CN102185556A - Power joint control method for cage motor back-to-back frequency converter and frequency converter - Google Patents

Abstract

The invention discloses a power joint control method for a cage motor back-to-back frequency converter and a frequency converter using the method. Aiming at the characteristic that a load of the cage motor back-to-back frequency converter changes dramatically, a model of fluctuation of direct-current bus voltage is established according to change of load current and alternating-current voltage on the wire inlet network side of a rectifier. By adoption of a power joint control technology, the direct-current bus voltage of the system is not influenced by sudden change of the load current and the change of the alternating-current voltage on the wire inlet network side of the rectifier under a bad working condition. By execution of an ideal power joint control strategy, the power absorbed by the rectifier from a power grid is equal to the power output to the load side when the load and the power grid of the system change suddenly, so the fluctuation of the direct-current bus voltage is reduced; meanwhile, the current flowing into a filter capacitor is decreased and the service life of the capacitor is prolonged.

Description

Squirrel-cage motor is transducer power combination control method and frequency converter back-to-back

Technical field

The squirrel-cage motor that the present invention relates to squirrel-cage motor transducer power combination control method back-to-back and adopt this method is frequency converter back-to-back, is applicable to the squirrel-cage motor frequency conversion speed-adjusting system of inverter supply back-to-back.

Background technology

Back-to-back in the frequency converter vector control system, frequency converter is made up of rectifier and inverter back-to-back at squirrel-cage motor.The control of rectifier and inverter is separately carried out on traditional controlling schemes, controls DC bus-bar voltage and motor speed respectively.

Wherein the fluctuation of the DC bus-bar voltage controlled of rectifier mainly contains two factors and causes: the fluctuation of the fluctuation of grid side voltage and inverter power output, the variation of load is then depended in the fluctuation of inverter power output.The control of traditional rectifier is to adopt to encircle in two of a direct voltage outer shroud and active current, the reactive currents respectively DC bus-bar voltage to be regulated.DC bus-bar voltage is given to be that system handles according to actual conditions, is a fixed value.And the output of DC bus-bar voltage ring is given as what encircle in the active current, and reactive current is given and to be fixed on power factor is to be set to 0 under 1 the situation.

When the grid side voltage fluctuation and or since the variation of load cause under the situation that the inverter power output changes, error by direct voltage between the given and feedback causes the variation of direct voltage pi regulator output, active current is given to change thereby make, and it is given that the control by the active current pi regulator makes that DC bus-bar voltage is followed DC bus-bar voltage on new balance point.

Change the back in DC bus-bar voltage in this case and caused by error, so the DC bus-bar voltage fluctuation is quite serious, the electric current of inflow and outflow dc filter capacitor is bigger, is unfavorable for the long-term stability operation of system.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, a kind of squirrel-cage motor transducer power combination control method and frequency converter back-to-back are provided.Adopt following technical scheme:

A kind of squirrel-cage motor is the transducer power combination control method back-to-back, and power jointly controls the specific implementation process and is:

The first step: by the communication between rectifier controller and the circuit control device, obtain power and jointly control required parameter, the dq shaft current of the dq axle component of described parameter squirrel-cage motor number of pole-pairs, magnetic linkage, squirrel-cage motor rotating speed, inverter output.

Second step: rectifier adopts power combination control method under the virtual electrical network flux linkage orientation according to the parameter information that obtains from inverter; Voltage on line side and inverter relevant parameter information are joined in the given calculating of active current, and then the expression formula of fluctuation of rectifier DC busbar voltage and load current and net top-cross stream voltage fluctuation is as follows:

$\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}+T_e^{\′}\mathrm{\Δe}+Z_0^{\′}\mathrm{\Δ}{i}_{\mathrm{Inv}}$

Wherein:

$T_e^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δe}}=\frac{Z_L(G_{\mathrm{ein}}-G_E{G}_k)}{\mathrm{\Δ}}$

$Z_0^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δ}{i}_{\mathrm{Inv}}}=\frac{-Z_L(1-G_I{G}_k)}{\mathrm{\Δ}}$

Wherein each transfer function is as follows:

$G_k=\frac{3\mathrm{KE}}{V_{\mathrm{dc}}}---\left(10\right)$

$Z_L\left(S\right)=\frac{1}{{\mathrm{SC}}_{\mathrm{dc}}}---\left(11\right)$

$G_z=\frac{I_{\mathrm{Rec}}}{V_{\mathrm{dc}}}---\left(12\right)$

$G_{\mathrm{ein}}=\frac{2K{I}_q^{*}}{V_{\mathrm{dc}}}---\left(13\right)$

$G_U=K_P+\frac{K_i}{S}---\left(14\right)$

Can obtain $T_e^{\′}=Z_0^{\′}=0,\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}.$

Adopt the frequency converter of described method, comprise system control unit, described system control unit comprises rectifier controller, circuit control device and communication unit between the two, circuit control device obtains motor speed signal, current of electric, obtain the d axle and the q axle component of magnetic linkage by motor model, obtain torque current signal from described current of electric by rotor flux angle and coordinate transform; Described communication unit is used for described motor speed signal, the d axle of described magnetic linkage and q axle component, described torque current signal is transferred to rectifier controller, described commutation controller 15 is according to power combination control method under the described virtual electrical network flux linkage orientation, adopt described transfer function (10), (11), (12), (13) and (14) form the algorithm that power jointly controls, jointly control component according to the error between current d-c bus voltage value and the set-point and power and calculate the given of active current, thereby make the rectifier DC busbar voltage only be subjected to the given influence of DC bus-bar voltage, irrelevant with load current and net top-cross stream change in voltage.

By the communication between rectifier controller and the circuit control device, set up data transmission channel, the power combination control method of employing under virtual electrical network flux linkage orientation control strategy realized squirrel-cage motor high reliability, the high stability operation of frequency converter back-to-back.

The frequency converter back-to-back of said method and this method of employing utilizes the small-signal modeling of total system, directly obtains to influence the stable parameter of DC bus-bar voltage, thereby just effectively controls in advance before this factor makes the DC bus-bar voltage fluctuation.The enforcement of this method has reduced dc bus fluctuation under the bad working environments, has more reduced to flow into the electric current of filter capacitor simultaneously, has increased the electric capacity life-span.

Description of drawings

Fig. 1 is a rectifier small-signal control chart under the virtual electrical network flux linkage orientation;

Fig. 2 jointly controls block diagram for power under the virtual electrical network flux linkage orientation;

Fig. 3 is the converter plant figure of the topological structure back-to-back of employing joint Power control;

Among the figure: 1, three-phase alternating current input power supply; 2, mains switch; 3, power supply A phase current transducer; 4, power supply C phase current transducer; 5, the frequency converter major loop of topological structure back-to-back; 6, rectifier module; 7, DC filtering module; 8, inverter module; 9, motor A phase current transducer; 10, motor C phase current transducer; 11, controlled squirrel-cage motor; 12, voltage sensor; 13, rectification module triggers optical fiber; 14, system start-up signal and velocity setting unit; 15, rectifier controller; 16: circuit control device 17: by 15,16 and 19 system control units of forming; 18, encoder; 19, the communication unit between rectifier controller and the circuit control device 20, inverter module trigger optical fiber in the system control unit;

Embodiment

Below in conjunction with specific embodiment, the present invention is described in detail.

Embodiment 1

Under virtual electrical network flux linkage orientation control strategy, active current is i _q, and reactive current is i _dIn following statement, with subscript " Rec " expression rectifier (rectifier), and the definition rectifier outputs to dc bus filter capacitor direction for just, subscript " Inv " expression inverter (inverter), and definition from dc bus filter capacitor inflow inverter direction for just.P represents active power, and Q represents reactive power.ψ represents magnetic linkage.Subscript " α, β, d, q " is then represented α axle under the α β coordinate system and d axle and the q axle under β axle and the dq coordinate system respectively.

By Mathematical Modeling under the virtual electrical network flux linkage orientation α β coordinate system as can be known:

$\left[\begin{array}{c}{P}_{\mathrm{Rec}}\\ Q_{\mathrm{Rec}}\end{array}\right]=\mathrm{\ω}\left[\begin{array}{cc}-{\mathrm{\ψ}}_{\mathrm{\β}\_\mathrm{Rec}}& {\mathrm{\ψ}}_{\mathrm{\α}\_\mathrm{Rec}}\\ {\mathrm{\ψ}}_{\mathrm{\α}\_\mathrm{Rec}}& {\mathrm{\ψ}}_{\mathrm{\β}\_\mathrm{Rec}}\end{array}\right]\left[\begin{array}{c}{i}_{\mathrm{\α}\_\mathrm{Rec}}\\ i_{\mathrm{\β}\_\mathrm{Rec}}\end{array}\right]---\left(1\right)$

Transform under the dq coordinate system:

$\left[\begin{array}{c}{P}_{\mathrm{Rec}}\\ Q_{\mathrm{Rec}}\end{array}\right]=\mathrm{\ω}\left[\begin{array}{cc}-{\mathrm{\ψ}}_{q\_\mathrm{Rec}}& {\mathrm{\ψ}}_{d\_\mathrm{Rec}}\\ {\mathrm{\ψ}}_{d\_\mathrm{Rec}}& {\mathrm{\ψ}}_{q\_\mathrm{Rec}}\end{array}\right]\left[\begin{array}{c}{i}_{d\_\mathrm{Rec}}\\ i_{q\_\mathrm{Rec}}\end{array}\right]---\left(2\right)$

The motor of same inverter power supply is pressed under the vector control of rotor flux linkage orientation, and the machine torque of output is:

T _Inv＝1.5P(ψ _{d_Inv}i _{q_Inv}-ψ _{q_Inv}i _{d_Inv})(3)

P is arranged again _Inv=ω _InvT _Inv, can calculate to motor provides the inverter active power of output of power supply and be:

P _Inv＝1.5P(ψ _{d_Inv}i _{q_Inv}-ψ _{q_Inv}i _{d_Inv})ω _Inv (4)

According to the power-balance principle, system's input power equals system's power output, and in the native system, power output comprises switching losses such as motor power output, the loss of electric machine, rectifier and inverter, ideally ignores next three P as can be known _Rec=P _Inv, system is 1 in power factor, i.e. i _dCan obtain under=0 operating mode:

$C_{\mathrm{dc}}\frac{{\mathrm{dv}}_{\mathrm{dc}}}{\mathrm{dt}}=i_{\mathrm{Rec}}-i_{\mathrm{Inv}}---\left(5\right)$

3ei＝v _dci _Rec (6)

$i=K{i}_q^{*}---\left(7\right)$

In the following formula, v _DcBe DC bus-bar voltage, i _RecBe rectifier output current, i _InvBe input current of inverter, e, i are respectively rectifier net side phase voltage and phase current effective value,

Be active current (q shaft current) set-point.In desirable power factor is under 1 operating mode, and q shaft current set-point is a net side phase current peak value.

Utilize the linear analytical method of small-signal, can obtain the rectifier steady-state equation and the transient state equation is as follows:

$\left\{\begin{array}{c}3\mathrm{KE}{I}_q^{*}=V_{\mathrm{dc}}{I}_{\mathrm{Rec}}\\ I_{\mathrm{Rec}}=I_{\mathrm{Inv}}\end{array}\right.---\left(8\right)$

$\left\{\begin{array}{c}\mathrm{\Δ}{i}_{\mathrm{Rec}}=\frac{3\mathrm{KE}}{V_{\mathrm{dc}}}\mathrm{\Δ}{i}_q^{*}+\frac{3K{I}_q^{*}}{V_{\mathrm{dc}}}\mathrm{\Δe}-\frac{I_{\mathrm{Rec}}}{V_{\mathrm{dc}}}\mathrm{\Δ}{v}_{\mathrm{dc}}\\ C_{\mathrm{dc}}\frac{\mathrm{d\Δ}{v}_{\mathrm{dc}}}{\mathrm{dt}}=\mathrm{\Δ}{i}_{\mathrm{Rec}}-\mathrm{\Δ}{i}_{\mathrm{Inv}}\end{array}\right.---\left(9\right)$

Wherein according to the transient state equation, can draw under the virtual electrical network flux linkage orientation shown in Figure 1 rectifier based on the control block diagram of small-signal model.Each transfer function is as follows among Fig. 1:

$G_k=\frac{3\mathrm{KE}}{V_{\mathrm{dc}}}---\left(10\right)$

$Z_L\left(S\right)=\frac{1}{{\mathrm{SC}}_{\mathrm{dc}}}---\left(11\right)$

$G_z=\frac{I_{\mathrm{Rec}}}{V_{\mathrm{dc}}}---\left(12\right)$

$G_{\mathrm{ein}}=\frac{2K{I}_q^{*}}{V_{\mathrm{dc}}}---\left(13\right)$

$G_U=K_P+\frac{K_i}{S}---\left(14\right)$

So in the expression formula of this control strategy Down Highway voltage fluctuation and load current and the voltage fluctuation of net top-cross stream:

$\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}+T_e\mathrm{\Δe}+Z_0\mathrm{\Δ}{i}_{\mathrm{Inv}}---\left(15\right)$

In following formula:

$T_{\mathrm{ref}}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}}=\frac{G_k{Z}_L{G}_U}{\mathrm{\Δ}}---\left(16\right)$

$T_e=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δe}}=\frac{Z_L{G}_{\mathrm{ein}}}{\mathrm{\Δ}}---\left(17\right)$

$Z_0=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δ}{i}_{\mathrm{Inv}}}---\left(18\right)$

Δ＝1+Z _L(G _kG _U+G _z)(19)

If so if busbar voltage is given fixing, then busbar voltage is subjected to load disturbance Δ i _InvProduce fluctuation with the influence of grid disturbance Δ e, make T if adopt power to jointly control algorithm _e=0, Z ₀=0, then the rectifier busbar voltage is not subjected to the influence of load current and the voltage fluctuation of net top-cross stream.

So the present invention adopts transfer function G among Fig. 1 _kFront end add the small-signal Δ e and the transfer function-G of line voltage _EProduct and inverter current small-signal Δ i _InvWith transfer function G _iThe algebraical sum of product, obtained power combination control method under the virtual electrical network flux linkage orientation as shown in Figure 2 like this.Then the expression formula of fluctuation of rectifier DC busbar voltage and load current and net top-cross stream voltage fluctuation is as follows:

$\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}+T_e^{\′}\mathrm{\Δe}+Z_0^{\′}\mathrm{\Δ}{i}_{\mathrm{Inv}}---\left(20\right)$

Wherein:

$T_e^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δe}}=\frac{Z_L(G_{\mathrm{ein}}-G_E{G}_k)}{\mathrm{\Δ}}---\left(21\right)$

$Z_0^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δ}{i}_{\mathrm{Inv}}}=\frac{-Z_L(1-G_I{G}_k)}{\mathrm{\Δ}}---\left(22\right)$

With above-mentioned each transfer function substitution following formula, then can obtain

So it is the rectifier DC busbar voltage only is subjected to the given influence of DC bus-bar voltage, irrelevant with load current and net top-cross stream change in voltage in theory.And in the real system, DC bus-bar voltage is given as steady state value, so DC bus-bar voltage all can keep constant under transient state and stable situation.

Embodiment 2

The present invention's frequency converter back-to-back comprises source current transducer 3 and 4, frequency converter major loop 5, motor current sensor 9 and 10 voltage sensors 12, triggers in optical fiber 13 and 20, system start-up signal and velocity setting unit 14, system control unit 17, encoder 18 and the system control unit communication unit 19 between the rectifier controller and circuit control device and form.

System's input is that the controlled device of system is a squirrel-cage motor 11 by the three-phase alternating current input voltage 1 of mains switch 2 controls; Wherein the frequency converter major loop 5 of topological structure comprises rectification module 6, DC filtering module 7 and inversion module 8 back-to-back, and system control unit 17 comprises that rectifier controller 15, circuit control device 16 reach communication unit 19 between the two.The use of system triggers optical fiber 13 then is in order to reach the isolation of system high pressure and low-pressure section, to have improved the ability of the anti-electromagnetic interference of system.

Rectifier controller 15 is used to control DC bus-bar voltage and is stabilized in given numerical value, specifically realize its function in the following manner: electrical network A, C is connected to rectifier controller 15 by power supply A phase current transducer 3 and power supply C phase current transducer 4, voltage sensor 12 is used to measure the DC bus-bar voltage on the DC filtering module 7, export this DC bus-bar voltage and give rectifier controller 15, rectifier controller 15 triggers the grid emitter voltage of the power electronic device IGBT in the optical fiber 13 control rectifier modules 6 by rectification module, thereby IGBT is opened or turn-off, make dc voltage stability above the stream filtration module 7 at certain given numerical value.

Circuit control device 16 is by voltage sensor 12, DC bus-bar voltage and inverter output current that motor A phase current transducer 9 and motor C phase current sensor measurement obtain, by squirrel-cage motor Model Calculation rotor flux, and it is decomposed two-phase select on coordinate system d axle and the q axle, and then pass through speed feedback signal, control the rotating speed of controlled squirrel-cage motor 11, specifically realize its function in the following manner: the A of motor, C is connected to circuit control device 16 by motor A phase current transducer 9 and motor C phase current transducer 10, and circuit control device 16 receives the DC bus-bar voltage from voltage sensor 12 simultaneously; System start-up and velocity setting signal then are connected to circuit control device 16 by system start-up signal and velocity setting unit 14, be used for providing rate signal and electric motor starting signal to circuit control device 16, encoder 18 is used to measure the feedback speed signal of controlled squirrel-cage motor, to circuit control device 16 these feedback speed signals of output.Circuit control device 16 triggers the grid emitter voltage of the power electronic device IGBT in the optical fiber 20 control inverter modules 8 by inverter module, thereby IGBT is opened or turn-offs, thereby reaches the purpose that motor speed is controlled.Power jointly controls the communication unit 19 that reaches between the two by the rectifier controller in the system control unit 17 15, circuit control device 16 and carries out transfer of data.Circuit control device 16 obtains motor speed signal by encoder 18, measure current of electric by motor A phase current transducer 9 and motor C phase current transducer 10, obtain the d axle and the q axle component of magnetic linkage by motor model, obtain torque current signal from the current of electric that measures by rotor flux angle and coordinate transform.Communication unit 19 in the system control unit is responsible for the above-mentioned motor speed signal that obtains, the d axle of magnetic linkage and q axle component, torque current signal is transferred to rectifier controller 15, power combination control method under 15 bases of commutation controller virtual electrical network flux linkage orientation as shown in Figure 2, adopt the transfer function (10) in the foregoing description 1, (11), (12), (13) and (14) form the algorithm that power jointly controls, jointly control component according to the error between current d-c bus voltage value and the set-point and power and calculate the given of active current, thereby make the rectifier DC busbar voltage only be subjected to the given influence of DC bus-bar voltage, irrelevant with load current and net top-cross stream change in voltage.

Should be understood that, for those of ordinary skills, can be improved according to the above description or conversion, and all these improvement and conversion all should belong to the protection range of claims of the present invention.

Claims (2)

1. squirrel-cage motor transducer power combination control method back-to-back is characterized in that power jointly controls the specific implementation process and is:

The first step: by the communication between rectifier controller and the circuit control device, obtain power and jointly control required parameter, described parameter comprises the dq shaft current that dq axle component, squirrel-cage motor rotating speed, the inverter of squirrel-cage motor number of pole-pairs, magnetic linkage are exported;

Second step: rectifier adopts power combination control method under the virtual electrical network flux linkage orientation according to the parameter information that obtains from inverter; Voltage on line side and inverter relevant parameter information are joined in the given calculating of active current, and then the expression formula of fluctuation of rectifier DC busbar voltage and load current and net top-cross stream voltage fluctuation is as follows:

$\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}^{*}+T_e^{\′}\mathrm{\Δe}+Z_0^{\′}\mathrm{\Δ}{i}_{\mathrm{Inv}}$

Wherein:

$T_e^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δe}}=\frac{Z_L(G_{\mathrm{ein}}-G_E{G}_k)}{\mathrm{\Δ}}$

$Z_0^{\′}=\frac{\mathrm{\Δ}{v}_{\mathrm{dc}}}{\mathrm{\Δ}{i}_{\mathrm{Inv}}}=\frac{-Z_L(1-G_I{G}_k)}{\mathrm{\Δ}}$

Wherein each transfer function is as follows:

$G_k=\frac{3\mathrm{KE}}{V_{\mathrm{dc}}}---\left(10\right)$

$Z_L\left(S\right)=\frac{1}{{\mathrm{SC}}_{\mathrm{dc}}}---\left(11\right)$

$G_z=\frac{I_{\mathrm{Rec}}}{V_{\mathrm{dc}}}---\left(12\right)$

$G_{\mathrm{ein}}=\frac{2K{I}_q^{*}}{V_{\mathrm{dc}}}---\left(13\right)$

$G_U=K_P+\frac{K_i}{S}---\left(14\right)$

Can obtain $T_e^{\′}=Z_0^{\′}=0,\mathrm{\Δ}{v}_{\mathrm{dc}}=T_{\mathrm{ref}}\mathrm{\Δ}{v}_{\mathrm{dc}}$

2. adopt the frequency converter of the described method of claim 1, it is characterized in that, comprise system control unit, described system control unit comprises rectifier controller, circuit control device and communication unit between the two, circuit control device obtains motor speed signal, current of electric obtains the d axle and the q axle component of magnetic linkage by motor model, obtains torque current signal by rotor flux angle and coordinate transform from described current of electric; Described communication unit is used for described motor speed signal, the d axle of described magnetic linkage and q axle component, described torque current signal is transferred to rectifier controller, described commutation controller 15 is according to power combination control method under the described virtual electrical network flux linkage orientation, adopt described transfer function (10), (11), (12), (13) and (14) form the algorithm that power jointly controls, jointly control component according to the error between current d-c bus voltage value and the set-point and power and calculate the given of active current, thereby make the rectifier DC busbar voltage only be subjected to the given influence of DC bus-bar voltage, irrelevant with load current and net top-cross stream change in voltage.

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