CN106410818A - Real-time power factor correction circuit with fractional-order capacitor and control method thereof - Google Patents

Abstract

The invention discloses a real-time power factor correction circuit with a fractional-order capacitor and a control method thereof. The real-time power factor correction circuit is composed of an input alternating-current power supply, a fractional-order capacitor with a controllable order and capacitance value, a load, a voltage sampler, a current sampler, and a controller. The voltage sampler carries out input voltage sampling; the current sampler carries out load current sampling; the controller outputs signals for controlling the order number and capacitance value of the fractional-order capacitor based on voltage and current signals collected by the voltage sampler and the current sampler respectively, thereby adjusting the order number and capacitance value of the fractional-order capacitor and enabling the power factor of an input power side to reach 1. Therefore, real-time correction of a unit power factor can be realized effectively. According to the invention, the order number and capacitance value of the fractional-order capacitor are adjusted by real-time detection of the input voltage and the load current, thereby realizing real-time correction of the unit power factor. Moreover, the power factor correction function is realized only by one element, so that the structure of the circuit is simple.

Description

Realtime power factor correcting circuit and its control method using fractional order electric capacity

Technical field

The present invention relates to the technical field of PFC, refer in particular to a kind of realtime power of employing fractional order electric capacity Factor correcting circuit and its control method.

Background technology

Because most of electrical equipments are resistance inductive load, need from power system absorbing reactive power, power factor is not Height, leads to the capacity of power supply unit can not be fully used, causes power system electric energy loss increase and power supply quality simultaneously Reduce.In order to improve the power factor of whole system, generally add circuit of power factor correction in systems.Typical power because Number bearing calibration includes PPFC and APFC, and PPFC is according to inductance capacitance The complementary characteristic of reactive power, improves the power factor of circuit, structure letter by the method in inductive load end shunt capacitance Single.But because capacitor's capacity is fixed numbers it is impossible to consecutive variations, therefore when load changes it is impossible to realize unit power Factor correcting.Although APFC device can accomplish that realtime power factor corrects, the structure of these devices is multiple Miscellaneous, and relatively costly.

In recent years, this new device of fractional order electric capacity successfully produces.The present invention utilize fractional order electric capacity exponent number and The all adjustable characteristic of capacitance, proposes the realtime power factor correcting circuit using fractional order electric capacity.With existing PFC Circuit is compared, and the present invention can not only realize the real time correction of power factor, and has only used a controlled fractional order electric capacity Element, structure is simple, controls flexibly, has fabulous application prospect.

Content of the invention

It is an object of the invention to overcoming shortcoming and the deficiency of prior art, provide a kind of simple and reasonable for structure, reliable Using realtime power factor correcting circuit and its control method of fractional order electric capacity, can effectively realize the real-time of unity power factor Correction.

For achieving the above object, technical scheme provided by the present invention is as follows：

A kind of realtime power factor correcting circuit of employing fractional order electric capacity, described realtime power factor correcting circuit includes Alternating current power supply, exponent number and the controlled fractional order electric capacity of capacitance, load, voltage sample device, current sampler and controller；Described friendship The A end of stream power supply is connected with one end of fractional order electric capacity, and the B end of this alternating current power supply is connected with the other end of fractional order electric capacity, institute The A end of one end and alternating current power supply of stating load is connected, and the other end of this load is connected with one end of current sampler, and this electric current is adopted The other end of sample device is connected with the B end of alternating current power supply, and one end of described voltage sample device is connected with the A end of alternating current power supply, this electricity The other end of pressure sampler is connected with the B end of alternating current power supply, and the described output of voltage sample device and the output of current sampler divide It is not connected with controller, the output of this controller is connected with fractional order electric capacity.

The admittance of described realtime power factor correcting circuit is as follows：

In formula, R_LFor the resistance of resistance, L is the inductance value of inductance, the angular frequency that ω works for circuit, C_αFor fractional order electric capacity Capacitance, α be fractional order electric capacity exponent number；Load is by inductance L and resistance R_LConstitute；

In circuit with the ratio cos φ of active-power P and apparent energy S come the power-factor angle of indication circuit, φ is The impedance angle of system or admittance angle, are obtained the power factor of this circuit by (1) formula：

Knowable to (2) formula, unity power factor λ=1 to be realized, the B in equivalent admittance need to be made_eq=0, then have：

Known load impedance is：

The phase contrast of note load voltage and electric current is θ, then have：

ω L=| Z | sin θ (5)

(4) formula and (5) formula are brought in (3) formula, the capacitance obtaining fractional order electric capacity further is：

By phase difference θ and the load impedance Z of real-time detection load voltage (i.e. input voltage) and electric current it becomes possible to obtain Capacitance size to the correspondence realized required for unity power factor correction a certain exponent number fractional order electric capacity；

When the exponent number of fractional order electric capacity is more than 1, the voltage vector of fractional order electric capacity and the angle of current vector are π α/2, More than 90 degree, now fractional order electric capacity can not only provide reactive power to load, and is also provided with work(power.

The exponent number range of accommodation of described fractional order electric capacity is 0～2.

The capacitance of described fractional order electric capacity can continuously adjust.

The control method of the realtime power factor correcting circuit of the present invention above-mentioned employing fractional order electric capacity is as follows：

First, voltage sample device and current sampler are sampled by controller input voltage and load current be transformed into The synchronous square-wave signal of frequency, obtains the phase contrast of corresponding input voltage and load current, simultaneously according to input voltage and The size of load current, obtains corresponding load impedance；Obtain required fractional order electric capacity then according to phase contrast and load impedance Exponent number, the size of capacitance；When supply voltage or load change when, controller according to the voltage and current signal sampling, Adjust fractional order electric capacity size so that the power factor of input power side reaches 1, to realize the real-time school of unity power factor Just.

The present invention compared with prior art, has the advantage that and beneficial effect：

1st, pass through real-time detection input voltage and load current, the capacitance of adjustment fractional order electric capacity and exponent number, realize unit Power factor real time correction.

2nd, the exponent number of fractional order electric capacity and capacitance continuously adjustabe.

3rd, when the exponent number of fractional order electric capacity is more than 1, fractional order electric capacity not only can compensating power, but also provide Active power.

4th, only realize power factor emendation function with an element, structure is simple.

Brief description

Fig. 1 is the realtime power factor correcting circuit figure of the present invention.

Fig. 2 a is the input AC side voltage of realtime power factor correcting circuit of the present invention, input AC side electric current, point One of number rank capacitance current, load current vector diagram.

Fig. 2 b is the input AC side voltage of realtime power factor correcting circuit of the present invention, input AC side electric current, point Number rank capacitance currents, the two of load current vector diagram.

Fig. 3 is the realtime power factor correcting circuit analogous diagram of the present invention.

Fig. 4 adopts the realtime power factor correcting circuit input voltage of fractional order electric capacity of 1.3 ranks, input electricity for the present invention Stream and fractional order capacitance current analogous diagram.

Fig. 5 adopts the realtime power factor correcting circuit input voltage of fractional order electric capacity of 1.5 ranks, input electricity for the present invention Stream and fractional order capacitance current analogous diagram.

Specific embodiment

With reference to specific embodiment, the invention will be further described.

As shown in figure 1, the realtime power factor correcting circuit of the employing fractional order electric capacity described in the present embodiment, including exchange Power supply 1, exponent number and the controlled fractional order electric capacity 2 of capacitance, load 3, voltage sample device 4, current sampler 5 and controller 6.Exchange The A end of power supply 1 is connected with one end of fractional order electric capacity 2, and the B end of alternating current power supply 1 is connected with the other end of fractional order electric capacity 2, bears One end of load 3 is connected with the A end of alternating current power supply 1, and the other end of load 3 is connected with one end of current sampler 5, current sampler 5 other end is connected with the B end of alternating current power supply 1, and one end of voltage sample device 4 is connected with the A end of alternating current power supply 1, voltage sample The other end of device is connected with the B end of alternating current power supply 1, the output of the output of voltage sample device 4 and current sampler 5 respectively with control Device 6 is connected, and the output of controller 6 is connected with fractional order electric capacity 2.

The control method of the present embodiment above-mentioned realtime power factor correcting circuit is：First, controller 6 is by voltage sample device 4 and the input voltage that samples of current sampler 5 and load current be transformed into the synchronous square-wave signal of same frequency, obtain corresponding Input voltage and load current phase contrast, the size according to input voltage and load current, is loaded accordingly simultaneously Impedance；Obtain the exponent number of required fractional order electric capacity 2, the size of capacitance then according to phase contrast and load impedance；Work as supply voltage Or load is when changing, controller 6, according to the voltage and current signal sampling, adjusts the size of fractional order electric capacity 2 so that defeated The power factor entering mains side reaches 1, thus realizing the real time correction of unity power factor.

Resistance inductive load in Fig. 1 circuit is by inductance L and resistance R_LConstitute, C_αFor fractional order electric capacity in parallel.Now circuit Admittance：

In formula, R_LFor the resistance of resistance, L is the inductance value of inductance, the angular frequency that ω works for circuit, C_αFor fractional order electric capacity Capacitance, α be fractional order electric capacity exponent number.

In circuit generally with the ratio cos φ of active-power P and apparent energy S come the power-factor angle of indication circuit, φ can be impedance angle or the admittance angle of system, by the power factor of (1) this circuit of Shi Ke get：

Knowable to (2) formula, unity power factor λ=1 to be realized, the B in equivalent admittance need to be made_eq=0, then have：

Known load impedance is：

The phase contrast of note load voltage and electric current is θ, then have：

ω L=| Z | sin θ (5)

(4) formula and (5) formula are brought in (3) formula, the capacitance obtaining fractional order electric capacity further is：

By phase difference θ and the load impedance Z of real-time detection load voltage (i.e. input voltage) and electric current it is possible to obtain Capacitance size to the correspondence realized required for unity power factor correction a certain exponent number fractional order electric capacity.The rank of fractional order electric capacity Number range of accommodation is 0～2, and capacitance can continuously adjust.

Before correction, the input voltage V of fractional order Capacitance Power factor correcting circuit_s, input current I_s, fractional order electric capacity electricity Stream I_cWith load current I_LAs shown in Figure 2 a it is clear that circuit power factor is not up to 1.If the exponent number of fractional order electric capacity is constant, increase The capacitance of fractional order electric capacity, thus increase the electric current of fractional order electric capacity.Now fractional order Capacitance Power factor correcting circuit is defeated Enter voltage V_s, input current I_s, fractional order capacitance current I_cWith load current I_LAs shown in Figure 2 b it is seen that the power factor of circuit Reach 1.When the exponent number of fractional order electric capacity is more than 1, the voltage vector of fractional order electric capacity and the angle of current vector are π α/2, greatly In 90 degree, now fractional order electric capacity not only can provide reactive power to load, and additionally provides active power.

Fig. 3 is the PSIM analogue system figure of the present embodiment above-mentioned realtime power factor correcting circuit.Wherein load switching mould Block is used for embodying the power factor real time correction effect of invention circuit；Voltage, current signal modular converter are by voltage signal and electricity Stream signal is converted to square-wave signal, is easy to phase-detection；Impedance detection module is used for the size of computing impedance Z；Fractional order electricity Hold and realized with a controlled current source, output current meets：Wherein C_αFor the capacitance of fractional order electric capacity, α is The exponent number of fractional order electric capacity, α ∈ (0,2) and α ≠ 1.

According to simulation system parameters, (6) formula is changed into：

K in formula_sFor voltage sample coefficient, K_iFor current sample coefficient.K₁、K₂And K₄For proportional control factor, for the ease of Measurement impedance Z, makes K_sK₁=1, K_iK₂=1.K₄=1/ (sin (0.5 π α) ω^α).

Choose v_inThis circuit, corresponding voltage sample COEFFICIENT K to be verified in AC-input voltage source for 100V/50Hz_s= 0.01, then K₁=100；Current sample COEFFICIENT K_i=0.1, then K₂=10；R before load switching_L=30 Ω, L=14mH, load is cut Change rear R_L=25 Ω, L=14mH；Take exponent number α=1.3, then K₄=6.37 × 10^-4, emulate the input voltage v obtaining_inAnd input Electric current i_inAnd fractional order capacitance current i_cαAs shown in figure 4, as seen from the figure when load switching, fractional order capacitance current obtains To real-time regulation, input voltage and input current still keep homophase, and the power factor of circuit is still 1.If by exponent number be changed to α= 1.5, then K₄=2.54 × 10^-4, emulate the input voltage v obtaining_inWith input current i_inAnd fractional order capacitance current i_cαAs figure Shown in 5, as seen from the figure when load switching, fractional order capacitance current obtains real-time regulation, and input voltage and input current Still keep homophase, the power factor of circuit is still 1.The simulation results show feasibility of circuit of the present invention.

Embodiment described above is only the preferred embodiments of the invention, not limits the practical range of the present invention with this, therefore The change that all shapes according to the present invention, principle are made, all should cover within the scope of the present invention.

Claims (5)

1. a kind of realtime power factor correcting circuit of employing fractional order electric capacity it is characterised in that：Described realtime power factor school Positive circuit includes alternating current power supply, exponent number and the controlled fractional order electric capacity of capacitance, load, voltage sample device, current sampler and control Device processed；The A end of described alternating current power supply is connected with one end of fractional order electric capacity, and the B end of this alternating current power supply is another with fractional order electric capacity One end is connected, and one end of described load is connected with the A end of alternating current power supply, one end phase of the other end of this load and current sampler Even, the other end of this current sampler is connected with the B end of alternating current power supply, one end of described voltage sample device and the A of alternating current power supply End is connected, and the other end of this voltage sample device is connected with the B end of alternating current power supply, the output of described voltage sample device and current sample The output of device is connected with controller respectively, and the output of this controller is connected with fractional order electric capacity.

2. a kind of employing fractional order electric capacity according to claim 1 realtime power factor correcting circuit it is characterised in that The admittance of described realtime power factor correcting circuit is as follows：

$\begin{array}{c}{Y}_{eq}\left(j\mathrm{\ω}\right)=(\frac{R_L}{{R_L}^2+{\left(\mathrm{\ω}L\right)}^2}+{\mathrm{\ω}}^{\mathrm{\α}}{C}_{\mathrm{\α}}\cos \frac{\mathrm{\α}\mathrm{\π}}{2})+j({\mathrm{\ω}}^{\mathrm{\α}}{C}_{\mathrm{\α}}\sin \frac{\mathrm{\α}\mathrm{\π}}{2}-\frac{\mathrm{\ω}L}{{R_L}^2+{\left(\mathrm{\ω}L\right)}^2})\\ =G_{eq}+{\mathrm{jB}}_{eq}\end{array}---\left(1\right)$

In formula, R_LFor the resistance of resistance, L is the inductance value of inductance, the angular frequency that ω works for circuit, C_αAppearance for fractional order electric capacity Value, α is the exponent number of fractional order electric capacity；Load is by inductance L and resistance R_LConstitute；

In circuit with the ratio cos φ of active-power P and apparent energy S come the power-factor angle of indication circuit, φ is system Impedance angle or admittance angle, obtained the power factor of this circuit by (1) formula：

$\mathrm{\λ}={\mathrm{cos\φ}}_Y=\frac{G_{eq}}{\sqrt{{G_{eq}}^2+{B_{eq}}^2}}---\left(2\right)$

Knowable to (2) formula, unity power factor λ=1 to be realized, the B in equivalent admittance need to be made_eq=0, then have：

$C_{\mathrm{\α}}=\frac{\mathrm{\ω}L}{({R_L}^2+{\mathrm{\ω}}^2{L}^2)\sin \left(0.5\mathrm{\π}\mathrm{\α}\right){\mathrm{\ω}}^{\mathrm{\α}}}---\left(3\right)$

Known load impedance is：

$\left|Z\right|=\sqrt{{R_L}^2+{\mathrm{\ω}}^2{L}^2}---\left(4\right)$

The phase contrast of note load voltage and electric current is θ, then have：

ω L=| Z | sin θ (5)

(4) formula and (5) formula are brought in (3) formula, the capacitance obtaining fractional order electric capacity further is：

$C_{\mathrm{\α}}=\frac{sin\mathrm{\θ}}{\left|Z\right|sin\left(0.5\mathrm{\π}\mathrm{\α}\right){\mathrm{\ω}}^{\mathrm{\α}}}---\left(6\right)$

It is phase difference θ and the load impedance Z of input voltage and electric current by real-time detection load voltage it becomes possible to accomplished The capacitance size of a certain exponent number fractional order electric capacity of the correspondence required for unity power factor correction；

When the exponent number of fractional order electric capacity is more than 1, the voltage vector of fractional order electric capacity and the angle of current vector are π α/2, are more than 90 degree, now fractional order electric capacity can not only provide reactive power to load, and be also provided with work(power.

3. the realtime power factor correcting circuit of a kind of employing fractional order electric capacity according to claim 1 and 2, its feature exists In：The exponent number range of accommodation of described fractional order electric capacity is 0～2.

4. the realtime power factor correcting circuit of a kind of employing fractional order electric capacity according to claim 1 and 2, its feature exists In：The capacitance of described fractional order electric capacity can continuously adjust.

5. described in a kind of claim 1, adopt the control method of the realtime power factor correcting circuit of fractional order electric capacity, its feature It is：First, the input voltage that voltage sample device and current sampler are sampled by controller and load current are transformed into frequency The synchronous square-wave signal of rate, obtains the phase contrast of corresponding input voltage and load current, simultaneously according to input voltage and negative Current-carrying size, obtains corresponding load impedance；Obtain required fractional order electric capacity then according to phase contrast and load impedance Exponent number, the size of capacitance；When supply voltage or load change, controller, according to the voltage and current signal sampling, is adjusted Section fractional order electric capacity size so that the power factor of input power side reaches 1, to realize the real-time school of unity power factor Just.