grid-connected state;

[0046] S12. If the inverter is in a grid-connected state, all controllable switches are controlled to be closed; if the inverter is in a non-grid-connected state, at least one controllable switch on a capacitive device branch between any two phases is controlled to be opened.

[0047] In one example, the on or off state of the grid-connected unit is detected to determine whether the inverter is in a grid-connected state.

[0048] In one example, the grid-connected unit is controlled to be in an on or off state.

[0049] The preferred embodiments of the present application are described above with reference to the accompanying drawings, but the scope of the present application is not limited thereby. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present application shall be within the scope of the present application.

Claims

1. An inverter, characterized in that: It comprises an inverter unit, a grid-connected unit and a filter unit, wherein the output end of the inverter unit is connected to the grid through the grid-connected unit and the filter unit in sequence; The filtering unit includes a capacitive device, and there is at least one controllable switch on the capacitive device branch between any two phases; The capacitive device includes a first capacitive device, a second capacitive device and a third capacitive device, and the controllable switch includes a first controllable switch and a second controllable switch; one end of the first capacitive device is connected to a first phase of the three-phase power grid, and the other end of the first capacitive device is connected to a common point through the first controllable switch; one end of the second capacitive device is connected to a second phase of the three-phase power grid, and the other end of the second capacitive device is connected to a common point through the second controllable switch; one end of the third capacitive device is connected to a third phase of the three-phase power grid, and the other end of the third capacitive device is connected to a common point; or, One end of the capacitive device is connected to a first phase among the three phases of the power grid, and the other end of the capacitive device is connected to a second phase among the three phases of the power grid through the controllable switch.

2. The inverter according to claim 1, characterized in that: Also includes a control unit; The control unit is configured to detect whether the inverter is in a grid-connected state. If the inverter is in a grid-connected state, all controllable switches are controlled to be closed; if the inverter is in a non-grid-connected state, at least one controllable switch on a capacitive device branch between any two phases is controlled to be disconnected.

3. The inverter according to claim 2, characterized in that: The control unit is configured to determine whether the inverter is in a grid-connected state by detecting an on or off state of the grid-connected unit.

4. The inverter according to claim 1, characterized in that: Also included is a resistor connected in parallel with the capacitive device.

5. The inverter according to claim 1, characterized in that: The controllable switch includes at least one of a relay, a contactor, a circuit breaker, and a semiconductor switch.

6. The inverter according to claim 1, characterized in that: The grid-connected unit includes a grid-connected switch.

7. The inverter according to claim 6, characterized in that: The grid-connected switch includes a relay.

Images