CN210350806U

CN210350806U - Routing relay circuit on alternating current side of bidirectional AC/DC converter in energy storage inverter

Info

Publication number: CN210350806U
Application number: CN201921802607.6U
Authority: CN
Inventors: 曹凯; 吴怡; 黄健; 陈猛; 史亚圣; 茆健; 方宇; 曹松银; 夏晓南
Original assignee: State Grid Jiangsu Electric Power Co Ltd Yangzhou Power Supply Branch; State Grid Jiangsu Electric Power Co Ltd; Yangzhou University
Current assignee: State Grid Jiangsu Electric Power Co Ltd Yangzhou Power Supply Branch; State Grid Jiangsu Electric Power Co Ltd; Yangzhou University
Priority date: 2019-10-24
Filing date: 2019-10-24
Publication date: 2020-04-17
Anticipated expiration: 2029-10-24

Abstract

And a routing relay circuit on the alternating current side of the bidirectional AC/DC converter in the energy storage inverter. The utility model belongs to the technical field of power electronics and electricians; to a routing relay circuit on the AC side of a bi-directional AC/DC converter in a tank inverter. A routing relay circuit on the AC side of a bidirectional AC/DC converter in a power storage inverter which reduces the number of relays and facilitates the integration of a high power density power storage inverter is provided. The alternating current side of a bidirectional AC/DC converter in the energy storage inverter is connected with a routing relay circuit; the relay circuit comprises a relay K1, a relay K2 and a relay K3; the exchange side of two-way AC/DC converter among the energy storage inverter connects the input of two normally open contacts of relay K1, the output of two normally open contacts of relay K1 divide into electric wire netting branch road and back-up load branch road, the utility model provides a route relay and control method thereof not only can use in photovoltaic energy storage inverter, also can use in wind power generation energy storage equipment.

Description

Routing relay circuit on alternating current side of bidirectional AC/DC converter in energy storage inverter

Technical Field

The utility model belongs to the technical field of power electronics and electricians; the invention relates to a route relay circuit on the alternating current side of a bidirectional AC/DC converter in an energy storage inverter, in particular to a circuit for forming a route relay through which energy passes and a control method of the route relay circuit under the mode that a photovoltaic energy storage inverter supplies power for a backup load.

Background

In a photovoltaic energy storage inverter system, a bidirectional AC/DC converter circuit on a grid side can realize energy transmission from a direct current bus to a power grid or from the power grid to the direct current bus, that is, a bidirectional energy transmission function is realized, however, a relay network is required for the bidirectional AC/DC converter to connect an alternating current side thereof with the power grid and a load, and the relay network is properly controlled to realize energy transmission as required to realize the function of an energy storage inverter, and the relay network is not called a routing relay circuit here.

In the photovoltaic energy storage inverter, for a routing relay circuit, in the prior art, a 6/12 relay network shown in fig. 2 is mainly adopted to form a photovoltaic energy storage inverter system, the number of relays is large, the integration of a high-power density energy storage inverter is not facilitated, the reliability of the routing relay circuit formed by a plurality of relays is poor, the cost is high, and the cost performance of the energy storage inverter is low.

SUMMERY OF THE UTILITY MODEL

The utility model provides a to above technical problem, provide a reduce relay quantity, be favorable to the route relay circuit of two-way AC/DC converter alternating current side among the energy storage inverter of high power density energy storage inverter integration.

The technical scheme of the utility model is that: the alternating current side of a bidirectional AC/DC converter in the energy storage inverter is connected with a routing relay circuit; the relay circuit comprises a relay K1, a relay K2 and a relay K3;

the alternating current side of a bidirectional AC/DC converter in the energy storage inverter is connected with the input ends of two normally open contacts of the relay K1, the output ends of the two normally open contacts of the relay K1 are divided into a power grid branch and a backup load branch,

the power grid branch circuit is as follows: the output ends of the two normally open contacts of the relay K1 are connected with the input ends of the two normally open contacts of the relay K2, and then are connected to a power grid and a general load through the output ends of the two normally open contacts of the relay K2;

the backup load branch is as follows: the output ends of the two normally open contacts of the relay K1 are connected with the input ends of the two normally open contacts of the relay K3 and then are connected to a backup load through the output ends of the two normally open contacts of the relay K3;

and the direct current side of the bidirectional AC/DC converter is connected with a direct current bus.

The relay K1, the relay K2 and the relay K3 are relays with two groups of normally open contacts,

or two relays with a group of normally open contacts.

Compared with the prior art, the beneficial effects of the utility model reside in that, to the route relay that the alternating current side of two-way AC/DC circuit is connected among the photovoltaic energy storage inverter, the more expensive, low reliability and the control that lead to of quantity are complicated, are unfavorable for the integrated shortcoming of high power density, have provided route relay circuit and the control method that quantity is halved. The hardware self-checking function required in the demonstration of the energy storage inverter can be realized, and the performance requirement of energy transmission of the energy storage inverter can be realized. The utility model discloses owing to adopted less relay quantity, can effectual reduce cost and the volume of device, improve reliability, power density and obtain the high price/performance ratio. The utility model provides a route relay and control method thereof not only can use in photovoltaic energy storage dc-to-ac converter, also can use in wind power generation energy storage equipment. The advantages of the present invention will still be explained in the following statements.

Drawings

FIG. 1 is a schematic diagram of the present invention,

figure 2 is a schematic diagram of a prior art (current) implementation,

figure 3 is a schematic diagram of the implementation of the invention,

figure 4 is a schematic view of an example of the application of the present invention in a photovoltaic energy storage system,

FIG. 5 shows experimental waveforms of grid-connected power generation and load access when the grid is normal,

figure 6 shows experimental waveforms 1 when the grid of the application example of the present invention is disconnected,

figure 7 shows experimental waveform 2 when the grid of the application example of the present invention is disconnected,

figure 8 experimental waveform 1 for recovery of the power grid according to the embodiment of the present invention,

figure 9 shows experimental waveform 2 for recovery of the power grid of the present invention,

figure 10 experimental waveforms of the grid from normal to disconnected to restoration process of the utility model application example,

figure 11 shows a battery charging and discharging experimental waveform 1 when the PV module is not connected to the application example of the present invention,

figure 12 shows the experimental waveform 2 of the battery charge/discharge without the PV module in the embodiment of the present invention,

symbol names in fig. 1: 1 is an energy storage inverter, and 2 is a routing relay circuit;

the Vbus dc bus voltage is then applied,

k1, K2 and K3 are normally open contacts of the relay in the routing relay circuit,

the L-shaped firing line is connected with the L-shaped firing line,

and (4) an N zero line.

Symbol names in fig. 2:

k3, K4, K5 and K6 are normally open contacts of the relay in the routing relay circuit;

other symbols are the same as those in FIG. 1.

The symbol names in fig. 3 are the same as those in fig. 1 and 2.

Symbol names in fig. 4:

the alternating side current of the iac bidirectional AC/DC converter,

the alternating side current of the vac bidirectional AC/DC converter,

the current of the ig net side is measured,

the voltage of the grid in vg,

the voltage of the photovoltaic voltage of the VPV,

the Vbat is the voltage of the energy storage battery,

the current of the Ibat energy storage battery,

the voltage on the Vb back-up load,

vr1, Vr2, Vr3 relays K1, K2 and K3.

The symbol names in fig. 5 to 12 are the same as those in fig. 4 and 1.

Detailed Description

As shown in fig. 1, 3 and 4, the AC side of the bidirectional AC/DC converter in the energy storage inverter is connected to the routing relay circuit; the relay circuit comprises a relay K1, a relay K2 and a relay K3;

or two relays with a group of normally open contacts.

The control method of the utility model comprises the following steps,

a) when the energy storage inverter performs self-checking on the relays, the relays K2 and K3 are combined to detect whether the contacts of the relays have short-circuit faults or open-circuit faults, and the relays K1 and K2 are combined to detect whether the contacts of the relays have short-circuit faults or open-circuit faults;

b) when the energy storage inverter works normally and supplies power for the backup load, the method comprises the following steps:

1) when the PV assembly generates power to the power grid, the wires of the relays K1 and K2 are controlled to be electrified, so that the normally open contacts of the relays K1 and K2 are controlled to be closed, and energy of the PV assembly is transmitted to the power grid through the bidirectional AC/DC converter; when grid-connected power generation is stable, a coil of the relay K3 is controlled to be electrified, so that a normally open contact of the relay K3 is controlled to be closed to supply power to a backup load;

2) on the basis of the work of the step 1), when the power grid is switched from normal work to failure, controlling the coil of the relay K2 to lose power, so as to control the normally open contact of the relay K2 to be released from closed, controlling the coils of the relays K1 and K3 to be kept powered to control the normally open contacts to be closed, and transmitting the energy of the direct current bus to a backup load through the bidirectional AC/DC converter;

3) on the basis of the work of the step 2), after the power grid is recovered to be normal from a fault, controlling the coil of the relay K1 to lose power, and controlling the coil of the relay K2 to be electrified so as to control the normally open contact of the relay K1 to be released from a closed state, and controlling the normally open contact of the relay K2 to be closed, so that the power supply of the power grid for a backup load is realized; after the time delay of X1 seconds, controlling the coil of the relay K1 to be electrified so as to control the closing of the normally open contact of the relay K1, realizing that the energy of the photovoltaic module is transmitted to a power grid through the bidirectional AC/DC converter and supplying power to a backup load;

when the energy storage battery needs to be charged and only the power grid exists, the wire of the relays K1, K2 and K3 is controlled to be electrified, so that the normally open contacts of the relays K1, K2 and K3 are controlled to be closed, the power grid is supplied to a backup load, and the power grid energy is transmitted to the direct current bus through the bidirectional AC/DC converter.

The following describes the embodiments of the present invention with reference to the accompanying drawings 1-12,

the national power grid puts forward high standard requirements on the safety and reliability of the energy storage inverter, the hardware of the system needs to be self-checked before the system works normally, and the system can work normally when no fault exists. Fig. 2 shows that energy storage inverter 1 system architecture constitutes, and photovoltaic module passes through the MPPT controller and exports direct current bus (Vbus), and energy storage battery connects direct current bus (Vbus) through two-way charge-discharge circuit on, and two-way AC/DC converter is connected to direct current bus (Vbus), and two-way AC/DC converter passes through the utility model discloses a route relay circuit 2 connects electric wire netting and back-up load. When the photovoltaic module generates sufficient energy, the energy can be sent to the power grid through the MPPT controller, the bidirectional AC/DC converter and the routing relay circuit 2 of the utility model to supply power for the load, and meanwhile, the energy is charged for the energy storage battery through the battery bidirectional charging and discharging circuit; when the power generation energy of the photovoltaic module is insufficient to supply power to the load, the energy storage battery transmits the energy to a direct current bus (Vbus) through a bidirectional charge-discharge circuit, and then supplies power to the load through a bidirectional AC/DC circuit and a routing relay circuit 2 of the utility model; when there is not photovoltaic module or overcast and rainy weather, the energy of electric wire netting is through the utility model discloses a two-way AC/DC converter is sent to route relay circuit 2, and two-way AC/DC converter operation this moment is in the rectification state, sends the energy of electric wire netting to direct current bus, charges for the battery through two-way charge-discharge circuit again.

For the routing relay circuit, as shown in fig. 2, a relay K1 is connected in series with a relay K2, a relay K3 is connected in series with a relay K4, and a relay K5 is connected in series with a relay K6. Before the energy storage inverter 1 works normally, the relays in the routing relay circuit 2 need to be subjected to self-checking, taking a serial branch of the relay K1 and the relay K2 as an example, the coil of the relay K1 is not controlled to be powered on first, and the coil of the relay K2 is not powered off, so that two normally open contacts of the relay K1 are controlled to be closed, the normally open contact of the relay K2 is in an open state, and if the voltage of the alternating current output side of the bidirectional AC/DC converter detected at the moment is close to the voltage of a power grid, the fact that the normally open contact of the relay K2 has a short-circuit fault is indicated; after a period of time delay, the coil of the relay K1 is controlled to lose power, the coil of the relay K2 is powered on, so that two normally open contacts of the relay K1 are controlled to be switched off from closed, the normally open contact of the relay K2 is controlled to be switched on from open, and if the detected voltage of the alternating current output side of the bidirectional AC/DC converter is close to the voltage of a power grid, the short-circuit fault of the normally open contact of the relay K1 is indicated; after a time delay, the coils of the control relays K1 and K2 are all powered on, so that the normally open contacts of the control relays K1 and K2 are closed, and if the voltage of the alternating current output side of the bidirectional AC/DC converter is detected to be close to 0 and the voltage of the grid side is normal, that is, the voltage of the alternating current output side of the bidirectional AC/DC converter is detected to be greatly different from the voltage of the grid side, the situation shows that the open-circuit fault occurs on the contacts of the relays K1 or K2. The method for detecting whether the hardware of the branch relays K3 and K4 and the branch relays K5 and K6 of the relay network has faults is the method for detecting the serial branches of the relay K1 and the relay K2. The controller has the possibility of controlling the routing relay circuit to perform the energy transfer task if the short circuit and open circuit faults described above do not occur.

It is also this requirement set forth by the national grid's demonstrated standards that renders the current routing relay circuit 2 and its control quite complex. Therefore, the utility model provides a circuit network of less relay constitutes route relay circuit 2 in energy storage inverter 1, as shown in figure 1.

As shown in fig. 1 and 3: the energy storage inverter 1 is composed of an MPPT controller, a battery bidirectional charge-discharge circuit, a bidirectional AC/DC converter and a routing relay circuit 2, the energy storage inverter 1 is generally provided with 4 ports which are respectively connected with a PV assembly, an energy storage battery, a power grid and a backup load, and a local general load is connected with the power grid in parallel, so that the general load is not drawn in figure 1, and the connection relation and the control method of the routing relay circuit 2 are not influenced. In fig. 1, the output of the MPPT controller, the high voltage side of the battery during bidirectional charging and discharging, and the DC side of the bidirectional AC/DC converter are all connected in parallel to the DC bus (Vbus), and the AC side of the bidirectional AC/DC converter is connected to the routing relay circuit 2.

As shown in fig. 1 and 3, the connection relationship of the routing relay circuit 2 in the energy storage inverter 1 of the present invention is described as follows: the alternating current side of a bidirectional AC/DC converter in the energy storage inverter 1 is connected to the input ends of two normally open contacts of a relay K1, the output ends of the two normally open contacts corresponding to a K1 are divided into two branches, one branch is connected with the input ends of the two normally open contacts of the relay K2, the output ends of the two normally open contacts corresponding to the K2 are connected to a power grid and a general load, the other branch is connected to the input ends of the two normally open contacts of the relay K3, and the output ends of the two normally open contacts corresponding to the K3 are connected to a backup load. The direct current side of the bidirectional AC/DC converter is connected with a direct current bus, and the alternating current side of the bidirectional AC/DC converter is connected with a routing relay circuit 2. The coil of the relay is provided with a current loop by a common emitter amplifying circuit formed by triodes, the base of the triode is provided with a control signal by a controller, when the control signal is at a high level, the triode is in saturation conduction to enable the coil of the relay to be electrified, then the normally open contact of the relay is closed, and when the control signal is at a low level, the triode is cut off to enable the coil of the relay to be deenergized, then the normally open contact of the relay is disconnected.

The routing relay circuit 2 in fig. 1 and 3 adopts 3 relays with two sets of normally open contacts, and the relays K1, K2, and K3 can also be formed by combining two relays with one set of normally open contacts, that is, the routing relay circuit 2 can also be formed by 6 relays with one set of normally open contacts. Compare with current relay circuit network as in fig. 2, the utility model discloses a route relay circuit 2 has a half less relay quantity, obviously can reduce energy storage inverter 1's cost, helps the improvement of reliability and the promotion of power density.

The utility model discloses a control method of route relay circuit 2 divides two kinds of modes of energy storage system hardware self-checking and normal work to combine fig. 1 and fig. 3 to describe as follows:

(a) when the energy storage inverter 1 is used for self-checking the relays, the relays K2 and K3 are combined to detect whether the contacts of the relays have short-circuit faults or open-circuit faults, and the relays K1 and K2 are combined to detect whether the contacts of the relays have short-circuit faults or open-circuit faults.

The controller sends out a control signal to control the coil of the relay K2 to be electrified and the coil of the relay K3 to be deenergized, so that the normally open contact of the relay K2 is controlled to be closed, the normally open contact of the relay K3 is controlled to be opened, the detected voltage of the grid side power grid is close to the voltage of the backup load port, and the fact that the contact of the relay K3 has a short-circuit fault is indicated; after a period of time delay, the coil of the relay K2 is controlled to lose power, and the coil of the relay K3 is controlled to be powered on, so that the normally open contact of the relay K2 is controlled to be disconnected, the normally open contact of the relay K3 is controlled to be closed, and the detected voltage of the grid side power grid is close to the voltage of the backup load port, so that the fact that the contact of the relay K2 has a short-circuit fault is indicated; after a period of time delay, the coils of the control relays K2 and K3 are all powered on, so that the normally open contacts of the control relays K2 and K3 are both closed, and if the detected grid side grid voltage is greatly different from the voltage of the backup load port, it is indicated that the contact of the relay K2 or K3 has an open-circuit fault.

The method for detecting and judging whether the short-circuit fault and the open-circuit fault occur to the contacts of the relay K1 and the relay K2 in combination is the same as the method for detecting the relays K2 and K3, and is also the same as the method for detecting the relays K1 and K2 in the conventional routing relay circuit 2 in FIG. 2, so the description is omitted.

(b) When the energy storage inverter 1 works normally and supplies power for a backup load:

1) when the PV assembly generates power to a power grid, controlling the coils of relays K1 and K2 in FIGS. 1 and 3 to be electrified so as to control the normally open contacts of relays K1 and K2 to be closed, transmitting the energy of the PV assembly to a direct current bus Vbus through an MPPT controller, and transmitting the energy of the PV assembly to the power grid through the bidirectional AC/DC converter by adopting current type grid connection control; when grid-connected power generation is stable (after a period of time delay), the coil of the relay K3 is controlled to be electrified, so that the normally open contact of the relay K3 is controlled to be closed to supply power to a backup load;

2) on the basis of 1) working, when the power grid is switched from normal working to fault (if the power grid is powered off), the controller sends an instruction to control the power loss of a coil of the relay K2, so that the normally open contact of the relay K2 is controlled to be released from closing, namely the normally open contact of the relay K2 is disconnected with the power grid; the controller sends out a command to control the coil of the relay K1 and the relay K3 to be kept electrified so as to control the normally open contact of the relay K1 and the normally open contact of the relay K3 to be closed, and at the moment, the energy of the direct current bus Vbus is sent to a backup load through the bidirectional AC/DC converter. Under the mode, the bidirectional AC/DC converter is switched from current type grid-connected control to voltage type off-grid inversion control; in this mode, the backup load may be powered by the PV module, or the energy storage cell and the PV module together via a relay circuit.

3) On the basis of 2) working, after the power grid is recovered to be normal from a fault, the controller sends a command to control the coil of the relay K1 to lose power, the coil of the relay K2 is electrified, so that the normally open contact of the relay K1 is controlled to be released from being closed (namely the normally open contact is disconnected), the normally open contact of the relay K2 is closed, at the moment, the power supply of the backup load by the power grid is realized, the bidirectional AC/DC converter stops the control of voltage type off-grid inversion, and a switching tube pulse control signal of the bidirectional AC/DC converter is blocked; after the time delay of X1 seconds, controlling the coil of the relay K1 to be electrified so as to control the closing of the normally open contact of the relay K1, and realizing current type grid connection control of the bidirectional AC/DC converter by a controller so as to realize that the energy of the photovoltaic module is transmitted to a direct current bus through the MPPT controller, then transmitted to a power grid through the bidirectional AC/DC converter and simultaneously supplied to a backup load;

4) when the energy storage battery needs to be charged and only a power grid exists, the controller sends out an instruction to control the wire packages of the relays K1, K2 and K3 to be electrified, so that the normally open contacts of the relays K1, K2 and K3 are controlled to be closed, the power supply of the power grid to a backup load is realized, the energy of the power grid is transmitted to a direct current bus Vbus through the bidirectional AC/DC converter, and the energy storage battery is charged through the battery bidirectional charging and discharging circuit in the figure 3.

The utility model discloses a control method of route relay circuit 2 has realized photovoltaic energy storage inverter 1 and has carried out the functional requirement that charges for the energy storage battery by the electric wire netting energy for the backup load power supply, compares with prior art in fig. 2, has less relay and constitutes (the relay that has a little less in quantity), therefore the utility model discloses a control method is simple, and the reliability is promoted.

In the application example of the utility model circuit shown in fig. 4, compared with fig. 3, the output of the energy storage inverter 1 has access to a general load, which is connected in parallel with the grid, i.e. when there is power on the grid side, the general load will be powered on, and when the grid is powered off, the general load will be powered off. The main parameters and configurations of fig. 4 are as follows: the relays K1, K2 and K3 are all Tycor relays T92P7D12-12, the coil voltage of the relays is 12V, and the relays are provided with two groups of normally open contacts. The maximum power of the energy storage inverter is 4.6KW, the voltage Vbus (high-voltage direct-current side) of a direct-current bus is =400V, the voltage of an energy storage battery is 45V-63V, the MPPT voltage range of the PV assembly is 200V-440V, the alternating-current side outputs 23A of alternating current, and the rated voltage of a power grid is 230V/50 Hz. General IO ports GPIO17, GPIO16 and GPIO30 of a DSP with a model number of TMS320F28035 of TI company generate routing relay control signals Vr1, Vr2 and Vr3, and then power is supplied to coils of relays K1, K2 and K2 through corresponding drive 1, drive 2 and drive 3 circuits. GPIO17 is configured in controller TMS320F28035, GPIO16 and GPIO30 are output IO ports, and are initialized to low level, Vr1 output by corresponding GPIO ports is controlled according to function requirements, when Vr2 and Vr3 are low level, corresponding relays K1, K2 and K3 are electrified, so that normally open contacts of relays K1, K2 and K3 are controlled to be closed, otherwise when Vr1, Vr2 and Vr3 are high level, normally open contacts of relays K1, K2 and K3 are controlled to be opened. After the energy storage inverter 1 is powered on, the initialization program in the DSP controller sets the control signals Vr1, Vr2 and Vr3 of all relays in the routing relay circuit 2 to high level, so as to control the power loss of the coils of K1, K2 and K3, and make the normally open contacts of the coils in a release state.

The maximum power point of a PV component accessed by the energy storage inverter 1 is set to be 250V, the maximum power is set to be 1500W (realized by a photovoltaic analog power supply), the energy storage inverter 1 is accessed into a back-up load and a power grid (normal power grid), a general load is connected to a power grid terminal in parallel, and the general load and the back-up load are both configured to be 1100W. As shown in fig. 5, the channel 1 (CH 1) is a grid voltage waveform and a voltage waveform on a general load, CH2 is a voltage waveform on a backup load, CH3 is a driving waveform of a battery side (low voltage side) switch tube of the battery bidirectional charge and discharge circuit, and CH4 is a dc bus voltage Vbus waveform. Because the power grid is firstly added when the power grid is started and then the PV component is accessed, the initial stage of the direct current bus voltage in the waveform is provided by an uncontrolled rectifier bridge circuit of a power grid auxiliary power supply (Vbus is 318V), the corresponding time when the power grid is just accessed is set to be 0 for analysis and convenience, the MPPT controller boosts the voltage to establish the direct current bus voltage to 380V after 14 seconds of delay, when the DSP controller detects that the direct current bus voltage is more than 370, the controller firstly selects the relays K1 and K2 in the relay circuit 2 as a group for self-checking, then selects the relays K2 and K3 as a group for self-checking, and after the relays are confirmed to have no open circuit or short circuit fault, the controller controls the coil of the relay K3 to lose power so as to control the normally open contact of the relay K3 to be disconnected; the controller controls the coils of the K1 and the K2 to be electrified, so that the normally open contacts of the K1 and the K2 are controlled to be closed, the MPPT controller runs an MPPT tracking program to realize current type grid-connected power generation of the bidirectional AC/DC converter, stable grid-connected power generation is realized through the bidirectional AC/DC converter when 43 seconds pass, the voltage of a direct current bus after grid connection is stabilized at 370V, and when 50.5 seconds pass, the DSP controller controls the coils of the relay K3 to be electrified, so that the normally open contacts of the relay K3 are controlled to be closed to supply power for a backup load. According to the experimental waveform 5 and analysis, the backup load is supplied with power by controlling the normally open contact of the relay K3 to be closed through the DSP after the energy storage inverter 1 is stably connected to the grid for power generation.

The experimental waveforms obtained in the above grid-connected operation mode when the grid is disconnected (grid fault) without adding an energy storage battery are as shown in fig. 6 and 7. In fig. 6, CH1 is the grid voltage waveform, CH2 is the voltage waveform on the backup load, CH3 is the dc bus voltage waveform, and CH4 is the grid side current waveform; in fig. 7, CH1 is a relay K2 control signal Vr2 output from an IO port GPIO16 of the controller DSP TMS320F28035, CH2 is a voltage waveform on the backup load, CH3 is a voltage waveform on the line of the grid-side relay K2, and CH4 is a grid-side current waveform.

As can be seen from fig. 6 and 7, after the system stably operates, the grid voltage is cut off, the controller (DSP TMS320F 28035) outputs a control signal to make the line of the grid-side relay K2 lose power, so as to control the normally open contact of the relay K1 and the normally open contact of the relay K3 to be opened from closed, the photovoltaic energy storage inverter 1 is controlled by the controller to switch into the off-grid voltage type output mode, so that the backup load realizes the uninterrupted power supply, and at this time, the general load loses power. Experiments show that when the power grid is powered off, the energy storage inverter transmits the energy of the photovoltaic module to the direct current bus through the MPPT controller, and then the energy storage inverter generates inverter voltage through the voltage type control of the bidirectional AC/DC converter to provide energy for a backup load. As can be seen from the CH2 experimental waveforms of fig. 6 and 7, during the power-off switching process, the power-off time of the backup load is less than 10ms, so uninterrupted power supply of the backup load is realized through the routing relay circuit 2.

When the grid is restored, fig. 8 and 9 show experimental switching waveforms, where CH1 in fig. 8 is the grid voltage waveform, CH2 is the voltage waveform on the backup load, CH3 is the dc bus voltage, and CH4 is the grid side current waveform. The energy storage inverter corresponding to the experiment in fig. 8 does not have a general load, and it is seen from fig. 8 that when the grid is restored, the voltage on the backup load does not substantially fluctuate; the energy storage inverter 1 corresponding to the experiment of fig. 9 is connected with a general load (the general load is connected with a power grid in parallel), in fig. 9, CH1 is the voltage on a coil of an alternating current side relay K1 of a bidirectional AC/DC converter, CH2 is the voltage on a backup load, CH3 is the voltage on a coil of a power grid side relay K2, and CH4 is a power grid side current waveform. When the grid side has current, the time is 0 (indicating that the energy storage inverter is connected to the power grid), after about 10s of delay, the coil of the grid side relay K2 is electrified, so that the normally open contact of the grid side relay K2 is controlled to be closed, meanwhile, the coil of the alternating current side relay K1 of the bidirectional AC/DC converter is electrified, so that the normally open contact of the alternating current side relay K1 is controlled to be disconnected from closed, the voltage of the PV assembly becomes an open-circuit voltage value, the backup load is switched from power supply of the bidirectional AC/DC converter to power supply of the power grid, and therefore, the grid side current of the channel 4 in the graph 9 is increased. The 10s delay is actually the time required for the voltage type output voltage of the bidirectional AC/DC converter to track the phase of the power grid to realize the phase locking process when the power grid is recovered. From the absence of a significant change in the backup load voltage in fig. 8 and 9, it is known that the coil of relay K3 remains energized to control its normally open contacts to be closed; in order to realize that the normally open contact of the K1 can be rapidly switched from closed to open after the coil is not electrified, the coil voltage of the relay K1 in the application example of the figure 4 is controlled to be pulse voltage by a DSP controller.

Fig. 10 shows the switching experimental waveform of the whole process of the grid from normal to failure and recovery. CH1 in fig. 10 is the grid voltage, CH2 is the voltage across the backup load, CH3 is the dc bus voltage, and CH4 is the grid side current. The method comprises the steps of firstly connecting a power grid, then connecting PV, supplying power to a backup load by the power grid, setting the working time of an MPPT controller to be 0 moment, completing maximum power point tracking after 8 seconds, and controlling a coil of a relay K3 to be powered after delaying for a period of time, so that a normally open contact of a relay K3 is controlled to be closed, and power is supplied to the backup load; after about 21.5 seconds, the power grid is disconnected (the power grid fails), and the voltage still exists on the backup load, which indicates that the normally open contact of the controller control relay K3 is still closed at the moment; the grid is restored by 33 seconds, the current in CH4 indicating that the general load is powered by the grid; when 43 seconds, the normally open contact of the relay K2 is controlled to be closed, and the normally open contact of the relay K1 is controlled to be released, so that the power supply of a general load and a backup load is realized by a power grid, and the current of the power grid side in CH2 is increased; at 43 seconds, the wire of the control relay K1 is electrified, so that the normally open contact of the control relay K1 is closed again, the PV assembly runs a maximum power point tracking program through the MPPT controller, and as can be seen from the fact that the grid side current is reduced in CH4 in fig. 10, the general load and the backup load are simultaneously powered by the PV assembly energy and the grid energy. Therefore, after the power grid is restored and the backup load is supplied with power, the DSP controller controls the AC side relay K1 coil of the AC/DC converter to be powered again after a period of time delay, and therefore the PV assembly sends energy into the power grid again through the bidirectional AC/DC converter after passing through the MPPT controller.

In order to more effectively verify that the energy storage inverter 1 in the system in fig. 4 realizes the function of charging the energy storage battery by the power grid, the experiment is carried out without accessing a PV module, and the experimental waveforms in fig. 11 and fig. 12 are obtained. In fig. 11, CH1 is a grid voltage waveform, CH2 is a discharge and charge current waveform of the energy storage battery (positive values correspond to a discharge state and negative values correspond to a charge state), CH3 is a voltage waveform on the backup load, and CH4 is a bidirectional AC/DC converter bridge arm side voltage waveform. In fig. 12, CH1 is a grid voltage waveform, CH2 is a voltage waveform on the backup load, CH3 is a driving waveform of a battery-side switching tube in the battery bidirectional charging and discharging circuit (indicating that the energy storage battery is discharged when a driving pulse is present), and CH4 is a dc bus voltage waveform. From the experimental waveforms of CH1 and CH4 in fig. 11, if the time when the grid voltage exists is 0 time, it can be seen that no voltage waveform appears at the bridge arm side of the bidirectional AC/DC converter within 24s, which indicates that the grid is connected to the energy storage inverter for a certain period of time, the controller controls the power loss of the coils of the relays K1 and K2, that is, the normally open contacts thereof are open, and also indicates that the voltage at the initial stage of the DC bus voltage in fig. 12 is not from the uncontrolled rectification of the grid but from the rectified power supply branch in the grid-side auxiliary power supply; the controller in fig. 12 generates a driving signal on the low-voltage side at 24 seconds, the energy storage battery is discharged through the bidirectional charge and discharge circuit, so that the second-stage boosting of the direct-current bus is achieved, when the voltage of the direct-current bus is stable, self-checking is achieved through combination of the relays K1 and K2, self-checking is achieved through combination of the relays K2 and K3, when it is determined that the relays are not faulty, the controller controls the normally-open contacts of the relays K1 and K2 to be closed, so that a converter side voltage waveform shown in CH4 in fig. 11 is obtained, at the moment, the bidirectional AC/DC converter achieves current type grid connection, after the stability, the controller controls the bidirectional AC/DC converter to be switched into a rectifying working state according to the conditions of the battery at 61 seconds, the bidirectional charge and discharge circuit of the battery charges the energy storage battery, and therefore, a battery side current waveform measured by the CH2 in fig.. The bidirectional AC/DC converter during rectification transmits the energy of the power grid to the direct current bus through the closed normally open contacts of the relay K1 and the relay K2, and then charges the energy storage battery through the battery bidirectional charging and discharging circuit; from the voltage appearing on the backup load in fig. 11 and 12, it is known that when the bidirectional AC/DC converter starts rectifying operation, the controller controls the normally open contact of the relay K3 to close, thereby supplying power to the backup load.

From the above description, the utility model discloses a route relay circuit 2 of two-way AC/DC converter alternating current side and control method in energy storage inverter 1 only have two sets of normally open contact's relay or 6 relays that only have a set of normally open contact with 3, have just realized the energy transmission requirement in the single-phase energy storage inverter, the utility model discloses a method can be popularized and applied to three-phase energy storage inverter in order to found its net side route relay circuit.

The utility model has the advantages of it is following:

(1) the number of relays in the energy storage inverter 1 is greatly reduced;

(2) the feasibility and the power density are improved, the cost is reduced, and the cost performance is high;

(3) the inverter is not only suitable for a single-phase energy storage inverter, but also suitable for a three-phase energy storage inverter.

The present invention is not limited to the above embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some replacements and transformations for some technical features without creative labor according to the disclosed technical contents, and these replacements and transformations are all within the protection scope of the present invention.

Claims

1. The route relay circuit of the alternating current side of the bidirectional AC/DC converter in the energy storage inverter is characterized in that the alternating current side of the bidirectional AC/DC converter in the energy storage inverter is connected with the route relay circuit; the relay circuit comprises a relay K1, a relay K2 and a relay K3;

2. The routing relay circuit on the AC side of the bidirectional AC/DC converter in the energy storage inverter according to claim 1, wherein the relay K1, the relay K2 and the relay K3 are relays having two sets of normally open contacts,

or two relays with a group of normally open contacts.