Method of automatic balancing adjustment of currents in multi-phase system by specified phase

FIELD: electricity.

SUBSTANCE: improved efficiency of method implementation is achieved due to multi-phase system balancing against specified phase, or phase with load current close to mean current, or less loaded phase defined as reference phase. By the method, balancing is implemented by generation of pre-formed currents by means of additional power source in each of remaining (n-1) phases, so that in each balanced (n-1) phase of the main n-phase network, the geometrical sum of currents generated in balanced phase and with load current is equal modulo to current in reference phase, and angle formed by the current of reference phase and total current of balanced phase following the reference phase at forward sequence of phases, as well as between total currents of neighbouring (n-1) balanced phases is equal to electrical degrees.

EFFECT: improved efficiency of multi-phase system balancing due to increased response and simplified implementation, extended application sphere, improved economy.

1 dwg

 

Way to relate to electrical engineering and can be used for balancing multi-phase and single-phase loads with time-varying parameters.

There is a method of automatic control of symmetry and three-phase voltage system (1), the implementation of which is the measurement and adjustment of the currents reverse sequence simmetriyami system. The method has similar shortcomings, lies in the complexity of its implementation, as well as low performance, due to the search method of tuning of the parameters.

There is a method of automatic balancing voltage submersible induction motor is implemented in the device (2)through which symmetrist the voltage at the terminals of the consumer by regulating the resistance of the power supply circuit of the individual phases. This method is closest to the technical nature of the claimed and is therefore adopted as a prototype. Known prototype method has drawbacks consisting in low efficiency, low performance and low cost, and inability to use method for balancing group loads in its implementation.

The problem solved by the invention, the efficiency of the balancing multiphase systems by improving performance, simplified the Oia implementation, expand the scope and improve the efficiency in the process of balancing.

This is achieved by using an additional n-phase of the power source of the asymmetric n-phase network symmetrist on a given phase, which is pre-selected as a reference. The last choice is carried out in dependence on a combination of complex loads the individual phases of the n-phase network. As a reference - choose either phase with the load current, similar to the average, or the least loaded phase, the process of balancing is carried out by generating in each of the (n-1) simmetriyami phase load main n-phase circuit currents, in which the pre-form module and phase angle so that in each phase the geometric sum mentioned currents and currents, which currents of n-phase unbalanced load would be equal to the current reference phase, and the angle formed by the current past and current referred to the geometric sum of the currents in the phase, next support at direct alternation of phases, as well as between the currents of geometric sums neighboring simmetriyami phase would be equal toalrrady.

The essence of the method is determined as follows. As you know, any n-phase system is symmetrical, if complex load its phases are equal, i.e. if equal what about the module currents of individual phases, and the phase angle between them is equal towhere n is the number of phases of the system. Thus, on this basis, in an n-phase system it is possible to achieve balancing, balancing the currents in the individual phases, relative to the current of any of its phases. In some cases, when in advance, depending on the combination of complex loadings of the individual phases, as the reference is selected one of the phases or phase with the load current, similar to the average, or the least loaded phase, the power taken from the n-phase simmetriyami system is optimal. Since the load currents are parameters set by the load, the balancing can be achieved by geometrical addition of currents from an additional source of current or voltage so that in each simmetriyami phase geometric sum generated from an additional source current and the load current simmetriyami phase would be equal to a current reference phase, and the angle formed by the current of the reference phase and the currents mentioned geometric sums currents, as well as between the latter would be. The effectiveness of using the claimed process in the transition from balancing three-phase loads to the compensation of one or a group of single-phase loads do not depend on properties of the settlement of the tournament, and is determined only by the capacity of an additional source of power.

The drawing shows a diagram illustrating the essence of the proposed method.

The scheme introduced the following notation:

1 - the main n-phase power system;

2 - unbalanced load;

3, 4, 5 sensors form the phase current;

6 - the first phase-shifting block;

7 - the second phase-shifting block;

8 - unit forming differential signals;

9 is an additional source of power;

10 is a logical unit of analysis reference phase.

An example of the method considered in respect of the three-phase system. In advance, depending on the situation (depending on the ratio of the complexes loads), as a reference selects one of the phases or phase with the load current, similar to the average, or the least loaded phase, and further balancing is carried out with respect to the selected phase. From the outputs of the sensors of the current shape of phases 3, 4 and 5 signals proportional to the signal shape of the phase current n-phase simmetriyami system, proceed to the group of information inputs of the second phase-shifting block 7, consisting of separate identical modules, the number of which is equal to the number of phases, and at the same time information on the inputs of the logical unit of analysis given phase 10 and information on the inputs of the first phase shifting unit 6. In block 10 through the your comparison of the currents of the individual phases of them is selected the phase reference - or phase with the load current, similar to the average, or the least loaded phase. For example, we have determined that the balancing will occur relative to the least loaded phase, i.e. the phase with the minimum load current. By analyzing the phases in the unit 10 selects the least loaded phase, is determined as a reference, and its output generated control signals prohibition (resolution) of the individual modules of the logical block forming a differential signal 8 supplied to the group of control inputs of the latter. The absence of signals of the ban on individual output unit 10 is equivalent to the presence in the latter of the signals permits. Blocks 6, 7, involved in the formation of the signal at the output of block 8, consist of modules that are related to a specific phase. For example, the modules 6.1 and 7.1 are related to phase "A"modules 6.2 and 7.2 - phase "B"modules 6.3 and 7.3 - phase "C". In block 7, the signals proportional to the currents of phases "A", "b" and "C"are shifted by an angle equal to 180 elvrum (inverted)relative to the signals at the outputs of blocks 3, 4 and 5. Unit 6, in General, consists of n×2 - phase-shifting chains - per-phase 2 (in each module consists of 2 phase-shifting of the chain). In the continuously involved only two of them, i.e. only one specific module. A pair of such chains, or the module in which they are included, all who are depending on, which of the phases is selected as a reference. Each pair of phase-shifting chains a signal proportional to the current signal of the reference phase, in the General case is shifted respectively by the anglewhere m is the number of the phase that follows the reference with direct sequencing of phases, n is the number of phases in the system. In this case, one of the chains separate module mentioned signal is shifted respectively at 120 and the other 240 alcrudo, depending on the number of phases, for balancing which it will be used. From the output of block 6 signals proportional to the current reference, the least loaded phase and shifted by 120 and 240 alrrady respectively, are received on the first group of inputs of the block forming differential signals 8, to a second group of inputs which receives signals proportional to the currents form loads simmetriyami phases formed in the sensor current shape of phases 3, 4 and 5, and proinvestiruem 180 alrrady second phase-shifting block 7. Unit 8 also in the General case consists of n×2 summing chains. Constantly in the work involved only two of them are related to the corresponding phases. So, shifted by 120 alrrady signal phase "a" can communicate (stack) only signal phase "B", proinvestirovany 180 alcrudo, shifted by 24 alrrady signal phase "A" can only be summed with the signal phase "C", proinvestirovany 180 alrrady etc., according to the logic circuits and the principle of the proposed method. The choice of the pairs of chain block 8, or that the same module in which they are carried out control signals from unit 10, depending on the selected reference phase, the load which is minimal.

The logic of interaction between the above-mentioned blocks is as follows. If pre-installed, the balancing will occur relative to the least loaded phase, block 10 set as the reference to the least loaded phase. Suppose that the block 10 as the least loaded phase selected phase "A". In this case, the output of block 10 is formed by the combination of signals for ban modules 8.2 and 8.3. Thus, the work remains the only module 8.1, the output of which there are two signals, one of which is the sum of out of 120 alrrady signal of the reference phase "A" and proinvestirovanno 180 alrrady signal phase "B"and the second is a sum out of 240 alrrady signal of the reference phase "A" and proinvestirovanno 180 alrrady signal phase "C". Thus, on the output unit 8 generates signals proportional to the vector difference of the reference signal, the minimum loaded phase "A" and signal load simmetriyami phases "b" and "C". The data d is e a pair of vector difference of the currents and are formed by the signals used for balancing phase, the geometric sum which the load current of each of the respective phases and gives a current proportional to the current reference phase and the phase angle formed by the mentioned geometric sum of the current and the current reference phase, 120 alrrady. Thus, we get a completely symmetric system generated signal currents proportional to the currents simmetriyami three-phase system, a relatively minimally loaded phase "A". From the output of the unit 8 the generated control signals are received by the control circuit of the additional power source 9 through which are served in simmetriyami phase. As the latter can be used, for example, a system with dual energy conversion, including PWM - rectifier PWM inverter and containing an intermediate DC link. If the analysis of complexes loads determined that the balancing will occur relative to the phase current which is close to the average, in relation to the currents of the other phases, it is determined as a reference. The logic of the method of balancing, however, remains the same as in the case with the least loaded phase.

Thus, the sequence of actions performed in accordance with the claimed method is m, is balancing in the main n-phase network by means of an additional source of power, relative to a given phase. While improving the efficiency of balancing multi-phase system, when using the inventive method, is achieved by improved performance, ease of implementation, expanding the scope and increasing the efficiency in the process of balancing.

SOURCES of INFORMATION

1. AS the USSR №244495, bull. No. 18, 13.10.1969, CL H02J 3/26, 1969.

2. AS the USSR №562038, bull. No. 22, 14.07.1977, CL H02J 3/26, 1977.

The method of balancing the main n-phase network, loaded unsymmetrical n-phase load, which symmetrist the load currents of the individual phases, characterized in that the main n-phase network pre-set or phase with the load current, similar to the average, or the least loaded phase, determine the selected phase as a reference, emit it a signal proportional to the current it load, and with additional (n-1)-phase source of power is generated in each of the remaining (n-1) phase currents, pre-shaping them so that in each of simmetriyami (n-1) phases of the main n-phase network as a geometric sum of currents is generated in simmetrical phase current and its load would be equal to the current in the reference phase, and the angle formed by the sums of rim current, past and current simmetriyami phase, next support at direct alternation of phases, as well as between the total currents of the adjacent (n-1) simmetriyami phases, would be equal toalrrady.



 

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