CN101989832A - Frequency control of motor speed driver of double-fed energy three-phase electric machine - Google Patents

Abstract

The invention relates to a frequency control of motor speed driver of a double-fed energy three-phase electric machine, which is composed of four parts such as a main rectifier 100, a blocking-up phase selecting switch 200, a boost convertor 300, and a pulse-width modulation (PWM) frequency conversion sine wave generator 400; and energy-storage travelling wave tubes related to fundamental wave of an input three-phase power source or output speed regulation source or harmonic wave thereof is not arranged in the system, the 22% of average output or energy feedback power is processed at a high frequency mode by the boost convertor, so that no matter a motor is stared normally or is subject to the energy feedback, the motor has no harmonic radiation to the power grid, and the system has good stability.

Description

Energy double-fed three phase electric machine frequency-changing speed-regulating driver

Relevant patent

Content of the present invention and U.S. Pat 5784269, Chinese patent 01140014.5,, Chinese patent CN200810006950.X, U.S. Pat 6046915, US20090040800 is associated.

Technical field

The present invention relates to the three-phase induction motor frequency control, especially a kind of High Power Factor forward drive, High Power Factor energy back three phase electric machine frequency variant speed regulating circuit reaches the power supply that similarly need carry out the energy transmitted in both directions, is adapted to the double-fed wind generating converter especially.

The background technology part

Induction-motor load occupies maximum proportion in electrical network, adopt variable-frequency control technique to can save energy, improve control performance, has obtained good effect and remarkable economic efficiency in application.Along with the progress of semiconductor power device technology, become main flow based on the frequency control of pulse modulation technology (PWM).Run into great obstacle but apply on a large scale over 20 years, technical problem is a main cause, wherein most importantly harmonic wave and energy back, apply on a large scale on existing technical foundation as can not well solving, the possibility of result is catastrophic, no matter is to power grid environment or equipment self.

The three-phase PWM commutation technique is generally believed it is to address the above problem the most promising means, in the past several years have produced some patents, as Chinese patent CN1949645A, CN101001053A, U.S. Pat 20050093501, PCT patent PCT/JB2006/003334, PCT/US2005/033565 etc.Wherein a lot of is at the stable problem of exploring resolution system.The three-phase PWM commutation technique can realize not having the High Power Factor rectification of harmonic wave, also can realize the two-way transmission of energy simultaneously, but not be widely used in recent years, and generally accepted reason is that the high and serious common-mode voltage of circuit complexity, cost disturbs.U.S. Pat 5784269, US6046915 and US20090040800 have carried out exploration highly significant, and the power that high frequency is handled is reduced to the level suitable with power output, but still is total power, and can only one-way transmission.The three-phase current of what is more important three-phase rectifier has only two degrees of freedom, the controlled condition that the control mode of three-phase PWM commutation technique causes is unnecessary, when load is the active load of firm power, the current waveform that its standard is obtained by rectifier, thereby above dual mode has been handled unnecessary power, influenced the stability of system, what too much PWM modulated in the same system still more interacts.The low alternate rectifier of Chinese patent 200810006950.X and buck-boost converter circuit devcie are slightly many.

Summary of the invention

The objective of the invention is at Chinese patent, Chinese patent 01140014.5,, Chinese patent CN200810006950.X, U.S. Pat 5784269, US6046915, US20090040800, disclosed commutation technique improves on the basis, to adapt to the three-phase induction motor frequency control, double-fed wind generating, and similar needs carry out the rectification load demand of energy transmitted in both directions firm power.

For solving above-mentioned task, the solution that the present invention adopts is: 6 diodes that the bridge-type in the rectification circuit of former conventional three phase mains is connected are replaced by IGBT or other semiconductor switch device that can realize the reverse circulation of electric current, constitute main converter.In energy forward direction when circulation,, among these 6 IGBT, but for two IGBT Be Controlled conducting of the diode location of two conductings in the conventional three-phase bridge rectifier between the phase region of determining, remaining four must keep turn-offing by 16BT.The IGBT Be Controlled conducting of body diode forward conduction in parallel maybe can reduce tube voltage drop in the body.During the energy back circulation, among these 6 IGBT, must the Be Controlled conducting for flowing two IGBT of diode location of two conductings in forward energy in the conventional three-phase bridge rectifier between the phase region of determining, remaining four must keep turn-offing by IGBT, the body diode reverse of parallel connection in the IGBT body of conducting, current channel is kept by the IGBT of conducting.Rectifier filter capacitor capacity value should be very little, do not influence fully by the high phase of voltage in the three-phase electricity rectifier output voltage waveforms that mutually determined low with voltage, and this voltage fluctuation will be much smaller than operating current to the charging and discharging currents of described filter capacitor.So the voltage waveform of main converter output should be as shown in Figure 3, the motor variable-frequency speed-regulating control circuit of normal direct current input three-phase PWM output is because motor is typical symmetrical linear load, according to the transient power equilibrium principle, it is constant power load, current waveform should be as shown in Figure 4, no matter be forward direction or the back to.

Mediate in the three-phase electricity in main converter, being blocked of current potential, thus claim the blocking-up phase, as the B among Fig. 2 in bc and cd section.The blocking-up phase selector switch phase mutually shutoffs low with voltage that voltage is high that 3 semiconductor combinations bidirectional switchs are formed, with the blocking-up tremendously high frequency inductance that is connected, direction and size by the IGBT Control current of half-bridge form are communicated with main converter.

During the energy feedforward

As shown in Figure 1, buck-boost converter works in boosting mode, is zero A phase corresponding to the starting point phase place, forces the electric current of A phase to be exported by blocking-up phase selector switch inflow main converter between 0 to π/6 phase region, and size is:

$\mathrm{Ia}=\mathrm{Iaa}=\frac{\mathrm{Sin}\left(\mathrm{\ωt}\right)}{\mathrm{Sin}(\mathrm{\π}/3)}$

Original C phase current that flows into main converter will be reduced to:

$I_{\mathrm{bm}}=\frac{1}{\mathrm{Sin}(\mathrm{\ωt}+\mathrm{\π}/2)}-\frac{\mathrm{Sin}\left(\mathrm{\ωt}\right)\mathrm{Sin}(\mathrm{\ωt}+\mathrm{\π}/6)}{\mathrm{Sin}(\mathrm{\π}/3)\mathrm{Sin}(\mathrm{\ωt}+\mathrm{\π}/2)}=\frac{\mathrm{Sin}(t+4\mathrm{\π}/6)}{\mathrm{Sin}(\mathrm{\π}/3)}$

The B phase current then is

$I_b=I_{\mathrm{cm}}=I_{\mathrm{aa}}=\frac{\mathrm{Sin}(\mathrm{\ωt}+\mathrm{\π}/3)}{\mathrm{Sin}(\mathrm{\π}/3)}$

Therefore, we have obtained the perfect waveform of three-phase in this is interval.For-π/6 are between 0 phase region, and difference only is that sense of current is to flow out to the A phase by main converter, and what reduce is the absolute value of C phase negative current, and the whole course of work is so analogized.

Processing mode and result during energy back are identical, and only buck-boost converter works in the step-down state, and the Control current direction is opposite.

Thus, by the output current of constant power load standard rectifier, (BPCP) method is filled up in auxiliary blocking-up mutually, obtained one and do not used the perfect Active Power Factor Correction of any energy-storage travelling wave tube (APFC), and the power that high-frequency mode is handled only is:

$P_a=(\mathrm{\π}/6)\mathrm{Sin}(\mathrm{\π}/3){\∫}_0^{\mathrm{\π}/6}\mathrm{Sin}\left(\mathrm{\ωt}\right)\mathrm{Sin}(\mathrm{\ωt}+\mathrm{\π}/6)\mathrm{dt}=0.224$

Circuit has been kept and will have been compared reduction significantly with average power with common PWM rectifier with the installed capacity of high frequency switch mode processing power in the switching process, the what is more important system stability, no big common mode disturbances output, the while can be realized the transmitted in both directions of energy.

Description of drawings

The present invention is further detailed explanation below in conjunction with the drawings and specific embodiments:

Fig. 1: be the present invention's energy double-fed three phase electric machine frequency-changing speed-regulating driver circuit theory diagrams,

Fig. 2: be the voltage waveform of three-phase electricity,

Fig. 3: be the voltage waveform behind the three phase rectifier,

Fig. 4: be the rectifier current waveform of active firm power load standard,

Fig. 5: be that permanent power load energy double-fed blocking-up phase current as one of the present invention is filled up the rectification circuit schematic diagram.

Embodiment

Fig. 1 is the present invention's embodiment energy double-fed three phase electric machine frequency-changing speed-regulating driver circuit theory diagrams.Comprise four parts, main converter 100, blocking-up phase selector switch 200, buck-boost converter 300 and PWM frequency conversion sine-wave generator 400.Main converter 100 is made up of semiconductor IGBT switching tube 101,102,103,104,105,106 and filter capacitor 107, blocking-up phase selector switch 200 is made up of semiconductor combinations bidirectional switch 201,202,203, buck-boost converter 300 is by high-frequency inductor 301, buck IGBT switching tube 302 and 303 is formed, and PWM frequency conversion sine-wave generator 400 is by semiconductor IGBT switching tube 401,402,403,404,405,406 and be driven motor 407 and form.In the main converter 100, the emitter of semiconductor IGBT switching tube 101 is connected with 102 collector electrode, 103 emitter is connected with 104 collector electrode, 105 emitter is connected with 106 collector electrode, these three tie points are connected with A, B, the C three of three-phase electricity input 111 respectively, 101,103 and 105 collector electrode couples together and exports as the positive pole of main converter 100,102,104 and 106 the emitter utmost point couples together and exports as the negative pole of main converter 100, and the two ends of filter capacitor 107 are connected with the both positive and negative polarity output of main converter respectively.In blocking-up phase selector switch 200, semiconductor combinations bidirectional switch 201,202, an end of 203 is connected with A, B, the C three of three-phase electricity input 111 respectively, the other end connects together with an end of the high-frequency inductor 301 of buck-boost converter 300 and is connected, the other end of high-frequency inductor 301 is connected with 303 collector electrodes with the emitter of IGBT switching tube 302, and the emitter of IGBT switching tube 303 is connected with the negative pole output of main converter 100, and 302 collector electrodes are connected with the positive pole output of main converter 100.PWM frequency conversion sine-wave generator 400 in, the emitter of semiconductor IGBT switching tube 401 is connected with 402 collector electrode, 403 emitter is connected with 404 collector electrode, 405 emitter is connected with 406 collector electrode, the three-phase electricity output that these three tie points are respectively frequency adjustable be driven the input of motor 407 three-phases and be connected; Semiconductor IGBT switching tube 401,403 couples together with 405 collector electrode and is connected with the positive pole output of main converter, and 402,404 couple together to export with the negative pole of main converter with 406 the emitter utmost point and are connected.Main converter 100, blocking-up phase selector switch 200 and buck-boost converter 300 constitute the double-fed rectifier, PWM frequency conversion sine-wave generator 400 is as active load, according to the transient power equilibrium principle, be no matter constant power load is the energy feedforward, still feed back, the output current wave of rectifier is all by its standard.

Circuit working is in the energy fl transmission process of drive motors.

Semiconductor IGBT switching tube 101 in the main converter 100,102,103,104,105,106 can keep normal off will not control, form conventional rectifier bridge by the parallel diode in its body, also can be for two IGBT control conductings of the diode location of two conductings in the conventional three-phase bridge rectifier between the phase region of determining, remaining four must keep turn-offing by IGBT, maybe can reduce tube voltage drop.I.e. ab between phase region as shown in Figure 2 can allow IGBT105,104 conductings, bd between phase region, can allow IGBT101,104 conductings, df between phase region can allow IGBT101,106 conductings, fh between phase region, can allow IGBT103,106 conductings, hj between phase region can allow IGBT103,102 conductings, jl between phase region, can allow IGBT103,104 conductings, lm between phase region can allow IGBT105,104 conductings.

Blocking-up phase selector switch 200 is at ab between phase region as shown in Figure 2, allow semiconductor bi-directional combination switch 202,203 turn-off, and 201 conductings make A link to each other with inductance, bd between phase region, allow semiconductor bi-directional combination switch 201,202 turn-off, and 203 conductings make C link to each other with inductance, df between phase region, allow semiconductor bi-directional combination switch 201,203 turn-off, and 202 conductings make B link to each other with inductance, fh between phase region, allow semiconductor bi-directional combination switch 202,203 turn-off, and 201 conductings make A link to each other with inductance, hj between phase region, allow semiconductor bi-directional combination switch 201,202 turn-off, and 203 conductings make C link to each other with inductance, jl between phase region, allow semiconductor bi-directional combination switch 201,203 turn-off, and 202 conductings make B link to each other with inductance, lm between phase region, allow semiconductor bi-directional combination switch 202,203 turn-off, and 201 conductings make A link to each other with inductance.

Ab between phase region, the buck-boost converter Control current makes sense of current go into main converter by the A phase current, and size of current is to press the numerical value of power normalization and amassing of the electric corresponding mutually phase place sine value constantly of A; Bc between phase region, the buck-boost converter Control current makes sense of current go into main converter by the C phase current, and size of current is pressed the numerical value of power normalization and amassing of the electric corresponding mutually phase place sine value constantly of C; Cd between phase region, the buck-boost converter Control current makes sense of current go into the C phase by the main converter electric current, and size of current is pressed the numerical value of power normalization and amassing of the electric corresponding mutually sinusoidal absolute value of phase place constantly of A; De between phase region, the buck-boost converter Control current makes sense of current go into the B phase by the main converter electric current, and size of current is pressed the numerical value of power normalization and amassing of the electric corresponding mutually sinusoidal absolute value of phase place constantly of B;

The value of filter capacitor 107 capacity should not influence fully by the high phase of voltage in the three-phase electricity main converter output voltage waveforms that mutually determined low with voltage, and this voltage fluctuation to the charging and discharging currents of described filter capacitor much smaller than operating current.So the voltage waveform of main converter output should be as shown in Figure 3, the motor variable-frequency speed-regulating control circuit of normal direct current input three-phase PWM output is because motor is typical symmetrical linear load, according to the transient power equilibrium principle, it is constant power load, current waveform should be as shown in Figure 4, no matter be forward direction or the back to.So, can obtain the sine-wave current identical in the input of three-phase electricity with phase voltage.

Circuit working is in the energy back transmission course of control motor.

IGBT in the main converter and blocking-up gating period and the aforementioned energy of selector switch mutually feedover identically, and difference only is that the conducting of the IGBT in the main converter is necessary.Current waveform shape between each π/6 phase regions is identical with aforementioned energy feedforward, but direction is just opposite.

Fig. 5 is the present invention's the active constant power load standard of embodiment output current, and the blocking-up phase current is filled up the rectifier circuit schematic diagram, comprises four parts, main converter 100, blocking-up phase selector switch 200, booster converter 300 and active constant power load 400.Main converter 100 is made up of semiconductor diode 101,102,103,104,105,106 and filter capacitor 107, blocking-up phase selector switch 200 is made up of semiconductor combinations bidirectional switch 201,202,203, buck-boost converter 300 is by high-frequency inductor 301, and step-down IGBT switching tube 302,303 is formed.In the main converter 100, the positive pole of semiconductor diode 101 is connected with 102 negative pole, 103 positive pole and negative connection of 104,105 just with negative connection of 106, these three tie points are connected with A, B, the C three of three-phase electricity input 100 respectively, 101,103 and 105 negative pole couples together and exports as the positive pole of main converter 100, and 102,104 and 106 positive pole couples together as the negative pole output of main converter 100, and the two ends of filter capacitor 107 are connected with the both positive and negative polarity output of main converter respectively.In blocking-up phase selector switch 200, one end of semiconductor combinations bidirectional switch 201,202,203 is connected with A, B, the C three of three-phase electricity input 111 respectively, the other end connects together with an end of the high-frequency inductor 301 of buck-boost converter 300 and is connected, the other end of high-frequency inductor 301 is connected with 303 collector electrodes with the emitter of IGBT switching tube 302, the emitter of IGBT switching tube 303 is connected with the negative pole output of main converter 100, and 302 collector electrodes are connected with the positive pole output of main converter 100.Main converter 100, blocking-up phase selector switch 200 and booster converter 300 are combined as rectifier.

Main converter that is constituted by a diode and common three-phase commutation bridge operation principle are identical.The operating state and previous embodiment 1 circuit working of blocking-up phase selector switch and booster converter are identical in the energy fl transmission process of drive motors.

The value of filter capacitor 107 capacity should not influence fully by the high phase of voltage in the three-phase electricity voltage waveform that mutually determined low with voltage, and this voltage fluctuation to the charging and discharging currents of described filter capacitor much smaller than operating current.The voltage waveform of main converter output should be as shown in Figure 3, should be as shown in Figure 4 by the rectifier output current wave of constant power load standard.So, with previous embodiment 1 circuit working in the identical blocking-up phase current size and Orientation control mode of the energy fl transmission of drive motors, can obtain the sine-wave current identical in the input of three-phase electricity with phase voltage.

Certainly, the present invention's energy double-fed three phase electric machine frequency-changing speed-regulating driver also is regardless of and is limited to illustrated embodiment, as adopts mains switch, rectification circuit, buck-boost converter of other form etc., and these variations all drop within protection scope of the present invention.

Claims (4)

1. the present invention relates to a kind of three phase electric machine frequency variant speed regulating circuit, especially a kind of High Power Factor forward drive that is adapted to double-fed wind generating, the three phase electric machine frequency variant speed regulating circuit of High Power Factor energy back, it is characterized in that: circuit is made up of four parts, main converter 100, blocking-up phase selector switch 200, buck-boost converter 300 and PWM frequency conversion sine-wave generator 400; Described main converter 100 is made up of semiconductor IGBT switching tube 101,102,103,104,105,106 and filter capacitor 107, blocking-up phase selector switch 200 is made up of semiconductor combinations bidirectional switch 201,202,203, buck-boost converter 300 is made up of high-frequency inductor 301 and IGBT switching tube 302,303, and PWM frequency conversion sine-wave generator 400 is by semiconductor IGBT switching tube 401,402,403,404,405,406 and be driven motor 407 and form; In described main converter 100, the emitter of semiconductor IGBT switching tube 101 is connected with 102 collector electrode, 103 emitter is connected with 104 collector electrode, 105 emitter is connected with 106 collector electrode, these three tie points are connected with A, B, the C three of three-phase electricity input 111 respectively, 101,103 and 105 collector electrode couples together and exports as the positive pole of main converter 100,102,104 and 106 the emitter utmost point couples together and exports as the negative pole of main converter 100, and the two ends of filter capacitor 107 are connected with the both positive and negative polarity output of main converter respectively; In described blocking-up phase selector switch 200, described semiconductor combinations bidirectional switch 201,202 is connected with A, B, the C three of three-phase electricity input 111 respectively with an end of 203, the other end connects together with an end of the high-frequency inductor 301 of described buck-boost converter 300 and is connected, the emitter of the other end of described high-frequency inductor 301 and described IGBT switching tube 302 is connected with, 303 collector electrode, the emitter of described IGBT switching tube 303 connects the negative pole output of described main converter 100, and 302 collector electrodes connect the positive pole output of main converter 100; In described PWM frequency conversion sine-wave generator 400, the emitter of semiconductor IGBT switching tube 401 is connected with 402 collector electrode, 403 emitter is connected with 404 collector electrode, 405 emitter is connected with 406 collector electrode, the three-phase electricity output that these three tie points are respectively frequency adjustable be driven the input of motor 407 three-phases and be connected, semiconductor IGBT switching tube 401,403 couples together with 405 collector electrode and is connected with the positive pole output of main converter, and 402,404 couple together to export with the negative pole of main converter with 406 the emitter utmost point and are connected; Described main converter 100, blocking-up phase selector switch 200 and buck-boost converter 300 constitute the double-fed rectifier, and described PWM frequency conversion sine-wave generator 400 is as active load.

2. three phase mains energy double-fed three phase electric machine frequency variant speed regulating circuit according to claim 1, it is characterized in that: the transmission direction of electric flux and size are by described active load PWM frequency conversion sine-wave generator 400 decisions, described main converter 100 keep its positive-negative output ends respectively with three-phase electricity in the highest and minimum low impedance path mutually of voltage of voltage, be connected in the body diode forward conduction of the IGBT switching tube of the highest phase of voltage and described main converter 100 positive poles during the energy feedforward, form low impedance path, this IGBT switch controls conducting also may command is turn-offed, be connected in the body diode forward conduction of the IGBT switching tube of minimum phase of voltage and described main converter 100 negative poles, form low impedance path, this IGBT switch controls conducting also may command is turn-offed; The body diode that is connected in the IGBT switching tube of the highest phase of voltage and described main converter 100 positive poles during energy back also is blocked, this IGBT switch must the Be Controlled conducting form low impedance path, the body diode that is connected in the IGBT switching tube of minimum phase of voltage and described main converter 100 negative poles also is blocked, form low impedance path, this IGBT switch must the Be Controlled conducting form low impedance path.

3. according to claim 1 and 2 described three phase mains energy double-fed three phase electric machine frequency variant speed regulating circuits, it is characterized in that: any time of three-phase input power supply always has a phase voltage the highest, one phase voltage is minimum, voltage the highest by described main converter 100 101,103,105 in be attached thereto the IGBT switch and be connected to main converter 100 positive output ends, the minimum phase of voltage by main converter 100 102,104,106 in the IGBT switch that is attached thereto be connected to main converter 100 negative outputs; Mediate in main converter, being blocked of current potential, promptly so-called blocking-up phase, by described blocking-up phase selector switch 200 201,202,203 in the semiconductor combinations bidirectional switch that is attached thereto be connected to the high-frequency inductor 301 of described buck-boost converter 300; 2 complete π are divided into 12 beats in the cycle, at before and after the mutually electric zero passage of described blocking-up ± π/6 phase regions between, by described its size of current of buck-boost converter 300 standards and direction; When described active load PWM frequency conversion sine-wave generator 400 control electric fluxs feedover, when blocking-up is between 0 to π/6 phase region mutually, described its sense of current of buck-boost converter 300 standards is exported to described main converter 100 by three-phase current, blocking-up is in mutually-π/6 are between phase region the time, described its sense of current of buck-boost converter 300 standards by the output stream of main converter 100 to described blocking-up phase; When described active load PWM frequency conversion sine-wave generator 400 control electric fluxs feed back, when blocking-up is between 0 to π/6 phase region mutually, described its sense of current of buck-boost converter 300 standards by the output stream of main converter 100 to described blocking-up phase, blocking-up is in mutually-π/6 are between 0 phase region the time, described its sense of current of buck-boost converter 300 standards by three-phase current to described main converter 100 outputs; The size of electric current all is to press the numerical value of power normalization and amassing of the corresponding moment phase place sine value of blocking-up by the size of current of described active load PWM frequency conversion sine-wave generator 400 decisions; So the low impedance path by described its output of main converter 100 maintenances and all the other two-phases provides required residual current, and each phase current of three-phase electricity just all is the sine wave of standard after finally synthesizing under the normal stable case.

4. one kind adapts to the three-phase high power factor rectification circuit that firm power is loaded, it is characterized in that: circuit is made up of four parts, main converter comprises three-phase bridge and filter capacitor that 6 common low frequency diodes are formed, blocking-up phase selector switch and booster converter; Described main converter filter capacitor capacity is very little, do not influence fully by the high phase of voltage in the three-phase electricity voltage waveform that mutually determined low with voltage, and this voltage fluctuation to the charging and discharging currents of described filter capacitor much smaller than operating current, described blocking-up phase selector switch, comprise 3 semiconductor combinations bidirectional switchs, described booster converter comprises that two IGBT switching tubes of a high-frequency inductor and half-bridge form are formed; In described blocking-up phase selector switch, one end of described 3 semiconductor combinations bidirectional switchs is connected with the three-phase electricity of input respectively, the other end connects together with an end of the high-frequency inductor of described booster converter and is connected, the described high-frequency inductor other end is connected with the intermediate point of described half-bridge form IGBT switching tube, the emitter of the following IGBT switching tube of described half-bridge form connects the negative pole output of described main converter, and the collector electrode of last IGBT connects the positive pole output of main converter; Described rectifier is the output current wave that is inversely proportional to the rectifier output voltage by the constant power load standard, the i.e. blocking-up mutually that described blocking-up phase selector switch is selected to mediate in the three-phase electricity is connected with described high-frequency inductor, when blocking-up is between 0 to π/6 phase region mutually, described its electric current of booster converter standard is flowed out mutually by blocking-up, blocking-up is in mutually-and π/6 are between 0 phase region the time, its sense of current of described booster converter standard flows to the blocking-up phase, and the size of electric current all is to press the numerical value of power normalization and amassing of the corresponding moment phase place sine value absolute value of blocking-up by the constant power load decision; Diode by described main converter conducting like this keeps the low impedance path of its output and all the other two-phases that required residual current is provided, and each phase current of three-phase electricity just all is the sine wave of standard after finally synthesizing under the normal stable case.

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