CN104377725A - Phase-locked-loop-free direct power prediction control method for three-phase converter - Google Patents

Abstract

The invention discloses a phase-locked-loop-free direct power prediction control method for a three-phase converter. The method is implemented under a synchronous rotating coordinate system, and no phase-locked loop is needed. According to the fact that a control system is delayed by two beats actually, sampling frequency which is two times of carrier frequency is adopted for reducing influences on prediction accuracy of the output power and current of the next beat and simplifying prediction calculation, complex calculation is not needed, the grid connection power, grid connection current and network voltage value of the next beat can be calculated accurately, control precision is improved, and output of a three-phase converter circuit of the next carrier cycle is obtained through calculation. The control method is simple and easy, fixed-frequency phase-locked-loop-free direct power prediction of the three-phase converter can be achieved, and the method is prone to engineering.

Description

A kind of no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm

Technical field

The present invention relates to a kind of no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm, belong to electric and electronic technical field.

Background technology

Three-phase DC/AC current transformer has can realize alternating current-direct current bi-directional power flow, power factor is adjustable, grid-connected current sine degree high, in recent years along with the fast development of distributed power generation obtains research and apply widely, its performance directly has influence on the quality of power supply of distributed power generation.In numerous control method, direct Power Control (direct power control, DPC) has the advantage that control algolithm is simple, power factor can be in harmonious proportion good dynamic property.DPC comes from the direct torque control (Direct torque control, DTC) of motor, and DTC does not need to control electric current, selects voltage vector according to sector and demand by switch list, realizes the direct control of motor torque and magnetic linkage.According to same principle, DPC is applied in 3-phase power converter, three-phase grid-connected converter can be realized and gain merit and the instantaneous power control of reactive power.

DPC realizes power by Hysteresis control to control, this causes the change of running breaker in middle frequency, bring very large difficulty to power circuit and design of Cooling System, and broadband is unfavorable for the design of grid-connected filter, thus reduces the output quality of power supply of grid-connected converter.For above problem, propose and adopt fixed switching frequency DPC scheme.But fixed direct Power Control (the constant frequence DPC frequently of tradition, CF-DPC) current transformer output voltage is obtained by closed-loop control, this needs to adjust to obtain good dynamic and static state performance to closed loop control parameters, and the performance of numerically controlled time delay also influential system.The difficult problem such as to adjust for digital control delay, controling parameters, for improving control performance further, Prediction and Control Technology is introduced in CF-DPC, and Direct Power PREDICTIVE CONTROL (predictive DPC, P-DPC) is the dead beat optimal control realizing grid-connected power based on Mathematical Modeling.Traditional PREDICTIVE CONTROL is open-loop prediction, clap time delay for one and carry out PREDICTIVE CONTROL, have ignored the time delay comprising the present sample control cycle having little time to upgrade duty ratio and the next control cycle worked, next claps output variable to be difficult to accurately predicting, and then affects control precision.

DPC adopts space vector pulse width modulation (space vector pulse width modulation, SVPWM) realize, need to carry out line voltage phase-locked to obtain mains frequency and phase angle, which increase the operand controlling difficulty and control system, reduce efficiency." the no phase-locked loop control strategy of two-way three-phase AC/DC current transformer. Proceedings of the CSEE; 2013; 33 (36): 79-87 " propose the no phase-locked loop control strategy of two-way three-phase AC/DC current transformer, but still need by increasing reactive power closed-loop adjustment, given frequency is adjusted in real time, solve frequency given different with electrical network actual frequency time the departure that causes." Hardware delay compensation of no phase-locked loop Synchronous Reference Frame Transform detection method. Proceedings of the CSEE; 2008; 28 (27): 78-83 " propose no phase-locked loop Synchronous Reference Frame Transform detection method, still need introduce phase compensation angle in synchronous coordinate inverse-transform matrix and hardware time delay is compensated.

Summary of the invention

The object of the invention is to overcome deficiency of the prior art, a kind of no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm is provided, the method realizes under synchronous rotating frame, without the need to carrying out phase lock control to electrical network, and realize directly controlling grid-connected power dead beat by PREDICTIVE CONTROL.

For achieving the above object, the technical solution adopted in the present invention is: a kind of no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm, comprises the following steps:

Step one: in (k-1) T, (k-1/2) T, kT, (k+1/2) T, (k+1) T, (k+3/2) T, (k+2) T moment, respectively to three-phase power grid voltage e _a, e _b, e _cwith three-phase grid current i _a, i _b, i _csample, T is a triangular carrier cycle of PWM, and k is integer;

Step 2: the three-phase power grid voltage obtained of step one being sampled and three-phase grid electric current, respectively through Clark conversion and Park conversion, obtain the three-phase power grid voltage vector e under synchronous rotating frame _d, e _qwith three-phase grid current vector i _d, i _q;

Step 3: according to instantaneous power theory, calculates instantaneous active power P and reactive power Q:

$\left[\begin{array}{c}P\\ Q\end{array}\right]=\frac{3}{2}\left[\begin{array}{cc}{e}_d& e_q\\ e_q& -e_d\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]$

Step 4: according to the active-power P in (k+1/2) T moment ^mid(k) and reactive power Q ^midk (), the active-power P (k) in kT moment and reactive power Q (k), calculate (k+1) T moment active power predicted value P ₁and reactive power predicted value Q (k+1) ₁(k+1):

$\left[\begin{array}{c}{P}_1(k+1)\\ Q_1(k+1)\end{array}\right]=2\left[\begin{array}{c}{P}^{\mathrm{mid}}\left(k\right)\\ Q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}P\left(k\right)\\ Q\left(k\right)\end{array}\right]$

Step 5: according to the grid-connected current in (k+1/2) T moment with the grid-connected current i in kT moment _d(k) and i _qk (), calculates the grid-connected current predicted value i in (k+1) T moment _d1and i (k+1) _q1(k+1):

$\left[\begin{array}{c}{i}_{d1}(k+1)\\ i_{q1}(k+1)\end{array}\right]=2\left[\begin{array}{c}{i}_d^{\mathrm{mid}}\left(k\right)\\ i_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}{i}_d\left(k\right)\\ i_q\left(k\right)\end{array}\right]$

Step 6: the line voltage according to (k+1/2) T moment is with the line voltage in kT moment is e _d(k) and e _qk (), calculates the line voltage predicted value e in (k+1) T moment _d1and e (k+1) _q1(k+1):

$\left[\begin{array}{c}{e}_{d1}(k+1)\\ e_{q1}(k+1)\end{array}\right]=2\left[\begin{array}{c}{e}_d^{\mathrm{mid}}\left(k\right)\\ e_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}{e}_d\left(k\right)\\ e_q\left(k\right)\end{array}\right]$

Step 7: calculate (k+1) T to (k+2) T moment current transformer output voltage vector v _dand v (k+1) _q(k+1):

$\left\{\begin{array}{c}{v}_d(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{d1}(k+1)\\ [P_{\mathrm{ref}}(k+2)-P_1(k+1)]+e_{q1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ -Q_1(k+1)\left]\right\}+e_{d1}(k+1)-{\mathrm{\ω}}_1{\mathrm{Li}}_{q1}(k+1)\\ v_q(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{q1}(k+1)\\ [P_{\mathrm{ref}}(k+2)-P_1(k+1)]-e_{d1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ -Q_1(k+1)\left]\right\}+e_{q1}(k+1)+{\mathrm{\ω}}_1{\mathrm{Li}}_{d1}(k+1)\end{array}\right.;$

Wherein: P _refk () is kT moment grid-connected active power reference value; Q _refk () is kT moment grid-connected reactive power reference qref; L is three-phase grid inductance value; ω ₁=2 π f ₁t; f ₁for controlling the frequency of setting;

Step 8: by current transformer output voltage vector v _dand v (k+1) _q(k+1) through Park inverse transformation, SVPWM modulation, current transformer power tube drive singal is exported.

When carrying out Park conversion in step 2, the angle theta=θ of synchronous rotating frame and rest frame ₁+ 2 π f ₁t, t are the moment, phase angle theta ₁for arbitrary value.

Compared with prior art, the beneficial effect that the present invention reaches is: clap according to control system actual time delay two, for reducing next impact of clapping power output and current forecasting precision and simplifying prediction and calculation, adopt the sample frequency doubling carrier frequency, do not need complicated calculations, just accurately can calculate the predicted value of next the grid-connected power clapped, grid-connected current and line voltage, improve control precision, then calculate the output of next carrier cycle three-phase convertor circuit.Without the need to phase-locked loop, f ₁with f ₀deviation on the present invention put forward control method performance do not affect, without the need to the adjustment for frequency departure, decrease the impact of phase-locked error on control performance.Control method provided by the present invention is simple, and what can realize 3-phase power converter determines frequency no phase-locked loop Direct Power PREDICTIVE CONTROL, is easy to through engineering approaches.

Accompanying drawing explanation

Fig. 1 adopts 3-phase power converter system construction drawing of the present invention.

Fig. 2 is 3-phase power converter output voltage effect sequential chart.

Fig. 3 is algorithm principle block diagram of the present invention.

Fig. 4 is given active power 20kW and reactive power 20kVAR, changes f ₁the simulation waveform obtained.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

As shown in Figure 1,3-phase power converter comprises DC power supply U _dc, six IGBT power tube, three-phase reactor L and dc-link capacitance C, six IGBT power tubes composition three phase bridge circuits, dc-link capacitance C is connected in parallel on DC power supply U _dctwo ends, three-phase reactor is series between current transformer and three phase network, and control system obtains the output of three phase bridge circuit according to the value that calculates of sampling, and obtains drive singal and drives each IGBT switch, control grid-connected power and make it reach set point by SVPWM.

As shown in Figure 3, no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm, comprises the following steps:

Step one: in Fig. 2, in (k-1) T, (k-1/2) T, kT, (k+1/2) T, (k+1) T, (k+3/2) T, (k+2) T moment, respectively to three-phase power grid voltage e _a, e _b, e _cwith three-phase grid current i _a, i _b, i _csample, T is a triangular carrier cycle of PWM, and k is integer.

Step 2: the three-phase power grid voltage obtained of step one being sampled and three-phase grid electric current through Clark conversion and Park conversion (in Fig. 1, dp conversion and Clark convert and Park conversion), obtain the three-phase power grid voltage vector e under synchronous rotating frame respectively _d, e _qwith three-phase grid current vector i _d, i _q;

Ignore line impedance, three phase network is symmetrical, and the current transformer Mathematical Modeling under three-phase static coordinate system is:

$L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_a\\ i_b\\ i_c\end{array}\right]=\left[\begin{array}{c}{v}_{\mathrm{an}}\\ v_{\mathrm{bn}}\\ v_{\mathrm{cn}}\end{array}\right]-\left[\begin{array}{c}{e}_a\\ e_b\\ e_c\end{array}\right]---\left(1\right)$

In formula, v _an, v _bn, v _cnfor the output voltage of the relative neutral point of electric network of 3-phase power converter half-bridge output a, b, c, i _a, i _b, i _cfor three-phase grid electric current.

Formula (1), through Clarke conversion, can obtain the current transformer Mathematical Modeling under static α β coordinate system:

$L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{I}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ζ})\\ I_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\π}/2+\mathrm{\ζ})\end{array}\right]=\left[\begin{array}{c}{v}_{\mathrm{\α}}\\ v_{\mathrm{\β}}\end{array}\right]-\left[\begin{array}{c}{E}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ψ})\\ E_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\π}/2+\mathrm{\ψ})\end{array}\right]---\left(2\right)$

In formula, I _{α β}and E _{α β}be respectively the peak value of grid-connected current under static α β coordinate system and line voltage, v _{α β}=[v _α, v _β] ^tfor current transformer bridge output voltage under static α β coordinate system, ω ₀=2 π f ₀for actual electric network angular frequency, ψ and ζ is respectively the phase angle of line voltage and grid-connected current.

The Park that two-phase static α β coordinate is tied to two-phase synchronous rotating frame is transformed to:

$\left[\begin{array}{c}{e}_d\\ e_q\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}{E}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ψ})\\ E_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\π}/2+\mathrm{\ψ})\end{array}\right]=\left[\begin{array}{c}{E}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ψ}-{\mathrm{\ω}}_{1}t-{\mathrm{\θ}}_1)\\ -E_{\mathrm{\α\β}}\cos ({\mathrm{\ω}}_{0}t+\mathrm{\ψ}-{\mathrm{\ω}}_{1}t-{\mathrm{\θ}}_1)\end{array}\right]---\left(3\right)$

$\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\left[\begin{array}{cc}\cos \mathrm{\θ}& \sin \mathrm{\θ}\\ -\sin \mathrm{\θ}& \cos \mathrm{\θ}\end{array}\right]\left[\begin{array}{c}{I}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ζ})\\ I_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t-\mathrm{\π}/2+\mathrm{\ζ})\end{array}\right]=\left[\begin{array}{c}{I}_{\mathrm{\α\β}}\sin ({\mathrm{\ω}}_{0}t+\mathrm{\ζ}-{\mathrm{\ω}}_{1}t-{\mathrm{\θ}}_1)\\ -I_{\mathrm{\α\β}}\cos ({\mathrm{\ω}}_{0}t+\mathrm{\ζ}-{\mathrm{\ω}}_{1}t-{\mathrm{\θ}}_1)\end{array}\right]---\left(4\right)$

In formula, i _dq=[i _d, i _q] ^tand e _dq=[e _d, e _q] ^tbe respectively the grid-connected current under synchronous rotating frame and line voltage, θ is the angle of synchronous rotating frame and two-phase rest frame.θ=θ ₁+ 2 π f ₁t, f ₁for the frequency of control system setting, phase angle theta ₁can be arbitrary value, without the need to carrying out phase lock control.

Formula (2), through Park coordinate transform, can the current transformer Mathematical Modeling under synchronous rotating frame can be expressed as:

$L\frac{d}{\mathrm{dt}}\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]=\left[\begin{array}{c}{v}_d\\ v_q\end{array}\right]-\begin{array}{c}\left[\begin{array}{c}{e}_d-{\mathrm{\ω}}_1{\mathrm{Li}}_q\\ e_q+{\mathrm{\ω}}_1{\mathrm{Li}}_d\end{array}\right]\end{array}---\left(5\right)$

In formula, v _dq=[v _d, v _q] ^tfor the three-phase bridge output voltage under synchronous rotating frame.

Step 3: according to instantaneous power theory, the instantaneous active power P and the reactive power Q that calculate 3-phase power converter output are:

$\left[\begin{array}{c}P\\ Q\end{array}\right]=\frac{3}{2}\left[\begin{array}{cc}{e}_d& e_q\\ e_q& -e_d\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]---\left(6\right)$

Formula (5) discretization is obtained:

$\left[\begin{array}{c}{i}_d(k+1)-i_d\left(k\right)\\ i_q(k+1)-i_q\left(k\right)\end{array}\right]=\frac{T}{L}(\left[\begin{array}{c}{v}_d\left(k\right)+{\mathrm{\ω}}_1{\mathrm{Li}}_q\left(k\right)\\ v_q\left(k\right)-{\mathrm{\ω}}_1{\mathrm{Li}}_d\left(k\right)\end{array}\right]-\left[\begin{array}{c}{e}_d\left(k\right)\\ e_q\left(k\right)\end{array}\right])---\left(7\right)$

By formula (6) discretization, and formula (7) is substituted into:

$\left[\begin{array}{c}P(k+1)-P\left(k\right)\\ Q(k+1)-Q\left(k\right)\end{array}\right]=\frac{3T}{2L}\left[\begin{array}{cc}{e}_d\left(k\right)& e_q\left(k\right)\\ e_q\left(k\right)& -e_d\left(k\right)\end{array}\right](\left[\begin{array}{c}{v}_d\left(k\right)+{\mathrm{\ω}}_1{\mathrm{Li}}_q\left(k\right)\\ v_q\left(k\right)-{\mathrm{\ω}}_1{\mathrm{Li}}_d\left(k\right)\end{array}\right]-\left[\begin{array}{c}{e}_d\left(k\right)\\ e_q\left(k\right)\end{array}\right])---\left(8\right)$

In the numerical control system of reality, due to links such as AD sampling, signal filtering and control algolithm calculating, from the generation sampling output voltage signal of electric current and voltage value, always there is inevitable digital delay.Current transformer output voltage effect sequential as shown in Figure 2, the kT moment samples to the grid-connected current of current transformer, DC bus-bar voltage and line voltage, and the control algorithm of kT ~ (k+1) T time section obtains (k+1) T ~ (k+2) T time section three-phase bridge and exports v _dand v (k+1) _q(k+1), the quantity of state of system reaches desired value in (k+2) T moment, and whole time of delay reaches 2T.In order to realize the accurate control to (k+2) T moment output valve, PREDICTIVE CONTROL needs to precalculate the current transformer quantity of state in (k+1) T moment.

The active power of step 4: kT to (k+1/2) T is identical with reactive power increment to the active power of (k+1) T with (k+1/2) T with reactive power increment, can according to the active-power P in (k+1/2) T moment ^mid(k) and reactive power Q ^midk (), the active-power P (k) in kT moment and reactive power Q (k), calculate (k+1) T moment active power predicted value P ₁and reactive power predicted value Q (k+1) ₁(k+1):

$\left[\begin{array}{c}{P}_1(k+1)\\ Q_1(k+1)\end{array}\right]=2\left[\begin{array}{c}{P}^{\mathrm{mid}}\left(k\right)\\ Q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}P\left(k\right)\\ Q\left(k\right)\end{array}\right]---\left(9\right)$

Step 5: the grid-connected current according to (k+1/2) T moment is with the grid-connected current in kT moment is i _d(k) and i _qk (), calculates the grid-connected current predicted value i in (k+1) T moment _d1and i (k+1) _q1(k+1):

$\left[\begin{array}{c}{i}_{d1}(k+1)\\ i_{q1}(k+1)\end{array}\right]=2\left[\begin{array}{c}{i}_d^{\mathrm{mid}}\left(k\right)\\ i_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}{i}_d\left(k\right)\\ i_q\left(k\right)\end{array}\right]---\left(10\right)$

Step 6: from formula (3), e _dand e _qbeing frequency is | f ₀-f ₁| Low Frequency Sine Signals, for the sample frequency up to a few kHz, tens kHz, adjacent amount can be considered as linear relation, therefore, can be according to the line voltage in (k+1/2) T moment with the line voltage in kT moment is e _d(k) and e _qk (), calculates the line voltage predicted value e in (k+1) T moment _d1and e (k+1) _q1(k+1):

$\left[\begin{array}{c}{e}_{d1}(k+1)\\ e_{q1}(k+1)\end{array}\right]=2\left[\begin{array}{c}{e}_d^{\mathrm{mid}}\left(k\right)\\ e_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}{e}_d\left(k\right)\\ e_q\left(k\right)\end{array}\right]---\left(11\right)$

Step 7: by formula (6), formula (7) and formula (8), calculates (k+1) T to (k+2) T moment current transformer output voltage vector v _dand v (k+1) _q(k+1):

$\left\{\begin{array}{c}{v}_d(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{d1}(k+1)\\ [P_{\mathrm{ref}}(k+2)-P_1(k+1)]+e_{q1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ -Q_1(k+1)\left]\right\}+e_{d1}(k+1)-{\mathrm{\ω}}_1{\mathrm{Li}}_{q1}(k+1)\\ v_q(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{q1}(k+1)\\ [P_{\mathrm{ref}}(k+2)-P_1(k+1)]-e_{d1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ -Q_1(k+1)\left]\right\}+e_{q1}(k+1)+{\mathrm{\ω}}_1{\mathrm{Li}}_{d1}(k+1)\end{array}\right.;$

Wherein: P _refk () is kT moment grid-connected active power reference value; Q _refk () is kT moment grid-connected reactive power reference qref; L is three-phase grid inductance value; ω ₁=2 π f ₁t; f ₁for controlling the frequency of setting;

Step 8: by current transformer output voltage vector v _dand v (k+1) _q(k+1) through Park inverse transformation, SVPWM modulation, current transformer power tube drive singal is exported.

Matlab/Simulink is utilized to build 3-phase power converter circuit, drive circuit and Control System Imitation model, simulation parameter: U _dc=800V, L=0.6mH, 380Vac/50Hz three phase network, carrier frequency is 12kHz.Given meritorious and reactive power one timing, changes the frequency f of control system setting in simulation run process ₁the waveform obtained as shown in Figure 4.Active power given in Fig. 4 is 20kW, and reactive power is 20kVAR, as can be seen from the figure, and f ₁change procedure grid-connected current steady, this illustrates that the present invention carries setpoint frequency f in control method ₁with actual electric network frequency f ₀deviation do not affect control performance.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (2)

1. a no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm, is characterized in that, comprise the following steps:

Step one: in (k-1) T, (k-1/2) T, kT, (k+1/2) T, (k+1) T, (k+3/2) T, (k+2) T moment, respectively to three-phase power grid voltage e _a, e _b, e _cwith three-phase grid current i _a, i _b, i _csample, T is a triangular carrier cycle of PWM, and k is integer;

Step 2: the three-phase power grid voltage obtained of step one being sampled and three-phase grid electric current, respectively through Clark conversion and Park conversion, obtain the three-phase power grid voltage vector e under synchronous rotating frame _d, e _qwith three-phase grid current vector i _d, i _q;

Step 3: according to instantaneous power theory, calculates instantaneous active power P and reactive power Q:

$\left[\begin{array}{c}P\\ Q\end{array}\right]=\frac{3}{2}\left[\begin{array}{cc}{e}_d& e_q\\ e_q& {-e}_d\end{array}\right]\left[\begin{array}{c}{i}_d\\ i_q\end{array}\right]$

Step 4: according to the active-power P in (k+1/2) T moment ^mid(k) and reactive power Q ^midk (), the active-power P (k) in kT moment and reactive power Q (k), calculate (k+1) T moment active power predicted value P ₁and reactive power predicted value Q (k+1) ₁(k+1):

$\left[\begin{array}{c}{P}_1(k+1)\\ Q_1(k+1)\end{array}\right]=2\left[\begin{array}{c}{P}^{\mathrm{mid}}\left(k\right)\\ Q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}P\left(k\right)\\ Q\left(k\right)\end{array}\right]$

Step 5: according to the grid-connected current in (k+1/2) T moment with the grid-connected current i in kT moment _d(k) and i _qk (), calculates the grid-connected current predicted value i in (k+1) T moment _d1and i (k+1) _q1(k+1):

$\left[\begin{array}{c}{P}_1(k+1)\\ Q_1(k+1)\end{array}\right]=2\left[\begin{array}{c}{i}_d^{\mathrm{mid}}\left(k\right)\\ i_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\left[\begin{array}{c}{i}_d\left(k\right)\\ i_q\left(k\right)\end{array}\right]$

Step 6: according to the line voltage in (k+1/2) T moment with the line voltage e in kT moment _d(k) and e _qk (), calculates the line voltage predicted value e in (k+1) T moment _d1and e (k+1) _q1(k+1):

$\left[\begin{array}{c}{e}_{d1}(k+1)\\ e_{q1}(k+1)\end{array}\right]=2\begin{array}{c}\left[\begin{array}{c}{e}_d^{\mathrm{mid}}\left(k\right)\\ e_q^{\mathrm{mid}}\left(k\right)\end{array}\right]-\end{array}\left[\begin{array}{c}{e}_d\left(k\right)\\ e_q\left(k\right)\end{array}\right]$

Step 7: calculate (k+1) T to (k+2) T moment current transformer output voltage vector v _dand v (k+1) _q(k+1):

$\left\{\begin{array}{c}{v}_d(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{d1}(k+1)\\ P_{\mathrm{ref}}(k+2)-P_1(k+1)]+e_{q1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ {-Q}_1(k+1)\left]\right\}+e_{d1}(k+1)-{\mathrm{\ω}}_1{\mathrm{Li}}_{q1}(k+1)\\ v_q(k+1)=\frac{2L}{[e_{d1}^2(k+1)+e_{q1}^2(k+1)]3T}\{e_{q1}(k+1)\\ P_{\mathrm{ref}}(k+2)-P_1(k+1)]-e_{d1}(k+1)[Q_{\mathrm{ref}}(k+2)\\ {-Q}_1(k+1)\left]\right\}+e_{q1}(k+1)+{\mathrm{\ω}}_1{\mathrm{Li}}_{d1}(k+1)\end{array}\right.;$

Wherein: P _refk () is kT moment grid-connected active power reference value; Q _refk () is kT moment grid-connected reactive power reference qref; L is three-phase grid inductance value; ω ₁=2 π f ₁t; f ₁for controlling the frequency of setting;

Step 8: by current transformer output voltage vector v _dand v (k+1) _q(k+1) through Park inverse transformation, SVPWM modulation, current transformer power tube switching drive signal is exported.

2. no phase-locked loop 3-phase power converter Direct Power forecast Control Algorithm according to claim 1, is characterized in that, when carrying out Park conversion in step 2, and the angle theta=θ of synchronous rotating frame and rest frame ₁+ 2 π f ₁t, t are the moment, phase angle theta ₁for arbitrary value.