CN103746445B - The on line type UPS control method for parallel that a kind of no signal is interconnected - Google Patents

Abstract

The invention discloses the on line type UPS control method for parallel that a kind of no signal is interconnected, comprise active power and reactive power calculating, phase-locked adjustment, the adjustment of self adaptation virtual resistance and output voltage control; Wherein, adapt to virtual resistance adjustment and the output impedance of UPS inverter is adjusted to resistive, use active power regulation reference amplitude, reactive power regulates reference angle frequency, and phase-locked adjustment reference phase, determines reference voltage jointly.Reactive power absolute value is modulated virtual resistance value, realizes its adaptive characteristic; UPS output current or filter inductance electric current are multiplied by virtual resistance value, and negative feedback, to reference voltage, obtains reference voltage, and then track reference voltage, its closed loop feedback output variable by pulse-width modulation with control UPS inverter.The present invention effectively can weaken the phase-locked frequency disturbance brought to the impact of power-sharing, realizes UPS output voltage with line voltage accurately phase-locked and UPS parallel operation highly current-sharing and good dynamic characteristic.

Description

The on line type UPS control method for parallel that a kind of no signal is interconnected

Technical field

The invention belongs to power supply unit control technology field, be specifically related to the on line type UPS control method for parallel that a kind of no signal is interconnected.

Background technology

Along with the development of society and the progress of science and technology, UPS(uninterrupted power supply) as the power supply of important events key equipment, obtain and apply more and more widely.Along with user improves constantly the reliability of ups power system and the requirement of power grade, single UPS demonstrates limitation gradually, modularization N+X parallel redundancy technology can improve the reliability of ups power system, flexibility and capacity greatly, also effectively can reduce system cost.

Control method for inverter parallel has line parallel and without the large class of line parallel two according to being divided into or without internal signal interconnection line between module, line parallel is had to mainly contain centralized control, master & slave control and distributed AC servo system, distributed AC servo system can adopt again active power and Reactive Power Control, instantaneous Average Current Control and PQ(are meritorious and reactive power) droop control etc., without line parallel mainly based on PQ droop control.Centerized fusion mode needs to arrange a centralized control module, for realizing the synchronous of each module and current-sharing, structure is simple, current-sharing effect is better, but the reference signal of all parallel modules is all provided by centralized control module in focus control mode, when centralized control module breaks down, whole system will be collapsed.Centralized control is because integrity problem is seldom used now.Master slave control mode is with a module for primary module, and remaining module is from module, and intermodule status is not reciprocity, is to improve the one of centerized fusion.But when primary module break down and can not normally for providing voltage and frequency reference signal from module time, parallel system is by cisco unity malfunction, and system does not realize redundancy, and reliability is also lower.In distributed control mode, status between each inversion module is equal, there is no master-slave, just automatically log off after certain inverter breaks down, and all the other inverters are unaffected, distributed control mode line is more complicated, when modules is apart from each other, there is interference in long holding wire, the reliability of influential system.When inverter based on PQ droop control has that reliability is high, redundancy is high and build without the inverter parallel system that interconnect parallel system compares signal link, line simple and convenient, features such as " hot plugs " can be realized, be the trend of following inverter development.

PQ droop control realizes power-sharing by the amplitude of regulation output voltage and frequency.The wireless parallel technology of inverter of current employing PQ droop control becomes to achieve a series of achievement.And without the difference that line parallel is maximum, on line type UPS is that on line type UPS is while in parallel without line parallel and inverter, its output voltage also needs same line voltage phase-locked, and this also needs to be realized by the frequency of regulation output voltage.Power-sharing and phase-locked these two kinds adjustments all need regulation output frequency, but owing to regulating target different, are easy to produce conflict, and result makes parallel system can not steady operation, failure even in parallel.Therefore inverter can not directly apply on line type UPS parallel system based on the wireless parallel technology of PQ droop control.

Publication number is that the Chinese patent of CN1581628 discloses a kind of wireless parallel control method and system, it is based on the UPS output impedance of perception, utilize emulation P-ω and Q-V slope sagging curve realize inverter without line parallel and phase-locked and current-sharing automatically, but this technology does not take control measure with regard to inverter output voltage and the phase-locked link of civil power to the adverse effect that parallel current-sharing brings, realize effective PGC demodulation and stable current-sharing is difficult simultaneously.

Summary of the invention

For the above-mentioned technical problem existing for prior art, the invention provides the on line type UPS control method for parallel that a kind of no signal is interconnected, can while UPS output voltage be accurately phase-locked with line voltage, achieve the height current-sharing of parallel system, and in the large-signal perturbation process such as load jump in allowed band or DC bus fluctuation, phase-locked loop continues running to keep UPS output voltage with the PGC demodulation of line voltage.

The on line type UPS control method for parallel that no signal is interconnected, comprises the steps:

(1) output voltage and the output current of UPS is gathered, and the angular frequency of detection of grid voltage _g;

(2) active-power P and the reactive power Q of UPS is calculated according to described output voltage and output current;

(3) according to described active-power P and reactive power Q, by amplitude E and the angular frequency of droop control algorithm determination reference voltage; The output phase place that described output voltage and line voltage are obtained through phase-locked adjustment is as the phase place of reference voltage and then generation reference voltage;

(4) to through getting the reactive power just | Q| carries out PD(proportional-plus-derivative) regulate and be regulated resistance value, and then the reference resistor value preset is added with this regulation and control resistance value obtain virtual resistance value, finally described virtual resistance value being multiplied with output current obtains virtual resistance voltage;

(5) make described reference voltage deduct virtual resistance voltage and obtain reference voltage, and then carry out closed loop feedback according to described reference voltage and control to obtain modulation signal, finally according to described modulation signal by SPWM(sinusoidal pulse width modulation) technical construction obtains one group of pwm signal to control the inverter of UPS.

Described output current is load current or the filter inductance electric current of UPS outlet side.

In described step (2), calculate active-power P and the reactive power Q of UPS according to following formula:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}v\left(k\right)i\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}v\left(k\right)i\left(p\right)\end{array}\right.$

Wherein: N is the sampling number in current sample period, v (k) and i (k) is respectively output voltage values and the output current value of a kth sampled point in current sample period, i (p) is the output current value of p sampled point and p the advanced kth of a sampled point sampled point 1/4th sampling period, and k is natural number and 1≤k≤N.

Described droop control algorithm is based on following formula:

$\left\{\begin{array}{c}E=E^{*}-k_{\mathrm{pe}}(P-P^{*})\\ \mathrm{\ω}={\mathrm{\ω}}_g+k_{\mathrm{qw}}(Q-Q^{*})\end{array}\right.$

Wherein: P ^*and Q ^*be respectively the reference value of active power and reactive power, k _peand k _qwbe respectively the sagging coefficient of active power and reactive power, E ^*for the reference value of output voltage.Coefficient k _qwchoose and should make k _qw(Q-Q ^*) product enough little, make output voltage angular frequency approximate line voltage angular frequency _g, namely in error allowed band, realize Frequency Locking, for PGC demodulation creates necessary condition.

In described step (3), generate reference voltage according to following formula:

Wherein: V _reffor reference voltage, t is the time.

Include amplitude ring for active-power P modulation in described droop control algorithm to regulate or effective value ring adjustment, specific algorithm is as follows:

$\left\{\begin{array}{c}E=\mathrm{PI}\left(s\right)[E^{*}-k_{\mathrm{pe}}(P-P^{*})-V]\\ \mathrm{\ω}={\mathrm{\ω}}_g+k_{\mathrm{qw}}(Q-Q^{*})\end{array}\right.$

Wherein: P ^*and Q ^*be respectively the reference value of active power and reactive power, k _peand k _qwbe respectively the sagging coefficient of active power and reactive power, E ^*for the reference value of output voltage, V is amplitude or the effective value of output voltage, the transfer function that PI (s) regulates for PI.

In described step (4), according to following formula to through getting the reactive power just | Q| carries out PD adjustment:

$R_c=K_p\left|Q\right|+K_d\frac{d\left|Q\right|}{\mathrm{dt}}$

Wherein: R _cfor regulation and control resistance value, K _pand K _dbe respectively proportionality coefficient and differential coefficient, t is the time.

In described step (5), carry out closed loop feedback control according to reference voltage based on following formula:

m _c＝PI(s)(V _res-V _o)

Wherein: m _cfor modulation signal, V _resfor reference voltage, V _ofor output voltage, the transfer function that PI (s) regulates for PI.

The equal separate connection of each UPS of parallel connection is integrated with to the control module of above-mentioned control method.Wherein, phase-locked governing loop is that adjustment UPS output voltage phase place and line voltage are synchronous, multiple Phase Lock Technique can be used to realize phase-locked, as the Phase Lock Technique based on Zero-cross comparator, the Phase Lock Technique based on coordinate transform and the Phase Lock Technique etc. based on Instantaneous Power Theory.The reference voltage that jointly provides of active power, reactive power and phase-locked module is followed the tracks of in acting as of last closed loop feedback controlling unit, various feedback control structure can be used to realize, as voltage monocycle, outer voltage current inner loop dicyclo, effective value outer shroud voltage inter-loop dicyclo, amplitude outer shroud voltage inter-loop dicyclo, effective value outer shroud electric current and voltage inner ring three ring etc., feed forward control techniques can be used in various control loop simultaneously.

Compared with prior art, the inventive method is while UPS output voltage is precisely phase-locked with line voltage, achieve the height current-sharing of parallel system, and during the large-signal disturbances such as the load jump in allowed band or DC bus fluctuation, phase-locked loop, without the need to deactivating, ensures the reliability of carrying out bypass changeover in large-signal perturbation process.

Accompanying drawing explanation

Fig. 1 is the schematic diagram in parallel of no signal interconnection line ups system.

Fig. 2 is the equivalent model schematic diagram of ups system parallel connection.

Fig. 3 is the UPS unit control block diagram not with amplitude ring.

Fig. 4 is the UPS unit control block diagram of band amplitude ring.

Fig. 5 is parallel system output voltage and the phase-locked oscillogram of line voltage.

Fig. 6 (a) carries current-sharing oscillogram for parallel system band resistive load is switched to cutting of 58 Ω by 29 Ω.

Fig. 6 (b) carries current-sharing oscillogram for parallel system band resistive load is switched to cutting of 29 Ω by 58 Ω.

Fig. 7 (a) for parallel system with rectified load schematic diagram.

Fig. 7 (b) is the current-sharing oscillogram of parallel system band rectified load.

Embodiment

In order to more specifically describe the present invention, below in conjunction with the drawings and the specific embodiments, technical scheme of the present invention is described in detail.

Fig. 1 is n platform no signal interconnection line UPS parallel system schematic diagram, and each UPS unit is connected in parallel by output being connected to AC bus (ac bus).Fig. 2 is n platform ups system parallel equivalent model, can calculate Z _onin time resistive n-th (n=1,2 ..., n) platform UPS export active power and reactive power be respectively

$P_n=\frac{U_n}{Z_n}(E_n-U_n)\cos {\mathrm{\φ}}_n---\left(1\right)$

$Q_n=-\frac{U_n}{Z_n}{E}_n\sin {\mathrm{\φ}}_n---\left(2\right)$

Wherein: Z _n=Z _on+ R _vn+ Z _linen, Z _onfor UPS inverter equivalent output impedance, R _vnfor the virtual resistance added, Z _linenfor line resistance value, R _vnadd adjustment Z _nin resistive.

Be power measurement portion in the trial edition 1459-2000 that formulates of instrument design with reference to IEEE, obtain following rating formula:

$p=\mathrm{vi},P=\frac{1}{\mathrm{kT}}{\∫}_{\mathrm{\τ}}^{\mathrm{\τ}+\mathrm{kT}}\mathrm{pdt},Q=\frac{\mathrm{\ω}}{\mathrm{kT}}{\∫}_{\mathrm{\τ}}^{\mathrm{\τ}+\mathrm{kT}}i[\∫\mathrm{vdt}]\mathrm{dt}---(1-1)$

In formula, v is output voltage, and i is output current, and p is power output instantaneous value, and P is active power of output, and Q is output reactive power.

In formula (1-1), institute's calculating formula is applicable to the various power calculation with periodic waveform, is out of shape further above formula:

$\left\{\begin{array}{c}P=\frac{1}{T_o}{\∫}_0^{T_o}{v}_o{i}_o\mathrm{dt}\\ Q=\frac{\mathrm{\ω}}{T_o}{\∫}_0^{T_o}(\∫v_o\mathrm{dt})i_o\mathrm{dt}\end{array}\right.(1-2)$

Output voltage due to UPS is sinusoidal wave, that is:

v _o＝Vcos(ωt) (1-3)

Carry out integration to magnitude of voltage can obtain:

$\∫v_o\mathrm{dt}=\∫v\cos \left(\mathrm{\ωt}\right)\mathrm{dt}=\frac{V}{\mathrm{\ω}}\cos (\mathrm{\ωt}-\frac{\mathrm{\π}}{2})---(1-4)$

Formula (1-4) to be substituted in formula (1-2) and discretization carried out to it, obtaining:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{1}{\mathrm{\Σ}}}v\left(k\right)i\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\mathrm{\Σ}}}v\left(k\right)i(k+\frac{N}{4})\end{array}\right.---(1-5)$

In above formula: N represents the sampling number of one-period.As can be seen from formula (1-5), active power is average after the product of instantaneous voltage and current instantaneous value adds up in one-period; Reactive power is average after the product of the current instantaneous value in current voltage instantaneous value and advanced 1/4th cycles adds up in one-period.

The power droop control equation that can obtain resistive output impedance from formula (1) and formula (2) is

E＝E ^*-k _pe(P-P ^*) （3）

ω=ω _g+ k _qw(Q-Q ^*) (4) wherein: E* and ω * be respectively UPS inverter unloaded time output voltage amplitude and frequency, ω _gfor the angular frequency of line voltage, k _peand k _qwbe respectively active power and the sagging coefficient of reactive power, P* and Q* is respectively active power and reactive power nominal value, is generally set to the power rating that module the most often works.In present embodiment, E*=311V, P*=Q*=0, k _pe=0.001, k _qw=0.0001.

UPS output frequency ω needs acceptance two kinds adjustment.Regulate 1: modulated by reactive power Q, divide equally to realize reactive power, shown in (4); Regulate 2: need to regulate UPS output frequency phase-locked with line voltage to realize its output voltage.Easy understand, when adjustment 1 reaches stable state, regulates 2 will break the stable state of adjustment 1.As long as phase-locked loop action, reactive power is divided equally just needs the moment to regulate, and exists with a kind of " unstable state " close to stable state.

Observation type (2), can find out that the absolute value of reactive power reduces along with the increase of resistance value Zn, therefore, and adaptively changing Z _nsize be conducive to dividing equally of reactive power, when reactive power is larger, by increase Z _nreactive power is reduced, when reactive power is less, by reducing Z _nreactive power is increased.Z _nadjustment by R _vnadjustment can realize easily, present embodiment propose self adaptation virtual resistance be:

$R_c={R_v}^{*}+k_{\mathrm{qp}}\left|Q\right|+K_{\mathrm{qd}}\frac{d\left|Q\right|}{\mathrm{dt}}---\left(5\right)$

In formula: R _v ^*for the virtual resistance fiducial value of setting, k _qpand k _qdbe respectively ratio and differential adjustment factor, by reactive power absolute value, adjustment made to virtual resistance.Differential regulates and contributes to accelerating virtual resistance governing speed when large-signal disturbance, thus improves the dynamic property that reactive power divides equally, and works as k _qdwhen being set to zero, PD regulates and deteriorates to P adjustment.In present embodiment, k _qp=0.006, k _qd=2 × 10 ^-5, R _v ^*=0.4 Ω.

Through type (5) bears the idle Main Function dividing equally adjustment, and formula (4) just helps out in reactive power regulates, its adjustment factor k _qwcan establish very little, make UPS output voltage frequency can follow the tracks of mains frequency close to indifference, realize same civil power phase-locked.Meanwhile, owing to there being formula (5) to play a leading role in idle dividing equally in adjustment, when phase-locked loop action, power-sharing still can reach stable state.When large-signal disturbance, formula (5) can regulate reactive power to divide equally, phase-locked loop also without the need to exiting, sustainable effect.Idlely divide equally adjustment and phase-locked adjustment can Approximate Decoupling, can independently design and control.

UPS unit control block diagram as shown in Figure 3 and Figure 4 can be drawn according to Such analysis, UPS unit control block diagram not with amplitude ring as described in Figure 3, through the phase place that the sagging angular frequency that obtains of sagging amplitude E, the reactive power power obtained of active power power and phase-locked loop provide jointly provide reference voltage, the v namely in Fig. 3 _ref ^*.UPS unit control block diagram with amplitude ring as shown in Figure 4, obtains E, the E that E obtains through amplitude ring through active power is sagging ₂, the phase place that provides of the sagging ω that obtains of reactive power power and phase-locked loop jointly provide reference voltage, the v namely in Fig. 4 _ref ^*; In present embodiment, the calculation expression of amplitude ring is as follows:

E ₂=PI (s) (E-E _a) (6) wherein: E _afor the amplitude of output voltage, the transfer function that PI (s) regulates for PI, the proportionality coefficient that wherein PI regulates is set as 0.5, and integral coefficient is set as 100.

By reference virtual resistance value R _v ^*be added as final virtual resistance value R with the value of reactive power absolute value after PD regulates _v, by R _vafter being multiplied by transient current, negative feedback is to above-mentioned reference voltage, obtains reference voltage, the v namely in Fig. 3 and Fig. 4 _ref.Here transient current can be that UPS exports transient current i _o, also can be filter inductance current i _l.Reference voltage, after output voltage controller, obtains the modulation signal of control UPS output voltage, through the switching device of SPWM driver drives UPS inverter.In present embodiment, output voltage controller carries out closed loop feedback control based on following formula:

m _c＝PI(s)(v _ref-v _o) （7）

Wherein: m _cfor modulation signal, V _resfor reference voltage, V _ofor output voltage, the transfer function that PI (s) regulates for PI, the proportionality coefficient that wherein PI regulates is set as 0.002, and integral coefficient is set as 22.

In present embodiment, inverter adopts half-bridge topology, and filter inductance is 5mH, and filter capacitor is 6.8 μ F, positive and negative DC bus-bar voltage V _inbe 390V.

Fig. 5 be parallel UPS system output voltage with the phase-locked waveform of line voltage, Fig. 6 (a) is that load resistance is switched to the parallel operation current-sharing waveform of 58 Ω by 29 Ω, and Fig. 6 (b) is that load resistance is switched to the parallel operation current-sharing waveform of 29 Ω by 58 Ω.I ₀₁and i ₀₂represent the output current of two UPS respectively.As we can see from the figure when PGC demodulation, on line type UPS parallel system can effectively current-sharing, and has good dynamic response capability.Current-sharing and phase-lockedly can simultaneously to realize.

In present embodiment, rectified load is as shown in Fig. 7 (a), and Fig. 7 (b) is the current-sharing waveform connecing rectified load.Wherein R _s=1 Ω, electric capacity C ₀be 2670 μ F, resistance R be 58 Ω.As can be seen from Fig. 7 (b), under phase lock condition, combining system also can realize good current-sharing for rectified load.

Therefore, use the present invention can while UPS output voltage is accurately phase-locked with line voltage, realize the current-sharing that parallel system is good, the present invention be applicable to the on line type UPS system of the interconnected parallel connection of no signal.

Claims (6)

1. the on line type UPS control method for parallel that no signal is interconnected, comprises the steps:

(1) output voltage and the output current of UPS is gathered, and the angular frequency of detection of grid voltage _g;

(2) active-power P and the reactive power Q of UPS is calculated according to described output voltage and output current;

(3) according to described active-power P and reactive power Q, by amplitude E and the angular frequency of droop control algorithm determination reference voltage; The output phase place that described output voltage and line voltage are obtained through phase-locked adjustment is as the phase place of reference voltage and then generation reference voltage;

Include amplitude ring for active-power P modulation in described droop control algorithm to regulate or effective value ring adjustment, specific algorithm is as follows:

$\left\{\begin{array}{c}E=PI\left(S\right)\[E^{*}-k_{pe}\left(P-P^{*}\right)-V\]\\ \mathrm{\ω}={\mathrm{\ω}}_g+k_{qw}\left(Q-Q^{*}\right)\end{array}\right.$

Wherein: P ^*and Q ^*be respectively the reference value of active power and reactive power, k _peand k _qwbe respectively the sagging coefficient of active power and reactive power, E ^*for the reference value of output voltage, V is amplitude or the effective value of output voltage, the transfer function that PI (s) regulates for PI;

(4) to through getting the reactive power just | Q| carries out PD and regulates and be regulated resistance value, and then the reference resistor value preset is added with this regulation and control resistance value obtain virtual resistance value, finally described virtual resistance value being multiplied with output current obtains virtual resistance voltage;

(5) make described reference voltage deduct virtual resistance voltage and obtain reference voltage, and then according to described reference voltage carry out closed loop feedback control obtain modulation signal, finally obtain one group of pwm signal to control the inverter of UPS according to described modulation signal by SPWM technical construction.

2. UPS control method for parallel according to claim 1, is characterized in that: described output current is load current or the filter inductance electric current of UPS outlet side.

3. UPS control method for parallel according to claim 1, is characterized in that: in described step (2), calculates active-power P and the reactive power Q of UPS according to following formula:

$\left\{\begin{array}{c}P=\frac{1}{N}\underset{k=1}{\overset{N}{\Σ}}v\left(k\right)i\left(k\right)\\ Q=\frac{1}{N}\underset{k=1}{\overset{N}{\Σ}}v\left(k\right)i\left(p\right)\end{array}\right.$

Wherein: N is the sampling number in current sample period, v (k) and i (k) is respectively output voltage values and the output current value of a kth sampled point in current sample period, i (p) is the output current value of p sampled point and p the advanced kth of a sampled point sampled point 1/4th sampling period, and k is natural number and 1≤k≤N.

4. UPS control method for parallel according to claim 1, is characterized in that: in described step (3), generates reference voltage according to following formula:

Wherein: V _reffor reference voltage, t is the time.

5. UPS control method for parallel according to claim 1, is characterized in that: in described step (4), according to following formula to through getting the reactive power just | Q| carries out PD adjustment:

$R_c=K_p\left|Q\right|+K_d\frac{d\left|Q\right|}{dt}$

Wherein: R _cfor regulation and control resistance value, K _pand K _dbe respectively proportionality coefficient and differential coefficient, t is the time.

6. UPS control method for parallel according to claim 1, is characterized in that: in described step (5), carry out closed loop feedback control according to reference voltage based on following formula:

m _c＝PI(s)(V _res-V _o)

Wherein: m _cfor modulation signal, V _resfor reference voltage, V _ofor output voltage, the transfer function that PI (s) regulates for PI.