CN115833206A - Energy storage conversion circuit, converter submodule and energy storage conversion system - Google Patents
Energy storage conversion circuit, converter submodule and energy storage conversion system Download PDFInfo
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Abstract
The application provides an energy storage converting circuit, converter submodule and energy storage converting system relates to energy storage converter technical field, and this circuit includes two level circuit of first H bridge and three level circuit of first H bridge, the first end of three level circuit of first H bridge is used for connecting the first phase of alternating current electric network, the second end of three level circuit of first H bridge is used for connecting two level circuit's of first H bridge first end, two level circuit's of first H bridge first end and energy storage unit are parallelly connected. Therefore, the combination of the H-bridge three-level circuit and the H-bridge two-level circuit replaces an H-bridge two-level circuit structure used in a traditional cascade energy storage system, and the influence of the cascade energy storage conversion system on the service life of the battery pack due to double-frequency fluctuation in the charging and discharging processes is avoided.
Description
Technical Field
The application relates to the technical field of energy storage converters, in particular to an energy storage conversion circuit, a converter submodule and an energy storage conversion system.
Background
When new energy such as wind power, photovoltaic and the like is used for power generation, the generated power has randomness and intermittence, and some challenges are brought to the safe and stable operation of a power grid. And this problem can be solved by providing a cascade type large capacity energy storage system.
However, the existing cascaded high-capacity energy storage system mostly adopts an H-bridge structure, which has more defects, and can cause the charge and discharge power of the battery to fluctuate at twice frequency, and the instantaneous active power fluctuation of the twice frequency can accelerate the service life attenuation of the battery pack; each H-bridge module needs one battery pack, and the number of the required battery packs is large; the H bridge is a two-level topological structure, the output harmonic wave is high, and the fluctuation of the charging and discharging current power is large.
Based on this, this application proposes a new kind of tank transform circuit.
Disclosure of Invention
In view of this, the present application provides an energy storage conversion circuit, which aims to solve the problem of high output current ripple and harmonic in the existing energy storage conversion circuit.
In a first aspect, the present application provides a tank converter circuit, including: a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
Optionally, the energy storage conversion circuit further includes:
the second H bridge two-level circuit, the second H bridge three-level circuit, the third H bridge two-level circuit, the third H bridge three-level circuit and the transformer;
the second end of the first H-bridge two-level circuit is connected with the primary winding of the transformer;
the first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and the second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
Optionally, a first switch is connected in series between a positive end of the first H-bridge three-level circuit and a negative end of the first end;
a second switch is connected in series between the positive end of the second H-bridge three-level circuit and the negative end of the second end;
and a third switch is connected in series between the positive end of the second end of the third H-bridge three-level circuit and the negative end of the second end.
Optionally, a second end of the first H-bridge three-level circuit is connected to a first dc support capacitor and a second dc support capacitor;
the first end of the second H-bridge three-level circuit is connected with a third direct-current supporting capacitor and a fourth direct-current supporting capacitor;
the first end of the third H-bridge three-level circuit is connected with a fifth direct-current support capacitor and a sixth direct-current support capacitor;
the first direct current support capacitor, the second direct current support capacitor, the third direct current support capacitor, the fourth direct current support capacitor, the fifth direct current support capacitor and the sixth direct current support capacitor are used for storing and releasing electric energy.
Optionally, a tap of a primary winding of the transformer is connected to a midpoint of the first dc support capacitor and the second dc support capacitor;
a tap of the first secondary winding of the transformer is connected with the middle point of the third direct current support capacitor and the fourth direct current support capacitor;
and a tap of the second secondary winding of the transformer is connected with the middle points of the fifth direct current support capacitor and the sixth direct current support capacitor.
Optionally, the first H-bridge three-level circuit is:
a first T-type H-bridge three-level circuit or a first active clamp I-type H-bridge three-level circuit;
the second H-bridge three-level circuit is as follows:
a second T-type H-bridge three-level circuit or a second active clamp I-type H-bridge three-level circuit;
the third H-bridge three-level circuit is:
a third T-type H-bridge three-level circuit or a third active clamp I-type H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first T-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second T-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third T-shaped H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first active clamp I-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second active clamp I-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third active clamp I-type H-bridge three-level circuit.
In a second aspect, the present application provides an energy storage converter sub-module comprising: a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
Optionally, the energy storage converter sub-module further includes a second H-bridge two-level circuit, a second H-bridge three-level circuit, a third H-bridge two-level circuit, a third H-bridge three-level circuit, and a transformer;
the second end of the first H-bridge two-level circuit is connected with the primary winding of the transformer;
the first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and the second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
Optionally, a first switch is connected in series between a positive terminal of a first end of the first H-bridge three-level circuit and a negative terminal of the first end;
a second switch is connected in series between the positive end of the second H-bridge three-level circuit and the negative end of the second end;
and a third switch is connected in series between the positive end of the second end of the third H-bridge three-level circuit and the negative end of the second end.
Optionally, a second end of the first H-bridge three-level circuit is connected to a first dc support capacitor and a second dc support capacitor;
the first end of the second H-bridge three-level circuit is connected with a third direct-current supporting capacitor and a fourth direct-current supporting capacitor;
the first end of the third H-bridge three-level circuit is connected with a fifth direct-current support capacitor and a sixth direct-current support capacitor;
the first direct current support capacitor, the second direct current support capacitor, the third direct current support capacitor, the fourth direct current support capacitor, the fifth direct current support capacitor and the sixth direct current support capacitor are used for storing and releasing electric energy.
Optionally, a tap of a primary winding of the transformer is connected to a midpoint of the first dc support capacitor and the second dc support capacitor;
a tap of the first secondary winding of the transformer is connected with the middle point of the third direct current support capacitor and the fourth direct current support capacitor;
and a tap of the second secondary winding of the transformer is connected with the middle points of the fifth direct current support capacitor and the sixth direct current support capacitor.
Optionally, the first H-bridge three-level circuit is:
a first T-type H-bridge three-level circuit or a first active clamp I-type H-bridge three-level circuit;
the second H-bridge three-level circuit is as follows:
a second T-type H-bridge three-level circuit or a second active clamp I-type H-bridge three-level circuit;
the third H-bridge three-level circuit is:
a third T-type H-bridge three-level circuit or a third active clamp I-type H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first T-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second T-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third T-shaped H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first active clamp I-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second active clamp I-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third active clamp I-type H-bridge three-level circuit.
In a third aspect, the present application provides an energy storage converter system comprising at least one energy storage converter sub-module, a reactor;
the energy storage converter sub-module is the energy storage converter sub-module of the second aspect;
and after the at least one energy storage converter submodule is cascaded, the at least one energy storage converter submodule is connected with an alternating current power grid through the reactor in a triangular connection or star connection mode.
Optionally, after the at least one energy storage converter submodule is cascaded, connecting the ac power grid through the reactor includes:
the first end of a first H-bridge three-level circuit of the energy storage converter submodule is connected with a first phase of an alternating current power grid through the reactor;
the second end of a second H-bridge three-level circuit of the energy storage converter submodule is connected with a second phase of an alternating current power grid through the reactor;
and the second end of a third H-bridge three-level circuit of the energy storage converter submodule is connected with a third phase of an alternating current power grid through the reactor.
The application provides an energy storage conversion circuit. The circuit comprises a first H-bridge two-level circuit and a first H-bridge three-level circuit, wherein a first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, a second end of the first H-bridge three-level circuit is used for being connected with a first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with an energy storage unit in parallel. Therefore, the combination of the H-bridge three-level circuit and the H-bridge two-level circuit replaces an H-bridge two-level circuit structure used in the traditional energy storage system, and the influence of the energy storage conversion system on the service life of the battery pack due to double-frequency fluctuation in the charging and discharging processes is avoided.
Drawings
To illustrate the technical solutions in the present embodiment or the prior art more clearly, the drawings needed to be used in the description of the embodiment or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic diagram of a typical topology of a cascaded energy storage converter according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of an energy storage conversion circuit according to an embodiment of the present disclosure;
fig. 3 is a schematic diagram of another tank converter circuit provided in the embodiment of the present application;
fig. 4 is a schematic diagram of another energy storage conversion circuit provided in the embodiment of the present application;
fig. 5 is a schematic diagram of another tank converter circuit according to an embodiment of the present application;
fig. 6 is a schematic diagram of an energy storage conversion system according to an embodiment of the present application;
fig. 7 is a schematic diagram of another energy storage conversion system according to an embodiment of the present application.
Detailed Description
The large-capacity centralized energy storage system not only can stabilize power fluctuation caused by large-scale access of new energy and assist in solving the problem of low electric energy ride through, but also can realize peak clipping, valley filling and peak-load and frequency modulation required by power grid dispatching. The typical topology of the existing cascade energy storage converter is shown in fig. 1, each phase of bridge arm of a cascade H-bridge battery energy storage converter (PCS) is formed by cascading N current transformation units based on an H-bridge, the direct current side of each H-bridge power unit is formed by connecting a battery energy storage unit and a capacitor in parallel, and each phase of bridge arm is connected to an alternating current power grid through a grid-connected reactance, so that the capacity expansion of the energy storage converter is realized, and the output power level of the energy storage converter is improved. The cascaded H-bridge converter is widely used due to its modular configuration, good harmonic characteristics and high efficiency. Meanwhile, because the H-bridge converter needs to provide an isolated direct current power supply for each H-bridge module, a plurality of battery units can be integrated to realize medium-high voltage operation.
However, in the prior art, the high-capacity energy storage converter is implemented by adopting a cascaded H-bridge manner, so that the charging and discharging power of the battery fluctuates at twice frequency, the fluctuation of the twice frequency instantaneous active power accelerates the life attenuation of the battery pack, and the H-bridge is of a two-level topological structure, so that the output harmonic wave is higher, and the charging and discharging current ripple is large. Based on the above disadvantages, the present application proposes a new circuit structure.
Referring to fig. 2, fig. 2 is a schematic diagram of an energy storage conversion circuit provided in the embodiment of the present application, including a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
The first end of the first H-bridge three-level circuit is connected to a first phase of an alternating current power grid through ports X1 and X2, a first switch is connected in series between the positive end of the first H-bridge three-level circuit and the negative end of the first H-bridge three-level circuit and serves as a bypass switch, the second end of the first H-bridge three-level circuit is connected with a first direct current supporting capacitor and a second direct current supporting capacitor and is used for storing and releasing electric energy, a tap of a primary winding of a transformer is connected with the middle points of the first direct current supporting capacitor and the second direct current supporting capacitor, the first end of the first H-bridge two-level circuit is connected with an energy storage unit in parallel to charge or discharge the energy storage unit, and the first T-type H-bridge three-level circuit or the first active clamping I-type H-bridge three-level circuit is used for realizing charging or discharging of the energy storage unit. When the first H-bridge three-level circuit is a first T-type H-bridge three-level circuit, the energy storage conversion circuit further includes electronic switches TXa1 to TXa4, TXb1 to TXb4, and TX9 to TX12, and the energy storage unit is charged or discharged by controlling the electronic switches to be turned on or off, and the specific operation mode is as follows:
first, an ideal switching function S is defined Ji As shown in formula (1):
U X is the voltage across ports X1 and X2, U 1 Is C 1 Capacitor voltage, U 2 Is C 2 Capacitor voltage, U N For the grid voltage, I N Is the grid current (the direction pointing to the grid is defined as the opposite direction). Each bridge arm has three equivalent states of 1,0 and-1, the two bridge arms have 9 switch combinations and 9 working modes, and the table below shows the working states of the T-shaped H-bridge three-level circuit.
Table 1: working state of T-shaped H-bridge three-level circuit
Working mode 1: (S) Xa ，S Xb ) = (1, 1), electronic switch T Xa1 ,T Xb1 On, other electronic switches off, port voltage U X ＝0。
The working mode 2 is as follows: (S) Xa ，S Xb ) = (1, 0), electronic switch T Xa1, T Xb3 ,T Xb4 Conducting, other electronic switches are disconnected, and the port voltage U X ＝U 1 Voltage U across the network side inductor L L ＝U N -U X ，U N Greater (less) than U 1 Time, net side current I N Will increase (decrease), I N In the forward (backward) direction, for the capacitor C 1 And charging (discharging) is carried out, and the capacitors C1 and C2 charge (discharge) the battery.
And (3) working mode: (S) Xa ，S Xb ) = 1, -1, electronic switch T Xa1 ,T Xb2 Conducting other electronic switches are disconnected, and the port voltage U is X ＝U 1 +U 2 Voltage U across the network side inductor L L ＝U N -U X Due to U N Less than U 1 +U 2 Time, net side current I N Will be gradually reduced by N When the direction is forward (reverse), the capacitors C1 and C2 are charged (discharged), and the capacitors C1 and C2 charge (discharge) the battery.
The working mode 4 is as follows: (S) Xa ，S Xb ) = (0, 1), electronic switch T Xa3 ,T Xa4 ,T Xb1 Conducting, other electronic switches are disconnected, and the port voltage U X ＝-U 1 Voltage U across the network side inductor L L ＝U N -U X ，U N Greater than (less than) -U 1 Time, net side current I N Will increase (decrease), I N In the forward (backward) direction, for the capacitor C 1 And discharging (charging), and the capacitors C1 and C2 discharge (charge) the battery.
The working mode 5 is as follows: (S) Xa ，S Xb ) = (0, 0), electronic switch T Xa3 ,T Xa4 ，T Xb3 ,T Xb4 Conducting other electronic switches are disconnected, and the port voltage U is X ＝0。
The working mode 6 is as follows: (S) Xa ，S Xb ) = 0, -1, electronic switch T Xa3 ,T Xa4 ,T Xb2 Conducting, other electronic switches are disconnected, and the port voltage U X ＝U 2 Voltage U across the network side inductor L L ＝U N -U X ，U N Greater (less) than U 1 Time, net side current I N Will increase (decrease), I N In the forward (backward) direction, for the capacitor C 2 Charging (discharging), the capacitors C1 and C2 charge (discharge) the battery.
Other modes of operation may be analyzed from table 1 and are not described in further detail herein.
When the first H-bridge three-level circuit is a first active clamp I-type H-bridge three-level circuit, referring to fig. 3, fig. 3 is a schematic diagram of another energy storage conversion circuit provided in the embodiment of the present application, and compared with fig. 2, the energy storage conversion circuit includes electronic switches TXa1 to TXa6, TXb1 to TXb6, and TX13 to TX16, and the energy storage unit is charged or discharged by controlling the electronic switches to be turned on or turned off, which specifically includes the following operation modes:
defining an ideal switching function S Ji As shown in formula (2):
U X is the voltage across ports X1 and X2, U 1 Is C 1 Capacitor voltage, U 2 Is C 2 Capacitor voltage, U N For the mains voltage, I N Is the grid current (the direction towards the grid is defined as the opposite direction). Each bridge arm has three equivalent states of 1,0 and-1, the two bridge arms have 9 switch combinations and 9 working modes, and the following table 2 shows three-level working states of the active clamp I-type H bridge.
Table 2: active clamp I type H bridge three-level working state
The working mode 2 is as follows: (S) Xa ，S Xb ) = (1, 0), electronic switch T Xa1 ,T Xa2 ,T Xa6 ,T Xb2 ,T Xb5 (or T) Xb3 ,T Xb6 ) Conducting, other electronic switches are disconnected, and the port voltage U X ＝U 1 Voltage U across the network side inductor L L ＝U N -U X Wherein U is N For mains voltage, U N Greater (less) than U 1 Time, net side current I N Will increase (decrease), I N In the forward (backward) direction, for the capacitor C 1 And charging (discharging) is carried out, and the capacitors C1 and C2 charge (discharge) the battery.
Working mode 3: (S) Xa ，S Xb ) = 1, -1, electronic switch T Xa1 ,T Xa2 ,T Xa6, T Xb3, T Xb4, T Xb5, Conducting other electronic switches are disconnected, and the port voltage U is X ＝U 1 +U 2 Voltage U across the network side inductor L L ＝U N -U X Wherein U is N Is the network voltage, due to U N Is less than U 1 +U 2 Time, net side current I N Will gradually decrease, I N When the direction is forward (reverse), the capacitors C1 and C2 are charged (discharged), and the capacitors C1 and C2 charge (discharge) the battery.
The working mode 6 is as follows: (S) Xa ，S Xb ) = 0, -1, electronic switch T Xa2 ,T Xa5 (or T) Xa3 ,T Xa6 ),T Xb3 ,T Xb4 ,T Xb5 Conducting, other electronic switches are disconnected, and the port voltage U X ＝U 2 Voltage U across the network side inductor L L ＝U N -U X Wherein U is N For mains voltage, U N Greater (less) than U 1 Time, net side current I N Will increase (decrease), I N In the forward (backward) direction, for the capacitor C 2 And charging (discharging) is carried out, and the capacitors C1 and C2 charge (discharge) the battery.
Other modes of operation may be analyzed from table 2 and are not described in further detail herein.
In another implementation manner of the embodiment of the present application, the energy storage conversion circuit further includes:
the second H bridge two-level circuit, the second H bridge three-level circuit, the third H bridge two-level circuit, the third H bridge three-level circuit and the transformer;
the second end of the first H-bridge two-level circuit is connected with the primary winding of the transformer;
the first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and the second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
Referring to fig. 4 and fig. 5, fig. 4 is a schematic diagram of another energy storage conversion circuit provided in the embodiment of the present application, and fig. 5 is a schematic diagram of another energy storage conversion circuit provided in the embodiment of the present application.
FIG. 4 is composed of three-phase symmetrical X-phase (electronic switches TXA 1-TXA 4, TXB 1-TXB 4, TX 9-TX 12), Y-phase (electronic switches TXA 1-TXA 4, TYB 1-TYB 4, TY 9-TY 12), Z-phase (electronic switches TZa 1-TZa 4, TZb 1-TZb 4, TZ 9-TZ 12), three-winding high-frequency transformer, DC support capacitors C1-C6, mechanical bypass switches K1-K3, etc., and the ports (B +, B-) are connected with the battery.
The transformer is a high-frequency isolation transformer, three windings are adopted, each winding is provided with a middle tap, a certain leakage inductance is designed, the middle tap is connected with the middle point of a capacitor, the high-frequency transformer and the H-bridge two-level unit can be equivalent to a bidirectional active DC/DC converter, power can be bidirectionally controlled between a T-shaped H-bridge three-level unit and a battery, and the high-frequency isolation transformer has an upper capacitor voltage-sharing function and a lower capacitor voltage-sharing function.
In fig. 5, the three-phase high-frequency transformer consists of three symmetrical X phases (electronic switches TXA 1-TXA 6, TXB 1-TXB 6 and TX 13-TX 16), Y phases (electronic switches TXA 1-TXA 6, TYB 1-TYB 6 and TY 13-TY 16), Z phases (electronic switches Tza 1-Tza 6, TZb 1-TZb 6 and TZ 13-TZ 16), a three-winding high-frequency transformer, DC support capacitors C1-C6, mechanical bypass switches K1-K3 and the like, and ports (B + and B-) are connected with the battery. The high-frequency isolation transformer adopts three windings, each winding is provided with a middle tap, a certain leakage inductance is designed, the middle tap is connected with the midpoint of a capacitor, the high-frequency transformer and the H-bridge two-level unit can be equivalent to a bidirectional active DC/DC converter, the power can be bidirectionally controlled between the active clamping I type H-bridge three level and a battery, and the high-frequency isolation transformer has the upper and lower capacitor voltage-sharing function.
The application also provides an energy storage converter submodule which comprises a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
In an implementation manner of the embodiment of the application, the energy storage converter submodule further comprises a second H bridge two-level circuit, a second H bridge three-level circuit, a third H bridge two-level circuit, a third H bridge three-level circuit and a transformer;
the second end of the first H-bridge two-level circuit is connected with the primary winding of the transformer;
a first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and a second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
In an implementation manner of the embodiment of the present application, a first switch is connected in series between a positive terminal of a first end of the first H-bridge three-level circuit and a negative terminal of the first end;
a second switch is connected in series between the positive end of the second H-bridge three-level circuit and the negative end of the second end;
and a third switch is connected in series between the positive end of the second end of the third H-bridge three-level circuit and the negative end of the second end.
In an implementation manner of the embodiment of the present application, a second end of the first H-bridge three-level circuit is connected to a first dc support capacitor and a second dc support capacitor;
the first end of the second H-bridge three-level circuit is connected with a third direct-current supporting capacitor and a fourth direct-current supporting capacitor;
a first end of the third H-bridge three-level circuit is connected with a fifth direct-current support capacitor and a sixth direct-current support capacitor;
the first direct current support capacitor, the second direct current support capacitor, the third direct current support capacitor, the fourth direct current support capacitor, the fifth direct current support capacitor and the sixth direct current support capacitor are used for storing and releasing voltage.
In an implementation manner of the embodiment of the present application, a tap of a primary winding of the transformer is connected to a midpoint of the first dc support capacitor and the second dc support capacitor;
a tap of the first secondary winding of the transformer is connected with the middle point of the third direct current support capacitor and the fourth direct current support capacitor;
and a tap of the second secondary winding of the transformer is connected with the middle points of the fifth direct current support capacitor and the sixth direct current support capacitor.
In an implementation manner of the embodiment of the present application, the first H-bridge three-level circuit is:
a first T-type H-bridge three-level circuit or a first active clamp I-type H-bridge three-level circuit;
the second H-bridge three-level circuit is as follows:
a second T-type H-bridge three-level circuit or a second active clamp I-type H-bridge three-level circuit;
the third H-bridge three-level circuit is:
a third T-type H-bridge three-level circuit or a third active clamp I-type H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first T-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second T-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third T-shaped H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first active clamp I-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second active clamp I-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third active clamp I-type H-bridge three-level circuit.
The application also provides an energy storage conversion system, which comprises at least one energy storage converter sub-module and a reactor.
After the at least one energy storage converter submodule is cascaded, the at least one energy storage converter submodule is connected with an alternating current power grid through the reactor in a triangular connection or star connection mode, and the specific connection mode is that the first end of a first H-bridge three-level circuit of the energy storage converter submodule is connected with the first phase of the alternating current power grid through the reactor;
the second end of a second H-bridge three-level circuit of the energy storage converter submodule is connected with a second phase of an alternating current power grid through the reactor;
and the second end of a third H-bridge three-level circuit of the energy storage converter submodule is connected with a third phase of an alternating current power grid through the reactor.
The specific connection mode is as shown in fig. 6 and 7, the X1 and X2 ports of all the energy storage converter sub-modules are cascaded to form an a phase, all the Y1 and Y2 terminals are cascaded to form a B phase, all the Z1 and Z2 terminals are cascaded to form a C phase, each SM sub-module is connected with a group of battery packs, and a system formed by a plurality of sub-module cascades and the battery packs can be directly connected through reactorsAnd the three-phase 10KV power grid is connected, the star connection is shown in figure 6, and the triangular connection is shown in figure 7. Under normal conditions, the mechanical bypass switches K1-K3 in each submodule are in an off state, and when the electronic switch T is in an off state x1 ～T x12 ，T y1 ～T t12 ，T z1 ～T z12 When a fault occurs, the mechanical bypass switches K1-K3 are closed, the fault sub-module is in a fault bypass state, and the rest other sub-modules are recombined to continue to operate. The connection mode of each submodule can be regarded as a three-phase H-bridge structure, and a three-phase static coordinate system (A, B, C) of three-phase alternating voltage and current can be converted into a direct current coordinate system (d, q) synchronously rotating at the frequency of a power grid fundamental wave through coordinate transformation. Three-phase network voltage U a 、U b 、U c Performing abc/dq conversion to obtain a direct current component U under a dq rotation coordinate system d 、U q The equation in dq coordinate system is:
three-phase current I a 、I b 、I c Performing abc/dq conversion to obtain DC component in dq rotation coordinate system
I d 、I q The equation in dq coordinate system is:
the power equation can be found as:
P＝U d *I d +U q *I q
Q＝U q *I d -U d *I q
in the formula, P is active power, Q is reactive power, and U is used d 、U q And I d 、I q The active power P and the reactive power Q are direct current, the charging and discharging power at the direct current side basically has no double frequency fluctuation under the condition of symmetrical power grid, and the charging and discharging rippleThe wave is very small.
Because the present cascade multilevel system connected to a 10KV power grid needs 45 sub-modules and 45 battery packs, the scheme needs fewer sub-modules and battery packs, the number of the battery packs is greatly reduced, and because each battery pack needs to be provided with a corresponding battery management system and an electric device, the number of the battery packs is reduced, and the cost and the occupied area of part of the battery systems can be saved. The structures in fig. 6 and 7 do not have power double frequency fluctuation, no extra power double frequency suppression strategy is needed, and the control strategy is simple.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus embodiment, since it is substantially similar to the method embodiment, it is relatively simple to describe, and reference may be made to some descriptions of the method embodiment for relevant points. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
It should be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
It should be further noted that, in the present specification, all the embodiments are described in a progressive manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the apparatus and device embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described embodiments of the apparatus and device are merely illustrative, and units described as separate components may or may not be physically separate, and components indicated as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The above description is only one specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A tank converter circuit, comprising: a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
2. The tank conversion circuit according to claim 1, further comprising:
the second H bridge two-level circuit, the second H bridge three-level circuit, the third H bridge two-level circuit, the third H bridge three-level circuit and the transformer;
the second end of the first H-bridge two-level circuit is connected with a primary winding of the transformer;
a first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and a second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
3. The tank conversion circuit according to claim 2, wherein a first switch is connected in series between a positive terminal of the first end of the first H-bridge three-level circuit and a negative terminal of the first end;
a second switch is connected in series between the positive end of the second H-bridge three-level circuit and the negative end of the second end;
and a third switch is connected in series between the positive end of the second end of the third H-bridge three-level circuit and the negative end of the second end.
4. The energy storage conversion circuit according to claim 2, wherein a first direct current support capacitor and a second direct current support capacitor are connected to a second end of the first H-bridge three-level circuit;
the first end of the second H-bridge three-level circuit is connected with a third direct-current supporting capacitor and a fourth direct-current supporting capacitor;
the first end of the third H-bridge three-level circuit is connected with a fifth direct-current support capacitor and a sixth direct-current support capacitor;
the first direct current support capacitor, the second direct current support capacitor, the third direct current support capacitor, the fourth direct current support capacitor, the fifth direct current support capacitor and the sixth direct current support capacitor are used for storing and releasing electric energy.
5. The tank converter circuit according to claim 4, wherein a tap of the primary winding of the transformer is connected to a midpoint of the first DC-support capacitor and the second DC-support capacitor;
a tap of the first secondary winding of the transformer is connected with the middle point of the third direct current support capacitor and the fourth direct current support capacitor;
and a tap of the second secondary winding of the transformer is connected with the middle points of the fifth direct current support capacitor and the sixth direct current support capacitor.
6. The tank conversion circuit according to claim 2, wherein the first H-bridge three-level circuit is:
a first T-type H-bridge three-level circuit or a first active clamp I-type H-bridge three-level circuit;
the second H-bridge three-level circuit is as follows:
a second T-type H-bridge three-level circuit or a second active clamp I-type H-bridge three-level circuit;
the third H-bridge three-level circuit is:
a third T-type H-bridge three-level circuit or a third active clamp I-type H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first T-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second T-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third T-shaped H-bridge three-level circuit;
when the first H-bridge three-level circuit is the first active clamp I-type H-bridge three-level circuit, the second H-bridge three-level circuit is the second active clamp I-type H-bridge three-level circuit; the third H-bridge three-level circuit is the third active clamp I-type H-bridge three-level circuit.
7. An energy storage converter submodule, comprising: a first H-bridge two-level circuit and a first H-bridge three-level circuit;
the first end of the first H-bridge three-level circuit is used for being connected with a first phase of an alternating current power grid, the second end of the first H-bridge three-level circuit is used for being connected with the first end of the first H-bridge two-level circuit, and the first end of the first H-bridge two-level circuit is connected with the energy storage unit in parallel.
8. The energy storage converter sub-module of claim 7, further comprising a second H-bridge two-level circuit, a second H-bridge three-level circuit, a third H-bridge two-level circuit, a third H-bridge three-level circuit, and a transformer;
the second end of the first H-bridge two-level circuit is connected with the primary winding of the transformer;
the first secondary winding of the transformer is connected with a first end of the second H-bridge two-level circuit, a second end of the second H-bridge two-level circuit is connected with a first end of the second H-bridge three-level circuit, and the second end of the second H-bridge three-level circuit is used for being connected with a second phase of the alternating current power grid;
and a second secondary winding of the transformer is connected with a first end of the third H-bridge two-level circuit, a second end of the third H-bridge two-level circuit is connected with a first end of the third H-bridge three-level circuit, and a second end of the third H-bridge three-level circuit is used for connecting a third phase of the alternating current power grid.
9. An energy storage converter system, characterized in that the system comprises at least one energy storage converter submodule, a reactor;
the energy storage converter sub-module is the energy storage converter sub-module of any one of claims 7 or 8;
and after the at least one energy storage converter submodule is cascaded, the at least one energy storage converter submodule is connected with an alternating current power grid through the reactor in a triangular connection or star connection mode.
10. The system of claim 9, wherein connecting the ac grid through the reactor after the at least one energy storage converter sub-module is cascaded comprises:
the first end of a first H-bridge three-level circuit of the energy storage converter submodule is connected with a first phase of an alternating current power grid through the reactor;
the second end of a second H-bridge three-level circuit of the energy storage converter submodule is connected with a second phase of an alternating current power grid through the reactor;
and the second end of a third H-bridge three-level circuit of the energy storage converter submodule is connected with a third phase of an alternating current power grid through the reactor.
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