CN102035463A - 6 kV medium voltage frequency converter based on neutral-point-clamped three-level technology - Google Patents
6 kV medium voltage frequency converter based on neutral-point-clamped three-level technology Download PDFInfo
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- CN102035463A CN102035463A CN2010105842987A CN201010584298A CN102035463A CN 102035463 A CN102035463 A CN 102035463A CN 2010105842987 A CN2010105842987 A CN 2010105842987A CN 201010584298 A CN201010584298 A CN 201010584298A CN 102035463 A CN102035463 A CN 102035463A
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Abstract
The invention relates to a 6 kV medium voltage frequency converter based on a neutral-point-clamped three-level technology. The frequency converter comprises a rectifying power supply, a neutral-point-clamped three-level inverter and a zero sequence reactor, and is mainly technically characterized in that the two sides of a three-phase winding of a motor stator with open neutral-point connection are connected with a set of inverter respectively to form a serial loop; and two sets of inverters share a group of rectifying power supply. Through the invention, the rated output voltage of the traditional neutral-point-clamped three-level (3L-NPC) frequency converter is increased to 6 kV based on the advantages of the traditional neutral-point-clamped 3L-NPC frequency converter; meanwhile, the output phase voltage is 5 levels; the ratio of dv to dt is the same as that of the traditional 3 kV neutral-point-clamped three-level inverter; a 5 kV motor can be used directly; the requirements of the voltage class standard in China are met; and the 6 kV medium voltage frequency converter has the characteristics of simple structure, reliable operation and the like and is easy to realize feedback.
Description
Technical field
The invention belongs to the frequency conversion and speed regulation of AC motor technical field, especially a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology.
Background technology
Frequency converter is to utilize the on-off action of power semiconductor device power frequency supply to be transformed to the electric energy control device of required frequency, can realize soft start or frequency control to AC induction motor, the most frequently used frequency converter is the AC-DC-AC voltage frequency converter, is divided into four parts usually: rectifier, energy storage capacitor, inverter and controller.Rectifier is that the alternating current with fixed-frequency is converted to galvanic equipment; Energy storage capacitor is used for storing the electric energy after the conversion; Inverter is the equipment that direct current is changed into the alternating current of different frequency, amplitude; Controller is by the program work of setting, the pulse duration of control of conversion device output voltage square wave, and making fundamental voltage output of voltage is equivalent sine wave, and then drives the equipment of alternating current motor.
Mid point clamper three level (be called for short 3L-NPC) frequency converter be high-power (＞press one of present most widely used voltage frequency converter of frequency conversion and speed regulation of AC motor technical field in 1MW).The inverter of existing 3L-NPC frequency converter is made of three 3L-NPC Zhi Lu And connection, as shown in Figure 1, on each 3L-NPC branch road, constitute by four switch modules (wherein each switch module comprises a controllable devices and a fly-wheel diode) and two mid point clamp diodes, its advantage is: main circuit is simple, switching device quantity is few, only need a cover rectifier power source, the energy feedback realizes easily, the problem of its existence is: under the situation that existing High-tension Switch Devices is not connected, the rated output voltage of the inverter of 3L-NPC frequency converter does not reach 6kV, does not satisfy China's GB; And the dv/dt of output voltage waveforms is higher, influences common standard insulation of Electric Motor and useful life, needs to use the special (type) motor of reinforced insulation.
In order to improve output voltage, a kind of method is to adopt the switch module series system to realize: it changes each switch module in Fig. 1 main circuit into two strings, DC bus-bar voltage U
dBe increased to 9kV, make the maximum output line voltage of inverter reach 6.3kV, the problem that this method exists is: the switch module series connection need have all presses measure, and reliability is affected, and because dv/dt increases, need install huge output filter additional; Another kind method is the frequency converter that adopts 3 single-phase H bridges of 3L-NPC to constitute, single-phase H bridge of every phase, every bridge by two 3L-NPC branch roads in parallel and one group floating empty ± the 2.5kV rectifier power source constitutes, as shown in Figure 2, the problem that this method exists is: need to use the floating empty rectifier power source of 3 covers, lost the transformer of conventional 3L-NPC frequency converter and rectifier power source simple, realize that feedback is easy to advantage, and single-phase H bridge requires the energy storage capacitor amount that many bigger than three phase inverter bridge.
In sum, prior art can not be increased to 6kV with its rated output voltage on the basis that guarantees existing 3L-NPC frequency converter advantage.
Summary of the invention
The objective of the invention is to overcome the deficiencies in the prior art, a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology is provided, both kept the advantage of existing 3L-NPC frequency converter, its rated output voltage can be increased to 6kV again simultaneously.
The present invention solves its technical problem and takes following technical scheme to realize:
A kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology, comprise rectifier power source, mid point clamper three-level inverter and zero-sequence reactor, respectively connect a cover mid point clamper three-level inverter on the motor stator three phase winding both sides that the mid point on line is opened and constitute series loop, the shared one group of rectifier power source of two cover mid point clamper three-level inverters, zero-sequence reactor winding and motor stator three-phase windings in series are together.
And, described mid point clamper three-level inverter is made of three mid point clampers, three level Zhi Lu And connection, each mid point clamper three level branch road constitutes by four switch modules and two mid point clamp diodes, and each switch module constitutes by a controllable devices and a fly-wheel diode reverse parallel connection.
And described controllable devices is IGBT or IGCT or IEGT high tension apparatus.
And described zero-sequence reactor is 3 winding zero-sequence reactors or 6 winding zero-sequence reactors.
And described motor stator three phase windings adopt one of following three kinds of modes to be connected with the zero-sequence reactor winding: use one 3 winding zero-sequence reactor to be serially connected with motor stator three phase windings one side; Use two 3 winding zero-sequence reactors to be serially connected with the both sides of motor stator three phase windings respectively; Use one 6 winding zero-sequence reactor, wherein 3 windings are serially connected with motor stator three phase windings one side, and 3 windings are serially connected with motor stator three phase winding opposite sides in addition.
And described rectifier power source is made up of rectifier and energy storage capacitor.
And, the DC bus-bar voltage U of described rectifier power source
d≈ 5kV, this rectifier power source are one of following three kinds of modes: uncontrollable rectifier power source, rectification/feedback power and PWM rectifier power source.
And the input of described two cover mid point clamper three-level inverters connects a pair of energy storage capacitor respectively, or the shared a pair of energy storage capacitor of two cover mid point clamper three-level inverters.
And, the PWM modulation strategy of two cover mid point clamper three-level inverters is voltage space vector pwm theory or the triangular carrier comparison method that 3 frequency multiplication AC biases are arranged, PWM's modulation period of two cover mid point clamper three-level inverters stagger the half period, make that the output phase voltage reaches 5 level, equivalent switching frequency doubles.
Advantage of the present invention and good effect are:
1, this medium voltage frequency converter respectively connects a cover 3L-NPC mid point clamper three-level inverter formation series loop by the motor stator three phase winding both sides of opening in the mid point on line, realized the output voltage of existing 3L-NPC frequency converter has been brought up to 6kV from 3kV, satisfied China's electric pressure standard-required, had circuit and realize feedback, characteristics such as reliable simply, easily.
2, the dv/dt of this 6kV medium voltage frequency converter is identical with the dv/dt of the existing 3L-NPC inverter output voltage of 3kV, can not influence motor insulation and useful life, and the zero-sequence reactor that increases between inverter output and motor stator three phase windings not only limits zero-sequence current, also can further reduce the influence of dv/dt, so this frequency converter can directly drive common 6kV alternating current machine to motor.
3, the rectifier power source of this medium voltage frequency converter uses one group and is about ± the 2.5kV DC power supply, and transformer and rectifier power source are simple, realize feedback easily, and can be used for common DC bus.
4, this medium voltage frequency converter makes the PWM of the two cover inverters T/2 (T-modulation period) that staggers modulation period, make output phase voltage level number increase to 5 from 3, and equivalent switching frequency doubles, and harmonic wave has been reduced, help to solve use High-tension Switch Devices after switching frequency reduce the difficulty of bringing.
5, pressure transformer is connected on the three-phase inverter input with energy storage capacitor in this, and is little than single-phase H bridge concatenated schemes capacitance.
Description of drawings
Fig. 1 is the circuit diagram of conventional three-phase 3L-NPC converter main circuit;
Fig. 2 is the circuit diagram of the ACS-5000 frequency converter of ABB AB;
Fig. 3 is the circuit diagram based on the 6kV medium voltage frequency converter of mid point clamper three Level Technology that the embodiment of the invention provides;
Fig. 4 is the 3 winding zero-sequence reactor zero-sequence reactor schematic diagrames that the embodiment of the invention provides;
Fig. 5 is the 6 winding zero-sequence reactor zero-sequence reactor schematic diagrames that the embodiment of the invention provides;
Fig. 6 is the voltage oscillogram of the inverter output that provides of the embodiment of the invention;
Fig. 7 is the two cover 3L-NPC rectifier power source (circuit diagrams of AFE) And connection circuit.
Embodiment
Below in conjunction with accompanying drawing the embodiment of the invention is further described:
A kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology, as shown in Figure 3, among the figure, U
dIt is DC bus-bar voltage; u
I, a, b, cAnd u
II, a, b, cIt is respectively the phase voltage of I cover and the output of II cover three-phase 3L-NPC inverter; u
A, b, cBe the motor stator three phase windings pressures that power on; u
0It is residual voltage; Three tri-state switch are represented each the 3L-NPC branch road in the conventional three-phase 3L-NPC inverter respectively.
In the present embodiment, 6kV medium voltage frequency converter based on mid point clamper three Level Technology comprises mid point clamper three-level inverter, rectifier power source and zero-sequence reactor, respectively connect a cover mid point clamper three-level inverter on the motor stator three phase winding both sides that the mid point on line is opened and constitute series loop, the shared one group of rectifier power source formed by rectifier and energy storage capacitor of two cover mid point clamper three-level inverters, the input of two cover mid point clamper three-level inverters connects a pair of energy storage capacitor or the shared a pair of energy storage capacitor of two cover mid point clamper three-level inverters respectively, and motor stator three phase windings and zero-sequence reactor windings in series are together.
In the present embodiment, drive motor is 6kV asynchronous motor or synchronous motor (permanent magnetism or excitation), the inverter that motor stator three phase winding both sides connect all adopts three-phase 3L-NPC inverter, as shown in Figure 1, this three-phase 3L-NPC inverter is made of three mid point clampers, three level Zhi Lu And connection, each mid point clamper three level branch road constitutes by four switch modules and two mid point clamp diodes, each switch module constitutes by a controllable devices and a fly-wheel diode reverse parallel connection, in the figure, V
1～V
4Be the controllable devices in the mid point clamper three level branch roads, this controllable devices can be IGBT, also can be IGCT or IEGT high tension apparatus, and the rated voltage of this controllable devices is 4.5kV.Two cover inverters are about ± 2.5kV (U for shared one group
d≈ 5kV) rectifier power source, the desirable non-loaded line voltage (effective value) of every cover inverter output is 3.5kV, two cover series connection back output 7kV satisfy 6kV motor needs fully.
Behind the shared one group of dc bus of two cover inverters, in motor windings, except that positive sequence or negative-sequence current, also have zero-sequence current and flow through.For suppressing zero-sequence current, introduce a zero-sequence reactor (claiming the common mode zero-sequence reactor again), it is to be wound with 3 winding zero-sequence reactors or 6 winding zero-sequence reactors on an iron core, 3 winding zero-sequence reactors or 6 winding zero-sequence reactors are respectively as Fig. 4 and shown in Figure 5, its winding respectively with motor three-phase windings in series.When flowing through positive sequence or negative-sequence current, the three-phase current sum equals 0, and iron core is not magnetized, and has only interlinked leakage, and zero-sequence reactor becomes three small inductors, does not influence the fundamental voltage of inverter output; When flowing through zero-sequence current, the three-phase current homophase, three-phase current sum ≠ 0, iron core is magnetized, and zero-sequence reactor becomes a big inductance, suppresses zero-sequence current.Residual voltage is made up of two parts: one is the component of 3 times of fundamental frequencies, its amplitude is little, it only is 15～20% of first-harmonic output voltage, reduce with fundamental frequency and voltage magnitude, the frequency and the amplitude of 3 frequency multiplication components descend in proportion, the volt-second area strengthens in the time of can not low frequency occurring, makes saturated conditions unshakable in one's determination; Another part is the component of switching frequency, and amplitude is higher, but frequency is high and fixing, and the volt-second area is little, can not reduce with fundamental frequency and strengthen.Volt-second area and core section are proportional, and the volt-second area is little, and the zero-sequence reactor volume and weight is just little.The connected mode of zero-sequence reactor winding and motor stator three phase windings has three kinds: one 3 winding zero-sequence reactor is serially connected with motor stator three phase windings one side; Two 3 less winding zero-sequence reactors are serially connected with the both sides of motor stator three phase windings respectively; One 6 winding zero-sequence reactor, 3 windings are serially connected with motor stator three phase windings one side, and 3 windings are serially connected with motor stator three phase winding opposite sides in addition.
In frequency converter provided by the invention, conventional strategy is adopted in the PWM modulation of two cover three-phase 3L-NPC inverters: voltage space vector pwm theory (SVPWM) or the triangular carrier comparison method (SPWM) of 3 frequency multiplication AC biases is arranged.But, require the PWM of the two cover inverters T/2 (T-modulation period) that staggers modulation period, then the phase voltage output waveform (u in output fundamental voltage＞0 o'clock
I+ u
II) as shown in Figure 6, in the figure, u
IAnd u
IIIt is respectively the phase voltage waveform of I cover and the output of II cover three-phase 3L-NPC inverter; u
I+ u
IIBe u
IAnd u
IISynthetic; D is the duty ratio of PWM modulation.
As can be seen from Figure 6, the phase output waveform has 5 kinds of level (± U
d, ± U
d/ 2 and 0, negative level o'clock just occurs in output fundamental voltage＜0), and the equivalent switching frequency of output voltage doubles.The output-voltage levels number increases to 5 from 3, can reduce harmonic wave.After equivalent switching frequency doubled, the sample frequency of respective digital control system also multiplicable (every T/2 once sampling) was to reducing harmonic wave, improving dynamic performance and have very great help.After using the high voltage switch device, because switching loss is big, switching frequency is reduced to hundreds of Hz, and harmonic wave is big, and dynamic property is influenced, brings very big difficulty for the design of variable frequency adjustment system.Equivalent switching frequency and sample frequency double and will alleviate the difficulty that low switching frequency brings.
It can also be seen that from Fig. 6 output voltage kick amplitude is U
d/ 2 ≈ 2.5kV that is to say that the dv/dt of new 6kV inverter output voltage is identical with the conventional 3L-NPC inverter of 3kV.Because added zero-sequence reactor between new inverter and motor, it also can further reduce the dv/dt that adds to motor windings.
Rectifier power source of the present invention is identical with the rectifier power source of conventional three-phase 3L-NPC frequency converter, and three kinds of forms are arranged: uncontrollable rectifier power source, be used for single quadrant transmission, install brake unit and dynamic braking resistance additional after, also can be used for the four-quadrant transmission; Rectification/feedback power is used for the four-quadrant transmission; PWM rectification (also claiming active front-end A FE) power supply is used for four-quadrant transmission and the high occasion of power grid quality requirement.
If want to use the AFE power supply, and wish the switching device and the converter of use and the same specification of inverter, (AFE) And joins circuit can to adopt two cover 3L-NPC rectifier power sources, as shown in Figure 7, in the figure, Ud is a DC bus-bar voltage, and 3L-NPC represents 3L-NPC rectifier power source (AFE), as can be seen: DC bus-bar voltage still is about ± 2.5kV, but current doubles.
It is emphasized that; embodiment of the present invention is illustrative; rather than it is determinate; therefore the present invention is not limited to the embodiment described in the embodiment; every other execution modes that drawn by those skilled in the art's technical scheme according to the present invention belong to the scope of protection of the invention equally.
Claims (9)
1. 6kV medium voltage frequency converter based on mid point clamper three Level Technology, comprise rectifier power source, mid point clamper three-level inverter and zero-sequence reactor, it is characterized in that: respectively connect a cover mid point clamper three-level inverter on the motor stator three phase winding both sides that the mid point on line is opened and constitute series loop, the shared one group of rectifier power source of two cover mid point clamper three-level inverters, zero-sequence reactor winding and motor stator three-phase windings in series are together.
2. a kind of 6kV medium voltage frequency converter according to claim 1 based on mid point clamper three Level Technology, it is characterized in that: described mid point clamper three-level inverter is made of three mid point clampers, three level Zhi Lu And connection, each mid point clamper three level branch road constitutes by four switch modules and two mid point clamp diodes, and each switch module constitutes by a controllable devices and a fly-wheel diode reverse parallel connection.
3. a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology according to claim 2 is characterized in that: described controllable devices is IGBT or IGCT or IEGT high tension apparatus.
4. a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology according to claim 1 is characterized in that: described zero-sequence reactor is 3 winding zero-sequence reactors or 6 winding zero-sequence reactors.
5. a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology according to claim 4 is characterized in that: described motor stator three phase windings adopt one of following three kinds of modes to be connected with the zero-sequence reactor winding: use one 3 winding zero-sequence reactor to be serially connected with motor stator three phase windings one side; Use two 3 winding zero-sequence reactors to be serially connected with the both sides of motor stator three phase windings respectively; Use one 6 winding zero-sequence reactor, wherein 3 windings are serially connected with motor stator three phase windings one side, and 3 windings are serially connected with motor stator three phase winding opposite sides in addition.
6. a kind of 6kV medium voltage frequency converter based on mid point clamper three Level Technology according to claim 1, it is characterized in that: described rectifier power source is made up of rectifier and energy storage capacitor.
7. according to claim 1 or 6 described a kind of 6kV medium voltage frequency converters based on mid point clamper three Level Technology, it is characterized in that: the DC bus-bar voltage Ud ≈ 5kV of described rectifier power source, this rectifier power source is one of following three kinds of modes: uncontrollable rectifier power source, rectification/feedback power and PWM rectifier power source.
8. a kind of 6kV medium voltage frequency converter according to claim 1 based on mid point clamper three Level Technology, it is characterized in that: the input of described two cover mid point clamper three-level inverters connects a pair of energy storage capacitor respectively, or the shared a pair of energy storage capacitor of two cover mid point clamper three-level inverters.
9. a kind of 6kV medium voltage frequency converter according to claim 1 based on mid point clamper three Level Technology, it is characterized in that: the PWM modulation strategy of two cover mid point clamper three-level inverters is voltage space vector pwm theory or the triangular carrier comparison method that 3 frequency multiplication AC biases are arranged, PWM's modulation period of two cover mid point clamper three-level inverters stagger the half period, make that the output phase voltage reaches 5 level, equivalent switching frequency doubles.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103280956A (en) * | 2013-05-08 | 2013-09-04 | 河南科技大学 | Virtual vector optimizing and neutral-point potential balancing closed-loop control system of multilevel inverter |
| CN104333284A (en) * | 2014-11-03 | 2015-02-04 | 东南大学 | Direct torque control method for six-phase synchronous motor with zero-sequence current self-correction |
| CN110971162A (en) * | 2019-12-11 | 2020-04-07 | 浙江大学 | Improved model prediction torque control method of NPC three-level converter-PMSM system |
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| JPH11150986A (en) * | 1997-11-20 | 1999-06-02 | Fuji Electric Co Ltd | Control equipment of parallel multiplex power inverter |
| CN1578110A (en) * | 2003-07-04 | 2005-02-09 | Abb有限公司 | Frequency converter and drive for electric motor |
| CN1974261A (en) * | 2005-11-30 | 2007-06-06 | 株式会社日立制作所 | Motor driving device and automobile using the same |
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| CN1083282A (en) * | 1992-06-24 | 1994-03-02 | 三菱电机株式会社 | The parallel Operation Control device of power converter |
| CN1109653A (en) * | 1994-03-31 | 1995-10-04 | 三菱电机株式会社 | Parallel multiple inverter |
| JPH11150986A (en) * | 1997-11-20 | 1999-06-02 | Fuji Electric Co Ltd | Control equipment of parallel multiplex power inverter |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103280956A (en) * | 2013-05-08 | 2013-09-04 | 河南科技大学 | Virtual vector optimizing and neutral-point potential balancing closed-loop control system of multilevel inverter |
| CN103280956B (en) * | 2013-05-08 | 2015-06-17 | 河南科技大学 | Virtual vector optimizing and neutral-point potential balancing closed-loop control system of multilevel inverter |
| CN104333284A (en) * | 2014-11-03 | 2015-02-04 | 东南大学 | Direct torque control method for six-phase synchronous motor with zero-sequence current self-correction |
| CN104333284B (en) * | 2014-11-03 | 2017-02-15 | 东南大学 | Direct torque control method for six-phase synchronous motor with zero-sequence current self-correction |
| CN110971162A (en) * | 2019-12-11 | 2020-04-07 | 浙江大学 | Improved model prediction torque control method of NPC three-level converter-PMSM system |
| CN110971162B (en) * | 2019-12-11 | 2021-04-06 | 浙江大学 | Model prediction torque control method of NPC three-level converter-PMSM system |
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Application publication date: 20110427 |