CN103746445A - No-signal interconnection online type UPS parallel control method - Google Patents

Abstract

The invention discloses a no-signal interconnection online type UPS parallel control method comprising active power and reactive power calculation, phase lock adjustment, self-adaptive virtual resistor adjustment and output voltage control. In the adaptive virtual resistor adjustment, output impedance of a UPS inverter is adjusted to be resistivity. Benchmark amplitude is adjusted by using active power, benchmark angular frequency is adjusted by using reactive power and a benchmark phase is adjusted by using phase lock so that benchmark voltage is co-determined. An absolute value of the reactive power modulates a virtual resistance value so that a self-adaptive characteristic is realized. UPS output current or filtering induction current is multiplied by the virtual resistance value and then negatively fed back to the benchmark voltage so that reference voltage is obtained and the reference voltage is tracked. Closed loop feedback output quantity is modulated via pulse width so that the UPS inverter is controlled. Influence of frequency disturbance on power equalization caused by the phase lock can be effectively reduced so that accurate phase lock of UPS output voltage and commercial power voltage, UPS parallel operation high current sharing and great dynamic characteristic can be realized.

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 interconnected on line type UPS control method for parallel of a kind of no signal.

Background technology

Along with social development and scientific and technological progress, UPS(uninterrupted power supply) as the power supply of important events key equipment, obtained application more and more widely.Along with the reliability of user to ups power system and the requirement of power grade improve constantly, single UPS has demonstrated limitation gradually, modularization N+X parallel redundancy technology can improve reliability, flexibility and the capacity of ups power system greatly, also can effectively reduce system cost.

For the control method of inverter parallel according to having or not internal signal interconnection line to be divided between module to have line parallel and without the large class of line parallel two, there is line parallel to mainly contain centralized control, principal and subordinate's control and distributed control, distributed control can adopt again the meritorious and reactive power of active power and Reactive Power Control, instantaneous Average Current Control and PQ() droop control etc., without line parallel mainly based on PQ droop control.Centralized control mode need to arrange a centralized control module, for realizing the synchronous and current-sharing of each module, simple in structure, current-sharing effect is better, but in focus control mode, the reference signal of all parallel modules is all provided by centralized control module, 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 take a module as primary module, and remaining module is from module, and intermodule status is not reciprocity, is the one of centralized control is improved.But when primary module break down and can not be normally when providing voltage and frequency reference signal from module, parallel system is by cisco unity malfunction, system does not realize redundancy, reliability is also lower.In distributed control mode, status between each inversion module is equal, there is no master-slave, after breaking down, certain inverter just automatically logs off, and all the other inverters are unaffected, distributed control mode line is more complicated, when modules apart from each other, long holding wire exists and disturbs, and affects the reliability of system.When the inverter parallel system that the inverter based on PQ droop control is compared signal link without interconnect parallel system has that reliability is high, redundancy is high and builds line simple and convenient, can realize features such as " hot plugs ", be the trend of following inverter development.

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

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

Summary of the invention

For the existing above-mentioned technical problem of prior art, the invention provides the interconnected on line type UPS control method for parallel of a kind of no signal, can be when UPS output voltage be accurate phase-locked with line voltage, realized the height current-sharing of parallel system, and in the large-signal perturbation process such as the load saltus step in allowed band or DC bus fluctuation, phase-locked loop continues running to keep the phase place locking of UPS output voltage with 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 collection UPS, and the angular frequency of detection of grid voltage _g;

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

(3), according to described active-power P and reactive power Q, by droop control algorithm, determine amplitude E and the angular frequency of reference voltage; The output phase that output voltage described in making and line voltage obtain through phase-locked adjusting is as the phase place of reference voltage

and then generation reference voltage;

(4) to the reactive power after just getting | Q| carries out PD(ratio-differential) regulate and be regulated resistance value, and then default reference resistor value and this regulation and control resistance value are added obtain virtual resistance value, finally described virtual resistance value and output current are multiplied each other and obtain 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 and obtain modulation signal, last according to described modulation signal by SPWM(sinusoidal pulse width modulation) technical construction obtains one group of pwm signal and controls with the inverter to UPS.

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

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

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

Wherein: N is the sampling number in the current sampling period, v (k) and i (k) are respectively output voltage values and the output current value of k sampled point in the current sampling period, the output current value that i (p) is p sampled point and p leading k 1/4th sampling periods of sampled point of sampled point, 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 necessary condition is created in phase place locking.

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

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

In described droop control algorithm, for active-power P, modulation includes the adjusting of amplitude ring or effective value ring adjusting, and 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, the amplitude that V is output voltage or effective value, the transfer function that PI (s) regulates for PI.

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

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

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), according to reference voltage, based on following formula, carry out closed loop feedback control:

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 adjusting UPS output voltage phase place and line voltage are synchronous, can use multiple Phase Lock Technique to realize phase-locked, as Phase Lock Technique, the Phase Lock Technique based on coordinate transform and the Phase Lock Technique based on Instantaneous Power Theory etc. based on crossing zero balancing.The reference voltage that active power, reactive power and phase-locked module provide is jointly followed the tracks of in acting as of last closed loop feedback controlling unit, can use various feedback control structure to realize, as encircled three rings etc. in 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, can in various control loop, use feedfoward control technology simultaneously.

Compared with prior art, the inventive method is when UPS output voltage is accurate phase-locked with line voltage, realized the height current-sharing of parallel system, and during the large-signal disturbances such as the load saltus step in allowed band or DC bus fluctuation, phase-locked loop, without deactivating, guarantees to carry out the reliability of 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 of not being with amplitude ring.

Fig. 4 is the UPS unit control block diagram with 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 more specifically to describe the present invention, below in conjunction with the drawings and the specific embodiments, technical scheme of the present invention is elaborated.

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 equivalent model in parallel, can calculate Z _onn(n=1 while being resistive, 2 ..., n) active power and the reactive power of platform UPS output are 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 adding, Z _linenfor line resistance value, R _vnadd adjust Z _nbe resistive.

With reference to IEEE, be power measurement part in the trial edition 1459-2000 that formulates of instrument design, 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 to be applicable to the various power calculation with periodic waveform, above formula is further out of shape:

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

Because the output voltage of UPS is sinusoidal wave, that is:

v _o＝Vcos(ωt) (1-3)

Magnitude of voltage is carried out to integration can be obtained:

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

To in formula (1-4) substitution formula (1-2) and to it, carry out discretization, obtain:

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

In above formula: N represents the sampling number of one-period.By formula (1-5), can be found out, active power is to average after the product of instantaneous voltage and current instantaneous value adds up in one-period; Reactive power is to average after the product of current voltage instantaneous value and the current instantaneous value in leading 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 * are respectively UPS inverter output voltage amplitude and frequency when unloaded, ω _gfor the angular frequency of line voltage, k _peand k _qwbe respectively the sagging coefficient of active power and reactive power, P* and Q* are respectively active power and reactive power nominal value, are generally made as the power rating that module is the most often worked.In present embodiment, E*=311V, P*=Q*=0, k _pe=0.001, k _qw=0.0001.

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

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 hour, by reducing Z _nreactive power is increased.Z _nadjusting 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, virtual resistance made to adjusting.Differential regulates and contributes to accelerate virtual resistance governing speed when large-signal disturbance, thereby improves the dynamic property that reactive power is divided equally, and works as k _qdbe made as at 1 o'clock, PD regulates and deteriorates to P adjusting.In present embodiment, k _qp=0.006, k _qd=2 × 10 ^-5, R _v ^*=0.4 Ω.

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

According to aforementioned analysis, can draw UPS unit control block diagram as shown in Figure 3 and Figure 4, the UPS unit control block diagram with amplitude ring as described in Figure 3, does not pass through the phase place that the sagging amplitude E obtaining of active power power, the sagging angular frequency obtaining of reactive power power and phase-locked loop provide

jointly provide reference voltage, i.e. v in Fig. 3 _ref ^*.UPS unit control block diagram with amplitude ring as shown in Figure 4, passes through the sagging E that obtains of active power, the E that E obtains through amplitude ring ₂, the phase place that provides of the sagging ω obtaining of reactive power power and phase-locked loop

jointly provide reference voltage, i.e. v 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 benchmark 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, to above-mentioned reference voltage, obtains reference voltage, i.e. v in Fig. 3 and Fig. 4 _ref.Here transient current can be UPS output transient current i _o, can be also filter inductance current i _l.Reference voltage is after output voltage controller, and the modulation signal of controlled 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 load resistance is switched to 58 Ω parallel operation current-sharing waveform by 29 Ω, Fig. 6 (b) is load resistance is switched to 29 Ω parallel operation current-sharing waveform by 58 Ω.I ₀₁and i ₀₂represent respectively the output current of two UPS.As we can see from the figure in the situation that phase place locks, the effectively current-sharing of on line type UPS parallel system, and there is good dynamic response capability.Current-sharing and phase-locked can simultaneously realization.

In present embodiment, rectified load is as shown in Fig. 7 (a), and Fig. 7 (b) is the current-sharing waveform that connects rectified load.Wherein R _s=1 Ω, capacitor C ₀be 2670 μ F, resistance R is 58 Ω.From Fig. 7 (b), can find out, under phase place locking condition, combining system also can be realized good current-sharing for rectified load.

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

Claims (8)

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

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

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

(3), according to described active-power P and reactive power Q, by droop control algorithm, determine amplitude E and the angular frequency of reference voltage; The output phase that output voltage described in making and line voltage obtain through phase-locked adjusting is as the phase place of reference voltage

and then generation reference voltage;

(4) to the reactive power after just getting | Q| carries out PD adjusting and is regulated resistance value, and then default reference resistor value and this regulation and control resistance value are added obtain virtual resistance value, finally described virtual resistance value and output current are multiplied each other and obtain 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 and obtain modulation signal, finally according to described modulation signal, by SPWM technical construction, obtain one group of pwm signal and control with the inverter to UPS.

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), 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 the current sampling period, v (k) and i (k) are respectively output voltage values and the output current value of k sampled point in the current sampling period, the output current value that i (p) is p sampled point and p leading k 1/4th sampling periods of sampled point of sampled point, k is natural number and 1≤k≤N.

4. UPS control method for parallel according to claim 1, is characterized in that: 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.

5. UPS control method for parallel according to claim 1, is characterized in that: in described droop control algorithm, for active-power P, modulation includes the adjusting of amplitude ring or effective value ring adjusting, and 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, the amplitude that V is output voltage or effective value, the transfer function that PI (s) regulates for PI.

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

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

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

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

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

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

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.

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