Three-level I-type high-power energy storage converter

Abstract

The invention discloses a three-level I-type high-power energy storage converter, which relates to the technical field of power electronics and comprises a three-phase four-wire power grid power supply, an LC alternating-current low-pass filter circuit consisting of inductors L1 to L4 and capacitors C1 to C4, alternating-current contactors KM1 to KM4, a three-phase three-level I-type power inversion topological circuit consisting of six IGBT (Insulated Gate Bipolar Translator) modules connected in parallel, and direct-current end contactors KM5-KM7, the I-type three-level power converter is provided with three phases A, B and C, each phase is formed by connecting two IGBT modules in parallel, the topology is provided with six IGBT modules, each module comprises four groups of insulated gate pole thyristors / diodes Txi1, Txi2, Txi3 and Txi4 and two clamping diodes Dx1 and Dx2 (x = a, b and c; i = 1, 2). The topology of the I-type power inverter system is obtained from three levels, and the I-type power inverter system has a double-phase current conversion function; the high-voltage direct-current bus module is used for outputting high-direct-current bus voltage to the I-type inverter system and outputting alternating current, and the alternating current outputs stable waveform after being subjected to LC filtering and enters a load power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a three-level I-type high-power energy storage converter. Background Art

[0002] With the continuous development of society, the electricity load is increasing, which makes the transmission capacity of long-distance transmission lines increase continuously, and people have higher and higher requirements for power quality. As an important device for energy conversion between batteries and power grids, energy storage inverters can play a role of real-time balancing in the power system, release or store energy according to the actual situation, promote the exchange of energy between batteries and power grids, and solve the problem of peak and valley difference between day and night.

[0003] In order to promote the high-quality development of the distribution network under the new situation, improving the energy storage technology of the inverter system is crucial to building a safe, sufficient, economical and efficient power system. There are mainly two types of inverter systems: three-level circuits and two-level circuits. Compared with ordinary two-level circuits, the three-level circuit has a good effect on improving current ripple and reducing losses because it has midpoint freewheeling capability.

[0004] Therefore, in view of this, the shortcomings of the existing structure are studied and improved, and a three-level I-type high-power energy storage converter is proposed. Summary of the invention

[0005] The object of the present invention is to provide a three-level I-type high-power energy storage converter to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a three-level I-type high-power energy storage converter, comprising a three-phase four-wire grid power supply, an inductor L 1 ~L 4 and capacitor C 1 ~C 4 LC AC low-pass filter circuit composed of AC contactor KM 1 ~KM 4 , a three-phase three-level I-type power inverter topology circuit consisting of 6 IGBT modules in parallel, DC end contactor KM 5 ~KM 7 The I-type three-level power converter has three phases A, B, and C. Each phase consists of two IGBT modules in parallel. The topology has a total of 6 IGBT modules. Each module contains four groups of insulated gate thyristors / diodes Txi1, Txi2, Txi3, and Txi4, two clamping diodes Dx1 and Dx2 (x=a, b, c; i=1, 2). The topology structure also includes two series capacitors C5 and C6, and the midpoint of the two capacitors is N.

[0007] Furthermore, the contactor KM 5 and KM6 Common resistance R 1 , forming a DC pre-charge and discharge circuit.

[0008] Furthermore, the LC AC filter circuit is used to provide a standard sine wave for the power grid.

[0009] Further, the AC / DC contactor includes an open state and a closed state.

[0010] Furthermore, each phase of the three-level inverter bridge arm is composed of two IGBT modules connected in parallel, and each module is composed of four switch devices connected in series.

[0011] Furthermore, identical capacitors C5 and C6 are connected in series to form a support capacitor.

[0012] The present invention provides a three-level I-type high-power energy storage converter, which has the following beneficial effects: compared with the traditional converter, the topology of the present invention has the advantages of small output voltage and current harmonics, large output power, and halved voltage and switching loss borne by the switching device; the I-type power inverter system topology is obtained by three levels and has a two-phase current conversion function; the high-voltage DC bus module is used to output a high DC bus voltage to the I-type inverter system and output AC power, and the AC power outputs a stable waveform after LC filtering and enters the load power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the structure of a three-level I-type energy storage inverter system of the present invention;

[0014] Figure 2 This is a type I inverter power topology diagram in an embodiment of the present invention;

[0015] Figure 3 The DC-AC voltage waveform diagram of the inverter system of the present invention before filtering;

[0016] Figure 4 This is a voltage waveform diagram of the inverter system of the present invention after LC filtering. DETAILED DESCRIPTION

[0017] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0018] See also Figures 1 to 4 The present invention provides a technical solution: a three-level I-type high-power energy storage converter, comprising: a three-phase four-wire grid power supply, an inductor L 1 ~L 4 and capacitor C 1 ~C 4 LC AC low-pass filter circuit composed of AC contactor KM 1 ~KM4 , a three-phase three-level I-type power inverter topology circuit consisting of 6 IGBT modules in parallel, DC end contactor KM 5 ~KM 7 , among which, in order to reduce costs, the contactor KM 5 and KM 6 Common resistance R 1 , forming a DC pre-charge and discharge circuit;

[0019] The LC AC filter circuit is mainly used to provide a standard sine wave for the power grid, thereby improving the quality of the power grid. Therefore, the selection of AC filter inductance and capacitance values ​​is particularly important. The resonant frequency of the LC filter should be no less than 10 times the fundamental frequency and generally less than or equal to the switching frequency.

[0020]

[0021] Where f is the fundamental frequency, usually 50Hz, f k is the switching frequency, f 谐振 The resonant frequency produced by LC.

[0022]

[0023] AC / DC contactors include open and closed states. Prevent excessive surge current at the moment of power-on from damaging semiconductor devices and reducing the life of supporting capacitors. 6 and R 1 The DC pre-charging circuit is essential.

[0024] In the present invention, the pre-charge resistor R 1 The value is calculated by the following formula

[0025]

[0026] Among them, V dc_max is the maximum voltage at the DC terminal, C bus is the support capacitor, V T It is a given pre-charge voltage difference, usually a constant, and here it is 5V.

[0027] In order to increase the current specification of the I-type three-level bidirectional converter system, each phase of the three-level inverter bridge arm is composed of two IGBT modules in parallel, and each module is composed of four switch devices in series. Txi2 and Txi3 and clamping diodes Dx1 and Dx2 together clamp the potential of the output end to the midpoint N. The same capacitor C 5 and C 6 The supporting capacitor is connected in series, which is equivalent to C bus The voltage across the two ends is called Bus voltage (V bus ). When the DC voltage is U dcWhen the voltage across each capacitor is U dc / 2. The load power factor is known to be 1, and the AC rated current satisfies

[0028]

[0029] Among them, I ac is the rated line current of phase A, P n Represents the rated output power of the inverter, U ac is the rated AC line voltage. Voltage modulation ratio

[0030]

[0031] Voltage DC ripple ΔU dc satisfy

[0032] ΔU dc ≤0.02U dc

[0033] Here ΔU dc =0.02U dc , according to the formula

[0034]

[0035] Thus, the capacitance of the required support capacitor can be calculated.

[0036] In addition, in the embodiment, in order to ensure that the three-phase voltage has the least number of switching devices during the inversion process, the phase potential should not be at +U dc / 2 and -U dc / 2 directly changes, and through the transition of the neutral point potential, the on-state characteristics of the three-level converter are: each phase always has two adjacent switch devices turned on, and the other two devices turned off, so as to obtain different on-off state combinations and corresponding output voltages. Txi1 and Txi3 cannot be turned on at the same time. They are in a logical negation relationship, and their drive signals are complementary ignoring the dead zone. Similarly, Txi2 and Txi4 are also in a logical negation relationship. Thus, each bridge arm of the converter has three output voltage levels, namely U dc / 2, 0, -U dc / 2. Each phase output has three switching states: positive (1), zero (0), and negative (-1).

[0037]

[0038] Before the whole machine is powered on, for the inverter topology system, such as Figure 2 As shown, a DC source is used to directly supply power at the BUS end, and the voltage is gradually increased from 5V to 24V. The differential probe of the oscilloscope is used to measure and record the inverter waveform of the three-phase AC ports A, B, and C of the IGBT board. Figure 3As shown, the yellow waveform is the AB phase voltage waveform, and the green waveform is the BC phase voltage waveform. Due to the characteristics of the PWM pulse itself, the output voltage of the inverter contains more high-order harmonics, so it is necessary to add an LC low-pass filter at the output end of the inverter.

[0039] According to the above LC AC filter circuit principle, the experimental parameters are derived for testing. When the converter carries a resistive load, the output voltage waveform after filtering by the filter is as follows: Figure 4 shown. Figure 4 (a) is the output waveform of the BC phase of the converter before filtering. Figure 4 (b) is the BC phase grid waveform after LC filtering. It can be seen from the figure that after LC filtering, the converter output voltage is smooth and the harmonics are greatly reduced, which meets the converter performance index requirements.

[0040] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various implementations with various modifications suitable for specific uses.

Claims

1. A three-level I-type high-power energy storage converter, It is characterized in that Including three-phase four-wire power grid, inductor L 1 ~L 4 and capacitor C 1 ~C 4 LC AC low-pass filter circuit composed of AC contactor KM 1 ~KM 4 , a three-phase three-level I-type power inverter topology circuit consisting of 6 IGBT modules in parallel, DC end contactor KM 5 ~KM 7 The I-type three-level power converter has three phases A, B, and C. Each phase consists of two IGBT modules in parallel. The topology has a total of 6 IGBT modules. Each module contains four groups of insulated gate thyristors / diodes Txi1, Txi2, Txi3, and Txi4, two clamping diodes Dx1 and Dx2 (x=a, b, c; i=1, 2). The topology structure also includes two series capacitors C5 and C6, and the midpoint of the two capacitors is N.

2. A three-level I-type high-power energy storage converter according to claim 1, It is characterized in that Contactor KM 5 and KM 6 Common resistance R 1 , forming a DC pre-charge and discharge circuit.

3. A three-level I-type high-power energy storage converter according to claim 1, It is characterized in that The LC AC filter circuit is used to provide a standard sine wave for the power grid.

4. A three-level I-type high-power energy storage converter according to claim 1, It is characterized in that The AC / DC contactor includes open and closed states.

5. A three-level I-type high-power energy storage converter according to claim 1, It is characterized in that Each phase of the three-level inverter bridge arm is composed of two IGBT modules in parallel, and each module is composed of four switching devices in series.

6. A three-level I-type high-power energy storage converter according to claim 5, It is characterized in that Identical capacitors C5 and C6 are connected in series to form support capacitors.

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