CN103248106A - Novel electric automobile battery charger based on single-cycle control strategy - Google Patents

Abstract

The invention discloses a novel electric automobile battery charger based on a single-cycle control strategy, which comprises a three-phase power source connected with an LCL filter, wherein the LCL filter is connected with an input end of a main circuit of a three-phase PWM (Pulse-width Modulation) power converter; a DC output end of the three-phase PWM power converter is connected in parallel with a support capacitor, while a first load and a discharge loop are connected in parallel to the DC output end of the three-phase PWM power converter through a selective switch; and a control system of the three-phase PWM power converter acquires induction current signals of an LCL filter, voltage signals of the connection point of the input end of the main circuit of the three-phase PWM power converter with the LCL filter and DC voltage signals of the support capacitor C and controls the three-phase PWM power converter to operationally output corresponding pulse switch signals. The electric automobile battery charger has the advantages of simplicity in controlling, high response speed, low manufacturing cost, and capability of realizing seamless switch between rectification and inversion.

Description

Novel electric vehicle charger based on the monocycle control strategy

Technical field

The present invention relates to a kind of novel electric vehicle charger based on the monocycle control strategy.

Background technology

The charging electric vehicle machine is nonlinear-load, produces harmonic current during charging, causes voltage distortion.At present, elimination and inhibition current harmonics have become a focus of charging electric vehicle machine.

1. the three-phase PWM power inverter is used widely in the charging electric vehicle machine owing to have advantages such as current on line side sine, power factor height, energy two-way flow.Control strategy to the three-phase PWM power inverter has the ring of stagnating control, PREDICTIVE CONTROL, vector control, direct Power Control etc., but these control methods all need to adopt dq coordinate transform and SPWM or SVPWM modulation, and system is comparatively complicated, the production cost height.

Monocycle control circuit compact conformation, used element is few and response speed is fast, but the limitation of system's fluctuation of service occurs under underloading or anti-phase inverter mode, being applied to has a lot of difficulties on the charging electric vehicle machine.

Summary of the invention

Purpose of the present invention is exactly in order to address the above problem, traditional monocycle control method is improved, a kind of novel electric vehicle charger based on the monocycle control strategy is provided, has that control is simple, response speed is fast, production cost is low, can realize the advantage by the seamless switching that is rectified to inversion.

To achieve these goals, the present invention adopts following technical scheme:

A kind of novel electric vehicle charger based on the monocycle control strategy, comprise three phase mains, three phase mains is connected with the LCL filter, and the LCL filter is connected with the input of three-phase PWM power inverter main circuit, the dc output end of the three-phase PWM power inverter electric capacity that supports in parallel; Load simultaneously and discharge loop are in parallel with the dc output end of three-phase PWM power inverter by selector switch; The control system of three-phase PWM power inverter is gathered the current signal i of LCL filter inductance _Rn, LCL filter and three-phase PWM power inverter main circuit input the voltage signal v of tie point _RnAnd the d. c. voltage signal U that supports the capacitor C two ends _Dc, corresponding pulse switch signal is exported in the work of control three-phase PWM power inverter.

Described three-phase PWM power inverter major loop adopts the three-phase full-controlled bridge of being made up of a plurality of switching devices.

Described discharge loop comprises the series circuit of second load and direct current adjustable voltage.

The control system of described three-phase PWM power inverter comprises: a plurality of rest-set flip-flops, each rest-set flip-flop

End, Q end are all distinguished corresponding with the pulse switch signal of the upper and lower brachium pontis switching device of a brachium pontis; The R end of each rest-set flip-flop is connected with the output of corresponding comparator respectively, and its S end all is connected with the clock signal module; The forward end input signal of each comparator is by detecting current i _Rn, detect voltage v _RnWith 1/R _fModule, R _sModule interconnects and obtains, and the negative end input signal is sawtooth signal; Described sawtooth signal is by error signal V _mWith V _mThe superimposed generation of signal through the integrator generation; Described error signal V _mBe reference voltage and dc voltage U _DcDifference through the output signal of pi regulator.

Described sawtooth waveforms carrier signal is V _m(1-t/ τ), t are time signal, and τ is time constant of integrator, gets τ=0.5T _s, T _sBe switch periods.

Described detection current i _Rn, detect voltage v _RnWith 1/R _fModule, R _sThe interconnected relationship of module is: voltage signal v _RnMultiply by gain 1/R _f, obtain virtual current signal i _NfVirtual current i _NfMultiply by gain R _sObtain R _si _NfCurrent signal multiply by gain R _sObtain R _si _RnR _si _NfAnd R _si _RnThe superimposed comparison signal R that obtains _si _NO, i _NO=i _Nf+ i _Rn

Described gain 1/R _fIn R _fBe the adjustable electric resistance, described gain 1/R _fIn R _sBe three phase mains equivalent internal resistance value.

Beneficial effect of the present invention:

1. the charging electric vehicle machine adopts the three-phase PWM power inverter, have advantages such as current on line side sine, power factor height, energy two-way flow, can effectively suppress current harmonics, both can realize being under the normal mode charging electric vehicle, can when the network load peak, the electric energy feedback grid have been realized peak load shifting again.

2. adopt improved monocycle control strategy, have the dual-use function of modulation and control, simple in structure, cost is low, and neither need to divide 60 ° of control intervals and also need not to increase logic control circuits such as interval selection circuit, control method realizes more easy.

3. in three-phase PWM power inverter monocycle control system, introduce electric voltage feed forward control, and by regulating adjustable resistance R _fProduce virtual current, can realize being switched to the smooth and seamless of inverter mode by the rectification pattern.

Description of drawings

Fig. 1 is three-phase PWM power inverter main circuit topological structure;

Fig. 2 is the control system block diagram of improved three-phase PWM power inverter;

The switching signal that Fig. 3 compares with sawtooth waveforms and produces for virtual current and the stack of detection electric current;

The Bode diagram that Fig. 4 draws for the LCL filter parameter;

Fig. 5 is three-phase PWM power inverter A phase voltage, electric current and dc voltage;

A phase voltage, electric current and dc voltage when Fig. 6 uprushes 50 Ω for load by 25 Ω;

Fig. 7 be the three-phase PWM power inverter by the rectification mode transition to inverter mode.

Wherein, 1. three phase mains; 2.LCL filter; 3. three-phase full-controlled bridge; 4. support electric capacity; 5. selector switch; 6. first load; 7. second load; 8. direct current adjustable voltage; 9.PI adjuster; 10. integrator; 11. comparator; 12.RS trigger; 13. clock signal module; 14.1/R _fModule; 15.R _sModule.

Embodiment

The invention will be further described below in conjunction with accompanying drawing and embodiment.

As shown in Figure 1, a kind of novel electric vehicle charger based on the monocycle control strategy, comprise three phase mains 1, three phase mains 1 is connected with LCL filter 2, LCL filter 2 is connected with the input of three-phase PWM power inverter main circuit, the dc output end of the three-phase PWM power inverter electric capacity 4 that supports in parallel; First load 6 simultaneously and discharge loop are in parallel with the dc output end of three-phase PWM power inverter by selector switch 5; The control system of three-phase PWM power inverter is gathered the current signal i of LCL filter 2 inductance _Rn, LCL filter 2 and the tie point of three-phase PWM power inverter main circuit input voltage signal v _RnAnd the d. c. voltage signal U that supports electric capacity 4 two ends _Dc, corresponding pulse switch signal is exported in the work of control three-phase PWM power inverter.

Described three-phase PWM power inverter major loop adopts the three-phase full-controlled bridge of being made up of a plurality of switching devices 3.

Described discharge loop comprises the series circuit of second load 7 and direct current adjustable voltage 8.

First load 6 inserted main circuits when selector switch 5 was connected with A in the switching circuit, and the three-phase PWM power inverter is operated in the rectification pattern, and charger is given charging electric vehicle; When selector switch 5 pointed to B by A, the series circuit of second load 7 and direct current adjustable voltage 8 inserted main circuit, and the three-phase PWM power inverter to inverter mode, with electric energy feedback grid is realized peak load shifting when being implemented in the network load peak by the rectification mode transition.

Described LCL filter three is symmetrical, comprises net side inductance L _s, rectification side inductance L _r, inductance side dead resistance R _r, filter capacitor C _f, capacitive side dead resistance R _cEach phase inductance L _rWith resistance R _rThe series connection, this series circuit one end is connected with three-phase full-controlled bridge 3 brachium pontis mid points, the other end respectively with inductance L _s, capacitor C _fWith resistance R _cSeries circuit connect; Inductance L _sThe other end and three phase mains 1 internal resistance R _sConnect; Capacitor C _fWith resistance R _cThe other end of series circuit and the capacitor C of other two-phases _fWith inductance R _cSeries circuit connect.

As shown in Figure 2, the control system of described three-phase PWM power inverter comprises: a plurality of rest-set flip-flops 12, each rest-set flip-flop 12

The pulse switch signal of the upper and lower brachium pontis switching device of end, the corresponding phase of Q end output; The R end of each rest-set flip-flop 12 is connected with the output of corresponding comparator 11 respectively, and its S end all is connected with clock signal module 13; The forward end input signal of comparator 11 is by detecting current i _Rn, detect voltage v _RnWith 1/R _fModule 14, R _sModule 15 interconnects and obtains, and the negative end input signal is sawtooth signal; Described sawtooth signal is by error signal V _mWith V _mThe superimposed generation of signal through integrator 10 generations; Described error signal V _mBe reference voltage and dc voltage U _DcDifference through the output signal of pi regulator 9.

Described sawtooth waveforms carrier signal is V _m(1-t/ τ), t are time signal, and τ is time constant of integrator, gets τ=0.5T _s, T _sBe switch periods.

Described detection current i _Rn, detect voltage v _RnWith 1/R _fModule 14, R _sThe interconnected relationship of module 15 is: voltage signal v _RnMultiply by gain 1/R _f, obtain virtual current signal i _NfVirtual current i _NfMultiply by gain R _sObtain R _si _NfCurrent signal multiply by gain R _sObtain R _si _RnR _si _NfAnd R _si _RnThe superimposed comparison signal R that obtains _si _NO, i _NO=i _Nf+ i _Rn

Described gain 1/R _fIn R _fBe the adjustable electric resistance, described gain R _sIn R _sBe three phase mains equivalent internal resistance value.

As shown in Figure 3, virtual current with detect compare with the sawtooth waveforms switching signal of generation of electric current sum and be:

$R_s{i}_{\mathrm{nO}}=R_s(i_{\mathrm{rn}}+i_{\mathrm{nf}})=R_s(i_{\mathrm{rn}}+\frac{v_{\mathrm{rn}}}{R_f})(n=A,B,C)---\left(1\right)$

In the formula, R _sBe three phase mains equivalent internal resistance, R _fBe adjustable resistance.

Also can be obtained by (1) formula: i _NO=i _Rn+ i _Nf

In addition,

$\frac{I_{\mathrm{PA}}-I_{\mathrm{PB}}}{t_2}=\frac{I_{\mathrm{PB}}-I_{\mathrm{<figure-callout\; id="3"\; label="PC\; t"\; filenames="HDA00003166074200011.png"\; state="\{\{state\}\}">PC</figure-callout>}}}{t_{}}=K_3---\left(2\right)$

In the formula, I _PABe A phase maximum phase current, I _PBBe B phase maximum phase current, I _PCBe C phase maximum phase current, t ₂For A is conducted the time, t ₃For C is conducted the time, K ₃Be the carrier signal slope.

Then the variable quantity of A phase current is in the one-period:

${\mathrm{\&Delta;i}}_A=\frac{v_A}{L_s}{T}_s-\frac{v_A}{{3L}_s}({2t}_2+t_3)---\left(3\right)$

In the formula, v _ABe A phase phase voltage, T _sBe switch periods, L _sNet side inductance for the LCL filter.

Because switching frequency is far longer than supply frequency, simultaneous formula (1)～(3) can obtain:

$\frac{R_s{U}_{\mathrm{dc}}}{{2V}_m}{i}_A+L_s\frac{{\mathrm{di}}_A}{\mathrm{dt}}=v_A(1-\frac{R_s{U}_{\mathrm{dc}}}{{2R}_f{V}_m})---\left(4\right)$

In the formula, i _ABe A phase phase current, U _DcBe the both end voltage of DC side support electric capacity 4, V _mError signal for pi regulator 9 outputs.

Its frequency-domain model is:

$\stackrel{\&OverBar;}{i_A}=\frac{\stackrel{\&OverBar;}{v_A}(1-\frac{R_s{U}_{\mathrm{dc}}}{2R_f{V}_m})}{\frac{R_s{U}_{\mathrm{dc}}}{2V_m}+{\mathrm{j\&omega;L}}_s}---\left(5\right)$

In the formula,

Be A phase phase current effective value, Be A phase phase voltage effective value,

Be each phase phase current effective value.

Obtain the input current of Three-Phase PWM Rectifier:

$\stackrel{\&OverBar;}{i_n}=\frac{\stackrel{\&OverBar;}{v_n}(1-\frac{R_s{U}_{\mathrm{dc}}}{{2R}_f{V}_m})}{\frac{R_s{U}_{\mathrm{dc}}}{{2V}_m}+{\mathrm{j\&omega;L}}_s}(n=A,B,C)---\left(6\right)$

In the formula,

Be each phase phase voltage effective value,

Be each phase phase current effective value.

By formula (6) as can be seen, when

The time, power inverter operates in rectification state, when The time, power inverter operates in inverter mode, both can realize being under the normal mode charging electric vehicle, can when the network load peak electric energy feedback grid be realized peak load shifting again.

1.LCL filter design

Simple L filtering possibly can't be satisfied the electrical network requirement, and LCL filtering obtains extensive concern owing to have good filtering effect.Main circuit adopts LCL filter 2, ignores dead resistance R _sAnd R _r, its input and output transfer function is:

$\frac{I_r\left(s\right)}{V\left(s\right)}=\frac{L_r{L}_s{C}_f{s}^2+L_r{R}_c{C}_{f}s+L_r}{L_s{L}_r{C}_f(L_s+L_r)s^3+{(L_s+L_r)}^2{R}_c{C}_f{s}^2+{(L_s+L_r)}^{2}s}---\left(7\right)$

In the formula, V _rBe converter phase voltage first-harmonic peak value, L _rBe the rectification side inductance of LCL filter, R _rBe the inductance side dead resistance of LCL filter, C _fBe the filter capacitor of LCL filter, R _cCapacitive side dead resistance for the LCL filter.

The resonance frequency of LCL system is:

$f_{\mathrm{res}}=\frac{1}{2\mathrm{\&pi;}}\sqrt{\frac{L_s+L_r}{L_s{L}_r{C}_f}}---\left(8\right)$

Obtain the transducer side inductance L by empirical equation _rFor:

$L_r=\frac{V_m}{2\sqrt{6}\mathrm{\&Delta;}{i}_{\max }{f}_k}---\left(9\right)$

In the formula, Δ i _MaxBe the largest ripple current of harmonic current, be generally 10%～20% of rated current, f _kBe switching frequency.

In addition, L _sBe generally L _r0～1 times.

Filter capacitor C _fFor:

$C_f\&le;5<figure-callout\; id="3"\; label="\%\; P"\; filenames="HDA00003166074200011.png"\; state="\{\{state\}\}">\%</figure-callout>\frac{P}{}\frac{}{3*2\mathrm{\&pi;}{{\mathrm{fV}}_m}^2}---\left(9\right)$

In the formula, P is power output, and f is supply frequency.

In addition, the filter inductance and the electric capacity that adopt in the monocycle control strategy should be as far as possible little, to reduce system's reactive loss.

As shown in Figure 4, select four groups of LCL parameters as shown in table 1 according to mentioned above principle, and draw corresponding Bode diagram and compare analysis.Clearly LCL filtering has more obvious inhibition than independent L filtering for current harmonics, and the inductance value is much smaller.

Table 1 LCL filter parameter

Sequence number	C f(μf)	L s(mH)	L r(mH)	R s(Ω)	R r(Ω)
						a	25	2.0	2.0	0.25	0.25
b	25	2.5	1.5	0.3	0.2
						c	25	1	2.5	0.15	0.3
d	0	2	2	0.25	0.25

2. emulation experiment

The present invention is by the PSCAD simulation software, the novel electric vehicle charger system based on the monocycle control strategy that the present invention is proposed has carried out simulating, verifying, and simulation result contrasted and analyze, only with part result of calculation correctness of the present invention and validity are described below.

Built three-phase PWM power inverter simulation model in the PSCAD analogue system, the system emulation parameter is as shown in table 2.

Table 2 system emulation parameter

Circuit	Parameter
		Switching frequency	10kHz
Dc bus capacitor	1980μf
		Load resistance	25Ω
The power supply phase voltage	400V
		Supply frequency	50Hz
Dc voltage	700V

As shown in Figure 5, the waveform of three-phase PWM power inverter A phase voltage, electric current and dc voltage during for stable state, current waveform (having amplified 3 times) near sinusoidal as can be seen, dc voltage stability, utilize among the PSCAD FFT module to analyze, phase current THD is 2.13%, and power factor is 0.993, has realized the control target of unity power factor substantially.

As shown in Figure 6, be that checking improves the dynamic property of control scheme, first load 6 be set by 25 Ω, 50 Ω that uprush, observe output waveform, A phase current sinuso sine protractor is still good as can be seen, and dc voltage tended towards stability about 2 cycles, and system can realize a smooth transition substantially.

As shown in Figure 7, the selector switch 5 of DC side points to B by A in main circuit, adjusts direct current adjustable voltage 8 simultaneously, the three-phase PWM power inverter by the rectification mode transition to inverter mode.When 3S, selector switch 5 points to B by A, and system finished by the seamless switching of rectification pattern to inverter mode through about 3 cycles, had realized the bi-directional of power.

Though above-mentionedly by reference to the accompanying drawings the specific embodiment of the present invention is described; but be not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various modifications that creative work can make or distortion still in protection scope of the present invention.

Claims (7)

1. novel electric vehicle charger based on the monocycle control strategy, it is characterized in that, comprise three phase mains, three phase mains is connected with the LCL filter, the LCL filter is connected with the input of three-phase PWM power inverter main circuit, the dc output end of the three-phase PWM power inverter electric capacity that supports in parallel; First load simultaneously and discharge loop are in parallel with the dc output end of three-phase PWM power inverter by selector switch; The control system of three-phase PWM power inverter is gathered the current signal i of LCL filter inductance _Rn, LCL filter and three-phase PWM power inverter main circuit input the voltage signal v of tie point _RnAnd the d. c. voltage signal U that supports the capacitor C two ends _Dc, corresponding pulse switch signal is exported in the work of control three-phase PWM power inverter.

2. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 1 is characterized in that, described three-phase PWM power inverter major loop adopts the three-phase full-controlled bridge of being made up of a plurality of switching devices.

3. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 1 is characterized in that described discharge loop comprises the series circuit of second load and direct current adjustable voltage.

4. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 1 is characterized in that the control system of described three-phase PWM power inverter comprises: a plurality of rest-set flip-flops, each rest-set flip-flop

End, Q end are all distinguished corresponding with the pulse switch signal of the upper and lower brachium pontis switching device of a brachium pontis; The R end of each rest-set flip-flop is connected with the output of corresponding comparator respectively, and its S end all is connected with the clock signal module; The forward end input signal of each comparator is by detecting current i _Rn, detect voltage v _RnWith 1/R _fModule, R _sModule interconnects and obtains, and the negative end input signal is sawtooth signal; Described sawtooth signal is by error signal V _mWith V _mThe superimposed generation of signal through the integrator generation; Described error signal V _mBe reference voltage and dc voltage U _DcDifference through the output signal of pi regulator.

5. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 4 is characterized in that described sawtooth waveforms carrier signal is V _m(1-t/ τ), t are time signal, and τ is time constant of integrator, gets τ=0.5T _s, T _sBe switch periods.

6. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 4 is characterized in that described detection current i _Rn, detect voltage v _RnWith 1/R _fModule, R _sThe interconnected relationship of module is: voltage signal v _RnMultiply by gain 1/R _f, obtain virtual current signal i _NfVirtual current i _NfMultiply by gain R _sObtain R _si _NfCurrent signal multiply by gain R _sObtain R _si _RnR _si _NfAnd R _si _RnThe superimposed comparison signal R that obtains _si _NO, i _NO=i _Nf+ i _Rn

7. a kind of novel electric vehicle charger based on the monocycle control strategy as claimed in claim 6 is characterized in that, described gain 1/R _fIn R _fBe the adjustable electric resistance, described gain 1/R _fIn R _sBe three phase mains equivalent internal resistance value.

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