WO2016015329A1

WO2016015329A1 - Dc-ac bi-directional power converter topology

Info

Publication number: WO2016015329A1
Application number: PCT/CN2014/083542
Authority: WO
Inventors: 冷再兴; 魏天魁
Original assignee: 冷再兴; 魏天魁
Priority date: 2014-08-01
Filing date: 2014-08-01
Publication date: 2016-02-04

Abstract

A DC-AC bi-directional power converter topology located between AC grid and DC storage battery implements charging and discharging between DC storage battery and AC grid. The topology comprises a bi-directional DC/DC converter circuit, a bi-directional DC/AC converter circuit, a DC filtering and protection circuit at high voltage side, a DC filtering capacitor at high voltage side, a detection circuit and a driving and control circuit. The bi-directional DC/DC converter circuit works as follows: when the DC storage battery is discharging, the voltage wave at high voltage side being a positive half wave varying sinusoidally, enabling DC/AC conversion part only to need to work in a power frequency state not in a high frequency pulse modulation state, and greatly reducing the switching consumption of the DC/AC bridge circuit. Meanwhile, a high frequency power transformer with high efficiency is adopted to implement conversion of the DC/DC part, developing the function of boosting, sinking and electrical isolation and greatly increasing the whole conversion efficiency.

Description

DC-AC bidirectional power converter topology

Technical field

The present invention relates to the technical field of battery power converters, and in particular to a DC-AC bidirectional power converter topology.

Background technique

The bidirectional power converter is used on the one hand to convert the DC battery voltage from low voltage direct current to an alternating voltage of, for example, 220 volts 50 Hz, and on the other hand to charge the battery by the AC voltage. Energy flows from the battery to the DC-AC converter and also from the DC-AC converter to the battery. Bidirectional power converters that currently implement this function mostly use two-stage conversion, first-stage DC-DC Boost/buck, second-stage DC-AC full-bridge pulse width modulation inverter, and transformer isolation on the AC side. The topology scheme of the existing bidirectional power converter has the disadvantages of complicated structure, low efficiency and large loss, so that the reliability and economy of the whole device are not high.

Summary of the invention

The object of the present invention is to overcome the shortcomings and shortcomings of the prior art, and to provide a DC-AC bidirectional power converter topology, which is suitable for use in a DC energy storage battery such as a smart grid energy storage system, and can realize DC/AC. The energy flows in both directions, the system is compact and efficient, and can be modularly built into a large-scale energy storage battery energy storage system or an energy storage power station.

The invention is mainly for solving the requirement of matching of new energy power generation and power consumption, and has the function of peak shaving of power grid, and proposes an energy storage technology capable of bidirectional flow of electric energy, and based on this, a power electronic device and The main circuit topology of the converter of the control technology. The hardware of the solution is compact, and the versatility, reliability and modularity are greatly improved.

The object of the invention is achieved by the following technical solution:

A DC-AC bidirectional power converter topology is disposed between an AC power grid and a DC energy storage battery to implement charging and discharging between a DC energy storage battery and an AC power grid. The topology includes a bidirectional DC/DC conversion circuit and a bidirectional a DC/AC conversion circuit, a high-voltage side DC filter and protection circuit, and a high-voltage side DC filter capacitor, wherein the low-voltage side of the bidirectional DC/DC converter circuit is connected to a DC energy storage battery for use in the discharge mode by the DC energy storage The generated AC power of the battery is output to the power grid, and the DC energy storage battery is charged in the charging mode;

The bidirectional DC/DC conversion circuit includes a DC input filtering and protection circuit, a high frequency power transformer T1, a first power diode, and a second power diode , power switch tube Q1 and power switch tube Q2;

The low-voltage side end of the high-frequency power transformer T1 is connected to one end of the DC energy storage battery (6) positive pole, the DC input filter and the protection circuit, and the other end of the low-voltage side of the high-frequency power transformer T1 and the D of the parallel power switch tube Q1 The pole is connected to the negative pole of the first power diode, the S pole of the power switch tube Q1, the cathode of the first power diode, the other end of the DC input filtering and protection circuit, and the negative end of the DC energy storage battery are connected to the ground end;

The high-voltage side end of the high-frequency power transformer T1 is connected to one end of the high-voltage side DC filter and protection circuit, one end of the bidirectional DC/AC conversion circuit, and the anode of the high-voltage side DC filter capacitor, and the other end of the above circuit is connected to the ground end. ;

The bidirectional DC/AC conversion circuit includes an AC filtering and protection circuit, a first dual-conducting power thyristor, a second bi-directional power thyristor, a third power diode, and a fourth power diode , power switch tube Q3, power switch tube Q4 and capacitor C3, capacitor C4;

The first double-conducting power thyristor is connected in parallel with the capacitor C3, and the other end is connected to the high-voltage side end of the high-frequency power transformer T1, and the other end is connected to the D-pole of the parallel power switch tube Q3 and the cathode of the third power diode. The two double-conducting power thyristors are connected in parallel with the capacitor C4, one end is connected to one end of the high-voltage power transformer T1, and the other end is connected to the D pole of the parallel power switch tube Q4 and the negative pole of the fourth power diode, the power switch tube The S pole of Q3 and Q4 and the positive pole of the third and fourth power diodes are connected to the ground end; the G poles of the power switch tubes Q3 and Q4 are respectively connected with the alternating current filtering and protection circuit and the two ends of the alternating current grid.

Preferably, the topology further includes a driving control circuit, two ends of the DC energy storage battery and the AC power grid, D poles of the power switch tubes Q1 and Q2, a high voltage side end of the high frequency power transformer T1, and a high voltage side DC filter. And the signal feedback of the protection circuit is connected to the detection circuit in the drive control circuit, and then the drive control circuit outputs the control signal to the G pole of the power switch tubes Q1, Q2, Q3, Q4 and the first and second two-way power thyristors.

Preferably, the filter circuit in the DC input filtering and protection circuit adopts a passive filtering network.

Preferably, the first dual-conducting power thyristor D1 and the second dual-conducting power thyristor D2 in the bidirectional DC/AC conversion circuit are bidirectional controllable power switches, and the conduction angles of D1 and D2 are adjustable. The voltage across the high-voltage side DC filter capacitor C2 changes with the adjustment of the conduction angle of D1 and D2.

Preferably, the first and second dual-conducting power thyristors and the power switching tubes Q3 and Q4 in the bidirectional DC/AC conversion circuit form a bridge circuit. When the DC energy storage battery operates in a discharging state, the bridge circuit Working in DC/AC single-phase full-bridge inverter state, converting DC input to AC output; when DC storage battery is working in charging state, the bridge circuit works in AC/DC single-phase full-bridge rectification state, and will communicate The input is converted to a DC output.

Preferably, the high frequency power transformer T1 in the bidirectional DC/DC converter circuit has the function of energy bidirectional flow. When the DC energy storage battery operates in the discharge mode, the power switch tube Q1 is turned on and off according to the drive control circuit. The signal works. At this time, the high-frequency power transformer T1 is in the flyback mode, the high-voltage side current flows through the parallel diode of the power switch tube Q2, and the high-frequency power transformer T1 operates in the boost state; when the DC energy storage battery operates in the charging mode When the power switch tube Q2 operates according to the turn-on and turn-off signals of the drive control circuit, the high-frequency power transformer T1 operates in the flyback mode, and the low-side current flows through the body diode of the power switch tube Q1, and the high-frequency power transformer T1 Working in a buck state.

Preferably, when the battery is in the discharging state, the 3 and 4 terminals of the power transformer T1 are output terminals, and the output voltage waveform is a forward sinusoidal AC half wave waveform.

Preferably, when the battery is in the charging state, the terminals 3 and 4 of the power transformer T1 are input terminals, and the input voltage is a constant DC voltage.

Preferably, when the battery is in the discharge state, the single-phase full-bridge circuit composed of D1, D2, Q3, and Q4 operates in an inverter state, and the operating frequency is a power frequency, and the forward sine half-wave on the DC/DC side is used. Transform into AC and merge into the grid;

Preferably, when the battery is in the charging state, the single-phase full-bridge circuit composed of D1, D2, Q3, and Q4 operates in a controlled rectification state to convert the grid AC power into the required DC power source;

Preferably, the bidirectional DC/DC conversion circuit can be operated independently or in parallel, and a plurality of bidirectional DC/DC conversion circuits can share a DC/AC conversion circuit when operating in parallel.

The present invention has the following advantages and effects over the prior art:

1. The working mode of the invention is special in the bidirectional DC/DC conversion circuit part. When the DC energy storage battery is discharged, the high voltage side voltage waveform is a forward half wave waveform which changes according to a sinusoidal law, so that the bidirectional DC/AC conversion part only needs to work. In the power frequency state, instead of the high-frequency pulse modulation state, the switching loss of the bidirectional DC/AC circuit bridge is greatly reduced, and the energy conversion efficiency is much higher than that currently used.

2. The invention adopts an efficient high-frequency power transformer to realize the conversion of the DC/DC part, and at the same time realizes the functions of boosting, step-down and electrical isolation. The transformer is efficient and compact, so that the overall conversion efficiency is much higher than the prior art.

3. The DC/AC circuit of the invention has a unique working mode. When DC to AC is switched, it works at the power frequency. When AC to DC is switched, the DC voltage is accurately adjusted by controlling the opening angle, and the control precision is high and the efficiency is high. simple.

DRAWINGS

1 is a topological structural view of a DC-AC bidirectional battery power conversion circuit of the present invention;

2 is a view showing the operation mode of a DC/DC converter circuit when a DC energy storage battery is discharged in the present invention;

3 is a waveform diagram showing current and voltage of a diode C2 in a DC/DC converter circuit during discharge operation of a DC energy storage battery according to the present invention;

4 is a view showing the operation mode of a DC/AC conversion circuit when a DC energy storage battery is discharged in the present invention;

5 is a voltage waveform diagram of an AC side of a DC/AC conversion circuit during discharge operation of a DC energy storage battery according to the present invention;

6 is a view showing the operation mode of a DC/AC conversion circuit during charging operation of a DC energy storage battery according to the present invention;

7 is a voltage waveform diagram of a DC side of a DC/AC conversion circuit during charging operation of a DC energy storage battery according to the present invention;

8 is a view showing the operation mode of a DC/DC conversion circuit when a DC energy storage battery is charged in the present invention;

In the figure, the reference numerals are: 1-bidirectional DC/DC converter circuit, 101-DC filter and protection circuit, 102-high frequency power transformer, 103-first power diode, 104-second power diode, 2-bidirectional DC /AC conversion circuit, 201-AC filter and protection circuit, 202-first double-conducting power thyristor, 203-second double-conducting power thyristor, 204-third power diode, 205-fourth power diode, 3-high voltage Side DC filtering and protection circuit, 4-high-side filter capacitor, 5-AC grid, 6-DC energy storage battery.

detailed description

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

Example

In the drawings, the same elements have the same reference numerals.

1 shows a power conversion circuit of the present invention, which includes a DC/DC conversion circuit 1, a DC/AC conversion circuit 2, a DC filter and protection circuit 3, a DC filter capacitor 4, an AC grid or an AC output 5, and a DC storage. The battery 6 is connected to the circuit, and the charge and discharge between the DC energy storage battery and the power grid are realized by the present invention.

The DC/DC conversion circuit 1 side is electrically connected to the DC energy storage battery 6, and the DC/DC conversion circuit can be operated independently or in parallel. When multiple DC/DC conversion circuits are operated in parallel, one DC/ AC conversion circuit.

The DC/DC conversion circuit 1 comprises a DC filtering and protection circuit 101, a high frequency power transformer T1 102, and a first power switch Q1. 103. The second power switch Q2 104 is composed.

The filter circuit part of the DC filter and protection circuit 101 adopts a passive filter network to reduce the large current when the DC energy storage battery 6 is charged and discharged, to protect the battery and reduce the input and output ripple. The protection circuit in the DC filter and protection circuit 101 protects against DC overvoltage and reverse connection faults, and protects the energy storage battery and the power converter.

As shown in FIG. 2, when the DC energy storage battery 6 is discharged, the high frequency power transformer T1 102 works in the flyback state, and controls the turn-on and turn-off of the power switch tube Q1 according to the frequency and amplitude of the output AC power. When Q1 is turned on, the high-frequency power transformer T1 is turned on at the primary side and stores energy in the winding electrically connected to the power switch tube Q1. When the power switch tube Q1 is turned off, the high-frequency power pulser stores the energy stored on the primary side. It is coupled to the secondary side and flows through a diode C2 in parallel with the power switch tube Q2. A voltage and current waveform which changes according to the law of the AC sinusoidal positive half wave is obtained on the diode C2 electrically connected to the secondary side winding, as shown in FIG.

High-frequency power transformer T1 during discharge of DC energy storage battery 102 simultaneously realizes the conversion of DC electric energy into AC electric energy converted according to the regular sine wave law, and converts the low voltage of the DC energy storage battery C1 into C2. The 220V high voltage on the upper side simultaneously realizes the function of isolating the DC energy storage battery from the AC side.

The DC/DC converter circuit can be operated in parallel and share a DC/AC conversion circuit to provide a larger DC storage battery capacity.

The control circuit controls the turn-on sequence of the power devices D1, D2, Q3, Q4 in the full-bridge circuit 2 based on the detected amplitude and frequency of the AC side and the zero-crossing signal. When the DC energy storage battery 6 is in the discharge state, when the grid voltage is a positive half wave, the switch tubes D1 and Q4 are simultaneously turned on. When the grid voltage is a negative half wave, the switch tubes D2 and Q3 are turned on, as shown in FIG. 4 and FIG. 5. Shown. The bridge circuit composed of D1, D2, Q3, and Q4 operates in the power frequency state, which greatly reduces the switching loss of the device, reduces the control difficulty, and effectively improves the working mode compared with the working mode of the pulse modulation state. The efficiency and reliability of the entire system.

During the charging process of the DC energy storage battery C1, the energy is supplied from the AC power grid through the bidirectional DC/AC circuit 2 to provide a DC voltage for the DC circuit portion. At this time, according to the charging voltage and the charging current of the DC energy storage battery C1, the adjustment is required. The conduction angle of the power switches D1 and D2 controls the charging current to the DC energy storage battery C1, and the maximum capacity increases the life of the DC energy storage battery. When the grid voltage is a forward half-wave, D1 is turned on, and the turn-on angle is adjusted to control the input power, and the charging current is recirculated through D1 and the power diode 205 connected in anti-parallel with the power switching device Q4. When the grid voltage is a negative half-wave, D2 is turned on, and the turn-on angle is adjusted to control the input power, and the charging current is recirculated through D2 and the power diode 204 connected in anti-parallel with the power switching device Q3. The turn-on sequence and the DC voltage waveform are shown in Figure 6 and Figure 7.

In DC storage battery C1 6 When operating in the charging state, the DC/DC bidirectional conversion circuit 1 operates in a flyback step-down operation state, and adjusts the charging voltage of the DC energy storage battery C1 by adjusting the operating frequency and the conduction pulse width of the power switching tube Q2. Current, when the voltage of the DC storage battery is gradually increased, adjust the opening angle and the opening frequency of the DC/AC circuit, control the charging current, and complete the charging of the DC energy storage battery. When the DC energy storage battery reaches the set charging voltage, the charging is stopped, the power switch tube Q2 and the bridge rectifier circuit 2 are turned off, the charging of the DC energy storage battery is completed, and the state of the DC energy storage battery is displayed correspondingly. When the DC energy storage battery C1 is charged, the power switch tube Q2 is turned on and off according to the pulse modulation signal given by the controller. When Q2 is turned on, the power is stored in the form of magnetic energy in the high frequency power transformer T1 and C2. On the high voltage side, when Q2 is turned off, the stored energy of the high side winding is coupled to the low voltage side electrically connected to the DC energy storage battery C1 through the high frequency power transformer T1 to charge the DC energy storage battery C1, and the current flows through the high frequency power. A low voltage side of the transformer T1, a DC energy storage battery, and a power diode 103 connected in parallel with the power switch Q1. The operation timing of the DC/DC bidirectional conversion circuit in the state of charge of the DC energy storage battery C1 is shown in FIG.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and combinations thereof may be made without departing from the spirit and scope of the invention. Simplifications should all be equivalent replacements and are included in the scope of the present invention.

Claims

A DC-AC bidirectional power converter topology, located between an AC grid (5) and a DC energy storage battery (6), for charging and discharging between a DC energy storage battery and an AC grid, the topology comprising a bidirectional DC /DC conversion circuit (1), bidirectional DC/AC conversion circuit (2), high-voltage side DC filter and protection circuit (3), and high-voltage side DC filter capacitor (4), characterized by:

The low-voltage side of the bidirectional DC/DC converter circuit is connected to a DC energy storage battery (6) for outputting AC power generated by the DC energy storage battery (6) to the power grid in a discharge mode, and in a charging mode Charging the DC energy storage battery (6);

The bidirectional DC/DC conversion circuit includes a DC input filtering and protection circuit (101), a high frequency power transformer T1 (102), and a first power diode (103), a second power diode (104), a power switch tube Q1, and a power switch tube Q2;

The low-voltage side end of the high-frequency power transformer T1 is connected to one end of the DC energy storage battery (6) positive pole, the DC input filtering and protection circuit (101), and the other end of the low-voltage side of the high-frequency power transformer T1 and the parallel power switch tube The D pole of Q1 is connected to the negative pole of the first power diode, the S pole of the power switch tube Q1, the cathode of the first power diode, the other end of the DC input filtering and protection circuit (101), and the negative of the DC energy storage battery (6). The ends are connected to the ground;

The high-voltage side end of the high-frequency power transformer T1 is connected to one end of the high-voltage side DC filter and protection circuit (3), one end of the bidirectional DC/AC conversion circuit (2), and the anode of the high-voltage side DC filter capacitor (4), The other end of the circuit is connected to the ground;

The bidirectional DC/AC conversion circuit (2) includes an AC filtering and protection circuit (201), a first bi-directional power thyristor (202), a second bi-directional power thyristor (203), and a third power diode (204), fourth power diode (205), power switch tube Q3, power switch tube Q4, capacitor C3, capacitor C4;

The first double-conducting power thyristor (202) is connected in parallel with the capacitor C3, and the other end is connected to the high-voltage side end of the high-frequency power transformer T1, and the other end is connected with the D-pole of the parallel power switch tube Q3 and the cathode of the third power diode. Connected, the second double-conducting power thyristor (203) is connected in parallel with the capacitor C4, and the other end is connected to the high-voltage side end of the high-frequency power transformer T1, and the other end is connected with the D-pole and the fourth power diode of the parallel power switch tube Q4. The negative pole is connected, the S poles of the power switch tubes Q3 and Q4 and the anodes of the third and fourth power diodes are connected to the ground end; the G poles of the power switch tubes Q3 and Q4 are respectively connected with the AC filter and protection circuit (201) and the AC grid ( 5) The two ends are connected.
The DC-AC bidirectional power converter topology according to claim 1, wherein the topology further comprises a driving control circuit (8), the DC energy storage battery and the two ends of the AC power grid, and the power switch tube The D pole of Q1 and Q2, the high voltage side end of the high frequency power transformer T1, the DC filter of the high voltage side and the signal feedback of the protection circuit are connected to the detection circuit (7) in the drive control circuit, and then the drive control circuit (8) outputs the control signal. To the G pole of the power switch tubes Q1, Q2, Q3, Q4 and the first and second two-way power thyristors.
The DC-AC bidirectional power converter topology of claim 1 wherein:

The filter circuit part of the DC input filtering and protection circuit (101) adopts a passive filter network.
The DC-AC bidirectional power converter topology of claim 1 wherein:

The first dual-conducting power thyristor D1 and the second dual-conducting power thyristor D2 in the bidirectional DC/AC conversion circuit are bidirectional controllable power switches, and the conduction angles of D1 and D2 are adjustable. The voltage across the high-voltage side DC filter capacitor C2 changes with the adjustment of the conduction angle of D1 and D2.
The DC-AC bidirectional power converter topology of claim 1 wherein:

The first and second dual-conducting power thyristors and the power switching tubes Q3 and Q4 in the bidirectional DC/AC conversion circuit (2) form a bridge circuit, and the bridge circuit is used when the DC energy storage battery operates in a discharging state. Working in DC/AC single-phase full-bridge inverter state, converting DC input to AC output; when DC storage battery is working in charging state, the bridge circuit works in AC/DC single-phase full-bridge rectification state, and will communicate The input is converted to a DC output.
The DC-AC bidirectional power converter topology according to claim 2, wherein:

The high-frequency power transformer T1 in the bidirectional DC/DC conversion circuit has the function of energy bidirectional flow. When the DC energy storage battery operates in the discharge mode, the power switch tube Q1 operates according to the turn-on and turn-off signals of the drive control circuit. At this time, the high-frequency power transformer T1 is in the flyback mode, the high-voltage side current flows through the diode of the power switch tube Q2, and the high-frequency power transformer T1 operates in the boost state; when the DC energy storage battery operates in the charging mode, the power The switch tube Q2 operates according to the turn-on and turn-off signals of the drive control circuit. At this time, the high-frequency power transformer T1 operates in the flyback mode, the low-side current flows through the body diode of the power switch tube Q1, and the high-frequency power transformer T1 operates in the lower limit. Pressure state.
The DC/AC bidirectional battery power conversion circuit according to any one of claims 1 to 6, wherein:

When the battery is in the discharge state, the 3 and 4 terminals of the power transformer T1 are output terminals, and the output voltage waveform is a forward sinusoidal AC half wave waveform.
The DC/AC bidirectional battery power conversion circuit according to any one of claims 1 to 6, wherein:

When the battery is in the charging state, the terminals 3 and 4 of the power transformer T1 are input terminals, and the input voltage is a constant DC voltage.
The DC/AC bidirectional battery power conversion circuit according to any one of claims 1 to 6, wherein:

When the battery is in the discharge state, the single-phase full-bridge circuit composed of D1, D2, Q3, and Q4 operates in the inverter state, and the operating frequency is the power frequency, and the forward sine half wave on the DC/DC side is converted into the alternating current. Incorporate into the grid.
The DC/AC bidirectional battery power conversion circuit according to any one of claims 1 to 6, wherein:

When the battery is in the charging state, the single-phase full-bridge circuit composed of D1, D2, Q3, and Q4 operates in a controlled rectification state to convert the grid AC power into the required DC power.
The DC-AC bidirectional power converter topology according to any one of claims 1 to 6, characterized in that:

The bidirectional DC/DC conversion circuit can be operated independently or in parallel, and a plurality of bidirectional DC/DC conversion circuits can share a DC/AC conversion circuit when operating in parallel.