SU901928A1 - Method of measuring active and reactive power - Google Patents

Description

one

The invention relates to a measurement technique and is intended for use in the measurement of active and reactive power in a network with asymmetric and nonlinear loads in the presence of zero and inverse sequences and higher harmonic components in the voltage.

A known method for measuring power, which consists in forming a measurement interval equal to the period of the main harmonic, during this period the voltage and current are converted by the input converters into a time interval and frequency, respectively. The converted voltage and current signals are multiplied together, resulting in a signal proportional to the current instantaneous power value. At the same time, two double frequency reference signals are formed, which are multiplied by the instantaneous power values, and the multiplication results are integrated over the measurement interval 111.

Its disadvantage is complexity.

There is also known a method for measuring active and reactive power, which means that the measurement of active and reactive power is performed on the main component of the current and voltage in a single and unchanging reference system, for which two orthogonal systems of three-phase sinusoidal reference signals of the current system frequency are formed. Using two orthogonal three-phase reference signal systems, the components of the main component are selected, by which the value of the main power flow C21 is determined.

The disadvantage of this method is complexity.

Claims (2)

The purpose of the invention is to simplify the method of measuring active and reactive power. The goal is achieved by the fact that in the method of measuring active and reactive power, based on the formation of a time interval equal in duration to the period of the main frequency of the monitored system, the components of the main component of the current and voltage determine the active and reactive power in this time interval. , they form signals by multiple integration of phase currents and voltages on the selected period, the values of these signals are measured at the end of the integration intervals, the signal, field chenny multiplicity of latest integrates Niemi, measured in the process of integration or the end of each interval znakoposto nstva symmetrical component B controlled forward sequence we ie. The essence of the method of measuring active and reactive power is as follows. 1. Form a time interval equal in duration to the period of the T-current of the main frequency of the monitored system. 2. Form a signal by integrating phase voltages UA (t), Ue, (t), Uc (t) and currents iA (t), ifc (t) and t. (T) in the interval 06, 4 (t) (t ) df, / t) t / y JA, B, C. 3- The magnitudes of the signals obtained by oflHOiKparHbiM by integrating voltages and currents at the end of period T result in the result that J}, j A, 8, C and (N), j A, B, C are obtained. 4. Signals are formed by double integration of phase voltages and currents in the same interval. i (t) ro // u (t) (dtf;% i (t) J) (,, B, C. 5. Measured values of signals at time t T, obtained by double integration, as a result of which they form & (T), j A, B C and GajXT) j A, B, C. 6. Generate a signal by threefold integration of phase voltages and currents on the inte (audio, vsjlt) JoJoXj (t) JoJoJo dtT 9 84 7. During the threefold integration, the values of the generated signals are measured at the end of the sign of the symmetry component of the direct sequence of the reference system, namely at time T / 2 for phase A, at times T / 3 and 5T / 6 for phase AT, at times T / b and 2T / 3 for phase C, as a result of which they receive, the values: (T / 2), 4b (T / 3) Vse, (5T / 6), Vac (T / 6). V4c (2T / 3); l (1/2), HT / 3). For & 5T / 6), L., e (T / 6), aac (2T / 3). 8, The signals obtained by threefold integration of phase voltages and currents at time T:), 35} (T), j A, B, C, 9 are measured. The measured values of c are summed. given weights, resulting in values that are proportional to the components of the voltage and current of the direct sequence, from which the active and reactive powers are calculated. For the considered example of three-time integration, the in-phase component of the voltage, as the sum of the measured values with given weights, has the form; MI E-Chs (t / b) W56 (V.) - VM (T / aV 1-VaeUT / s) - VAb (5T / 6) - L (T) | rzVaCr), V2c (T) J (T ) WbeCTj-VscCt). Expressions for the quadrature component of the voltage M / (have the same form, as well as the in-phase quadrature Ng components of the current, which are used to calculate the active 2 P I (, Ma) and reactive power Q 1 (- MaN). The measurement process in the proposed method It does not require for its implementation the generation of two orthogonal three-phase reference signal systems, as is required in the known method, and that is a complex technical task, taking into account the high demands on accuracy in shape and ase and the position of each of the system signals. The invention is a method of measuring active and reactive power, which consists in forming an interval of time equal to 5901928. over the duration of the period the main point in the process of integration is at the end of frequency of the controlled system, at each interval of sign In this time interval, a com- ponent component of the direct component of the main component of the current and a series of controlled voltage circuits are identified, which determine the 5 active and reactive power, about t and which is due to the fact that, with the price sources, I am simplifying, form signals that are multiply taken into account when examining with integral integration of phase currents-1. USSR author's certificate strains and voltages on a dedicated peri- no. 515E97, cl. G 01 R 21/06, 23, ode, measure the magnitude of these signals 2. Kuchumov L.A., Spiridonova L.V. at the end of the integration intervals. Some measurement and accounting problems and the signal obtained by the last electric energy. - Industrial multiples of integration, energy measurement, 1979, No. 1, p.